imaging in coronary artery disease

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Imaging in Coronary Artery Disease Author: Justin D Pearlman, MD, ME, PhD, FACC, MA; Chief Editor: Eugene C Lin, MD more...

Updated: Nov 13, 2012

Overview

Coro nary artery disease (CAD) is a complex disease that causes reduced or absent blood flow in one or more of the a rteries that encircle and supply the heart. The disease may be focal or diffuse. Apart from ra re congenitalanom alies (birth defects), CAD is usually a degenerative disease, uncommon as a clinical proble m before the ageof 30 years and common by the age of 60 years. One in four people will have a heart attack. The first recognizedsym ptom may be death. The term coronary is derived from crown, referring to the way these arte ries sit on theheart .

See the images below depicting the coronary arteries and CAD.

Selective injection image of the left coronary arteries. D1 = first diagonal, LAD = left anterior descending artery, LCX = left circumflex, LM= left main coronary artery, and OM1= first obtuse marginal.

Contr ast-la beled blood to the heart is used to identify the territory at risk. The results of this assessment of the delayed arrival comparesfavorably to the f indings of radionuclide stress imaging, and stress induction of ischemia is not required to identify the zone at risk.

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Compared w ith radionuclide images of blood delivery, MRIs and CT scans improve resolution, depiction of the functional effect and therelationship to the coronary supply, and identification of the area at risk w ithout stress. The advantage of radionuclide imaging is primarilyits predictive value; stress echocardiography has similar predictive value. MRI and CT have been less available than other studies;therefore, data on their value are relatively limited.

Stable and unstable lesions

Lesions that cause blockages in the coronary arteries may be stable or unstable. Unstable lesions activate bloodclotting and/or vascular spasm. Indications that CAD may be unstable include recent onset or familiar symptomsthat are increasing in frequency, in duration, or in severity or with decreasing exertion tolerance or at rest. Theterm "chest pain" is a code phrase the symptoms of CAD do not have to be in the chest and do not have toinclude pain. I prefer the phrase "heart warning" symptoms. When a warning light is activated, you should resolvethe problem quickly even if it is low in intensity.

Unstable symptoms of CAD may represent a threatened heart attack. After as little as 5 minutes, a wall of theheart may stop functioning but still be salvageable that is called stun. After as little as 10-20 minutespermanent damage may accumulate, summarized by the phrase "time is muscle." If the symptoms are new or if they are familiar but unstable or are not reliably fully resolved in 5 minutes, emergency help is recommendedbecause "time is muscle." Intervention completed within 60 minutes improves outcome. The symptoms of athreatened heart attack may be very mild.

Ischemia

When the heart has inadequate blood supply (ie, ischemia), pressure may be felt in the chest that moves to theleft arm; one may feel weak, sweaty, or short of breath or nauseated; palpitations (ie, change in heart rhythm) mayoccur; or there may be a sensation of pressure or tightness just in the chest, neck, or arms.

Many patients mistake the heart warning symptoms for heartburn or gas. If symptoms occur that may representinadequate blood supply to the heart, one should rest immediately and take nitroglycerin, if available. If symptomslast more than 5 minutes, occur at rest, or keep coming back, one should call 911, chew a full-sized aspirin (325mg) if not allergic, and continue taking nitroglycerin every 5 minutes as long as it does not cause dizziness or light-headedness.

For excellent patient education resources, see eMedicineHealth's Cholesterol Center . Also, visiteMedicineHealth's patient education articles Chest Pain , Coronary Heart Disease , and Heart Attack .

Severity of CAD

The severity of CAD is defined several ways, including the following:

Anatomically , by visualiz ing the blood vessel branches and any blockages to blood flow along the pathwaysFunctionally, by estimating blood delivery to tissue supplied by each branch vesselClinically, by determining what symptoms correspond to inadequate blood delivery, what level of activitycauses them, what relieves them, and the pattern of occurrences

Such patterns are described as unstable if the pattern includes variable or accelerating frequency, variable or increasing severity or changing character of symptoms, or variable or decreasing exercise threshold or if symptoms continue or recur just after a heart attack.

In addition, one examines the consequences, including the location and extent of reversible and of permanentimpairment, motion and thickening of affected segments of the heart, and whether the damage is causing or sustaining life-threatening arrhythmias.
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One also evaluates the patient's overall cardiac performance, which is typically expressed as the ejection fraction(EF), or percentage of the contents the left ventricle pumps forward in a heartbeat, and exertion tolerance, graded1-4 (1=normal, 4=bedridden).

The TIMI (Thrombolysis in Myocardial Infarction) risk score looks at 7 factors that point to bad outcomes:

1. Age 65 years or older 2. At least 3 risk factors for coronary artery disease3. Prior coronary stenosis of 50% or more

4. ST-segment deviation on electrocardiogram at presentation greater than 0.5 mm5. At least 2 anginal events in prior 24 hours6. Use of aspirin in prior 7 days7. Elevated serum cardiac markers

TIMI risk scores have the following risk of all-cause mortality , new or recurrent MI, or severe recurrent ischemiarequiring urgent revascularization within the first 2 weeks: 1=5%, 2=8%, 3=13%, 4=20%, 5=26%, 6/7=41%. [1]

Imaging of CAD

At present, achieving the best resolution on images of the coronary arteries requires catheterization, injection of aniodinated contrast agent, and use of a radiographic technique. As an alternative, multidetector-row CT (MDCT) or

MRI may be used to clarify coronary anatomy and to determine whether a vessel is occluded.

Stress imaging has a complementary role in depicting zones with inducible ischemia (blood supply inadequate for the demands of the tissue). Stress may be produced with exercise, an infusion of a medication that increases thestrength of cardiac contractions (eg, dobutamine), or an infusion of a medication (eg, adenosine, dipyridamole) thatdilates the vessels and thereby reduces the delivery of blood to diseased branches.

More than a decade ago, MRI was shown to be capable of imaging the coronary arteries and demonstratingstenoses without catheterization or injection of contrast material. [2] MDCT is now proving to be a fast and usefulalternative for defining the coronary anatomy. [3] MRI takes more time than MDCT and generally provides less detailof the coronary anatomy, but it avoids ionizing radiation and the use of iodinated contrast agent.

Advances in MRI and CT have markedly improved the speed and resolution of imaging, making these modalitiesuseful in the clinical evaluation of CAD while improving their safety and convenience. In addition to defining theanatomy, both MRI and CT can be used to identify zones of impaired blood supply by timing of the arrival of contrast agentlabeled blood.

In addition, MRI is useful in identifying the location and thickness of myocardial scars. Although neither MRI nor CT has replaced x-ray angiography (XRA) as the clinical standard for the diagnosis of coronary stenosis, their usein determining if a vessel is open is increasing. Recently, 64-slice multidetector-row CT angiography (CTA) hasshown potential as an alternative to x-ray angiography for the identification of coronary blockages. [4] In a study of 15,207 intermediate likelihood patients without known CAD, the severity of CAD on coronary CTA was predictive of the need for invasive coronary artery catheterization or revascularization. This suggests that coronary CTA may bean effective gatekeeper for invasive catheterization. [5]

Assessment of tissue viability

The amount of impairment or damage caused by stenosis obstructing a coronary artery depends on how much of the myocardium the vessel supplies, the severity of the stenosis and any superimposed spasm, the level of demand in the tissue it supplies, and the condition of the tissue it supplies.

When demand exceeds supply, the tissue becomes ischemic, which means blood supply is insufficient tomaintain normal metabolism. Myocardial ischemia may cause chest pain, fatigue, shortness of breath, or another form of reduced exertion tolerance.

Ischemia may have no symptoms but may be detected as impaired blood delivery, impaired contractile function(wall motion or wall-thickening abnormality on dynamic cardiac imaging series), or interference with the movementof ions (resulting in depolarization and repolarization abnormalities on EKGs as ST-segment shifts, changes in STand T waves, and/or rhythm abnormalities); and/or it may be detected when a blood test shows a release of enzymes (creatine kinase-MB [CK-MB], troponin-I, troponin-T) from the heart muscle.

Ischemia may deplete high-energy phosphate carriers (eg, c reatine, adenosine) that are needed for muscle


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contraction. Depletion may occur to the point that impaired motion may persist even when ischemia is relieved.Transiently impaired contractile function of muscle that persists after the relief from ischemia is called stun , andlong-term dysfunction of viable muscle is called hibernation .

Dead tissue converted to scar likewise loses contractile function. Therefore, a key issue when a region of heartwall shows loss of function is the determination of whether the myocardium is still viable. Persistent wall-motionabnormality at rest shown by imaging (echocardiography, MRI, CT, x-ray angiography) can raise the issue of tissue viability and, in particular, whether repairing a blockage in the blood supply is likely to be beneficial.

If a region is thin and akinetic (no motion), it is more likely to scar (dead myocardium) than if it is not. However,when in doubt, viability tests are appropriate. For example, viability can be identified by performing phosphorus-31MRI and by reporting for each region the relative concentrations of creatine phosphate; inorganic phosphate; andadenosine monophosphate, diphosphate, and triphosphate.

Although MRI of phosphorylated metabolites and positron emission tomography (PET) of metabolic activity (toassess glucose utilization) can be used to assess tissue viability, an alternative method of equal, if not better,clinical value is imaging by MRI with contrast to identify contrast retention by damaged myocardium. We firstobserved that phenomenon over a decade ago when studying an animal model of ischemia and infarction whilelooking at angiogenesis (treatments to promote development of the blood supply).

Another way to identify viability is to examine wall motion at rest and with light stress. Dobutamine stress imaging

may be performed with MRI or echocardiography. Dobutamine stress tests are used to detect viability bydemonstrating dose-related increases in contractility if the tissue is viable. An increase in the dose of dobutaminemay subsequently elicit a decline in contractility associated with induced ischemiathat is, a biphasic response,indicating viable but threatened myocardium.

Early in the development of perfusion imaging [6, 7] , we observed retention of gadolinium contrast by injuredmyocardium. Normally, a bolus of contrast agent washes out of the heart walls within 5-10 minutes. Any contrastagent seen in the heart after the agent has washed out of normal zones demarcates injured myocardium.

This technique has since been called MRI scar mapping or delayed enhancement imaging. The fraction of wallthickness that retains gadolinium-based contrast agent 10-20 minutes after a bolus infusion of 20 mL/75 kgindicates viability. The result is an excellent predictor of potential for functional recovery. If the scar is less than

one third the thickness of the wall, improvement with revascularization is likely. However, if the scar is more thantwo thirds the thickness of the wall, improvement after revascularization is unlikely.

MRI scar maps depict contrast retention due to cell disruption. Although acute injury results in slightly enlargedzones of retained contrast agent on MRI, after a week, the defined zone appears the same months to years later and it corresponds on pathology to dead tissue.

Unfortunately, in patients with poor renal function, gadolinium contrast may stay in the body long enough to causea potentially disabling inflammatory reaction called nephrogenic systemic sclerosis, also known as nephrogenicfibrosing dermopathy (NSF/NFD).

NSF/NFD has been linked to all the gadolinium-based contrast agents (gadopentetate dimeglumine [Magnevist],gadobenate dimeglumine [MultiHance], gadodiamide [Omniscan], gadoversetamide [OptiMARK], gadoteridol[ProHance]). For more information, see the Medscape Reference topic Nephrogenic Fibrosing Dermopathy. Thedisease has occurred in patients with moderate to end-stage renal disease after being given a gadolinium-basedcontrast agent to enhance MRI or MRA scans.

NSF/NFD is a debilitating and sometimes fatal disease. Characteristics include red or dark patches on the skin;burning, itching, swelling, hardening, and tightening of the skin; yellow spots on the whites of the eyes; jointstiffness with trouble moving or straightening the arms, hands, legs, or feet; pain deep in the hip bones or ribs; andmuscle weakness. For more information, see FDA Information on Gadolinium-Based Contrast Agents or Medscape . Patients with poor renal function undergoing dialysis have been imaged with coordinated extra dialysisruns to clear the agent.

Appropriate and timely treatment

When symptoms suggestive of a possible threatened heart attack are present (persisting chest pain or pressureradiating to 1 or both arms or jaw; or unexplained shortness of breath, weakness, sudden sweating, or a seriousarrhythmia), an electrocardiogram should be obtained promptly, with continual monitoring for arrhythmia or ischemia (impaired blood supply).
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Ambulances have both EKG and rhythm and oxygenation monitoring equipment, as do emergency departments.The EKG can show ST segment shifts and/or T-wave inversions as signs of heart ischemia or injury. However,there are electrically silent areas in the standard monitors. A 12-lead EKG does not detect all of the electricalwarning signs of heart damage; more extensive thoracic coverage is desirable.

Preferred examination

If a patient has symptoms, suggestive EKG findings, or imaging results that indicate a need for intervention, x-rayangiography by means of catheterization is currently the preferred examination for identifying the culprit lesionsand, often, for providing an interventional remedy during a single session.

The patient's clinical history (age, symptoms, risk factors) provides an estimate of disease likelihood. The basicscreening test is stress EKG, which can adjust prognosis depending on the pretest likelihood of disease.

Generally, if the patient has no symptoms and the resting and stress EKGs are normal, the risk of mortality in thenext year is low. However, the predictive accuracy of EKG even at peak stress as part of stress testing overall isnot good, with as much as one half of all cases of disease missed by EKG. The simple addition of stress testingof B-type natriuretic peptide (BNP) levels in the blood markedly improves the predict ive accuracy. [8] Other ways toimprove accuracy are nuclear imaging, echocardiography, MRI, or CT.

Stress nuclear imaging is widely used to assess the patient's exercise tolerance and to identify zones of inducible

ischemia (jeopardized myocardium), which is useful information, even after x-ray angiography is performed. PEToffers similar rest-stress data and is superior for identifying viable myocardium. Jeopardy and viability are importantissues, because if the myocardium is not at risk or if it is not viable, revascularization (bypass or angioplasty) willnot help that part of the heart.

Echocardiography to identify wall motion abnormalities has a similar predictive accuracy in patients withintermediate suspicion of CAD, estimated at 80-90%. Echocardiography avoids radiation exposure, which maycause as much as 1 new cancer for every thousand patients studied, but radionuclide imaging (thallium,sestamibi) is preferred if the patient already has old wall motion abnormalities or has poor echo windows (lungblocks the views).

Exercise stress echo may be performed before and after treadmill exercise or during exercise on a supine bicycle.

The latter requires more cooperation but allows imaging at every stage, so it may avoid false negatives from rapidrecovery or from involvement of all areas (balanced ischemia).

MRI and CT have markedly improved the ability to depict zones of impaired blood supply and to display thecoronary anatomy. MRI and CT do not require stress; they offer sensitivity and specificity similar to those of nuclear imaging; they achieve resolution better than that of nuclear imaging; and they can demonstrate the 3-dimensional (3D) coronary anatomy. [9] Therefore, MRI and CT complement the combination of stress test andcatheterization, and in some settings, MRI and/or CT may replace them (eg, by demonstrating normal results).

EBT offers similar value. EBT is a form of CT in which an electron beam, rather than the entire x-ray source, isrotated around the patient. Also, EBT and CT have been used as a screening test to screen for calcifications in thecoronary arteries as a marker for risk of coronary disease in young patients.

To monitor angiogenesis, collateral-sensitive and delayed-arrival MRI appear to be far more sensitive than anyother technique. Collateral-sensitive MRI generates a dark flare of susceptibility effect due to sparse neovascular development at an early stage while suppressing a similar effect from the LV. This finding is a strong predictor ( r =0.93) of improved blood delivery.

Data from quantitative studies of the extent of delayed arrival in humans and from double-blind postmortemevaluations in porcine models of chronic myocardial ischemia and angiogenesis have validated this method. [6] Thisfinding clearly distinguishes angiogenic treatment from control at 4 weeks after treatment, and the benefit isfollowed by improvements in wall motion (serial motion assessment by reference tracking [SMART]measurements). [10]

Limitations of techniques

X-ray angiography is considered the criterion standard for evaluating coronary artery stenosis. Flow limitations maybe estimated by using the TIMI (Thrombolysis in Myocardial Infarction)score and confirmed by using a flow wire or by performing IVUS. [11] If x-ray angiography fails to depict a culprit lesion and if cardiac ischemia is inducible, the


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patient may have syndrome X (microvascular disease).

X-ray angiography requires the use of iodine, which may cause serious allergic reactions, including anaphylaxisand also renal failure. Use of large volumes of saline and the antioxidant acetylcysteine may help prevent renalfailure. The catheterization procedure can induce vessel spasm and/or tear the lining of a vessel, resulting inocclusion and, possibly, death in a patient who may not have had coronary artery disease (CAD). The procedurecan also result in embolism, which may cause stroke or limb loss. Nerve damage, infection, and other complications are possible as well. The death rate is approximately 0.1%.

Nuclear imaging produces low-resolution images that may depict an apparent defect resulting from breast tissue,hiccups, paradoxical septal motion, or other confounding factors. Nuclear imaging may fail to depict diseasebecause of submaximal stress. Tomographic imaging, attenuation correction, or PET substantively eliminate theproblems resulting from breast attenuation. The newer combinations of nuclear imaging with CT enable the mostaccurate correction of nuclear event maps for attenuation by overlying tissues.

MRI requires special precautions in patients with pacemakers or recently placed aneurysm clip. Patients withclaust rophobia require premedication, mirrors, and/or an open magnet. Many magnets do not accommodatepatients who weigh more than 300 lb. Arrhythmias commonly lower image quality.

CT contrast agents usually contain iodine, which may cause an allergic reaction and possibly anaphylaxis.Nonionic contrast material reduces the risk of harm, as does pretreatment with steroids. Gadopentetate

dimeglumine, the contrast agent used for MRI, may be used for CT if patients are allergic to iodine-based media.CT uses X-rays typically equivalent to the dose needed for about 200 chest radiographs. A single routine CT studyin a child increases the lifetime risk of cancer by 0.35% per scan. [12] In adults, the lifetime risk of cancer may beas high as 2% with annual CT screening. Because the breast has high radiosensitivity, techniques to reducetissue exposure, such as displacing the breasts outside the direct x-ray beam and using a lead shield, can reduceradiation hazard of CTA. [13]

Imaging guidance of interventional procedures

X-ray angiography is widely used to guide interventions, such as balloon angioplasty, atherectomy, laser treatment, stent placement, and other procedures. Current practice indicates the use of x-ray angiography in

patients with potentially treatable lesions to confirm the findings and to perform interventions. Both tasks may beaccomplished in a single procedure.

Cardiac catheterization is recommended for patients with mild angina (class I or II) plus an EF of less than 45%,including patients with noninvasive test results indicating a high risk, those with an uncertain diagnosis after noninvasive testing, patients with serious ventricular arrhythmias, and those who survive an episode of suddendeath. The only indication with submaximal support is mild angina with reduced EF; this is a class IIarecommendation. The classification of indications by the American College of Cardiology indicates the weight of evidence in support of the recommendation. Mild angina with no reduction in EF might be managed withmedication as a therapeutic trial.

As an experiment, MRI, CT, or echocardiography may be used to guide interventional procedures. MRI does not

involve ionizing radiation; therefore, imaging may be active throughout the procedure. However, special guidewiresand other equipment compatible with the magnet and the rapidly changing magnetic field must be used, and staff must be trained to ensure that no magnetic objects are brought near the magnet.

CT uses ionizing radiation and is slower than x-ray angiography, but it provides 3D information that may facilitatelocalization, especially for newer interventions such as the intramyocardial injection of angiogenic growth factors or stem cells. 3D ultrasonography similarly facilitates accurate injections, with convenience of portability and withouta need for lead shielding from x-rays.

Radiography

Coronary angiography shows where vessels originate, how they branch, whether they have obstructions or dissections or thrombi, the degree of any obstructions, and which territories they supply. See the x-ray angiographbelow.
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X-ray angiography is the criterion standard for delineating the coronary anatomy, but it is inferior to MRI and CT in identifying myocardiumw ith impaired blood delivery, in assess ing the functional consequences, and in identify ing the development of microvascular collaterals.

Some key questions answered during an examination of the anatomy include the following:

Does a coronary artery pass between the aorta and pulmonary artery where it may get pinched?Does a segment tunnel under a myocardial bridge?Which pathway supplies the posterior surface? Is it the right, left circumflex, or both? That is, is it rightdominant, left dominant, or cdominant?Does the LAD wrap around the apex to supply the distal diaphragmatic surface?What vessel supplies the AV node? Is its blood supply impaired?If an infarct is present, which is the infarct-related artery?If abnormal wall motion is seen, which branch obstruction accounts for it?

Are any bypass-graft vessels present? If so, where do they originate (left internal mammary, saphenousvein graft from anterior aortic root)? Are they long or short, where do they connect, and how (end to side,

side to side)?

The caliber of vessels may be estimated by comparing them with the known diameter of the catheter if it appearson the image. The reviewer should take into account the fact that magnifications differ at different distances fromthe source to the intensifier with x-ray projection angiography.

After describing the anatomy, note the location, percent narrowing, and character of all focal obstructions(stenoses).

For each lesion, is it concentric (symmetric) or eccentric (1 sided)?Is it long or short?Does it abut a branch vessel (which may be lost after intervention)?Is it calcified?Is any thrombus demonstrated?Is evidence of intimal tear demonstrated?Is evidence of vessel spasm demonstrated?Is diffuse narrowing demonstrated?

The flow of contrast agentlabeled blood offers useful information. TIMI criteria may be applied to determinewhether the distribution of contrast material is TIMI 0 (incomplete, fails to fill branches and distal part of thevessel), TIMI 1 (slow but complete), or TIMI 2 (brisk and complete). When imaging is performed at a rate of 30frames per second, the number of frames it takes for a vessel to completely fill may be assessed. The normalnumber is approximately 21 frames. Filling takes longer in patients with disease than in healthy people, not only inthe diseased vessel but also in normal vessels.

Consider how findings may affect possible interventions and report them accordingly. Clinically significantnarrowing in the left main coronary artery is a medical emergency because of the amount of myocardium at risk.Other patterns of disease can pose similar risk; examples are proximal disease in both the LAD and a dominantright or left circumflex vessel.

What is the caliber of distal vessels that may support a bypass graft? Are they calcified?Is any stenosis near a branch point (such that balloon angioplasty of the lesion may obstruct a branchartery)?How long is the left main coronary artery?How much myocardium is at risk?

Examine images for ancillary findings.

Which calcifications move with the heart?Is the mitral valve annulus calcified?Is the aortic root or the aortic valve calcified?
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Are valve rings, bypass vessel rings or clips, stents , s ternal wires, or other evidence of prior surgeriesnoted?If pacer wires are noted, where do they end?Does evidence exis t of chamber enlargement, aneurysm, cardiac displacement, abnormal pulmonaryvenous return, unusual persistence of fetal structures, or other variants?

If left ventriculography is performed, examine LV function for the EF, regional wall-motion abnormalities, and valveintegrity. Hypokinesis indicates educed motion, akinesis indicates no motion, and dyskinesis indicates reversedmotion, such as ballooning outward during systole. Note any leakage of contrast material back into the left atrium

and any restriction of the valve leaflets.

At the time of coronary angiography, the same set of tools can be used to examine other vessels (eg, renal andcarotid arteries). [14]

Degree of confidence

X-ray angiography (XRA) is the standard for identifying the coronary anatomy and stenoses. In select cases,alternative imaging may appear superior, but be careful to distinguish between high-quality or good-looking picturesand the reliability of the results. X-ray angiography may provide a false-negative result if a branch vessel isoccluded at its origin, if the disease is asymmetrical, or if the lesion is cracked, such that the contrast agent canextend close to the full diameter of the vessel even though the vessel cross-sectional area is severely reduced (eg,a star-shaped lesion).

It is possible to miss a lesion that is hidden behind another vessel, but that problem is generally resolved byangled views and by moving the camera (panning) during image collection. If the significance of an obstruction isunclear by XRA, intravascular ultrasound (IVUS) or a flow wire may be used to clarify its spatial extent in relationto the vessel lumen or its impact on flow down a particular branch vessel. A vasodilator may be delivered toassess flow reserve. X-ray angiography is not a good detector of small vessel disease, epitomized by cardiacsyndrome-X.

Stress EKG predictive accuracy can be as low as 50%, but it rises above 75% if combined with proBNP bloodtesting. [8] Stress imaging accuracy for detection of coronary artery disease (CAD) ranges from 70-90% if the targetstress level is achieved while off antianginal medications.

Treadmill or bicycle stress testing is generally preferred, followed by dobutamine stress testing, then adenosinecombined with low level exercise. Adenosine or dipyridamole alone is less reliable. Chest pain during adipyridamole stress test is not uncommon in the absence of CAD. [15] Target heart rate (peak HR) for exercise or dobutamine stress testing is 85% of the age-predicted maximum (85% of peak systolic BP peak HR). Animalstudies have shown that the rate-pressure product is a better predictor of the stress levels that should inducedetectible ischemia. A 50% blockage should be detected with more than 50% confidence above a rate-pressureproduct of 20 kilotorr/min and with more than 85% confidence above 25 kilotorr/min.

Limitations

Balloon angioplasty can disrupt an obstruction so that the vessel appears to recover its full diameter when, in fact,the cross-sectional area is improved only minimally and insufficiently. 3D imaging can be used to examinecontrast-agent attenuation and the percentage narrowing. On occasion, this condition may be identified by lookingat the lesion on different views or by performing IVUS or optical CT.

The introduction of a catheter or a wire can cause intimal dissection (a tear in the lining of a vessel), which may bemistaken for vascular spasm, thrombosis, or a long stenosis on cursory examination. A tissue flap in theendothelial lining may alternate between an open position and an obstructive one, mimicking a spasm; however, itis not responsive to nitrates. The distinction may be a matter of life or death. If clinically significant, stentplacement, bypass, placement of a perfusion catheter, or other emergency treatment is typically required to treata dissection. Sudden obstruction due to a dissection can be deadly, and it does not respond to medications.

Myocardial bridges, or small bands of muscle overlying a vessel, may be mistaken for stenoses; however, theseare not amenable to angioplasty. The obstruction from a myocardial bridge is smooth and eccentric. Observationthroughout the cardiac cycle shows that the obstruction occurs during systole.

Computed Tomography


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CT imaging of the coronary arteries is achievable with fast CT and EBT systems triggered or gated by ECG toaccumulate data when the heart is in diastole. 64-section multidetector-row CT is the newest technology. [16, 17, 18,19]

With a section thickness of 1 or 0.5 mm or less, the coronary anatomy is laid out in a 3D volume. Imageprocessing can greatly facilitate visualization of the course of vessels and branches and the presence and degreeof stenoses. The coronary-artery tree may be viewed as a solid rendering of the surface of the heart, but portionsmay be obstructed from view.

Proper viewing of each coronary-artery branch should include clean views in which the LV blood pool, aortic root,and all extracardiac structures are removed, and vascular projections are limited to the zones that include thevessel of interest and a margin for partial-volume effects.

Do not rely on threshold-based renderings, which can cause false-stenosis and false-obstruction and which cancause an intravascular thrombus to be missed. The use of a pair of volumes before and after the administration of contrast material for elastic matching [20] greatly facilitates the evaluation by automatically isolating the coronarytree without thresholding. [9]

CT also enables superb evaluation of blood delivery. In principle, CT combined with catheterization permitsaccurate definition of the extent of collateral-dependent myocardium. [9] (See the CT image below.)

Elastic-match imaging automatically identifies diff erences betw een image volumes. The acquisition of 1 set of contrast-enhanced chestCT images via the coronaries and a nonenhanced set provides a 3-dimensional view of the coronary-artery tree. The nonenhancedvolume data w ere rendered as holographic projections to provide the anatomic context, and the elastic-match coronary tree w asoverlaid. In addition to automation, this method avoids thresholding so that small branches and filling defects, if present, are representedproperly.

Pizzuto et al found that transthoracic Doppler echocardiography can improve the diagnostic accuracy of multidetector computed tomography (MDCT) for detecting left anterior descending (LAD) coronary artery stenosis.In 144 consecutive patients, coronary anatomy was assessed with MDCT, and echocardiography was used tocalculate coronary flow reserve (CFR), by measuring the ratio of hyperemic to baseline peak flow velocity ; resultsof both methods were verified with invasive coronary angiography. [21]

In a univariate model, the prediction of significant LAD stenosis was slightly, but significantly, better with coronaryflow reserve (sensitivity 90%, specificity 96%, positive predictive value 84%, negative predictive value 97%,diagnostic accuracy 94%) than with MDCT (sensitivity 80%, specificity 93%, positive predictive value 71%,negative predictive value 95%, diagnostic accuracy 90%). [21]

When the findings from transthoracic Doppler echocardiography and MDCT agreed, the diagnostic accuracyincreased (96%). In the 13 patients missed by MDCT, transthoracic Doppler echocardiography proved 100%accurate at predicting significant LAD stenosis. [21]


The ability of MRI and CT to depict the anatomy and the absence of notable obstructions is improving rapidly, but

it is not uniform. The value of MRI and CT must be assessed in a truly double-blind fashion for each center untilstandardized, reliable methods are widely established.

Whether MRI and CT results match in terms of the percentage of stenosis is relatively unimportant. Mostimportant is whether MRI and CT reliably depict normal tissue and culprit lesions and, then, whether they establishthe severity and the territories supplied by the culprit vessel. Both MRI and CT offer the significant advantage of
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direct assessment of the zones of impaired blood delivery.

Limitations

MRI shows calcifications as black or signal voids, whereas CT shows calcifications as white and similar tocontrast-filled blood. These appearances can influence the estimation of stenoses.

Heavy calcification causes a beam-hardening artifact on CT that can interfere with visualization. Stents cause alocal disturbance stronger on MRI than on CT. Also, with 3D MRI or CT, be certain to understand how the images

account for local curvature in and out of the imaging planes. In finding the best plane to show a vessel, radiologistscan mistake a local curve that is out of plane for an apparent stenosis. Proper image processing resolves thisproblem.

Magnetic Resonance Imaging

Coronary MRI has improved from the early methods [2] and equipment sufficient to identify normal proximalcoronary arteries and courses, but it is not a c linical replacement for XRA apart from ruling out aberrant coronaryorigins, demonstrating graft or native vessel patency, or follow-up on specific lesions.

Coronary MRI may be performed by using a 3D volume, but the trade-off in time and resolution favors imaging in

selective planes that address each branch of interest. As a 3D volume, MRIs may show the coronary tree in a waysimilar to the methods described for CT. Background tissue may be suppressed with fat saturation, tissuesaturation, magnetization transfer, and/or T2 preparation (90-180-180- ... -180-90). [22]

The vessel-plane approach is as follows: Any desired target plane can be obtained by specifying 3 points toinclude in the plane, by drawing the lines of intersection with 2 previous images at different angles, or (commonly)by drawing a single line of intersect ion with a previous image that is perpendicular to the desired view. For example, to obtain a short-axis view of the coronary sinus, first obtain a long-axis view of the LV parallel to theseptum and perpendicular to the AV groove, then prescribe a plane in the AV groove perpendicular to that viewpassing through the 2 observed points of intersection on the first view with the coronary sinus, seen as bright dotsanterior and posterior to the mitral valve.

Other points regarding MRI to evaluate CAD are the following: A transverse stack of images covering the aortic root depicts the origin of the RCA and the left maincoronary artery. The typical section thickness should be 3 mm or less. A bright- or dark-blood techniquecan be applied with the use of single frames or with a dynamic movie series.

An additional distal transverse image shows a cross-section of the RCA, LAD, and LCX.From 2 points along the proximal vessel and from 1 point from the distal vessel, a plane that captures thedesired segment is selected. The plane may be adjusted to be thick enough to encompass out-of-planebends. As an alternative, it may be subdivided into a stack of thin imaging planes for a localized 3D stackof images.The course of the RCA in the AV groove can quickly be ascertained from a 4-chamber long-axis view of theheart by obtaining 1 preliminary image perpendicular to the AV groove and parallel to the septum through

the mid RV. This provides 2 points of intersection with the RCA: 1 anterior and 1 posterior in the AV groove.Prescribing a plane through those 2 points from the long axis image gives the desired view.The posterior descending artery requires a different imaging plane, as do the LAD, LCX, and major branches. The course of the LCX in the AV groove is assessed in a way similar to that used for imaging theRCA, by acquiring a scout image parallel to the septum to identify 2 points to include in one final short-axisimage. However, in this case, the scout image should be laterally displaced to the outer third, because thedistal LCX is often hard to identify.The authors routinely identify the proximal course of the coronary arteries in young patients who have hadsyncope to look for aberrant origins. A complete absence of abnormalities suggests a good prognosis.MRI with contrast is an excellent method to identify myocardial scar (infarction) as small as 1% of themyocardium, which is a very strong prognostic factor [23] , while also assessing perfusion and precisefunction of left and right ventricles. It can also be combined with stress testing and coronary imaging for a"one stop shop."MRI is the preferred test for right ventricular injury or infarction.

Apparent s tenosis must be distinguished from an out-of-plane bend. A signal void from flow disturbance may exaggerate apparent stenosis .MRI is well established as a means to assess the patency of a bypass graft.


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MRI offers high sensitivity to changes in wall function, eg, wall thickening and radial motion. [10] MRI may be usefulin identifying and quantifying impaired blood delivery and wall function in response to interventions. [6, 24, 25, 26, 27,28, 29, 30] Such applications are perhaps more vital than visualizing the percentage of stenosis .

Confidence in the data depends on the speed and quality of the imaging method, the cooperation of the patient(shallow regular breathing or several matching breath holds), the accuracy of EKG triggering or gating, and theanatomic knowledge and judgment of the person directly supervising data collection.

Usual EKG signal in MRI is markedly distorted by competing signals from movement in a magnetic field and bymoving magnetic fields, particularly from blood flow in the great vessels , called the magnetohydrodynamic effect.That distortion makes it difficult to perform electrographic safety monitoring for ischemic changes.

Cardiac MRI with the vessel-chasing approach requires highly informed decision making as the data are beingacquired. If the operator acquiring the data understands what the x-ray angiogram demonstrates, the views may bemanipulated for the best match. This consideration is not necessarily positive, because the operator mayexaggerate the agreement.

The ability of MRI and CT to identify anatomy and the absence of clinically significant obstructions is improvingrapidly, but it is not uniform. The value of MRI and CT must be assessed in a truly double-blind fashion for each

center until standardized and reliable methods are widely established.

Whether MRI and CT results match in terms of the percentage of stenosis is relatively unimportant. Mostimportant is whether MRI and CT reliably depict normal tissue and culprit lesions and, then, whether they help inestablishing their severity and in depicting the territories supplied by the culprit vessel. Both MRI and CT offer thenotable advantage of enabling direct assessment of the zones with impaired blood delivery.

Limitations

In an apparent stenosis, be certain that it is not a partial-volume artifact or a velocity-shear effect. Because localdifferences in velocity can cause a signal void, estimates of stenosis may be exaggerated.

Magnetic susceptibility artifacts may produce signal voids. Stents, clips, and wires cause local disturbances.

The presence of pacemaker wire is considered a relative contraindication to MRI because the rapidly changingmagnetic fields may induce a voltage that can trigger an arrhythmia, induce a burn, or shorten the battery life.

Also, when the patient enters and leaves the magnet, the magnetic reed switch on most pacemakers will switch itto fixed mode, and the temperature may rise in metal devices. For example, a pacemaker generator may warm by1-2C. However, with informed consent, careful pulse monitoring, and a readiness to promptly abort a pulsesequence if an arrhythmia is induced, patients with pacers have undergone MRI with no apparent consequenceand no change in their pacer thresholds. In the dozen reports of mishaps related to pacemakers and MRI, nonewere caused by MRI.

On MRIs, calcification is depicted as a black area or signal void, whereas CT shows calcifications as white, similar to blood filled with contrast agent. These appearances can influence the estimation of stenoses. Also, with 3D MRIor CT, be certain to understand how the images account for local curvature in and out of the imaging planes. Infinding a best MRI plane for showing a vessel, radiologists can mistake a local curve that is out of plane for anapparent stenosis. Proper image processing resolves this problem.

With MRI, flow disturbances that cause velocity shear (range of phases in each picture element or pixel resultingfrom different rates of motion of blood) cause a local decrease in signal intensity, which may create or exaggeratean apparent stenosis.

Ultrasonography

Echocardiography can be used to identify the left main coronary artery. In some patients, much of the RCA andLAD can be viewed; however, in most patients, the imaging window is inadequate for useful coronary imaging fromoutside the chest.

In the catheterization laboratory, IVUS may be performed to examine the coronary arteries from the inside and tocharacterize plaque. However, the diameter of the device limits the ability to pass through tight stenoses. Also, the
http://emedicine.medscape.com/article/1971142-overview


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injection of a sonographic contrast agent (eg, agitated Renografin) into the coronary arteries, combined withtransthoracic or esophageal ultrasonography, can be useful in identifying perfusion territories.

Pizzuto et al found that transthoracic Doppler echocardiography can improve the diagnostic accuracy of multidetector computed tomography (MDCT) for detecting left anterior descending (LAD) coronary artery stenosis.In 144 consecutive patients, coronary anatomy was assessed with MDCT, and echocardiography was used tocalculate coronary flow reserve (CFR), by measuring the ratio of hyperemic to baseline peak flow velocity ; resultsof both methods were verified with invasive coronary angiography.

In a univariate model, the prediction of significant LAD stenosis was slightly, but significantly, better with coronaryflow reserve (sensitivity 90%, specificity 96%, positive predictive value 84%, negative predictive value 97%,diagnostic accuracy 94%) than with MDCT (sensitivity 80%, specificity 93%, positive predictive value 71%,negative predictive value 95%, diagnostic accuracy 90%). When the findings from transthoracic Doppler echocardiography and MDCT agreed, the diagnostic accuracy increased (96%). In the 13 patients missed byMDCT, transthoracic Doppler echocardiography proved 100% accurate at predicting s ignificant LAD stenosis. [21]

Nuclear Imaging

Nuclear medicine study does not depict the coronary arteries, but it does demonstrate various metabolites usefulin identifying perfusion defects and tissue viability. Thallium-201 and technetium-99m sestamibi are widely used

and may be combined to shorten the study of myocardial uptake of radioactive tracer at rest and during stress. Although a rest-and-stress thallium study takes more than 4 hours, a combined study performed with thallium andsestamibi may be completed in less than 2 hours.

By using PET, a rest-and-stress study with rubidium-82 may be completed in 30 minutes, because the agent hasa half-life of less than 5 minutes. A defect during stress that is not evident at rest indicates a zone of inducedischemia. A defect at rest and also during stress indicates persisting metabolic dysfunction, either from infarction(scar) or hibernation (prolonged dysfunction).

PET with ammonia, fluorinated glucose, or other agents may be used to determine if the tissue with a defect atrest is viable.


Nuclear medicine tests for CAD improve the predictive accuracy over that of stress tests alone, to approximately90%. The utility of these tests depends on the previous probability of disease and on whether they are being usedto identify CAD or to clarify the pathophysiology of known disease.

Limitations

Breast attenuation may cause an apparent defect on radionuclide images. Attenuation correction and multiplanar imaging mitigate the problem.

Unusual motion, such as that from a bundle branch block or coughing during imaging, may cause false-positiveresults. A persisting defect is commonly interpreted as a fixed defect or a scar, but it may represent prolonged yetstill-reversible ischemic impairment of tracer uptake.

The low resolution of nuclear medicine s tudies compared with that of other modalities may result in false-negativeresults. Also, global disease may be missed because defects are generally identified by comparing them toregions with high uptake of the t racer.

Contributor Information and Disclosures Author Justin D Pearlman, MD, ME, PhD, FACC, MA Chief, Division of Cardiology, Director of CardiologyConsultative Service, Director of Cardiology Clinic Service, Director of Cardiology Non-Invasive Laboratory,

Director of Cardiology Quality Program KMC, Dartmouth-Hitchcock Medical Center, Dartmouth Medical School

Justin D Pearlman, MD, ME, PhD, FACC, MA is a member of the following medical societies: AmericanCollege of Cardiology , American College of Physicians , American Federation for Medical Research ,International Society for Magnetic Resonance in Medicine , and Radiological Society of North America
http://www.rsna.org/http://www.ismrm.org/http://www.afmr.org/http://www.acponline.org/http://www.acc.org/


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Disclosure: Nothing to disclose.

Specialty Editor BoardJustin D Pearlman, MD, ME, PhD, FACC, MA Chief, Division of Cardiology, Director of CardiologyConsultative Service, Director of Cardiology Clinic Service, Director of Cardiology Non-Invasive Laboratory,Director of Cardiology Quality Program KMC, Dartmouth-Hitchcock Medical Center, Dartmouth Medical School

Justin D Pearlman, MD, ME, PhD, FACC, MA is a member of the following medical societies: AmericanCollege of Cardiology , American College of Physicians , American Federation for Medical Research ,

International Society for Magnetic Resonance in Medicine , and Radiological Society of North America


Bernard D Coombs, MB, ChB, PhD Consulting Staff, Department of Specialis t Rehabilitation Services, HuttValley District Health Board, New Zealand


Robert M Krasny, MD Resolution Imaging Medical Corporation

Robert M Krasny, MD is a member of the following medical societies: American Roentgen Ray Society and

Radiological Society of North America


Chief Editor Eugene C Lin, MD Attending Radiologis t, Teaching Coordinator for Cardiac Imaging, Radiology ResidencyProgram, Virginia Mason Medical Center; Clinical Assistant Professor of Radiology, University of WashingtonSchool of Medicine

Eugene C Lin, MD is a member of the following medical societies: American College of Nuclear Medicine , American College of Radiology , Radiological Society of North America , and Society of Nuclear Medicine


References

1. Antman EM, Cohen M, Bernink PJ, McCabe CH, Horacek T, Papuchis G. The TIMI risk score for unstableangina/non-ST elevation MI: A method for prognostication and therapeutic decision making. JAMA . Aug16 2000;284(7):835-42. [Medline] . [Full Text] .

2. Pearlman JD. NMR imaging and spectroscopy s tudies of the coronary arteries: II. 3-D reconstruction of invivo coronary arteries. In: Sideman S, Beyar R, eds. Image Analysis and Simulation of the CardiacSystem: Proceedings of 5th Henry Goldberg Workshop on Analysis. London, England: Freund; . 1990:

451-64.3. Aviram G, Finkelstein A, Herz I, et al. Clinical value of 16-slice multi-detector CT compared to invasive

coronary angiography. Int J Cardiovasc Intervent . 2005;7(1):21-8. [Medline] .

4. Flohr T, Stierstorfer K, Raupach R, et al. Performance evaluation of a 64-slice CT system with z-flyingfocal spot. Rofo . Dec 2004;176(12):1803-10. [Medline] .

5. Shaw LJ, Hausleiter J, Achenbach S, Al-Mallah M, Berman DS, Budoff MJ, et al. Coronary ComputedTomographic Angiography as a Gatekeeper to Invasive Diagnostic and Surgical Procedures: Results Fromthe Multicenter CONFIRM (Coronary CT Angiography Evaluation for Clinical Outcomes: An InternationalMulticenter) Registry. J Am Coll Cardiol . Nov 13 2012;60(20):2103-14. [Medline] .

6. Pearlman JD, Laham RJ, Simons M. Coronary angiogenesis: detection in vivo with MR imaging sensitiveto collateral neocirculation--preliminary study in pigs. Radiology . Mar 2000;214(3):801-7. [Medline] .

7. Pearlman JD, Hibberd MG, Chuang ML, et al. Magnetic resonance mapping demonstrates benefits of VEGF-induced myocardial angiogenesis. Nat Med . Oct 1995;1(10):1085-9. [Medline] .
http://reference.medscape.com/medline/abstract/7489368http://reference.medscape.com/medline/abstract/10715049http://reference.medscape.com/medline/abstract/23083780http://reference.medscape.com/medline/abstract/15573292http://reference.medscape.com/medline/abstract/16019611http://jama.ama-assn.org/content/284/7/835.fullhttp://reference.medscape.com/medline/abstract/10938172http://interactive.snm.org/http://www.rsna.org/http://www.acr.org/http://www.acnucmed.com/http://www.rsna.org/http://www.arrs.org/http://www.rsna.org/http://www.ismrm.org/http://www.afmr.org/http://www.acponline.org/http://www.acc.org/


14/15



8. Foote RS, Pearlman JD, Siegel AH, Yeo KT. Detection of exercise-induced ischemia by changes in B-type natriuretic peptides. J Am Coll Cardiol . Nov 16 2004;44(10):1980-7. [Medline] .

9. Pearlman JD. Three- (and more) dimensional imaging of the heart, great vessels, and coronary arteries.In: Cardiovascular Radiology. Dallas, TX: American Heart Association; . 1997: 5-8.

10. Pearlman JD, Gertz ZM, Wu Y, et al. Serial motion assessment by reference tracking (SMART):application to detection of local functional impact of chronic myocardial ischemia. J Comput Assist Tomogr . Jul-Aug 2001;25(4):558-62. [Medline] .

11. Schoenhagen P, Nissen SE. Intravascular ultrasonography: using imaging end points in coronaryatherosclerosis trials. Cleve Clin J Med . Jun 2005;72(6):487-9, 493-6. [Medline] .

12. Brenner D, Elliston C, Hall E, Berdon W. Estimated risks of radiation-induced fatal cancer from pediatricCT. AJR Am J Roentgenol . Feb 2001;176(2):289-96. [Medline] .

13. Foley SJ, McEntee MF, Achenbach S, Brennan PC, Rainford LS, Dodd JD. Breast surface radiation doseduring coronary CT angiography: reduction by breast displacement and lead shielding. AJR Am J Roentgenol . Aug 2011;197(2):367-73. [Medline] .

14. Rigatelli G, Rigatelli G. Screening angiography of supraaortic vessels performed by invasive cardiologistsat the time of cardiac catheterization: indications and results. Int J Cardiovasc Imaging . Apr-Jun

2005;21(2-3):179-83. [Medline] .

15. Pearlman JD, Boucher CA. Diagnostic value for coronary artery disease of chest pain during dipyridamole-thallium stress testing. Am J Cardiol . Jan 1 1988;61(1):43-5. [Medline] .

16. Liu H, Huang MP, Liang CH, Zheng JH, Wu ZB. [Detection and its clinical value of myocardial bridgingwith 64-slice spiral CT coronary angiography.]. Nan Fang Yi Ke Da Xue Xue Bao . Feb 2009;29(2):236-8.[Medline] .

17. Tsiflikas I, Drosch T, Brodoefel H, Thomas C, Reimann A, Till A, et al. Diagnostic accuracy and imagequality of cardiac dual-source computed tomography in patients with arrhythmia. Int J Cardiol . Feb 242009; [Medline] .

18. Halon DA, Dobrecky-Mery I, Gaspar T, Azencot M, Yaniv N, Peled N, et al. Pulse pressure and coronaryatherosclerosis in asymptomatic type 2 diabetes mellitus: A 64 channel cardiac computed tomographyanalysis. Int J Cardiol . Feb 24 2009; [Medline] .

19. Ito H, Dajani KA. A case with noncompaction of the left ventricular myocardium detected by 64-slicemultidetector computed tomography. J Thorac Imaging . Feb 2009;24(1):38-40. [Medline] .

20. Pearlman JD, Raptopoulos VD, Kleefield J. Three-dimensional elastic subtraction spiral CT angiography.Radiology . 1995;197:143-4.

21. Pizzuto F, Voci P, Bartolomucci F, Puddu PE, St rippoli G, Broglia L, et al. Usefulness of coronary flowreserve measured by echocardiography to improve the identification of significant left anterior descendingcoronary artery stenosis assessed by multidetector computed tomography. Am J Cardiol . Sep 12009;104(5):657-64. [Medline] .

22. Kaya MG, Okyay K, Yazici H, Sen N, Tavil Y, Turkoglu S, et al. Long-term clinical effects of magneticresonance imaging in patients with coronary artery stent implantation. Coron Artery Dis . Feb 25 2009;[Medline] .

23. Kwong RY, Sattar H, Wu H, Vorobiof G, Gandla V, Steel K, et al. Incidence and prognostic implication of unrecognized myocardial scar characterized by cardiac magnetic resonance in diabetic patients withoutclinical evidence of myocardial infarction. Circulation . Sep 2 2008;118(10):1011-20. [Medline] . [Full Text] .

24. Pearlman JD, Gazit Y. Accurate quantification of atheroma inside arterial walls by 1H-NMR. In: Woodford

FP, Davignon J, Sniderman A, eds. Atherosclerosis X: Proceedings of the 10th International Symposiumon Atherosclerosis, Montreal, Canada, October 9-14 1994. Elsevier;1995:1008-17.

25. Pearlman JD, Yaseen ZS. Multiplexed space-time maps for time-series data visualization: application to4D cardiac imaging. In: Erbacher RD, Pang A, eds. Visual Data Exploration and Analysis V. Proceedingsof the SPIE. Vol 3298 . Bellingham, WA: The International Society for Optical Engineering;1998:153-9.
http://circ.ahajournals.org/content/118/10/979.fullhttp://reference.medscape.com/medline/abstract/18725488http://reference.medscape.com/medline/abstract/19247183http://reference.medscape.com/medline/abstract/19699341http://reference.medscape.com/medline/abstract/19242302http://reference.medscape.com/medline/abstract/19246107http://reference.medscape.com/medline/abstract/19246109http://reference.medscape.com/medline/abstract/19246287http://reference.medscape.com/medline/abstract/3337016http://reference.medscape.com/medline/abstract/16015426http://reference.medscape.com/medline/abstract/21785082http://reference.medscape.com/medline/abstract/11159059http://reference.medscape.com/medline/abstract/16018290http://reference.medscape.com/medline/abstract/11473185http://reference.medscape.com/medline/abstract/15542280


15/15


Medscape Reference 2011 WebMD, LLC

26. Sellke FW, Laham RJ, Edelman ER, et al. Therapeutic angiogenesis with basic fibroblast growth factor:technique and early results. Ann Thorac Surg . Jun 1998;65(6):1540-4. [Medline] .

27. Lopez JJ, Laham RJ, Stamler A, et al. VEGF administration in chronic myocardial ischemia in pigs.Cardiovasc Res . Nov 1998;40(2):272-81. [Medline] .

28. Laham RJ, Rezaee M, Post M, et al. Intrapericardial delivery of fibroblast growth factor-2 inducesneovascularization in a porcine model of chronic myocardial ischemia. J Pharmacol Exp Ther . Feb2000;292(2):795-802. [Medline] .

29. Laham RJ, Chronos NA, Pike M, et al. Intracoronary basic fibroblast growth factor (FGF-2) in patients withsevere ischemic heart disease: results of a phase I open-label dose escalation study. J Am Coll Cardiol .Dec 2000;36(7):2132-9. [Medline] .

30. Sato K, Laham RJ, Pearlman JD, et al. Efficacy of intracoronary versus intravenous FGF-2 in a pig modelof chronic myocardial ischemia. Ann Thorac Surg . Dec 2000;70(6):2113-8. [Medline] .

31. De Luca G, Suryapranata H, Marino P. Reperfusion strategies in acute ST-elevation myocardial infarction:an overview of current status. Prog Cardiovasc Dis . Mar-Apr 2008;50(5):352-82. [Medline] .

32. Ellis SG, Tendera M, de Belder MA, van Boven AJ, Widimsky P, Janssens L, et al. Facilitated PCI inpatients with ST-elevation myocardial infarction. N Engl J Med . May 22 2008;358(21):2205-17. [Medline] .

33. Heberden, William. Pectus Dolor. Commentaries on the History and Cure of Diseases . 1802;MedicalTransactions 2, 59-67 (1772): [Full Text] .

34. Toyama T, Hoshizaki H, Isobe N, et al. Detecting viable hibernating myocardium in chronic coronaryartery disease--a comparison of resting 201Tl s ingle photon emission computed tomography (SPECT),99mTc-methoxy-isobutyl isonitrile SPECT after nitrate administration, and 201Tl SPECT after 2. Jpn Circ J . Dec 2000;64(12):937-42. [Medline] .
http://reference.medscape.com/medline/abstract/11194287http://www2.umdnj.edu/~shindler/heberden.htmlhttp://reference.medscape.com/medline/abstract/18499565http://reference.medscape.com/medline/abstract/18313480http://reference.medscape.com/medline/abstract/11156130http://reference.medscape.com/medline/abstract/11127452http://reference.medscape.com/medline/abstract/10640320http://reference.medscape.com/medline/abstract/9893720http://reference.medscape.com/medline/abstract/9647055

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