cardiac mr and viability

Case

•80 yo F with PMH of HTN, HLD, DM, CVA with a history of continuous chest pain x 2 weeks. Patient was found to have a LBBB on unknown duration. Cardiac enzymes were negative. The patient was transferred to WHC for further management.

Dobutamine CMR• Contractile reserve can be assessed using low dose dobutamine

stress test

• Allows for superior endocardial border definition facilitating more accurate wall motion and wall thickening

• Dobutamine CMR vs PET

• 35 patients with mild LV dysfunction

• Sensitivity of 88% and Specificity of 87% for detecting regions of viable myocardium

• Reduced predictive ability with more severe dysfunction is present at rest with specificity in the 80% range, but sensitivity limited to 50%

• If contractile function improves with dobutamine the there is likely viability

• Lack of improvement, however, does may not rule out viability as ischemia may develop at even low levels of dobutamine administration

Mahrholdt, et al. Heart 2007

Contrast Enhancement CMR

• Regions of myocardial infarct exhibit signal intensity (contrast enhancement) on T1-weighted images after administration gadolinium

• Gadolinium passively diffuses into the intracellular space due to rupture of myocyte membranes leading to increased contrast concentration in interstitial space between collagen fibers

• Contrast images are acquired mid-diastole

• The inversion time must be manually selected to null signal from normal myocardial regions

• This varies btw patients as a function of dose and and time after administration of contrast due to varying pharmacokinetics. Mahrholdt, et al. Heart 2007

Mahrholdt, et al. Heart 2007

Use of contrast enhanced MRI to identifify reversible myocardial dysfunction

• Methods

• 50 patients prospectively enrolled

• Of these 41 patient had MRI before and after revascularization

• Inclusion criteria

• Scheduled to undergo revascularization

• Had regional wall motion abnormalities bu ventriculogram or echo

• Exclusion criteria

• Unstable angina

• NYHA Class IV heart failure

• Contraindication for MRI

• Results

• 80 percent of patient demonstrated hyperenhancement

• 50 percent with q waves on ekg showed hyperenhacement

• Before revascularization, 38 percent of pts had abnormal contractility and 33 percent had some areas of hyperenhancement

• Areas with dysfunctional, but non-hyperenhancing myocardium improved significantly after revascularization Kim et al NEJM, 2000

Viability post CABG• Methods

• 60 patients undergoing mutlivessel CABG were studies preoperatively, 6 days and 6 months post op

• Patients were also randomized to be off pump and on pump

• Exclusion: age > 75 yo, severe pre-existing LV dysfunction, CKD, typical MRI contraindications

• Results

• Preoporatively 21% of wall segments had abnormal regional function, whereas 14% showed evidence of hyperenhancement

• At 6 months, 57% of wall segments had improved contraction by at least one grade

• Strong correlation between the transmural extent of hyperenhancement and ther recovery of in regional function at 6 monthsSelvanayagam et al Circulation, 2004

Predicting Late Myocardial Recovery and Outcomes in Early hours of STEMI

• Methods

• 104 prospectively enrolled patients with successfully reperfused STEMI

• Exclusion criteria were recent MI (<6months), shock requiring IABP, respiratory failure, contraindications for MRI

• Subjects were followed prospectively at 33 months and MRI was repeated at 6 months

• Primary endpts were change in LVEF and LV dysfunction at 6 months.

• Secondary endpt was MACE

• Results

• LGE was the best predictor of late LV dysfunction

• LGE > 23% of volume accurately predicted late dysfunction (sensitivity 89%, specificity 74%)

• LGE > 23 % carried a hazard ration of 6.1 percent for adverse events (p<0.0001)

Larose et al JACC, 2010