Basic EKG For Dummies

R. Javelosa, Jr., MD. FPCP. FPCCSection of Cardiology

Department of MedicineUERMMMC

Cardiac Anatomy

Cardiac Cycle

Step 1: Rapid filling of ventricles

• Ventricular pressure drops below atrial pressure

• AV valves are open, semilunar valves are closed

• Rapid ventricular filling occurs

• 70-90% of the ventricles fill with blood

Cardiac Cycle

Step 2: Atrial systole

• P wave occurs

• Atrial contraction

• Pushed 10-30% more blood into ventricle

Cardiac Cycle

Step 3: Isovolumetric contraction

• QRS just occurred

• Contraction of the ventricles causes ventricular pressure to rise above atrial pressure,

• AV valves close

• Ventricular pressure is still less than aortic pressure

• Semilunar valves are closed

• Volume of blood in the ventricle is EDV

Cardiac Cycle

Step 4: Ejection

• Contraction of the ventricles causes ventricular pressure to rise above aortic pressure,

• Semilunar valves open

• Ventricular pressure is still greater than atrial pressure

• AV valves are still closed

• Volume of blood ejected by the ventricles: stroke volume (SV)

Cardiac Cycle

Step 5:

• T-wave occurs

• Ventricular pressure drops below aortic pressure

• Back pressure causes semilunar valves to close

Cardiac Cycle

Step 6: Isovolumetric relaxation

• AV valves are still closed

• Semilunar valves are still closed

• Volume of blood in ventricles: ESV

P

QRS

T

The Limb Leads

The Precordial Leads

The Precordial Leads

Sequence of ECG Interpretation

1. Rate2. Rhythm3. Axis4. Hypertrophy5. Infarction6. Injury7. Ischemia

Interpretation Sequence

• Check the patient details - is the ECG correctly labelled?

• What is the rate? • Is this sinus rhythm? If not, what is going on? • What is the mean frontal plane QRS axis (You may

wish at this stage to glance at the P and T wave axes too)

• Are the P waves normal (Good places to look are II and V1)

• What is the PR interval?

Interpretation Sequence• Are the QRS complexes normal? Specifically, are

there: – significant Q waves? – voltage criteria for LV hypertrophy? – predominant R waves in V1? – widened QRS complexes?

• Are the ST segments normal, depressed or elevated? Quantify abnormalities.

• Are the T waves normal? What is the QT interval? • Are there abnormal U waves?

What is the Rate?• Identify an R wave that falls on the marker of a `big block' • Count the number of big blocks to the next R wave. • 300 / # of big squares or 300, 150, 100, 75, 50 sequence• 1500 / # of small squares

What is the Rate?

What is the Rate?

Step 2. What is the Rhythm?

• Sinus?• Junctional?• Ventricular?• Pacemaker?• AF?• VF?

Junctional or AV Nodal Rhythm

Step 3. What is the QRS Axis?

Frontal QRS Axis

Extreme RAD Left axis NW axis deviation

Right axis Normal axisdeviation

Using leads I and aVF the axis can be calculated to within one of the four quadrants at a glance.

                                      

The QRS Axis

• Normal axis : both I and aVF (+)

• Right axis deviation : lead I (-) and aVF (+)

• Left axis deviation: lead I (+) and aVF (-)

• Northwest Territory : both I and aVF (-)

Causes of left axis deviation• Left ventricular hypertophy• Inferior myocardial infarction • Artificial cardiac pacing • Emphysema • Hyperkalemia • Wolff-Parkinson-White syndrome - right sided accessory

pathway • Tricuspid atresia • Ostium primum ASD

Causes of right axis deviation

• Normal finding in children and tall thin adults • Right ventricular hypertrophy • Chronic lung disease even without pulmonary hypertension • Anterolateral myocardial infarction • Left posterior hemiblock • Pulmonary embolism• Wolff-Parkinson-White syndrome - left sided accessory

pathway • Atrial septal defect • Ventricular septal defect

Causes of a Northwest axis • Emphysema • Hyperkalemia • Lead transposition • Artificial cardiac pacing • Ventricular tachycardia

Step 4. Check the P-R Interval for AV blocks

Second Degree AV Block

• Mobitz Type I (Wenckebach)• Mobitz Type II

Causes of AV Blocks

• Autonomic Carotid sinus

hypersensitivity

• Metabolic/endocrine Hyperkalemia Hypothyroidism Hypermagnesemia Adrenal insufficiency

• Drug-related Beta blockers Adenosine Ca channel blockers Antiarrhythmics (class I & III) Digitalis Lithium

Causes of AV Blocks

• Infectious Endocarditis Tuberculosis Lyme disease Diphtheria Chagas disease Toxoplasmosis Syphilis

• Heritable/congenital Congenital heart disease Maternal SLE Kearns-Sayre syndrome Emery-Dreifuss MD Myotonic dystrophy Progressive familial heart block

Causes of AV Blocks• Inflammatory SLE MCTD Rheumatoid arthritis Scleroderma • Infiltrative Amyloidosis Hemochromatosis Sarcoidosis • Coronary artery disease Acute MI

• Neoplastic/traumatic Lymphoma Radiation Mesothelioma Catheter ablation Melanoma • Degenerative Lev disease Lenègre disease

Step 5. Look for Ectopic beats

• Atrial?• Ventricular?

Step 6. Is there Chamber Enlargement?

Left atrial enlargement

a. P wave duration equal or more than 0.12 sec.

b. Notched, slurred P wave in lead I and II (P mitrale).

c. Biphasic P wave in lead V1 with a wide deep and negative terminal component.

Right atrial enlargementa. P wave duration equal or

less than 0.11 sec. b. Tall, peaked T wave equal

or more than 2.5 mm in amplitude in lead II,III or aVF (P pulmonale).

c. Mean P wave axis shifted to the right (more than +70 degrees).

Ventricular Hypertrophy

Left Ventricular Hypertrophy

Left ventricular enlargementa. "Voltage criteria":

1. R or S wave in limb lead equal or more than 20mm 2. S wave in V1,V2 or V3 equal or more than 30mm 3. R wave in V4,V5 or V6 equal or more than 30mm.

b. Depressed ST segment with inverted T waves in lateral leads(strain pattern ;more reliable in the absence of digitalis therapy.

c. Left axis of -30 degree or more.

d. QRS duration equal or more than 0.09 sec. e. Time of onset of the intrinsicoid deflection ( time from the beginning of the QRS

to the peak of the R wave ) equal or more than 0.05 sec in lead V5 or V6.

Right ventricular enlargementa. Tall R waves over the right precordium and deep S waves

over the left precordium ( R:S ratio in lead V1 > 1.0) b. Normal QRS duration (if no bundle branch block) c. Right axis deviation. d. ST-T "strain" pattern over the right precordium. e. Late intrinsicoid deflection in lead V1 or V2.

Step 7. Examine QRS Duration

Left bundle branch block

a. QRS duration equal or more than 0.12 sec. b. Broad , notched or slurred R wave in lateral leads( I,

aVL , V5,V6 ) c. QS or rS pattern in the anterior precordium.d. Secondary ST-T wave changes ( ST and T wave

vectors are opposite to the terminal QRS vectors). e. Late intrinsicoid deflection in lead V5 and V6.

Right bundle branch block

a. QRS duration equal or more than 0.12 sec. b. Large R' wave in lead V1( rsR' ). c. Deep terminal S wave in lead V6. d. Normal septal Q wave. e. Inverted T wave in lead V1 ( secondary T wave

changes ). f. Late intinsicoid deflection in lead V1 and V2.

Step 8. Look for ST Segment Abnormalities

Localization of Infarction

Localization of MI with the help of EKG

• Anterior wall V1 through V6

• Anteroseptal V1 through V3

• Inferior II, III, aVF

• Right ventricular V4R, V3R

• Posterior wall V7 through V9 V1 through V3 ( ST depression)

Thank you for not sleeping!