Inferolateral ischemia with QT prolongation

ECG Quiz 20

Inferolateral ischemia
Inferolateral ischemia with QT prolongation

This ECG tracing shows mild ST segment depression in inferior leads II, III and aVF, and T wave inversion in leads I, aVL and V3 to V6. There is a pathological Q wave in aVL, with width more than 40 ms. R waves are tall in V5 and V6 suggesting left ventricular hypertrophy. QT interval is 520 ms, which at the heart rate of 60/min has to be taken as the corrected QT interval and is therefore prolonged. Myocardial ischemia is an important common cause of QT interval prolongation. Electrolyte abnormalities like hypokalemia are also common cause for QT interval prolongation.

QT interval can be prolonged after a cardiac arrest and associated with giant T wave inversions. Drug induced QT prolongation is also an important aspect which mandates QT testing for all new drugs. Class Ia, Ic and Class III antiarrhythmic drugs can cause prolongation of QT interval and so can a wide array of drugs including macrolide antibiotics and antipsychotic drugs. QT prolongation can predispose to life threatening ventricular tachyarrhythmias.