Interpretation of Abnormal ECGs
Abnormal Component | Description | Possible Causes |
|---|---|---|
P waves | Abnormal | Left or right atrial hypertrophy, atrial escape (ectopic) beats |
P waves | Absent | Atrial fibrillation, sinus node arrest or exit block, hyperkalemia (severe) |
P-P interval | Varying | Sinus arrhythmia |
PR interval | Long | |
PR interval | Varying | Mobitz type I atrioventricular block, multifocal atrial tachycardia |
QRS complex | Wide | Right or left bundle branch block, ventricular flutter, ventricular fibrillation, hyperkalemia |
QT interval | Long | Myocardial infarction, myocarditis, stress cardiomyopathy, hypocalcemia, hypokalemia, hypomagnesemia, hypothyroidism, subarachnoid hemorrhage, intracerebral hemorrhage, stroke, congenital long QT syndrome |
QT interval | Short | |
ST segment | Depression | pulmonary embolism; left bundle branch block in leads V5–V6 and possibly in I and aVL; right bundle branch block in leads V1–V3 and possibly in II, III, and aVF; hyperventilation; hypokalemia |
ST segment | Elevation | Myocardial ischemia, acute myocardial infarction, left bundle branch block in leads V1–V3 and possibly in II, III, and aVF, acute pericarditisathlete's heart), hypothermia |
T wave | Tall | Hyperkalemia, acute myocardial infarction, left bundle branch block, stroke, ventricular hypertrophy |
T wave | Small, flattened, or inverted | |
U wave | Prominent | Hypokalemia, hypomagnesemia, ischemia |