| Physiologic or positional factors |
| Normal variant "septal" q waves |
| Normal variant Q waves in leads V1,V2, aVL, III, and aVF |
| Left pneumothorax or dextrocardia: loss of lateral precordial R wave progression |
| Myocardial injury or infiltration |
| Acute processes: myocardial ischemia or infarction, myocarditis, hyperkalemia |
| Chronic processes: myocardial infarction, idiopathic cardiomyopathy, myocarditis, amyloidosis, tumor, sarcoid, scleroderma, Chagas disease, echinococcus cyst |
| Ventricular hypertrophy or enlargement |
| Left ventricle: slow R wave progression in which there are small or absent R waves in the mid-precordial leads |
| Right ventricle: reversed R wave progression in which there is a progressive decrease in R wave amplitude from V1 to the mid-lateral precordial leads, or slow R wave progression, particularly with chronic obstructive lung disease or acute pulmonary embolism |
| Hypertrophic cardiomyopathy - may simulate anterior, inferior, posterior, or lateral infarcts |
| Conduction abnormalities |
| Left bundle branch block - slow R wave progression in which there are small or absent R waves in the mid-precordial leads |
| Wolff-Parkinson-White patterns |
