| P wave |
| Left atrial enlargement: negative portion of the P wave in lead V1 ≥0.1 mV in depth and ≥0.04 in duration |
| Right atrial enlargement: peaked P wave in leads II and III or V1 ≥0.25 mV in amplitude |
| QRS complex |
| Frontal plane axis deviation: right ≥+120º or left –30º to –90º |
| Increased voltage: amplitude of R or S wave in a standard lead ≥2 mV, S wave in lead V1 or V2 ≥3 mV, or R wave in lead V5 or V6 ≥3 mV |
| Abnormal Q waves ≥0.04 s in duration or ≥25 percent of the height of the ensuing R wave or QS pattern in two or more leads |
| Right or left bundle branch block with QRS duration ≥0.12 s |
| R or R' wave in lead V1 ≥0.5 mV in amplitude and R/S ratio ≥1 |
| ST-segment, T-waves, and QT interval |
| ST-segment depression or T-wave flattening or inversion in two or more leads |
| Prolongation of heart rate corrected QT interval >0.44 s in males and >0.46 s in females |
| Rhythm and conduction abnormalities |
| Premature ventricular beats or more severe ventricular arrhythmias |
| Supraventricular tachycardias, atrial flutter, or atrial fibrillation |
| Short PR interval (<0.12 s) with or without 'delta' wave |
| Sinus bradycardia with resting heart rate ≤40 beats/min* |
| First (PR ≥0.21 s¶), second, or third degree atrioventricular block |
