| 1 | Definition | PR interval > 200 ms on ECG without dropped beats. |
| 2 | Site of Delay | Typically occurs at the AV node; sometimes in the His bundle. |
| 3 | ECG Findings | Regular rhythm, prolonged and constant PR interval. |
| 4 | Symptoms | Usually asymptomatic; detected incidentally. |
| 5 | Causes | Increased vagal tone, drugs (β-blockers, CCBs, digoxin), ischemia. |
| 6 | Athlete Physiology | Common benign finding in well-trained athletes. |
| 7 | Drug Effects | Caused by AV nodal blockers like beta-blockers and digoxin. |
| 8 | Electrolyte Causes | Hyperkalemia slows AV nodal conduction, prolonging PR. |
| 9 | Reversibility | May resolve with drug withdrawal or correcting imbalances. |
| 10 | PR Interval Range | Usually 200–300 ms; >300 ms may be clinically significant. |
| 11 | Hemodynamics | Long PR may impair atrioventricular synchrony, causing MR. |
| 12 | Risk of Progression | Can progress to higher-degree block in diseased conduction. |
| 13 | Associated Conditions | Seen in Lyme disease, inferior MI, valvular disorders. |
| 14 | AFib Risk | Increases long-term risk of atrial fibrillation. |
| 15 | PR Measurement | From start of P wave to start of QRS complex. |
| 16 | Pacemaker Indication | Not needed unless symptoms or progression occur. |
| 17 | Marked PR Prolongation | PR > 300 ms may cause symptoms, termed “marked first-degree.” |
| 18 | Differentiation | Different from Mobitz I, which has variable PR and dropped beats. |
| 19 | Age Factor | More common in elderly due to conduction system fibrosis. |
| 20 | Management | No treatment if asymptomatic; treat underlying causes if needed. |
