| Pattern | Definition | Key Auscultatory Features | Most Likely Diagnoses | | :--- | :--- | :--- | :--- | | | A2-P2 interval is abnormally wide and does not vary with respiration. | Split heard in both inspiration and expiration; no change in interval. | Atrial Septal Defect (ASD) (classic), Right bundle branch block (RBBB), severe pulmonary stenosis. | | Paradoxical (Reversed) Splitting | P2 occurs before A2; split widens during expiration and narrows during inspiration. | Split heard in expiration; inspiration causes fusion into a single sound. | Left bundle branch block (LBBB) , severe aortic stenosis, hypertrophic cardiomyopathy, right ventricular pacing. | | Wide Physiologic Splitting | Split is wider than normal but still varies with respiration (wider on inspiration). | Normal respiratory variation, but interval > 30-40 ms at the sternal edge. | RBBB (most common), pulmonary stenosis, mitral regurgitation, pulmonary embolism (acute). |
Three major abnormal patterns are clinically significant: s2 heart sounds
| Condition | S2 Intensity | Splitting Pattern | Respiratory Variation | Other Clues | | :--- | :--- | :--- | :--- | :--- | | | Normal A2 > P2 | Physiologic | Present (widens on inspiration) | Asymptomatic | | Hypertension | Loud A2 | Physiologic | Present | Elevated BP | | Pulmonary HTN | Loud P2 (may equal or exceed A2) | Narrow or single | Minimal | Right ventricular heave | | Aortic Stenosis | Soft/absent A2 | Paradoxical (if severe) | Reversed | Late-peaking murmur | | ASD | Normal or wide | Wide fixed | Absent | Systolic murmur at LUSB | | LBBB | Normal | Paradoxical | Reversed | Wide QRS on ECG | | RBBB | Normal | Wide physiologic or fixed | Present or absent | Wide QRS on ECG | | Pattern | Definition | Key Auscultatory Features