| Finding | A2 | P2 | Common Causes | | :--- | :--- | :--- | :--- | | | Increased | Increased | Systemic hypertension (loud A2), Pulmonary hypertension (loud P2), thin chest wall. | | Soft S2 | Decreased | Decreased | Aortic stenosis (reduced valve mobility), severe hypotension, obesity/emphysema. | | Absent P2 | Normal | Absent | Pulmonary atresia, severe pulmonary stenosis. |
In Atrial Septal Defect (secundum type), chronic right ventricular volume overload prolongs RV systole. The split becomes "fixed" because respiration cannot further alter the already maximal delay of P2. s2 heart sounds
| 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). | | Finding | A2 | P2 | Common