S2 Heart Sounds [repack] -

| 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). |

| 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 | s2 heart sounds

1. Introduction The second heart sound (S2) is produced by the closure of the semilunar valves (aortic and pulmonary) at the beginning of ventricular diastole. It marks the end of systole. Unlike the first heart sound (S1), which is monophonic, S2 is normally split into two audible components: A2 (aortic valve closure) and P2 (pulmonary valve closure). Analysis of S2—its intensity, splitting pattern, and pitch—provides critical diagnostic information about hemodynamics and valvular function. | Pattern | Definition | Key Auscultatory Features