Which finding best discriminates between aortic stenosis and aortic regurgitation in a 65-year-old man with a diastolic murmur and a wide pulse pressure?

Explanation

## Distinguishing Aortic Stenosis from Aortic Regurgitation ### Hemodynamic and Clinical Contrast **Key Point:** Aortic stenosis (AS) obstructs systolic outflow, raising LV systolic pressure and narrowing pulse pressure. Aortic regurgitation (AR) allows diastolic runoff, widening pulse pressure and producing characteristic peripheral signs. ### Comparative Table | Feature | Aortic Stenosis | Aortic Regurgitation | |---------|-----------------|----------------------| | **Pulse Pressure** | Narrow (↓ pulse pressure) | Wide (↑ pulse pressure) | | **Pulse Quality** | Slow-rising (pulsus parvus et tardus) | Bounding, collapsing (water-hammer) | | **Systolic Murmur** | Ejection systolic (crescendo-decrescendo) | Early diastolic (high-pitched, blowing) | | **Diastolic Murmur** | Absent | Present (hallmark) | | **LV Pressure** | ↑ Systolic | Normal systolic, ↑ end-diastolic | | **LV Hypertrophy** | Concentric | Eccentric | | **Peripheral Signs** | Slow pulse, narrow pulse pressure | Bounding pulse, wide pulse pressure | ### Why This Feature Discriminates **High-Yield:** The **water-hammer pulse** (or Corrigan's pulse) is pathognomonic for significant aortic regurgitation. It results from the rapid rise and fall of aortic pressure as blood regurgitates back into the LV during diastole. This produces the characteristic bounding, collapsing pulse palpable at the wrist. In contrast, AS produces a **slow-rising pulse** (pulsus parvus et tardus) due to obstruction of systolic outflow. **Mnemonic:** **WATER-HAMMER = AR** (Aortic Regurgitation). The pulse feels like a hammer blow—sudden, forceful, then collapses. **Clinical Pearl:** The wide pulse pressure in AR (elevated systolic, normal or low diastolic) is a direct consequence of the regurgitant jet. This also explains other peripheral signs: pistol-shot femorals, Quincke's sign (nail bed pulsations), and Hill's sign (elevated leg BP > arm BP by >20 mmHg). ### Why Other Options Are Incorrect - **LV hypertrophy on ECG:** Both AS and AR cause LVH, though the pattern differs (concentric in AS, eccentric in AR). LVH alone does not discriminate between them. - **Systolic ejection murmur at right upper sternal border:** This is the murmur of AS, not AR. The stem explicitly states the patient has a diastolic murmur, which is the hallmark of AR. A patient with both AS and AR would have both murmurs, but the question asks for the discriminating feature. - **Elevated LVEDP on catheterization:** Both AS and AR can elevate LVEDP (in AS due to impaired diastolic relaxation; in AR due to volume overload). This is not a discriminating feature. [cite:Harrison 21e Ch 297]