A 52-year-old man is found to have a high-pitched, early diastolic murmur at the left sternal border, accentuated by leaning forward. The murmur is suspected to be aortic regurgitation secondary to aortic root dilatation. Which investigation is most appropriate to assess the aortic root diameter and determine the need for surgical intervention?

Explanation

## Investigation of Choice for Aortic Root Assessment in Aortic Regurgitation ### Why Transthoracic Echocardiography is Correct **Key Point:** Transthoracic echocardiography (TTE) with precise measurement of the aortic root diameter at the sinuses of Valsalva is the first-line, non-invasive investigation for assessing aortic root dilatation and determining surgical intervention thresholds. **High-Yield:** TTE provides: - Direct visualization of aortic root, sinuses of Valsalva, sinotubular junction, and ascending aorta - Measurement of aortic root diameter (normal <40 mm; dilatation >40 mm) - Assessment of aortic valve leaflets and severity of regurgitation (Doppler) - Evaluation of left ventricular dimensions and function - Cost-effective, non-invasive, widely available, repeatable for serial monitoring ### Aortic Root Diameter Thresholds for Surgical Intervention | Aortic Root Diameter | Clinical Significance | Management | |----------------------|----------------------|-------------| | <40 mm | Normal | Medical management; serial echo | | 40–45 mm | Mild–moderate dilatation | Monitor annually; beta-blocker/ARB | | 45–50 mm | Significant dilatation | Consider surgery if family hx of dissection or rapid progression | | >50 mm | Severe dilatation | Surgery indicated (elective) | | >55 mm | Critical dilatation | Surgery urgent; high dissection risk | **Clinical Pearl:** The early diastolic murmur at the left sternal border, accentuated by leaning forward (Cormican sign), is classic for aortic regurgitation. Aortic root dilatation is a common etiology in Marfan syndrome, bicuspid aortic valve, hypertension, and aortitis. Serial TTE monitoring is essential to detect progressive dilatation and guide timing of aortic root replacement (composite graft or valve-sparing procedures). ### Why Other Options Are Suboptimal **Transesophageal echocardiography (TEE):** Reserved for intraoperative monitoring, assessment of prosthetic valve function, or when TTE images are inadequate. It is invasive and not first-line for routine aortic root measurement. **Cardiac MRI:** Excellent for detailed aortic root and ascending aorta imaging and is preferred in Marfan syndrome or when TTE is inconclusive. However, it is more time-consuming, expensive, and less available than TTE; not first-line for initial assessment. **Aortography:** Invasive, carries risk of dissection, and does not provide functional assessment of the aortic valve. Reserved for coronary angiography or hemodynamic assessment when clinically indicated. [cite:Harrison 21e Ch 297]