Agreement Between Transthoracic Echocardiography and CT Coronary Angiography for Left Ventricular Outflow Tract Diameter in Stable Indian Adults: A Prospective Observational Study.

To assess the agreement between transthoracic echocardiography (TTE) and computed tomography coronary angiography (CT-CAG) for measurement of the left ventricular outflow tract diameter (LVOTd) in the parasternal long-axis orientation, and to explore anthropometric predictors of LVOTd in stable Indian adults. In this prospective, single-centre study, hemodynamically stable adults in sinus rhythm undergoing outpatient CT-CAG were enrolled (October–December 2024). LVOTd was measured by TTE (parasternal long-axis view, mid-systole) and by CT in a matched long-axis orientation (anteroposterior diameter at the same anatomical level) by separate blinded readers. Agreement was assessed using intraclass correlation coefficients (ICC) and Bland–Altman analysis. Of 100 screened subjects, 91 were analysed (mean age 53.9 ± 8.7 years; 72.5% male; 84.6% health screening). Mean LVOTd was 1.94 ± 0.24 cm (CT-CAG) versus 1.88 ± 0.18 cm (TTE). The two modalities demonstrated good agreement for LVOTd (ICC 0.85; 95% CI 0.77–0.89). Bland–Altman analysis revealed a bias of 0.05 cm (limits of agreement 0.25 to 0.34 cm), with CT-CAG yielding larger values. Agreement diminished for derived parameters, being moderate for LVOT area (ICC 0.74) and modest for cardiac output (CO) (ICC 0.57; bias 0.5 L/min), indicating non-interchangeability for hemodynamic calculations. Body weight was the sole significant predictor of LVOTd (β = 0.004 cm/kg; R 2 = 0.29; p = 0.04). In stable Indian adults, TTE and CT-CAG show good agreement for LVOTd measured in a comparable anatomical plane. Agreement diminishes for derived area and CO estimates. The weight-based model requires validation in larger, more diverse cohorts.