Abstract 700: Left Ventricular Outflow Tract (LVOT) Diameter/Aortic Valve Diameter Ratio is an Accurate Non-invasive Cardiac MRI Marker for Estimation of LVOT Obstruction in Patients With Hypertrophic Cardiomyopathy
Purpose: To evaluate if LVOT diameter/aortic valve (LVOT/AO) ratio measured by cardiac MRI is an accurate marker to estimate LVOT obstruction in patients with hypertrophic cardiomyopathy.
Methods: 92 patients with hypertrophic cardiomyopathy (HCM) underwent cardiac magnetic resonance imaging (MRI) and echocardiogram within 24h. Using a 1.5T MR system ECG gated steady state free precession cine MRI was obtained in a LV outflow tract view. The systolic most severe narrowing of the LVOT was divided by the aortic valve diameter to calculate the LVOT/AO ratio. The LVOT pressure gradient was derived by Doppler echocardiography. Patients were divided in 3 groups: LVOT gradient <10mmHg (low, n=31), 10–30mmHg (intermediate, n=30) and >30mmHg (high, n=31).
Results: There were significant differences of the LVOT/AO ratio between the 3 subgroups (low 0.62±0.13, intermediate 0.38±0.13, high 0.24±0.09, p<0.001). For detection of a gradient ≥10mmHg (and ≥30mmHg) using the LVOT/AO ratio the area under the curve was 0.95 (and 0.91); a cutoff LVOT/AO ratio of 0.41 (and 0.30) yielded the best balanced sensitivity (88% and 89%) and specificity (92% and 81%). There was a nonlinear relationship between LVOT gradient and LVOT/OA ratio (picture) and a linear correlation between the LVOT/AO ratio and the natural logarithm of the LVOT pressure gradient (r=−0.82, p<0.0001) with good interobserver agreement (concordance correlation coefficient 0.89).
Conclusion: The LVOT/AO ratio is an accurate, noninvasive cardiac MRI marker to assess LVOT pressure gradients in patients with HCM.