Usefulness of Left Parasternal Approach for the Continuous-Wave Doppler Measurement of Left Ventricular Outflow Tract Pressure Gradient in Patients With Hypertrophic Cardiomyopathy

Abstract

Background. The apical approach (ApA) has been usually employed for the continuous-wave Doppler (CWD) measurement of pressure gradient in the left ventricular outflow tract (LVOT) in patients with hypertrophic obstructive cardiomyopathy (HOCM). This study aimed to assess the usefulness of a left parasternal approach (LPA) using the most cranial part of the echo-window for the measurement of the LVOT pressure gradient.
Methods. CWD using LPA and ApA was performed in 19 patients with HOCM to measure LVOT peak pressure gradients (PG_LPA and PG_ApA, respectively) and record a signal of mitral regurgitation (MR). The beam incident angles to LVOT flow in LPA (θ_LPA) and in ApA (θ_ApA) were measured using color Doppler flow imaging.
Results. PG_LPA was distinctly greater (>= 10mmHg) than PG_ApA in 7 patients (37%); they were similar in 6 (32%); and PG_LPA was distinctly smaller (<= -10mmHg) than PG_ApA in 6 (32%). All patients had MR. While all the MR jets in ApA shifted away from the probe, i.e. to the same side of the LVOT flow, 18 of the 19 MR jets shifted to the opposite side of the LVOT flow, when using LPA. Cos θ_LPA was significantly smaller and Cos θ_ApA was significantly greater in the HOCM patients than 10 control subjects (p<0.001 for both). Both PG_LPA and PG_ApA correlated with the invasive pressure gradient (r=0.99 and r=0.97) in 7 patients who underwent invasive study. PG_LPA was closer to the invasive pressure gradient than PG_ApA in 6 patients.
Conclusions. LPA provided a more accurate measurement of pressure gradient than ApA in about one third of HOCM patients, probably due to the altered direction of LVOT flow in HOCM. LPA is also useful in distinguishing LVOT flow from MR jet commonly seen in these patients.