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 (PGLPA and PGApA, respectively) and record a signal of mitral regurgitation (MR). The beam incident angles to LVOT flow in LPA ( LPA) and in ApA ( ApA) were measured using color Doppler flow imaging.Results. PGLPA was distinctly greater (>= 10mmHg) than PGApA in 7 patients (37%); they were similar in 6 (32%); and PGLPA was distinctly smaller (<= -10mmHg) than PGApA 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 LPA was significantly smaller and Cos ApA was significantly greater in the HOCM patients than 10 control subjects (p<0.001 for both). Both PGLPA and PGApA correlated with the invasive pressure gradient (r=0.99 and r=0.97) in 7 patients who underwent invasive study. PGLPA was closer to the invasive pressure gradient than PGApA 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. (J Echocardiogr 2005; 3: 140-147)