Intraoperative Direct Measurement of Left Ventricular Outflow Tract Gradients to Guide Surgical Myectomy for Hypertrophic Cardiomyopathy

Study Questions:

Is intraoperative direct measurement of left ventricular outflow tract (LVOT) gradient important in the management of patients with hypertrophic obstructive cardiomyopathy (HOCM) undergoing transaortic septal myectomy?


This was a retrospective study assessing echocardiographic and direct measurement of LVOT gradients in 198 patients (>18 years of age) with HOCM who underwent transaortic septal myectomy. Evaluated baseline and provoked LVOT gradients (Valsalva or inhaled amyl nitrate for transesophageal echocardiography [TEE] and induced premature ventricular contraction or isoproterenol infusion intraoperatively) were obtained by TEE and by direct pressure measurement in the left ventricle and aorta.


After induction of anesthesia and prior to myectomy, LVOT gradient was significantly less severe by direct measurement than by preoperative TEE in 60% of patients (p < 0.001), was significantly more severe in 38% (p < 0.001), and the same in only 2%. Provocation tests were performed preoperatively in 50% primarily in symptomatic patients with low (<30 mm Hg) gradients. In all patients, the LVOT gradient increased significantly with provocation. In 96% of patients, the LVOT gradient significantly decreased after initial septal myectomy by direct measurement and by TEE (p < 0.001 for both). Cardiopulmonary bypass was resumed in 4% because of a persistently elevated LVOT gradient. Intraoperative TEE was technically inadequate in assessing LVOT gradient in 38% of patients.


Direct pressure measurements of LVOT gradients provide important information at baseline and following septal myectomy to determine adequacy of repair due to the significant number of patients demonstrating heterogeneous alterations in gradients under general anesthesia compared to preoperative baseline TEE.


Due to the dynamic nature of LVOT obstruction in patients with septal hypertrophy, it is imperative to have an adequate assessment of the baseline LVOT gradient in patients undergoing septal myectomy so that there is an adequate point for comparison under similar loading conditions. The addition of provoked LVOT gradient pressure measurements helps to identify patients who are at risk for severe LVOT obstruction with activity that may not be readily apparent at baseline, and to ensure that it is adequately addressed at the time of surgery while the patient is under general anesthesia.

Clinical Topics: Arrhythmias and Clinical EP, Dyslipidemia, Heart Failure and Cardiomyopathies, Noninvasive Imaging, EP Basic Science, SCD/Ventricular Arrhythmias, Lipid Metabolism, Acute Heart Failure, Echocardiography/Ultrasound

Keywords: Heart Septum, Cardiomyopathy, Hypertrophic, Ventricular Outflow Obstruction, Nitrates, Heart Failure, Pentanols, Isoproterenol, Cardiopulmonary Bypass, Ventricular Premature Complexes, Heart Ventricles, Echocardiography, Transesophageal, Echocardiography

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