Available online 6 May 2025

APM-IVS distance was measured at mid-ventricle, apical 3-chamber view, end-diastole

APM-IVS distance was an independent factor of LV mid-ventricular obstruction with HCM

A smaller APM-IVS distance was correlated with LV apical aneurysm and higher NYHA.

After myectomy, APM-IVS distance increased.

Left ventricular mid-ventricular obstruction (MVO) is thought to be dynamic with hypertrophic cardiomyopathy (HCM). Therefore, the distance between the anterior papillary muscle and interventricular septum was employed as a parameter named APM-IVS distance for assessing MVO by rest echocardiography.

MVO was defined as a mid-ventricular gradient of ≥ 30 mmHg at rest or after being provoked. APM-IVS distance was analyzed on apical three chamber view at end-diastole.

A total of 2125 patients with HCM were enrolled in this study. Among these, data from 1453 patients with measurable APM-IVS distances were analyzed. Of the 1453 patients, 596 had MVO, while 857 did not exhibit MVO. Multivariate logistic regression analyses showed that APM-IVS distance was an independent indicator of MVO (adjusted odds ratio [95% confidence interval (CI)]: 0.487 [0.448–0.529]). The APM-IVS distance demonstrated the highest diagnostic accuracy in identifying MVO, exhibiting an area under the receiver operating characteristic curve of 0.949 (95% CI: 0.937–0.960). The presence of a smaller APM-IVS distance was correlated with increased incidence of left ventricular apical aneurysm and MVO, elevated levels of N-terminal pro brain natriuretic peptide, as well as higher New York Heart Association functional class. Among those with MVO, 198 patients underwent surgical myectomy and were followed up after a median time of 12 months. APM-IVS distance increased from 7.6±2.2 mm to 18.9±4.9 mm, and the peak mid-ventricular gradient decreased from 50 mm Hg (36–57 mmHg) to 3 mmHg (3–7 mmHg) at follow-up.

A small APM-IVS distance was associated with MVO, which was alleviated after myectomy following an increase in APM-IVS distance.

Hypertrophic Cardiomyopathy

Mid-ventricular Obstruction

Papillary Muscle

Interventricular septum

Echocardiography

2025 Published by Elsevier Inc. on behalf of the American Society of Echocardiography.