Quantitative assessment of hypertrophic obstructive cardiomyopathy with intraoperative three-dimensional epicardial and transesophageal echocardiography.

Background: Hypertrophic obstructive cardiomyopathy (HOCM), a subset of hypertrophic cardiomyopathy (HCM), is characterized by dynamic left ventricular outflow tract (LVOT) obstruction, often caused by systolic anterior motion (SAM) of the mitral valve and septal hypertrophy. Accurate intraoperative assessment of septal morphology, SAM distance, and LVOT area (LVOTa) is critical for surgical planning during septal myectomy. While transesophageal echocardiography (TEE), particularly with three-dimensional (3D) imaging, is the standard modality for evaluating these parameters, it may be contraindicated or suboptimal in select cases. Real-time 3D epicardial echocardiography (EE) offers an alternative imaging approach that allows direct visualization of the heart intraoperatively without esophageal instrumentation. This study investigates the utility of 3D EE compared to 3D TEE for quantitative assessment of septal left ventricular wall thickness (LVWT), SAM distance, and LVOTa in HOCM patients undergoing myectomy. The primary aim is to assess whether 3D EE and TEE measurements correlate and can be used interchangeably. A secondary aim is to compare 2D and 3D measurements by both modalities.

Methods: Perioperative data of 59 patients with HOCM were obtained by retrospective review in a tertiary care setting. 2D and 3D intraoperative transesophageal and EE studies were assessed performing multiple measurements relevant for myectomy. Demographic and clinical data were summarized with descriptive statistics, while the Altman-Bland method assessed the interchangeability of three-dimensional transesophageal and EE measurements. Inter- and intraobserver variabilities were evaluated using the Bland-Altman method and intraclass correlation coefficient.

Results: Off-line analysis of 3D data sets with Qlab Phillips was feasible in 79.7% of the patients. No significant differences were found between epicardial and transesophageal echocardiographic intraoperative measurements by 2D: septal LVWT (P=0.59), SAM distance (P=0.40) or LVOTa (P=0.22), or by 3D: septal LVWT (P=0.42), SAM distance (P=0.23) or LVOTa (P=0.38).

Conclusions: Intraoperative EE demonstrates equal potential utility in guiding HOCM patients when TEE is not an option or is contraindicated. These findings underscore the clinical significance of EE as a reliable alternative for image guidance during myectomy in HOCM patients, contributing to improved surgical outcomes.