Numerical Simulation Study on the Mechanism of Formation of Apical Aneurysm in Hypertrophic Cardiomyopathy With Midventricular Obstruction

Transapical beating-heart septal myectomy for hypertrophic cardiomyopathy patients with midventricular obstruction

Background

We developed a novel minimally invasive transapical beating-heart septal myectomy (TA-BSM) procedure for patients with midventricular obstruction (MVO), without the aid of cardiopulmonary bypass. This study aims to describe the TA-BSM procedure for the relief of MVO and to detail the clinical outcomes in these patients.

Methods

Sixty-one patients receiving TA-BSM for MVO were included: isolated MVO (n = 12) and combined MVO and subaortic obstruction (n = 49). We reviewed the electronic medical record to collect information on preoperative, intraoperative, and postoperative parameters.

Results

The intraventricular pressure gradient after the resection was largely attenuated. On the catheter measurement, the median resting and provoked gradient decreased by 29.0 and 71.0 mm Hg, respectively. Likewise, the resting intraventricular gradient was successfully reduced from 58.0 to 11.0 mm Hg, and the maximal intraventricular gradient was reduced from 88.0 to 20.0 mm Hg at 6 months follow-up. In addition, all patients showed significantly improved MR and 37 of 42 patients with preoperative MR grade ≥2+ showed MR grade ≤1+ after TA-BSM. During the follow-up, no death was observed and no one had HCM-related rehospitalization. All patients reported improvement in symptoms and the mean New York Heart Association class improved from 3.0 (IQR, 3.0-3.0) preoperatively to 1.0 (IQR, 1.0-1.0) at 6 months follow-up.

Conclusions

The TA-BSM procedure is a valuable therapy to relieve MVO, improving hemodynamics and providing satisfactory clinical outcomes. The procedure can also preserve favorable outcomes for patients with MVO and concomitant subaortic obstruction.

Diagnosis and Clinical Implication of Left Ventricular Aneurysm in Hypertrophic Cardiomyopathy

Hypertrophic cardiomyopathy (HCM) is a genetic disease with heterogeneous clinical presentation and prognosis. Within the broad phenotypic expression of HCM, there is a subgroup of patients with a left ventricular (LV) apical aneurysm, which has an estimated prevalence between 2% and 5%. LV apical aneurysm is characterized by an area of apical dyskinesis or akinesis, often associated with regional scarring. To date, the most accepted pathomechanism of this complication is, in absence of coronary artery disease, the high systolic intra-aneurysmal pressure, which, combined with impaired diastolic perfusion from lower stroke volume, results in supply-demand ischemia and myocardial injury. Apical aneurysm is increasingly recognized as a poor prognostic marker; however, the efficacy of prophylactic anticoagulation and/or intracardiac cardioverted defibrillator (ICD) in improving morbidity and mortality is not yet clearly demonstrated. This review aims to elucidate the mechanism, diagnosis and clinical implication of LV aneurysm in patients with HCM.

Computational analysis of ventricular mechanics in hypertrophic cardiomyopathy patients

Hypertrophic cardiomyopathy (HCM) is a genetic heart disease that is associated with many pathological features, such as a reduction in global longitudinal strain (GLS), myofiber disarray and hypertrophy. The effects of these features on left ventricle (LV) function are, however, not clear in two phenotypes of HCM, namely, obstructive and non-obstructive. To address this issue, we developed patient-specific computational models of the LV using clinical measurements from 2 female HCM patients and a control subject. Left ventricular mechanics was described using an active stress formulation and myofiber disarray was described using a structural tensor in the constitutive models. Unloaded LV configuration for each subject was first determined from their respective end-diastole LV geometries segmented from the cardiac magnetic resonance images, and an empirical single-beat estimation of the end-diastolic pressure volume relationship. The LV was then connected to a closed-loop circulatory model and calibrated using the clinically measured LV pressure and volume waveforms, peak GLS and blood pressure. Without consideration of myofiber disarray, peak myofiber tension was found to be lowest in the obstructive HCM subject (60 kPa), followed by the non-obstructive subject (242 kPa) and the control subject (375 kPa). With increasing myofiber disarray, we found that peak tension has to increase in the HCM models to match the clinical measurements. In the obstructive HCM patient, however, peak tension was still depressed (cf. normal subject) at the largest degree of myofiber disarray found in the clinic. The computational modeling workflow proposed here can be used in future studies with more HCM patient data.