Novel Insights Into RV Adaptation and Function in Hypoplastic Left Heart Syndrome Between the First 2 Stages of Surgical Palliation

Apr 06, 2011
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Authors:
Khoo NS, Smallhorn JF, Kaneko S, Myers K, Kutty S, Tham E.
Citation:
JACC Cardiovasc Imaging 2011;4:128-137.
Summary By:
Jennifer C. Romano, MD, FACC

Study Questions:

What are the changes in right ventricular (RV) function by speckle tracking imaging (STI) and magnetic resonance imaging (MRI) between the first two stages of surgical palliation for hypoplastic left heart syndrome (HLHS)?

Methods:

This was a prospective study of echocardiographic and MRI analysis of 20 HLHS patients (from two separate institutions) pre-Norwood and pre-bidirectional cavoplumonary anastomosis (BCPA) with comparison between stages and imaging modality. Two-dimensional echocardiography with STI (n = 20) and MRI (n = 12) was used to assess RV function. Measurements of ventricular function included: longitudinal/circumferential strain ration, reflecting changes in contraction pattern; post-systolic strain index (PSSI), a potential marker of myocardial ischemia; and mechanical dyssynchrony index (MDI).

Results:

Before BCP, RV function was reduced based on isovolumetric acceleration and strain rate and this paralleled an increase in PSSI. RV changes included a decreased longitudinal/circumferential strain ratio attaining a more left ventricular (LV)-like contraction pattern that was associated with decreased MDI (r = 0.65, p < 0.01), and MRI RV end-diastolic volume (r = 0.65, p < 0.05) and mass (r = 0.71, p < 0.01). Ventricular strain (r = -0.72, p < 0.01), strain rate (r = -0.85, p < 0.001), and MDI (r = -0.73, p < 0.01) correlated with MRI-derived RV ejection fraction.

Conclusions:

Ventricular strain, strain rate, and mechanical synchrony using STI are reproducible and correlate closely with RV function by MRI, providing a potential tool for monitoring ventricular function in HLHS. Adaptation of the ventricle to an LV-like contraction pattern with dominance of circumferential contraction was associated with better ventricular mechanics pre-BCPA as well as improved mechanical synchrony, and reduced size and mass. The evidence of increased post-systolic strain in HLHS may be associated with myocardial ischemia, which may be contributing to short- and long-term function.

Perspective:

Effectively assessing RV function in patients with HLHS is challenging due to the geometric configuration of the ventricle. This study provides insight into the differential benefit of various imaging modalities to better determine ventricular function and mechanical synchrony. Given the sedation requirements of MRI in infants and toddlers, the ability to utilize STI to obtain adequate assessments of RV function without anesthesia is of significant clinical importance.

Keywords: Ventricular Function, Right, Myocardial Ischemia, Hypoplastic Left Heart Syndrome, Heart Ventricles, Magnetic Resonance Imaging, Systole, Echocardiography


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