A prospective evaluation of cardiovascular magnetic resonance measures of dyssynchrony in the prediction of response to cardiac resynchronization therapy.

Manav Sohal,Steven Niederer,Wenzhe Shi,Matthew Ginks,Gerald Carr-White,Simon G Duckett,Anoop Shetty,Sebastian Kozerke,Reza Razavi,Eva Sammut,Daniel Rueckert,Nic Smith,Sebastien Ourselin,Christopher Aldo Rinaldi,Xiahai Zhuang

doi:10.1186/s12968-014-0058-0

Abstract

BackgroundMany patients with electrical dyssynchrony who undergo cardiac resynchronization therapy (CRT) do not obtain substantial benefit. Assessing mechanical dyssynchrony may improve patient selection. Results from studies using echocardiographic imaging to measure dyssynchrony have ultimately proved disappointing. We sought to evaluate cardiac motion in patients with heart failure and electrical dyssynchrony using cardiovascular magnetic resonance (CMR). We developed a framework for comparing measures of myocardial mechanics and evaluated how well they predicted response to CRT.MethodsCMR was performed at 1.5 Tesla prior to CRT. Steady-state free precession (SSFP) cine images and complementary modulation of magnetization (CSPAMM) tagged cine images were acquired. Images were processed using a novel framework to extract regional ventricular volume-change, thickening and deformation fields (strain). A systolic dyssynchrony index (SDI) for all parameters within a 16-segment model of the ventricle was computed with high SDI denoting more dyssynchrony. Once identified, the optimal measure was applied to a second patient population to determine its utility as a predictor of CRT response compared to current accepted predictors (QRS duration, LBBB morphology and scar burden).ResultsForty-four patients were recruited in the first phase (91% male, 63.3 ± 14.1 years; 80% NYHA class III) with mean QRSd 154 ± 24 ms. Twenty-one out of 44 (48%) patients showed reverse remodelling (RR) with a decrease in end systolic volume (ESV) ≥ 15% at 6 months. Volume-change SDI was the strongest predictor of RR (PR 5.67; 95% CI 1.95-16.5; P = 0.003). SDI derived from myocardial strain was least predictive. Volume-change SDI was applied as a predictor of RR to a second population of 50 patients (70% male, mean age 68.6 ± 12.2 years, 76% NYHA class III) with mean QRSd 146 ± 21 ms. When compared to QRSd, LBBB morphology and scar burden, volume-change SDI was the only statistically significant predictor of RR in this group.ConclusionA systolic dyssynchrony index derived from volume-change is a highly reproducible measurement that can be derived from routinely acquired SSFP cine images and predicts RR following CRT whilst an SDI of regional strain does not.

Highlights

Many patients with electrical dyssynchrony who undergo cardiac resynchronization therapy (CRT) do not obtain substantial benefit
A systolic dyssynchrony index derived from volume-change is a highly reproducible measurement that can be derived from routinely acquired Steady-state free precession (SSFP) cine images and predicts reverse remodeling (RR) following CRT whilst an SDI of regional strain does not
The phase 2 cohort had significantly more females (30% vs 9%: P = 0.01). Both groups were matched in terms of etiology, number of patients with scar, baseline New York Heart Association (NYHA) class, medical therapy and baseline left ventricular (LV) volumes derived from 2D echocardiography

Summary

Introduction

Many patients with electrical dyssynchrony who undergo cardiac resynchronization therapy (CRT) do not obtain substantial benefit. Cardiac resynchronization therapy (CRT) is established as an effective treatment in selected heart failure patients with evidence of dyssynchrony, improving both morbidity and mortality [1]. The mechanics of myocardial contraction and relaxation are complex with multiple methods currently used to investigate dyssynchrony This has led to extensive, but unsuccessful, work in the field of echocardiography to develop imaging based mechanical dyssynchrony measures that improve patient selection [3]. It is not entirely clear if the concept of mechanical dyssynchrony is flawed or if the most widely used method of measuring it (echocardiography) is the limiting factor. Newer echocardiographic techniques that use speckle tracking to measure strain have been advocated as better methods of measuring mechanical dysynchrony and CRT response but this has yet to be demonstrated in a multi-center setting [6,7]

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