Abstract
Cardiac resynchronization therapy (CRT) is an established treatment for patients with symptomatic heart failure, severely impaired left ventricular (LV) systolic dysfunction and a wide (> 120 ms) complex. As with any other treatment, the response to CRT is variable. The degree of pre-implant mechanical dyssynchrony, scar burden and scar localization to the vicinity of the LV pacing stimulus are known to influence response and outcome. In addition to its recognized role in the assessment of LV structure and function as well as myocardial scar, cardiovascular magnetic resonance (CMR) can be used to quantify global and regional LV dyssynchrony. This review focuses on the role of CMR in the assessment of patients undergoing CRT, with emphasis on risk stratification and LV lead deployment.
Highlights
The first demonstration of a beneficial effect from cardiac resynchronization therapy (CRT) was provided by Cazeau et al who, in 1994, treated a 54 year old heart failure patient with four-chamber pacing [1]
The Multicenter Automatic Defibrillator Implantation Trial with Cardiac Resynchronization Therapy (MADIT-Cardiac resynchronization therapy (CRT)) trial has shown that compared with implantable cardioverter defibrillators (ICD) therapy alone, CRT-D therapy is associated with a dramatic reduction in the risk of heart-failure events in relatively asymptomatic
In a study patients with ischemic cardiomyopathy, a transmurality exceeding ≥ 51% in a left ventricular (LV) free wall scar was associated with a poor response rate (23%), compared with scars with < 51% transmurality (88%, p < 0.001), in terms of a composite clinical score
Summary
The first demonstration of a beneficial effect from cardiac resynchronization therapy (CRT) was provided by Cazeau et al who, in 1994, treated a 54 year old heart failure patient with four-chamber pacing [1]. Amongst the most complex is the absolute difference or the standard deviation of the time-to-peak systolic wall motion on tissue Doppler imaging in various (usually 12) myocardial segments [19] These and multiple other measures raised great expectations as predictors of response to and outcome of CRT in early single-centre studies [18,20,21]. In a study patients with ischemic cardiomyopathy, a transmurality exceeding ≥ 51% in a LV free wall scar was associated with a poor response rate (23%), compared with scars with < 51% transmurality (88%, p < 0.001), in terms of a composite clinical score (survival for 1 year with no heart failure hospitalizations, and; improvement by ≥ 1 NYHA classes or ≥ 25% 6-min walking distance). Further studies are needed to determine whether other CMRderived data, relating to coronary sinus anatomy, [124] mechanical activation, [125,34] perfusion and viability can be ‘fused’ with real-time CMR or conventional fluoroscopy to guide LV lead deployment
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