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Imaging for Planning of Cardiac Resynchronization Therapy

Bobak Heydari, MD^_*, Michael Jerosch-Herold, PhD, Raymond Y. Kwong, MD, MPH^_*,_*

^_* Cardiovascular Division, Department of Medicine, Brigham and Women's Hospital, Boston, Massachusetts
Department of Radiology, Brigham and Women's Hospital, Boston, Massachusetts

^_* Reprint requests and correspondence: Dr. Raymond Y. Kwong, Brigham and Women's Hospital, Harvard Medical School, 75 Francis Street, Boston, Massachusetts 02115 (Email: rykwong{at}partners.org).

Cardiac resynchronization therapy (CRT) is a novel therapy for patients with refractory heart failure (HF). Large clinical trials evaluating CRT have demonstrated significant improvements in cardiac survival, decreases in recurrent HF hospitalization, and improvements in indexes of quality of life. Although numerous mechanisms are involved in CRT's therapeutic effects, correction of both interventricular and intraventricular mechanical dyssynchrony has been postulated as the key mechanism. To date, most large randomized controlled trials evaluating CRT have identified dyssynchronous patients on the basis of prolongation of the QRS complex from the baseline electrocardiogram. Concerns have been raised regarding the use of this measure for patient selection, stemming from a significant 30% to 40% nonresponse rate to CRT. Because of the cost and invasive nature of CRT, optimal patient selection for this therapy has become a priority for HF specialists and electrophysiologists. Cardiac imaging modalities have attempted to fulfill this need to improve patient selection by identifying mechanical dyssynchrony. Although early echocardiographic studies reported promising results, more recent larger scale studies have curtailed this enthusiasm, with a lack of established selection criteria for CRT in the current practice guidelines. This review summarizes the evidence to date and the potential role of imaging modalities in the selection and care of patients with HF referred for CRT.

Key Words: cardiac computed tomography • cardiac magnetic resonance imaging • cardiac resynchronization therapy • noninvasive imaging • radionuclide imaging

Abbreviations and Acronyms   CCT = cardiac computed tomography   CMR = cardiac magnetic resonance   CRT = cardiac resynchronization therapy   DENSE = displacement encoding with stimulated echoes   GMPS = gated myocardial perfusion single-photon emission computed tomography   HF = heart failure   LV = left ventricular   LVEF = left ventricular ejection fraction   MRI = magnetic resonance imaging   RT3D = real-time 3-dimensional   SENC = strain-encoded magnetic resonance imaging   TDI = tissue Doppler imaging