State-of-the-Art Paper
Cardiac Resynchronization Therapy: Part 1—Issues Before Device Implantation

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Cardiac resynchronization therapy (CRT) has been used extensively over the last years in the therapeutic management of patients with end-stage heart failure. Data from 4,017 patients have been published in eight large, randomized trials on CRT. Improvement in clinical end points (symptoms, exercise capacity, quality of life) and echocardiographic end points (systolic function, left ventricular size, mitral regurgitation) have been reported after CRT, with a reduction in hospitalizations for decompensated heart failure and an improvement in survival. However, individual results vary, and 20% to 30% of patients do not respond to CRT. At present, the selection criteria include severe heart failure (New York Heart Association functional class III or IV), left ventricular ejection fraction <35%, and wide QRS complex (>120 ms). Assessment of inter- and particularly intraventricular dyssynchrony as provided by echocardiography (predominantly tissue Doppler imaging techniques) may allow improved identification of potential responders to CRT. In this review a summary of the clinical and echocardiographic results of the large, randomized trials is provided, followed by an extensive overview on the currently available echocardiographic techniques for assessment of LV dyssynchrony. In addition, the value of LV scar tissue and venous anatomy for the selection of potential candidates for CRT are discussed.

Abbreviations and Acronyms

CMR
cardiovascular magnetic resonance
CRT
cardiac resynchronization therapy
LV
left ventricle/ventricular
LVEF
left ventricular ejection fraction
MIRACLE
Multicenter InSync Randomized Clinical Evaluation study
MSCT
multislice computed tomography
NYHA
New York Heart Association
TDI
tissue Doppler imaging
TSI
tissue synchronization imaging

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Dr. Abraham receives honoraria from GE, Guidant, Medtronic, St. Jude and receives research support from Guidant; Dr. Barold received lecture fees from receives research support from Guidant; Dr. Barold received lecture fees from Medtronic; Dr. Breithardt has been a consultant for Medtronic and Guidant and has research affiliations with Medtronic, Guidant, and GE Vingmed; Dr. Hayes is on the advisory board of Guidant Inc. and has been a speaker for Guidant Inc., Medtronic Inc., St. Jude Medical, and ELA Medical, and has received royalties from Blackwell Futura; Dr. Gorcsan received research grant support from GE, Toshiba, Siemens, Medtronic, and St. Jude; Dr. Kass has been a consultant for Guidant Inc.; Dr. Mark has been a consultant and received grants from Medtronic, Inc. Dr. Monaghan has received support from Philips, GE, Siemens, Guidant, Medtronic, and Accusphere; Dr. Schalij is on the advisory board of Guidant and has received research grants from Medtronic, Guidant, and St. Jude; Dr. Stellbrink is a sponsored investigator for Guidant, Medtronic, St. Jude, and Biotronik and is also an advisor to Guidant and Biotronik; Dr. Nihoyannopoulos received research grants and consultant fees from Medtronic.