The Impact of Myocardial Viability on the Clinical Outcome of Cardiac Resynchronization Therapy


  • Lucie Riedlbauchová, M.D., Ph.D., and Lucie Popová, M.D., worked as visiting fellows from the Institute for Clinical and Experimental Medicine in Prague, Czech Republic. Funds for their stays were provided by the Modern Treatment of Arrhythmia Endowment Fund in Prague and by the Czech Society of Cardiology (through a travel grant for young physicians).

  • Dr. Brunken reports receiving a research grant from Bracco Diagnostics. Dr. Burkhardt reports serving as a consultant and receiving speaker's fees and honoraria from St. Jude Medical. Dr. Martin is a PI for the Pegasus CRT clinical trial funded by Boston Scientific, and reports serving on the CRM Advisory Board and receiving honoraria from Medtronic and speaker's bureau fees from St. Jude Medical. Dr. Wilkoff reports serving on the advisory boards of Medtronic, St. Jude Medical, and Boston Scientific and has received honoraria from them. Dr. Grimm has received research support from Medtronic and honoraria from GE, Medtronic and St. Jude Medical. He holds a patent on ultrasound technology relative to CRT. Dr. Natale reports research support from St. Jude Medical and speaker's bureau fees from Medtronic, Boston Scientific, St. Jude Medical, and Biosense Webster.

  • Manuscript received 31 March 2008; Revised manuscript received 2 June 2008; Accepted for publication 3 June 2008.

Address for correspondence: Lucie Riedlbauchová, M.D., Ph.D., Department of Cardiology, Institute for Clinical and Experimental Medicine, Vídeňská 1958/9, 14021 Prague 4, Czech Republic. Fax: 00-420-261-362-985; E-mail:


Introduction: Around 30% of patients do not respond to cardiac resynchronization therapy (CRT). Nonischemic cardiomyopathy has been identified as an independent predictor of response to CRT, probably due to the absence of compact scar.

Methods and results: The relationship between cardiac scar, ischemia, and hibernation (both at the left-ventricular pacing site and as a total burden) and response to CRT was studied in patients with ischemic cardiomyopathy using the perfusion-viability positron emission tomography (PET) test.

Sixty-six patients with ischemic cardiomyopathy and traditional criteria for CRT were included. All patients underwent PET scan prior to CRT. Using PET, the amount and location of scarred, ischemic, and hibernating myocardium were characterized. No revascularization was indicated. Responders were defined by an improvement of left-ventricular ejection fraction (LVEF) ≥ 5% and/or New York Heart Association (NYHA) class ≥ 1 degree.

During a mean follow-up of 26.2 ± 22.2 months, there was a significant improvement in NYHA class and reverse remodeling in patients with the LV lead inserted remotely from the scar. However, reverse remodeling of a similar degree was present also in patients with extensive scarring including the lateral wall. The presence of ischemia, hibernation, or nontransmural scar at the pacing-site did not significantly modify the outcome of CRT as compared with viable myocardium. There were only 38% of CRT-nonresponders. Neither the extent of scar, ischemia, hibernation, or viability predicted outcome or mortality. Twenty patients died during the follow-up, one patient underwent heart transplant.

Conclusions: At follow-up, response to CRT is observed regardless of the presence of extensive scarring. Left ventricular (LV) pacing at sites with ischemia, hibernation, or nontransmural scar does not appear to modify the effect of CRT as compared to viable tissue.