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Cardiac Resynchronization Therapy and Heart Failure
Abstract & Commentary
By Harold L. Karpman, MD, FACC, FACP, Clinical Professor of Medicine, UCLA School of Medicine. Dr. Karpman reports no financial relationship to this field of study.
Synopsis: CRT combined with ICD decreased the risk of heart failure events in relatively asymptomatic patients with low ejection fractions and wide QRS complexes on their EKGs.
Source: Moss AJ, et al. Cardiac-resynchronization therapy for the prevention of heart-failure events. N Engl J Med 2009;361:1329-1338.
Implantation of an automatic cardioverter-defibrillator (ICD) improves survival and reduces the risk of sudden death in appropriately selected patients with cardiac disease; however, ICD therapy is often associated with increased risk of first and recurrent heart failure events.1-4 Cardiac resynchronization therapy (CRT) with biventricular pacing has been shown to be an effective adjunctive therapeutic addition to pharmacologic management in reducing the rate of hospitalization in symptomatic patients with advanced heart failure symptoms, an ejection fraction of 35% or less, and an intraventricular conduction delay of 120 msec or more.5-7 Results from a previously published study suggested that CRT improves cardiac structure and function through reverse left ventricular remodeling.8
Moss and his colleagues designed a trial to determine whether CRT with biventricular pacing would reduce the risk of death or heart failure events in patients with mild cardiac symptoms, a reduced ejection fraction, and wide QRS complexes. They enrolled 1820 patients with ischemic or non-ischemic cardiomyopathy with an ejection fraction of 30% or less, a QRS duration of 130 msec or more, and New York Heart Association class I or II symptoms. Echocardiographic studies demonstrated substantial reductions in left ventricular end-diastolic and end-systolic volumes with improvement in the ejection fraction 1 year after the initiation of CRT-ICD therapy. They concluded that there was a 41% reduction in the risk of heart failure events, a significant reduction in left ventricular volumes, and improvement in the ejection fraction in patients treated with CRT; however, CRT did not reduce the overall risk of death.
Moss and his group demonstrated that the use of CRTcombined with an ICD in asymptomatic or mildly symptomatic patients with heart disease, widened QRS complexes, and a reduced ejection fraction was associated with a 34% reduction in the risk of death or heart failure events as compared with patients who received ICD therapy alone. The observed benefit was driven by a highly significant 41% reduction in the risk of heart failure events, a finding that was evident primarily in the subgroup of patients with a QRS duration of 150 msecor more. CRT therapy was found to be associated with improvement in composite heart failure score during 12 months of follow-up in 419 patients with resynchronization turned on in the CRT devices as compared with 191 patients with resynchronization turned off in the CRTdevices.8 In summary, CRT-ICD appears to significantly reduce the risk of heart failure events in vulnerable patients with ischemic or non-ischemic heart disease who have reduced ejection fractions and wide QRS complexes on their resting EKG, even if they have only minimal heart failure symptoms.
1. Bardy GH, et al. Amiodarone or an implantable cardioverter-defibrillator for congestive heart failure. N Engl J Med 2005;352:225-237; Erratum in: N Engl J Med 2005;352:2146.
2. Moss AJ, et al. Improved survival with an implanted defibrillator in patients with coronary disease at high risk for ventricular arrhythmia. Multicenter Automatic Defibrillator Implantation Trial Investigators. N Engl J Med 1996;335:1933-1940.
3. Moss AJ, at al. Prophylactic implantation of a defibrillator in patients with myocardial infarction and reduced ejection fraction. N Engl J Med 2002;346: 877-883.
4. Goldenberg I, et al. Causes and consequences of heart failure after prophylactic implantation of a defibrillator in the multicenter automatic defibrillator implantation Trial II. Circulation 2006;113:2810-2817.
5. Bristow MR, et al. Cardiac-resynchronization therapy with or without an implantable defibrillator in advanced chronic heart failure. N Engl J Med 2004;350:2140-2150.
6. Cleland JG, et al. The effect of cardiac resynchronization on morbidity and mortality in heart failure. N Engl J Med 2005;352:1539-1549.
7. Epstein AE, et al. ACC/AHA/HRS 2008 Guidelines for Device-Based Therapy of Cardiac Rhythm Abnormalities: A report of the American College of Cardiology/ American Heart Association Task Force on Practice Guidelines: Developed in collaboration with the American Association for Thoracic Surgery and Society of Thoracic Surgeons. Circulation 2008; 117:e350-e408; Erratum in: Circulation 2009;120: e34-e35.
8. Linde C, et al. Randomized trial of cardiac resynchronization in mildly symptomatic heart failure patients and in asymptomatic patients with left ventricular dysfunction and previous heart failure symptoms. J Am Coll Cardiol 2008;52:1834-1843.