Cardiac resynchronization therapy

Explanation of Cardiac Resynchronization Therapy and Its Role in Treating AIHD... 

A series of pilot studies began with multisite pacing for patients with heart failure and dilated cardiomyopathy in the early 1990s [52, 105-111]. An improvement in LV function and symptoms of heart failure were demonstrated. This provided the interest in biventricular pacing for heart failure. The term cardiac resynchronization therapy was coined to refer to pacing therapies that attempt to enhance cardiac performance by using pacing to correct electrical conduction abnormalities in the heart. The most common form of this therapy is atrial-synchronous... 

Table 4.1 Entry criteria in randomized trials of cardiac resynchronization therapy...

However, the long-term effects of cardiac resynchronization therapy (CRT) on morbidity and mortality were not known. Two clinical trials have established the morbidity and mortality effects of CRT. The COMPANION trial was a three armed trial, testing optimal medical therapy (OPT) against OPT plus CRT by a pacemaker or a OPT plus CRT by an implantable cardioverter-defibrillator (CRT-D) [118]. In this study, patients were enrolled prior to... 

Fig. 4.3 Survival in the long-term randomized trials of CRT. In Panel A, the survival in the COMPANION trial was trended to improve by 24% in the cardiac resynchronization therapy (CRT) group P = 0.059), but improved by 36% with CRT with ICD capability (CRT-D). Panel B shows the mortality results from the CARE-HF study. CRT reduced mortality by 36% with a longer follow-up than the COMPANION trial. Note that in both studies, the survival benefit CRT appears to increase with time...

Auricchio A, Kloss M, Trautmann SI, Rodner S, Klein H. Exercise performance following cardiac resynchronization therapy in patients with heart failure and ventricular conduction delay. Am. J. Cardiol. 2002 89 198-203. 

Notabartolo D, Merlino JD, Smith AL, et al. Usefulness of the peak velocity difference by tissue Doppler imaging technique as an effective predictor of response to cardiac resynchronization therapy. Am. J. Cardiol. 2004 94 817-20. 

Sogaard P, Egeblad H, Kim WY, et al. Tissue Doppler imaging predicts improved systolic performance and reversed left ventricular remodeling during long-term cardiac resynchronization therapy. J. Am. Coll. Cardiol. 2002 40 723-30. 

Kanzaki H, Bazaz R, Schwartzman D, Dohi K, Sade LE, Gorcsan J, III. A mechanism for immediate reduction in mitral regurgitation after cardiac resynchronization therapy insights from mechanical activation strain mapping. J. Am. Coll. Cardiol. 2004 44 1619-25. 

Stellbrink C, Breithardt OA, Franke A, et al. Impact of cardiac resynchronization therapy using hemodynami-cally optimized pacing on left ventricular remodeling in patients with congestive heart failure and ventricular conduction disturbances, [see comment]. J. Am. Coll. Cardiol. 2001 38 1957-65. 

Bristow MR, Saxon LA, Boehmer J, et al. Cardiac-resynchronization therapy with or without an implantable defibrillator in advanced chronic heart failure, [see comment]. N. Engl. J. Med. 2004 350 2140-50. 

St John Sutton MG, Plappert T, Abraham WT, et al. Effect of cardiac resynchronization therapy on left ventricular size and function in chronic heart failure, [see comment]. Circulation 2003 107 1985-90. 

McAlister F, Ezekowitz J, Wiebe N, et al. Cardiac resynchronization therapy for congestive heart failure. Evid. Rep. Technol. Assess (Summ.) 2004 106 1-8. 

Molhoek SG, Van Erven L, Bootsma M, Steendijk P, Van Der Wall EE, Schalij MJ. QRS duration and shortening to predict clinical response to cardiac resynchronization therapy in patients with end-stage heart failure. Pacing Clin. Electrophysiol. 2004 27 308-13. 

Yu CM, Zhang Q, Fung JW, et al. A novel tool to assess systolic asynchrony and identify responders of cardiac resynchronization therapy by tissue synchronization imaging. J. Am. Coll. Cardiol. 2005 45 677-84. 

Gold MR, Auricchio A, Hummel JD, et al. Comparison of stimulation sites within left ventricular veins on the acute hemodynamic effects of cardiac resynchronization therapy. Heart Rhythm 2005 2 376-81. 

Recent studies demonstrate that cardiac resynchronization therapy (CRT) offers a promising approach to selected patients with chronic heart failure. Delayed electrical activation of the left ventricle, characterized on the ECG by a QRS duration that exceeds 120 ms, occurs in approximately one-third of patients with moderate to severe systolic heart failure. Since the left and right ventricles normally activate simultaneously, this delay results in asynchronous contraction of the left and right ventricles, which contributes to the hemodynamic abnormalities of this disorder. Implantation of a speciahzed biventricular pacemaker to restore synchronous activation of the ventricles can improve ventricular contraction and hemodynamics. Recent trials show improvements in exercise capacity, NYHA classification, quality of life, hemodynamic function, and hospitalizations. A device that combined CRT with an implantable cardioverter-defibrillator (ICD) improved survival in addition to functional status. CRT is currently indicated only in NYHA class ni-IV patients receiving optimal medical therapy (ACE inhibitors, diuretics, -blockers, and digoxin) and... 

Abraham WT, Hayes DL. Cardiac resynchronization therapy for heart failure. Circulation 2003 108 2596-2603. 

FIGURE 1.5 Summary of evidence supporting defibrillator implantation as stratified by ejection fraction and heart failure class in patients with ischemic cardiomyopathy (A) and nonischemic cardiomyopathy (B). For details of COMPANION trial, see Chapter 5. (CRT, cardiac resynchronization therapy EPS, electrophysiology study NYHA,New York Heart Association.)... 

Cardiac resynchronization therapy (CRT) for systolic congestive heart failure (CHF) represents a new paradigm in cardiology the use of an electrical therapy (cardiac pacing) to treat a mechanical problem. Multiple randomized clinical trials have proven that resynchronization therapy improves symptoms and functional status, increases quality of life, reduces hospitalizations, and prolongs survival in appropriately selected patients. As a result, this therapy has been quickly established as a standard treatment for patients with severe left ventricular dysfunction, moderate-to-severely symptomatic CHF despite optimal medical therapy, and prolonged QRS duration (1,2). 

FIGURE 5.1 Proportion of patients from MIRACLE (9) and CONTAK-CD (10) demonstrating varying levels of response in the New York Heart Association (NYHA) functional class with cardiac resynchronization therapy (CRT) hyper-responders improved by two functional classes, responders improved by one functional class, nonresponders had no improvement or deterioration in functional status. 

Higgins SL, Hummel JD, Niazi IK, et al. Cardiac resynchronization therapy for the treatment of heart failure in patients with intraventricular conduction delay and malignant ventricular tachyarrhythmias. J Am Coll Cardiol 2003 42 1454-9. 

Auricchio A, Stellbrink C, Butter C, et al. Clinical efficacy of cardiac resynchronization therapy using left ventricular pacing in heart failure patients stratified by severity of ventricular conduction delay. J Am Coll Cardiol 2003 42 2109-16. 

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