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Cardiac-Resynchronization Therapy in Heart Failure with a Narrow QRS Complex To the Editor: Ruschitzka et al. (Oct. 10 issue)1 report that in the Echocardiography Guided Cardiac Resynchronization Therapy (EchoCRT) study involving patients with systolic heart failure and a QRS duration of less than 130 msec, cardiacresynchronization therapy (CRT) failed to reduce the rate of death from any cause or hospitalization for heart failure. The authors, however, fail to present data elaborating whether CRT improved the measured variables of mechanical dyssynchrony at follow-up. This is especially relevant, because mechanical dyssynchrony represents the culmination of multiple disease processes, including electrical dyssynchrony, myocardial stress, and myocardial fibrosis.2 CRT primarily improves electrical dyssynchrony but does not uniformly decrease morbidity and mortality, even in patients with a wide QRS complex.3 Without the above data, it is unclear whether the failure of CRT was secondary to persistent mechanical dyssynchrony or other causes. Prabhpreet Singh, M.B., B.S., M.D. University of Pittsburgh Pittsburgh, PA
[email protected]
Jeffrey J. Goldberger, M.D. Northwestern University Chicago, IL Dr. Goldberger reports receiving honoraria, unrestricted educational grants, or both from Boston Scientific, Medtronic, and St. Jude Medical. No other potential conflict of interest relevant to this letter was reported. 1. Kass DA, Chen CH, Curry C, et al. Improved left ventricular
No potential conflict of interest relevant to this letter was reported. 1. Ruschitzka F, Abraham WT, Singh JP, et al. Cardiac-resyn-
chronization therapy in heart failure with a narrow QRS complex. N Engl J Med 2013;369:1395-405. 2. Cheng A, Helm RH, Abraham TP. Pathophysiological mechanisms underlying ventricular dyssynchrony. Europace 2009;11: Suppl 5:v10-v14. 3. Kass DA. Predicting cardiac resynchronization response by QRS duration: the long and short of it. J Am Coll Cardiol 2003; 42:2125-7. DOI: 10.1056/NEJMc1315288
To the Editor: Ruschitzka et al. report harm from CRT in patients with a QRS duration of less than 130 msec and echocardiographic evidence of left ventricular dyssynchrony. Several trials have failed to show a benefit of CRT in patients with dyssynchony without QRS prolongation. Initial physiological studies involving patients with left bundle-branch block showed that left ventricular pacing was as good as or even better than biventricular pacing.1,2 In addition, multiple
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studies3,4 have shown an adverse effect of right ventricular pacing, which reduces left ventricular function.5 It is notable that the combination of left and right ventricular pacing in patients with left bundle-branch block results in clinical improvement, whereas this same combination in patients without it can cause harm. Perhaps left bundle-branch block protects patients from the detrimental effects of right ventricular pacing owing to the similar underlying conduction abnormalities. In contrast, patients without left bundle-branch block are exposed to the detrimental effect of right ventricular pacing, which overwhelms any potential benefit of left ventricular pacing. Better understanding of the underlying physiological effects of CRT is needed before applying it clinically in untested populations.
mechanics from acute VDD pacing in patients with dilated cardiomyopathy and ventricular conduction delay. Circulation 1999; 99:1567-73. 2. Blanc JJ, Etienne Y, Gilard M, et al. Evaluation of different ventricular pacing sites in patients with severe heart failure: results of an acute hemodynamic study. Circulation 1997;96: 3273-7. 3. Wilkoff BL, Cook JR, Epstein AE, et al. Dual-chamber pacing or ventricular backup pacing in patients with an implantable defibrillator: the Dual Chamber and VVI Implantable Defibrilla tor (DAVID) Trial. JAMA 2002;288:3115-23. 4. Sweeney MO, Hellkamp AS, Ellenbogen KA, et al. Adverse effect of ventricular pacing on heart failure and atrial fibrillation among patients with normal baseline QRS duration in a clinical trial of pacemaker therapy for sinus node dysfunction. Cir culation 2003;107:2932-7. 5. Nahlawi M, Waligora M, Spies SM, Bonow RO, Kadish AH, Goldberger JJ. Left ventricular function during and after right ventricular pacing. J Am Coll Cardiol 2004;44:1883-8. DOI: 10.1056/NEJMc1315288
To the Editor: Ruschitzka et al. found that in patients with systolic heart failure and a QRS duration of less than 130 msec, CRT did not reduce the rate of hospitalization for heart failure and may increase mortality. In patients with atrial fi-
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correspondence
brillation and an uncontrolled heart rate, atrioventricular-junction ablation and permanent pacing from the right ventricular apex provide efficient ventricular-rate control and may improve symptoms. However, left ventricular dyssynchrony can be induced in about 50% of patients and may be followed by worsening of heart failure. Recent guidelines recommend CRT for patients with a reduced left ventricular ejection fraction and rapid atrial fibrillation who are eligible for atrioventricular-junction ablation, because CRT may prevent dyssynchrony induced by right ventricular pacing.1 The results of the EchoCRT study question this strategy in patients with a narrow QRS complex and highlight the need for a trial evaluating properly the effects of atrioventricularjunction ablation and CRT on hard clinical end points.
aforementioned study. Using apical rocking1 and the extent of myocardial scar as determined by echocardiography as criteria, we identified dyssynchrony that was potentially treatable by CRT in only 7% of 258 patients. We see two possible explanations for this discrepancy: a strong referral bias in the patient population enrolled in the study or the use of echocardiographic selection criteria that were not sufficiently specific for CRT-treatable dyssynchrony patterns. A reanalysis of the study data using more specific selection criteria2,3 may therefore be of interest.
Laurent Fauchier, M.D.
University of Belgrade Belgrade, Serbia
Université François Rabelais Tours, France
[email protected]
Jens-Uwe Voigt, M.D., Ph.D. Razvan-Olimpiu Mada, M.D. Catholic University Leuven Leuven, Belgium
[email protected]
Ivan Stankovic, M.D.
No potential conflict of interest relevant to this letter was reported.
Nicolas Clementy, M.D.
1. Voigt JU, Schneider TM, Korder S, et al. Apical transverse
Centre Hospitalier Universitaire Trousseau Tours, France
Anne Brunet-Bernard, M.D. Université François Rabelais Tours, France No potential conflict of interest relevant to this letter was reported. 1. Brignole M, Auricchio A, Baron-Esquivias G, et al. 2013 ESC
guidelines on cardiac pacing and cardiac resynchronization therapy: the Task Force on Cardiac Pacing and Resynchronization Therapy of the European Society of Cardiology (ESC): developed in collaboration with the European Heart Rhythm Association (EHRA). Eur Heart J 2013;34:2281-329. DOI: 10.1056/NEJMc1315288
To the Editor: We agree with the hypothesis of the EchoCRT study that treatable dyssynchrony may exist in patients with a narrow QRS complex, although the study showed no benefit of CRT in this population. We assume that the very high number of patients identified by echocardiography as having ventricular dyssynchrony (855 of 1680 patients [51%]) contributed to this outcome. We have therefore reviewed echocardiographic examinations performed at the University Hospital Leuven during the past 3 years in search of patients who met the inclusion criteria of the
motion as surrogate parameter to determine regional left ventricular function inhomogeneities: a new, integrative approach to left ventricular asynchrony assessment. Eur Heart J 2009;30: 959-68. 2. Parsai C, Bijnens B, Sutherland GR, et al. Toward understanding response to cardiac resynchronization therapy: left ventricular dyssynchrony is only one of multiple mechanisms. Eur Heart J 2009;30:940-9. 3. Stankovic I, Aarones M, Smith HJ, et al. Dynamic relationship of left-ventricular dyssynchrony and contractile reserve in patients undergoing cardiac resynchronization therapy. Eur Heart J 2013;35:48-55. DOI: 10.1056/NEJMc1315288
To the Editor: The findings of the EchoCRT study corroborated the role of QRS duration as the primary predictor of response to CRT. How ever, the authors should have provided more data on methodologic issues regarding measurements of QRS duration as well as rates of agreement between individual site investigators and personnel at the electrocardiographic (ECG) core laboratory, patient eligibility for study inclusion (QRS duration
