Published online before print October 12, 2009, doi: 10.1161/CIRCULATIONAHA.108.799395
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(Circulation. 2009;120:1687-1694.)
© 2009 American Heart Association, Inc.
Heart Failure |
Short-Term Hemodynamic Effects of Cardiac Resynchronization Therapy in Patients With Heart Failure, a Narrow QRS Duration, and No Dyssynchrony
From the University of Birmingham, Edgbaston, Birmingham, UK (L.K.W., K.P., F.L., T.T.P., M.F.); Ashford and St Peter’s Hospital, Chertsey, London, UK (S.E., V.P.); Royal Glamorgan Hospital, Llantrisant, Wales (R.A.B.); Bakken Research Centre, Maastricht, the Netherlands (B.S.); and Leiden University Medical Centre, Leiden, the Netherlands (P.S.).
Correspondence to Dr Lynne Williams, Department of Cardiovascular Medicine, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK. E-mail L.K.Williams{at}bham.ac.uk
Received June 24, 2008; accepted August 4, 2009.
Background— Cardiac resynchronization therapy produces both short-term hemodynamic and long-term symptomatic/mortality benefits in symptomatic heart failure patients with a QRS duration >120 ms. This is conventionally believed to be due principally to relief of dyssynchrony, although we recently showed that relief of external constraint to left ventricular filling may also play a role. In this study, we evaluated the short-term hemodynamic effects in symptomatic patients with a QRS duration <120 ms and no evidence of dyssynchrony on conventional criteria and assessed the effects on contractility and external constraint.
Methods and Results— Thirty heart failure patients (New York Heart Association class III/IV) with a left ventricular ejection fraction 
35% who were in sinus rhythm underwent pressure-volume studies at the time of pacemaker implantation. External constraint, left ventricular stroke work, dP/dtmax, and the slope of the preload recruitable stroke work relation were measured from the end-diastolic pressure-volume relation before and during delivery of biventricular and left ventricular pacing. The following changes were observed during delivery of cardiac resynchronization therapy: Cardiac output increased by 25±5% (P<0.05), absolute left ventricular stroke work increased by 26±5% (P<0.05), the slope of the preload recruitable stroke work relation increased by 51±15% (P<0.05), and dP/dtmax increased by 9±2% (P<0.05). External constraint was present in 15 patients and was completely abolished by both biventricular and left ventricular pacing (P<0.05).
Conclusion— Cardiac resynchronization therapy results in an improvement in short-term hemodynamic variables in patients with a QRS <120 ms related to both contractile improvement and relief of external constraint. These findings provide a potential physiological basis for cardiac resynchronization therapy in this patient population.
CLINICAL PERSPECTIVE
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  O. A. Smiseth, K. Russell, and E. W. Remme Pacing in Heart Failure Patients With Narrow QRS: Is There More to Gain Than Resynchronization? Circulation, October 27, 2009; 120(17): 1651 - 1653. [Full Text] [PDF]
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