Copyright © 2003 by the European Society of Cardiology.
Clinical research
Walk test at increased levels of heart rate in patients with dual-chamber pacemaker and with normal or depressed left ventricular function
a Department of Biomorphological and Functional Sciences, University Federico II, Napoli, Italy
b Clinical Medicine, Cardiovascular and Immunological Sciences, University Federico II, Napoli, Italy
c IRCCS Neuromed, Pozzilli, Italy
* Correspondence to: Alberto Cuocolo, MD, Department of Biomorphological and Functional Sciences, University Federico II, Via Pansini 5-80131 Napoli, Italy. Tel: +39 081 7462044; fax: +39 081 5457081
E-mail address: cuocolo{at}unina.it
Received 7 April 2003; revised 2 September 2003; accepted 11 September 2003
Abstract
Background This study focuses the role of heart rate on cardiac output (CO) at rest and during walk test in patients with dual-chamber pacemaker and depressed or normal left ventricular (LV) function.
Methods and results In nine patients with ejection fraction (EF) <50% (group A) and in seven with EF 50% (group B) haemodynamics were assessed at rest and during three randomized 6-min walk tests at fixed rate of 70, 90, and 110beats·min–1. All patients had dual-chamber pacemaker implanted for complete heart block. Left ventricular function was monitored by a radionuclide system. In group A, with increasing pacing-rate from 70 to 110beats·min–1, CO did not change both at rest and during walk, whereas end-systolic volume (ESV) increased (P<0.05) and stroke volume (SV) decreased from 68±6 to 47±9ml at rest (P<0.0001) and from 112±21 to 76±17ml during walk (P<0.005). In group B, with increasing pacing-rate, CO rose from 6.4±0.7 to 9.1±1.6l·min–1at rest (P<0.001) and from 10±1.5 to 14.1±2.2l·min-1during walk (P<0.0001), with no change in ESV and SV.
Conclusions Increasing heart rate in presence of ventricular asynchrony induced by dual-chamber pacing has negative effect on cardiac contractility and does not improve CO at rest or during physical activity in patients with depressed LV function as occurs in those with normal function.
Key Words: Heart rate • Walk test • Dual-chamber pacing
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