Modern pacemaker modes and everyday activity

Sulke, Alfred Neil (1991) Modern pacemaker modes and everyday activity. University of Southampton, Doctoral Thesis.

Abstract

In recent years there has been a rapid evolution in pacemaker technology resulting in more `physiological' devices with increasingly complex features designed to improve patient wellbeing during everyday living. Studies described in this thesis assess, subjectively and objectively, the function of different rate response sensors, different programming parameters and different modern rate responsive pacing modes during everyday activity. The chronotropic response of patients with four types of single chamber (VVIR) pacemaker was adequate during treadmill exercise tests but poor during everyday activities involving burst and resting stress. Dual chamber devices were clearly superior during everyday activity. Programming and assessment of new and current rate adaptive devices should additionally use standardised daily activities to better simulate response during everyday activity. Holter monitor analysis of VVIR pacing during everyday activity showed that the known advantages of this mode over fixed rate (VVI) pacing result from increased rate pacing for less than 15% of the day. The effect of malprogramming of dual (DDDR), and single (VVIR) chamber rate responsive pacemakers reveals that patients find over-programming least acceptable but objective exercise tolerance is not significantly affected as long as some pacemaker rate response is available. The effect of different atrioventricular delay programming in DDDR mode shows that rate adaptive and shorter fixed settings are preferable to longer ones (250 ms). There was no difference in objective exercise tolerance but echocardiography revealed decreased stroke distance at 250 ms at high paced rates. Double blind crossover comparison of VVIR, DDIR, DDD and DDDR modes during out of hospital activity found that DDDR was most and VVIR least acceptable, with objective improvements detected in DDDR over all the remaining modes. Change in stroke volume detected by echo-Doppler proved predictive of benefit from dual chamber rate responsive pacing. Three echocardiographic techniques were compared to gated radionuclide ventriculography during assessment of modern pacing modes. Continuous wave Doppler proved most sensitive and reproducible in serial studies whilst nuclear scintigraphy failed to demonstrate beat to beat haemodynamic changes or to distinguish between different modes at rest or during exercise. The effect of upgrading apparently asymptomatic patients paced in VVI mode to DDD pacing has demonstrated the existence of a `subclinical' pacemaker syndrome in nearly 70% of such patients. This study suggests that DDD mode pacing should be used whenever possible. The increasing sophistication of modern pacemakers does result in improved patient wellbeing during everyday activity.

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