Pacemaker selection: time for a rethinking of complex pacing systems

The article by Musilli and Padeletti is a thought-provoking challenge to the widespread use of DDD pacing. They suggest that single-chamber devices, AAI and VVI, are a more rational choice in most cases of sinus node disease (SND) and AV block, respectively. The authors advocate VVI systems instead of DDD systems because of non-inferiority with regard to stroke and mortality, as shown by MOST, CTOPP, PASE, and UKPACE. However, in patients paced for a slower intrinsic rate, a significantly higher mortality has been reported using VVI vs. DDD systems.1 These studies also show that VVI pacing increases the risk of developing chronic atrial fibrillation (AF) by 20%. AF is the leading arrhythmia cause of hospitalization, increases the risk of stroke by five-fold, and doubles mortality,2 but the number needed to treat with a DDD system (CTOPP) to prevent AF is nine. MOST showed heart failure hospitalization reduction of 27% with DDD pacing. MOST and PASE show the incidence of pacemaker syndrome (PMS) to be about 25–33%, which occurred early and was resolved immediately by reprogramming to DDD mode.3 It is likely that the lower incidence of PMS reported in CTOPP is because reoperation rather than reprogramming was required biasing their results. If 30% of patients require an upgrade to the DDD mode early after implantation of a VVI system, the effects on patients' quality of life and healthcare costs will be marked. A recent meta-analysis showed that the cost difference between single and dual-chamber systems over 5 years is small—£700 more for dual-chamber devices.4 The authors suggest AAI systems, by reducing ventricular pacing, should be used instead of DDD systems in patients with SND because of ‘low’ requirement of upgrade to DDD (0.6–8.4%). This is not insignificant, and therefore, AAIR implantation for SND is only 1–3% in the US and central Europe. Manufacturers have addressed this by developing algorithms that reduce ventricular pacing to a minimum with a ‘pseudo-AAI’ mode with backup ventricular pacing, if required. It is likely that the benefits observed by Nielsen et al. with AAI pacing can be extrapolated to these new DDD devices. This is further supported by the linear relationship of ventricular pacing percentage and heart failure hospitalization and risk of AF in MOST. Large studies with these newer DDD systems may show superiority over VVI pacing and should be awaited before prematurily abandoning DDD pacing. DDD devices also improve patient diagnostics allowing accurate arrhythmia detection and enhanced pacemaker programming and can inform or monitor drug treatment and need for anti-coagulation. AF episodes recorded in this way have been shown to predict stroke5 and improve treatment by reducing AF-related hospitalizations.6 With home telemetry of Holter data, these monitoring features are going to become a crucial aspect of modern devices. Technological advances in device therapy will continue. With clearer identification of treatment goals, for example, less arrhythmia symptoms, reduced arrhythmia burden, beneficial remodelling effects, improved quality of life, or better exercise capacity, we will understand whether increasing complexity of device hardware is beneficial and cost-effective. It is our opinion that these objectives will not be met by the use of simple systems.