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Related Experiment Video

Updated: Jul 17, 2026

A New Single Chamber Implantable Defibrillator with Atrial Sensing: A Practical Demonstration of Sensing and Ease of Implantation

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Undesirable mode switching with a dual chamber rate responsive pacemaker

M R Pitney¹, C D May, M J Davis

¹Eastern Heart Clinic, New South Wales, Australia.

Pacing and Clinical Electrophysiology : PACE

|April 1, 1993

Summary

The Telectronics 1250 Meta MV DDDR pacemaker can undesirably switch to VVIR pacing during sinus tachycardia. Patients with normal sinus node function may benefit from DDD pacing to avoid this, or require careful parameter programming for DDDR mode.

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Area of Science:

Electrophysiology
Cardiovascular Devices
Medical Engineering

Background:

The Telectronics 1250 Meta MV DDDR pacemaker offers automatic mode switching from DDDR to VVIR pacing during atrial arrhythmias.
Sinus tachycardia, a common physiological response, can inadvertently trigger this mode switch, potentially compromising optimal pacing therapy.

Purpose of the Study:

To evaluate the incidence and predictors of undesirable mode switching in patients with the Telectronics 1250 Meta MV DDDR pacemaker.
To assess the impact of specific pacemaker programming parameters on mode switching behavior during physiological stress.

Main Methods:

Retrospective analysis of 24 pacemaker implants, focusing on 11 patients with AV conduction disorders.
Exercise testing and Holter monitoring were employed to evaluate mode switching occurrences.
Analysis of programming parameters including rate response factor, upper rate setting, postventricular atrial refractory period (PVARP), and AV delay.

Main Results:

Seven of eight evaluated patients experienced repeated undesirable mode switching to VVIR pacing at low exercise levels.
Key precipitating factors identified were a low rate response factor, low upper rate setting, long base PVARP, and long AV delay.
Patients spent up to 50% of monitoring time in VVIR mode instead of the intended DDDR mode.

Conclusions:

Patients with intact sinus node function are susceptible to undesirable mode switching with DDDR pacing.
Programming to DDD mode is recommended for these patients unless a specific indication for DDDR pacing exists.
If DDDR mode is necessary, careful optimization of rate response, upper rate, PVARP, and AV delay is crucial to prevent unwanted mode switching.