Key result
Disabling AV hysteresis and extending PVARP terminates pacemaker-mediated tachycardia, enabling vasopressor weaning.
Why the study?
Algorithms that minimize right ventricular pacing by prolonging AV delay can facilitate pacemaker-mediated tachycardia (PMT) that mimics sinus tachycardia and escapes device detection.
Case Report (n=1)
In paced patients with fixed tachycardia near 100-110 beats/min, active AV hysteresis can facilitate a slow pacemaker-mediated tachycardia that mimics sinus tachycardia and septic shock, which can be terminated by disabling hysteresis and extending PVARP.
Device interrogation warranted in paced patients with refractory shock; this case leaves open systematic assessment of AV hysteresis algorithm risks.
BACKGROUND: Algorithms that minimize right ventricular pacing, such as atrioventricular (AV) hysteresis, prolong the AV delay to promote intrinsic conduction. With intact ventriculoatrial (VA) conduction, this can facilitate pacemaker-mediated tachycardia (PMT). CASE SUMMARY: A 62-year-old woman with a dual-chamber pacemaker presented with respiratory failure and hypotension at a paced rate of 110 beats/min, treated for presumed sepsis with escalating vasopressors. Interrogation showed an upper tracking rate of 130 beats/min, AV hysteresis ON, and postventricular atrial refractory period (PVARP) (225 milliseconds) shorter than VA conduction (360 milliseconds), producing a 550-millisecond endless-loop PMT (∼109 beats/min) that escaped device detection. Disabling hysteresis and extending PVARP terminated it, allowing vasopressor weaning. DISCUSSION: When PVARP is shorter than the VA interval, a long AV delay converts retrograde conduction into a slow re-entrant circuit that escapes device diagnostics and mimics sinus tachycardia. TAKE-HOME MESSAGES: Suspect slow PMT in paced patients with fixed tachycardia near 100-110 beats/min when AV hysteresis is active. Disabling hysteresis and extending PVARP beyond VA conduction is diagnostic and lifesaving.
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Abrol et al. (2026) conducted a case report in Pacemaker-mediated tachycardia (n=1). Disabling AV hysteresis and extending PVARP was evaluated. Disabling atrioventricular hysteresis and extending the postventricular atrial refractory period terminated a 109 beats/min pacemaker-mediated tachycardia, allowing vasopressor weaning.
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