An Incidental Mobitz II Block: Pacing Timing and His Existing Beta-Blocker
A single patient found to have a real indication for a pacemaker on a monitor nobody was watching for it. The disagreement is less about whether he needs the device than about what to do, in the meantime, with a drug he was already taking.
T.W., a 74-year-old man, spends most of his free time in his garage building furniture, and was moving a bookshelf he'd just finished when he tripped over an extension cord and fell, breaking his hip. He has longstanding hypertension, managed for over fifteen years on metoprolol, and no prior cardiac history. He underwent hip fracture repair two days ago, and routine post-operative telemetry — ordered for the surgery, not for any cardiac complaint — picked up brief, self-terminating runs of 2:1 atrioventricular block that an electrophysiology consult confirmed as infra-Hisian, true Mobitz II, rather than the AV-nodal Wenckebach pattern that can look identical on a surface tracing — a 2:1 pattern cannot be separated into Mobitz I or II by the ECG alone, which is precisely why the consult was called.
He has had no syncope, no dizziness, nothing that would have brought this to anyone's attention on its own. Mobitz II is a recognized indication for permanent pacing regardless of symptoms, because unlike AV-nodal block, it can progress abruptly to complete heart block without warning. The electrophysiology team wants him paced before he leaves the hospital rather than referred outpatient. A separate, smaller question has come up alongside that one: whether his metoprolol, a drug that can itself slow AV conduction, needs to be held while he waits for the device, or whether the mechanism of his block makes that concern less relevant than it might first sound. He remains hemodynamically stable on continuous telemetry, and the surgical team has already cleared him medically for the pacemaker procedure, which leaves timing and this one medication question as the only things still unsettled before he can go home.
Pacing timing, and a drug already on board
I want him paced before discharge, not referred to an outpatient clinic and told to come back. Mobitz II can progress to complete heart block without any warning symptom, and he's already demonstrated the underlying disease on telemetry we happened to be watching for an unrelated reason. I don't want to rely on a second unrelated admission to catch the progression if it happens between now and an outpatient appointment.
Agreed on the timing. My question is about his metoprolol in the interim — he's been on it for fifteen years for his blood pressure, and I don't want to stop a long-term medication reflexively out of concern it's contributing to his AV block, especially perioperatively, when abrupt discontinuation risks rebound hypertension and tachycardia on top of everything else he's already recovering from.
I wouldn't stop it. Mobitz II is a disease of the His-Purkinje system, below the AV node, and beta-blockers act primarily on AV-nodal conduction — they're not typically what's driving an infra-Hisian block the way they can worsen AV-nodal Wenckebach. His metoprolol dose hasn't changed recently, and there's no reason to think it caused this or that continuing it at the same dose will meaningfully worsen it. Continue it unchanged, keep him on continuous telemetry until the pacemaker is placed, and let the device solve the actual problem rather than pulling a stable medication that isn't the one responsible for it.
Permanent pacemaker placed before discharge, on the same admission as his hip repair. Metoprolol continued unchanged throughout, with continuous telemetry maintained until the device was in place.