Hiccups since the new pacemaker went in

The case

81-year-old man. Hiccups since the new pacemaker went in

Gordon had a dual-chamber pacemaker implanted two days ago for complete heart block after recurrent syncope. He was discharged yesterday and has had constant hiccups since last night, with two near-syncopal episodes this morning.

On arrival

SpO2: 96%
Heart rate: 24
Blood pressure: 86/50
Respiratory rate: 18

Stage 1 of 3

He is pale and drowsy but alert. A rhythm strip is recorded on arrival.

Tracing 1 of 2 for the quiz “Hiccups since the new pacemaker went in”. — Monitor, lead II, 25 mm/s, 15 s Open this tracing in the studio

What does this rhythm strip show?

AIntermittent failure to capture Correct answer Your answer
BOversensing with inhibition of pacing Your answer
CFailure to pace (no output) Your answer
DNormal pacemaker function with sinus rhythm Your answer

Every sinus P wave is followed, after a fixed delay, by a ventricular pacing spike, so the device is sensing the atria and pacing on time: there is no failure of output. However, many of those spikes are not followed by a QRS complex, and the effective ventricular rate is only about 24 per minute. That is intermittent failure to capture. Oversensing would inhibit the spike itself, producing pauses with no spike visible. None of the P waves conducts on its own, which is the complete heart block the device was implanted for.

What most likely links the hiccups to the pacing problem?

ALead displacement with diaphragmatic stimulation Correct answer Your answer
BBattery depletion Your answer
CElectromagnetic interference Your answer
DPacemaker-mediated tachycardia Your answer

Persistent hiccups beginning within days of implantation suggest the ventricular lead has moved and is stimulating the diaphragm or phrenic nerve. A displaced lead also explains the failure to capture, because the electrode is no longer in reliable contact with excitable myocardium. Battery depletion two days after implantation is essentially unheard of. Pacemaker-mediated tachycardia is a fast, re-entrant rhythm through a dual-chamber device, not a slow one.

Stage 2 of 3

Over the next few minutes Gordon becomes more bradycardic and increasingly drowsy. The monitor shows stretches of nearly five seconds with no QRS complex.

Observations

Heart rate: 18
Blood pressure: 72/40

What is the most appropriate immediate management?

ATranscutaneous pacing with sedation as tolerated Correct answer Your answer
BIntravenous atropine and observe Your answer
CPlace a magnet over the generator Your answer
DArrange an outpatient pacing check Your answer

This patient has no ventricular escape rhythm and is haemodynamically compromised. Transcutaneous pacing provides immediate reliable ventricular capture while urgent arrangements are made for lead revision. Atropine acts at the AV node and is unlikely to help when the block is infranodal and there is no escape focus to accelerate. A magnet switches the device to asynchronous mode at its fixed rate, but the spikes are already firing on time and the problem is that they are not capturing, so asynchronous pacing will not restore capture.

Stage 3 of 3

Gordon is stabilised with transcutaneous pacing and transferred for urgent lead repositioning. A twelve-lead ECG is recorded afterwards.

Tracing 2 of 2 for the quiz “Hiccups since the new pacemaker went in”. — 12-lead, 25 mm/s, 10 mm/mV Open this tracing in the studio

Observations

Heart rate: 76
Blood pressure: 128/74

What does the ECG now show?

AP-synchronous ventricular pacing with consistent capture Correct answer Your answer
BVentricular tachycardia Your answer
CLeft bundle branch block with sinus rhythm Your answer
DPersisting failure to capture Your answer

Every P wave is now followed by a pacing spike and a broad QRS complex, so the device is tracking the atria and capturing the ventricle on every beat, at about 76 per minute. The QRS is broad because ventricular pacing activates the myocardium from the lead tip rather than through the normal conduction system, which is expected rather than pathological. The pacing spike before each QRS separates this from left bundle branch block in sinus rhythm.

Diagnosis

Early ventricular lead displacement with intermittent failure to capture and diaphragmatic stimulation, in a pacemaker-dependent patient

This patient is pacemaker-dependent: his own rhythm is complete heart block with no ventricular escape, so every lost capture is a lost heartbeat. On the monitor strip each P wave is tracked by a ventricular pacing spike, but only a minority of those spikes produce a QRS. That pattern is intermittent failure to capture, and its most common cause in the first days after implantation is displacement of the ventricular lead. The hiccups are diaphragmatic stimulation, which should raise concern for lead displacement or myocardial perforation.

The practical lesson is a three-step framework for any pacing malfunction on a rhythm strip. First, are pacing spikes present? If not, the problem is failure of output. Second, does every spike produce a QRS? If not, it is failure to capture. Third, is pacing appropriately inhibited by native beats? If not, it is a sensing fault. In a pacemaker-dependent patient with no escape rhythm, failure to capture is an emergency: transcutaneous pacing bridges to lead revision. Workup includes chest radiography and device interrogation, with echocardiography if perforation is suspected.

References

Safavi-Naeini P, Saeed M. Pacemaker Troubleshooting: Common Clinical Scenarios. Tex Heart Inst J. 2016;43(5):415-418.
Glikson M, Nielsen JC, Kronborg MB, et al. 2021 ESC Guidelines on cardiac pacing and cardiac resynchronization therapy. Eur Heart J. 2021;42(35):3427-3520.

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Discussion

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