Case: An elderly man with a pacemaker and chest pain – what are wemissing?

An 85-year-old man with known cognitive impairment was admitted with stabbing chest pain and shortness of breath. He had a single-chamber pacemaker implanted for permanent atrial fibrillation.

On admission

• Troponin T was normal, without dynamic changes.

• The ECG was described as “pacemaker rhythm.”

• Ischemia was considered difficult to exclude due to the paced rhythm.

Previous medical history

The patient had been admitted a few months earlier with similar symptoms. At that time, the ECG was also described as “pacemaker rhythm,” without further evaluation.

ECG findings

Review of two ECGs taken during admissions showed:

• Some irregular P-waves.

• Both wide and narrow QRS complexes.

• Sharp T-waves following paced beats, which in fact masked retrograde P-waves.

How does a single-chamber pacemaker work?

A single-chamber pacemaker is usually placed in the right ventricle. It stimulates the ventricle if the heart rate falls below a threshold, typically 60 beats per minute. The most common mode is VVI, which is not synchronized with atrial activity.

What happened in this case?

The patient had likely regained sinus rhythm, but at a slow rate of around 40 beats per minute. The pacemaker therefore took over pacing. The result was atrioventricular asynchrony, with atrial contraction occurring when the AV valves were closed.

This led to pacemaker syndrome, with symptoms such as:

• Dyspnea.

• Jugular venous pulsations.

• Palpitations.

• Chest pain or general discomfort.

Learning points

• Simply describing an ECG as “pacemaker rhythm” is insufficient. Both atrial and ventricular activity must be assessed.

• Always know the pacemaker type and understand its mode of function.

• Pacemaker syndrome typically occurs with VVI pacing in patients who have regained sinus rhythm.

• A single-chamber pacemaker is best suited for permanent atrial fibrillation, not when sinus rhythm is restored.

Conclusion

This case demonstrates how pacemaker-related complications may easily be overlooked when an ECG is too readily labeled as “pacemaker rhythm.” In all patients with a pacemaker, the interaction between atria and ventricles should be carefully evaluated. Pacemaker syndrome can explain symptoms such as dyspnea, palpitations, and chest discomfort, and understanding the function of the pacemaker is crucial in clinical practice.