Heart rhythm conundrumBMJ 2017; 357 doi: https://doi.org/10.1136/bmj.j2215 (Published 01 June 2017) Cite this as: BMJ 2017;357:j2215
- Rhodri Huw Davies, , specialist registrar (ST6) in cardiology,
- Dewi Eurfyl Thomas, consultant in cardiology and electrophysiology
- Morriston Cardiac Centre, Swansea, UK
- Correspondence to RH Davies
A 40 year old man was referred to the cardiology team because of bradycardia. He was an inpatient undergoing treatment for an infection of unknown origin and he had developed acute-on-chronic kidney dysfunction. His medical history included type 1 diabetes, a previous renal transplant for diabetic nephropathy, and permanent atrial fibrillation.
The patient was asymptomatic, with a blood pressure of 122/74 mm Hg and a pulse oximetry reading of 97% on room air (normal value ≥94%) His electrocardiogram (ECG) at the time of referral is shown in figure 1⇓.
What is the underlying rhythm on the ECG?
What are the potential causes of bradycardia in this patient?
How should the patient be managed and what is the definitive treatment?
1. What is the underlying rhythm on the ECG?
The atrial rhythm is atrial fibrillation. However, the ventricular rate is slow (36 beats/min) and regular with broad QRS complexes. The patient has developed atrial fibrillation with complete heart block.
The ECG has no discernible p waves, but there are fibrillatory waves seen in some leads. The appearance of the atrial activity in lead V1 can sometimes be confused with atrial flutter or a focal atrial tachycardia. This phenomenon occurs because the right atrial appendage lies between the V1 electrode and the left atrium and effectively “filters” the waves so that they appear organised. However, there is no organised atrial activity in the other leads and closer inspection of the fibrillatory waves in lead V1 shows an irregular and rapid rate, …