A 59-year-old male patient was referred to our hospital for treatment of paroxysmal atrial fibrillation since 8 years, with frequent presentations to the emergency department for cardioversion. Previously, post-cardioversion sinus bradycardia was observed. After extensive discussion of the treatment options, the patient opted for a minimally invasive surgical pulmonary vein isolation. The ECG shown was recorded during ablation of the left-sided pulmonary veins (Fig. 1).

Fig 1
figure 1

ECG recording during surgical pulmonary vein isolation

Question

What is the mechanism of this trigeminy rhythm?

You will find the answer elsewhere in this issue.