An 80-year-old man was referred to our institution for recent dyspnoea on exertion associated with asthenia for a few months. Physical examination, blood tests, chest X-ray and spirometry were normal. An electrocardiogram ( Fig. 1 A ) showed first-degree atrioventricular block (AVB) with a PR interval of 560 ms. Holter monitoring showed that during morning activity (walking), the P waves gradually merged with the QRS complexes. Wenckebach periods appeared as the heart rate exceeded 100 beats/min ( Fig. 1 B). A transthoracic echocardiogram revealed normal left ventricular systolic function but low cardiac output (3.8 L/min). Doppler tissue imaging at the mitral and tricuspid annulus showed A′ waves before the E′ waves ( Fig. 2 A and C ). Left and right ventricular filling was compromised because the atria were contracting before the atrioventricular (AV) valves opened ( Fig. 2 E). We observed reversed blood flow inside the inferior vena cava (IVC), responsible for expansion of the IVC following each right atrial contraction ( Fig. 3 A ). A dual-chamber pacemaker was implanted, with an immediate improvement in both clinical and echocardiographic variables ( Fig. 2 B, D and F) once the AV delay had been programmed at 200 ms ( Fig. 1 C). Right and left ventricular filling improved once AV synchrony was restored. At follow-up, 6 months after the procedure, the patient was free of symptoms. Pacemaker implantation is a class IIa recommendation for marked first-degree AVB responsible for haemodynamic compromise due to loss of AV synchrony.
