Atriobiventricular pacing (cardiac resynchronisation) is a promising treatment for patients with advanced heart failure and conduction abnormality.1 These patients have severely impaired exercise tolerance and this has been shown to be multifactorial. The present study examined, in detail, the effect of cardiac resynchronisation on maximal and submaximal exercise capacity as evaluated by metabolic exercise testing.

A consecutive series of patients from a single centre with cardiac resynchronisation therapy, able to perform baseline and follow up treadmill tests, were enrolled in the study. Inclusion criteria were New York Heart Association (NYHA) functional class III/IV heart failure on maximal medical treatment, left ventricular ejection fraction < 35%, left ventricular end diastolic dimension > 60 mm, and QRS duration > 130 ms. Patients with chronic atrial fibrillation were excluded. The protocol was approved by the hospital research and ethics committee and all subjects gave written informed consent.

Left ventricular (LV) stimulation was accomplished by a lead inserted into an LV branch of the coronary sinus. Specially designed leads were used (Medtronic 2187 or 2188, Medtronic Inc, Minneapolis, Minnesota, USA). Right atrial and ventricular leads were positioned in the right atrial appendage and right ventricular apex, respectively. All patients received cardiac resynchronisation devices (InSync, Medtronic Inc) with one atrial and two ventricular ports. Optimal atrioventricular delays were …