New practice corrects pump function in heart failure

Cardiac resynchronisation therapy (CRT), or biventricular pacing, is used to treat heart failure patients with left bundle branch block. Electrical impulses that travel from the atria to the ventricles are delayed or blocked, causing a prolonged and abnormal heartbeat. For CRT, a pacemaker is implanted below the collarbone and three leads are attached in the heart to resynchronise the contraction by stimulation with pulses of electricity.

CRT alleviates symptoms, such as breathlessness and fatigue, and reduces mortality, yet 30-40% of patients do not improve (non-responders). One of the most important modifiable causes of non-response to CRT is non-optimal positioning of the left ventricular lead.

ESC guidelines advise placing the left ventricular lead at the back of the heart where late activation occurs, as this improves response to CRT. This is the current standard of care practice. The study focused on how to identify this site more precisely.

Previous randomised controlled trials have shown improved response to CRT, compared to standard care, when multimodality imaging is used to identify the latest mechanically activated segment for left ventricular lead placement. But multimodality imaging is time consuming and costly.

This study investigated whether lead placement at the region with the latest electrical activation would be superior to the region with the latest mechanical activation. The method uses electrical measurements obtained during the implant procedure and does not require pre-implant imaging.

The study design has been published. Briefly, 122 heart failure patients were randomly allocated to left ventricular lead placement at the latest electrically activated site (using electrical mapping) or the latest mechanically activated site (using imaging). Neither treatment is the current standard of care. Patients and staff responsible for follow-up care were blinded to the procedure. The primary outcome was change in left ventricular pump function (ejection fraction) at six months.

The absolute increase in left ventricular ejection fraction was significantly larger in the electrical group (11%) compared to the imaging group (7%; p=0.03). The difference was not statistically significant after adjusting for sex, baseline left ventricular ejection fraction and other factors.

Implantation took 19 minutes (22%) longer in the electrical (104 minutes) versus imaging (85 minutes) group with no increase in complications. There were no differences between groups in left ventricular reverse remodelling, New York Heart Association functional class, six minute walk test, and quality of life.

Principal investigator Dr Charlotte Stephansen, of Aarhus University Hospital, Denmark, said: "Increased left ventricular ejection fraction after CRT is associated with a better prognosis. The 4% greater increase in the electrical group is of a magnitude shown to improve functional response and cardiac event-free survival in previous studies, indicating that the improvement is clinically important."

The Danish-CRT trial, set to enrol 1,000 patients, is testing whether electrically guided positioning of the left ventricular lead reduces hospitalisation for heart failure or death compared to standard of care lead placement.