The PACE study is a prospective, randomised, double-blind, parallel study enrolling 177 patients at four hospitals in Asia. Patients had a Medtronic Insync III cardiac resynchronisation therapy-pacemaker (CRT-P), or bi-ventricular pacemaker without defibrillation, and had no prior history of heart failure with normal left ventricle function and ejection fraction greater than or equal to 45%. Patients were evaluated at one, three, six, nine and 12 months.

Cardiac resynchronisation therapy (CRT), also known as bi-ventricular pacing, is a treatment for heart failure that uses an implantable device to improve the pumping efficiency of the heart.

A cardiac resynchronisation therapy-pacemaker (CRT-P) is a stopwatch-sized device implanted in the upper chest to resynchronise (without defibrillation) the contractions of the ventricles by sending tiny electrical pacing impulses to the heart muscle, to help the heart pump blood throughout the body more efficiently and reduce symptoms.

Cardiac resynchronisation therapy is intended to complement standard drug treatment, and dietary and lifestyle modifications.

Meeting its primary objective, PACE results showed that after one year of pacing, patients with pacing in both right and left ventricles (bi-ventricular) had no significant changes in left ventricle size, while patients paced only in the right ventricle developed enlarged left ventricles.

Adverse changes in patients paced only in the right ventricle included a significant increase of 6.3ml on average in the size of the left ventricle at the end contraction, and a decrease of 6.8% in the ejection fraction, or the amount of available blood pumped from the left ventricle.

Cheuk-Man Yu, professor of medicine at Prince of Wales Hospital, and PACE’s lead investigator, said: “These early results show bi-ventricular pacing may be superior to pacing only in the right ventricle to preserve the heart’s normal left ventricle size and pumping ability for these pacemaker patients. As the first randomized study with this patient population, these initial results suggested that ensuring synchrony of the ventricles can help maintain patient health.”