NEW YORK (Reuters Health) – In patients with nonischemic dilated cardiomyopathy, the left ventricular (LV) pacing site is a key determinant of the hemodynamic response to resynchronization – but contrary to common belief, the lateral LV wall and the coronary sinus are rarely the best sites, an international team of cardiologists has found.

Dr. Nicolas Derval, from Hopital Cardiologique du Haut-Leveque, Bordeaux, France, and colleagues also found that not only does the optimal site vary from patient to patient, but also that it “cannot be defined a priori.”

While cardiac resynchronization therapy (CRT) reduces morbidity and mortality in patients with heart failure, 20% to 40% of eligible patients may not fully benefit from CRT device implantation, the investigators point out.

In an expedited publication in the Journal of the American College of Cardiology posted online November 18, Dr. Derval and associates describe their efforts to identify optimal pacing sites in 35 patients with nonischemic dilated cardiomyopathy referred for CRT device implantation. The patients were in New York Heart Association functional class III or IV despite optimal medical therapy, with LV ejection fraction less than 35%.

The researchers compared hemodynamic responses to pacing at the conventional coronary sinus site and at 10 predetermined LV pacing sites: the basal and mid-ventricular segments of four different walls of the left ventricle (septal, anterior, lateral, inferior), the apex, and the endocardial site facing the coronary sinus.

“Major inter-individual and intra-individual variations of hemodynamic response depending on the LV pacing site were observed,” the authors report.

“In some patients,” they note, “there was as much as an 81% difference in (response) between the best and worst locations.”

Pacing at the best LV site improved the response rate and doubled the improvement in LV hemodynamic function observed with coronary sinus pacing, the investigators said.

Until now, an accompanying editorial suggests, it has been “commonly believed but not adequately proved (that) a ‘one-size-fits-all strategy’ does not work” with CRT.

Dr. Jagmeet P. Singh from the Massachusetts General Hospital, Boston, and Dr. William T. Abraham from The Ohio State University Medical Center, Columbus, point out, however, that the evaluation process this study employed “is impractical to adapt to everyday use.”

“The message that we need to individualize our approach is important, but how we do so in a practice-oriented way still needs to be defined,” the editorial concludes.

Reference:
J Am Coll Cardiol 2009.