Effects of cardiac resynchronization therapy on heart rate turbulence.

BACKGROUND

Cardiac resynchronization therapy (CRT) improves the clinical status of patients with heart failure (HF), though its effects on heart rate turbulence (HRT) are unknown.

METHODS

We measured HRT indices in 58 recipients of CRT systems (mean age = 56 +/- 9 years, 41 men) in New York Heart Association HF functional class III-IV, and with a left ventricular (LV) ejection fraction < or =35%. At 6 months of follow-up, 42 patients were responders and 13 nonresponders to CRT, and three patients died suddenly. The HRT indices turbulence onset (TO%) and turbulence slope (TS ms/RR interval) were calculated from digital 24-hour electrocardiogram before and after 6 months of CRT. TO > or = 0% and TS < or = 2.5 ms/RR interval were considered abnormal.

RESULTS

Mean TO in the entire population was 0.4 +/- 1.5 before CRT, and decreased to -0.8 +/- 7.0 during the 6 months of CRT (ns). TS increased significantly from 2.0 +/- 1.7 at baseline, to 3.9 +/- 3.1 (P < 0.05), and a significantly lower proportion of patients had abnormal HRT indices at 6 months. In contrast to the significant increase observed in responders, not significant change in TS was observed among the nonresponders.

CONCLUSIONS

During 6 months of CRT, improvements in HRT indices and a decrease in the proportion of patients with abnormal HRT were observed. CRT may have beneficial effects on baroreflex sensitivity.