Total cavopulmonary and atriopulmonary connections are associated with reduced heart rate variability

Aim-To determine whether cavopulmonary connections are associated with abno rmalities of heart rate variability. Methods-Heart rate variability was studied by 24 hour Holter monitoring in 39 patients (mean (SD) age 12.2 (4.1) years) who underwent cavopulmonary co nnection operations (partial in 12, total in 13, and atriopulmonary in 14). Two control groups were used: 18 healthy children (11.1 (2.5) years) and 1 6 patients (11.7 (4.3) years) undergoing cardiovascular surgery for biventr icular repair of congenital heart disease. All patients were in sinus rhyth m and had normal left ventricular function. Four time domain indices were c alculated: mean duration of RR intervals (RR), standard deviation of all RR intervals (SD), square root of the mean squared differences of successive RR intervals (r-MSSD), and percentage differences of successive RR interval s of > 50 ms duration (pNN50). Four frequency domain indices were calculate d: total power (TP), low frequency (LF), high frequency (HF), and the LF:HF ratio. Results-Heart rate variability indices were identical in the two control gr oups. Significantly reduced heart rate variability was found in patients wi th total cavopulmonary connections and atriopulmonary connections compared with the two control groups. In patients with partial cavopulmonary connect ions, heart rate variability was reduced compared with healthy controls. No differences in heart rate variability could be related to clinical status (New York Heart Association functional class), number of surgical intervent ions, or presence of right atrial enlargement. Conclusions-Patients with cavopulmonary connections have significantly redu ced heart rate variability and a particularly low vagal drive.