ORLANDO — Chronotropic index, a measure of heart rate response in an exercise test, significantly correlated with the risk for postpartum adverse cardiac events in a review of 83 women with congenital heart disease.
The finding shows that chronotropic index can provide valuable guidance when counseling women with congenital heart disease about the risk they face from pregnancy for triggering a cardiac or neonatal event, Dr. George K. Lui said at the annual scientific sessions of the American Heart Association.
The chronotropic index “is a helpful tool,” along with other risk markers such as a history of heart failure or of sustained arrhythmias, said Dr. Lui, director of adult congenital heart disease at Montefiore Medical Center in the Bronx, N.Y. “Stress testing adds to the risk assessment and counseling,” of these women, “especially in patients at borderline risk,” he said in an interview.
His study used data collected through the Alliance for Adult Research in Congenital Cardiology at 13 centers in the United States and Canada.
The 83 women had undergone a cardiopulmonary exercise test within the period starting 2 years prior to their pregnancy and running through the end of their first trimester. Their average age was 29 years, 88% had New York Heart Association class I heart failure, 12% had class II symptoms, and none were cyanotic.
The most common congenital heart disease was repaired tetralogy of Fallot, in 35%; D-transposition of the great arteries, in 29%; left-sided obstruction lesions, in 11%; and right-sided obstructive lesions, in 10%.
The study included outcomes from the 89 pregnancies.
The chronotropic index calculation involved subtracting a woman's resting heart rate from her peak exercise heart rate and dividing the difference by 220 minus her age and minus her resting heart rate.
According to a survey of healthy adults published in 1989, normal chronotropic index is 1.0, with a normal range of 0.8-1.3 (J. Cardiovasc. Electrophysiol. 1989;3:176-80).
The women in Dr. Lui's study had an average chronotropic index of 0.75. More than half had a chronotropic index below the normal range cutoff of 0.80.
During pregnancy, 15 of the women had a cardiac event, including 12 with heart failure, 6 with a sustained arrhythmia, and 1 death. Also, among the 89 pregnancies were 17 neonatal events, including 16 preterm deliveries, 7 neonates who were small for gestational age, and 3 episodes of respiratory distress syndrome.
Women who had a chronotropic index of less than 0.80 had a significantly increased risk for both a cardiac event and neonatal event.
A univariate analysis indicated that women with a chronotropic index of 0.80 or higher were 35% less likely to have a cardiac event and their pregnancies were 27% less likely to have a neonatal event, compared with women with a chronotropic index of less than 0.80.
Results of multivariate analysis that controlled for treatment with an antiarrhythmic medication showed that a chronotropic index of 0.80 or higher lowered the risk for a maternal cardiac event by 30%.
Dr. Lui stated that he had no financial disclosures.
Women who had a chronotropic index of less than 0.80 had an increased risk for cardiac and neonatal events.
Source DR. LUI