The return map: simple test for diagnosing disrupted nervous control of the heart period variation in cardiac diseased patients

Studies the complexity of heart period variation in randomly selected population of 210 cardiac diseased patients and 26 healthy subjects. Repeated return maps with increasing time-lag from 1 to 6 was used. Each return map was quantified by calculation of coefficient of correlation Rret1 (to6). Rret1 was diminished in all groups of cardiac patients, as compared to controls (0.611+/-0.141). The lowest Rret1 values were observed in 35 pts suffering from intrinsic sinus node dysfunction (0.315+/-0.237), in 21 pts after myocardial infarction (0.360+/-0.189) and in 26 pts with unexplained syncope (0.395+/-0.174). They presented lower Rret values despite much weaker differences in magnitude of heart period variation. The authors concluded that increased complexity of RR variability is not accompanied by an increment of RR variation magnitude and could be find in patients with normal or decreased overall RR variation. The authors suggest to use the return map to detect abnormal neural control of heart rate in the presence of normal magnitude of its variation.