Patients with uncomplicated coronary artery disease have reduced heart rate variability mainly affecting vagal tone

Aim-To investigate whether uncomplicated chronic coronary artery disease ca uses changes in heart rate variability and if so, whether the heart rate va riability pattern is different from that described in patients with acute m yocardial infarction. Methods-Heart rate variability was studied in 65 patients with angina who h ad no previous myocardial infarcts, no other diseases, and were on no drug that could influence the sinus node. Results were compared with 33 age matc hed healthy subjects. The diagnosis of coronary artery disease in angina pa tients was established by coronary angiography in 58, by thallium scintigra phy in six, and by exercise test only in one. Patients and controls were Ho lter monitored 24 hours outside hospital, and heart rate variability was ca lculated in the frequency domain as global power (GP: 0.01-1.00 Hz), low fr equency peak (LF: 0.04-0.15 Hz), high frequency peak (HF: 0.15-0.40 Hz), LF /HF in ms(2), and in the time domain as SDNN (SD of normal RR intervals), S DANN (SD of all five minute mean normal RR intervals), SD (mean of all five minute SDs of mean RR intervals), rMSSD (root mean square of differences o f successive normal RR intervals) (all in ms), and pNN50 (proportion of adj acent normal RR intervals differing more than 50 ms from the preceding RR i nterval) as per cent. Results-The mean age in patients and controls was 60.4 (range 32-81) and 59 .1 (32-77) years, respectively (NS), the male/female ratio, 57/65 and 24/33 (NS), and the mean time of Holter monitoring, 23.0 (18-24) and 22.8 (18-24 ) hours (NS). Mortality in angina patients was 0% (0/65) at one year, 0% (0 /56) at two years, and 3% (1/33) at three years. Compared with healthy subj ects angina patients showed a reduction in GP (p = 0.007), HF (p = 0.02), L F (p = 0.02), SD (p = 0.02), rMSSD (p = 0.01), and pNN50 (p = 0.01). No sig nificant difference was found in RR, LF/HF, SDNN, or SDANN. Conclusions-Uncomplicated coronary artery disease without previous acute my ocardial infarction was associated with reduced high and low frequency hear t rate variability, including vagal tone. SDANN and SDNN, expressing ultra low and very low frequencies which are known to reflect prognosis after acu te myocardial infarction, were less affected. This is in agreement with the good prognosis in uncomplicated angina in this study.