Changes Of Heart Rate Turbulence In Patients With Unstable Angina Pectoris And Its Correlation With Clinical Factors

Background and objective Sudden cardiac death (SCD) is one of the leading causes of death among patients with unstable angina pectoris(UAP). Recently, heart rate turbulence (HRT), marker of Autonomic Nervous System(ANS) balance has been introduced for risk stratification and it had an important clinical significance in predicting high-risk of SCD. HRT express fluctuations of sinus-rhythm cycle length after a single ventricular premature complex(VPC). It is a physiological phenomenon consisting of the early acceleration and subsequent deceleration of a sinus rhythm after a ventricular premature beat (VPC). Such a characteristic pattern does not occur in high-risk patients with MI. It was shown that abnormal HRT had the predictive value of the adverse outcome in Post-MI patients, even better than currently used risk factors such as left-ventricular dysfunction, T-wave alternans, QT dispersion, positive late potentials and heart rate variability (HRV). This result had been confirmed by retrospective evaluation in several multicenter trails. UAP has the same physiopathological mechanism with AMI. The role of HRT for risk stratification in patients with UAP and its relationship with other clinical risk factors had not been determined. The aim of this study is to observe the changes of HRT in patients with UAP and to analyze the effect of clinical factors such as age, left ventricular dysfunction, diabetes, medication and percutaneous coronary intervention(PCI)on HRT parameters in UAP patients.Method 63 patients with UAP and 49 healthy controls were chosen. HRT parameters including turbulence onset (TO), turbulence slope (TS) and turbulence dynamicity (TD), and heart rate variability (HRV) including SDNN, rMSSD and PNN50 were deteched by 24h dynamic electrocardiogra (DCG). Patients with UAP were divided into several subgroups according to clinical characteristics, risk stratification, severity of the coronary arteries disease, respectively. The value of HRT parameters were compared between UAP group and control group, and between each subgroups of UAP.Result 1. The levels of TO and TD in the patients with UAP were higher than those of the controls (P<0.05). TS and SDNN were significantly lower than those of the controls (P=0.001). 2. Patients over 60 years, with diabetes, OMI and with LVEF<45% had significantly higher TO and lower TS than those without these clinical factors, (P<0.05) respectively. But only diabetes patients had lower TD value compared with non-diabetes patients. (P<0.05) 3. Patients with multivessel coronary lesions had significantly lower TS (P<0.05) and higher TD (P<0.05) than those patients with single coronary disease. The same result also can be observed in patients with higher coronary artery stenosis score (>10) than lower score. 4. TO and TD were higher and TS was lower in the high-risk group compared to those in mid-risk and low-risk group. (P<0.05) The incidence of abnormal HRT in high risk group was significantly higher than mid and low risk group (x2=9.227, P=0.01). 5. TO was positively correlated with age(P=0.01)and was negatively correlated with SDNN, LVEF(P<0.05). TS displayed negative correlation with age, the number of abnormal coronary arteries and high coronary artery stenosis score (P < 0. 05) but positive correlation with SDNN,PNN50,rMSSD(P < 0. 05). TD were positively correlated with number of abnormal coronary artery and coronary artery stenosis score (p<0.05). 6. Compared to the group with normal HRT, patients with abnormal HRT parameters were characterized by features of more risk factors, such as age over 60 years, MI history, LVEF<45%, diabetes. Multivariate analysis revealed age over 60 years and MI history as independent factors associated with abnormal HRT parameters. 7. There were no variances of HRT parameters in patients who were treated or not with angiotensin-converting enzyme inhibitor (ACEI) or Angiotensin receptor antagonist (ARB), beta-blocker and statins. SDNN and TS were improved after PCI in UAP patients. (P < 0. 05)Conclusion Abnormal values of HRT are observed in patients with UAP. HRT can be used as a new valuable marker for risk stratification in UAP patients. Clinical multiple factors such as age, prior MI, diabetesand left ventricular dysfunction can influence values of HRT parameters. Old age and MI history are independent factors associated with abnormal HRT. Revascularization with PCI can probably improve HRT in high risk UAP patients.