| Coronary artery disease (CAD) refers to the coronal atherosclerosis causing the lumen narrow or obstruction leading to myocardial ischemia, also known as ischemic heart disease, which is a major disease hazard to the health, in China, and the morbidity is on the rise. Studies have shown that, most of CAD patients have autonomic nervous system dysfunction. In addition, autonomic nervous system function is closely related with cardiovascular events in patients with CAD. At present, an indicator of electrocardiology on evaluation of the autonomic nervous system function has become a new research direction. Myocardial ischemia plays the main part of the CAD's occurrence and development, and its severity is related with the patient's prognosis. However, for more than two-thirds of CAD patients are silent myocardial ischemia (SMI), but ambulatory electrocardiogram (AECG) and other checks will still be able to find an objective basis for myocardial ischemia, which have the same sense of the prognosis like angina. As the patients of SMI may have no symptoms and be ignored, but prone to various types of cardiac events and lead to adverse consequences, so SMI has a great impact on the patient's prognosis.Heart rate turbulence (HRT) and heart rate variability (HRV) are the indicators of electrocardiology on evaluation of the autonomic nervous system function with AECG technology. Parameters to describe the phenomenon of HRT are turbulence onset (TO) and turbulence slope (TS), which are recorded and calculated by a 24-hour AECG; the common indicators of HRV are SDNN, SDANN, RMSSD, RNN50, which are directly acquired by the AECG report.At present, a number of foreign multi-center study has confirmed that the predictive value of HRT and HRV for post-myocardial infarction sudden cardiac death, and the similar reports have come from domestic studies. As we know, sudden cardiac death is the SMI-prone cardiovascular events, patients with CAD only performance as SMI, whether these patients also have autonomic nervous system dysfunction, and whether HRT and HRV is valid indicator of evaluation on autonomic nervous system of the patients with SMI. This study is focus on the diversify regularity of HRT and HRV in patients of SMI, in order to explore the evaluating effect of HRT and HRV in patients of SMI.This study was to choose 130 cases of myocardial ischemia in patients with CAD (of which 90 cases for SMI, 40 cases of symptomatic myocardial ischemia) and controls, all the cases perform a 24-hour AECG, and to gather the following parameters, including gender, age, the total number of a 24-hour premature ventricular complex, and all the index of HRT (TO, TS), HRV (SDNN, SDANN, RMSSD, RNN50) were contrast analyzed. First of all, patients were divided into myocardial ischemia group (n = 130) and the control group (n = 40); second, myocardial ischemia group was divided into two subgroups according to accompanied clinical symptoms (chest tightness, shortness of breath, angina, etc.), one with symptoms of myocardial ischemia group (n = 40) and the other was SMI group (n = 90); third, SMI group was divided into 3 subgroups according to Cohn typing: full SMI group (n = 30), the SMI post-myocardial infarction group (n = 30) and the SMI associated with angina attack group (n = 30).The results showed no significant difference in the total number of a 24-hour premature ventricular complex, sex and age among the groups;All the parameters of HRT and HRV showed significant difference between SMI group and control group, TO of SMI group was significantly higher than that of control group, while TS and HRV indexes of SMI group were significantly lower than that of control group, but all the parameters showed no statistical significance between the SMI group and myocardial ischemia accompanied with symptoms group; The parameters of HRT and HRV showed significant difference between the SMI post-myocardial infarction group and full SMI group/ the SMI associated with angina attack group, TO of the SMI post-myocardial infarction was higher than that of the other two subgroups, TS and the HRV parameters were lower than those of the other subgroups, while the parameters of HRT and HRV showed no statistical significance between full SMI subgroup and the SMI associated with angina attack subgroup; In the SMI group, TO was negatively correlated with SDNN and SDANN, TS was positively correlated with SDNN, SDANN, RMSSD and PNN50; Among all the parameters of HRT and HRV, TO, TS and SDNN were good indicators for SMI, in addition, TO was the best indicator for SMI, while SDANN and RMSSD had no indicated value for SMI; Compined TO, TS and SDNN would increase the indicated value for SMI, and compined TO and TS had the best indicated value for SMI.Through the study we came to the conclusion: 1. SMI patients have autonomic nervous system dysfunction, especially in patients with SMI post-myocardial infarction. 2. These two groups which are SMI patients and symptomatic myocardial ischemia patients have the similar prognosis. 3. TS and HRV have the same physiological basis, that is, they reflect efferent state of pneumogastric nerve, TO is likely the result of common-control of sympathetic nerve and pneumogastric nerve. 4. Although HRT and HRV have certain limitations, they are still an effective evaluation of the autonomic nervous system function in patients with SMI. 5. For SMI patients, HRT and HRV's evaluation on autonomic nervous system has certain significance on the improve prognosis and clinical treatment.
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