Investigation On The Activity Of The Autonomic Nervous System And The Related Genetic Polymorphism In Patients With Coronary Artery Spasm

Coronary artery spasm （CAS） is one of the leading pathological causes of a widespectrum of ischemic heart diseases, ranging from variant angina pectoris to acutemyocardial infarction and even sudden cardiac death. However, the exact mechanism ofCAS is still not well understood. Recent studies have identified a number of precipitatingfactors that may play a role in the pathogenesis of CAS, which include endothelialdysfunction, smooth muscle cell hypersensitivity, increased oxidative stress, inflammation,genetic susceptibility and autonomic nerves system dysfunction.With the study extends, the role of autonomic nerves system dysfunction in thepathogenesis of CAS becomes a subject to be increasing noticed. A large number of studieshave consistently demonstrated that patients with CAS had autonomic nervous systemdisorder. However, which of the autonomic nerves system dysfunction, the sympatheticdysfunction or the vagal dysfunction plays a major role is still a dispute. This alsosuggested that the role of the autonomic nervous system dysfunction in the mechanism ofCAS may be complex and varied. Heart rate variability （HRV）, as a non-invasive method, isthe most sensitive indicator to evaluate autonomic nervous function.Our previous study investigated the characteristics of24-hour HRV in the patients withCAS and found that the reduction of vagal activity and the enhancement of sympatheticactivity may be the baseline features of the CAS patients during non-spastic episode.However, we did not catch the spastic episode and thus the overall level of HRV and thewhole situation of autonomic nervous system are still not clear.Therefore, we designed this study to learn more about the autonomic nervous systemdysfunction in Chinese CAS patients. We explored the status of the autonomic nervoussystem in CAS patients with clinical practical means of detection, such as cold pressor test,short-range HRV analysis, ultrasound Doppler, and then detected the association betweengenetic polymorphisms relating to autonomic activity and CAS, to evaluate the role of autonomic nervous system in the pathogenesis of CAS from the perspective of moleculargenetics and clinical function.Part I Study on the activity of the autonomic nervous system in patients withCASObjectivesTo observe the differences of the autonomic responses to the sympathetic activationwith cold pressor test in patients with CAS and health subjects. The responses of thebrachial artery to cold pressor test were also compared.Materials and MethodsCold pressor test was practiced on30patients with CAS and30health subjects. Bloodpressure, heart rate,5min-HRV analysis and the spectrum of brachial artery with colorDoppler ultrasonography were recorded before and after the cold pressor test, respectively.The data were showed as mean±SD and studied by student t test or χ2test.Results1. Among the parameters of HRV, the baseline of SDNN, RMSSD, PNN50, LF and HFwere significantly lower while the LF/HF value was significantly higher in the CAS groupthan in the control group before cold pressor test. No differences in heart rate, bloodpressure, the diameter and the PSV of brachial artery were found between the groups.2. After cold pressor test, the blood pressure and the value of SDNN, LF, TP andLF/HF rose significantly in both groups; the heart rate, the diameter of brachial artery andthe value of rMSSD, PNN50and HF did not change remarkably while the PSV of brachialartery decreased significantly in both groups. Compared between the two groups, thedifferences of SDNN, LF and TP value disappeared while the difference of LF/HF valueincreased further after cold pressor test. As same as the situation before cold pressor test, nodifferences in heart rate, blood pressure, the diameter and the PSV of brachial artery werefound between the groups after cold pressor test.Part II Investigation on the genetic polymorphisms related to the activity of theautonomic nervous system in patients with CASObjectivesTo investigate the differences of the genotype of4common polymorphic loci relatedto the activity of the autonomic nervous system (α_2BDel301-303, α_2CDel322-325, β₂Gln27Glu, and GNB3C825T) as well as the established risk factors of ischemic heartdisease in patients with CAS and health subjects.Materials and MethodsOne milliliter of blood was drawn from the median cubital vein in109patients withCAS and94health subjects. Genomic DNA was isolated from whole blood and then usedfor gene amplification by polymerase chain reaction （PCR）. Then the amplified productscorresponding to each different polymorphism were purified and analysed by gelelectrophoresis using1.5%agarose and sequenced using an ABI-prism3730sequencer toobtain the genotypes. Genotype and allelic frequency distributions of α_2BDel301-303（rs4066772）, α_2CDel322-325（rs2234888）, β₂Gln27Glu （rs1042714） and GNB3C825T（rs5443） were compared between the CAS patients and the health subjects with the χ2test.Odds ratios （ORs） and95%confidence intervals （CIs） for all potential risk factors related toCAS were calculated by binary logistic regression analysis to assess the effect of variousenvironmental and genetic factors on the presence of CAS.Results1. The minor alleles were α_2BDel301-303, α_2CDel322-325, β₂Glu27, and GNB3C825.Their frequencies were48.4%,13.3%,13.3%, and46.8%, respectively, in the controlsubjects of this Chinese population, all of which were different from the frequenciesreported in other races.2. No differences of the genotype and the allelic frequency of the4commonpolymorphisms related to the activity of the autonomic nervous system were found inpatients with CAS and health subjects.3. On univariate analysis, smoking and body mass index （BMI） were found to besignificant risk factors of CAS. After multivariate analysis using binary logistic regressionmodel, BMI （odds ratio （OR）:1.679;95%confidence interval （CI）:1.396-2.018; P <0.001）and smoking （OR:12.342;95%CI:5.072-30.028; P <0.001） remained as independent riskfactors.Conclusions1. The autonomic dysfunction is closely associated with CAS, expressed as that thereduction in vagal activity and the enhancement of sympathetic activity may be the baselinefeatures of the CAS patients and the autonomic responses to the sympathetic activation with cold pressor test may be much more acute in patients with CAS than in health subjects.2. There are presences of genetic polymorphisms at the loci of α_2BDel301-303,α_2CDel322-325, β₂Glu27Glu, and GNB3C825T in Chinese population and their allelefrequencies are different from those reported in other races. However, none of the fourgenetic polymorphisms related to the activity of the ANS that were tested have anysignificant association with CAS in Chinese patients. Smoking and BMI are the importantrisk factors of CAS.