Research On Using Microvolt Level T-Wave Alternans To Test The High Risk Group Of Sudden Cardiac Death

Objective To discuss the prognostic value of using Microvolt Level T-WaveAlternans (MTWA) to predict Malignant Ventricular Arrhythmia (MVA) and SuddenCardiac Death (SCD) and explore the methodology of time-domain way MTWAtesting, normal and abnormal value scope, indication group.Method The study enrolls 545 patients (285 male, 260 female, average age is 25years old) which receives a medical or physical examination in The First AffiliatedHospital of Kunming Medical College during January 2002～March 2007. All ofthem received the test of MTWA, and received some other auxiliary examinationaccording to their patient history and health examination, including echocardiogram,ECG, x-ray photographs, blood biochemistry, etc, 105 healthy persons after testing tobe the control group, 138 persons who have history of VT and VF or final diagnosisas organic heart disease patients (LVEF≤45％) to be the SCD high risk group. Bothof the control group and high risk group are all received testing of MTWA, LVEF,HRV, NSVT, QRS, QTc, etc. and accomplished follow-up. In high risk group receivedregular drug treatment, intervention and using PCI/CABG/ICD and so on treatments,dynamic follow up, compare death, causes of death, MVA, re-hospitalization, syncope,therapy intervention, cardiac status and so on in control group and high risk group,and to find the relationships between MTWA including other observation indicatorsand happening of death, causes of death, MVA, re-hospitalization, syncope, therapyintervention, cardiac status and so on.Result Achievement ratio of time-domain way MTWA examination is 95％. Thenormal reference value range of 95％after MTWA testing is MTWA＜37μV. TheMTWA positive rate of high risk group 45.7％is higher than the control group 4.8％(p＜0.05). The MTWA positive rate of ischemic heart disease and non-ischemic heart disease are 23.2％,22.50％(p＞0.05). Average 10±1.28 month follow-up, there isno cardiovascular events happening in control group, there are 11 death in high riskgroup, including 7 SCD (MTWA positive rate is 81.8％, 85.7％respectively), 17 casesof MVA (MTWA positive rate is 88.2％), in 9 cases of syncope (MTWA positive rateis 77.8％), 21 cases of hospitalization during the follow up (MTWA positive rate is85.7％). There is no significant deviation of above mentioned events between MTWApositive ischemic heart disease and MTWA positive non-ischemic heart disease (p＞0.05). Using logistic regression analysis to predict all cause of death, risk factors inturn are MTWA positive, a history of myocardial infarction and LVDd≥60mm.Onlythe MTWA positive is related to SCD. The factors related to MVA in turn are MTWApositive, LVEF≤35％, a history of cardiopulmonary resuscitation and a history ofsyncope. The factors related to hospitalization are MTWA positive, LVEF≤35％.High risk group included the cardiovascular events subset and the non-happeningsubset, the mean of MTWA examination values are 52.56μV and 31.48μVrespectively (P＜0.01). MTWA positive predict MVA's sensitivity is 88％, specificityis 60％, PPV is 23％, NPV is 97％(P＜0.01), except specificity are all better than thenoninvasive indicators including LVEF, SDNN, NSVT, QRS, OTc. MTWA positiveand LVEF≤35％are the independent indicators for predicting MVA (P＜0.01).Combined using MTWA positive and LVEF≤35％for predicting MVA's sensitivity is91％, PPV is 27％, NPV is 98％are better than only using any one of them. MTWApositive rate of 41 Implantable Cardioverter-Defibrillator (ICD) patients are 68.3％.MTWA positive rate of MVA happened and received ICD automatic shock duringfollow up are 87.5％. In high risk group, MTWA positive get more anti-arrhythmicdrug treatments than MTWA negative (P＜0.01). After three months interventiontreatment in high risk group, MTWA examination value became lower, has the trendof changing to negative, LVEF and NYHA class are improved (p＜0.05). Throughlogistic regression analysis, found that the effective interventions for MTWA valuebecame lower in turn are PCI, beta-blockers and other anti-arhythmia drugs.Conclusion①The normal reference value range of time-domain way MTWA examination for Chinese people is MTWA＜37μV.②The MTWA positive rate oforganic heart disease patients are higher than the healthy person, among heart diseasepatients, the cardiovascular events happening in the MTWA positive are morefrequent than the MTWA negative.③Both of MTWA and LVEF have independentpredict value for MVA, MTWA has a better value for SCD prediction than LVEF. Nomatter the basic cardiopathy is ischemic heart disease or non-ischemic heart disease,the sensitivity and specificity of MTWA are higher than other non-invasive riskstratification indicators.④Combination of MTWA and LVEF≤35％could raise thepredict value.⑤MTWA positive could become one of the preliminary screeningindicators of ICD implantation.⑥MTWA could use to evaluate the effect of SCDhigh risk group intervention treatment.⑦Time-domain way MTWA examinationhave characteristics of no wound, easy operate, high efficiency, easy repeat,reasonable test fee, etc. has a pleasant generalize and application prospect.