THE SHORT QT INTERVAL MEASSURED IN DIFFERENT PERIODS AFTER MYOCARDIAL INFARCTION AND MORTALITY
Introduction: There are not to much data related to connection of short QT interval and parameters of depolarisation meassured in different periods after myocardial infarction with cardiovascular risk.The analysis of risk predictors based on short-term recordings offers a a new relative simple diagnostic method based on the fact that all ECG parameters are highly genetically determinated.
Aim of the study was to determine predictive value of changes of depolarisation of left ventricle,measured during 10 minutes recording first day, seventh day and third week after onset of myocardial infarction.
Method:We analysed prognostic significance of mean RR interval,duration of P vawe,PR ,QRS,QT and QTc interval and Poincare plot as a shape as a point using only visual judgement of different forms. We included 1250 patients in the study and in follow up (survival time 71,range l-80 months).End-point of the study was total motality. All patients were tested in Neurocardiological unit using ECG with commercial software (Schiller AT-10). All parameters were analysed first day, 7th day and third week. in Coronary care unit after onset of myocardial infarction.
Results: Univariate risk predictors first day after onset of infarction were:short QT interval(p=0.002),short duration of QRS complex(p=0.000),mean RR interval <800ms,(p=0.000).Poincare plot in shape as a point was univariate predictor related to total mortality,meassured 7th day. Short QT interval and mean RR interval <800ms were also univariate risk predictors after 7th days. After the three weeks univariate risk predictors were:short QT interval,prolongation of QTc interval,mean RR<800ms and short duration of QRS complex.Mean RR interval lower than 800ms (p=0.000),was multivariate risk predictor related to total mortality.(P=0.023,RR: 2.740,CI:1.151-6.523).
Conclusion: Results have shown that onset of short QT interval in different periods after myocardial infarction as a reflexion of depolarisation abnormality is univariate predictor in early and late phase.In the late phase after myocardial infarction prolongation of QTc interval was also univariate risk predictor.This complete contrary and opposite effect is because of known methodological problem of meassurements of QT interval related to excesive changes of heart rate.