Background: Ventricular repolarization abnormalities are associated with increased risk of sudden cardiac death in patients after myocardial infarction. The aim of this study is to assess QT dynamicity - QT/RR relationship - in patients after myocardial infarction and its contribution to risk stratification of sudden cardiac death.
Methods: In a group of patients with diagnosis of acute myocardial infarction a long term ECG recording was performed 48-72 hours after myocardial infarction (MARS Unity Workstation, GE Medical Information Technologies). Patients with unstable circulation, artificial pulmonary ventilation, left bundle brach block, atrial fibrillation and paced rhythm were excluded. Analysis of QT dynamicity was performed by QT Guard software (GE Medical Information Technologies). QT/RR relationship is expressed by linear regression as QT = = aRR + b where "a" is termed "slope".
Results: Assessment of QT dynamicity was possible in 215 ECG recordings. In 6-month follow-up 2 patients died and another was successfully resuscitated for primary ventricular fibrillation. Six-month mortality resp. mortality + resuscitation was 0.9 %, resp. 1.4 %. Therefore statistical evaluation was not possible. In the 3 mentioned individuals the slope values were 0.333, 0.249 and 0.342.
Conclusions: Mortality of up-to-date-treated patients after myocardial infarction is low. Therefore, in such patients it is not possible to assess QT dynamicity as a risk factor in midterm follow-up. Limitation of the method is the necessity of substantial selection of patients elegible for analysis and dependance on necessary equipment.