Sudden cardiac death victims after myocardial infarction had a significantly steeper 24-hour mean QT/RR slope compared to normal subjects (0.15 vs 0.09, P=0.008).
Case-Control (n=42)
Patients who suffer sudden cardiac death after myocardial infarction exhibit abnormal repolarization dynamics, characterized by longer QT intervals and impaired QT adaptation to RR interval variations.
Tasa de eventos absoluta: 0.15% vs 0.09%
valor p: p=0.008
Background: Abnormalities in the adaptation of the QT interval to changes in the RR interval may facilitate the development of ventricular arrhythmias. Methods: This study sought to evaluate the dynamic relation between the QT and RR intervals in patients after acute myocardial infarction. The study population consisted of 14 patients after myocardial infarction (age 60 ± 7 years, 12 men) who died suddenly (SCD victims) within 1 year after the myocardial infarction and 14 pair‐matched age, sex, left ventricular ejection fraction, infarct site, thrombolytic therapy) patients who remained event‐free after myocardial infarction (Ml survivors) for at least 3 years. Fourteen normal subjects were studied as controls (age 55 ± 9 years, 11 men). QT and RR intervals were measured on a beat‐to‐beat basis automatically with a visual control from 24‐hour ambulatory ECGs using Reynolds Pathfinder 700. Mean hourly values of the QT/RR slope (QT =α+βRR) and corrected QT interval at 1000 ms of RR interval (QT 1s ) were derived for each subject using an inhouse program (QT 1s =α+1000β). The dynamics of the QT/RR slope and QT 1s were assessed on the basis of hourly mean values. The circadian rhythm of ventricular repolarization (QT 1s and QT/RR slope) was examined by harmonic regression analysis. Results: There was a trend towards a significant difference in 24‐hour mean value of QT 1s between study groups (408 ± 26 ms vs 381 ± 43 ms and 386 ± 22 ms, P = 0.06), and a significant difference was found between SCD victims and normal subjects (408 ± 26 vs 386 ± 22 ms, P = 0.02). The QT 1s differed significantly between study groups (P = 0.038) only during the day time (09:00–19:00 hour), when QT 1s was significantly longer in SCD victims than in normal subjects (409 ± 33 vs 380 ± 27 ms, P = 0.02) and tended to be longer than in Ml survivors (409 ± 33 vs 379 ± 42 ms, P = 0.08). The 24‐hour mean value of QT/RR slope was significantly different between study groups (P = 0.04), with a significantly steeper slope in SCD victims than in normal subjects (0.15 ± 0.07 vs 0.09 ± 0.02, P = 0.008). During day time, the QT/RR slope differed significantly between study groups (P = 0.04), while the difference was less marked at night (P = 0.08). The slope was significantly steeper in SCD victims than in normal subjects during both day and night (P < 0.05). A marked circadian variation of QT 1s was observed in normal subjects, which was blunted in Ml survivors and SCD victims. Conclusions: Abnormal repolarization behaviors, characterized by longer QT 1s and impaired adaptation of QT to variations in RR intervals, were found in SCD victims. Hence, lethal ventricular tachyarrhythmias might be provoked by the altered repolarization dynamics in patients after myocardial infarction. A.N.E. 1999;4(3):286–294
Yi et al. (Thu,) conducted a case-control in Myocardial Infarction (n=42). 24-hour ambulatory ECG monitoring vs. Event-free MI survivors and normal subjects was evaluated on 24-hour mean value of QT/RR slope (p=0.008). Sudden cardiac death victims after myocardial infarction had a significantly steeper 24-hour mean QT/RR slope compared to normal subjects (0.15 vs 0.09, P=0.008).