QT/RR relationship in patients after remote anterior myocardial infarction with left ventricular dysfunction and different types of ventricular arrhythmias.
BACKGROUND
QT/RR relationship was found to be both rate-dependent and rate-independent, what suggests the influence of autonomic drive and other not-autonomic related factors on it. The steeper QT/RR slope in patients after acute myocardial infarction (MI) was described, but the relationship to ventricular arrhythmias is unknown. The purpose of this study was to calculate differences in QT/RR relationship in patients after remote anterior MI with left ventricular dysfunction and different types of ventricular arrhythmias.


METHODS
The cohort of 95 patients (age: 63 +/- 11 years, LVEF: 35 +/- 9%) with previous anterior MI (mean 1.1 years) was divided into two well-matched groups-50 patients without episodes of ventricular tachycardia (VT) or ventricular fibrillation (VF) (NoVT/VF: 39 males, 64 +/- 12 years, LVEF 37 +/- 8%) and 45 patients with VT and/or VF (all with ICD implanted) (VT/VF: 35 males, 62 +/- 10 years, LVEF 34 +/- 10%). No true antiarrhythmics were used. QT/RR slope was calculated from 24-hour Holter ECG for the entire recording (E), daytime (D) and nighttime (N) periods.


RESULTS
Groups did not differ in basic clinical data (age, LVEF, treatment). QT/RR slopes were steeper in VT/VF than in NoVT/VF group in all analyzed periods: E - 0.195 +/- 0.03 versus 0.15 +/- 0.03 (P < 0.001), N - 0.190 +/- 0.03 versus 0.138 +/- 0.03 (P < 0.001) and D - 0.200 +/- 0.04 versus 0.152 +/- 0.03 (P < 0.001). No significant day-to-night differences were found in both groups.


CONCLUSIONS
Steeper QT/RR slope and complete lack of day-to-night differences in VT/VF patients show inappropriate QT adaptation to the heart rate changes. The prognostic significance of this parameter needs prospective studies.
Szydlo
Krzysztof
K
I Department of Cardiology, Silesian Medical University, Katowice, Poland. krzysztofszydlo@onet.eu
Trusz-Gluza
Maria
M
Wita
Krystian
K
Filipecki
Artur
A
Orszulak
Witold
W
Urbanczyk
Dagmara
D
Krauze
Jolanta
J
Kolasa
Jaroslaw
J
Tabor
Zbigniew
Z
D001145:Arrhythmias, Cardiac / Q000503:physiopathology*; D002940:Circadian Rhythm; D015331:Cohort Studies; D015716:Electrocardiography, Ambulatory / Q000379:methods / Q000706:statistics & numerical data*; D005260:Female; D006339:Heart Rate; D006801:Humans; D008297:Male; D008875:Middle Aged; D009203:Myocardial Infarction / Q000503:physiopathology*; D017180:Tachycardia, Ventricular / Q000503:physiopathology; D018487:Ventricular Dysfunction, Left / Q000503:physiopathology*; D014693:Ventricular Fibrillation / Q000503:physiopathology