The Acute Effects of Cigarette Smoking on the Heterogeneity of Ventricular Repolarization in Healthy Subjects: The Relationship between QT Dispersion and Coronary Flow Reserve

ABSTRACT

BACKGROUND AND OBJECTIVES: Although cigarette smoking is a known risk factor for sudden cardiac death, little is known about the effects of smoking on the heart. The QT interval and QT dispersion prolongation have been associated with a lower ventricular fibrillation threshold and the occurrence of sudden cardiac death. Smoking has an unfavorable influence on the autonomic balance and myocardial blood flow. The objective of the current study was to evaluate the relationship between the QT dispersion and coronary flow reserve (CFR) in healthy young male subjects. SUBJECTS AND METHODS: The study included a sample of 30 healthy young male cigarette smokers. The catecholamines level, QTc dispersion, heart rate variability and myocardial blood flow were measured, immediately before and 5 minutes after and during the smoking of 3 cigarettes. RESULTS: Short-term smoking caused significant increases in the serum cortisol (10.9+/-4.9 vs. 15.0+/-7.0 microgram/dL, p<0.01), serum epinephrine (0.038+/-0.026 vs. 0.046+/-0.026 ng/mL, p=0.044), heart rate (78+/-9 vs. 85+/-8 beats/min, p<0.01), maximal QTc interval (412+/-22 vs. 435+/-20 ms, p<0.01), QTc dispersion (43+/-14 vs. 62+/-17 ms, p<0.01), LFnu (68+/-9 vs. 78+/-6%, p<0.01), LF/HF (3.25+/-2.15 vs. 5.22+/-1.89, p<0.01) and peak diastolic velocity (21.7+/-3.9 vs. 23.9+/-5.5 cm/sec, p=0.005), and a decrease in the CFR (3.71+/-0.56 vs. 3.42+/-0.76, p=0.024). The change in the QTc dispersion was closely related to the change in the CFR (r=-0.357, p=0.043). CONCLUSION: The present study is the first to demonstrate that the impaired coronary flow reserve after smoking may contribute to the increased inhomogeneity of ventricular repolarization in healthy young male smokers.