QRS complex and ST segment manifestations of ventricular ischemia: the effect of regional slowing of ventricular activation.
OBJECTIVE
Reduction or interruption of the blood supply to myocardium due to occlusion of coronary artery and consequent ischemia leads to changes of electrogenesis: changes in morphology and duration of action potentials and slowing of conduction velocity in the affected area. In this study we simulated the effects of localized changes in depolarization sequence on the QRS and ST segment patterns, using computer modeling.


METHODS
The model defines the geometry of cardiac ventricles analytically as parts of ellipsoids and allows changing the velocity of impulse propagation in the myocardium. An intramural electrically inactive area encircled by a transmural area with slowed impulse propagation velocity was introduced in anteroseptal and inferior locations. The effects on the QRS complex and the ST segment of the 12-lead electrocardiogram are presented.


RESULTS
The intramural electrically inactive area caused QRS changes typical for corresponding locations of a myocardial infarction observed in patients, which were further considerably modified by slowed impulse propagation velocity in the surrounding area. Additionally, areas of slowed impulse propagation velocity led to ST segment deviations in the "reciprocal" leads, shifting the ST segment towards the affected areas.


CONCLUSIONS
Using computer modeling we showed that the localized alteration of impulse propagation not only modified the QRS complex, but produced also changes in the ST segment consistent with changes which are usually interpreted as the effect of "injury current".
International Laser Center, Bratislava, Slovak Republic; Institute of Pathophysiology, Medical Faculty, Comenius University, Bratislava, Slovak Republic. Electronic address: bacharova@ilc.sk.
Ljuba
L
Bacharova
Vavrinec
V
Szathmary
Anton
A
Mateasik
D003198:Computer Simulation; D006329:Heart Conduction System / Q000503:physiopathology*; D006352:Heart Ventricles / Q000503:physiopathology*; D006801:Humans; D008955:Models, Cardiovascular; D009200:Myocardial Contraction; D017202:Myocardial Ischemia / Q000503:physiopathology*; D018754:Ventricular Dysfunction / Q000503:physiopathology*
Myocardial infarction; QRS complex; Regional ischemia; ST segment deviation; Slowed ventricular activation