Stable coronary artery dissease extent and severity of coronary artery dissease of the relationship between the P-wave dispersion and QT dispersion

2. ABSTRACT Introduction: Coronary artery disease (CAD) is a leading cause of morbitiy and mortality among cardiovascular diseases. Atherosclerosis is a systemic, progressive and inflamatory disease. Among these patients, increased incidence of sudden cardiac death and serious arrhythmias are the most important predictors of cardiovascular risk. It is shown in several studies that CAD is an independent risk factor for atrial fibrillation (AF). Atrial fibrillation is seen more frequently in stable coronary artery disease, as well in patients with recent acute coronary syndrome, than general population. Among the clinical presantations of coronary artery disease, there are silent ischemia, stable angina pectoris, unstable angina pectoris, myocardial infarction (MI), heart failure and sudden cardiac death (SCD). The most important cause of sudden cardiac death is arrhythmia which presents as ventricular tachycardia or fibrillation. The patients with long QT in electrocardiography have nonhomogenous changes in action potentials and these changes facilitate the development of ventricular fibrillation by causing early and late repolarizations. QT dispersion (QTd) is a parameter that shows the heterogenity of ventricular repolarizations, and it is derived from noninvasive electrocardiogram. Increased QT dispersion is found to be associated with serious arrhytmia and sudden cardiac death in ischaemic and nonischaemic patient groups. QTd is defined as the difference between the longest and the shortest QT on ECG, if QTc (corrected QT) is used, the obtained valve is defined as corrected QTd (QTcd). It is known that QT dispersion shows the regional heterogeneity in ventricular repolarization and is an important predictor of sudden cardiac death. Also, QT dispersion rate (QTdr) which is defined as the ratio of QTd to the length of cardiac cycle, is shown to be more valvable parameter for prediction of ventricular arrhythmias. Nonhomogenous myocardial repolarization time is explained with the regional conduction slow down or changes in conduit lines, causing delays in action potentials. More QTd means less ventricular repolarization homogeneity, indicating increased myocardial instability. This can cause serious ventricular arrhythmias and sudden cardiac death by the effects of nonhomogenous conduction velocities in different regions of myocardium or reentrant repolarization mechanism. Aim: To investigate the relationship of coronary artery disease severity and diffusiveness with the electrocardiograhic parameters such as PDD, QTd, QTcd, QTdr in patients with stable coronary artery disease and preserved left ventricular ejection fraction, and to determine whether these parameters can be used as predictors of coronary artery disease severity. Methods: A group of 250 patients that admitted to cardiology polyclinic without any cardiovascular events or unstability, but have the probability of having stable coronary artery disease are taken into the study. Patients between the ages of 35-70, and without the history of any known cardiovascular events are included. More than 50 % narrowing in coronary arteries in coronary angiography is defined as coronary artery disease. According to this, the patients are divided into 5 groups such as group 1 ( normal coronary arteries ), group 2 (noncritical stenosis with less than 50 % narrowing ), group 3 ( one major vessel disease with more than 50% stenosis ), group 4 ( two major vessel disease with more than 50% stenosis ), group 5 ( three major vessel disease with more than 50% stenosis ). Coronary disease severity is calculated with gensini score index, which is obtained from the stenoses in the coronary angiography. The pre-angiography ECGs are obtained from the patient files in the archive and evaluated with the condition of being able to measure the parameters in 9 of the 12 derivations. All measurements are performed manually with a magnifier. Results: The age of patients in the study was between 35 and 70 ( mean age: 57,88 ± 8,49 ). Gensini score was between 0 and 178 ( mean score: 120,46 ± 155,72 ). 77 ( 30,8% ) of the patients were female and 173 ( 69,2% ) were male. 139 ( 55,6% ) had hypertension and 90 (36% ) have diabetes mellitus. As CAD severty which is calculated with Gensini score increases, the values of QTd, QTcd, QTdr, PDD and Pmax which are obtained with electrocardiography. Conclusion: In stable coronary artery disease patients with preserved left ventricular functions, with increasing coronary artery disease severity. QTd, QTcd, QTdr, PDD, Pmax values also increase.