الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
 |  | from | 195 |  |  |
| | | from | 195 | | |
Abstract
INTRODUCTION
Myocardial ischemia in different anqinal syndromes
and in silent episodes are due to imbalance between myocardial
oxygen demand and supply • Major determinants of
myocardial oxygen demand are heart rate, systolic blood
( aortic ) pressure. systolic wall tension. and myocardial
contractility . The major and most important factor that
determines myocardial oxygen supply ( coronary blood flow )
is the diameter (radius) of the epicardial coronary arteries
which is directly affected by atheromatous plaque ( fixed
narrowing ) and by vasomotor tone and spasm, platelet
aggregation, or thrombus formation ( dynamic narrowing )
( Maseri et al, 1985 ) •
Recently many observers have noticed a significant
circadian distribution in the frequency of myocardial ischemic
episodes throughout the day with the greatest frequency of
ST segment depression episodes occurring between the hours
of 6.00 A.M. to 12.00 noon ( Quyvumi et al, 1985; Rocco
et al, 1987; Mulcahy et al, 1988; Nademanee et al. 1988;
Barry et al, 1989; Taylor et al, 1989 ) while in variant
angina ST segment elevation episodes are most frequent
from midnight to 6.00 A.M. ( Araki et al, 1983 ) . The
circadian diurnal variation in the incidence of ischemic
episodes parallels other intrinsic neuro-endocrine physio