D. Tzivoni et S. Maybaum, ATTENUATION OF SEVERITY OF MYOCARDIAL-ISCHEMIA DURING REPEATED DAILY ISCHEMIC EPISODES, Journal of the American College of Cardiology, 30(1), 1997, pp. 119-124
Objectives. The purpose of this study was to assess whether the severi
ty of myocardial ischemia would be attenuated by repeated daily ischem
ic episodes, recorded by ambulatory electrocardiographic monitoring (A
EM). Background. Repetitive ischemic episodes induced by brief coronar
y occlusions in animal experiments and in humans during balloon corona
ry angioplasty produce preconditioning, We wanted to assess whether th
is phenomenon also exists during daily ischemic episodes. Methods. Twe
nty-one patients with known coronary artery disease and ischemia on ex
ercise testing and AEM were requested to walk a distance known to have
previously caused myocardial ischemia on three consecutive occasions,
Walking time was similar to 15 min and aas followed by 5 min of rest.
Results. Mean maximal heart rate during the three walks was similar;
however, the mean maximal ST segment depression decreased significantl
y from 2.21 mm during the first walk to 1.61 mm and 1.43 mm, respectiv
ely, an the second and third walks (p = 0.001). Ischemia duration was
also significantly reduced on the second and third walks by 56% from 5
14 to 228 and 254 s, respectively (p = 0.012), The heart rate at onset
of ischemia (ischemic threshold) increased from 99 beats/min on the f
irst walk to 101 beats/min on the second walk and to 106 beats/min on
the third walk (p = 0.058). Conclusions. This study demonstrated atten
uation of myocardial ischemia with an associated increase in ischemic
threshold in patients with repeated and adjacent ischemic episodes. Th
is form of myocardial protection is likely to be encountered in patien
ts during ordinary activity and may represent the clinical counterpart
of myocardial preconditioning. (C) 1997 by the American College of Ca
rdiology.