Electrocardiographic ST Depression Research Articles

対側冠動脈病変の有無からみた心筋虚血時心電図ＳＴ上昇，下降の成立機序

心筋虚血でST上昇, 下降に区分される機序を対側冠動脈病変の有無から検討した.雑種犬35頭で左冠動脈前下行枝 (LAD) を灌流し, この流量を平均18.4±1.8から5.3±1.4ml/minまで減らしたとき, 心表面心電図111個中109個ではST上昇, 2個でST下降が起った (実験A) .このとき左廻旋枝 (LCX) には虚血部へ血流供給をしたと考えられる代1賞性血流増大があった.LCXにcritical stenosisを作った後でLAD流量を15.5±1.5から6.2±1.2ml/minへ低下させたとき, 111個中11個にST下降がみられるようになった.この際, 大動脈圧とLCX流量は低下し, globa lischemiaが生じた (実験B) .実験Cでは, LADとLCX間の血流供給を遮断する目的で自由壁を絹糸で縫合した後に, LAD流量を漸減すると, 90個中48個にST下降がみられた.Aでは大幅な血流低下で初めて貫壁性虚血, ST上昇となり, 対側から副血行のないB, Cではわずかの血流低下で心内膜下虚血が起り, ST下降がみられ易くなったと考えられた.

Early postoperative assessment of coronary artery bypass surgery using nuclear left ventriculography and atrial pacing.

Nuclear ventriculography (MUGA) was performed in 22 patients at rest and during the stress of right atrial pacing 6 to 8 days after coronary artery bypass surgery. In 7 patients the MUGA-atrial pacing test was positive for ischemia with chest pain, electrocardiographic ST depression and/or a decrease in global left ventricular ejection fraction of greater than 10%. All 7 patients subsequently developed angina pectoris with a positive treadmill test (performed at a median time of 14 months after operation). In 15 patients, the early postoperative MUGA-atrial pacing test was negative. In this group, 3 patients subsequently developed angina pectoris with a positive treadmill test in one. The sensitivity of the 'one week' early postoperative MUGA-atrial pacing in the identification of patients with residual myocardial ischemia was high (88% for positive GXT, p less than 0.0001; 70% for chest pain, p less than 0.005) with 100% specificity. The early postoperative MUGA scan was also useful in predicting later shortness of breath on exertion and there was a significant correlation between the early resting ejection fraction and the exercise capacity of the patient subsequently. The information obtained from an early postoperative MUGA-atrial pacing study may have far-reaching and important practical application in selecting patients for early recatheterization, possible fibrinolysis and/or possible cardiac reoperation.

Comparison of supine and erect bicycle exercise electrocardiography in coronary heart disease: Accentuation of exercise-induced ischemic ST depression by supine posture

Exercise-induced electrocardiographic ST depression was compared during supine and erect graded bicycle exercise in 43 patients with chest pain but no prior myocardial infarct; all had ≥1 mm of ST depression during either erect or supine exercise; 16 had multivessel, 24 had 1-vessel and 3 had no coronary artery disease. Supine exercise used 4 minutes/stage and erect exercise used either 4 minutes or 3 minutes/stage with identical graded work loads for both postures. Chest pain occurred in 31 patients during erect and in 29 during supine exercise. ST depression was ≥1 mm in 28 patients during erect exercise and in all 43 during supine exercise (p <0.001); mean maximal ST depression was 1.3 ± 0.2 mm during erect and 2.6 ± 0.2 mm during supine exercise (p <0.001). Maximal work load was higher during erect than supine exercise (745 ± 32 versus 678 ± 32 kpm/min; p <0.001). The accentuation of ST depression by supine posture was not attributable to the changes in heart rate, rate-pressure product or mean blood pressure during supine versus erect exercise. In the 10 patients who had 2 erect bicycle tests using work load durations of 3 and 4 minutes, the maximal ST depression was not significantly different (erect 3 minutes 1.3 ± 0.5 mm and erect 4 minutes 1.4 ± 0.4 mm). In 7 patients who also had a maximal treadmill exercise test, the maximal ST depression was significantly greater during supine exercise (2.3 ± 0.4 mm) than during either an erect bicycle test (0.6 ± 0.4 mm) or treadmill exercise (0.7 ± 0.4 mm) (p <0.05). Supine posture should be considered as an important potentiator of exercise-induced myocardial ischemia whem comparing indicators such as electrocardiography, radionuclide ventriculography and thallium-201 myocardial perfusion imaging during exercise.

Longitudinal survey of ischaemic heart disease in randomly selected sample of older population.

A group of 215 men and 272 women aged 62 to 90 forming a randomly-selected sample of the older population was studied by cardiovascular survey methods and followed for 5 years. The 5-year mortality of 28 per cent was related to age and was higher in men. Ischaemic heart disease was the certified cause of 28 per cent of the deaths. Mortality was greater in those with systolic hypertension. Among electrocardiographic features ST depression, T inversion, and atrial fibrillation increased overall and ischaemic heart disease mortality independently of their association with age. A positive response to an angina and infarct questionnaire was poorly related to subsequent mortality. Re-examination of 72 per cent of 5-year survivors was possible. Systolic and diastolic blood pressures were significantly lower and the frequency of electrocardiographic abnormalities, particularly left axis deviation, left ventricular hypertrophy, and ST and T wave changes, was increased.