Variation in the size of jeopardized myocardium in patients with isolated left anterior descending coronary artery disease.

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Abstract
Previous studies show considerable variation in the perfusion and function of the left ventricle at rest and during stress in patients with disease of the isolated left anterior descending coronary artery. In search of mechanisms, exercise 201Tl images in 35 such patients were obtained. None of the patients had had infarction. The exercise-induced perfusion defect size was measured as the average of the percentage of abnormal perimeter from the 3 standard projections. The perfusion defect size was smaller in the 9 patients with 50-69% stenosis than in the 26 patients with .gtoreq. 70% stenosis (10 .+-. 9% vs. 27 .+-. 15%, mean .+-. SD, P < 0.01). Among the 26 patients with .gtoreq. 70% stenosis, the perfusion defect was .ltoreq. 30% in 14 and > 30% in 12. All 14 patients with perfusion defects .ltoreq. 30% were older than 50 yr; 8 of the 12 with perfusion defects > 30% were 50 yr or younger (P = 0.0003). The severity and site of stenosis, collaterals, exercise heart rate and double product, propranolol therapy and results of exercise ECG were similar in patients with perfusion defects .ltoreq. 30% and in patients with perfusion defects > 30%. Using a stepwise regression analysis of 30 clinical, anatomic and exercise variables, only age showed a significant correlation with perfusion defect size (r = -0.58, P < 0.005). In patients with effective collaterals, the perfusion defect was smaller in patients older than 50 yr than in patients age 50 yr or younger (14 .+-. 7% vs. 41 .+-. 8%, P < 0.001). The perfusion defect is small in patients with < 70% stenosis of the left anterior descending coronary artery, but varies considerably in patients with .gtoreq. 70% stenosis. Age is the chief determinant of perfusion defect size in patients with similar left anterior descending coronary artery anatomy and exercise variables. Age and, conceivably, the duration of disease may affect the functional maturity of collaterals. Left anterior descending coronary artery lesions may well put into risk > 30% of the heart muscle in a great number of patients. This phenomenon is significantly more common in patients younger than age 50 yr.