Silent myocardial ischemia has been inferred from transient ST-segment depression during continuous electrocardiographic monitoring. Recently, continuous ambulatory monitoring of left ventricular (LV) function using a radionuclide technique (VEST) has demonstrated episodes of significant silent LV dysfunction in the absence of electrocardiographic changes. To validate the demonstration of silent LV dysfunction with this technique, 12 men were studied during percutaneous transluminal coronary angioplasty. A total of 18 left anterior descending coronary artery balloon inflations were performed. Balloon inflations at 8 +/- 2 atm (4 to 10 atm) lasted 70 +/- 16 seconds. Seventeen of 18 inflations were associated with a decrease in LV ejection fraction greater than 0.10. Mean LV ejection fraction decreased from 0.53 +/- 0.08 to 0.28 +/- 0.11 (p less than 0.0001). In contrast, there was pain in only 10 inflations and ST-segment changes in 7. LV dysfunction was associated with a minimal increase in end-diastolic volume (4 +/- 3%, p less than 0.003), and a major increase in relative end-systolic volume (69 +/- 43%, p less than 0.001). These data suggest that continuous monitoring of LV function with the VEST can sensitively detect silent ischemic decreases in LV function occurring during angioplasty, and provide further validation of the use of this technique for detecting silent myocardial ischemia.