BACKGROUND Transmyocardial ischemia is manifested as ST-segment elevation (STE). We examined acoustic cardiographic indices of STE that occur during percutaneous coronary intervention (PCI). METHODS Of 83 patients undergoing coronary angiography, 25 underwent PCI, including 5 who developed STE. Continuous 12-lead ECG and computerized acoustic cardiographic heart sound analysis were performed during PCI. Intensities of the heart sounds (S1 to S4), diastolic time (from S2 to S1), and systolic time intervals (S1 to S2) were recorded. RESULTS As STE increased, there was no change in heart rate or systolic time. Contractility decreased, with an increase in S3 intensity and a reduction in S1/S2 ratio. Left ventricular stiffness increased, reflected by an increase in S4 intensity. CONCLUSIONS As transmyocardial ischemia worsened during progressive STE, acoustic cardiographic indices reflected impaired contractility and increased ventricular stiffness. In particular, the S4 was most predictive of increasing degrees of STE. These findings have implications for assessment of transmyocardial ischemia in patients with ECG findings that confound ST segment interpretation.