The purpose of this study was to answer the following questions: 1) are isovolumic contraction and relaxation affected in a different way by LAD occlusion? 2) Does proximal and distal LAD coronary occlusion induce different changes in isovolumic contraction and relaxation? In 22 pigs, LAD coronary artery was dissected free right after the first or third diagonal branch and occluded by ligation. The following variables were evaluated: left ventricular systolic and end-diastolic pressure; peak - and + dP/dt, mean arterial and pulmonary pressure. All our data were obtained in the first minute following the occlusion.(ABSTRACT TRUNCATED AT 250 WORDS)