Diagnosis of coronary stenosis by two-dimensional echographic study of dysfunction of ventricular segments during and immediately after pacing

The adequacy of two-dimensional echocardiography during right atrial pacing for the detection and characterization of coronary artery stenosis was examined in 10 closed chest dogs. Pacing at successively higher rates up to 210 beats/min was carried out in the control state and again during a 70% left anterior descending coronary artery stenosis induced with intracoronary plugs. Left ventricular short-axis echographic cross sections were obtained at several levels of the left ventricle. After computer-aided standardized subdivision, contractile function of the global section and its subsegments was characterized by computed systolic fractional area change percent and wall thickening percent. Ventricular segments supplied from the site of the 70% coronary stenosis were delineated in a low papillary level cross section by a myocardial contrast echographic technique, and these segments demonstrated significant dysfunction during pacing at 150 to 210 beats/min. Echographic observation of the involved segments immediately after pacing revealed a maximal depression of function 5 seconds after pacing, equivalent to dysfunction at peak pacing, with function returning to control levels within about 2 minutes. Both maximal pacing and early postpacing studies facilitated satisfactory discrimination of ischemic from normally perfused myocardial segments. These experiments show that right atrial pacing study with quantitative two-dimensional echocardiography may serve to detect and assess a coronary stenosis associated with minor or no cardiac dysfunction in the rest state.