INFLUENCE OF PACING-INDUCED MYOCARDIAL-ISCHEMIA ON LEFT ATRIAL REGURGITANT JET - A TRANSESOPHAGEAL ECHOCARDIOGRAPHIC STUDY

Objectives. We investigated the influence of pacing-induced myocardial ischemia on systolic regurgitant jet in the left atrium, using simult aneous transesophageal echocardiography and transesophageal atrial pac ing. Background. In vitro studies have shown that ischemia induced mit ral regurgitation may occur as a result of mitral leaflet malcoaptatio n or (global) left ventricular dysfunction. However, no transesophagea l echocardiographic study has thus far been performed to demonstrate t he mechanism and extent of mitral regurgitation during myocardial isch emia in patients. Methods. In 24 patients (mean [+/-SD] age 57 +/- 10 years) with (15 patients) and without (9 control subjects) coronary ar tery disease, heart rate, blood pressure and systolic regurgitant jet were assessed before and immediately after pacing. Pacing was increase d stepwise up to 160 beats/min to provoke wall motion abnormalities wh ile the left ventricular short axis was monitored at the midpapillary muscle level. Other variables obtained before and at peak pacing inclu ded left ventricular end-diastolic and end systolic areas and left ven tricular end diastolic and end-systolic endocardial segmental lengths. Results. Heart rate and blood pressure before and after pacing were n ot significantly different in control subjects or in patients. At base line, a jet was present in all but three control subjects. New or incr eased anterior or posterior wall motion abnormalities were observed du ring pacing in seven and eight patients, respectively. End-systolic le ft ventricular areas and segment lengths were significantly reduced in control subjects compared with patients with coronary artery disease at peak pacing (p < 0.05). The increase in systolic regurgitant jet wa s significantly greater in patients (2.0 +/- 1.1 to 3.1 +/- 1.8 cm(2) vs, 0.7 +/- 0.7 to 0.9 +/- 0.9 cm(2) [after pacing], p < 0.01). This e ffect was greater in patients with posterior than with anterior wall m otion abnormalities (3.5 +/- 1.6 vs. 2.1 +/- 1.2 cm(2) [after pacing], p < 0.05). Conclusions. Quantitative changes in geometry and function of the left ventricle caused by pacing induced myocardial ischemia au gments systolic regurgitant jet size. An increase in the jet during at rial pacing is associated with new or increased mall motion abnormalit ies, especially of the posterior wall. Pacing-induced anterior wall mo tion abnormalities appear not to be related directly to an increase in the jet.