MECHANISMS OF REGIONAL ISCHEMIC CHANGES DURING DIPYRIDAMOLE-ECHOCARDIOGRAPHY IN PATIENTS WITH SEVERE AORTIC-VALVE STENOSIS AND NORMAL CORONARY-ARTERIES

Objective-Vasodilator stress echocardiography can cause myocardial isc haemia in patients with severe aortic valve stenosis and angiographica lly normal coronary arteries. The aim of the study was to determine th e mechanism of ischaemia in this clinical model. Methods-The study gro up comprised patients with severe aortic valve stenosis and normal cor onary arteries: 25 patients (17 males, eight females; age 63 (SD 11) y ears) underwent a high dose (up to 0.84 mg/kg over 10 min) dipyridamol e echocardiography test both before (2-4 d) and after (10-15 d) aortic valve replacement. Mean aortic pressure gradient was 96 (15) nun Hg, with a left ventricular mass index of 228 (49) g/m(2). The dipyridamol e echocardiography test was well tolerated and interpretable in all pa tients. Results-Dipyridamole infusion induced chest pain in seven pati ents before and in no patient after surgery (28 v 0%, P < 0.01), ST se gment depression in 12 patients before and two after surgery (48 v 8%, P < 0.01), and a transient regional dyssynergy in 10 patients before and two after surgery (40 v 8%, P < 0.01). In the preoperative evaluat ion, patients with an echocardiographically positive dipyridamole echo cardiography test were comparable with patients with negative test as far as left ventricular mass index [240 (67) v 230 (64) g/m(2), NS] an d mean aortic pressure gradient [95 (22) v 92 (21) mm Hg, NS] were con cerned. When compared to the preoperative assessment, the resting echo assessment in the postoperative evaluation showed unchanged values of left ventricular mass index [pre 228 (49) g/m(2) v post 220 (36) g/m( 2), NS], but markedly decreased values of mean aortic gradient [pre 95 (15) mm Hg v post 22 (5) mm Hg, P < 0.01] and left ventricular wall s tress index [pre 134 (30) g/cm(2) v post 89 (19) g/cm(2)]. Conclusions -Dipyridamole echocardiography is a suitable clinical technique for as sessing the ischaemic vulnerability of the left ventricle in severe ao rtic valve stenosis with angiographically normal coronary arteries. Th e frequent disappearance of the ischaemic response early after aortic valve replacement suggests that haemodynamic factors such as compressi ve diastolic wall stress or afterload reduction are important componen ts of myocardial ischaemic vulnerability under these circumstances.