Subclinical embolism in patients undergoing cardiac valve implantation and coronary artery bypass surgery

Patients undergoing prosthetic valve insertion and coronary arterybypass surgery were examined with transcranial Doppler ultrasound, recentlyshown to be capable of detecting continuing subclinical emboli in patientswith embolic sources. In 30 patients examined at least 1 year after valvesurgery, and in whom warfarinisation was stable within defined limits, 20of 24 patients (83%) with mechanical valves and 3 of 6 patients (50%) withporcine valves had embolic signals. In a serial preoperative andpostoperative study in a further 30 patients, of whom 29 had native orbioprosthetic valves, only the one patient with a previous mechanicalmitral valve prosthesis had embolic signals preoperatively. The incidenceof embolic signals increased to 9 (30%) on the first postoperative day, and20 (67%) on day 5. In a similar serial study in 25 patients undergoingcoronary bypass surgery, 8 (32%) had preoperative embolic signals, whichwere explicable by cardiac and/or carotid disease in 6 cases. The embolussignal incidence and count did not increase postoperatively in this group.No embolic signals were found in 15 volunteer controls. The resultsindicate that prosthetic valves cause continuing microembolisation, detectable by transcranial Doppler; coronary artery bypass cases may haveincidental embolic signals which are unaffected by cardiac surgery. Thisnew application of Doppler ultrasound may improve the clinical assessmentof embolic risk of new prosthetic valve types and deserves furtherexamination