INTRACRANIAL HIGH-INTENSITY TRANSIENT SIGNALS AFTER HOMOGRAFT OR MECHANICAL AORTIC-VALVE REPLACEMENT

Objective. Comparison of the occurrence, intensity and rate of high-in tensity transient signals (HITS), measured in both middle cerebral art eries by transcranial Doppler ultrasound (TCD) after mechanical or hom ograft aortic valve implantation. Experimental design TCD monitoring w as performed by means of a pulsed Doppler ultrasound with two 2 MHz pr obes, stabilized on the head and directed at the middle cerebral arter y. Setting. Outdoor patients after aortic valve replacement in a unive rsity hospital. Patients. The study cohort comprised a random transver se sample of patients and included 20 patients with a mechanical aorti c valve and 20 with a homograft aortic valve. Comparisons were made wi th 20 admitted control patients. Interventions. No interventions. Meas ures. No significant number of HITS were expected in the homograft gro up and a limited number in the mechanical valve group. Results. HITS w ere detected in more patients after implantation of a mechanical aorti c valve prosthesis compared with a homograft aortic valve (16 versus 8 , p=0.02). Nevertheless, more patients with a homograft aortic valve s howed HITS than the control patients (8 versus 1, p=0.02). The mean nu mber of BITS in the mechanical prosthesis group was higher than in the homograft group (3, range 0-18 versus 13, range 0-70, p<0.05). HITS i n patients with mechanical prostheses had a higher amplitude than HITS in patients with homograft aortic valves (p<0.0001). Focal neurologic al deficit (FND) was diagnosed in 9 patients (mechanical prosthesis 6 versus homograft 3, ns). Conclusions. HITS commonly occur both in pati ents with a mechanical aortic valve and in patients with a homograft a ortic valve. HITS occur significantly less often, at a lower rate and with a lower intensity in patients with homograft aortic valve compare d with patients with a mechanical aortic valve. Future studies should elucidate the nature and prognostic significance of HITS and their rel ationship with thromboembolic events.