Clinical relevance of intracranial high intensity transient signals in patients following prosthetic aortic valve replacement

Abstract

Objectives: There has been frequent report on transcranially detected microembolic signals (HITS) following cardiac surgery using extracorporeal bypass support. The clinical relevance of HITS, however, has yet to be clarified. The incidence of thromboembolic events is increased following mechanical heart valve replacement. The purpose of this study was to quantify postoperative HITS after implantation of two types of prosthetic aortic valves and to compare both types of mechanical valves with respect to the generation of HITS. In addition, HITS rates were correlated with clinical, echocardiographical and laboratory findings. Methods: Forty-two patients following implantation of either a Sorin Biomedica^® heart valve (n=22, group A) or a Tekna Duromedics^® mechanical valve (n=20, group B) were examined. A group of ten healthy volunteers served as control. Clinical, echocardiographic, carotid artery duplex and laboratory examinations were performed in all patients. A 60 min bilateral transcranial doppler monitoring of the medial cerebral artery (MCA) was also carried out in order to evaluate cerebral blood flow. Results: In group A 14 of 22 patients were positive for HITS (53%), with an average of 16.4±19 HITS/pt.h. In group B 15 of 20 patients were HITS positive (75%) with an average amount of 14.4±24 HITS/pt.h. The incidence of HITS was not significantly different between the two groups. No correlation was seen between the HITS-rate/h and neurological findings, duplex sonographic results, mechanical valve size and anticoagulation regimen (P≫0.05). However, a negative correlation was observed between patient age and HITS-rate (P=0.02) as well as between the NYHA degree and HITS-rate (P=0.018). The HITS-rate also correlated with postoperative time (P=0.042). No HITS were detected in the control group. Conclusions: HITS do not correlate with the individual clinical status and, thus, cannot predict the occurrence of neurological deficits in patients following mechanical aortic valve implantation.