Transcranial Doppler monitoring of cerebral embolism in atrial fibrillation and prosthetic valves. Clinical correlations

Abstract

Transcranial Doppler (TCD) monitoring of the middle cerebral artery (MCA) permits the detection of high intensity transient signals (HITS), which are believed to represent microemboli. Non-valvular atrial fibrillation (NVAF) and prosthetic heart valves (PV) are important risk factors for embolic stroke. We evaluated both the prevalence and the frequency of microemboli in these high risk groups and the correlation with previous stroke. Sixty-six patients were monitored for 30 min on both MCAs sequentially. Twenty healthy subjects were studied as well. The total number of HITS recorded on both sides, expressed as HITS/h, was used for comparison. In NVAF patients (n = 24) the prevalence of HITS was 25%, in PV (n = 16) 62% and in those patients in whom PV coexisted with atrial fibrillation (PVAF) (n = 26), it was 42%. None in the control group showed HITS. HITS occurred significantly more frequently in PVAF (12.3/h) than in both NVAF (1.4/h, p = 0.007) and PV (2.7/h, p = 0.011), whereas there was no difference between PV and NVAF. The prevalence of HITS was not statistically different in patients with and without previous stroke, but among HITS positive patients those with previous stroke had a significantly higher HITS frequency (18.9 vs 8.5/h, p = 0.04). In conclusion, in patients with cardiac embolic sources the frequency of HITS increases from the classes with the lower (NVAF, PV) to the class with the highest (PVAF) risk factor. Patients with previous stroke have more HITS than asymptomatic ones. Therefore, embolus detection monitoring seems a promising tool in the assessment of the individual stroke risk in patients with cardiac embolic sources.