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Updated: Sep 2, 2026
Noninvasive Determination of Vortex Formation Time Using Transesophageal Echocardiography During Cardiac Surgery
Published on: November 28, 2018
[High-intensity transcranial Doppler signals in patients wearing heart valve prostheses: a prospective study]
A D'Alfonso1, A D Milano, R Codecasa
1Dipartimento di Cardiologia, Angiologia e Pneumologia, Università di Pisa.
Insights
Mechanical prosthetic heart valves are a significant risk factor for high-intensity transient signals (HITS), indicating asymptomatic microemboli. However, these signals do not appear to correlate with neurological events post-surgery.
Area of Science:
- Neurology
- Cardiovascular Surgery
- Medical Imaging
Background:
- Transcranial Doppler sonography (TCD) detects high-intensity transient signals (HITS) in patients with prosthetic heart valves, suggesting asymptomatic cerebrovascular microemboli.
- The origin and clinical significance of HITS, whether gaseous or corpuscular emboli, remain unclear.
Purpose of the Study:
- To investigate the incidence and predictive factors of HITS in patients undergoing prosthetic heart valve procedures.
- To assess the relationship between HITS and postoperative neurological events.
Main Methods:
- Prospective evaluation of 71 patients undergoing heart valve replacement or repair using TCD.
- Clinical assessments and continuous echo-Doppler studies of carotid and middle cerebral arteries were performed preoperatively and at 1 week, 3 months, and 12 months post-procedure.
Main Results:
- No HITS were detected preoperatively. At one week post-surgery, 35% of patients had HITS, predominantly those with mechanical prostheses (65%).
- HITS were exclusively observed in patients with mechanical prostheses who had positive TCD findings at one week.
- No neurological symptoms were reported during the postoperative evaluation; mechanical prosthetic valves were the sole independent predictor of HITS.
Conclusions:
- Mechanical prosthetic valves are a clear risk factor for HITS development.
- HITS detected via TCD appear unrelated to postoperative neurological events in this patient cohort.
- Further research is needed to associate TCD with methods for characterizing embolic material to enhance clinical utility.
Background:
Transcranial Doppler sonography (TCD) of the middle cerebral arteries in patients with prosthetic heart valves reveals high-intensity transient signals (HITS) and can detect asymptomatic cerebrovascular microemboli. Both the nature of the underlying embolic material (either gaseous or corpuscular) and its clinical significance remain uncertain.
Methods:
Seventy-one patients undergoing heart valve replacement (n = 63) or repair (n = 8) from June 1996 to June 1998 were prospectively evaluated preoperatively and one week, 3 months and 12 months after valve replacement using TCD. At each follow-up interval, clinical assessment was aimed at detecting neurological events. Furthermore, continuous echo-Doppler study of the carotid arteries and TCD of the middle cerebral arteries for a 30-minute period during each following visit was carried out.
Results:
No HITS were recorded preoperatively in any patient. At one week, HITS were detected in 25 patients (35%): 22 (65%) of these had received a mechanical prosthesis and three (10%) a bioprosthesis. No HITS were recorded in patients with mitral repair. HITS were subsequently detected only in patients with mechanical prosthesis with a positive TCD at one week, the mean number of HITS per patient being 7 +/- 18 at 3 months and 8 +/- 24 at 12 months. No neurological symptoms were evident in any patients during the postoperative evaluation. Multivariate analysis showed mechanical prosthetic valve to be the only independent predictive risk factor for HITS development.
Conclusions:
The role of a mechanical prosthetic valve as a risk factor in the pathogenesis of HITS appears evident. However, HITS appear to be unrelated to possible postoperative neurological events. TCD could have more specific clinical applications if associated with methods that would make it possible to ascertain the nature of various embolic materials.
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