Monitoring of cerebral high intensity transient signals during catheter interventions and surgery for congenital heart disease in infants using NeoDoppler

Background: There is a risk of gaseous- and solid micro embolus formation during transcatheter procedures (CATH) and surgery in children with congenital heart disease (CHD). Silent strokes during surgery or CATH may contribute to neurological impairment. NeoDoppler is a non-invasive ultrasound system based on plane wave transmissions to continuously monitor cerebral blood flow in infants with an open fontanelle. Gaseous- and solid micro embolus passing through the ultrasound beam create High Intensity Transient Signals (HITS) in the Doppler signal. Purpose: We aimed to study the amount of HITS during CATH and surgery in infants using NeoDoppler. Methods: The NeoDoppler probe operates at a frequency of 7.8 MHz. The frame rate is 300 fps and the beam covers a wide cylindrical area (10/35mm width/depth). The system displays a color M-mode Doppler and a spectrogram. The broad ultrasound beam permits prolonged scanning time of each event as the HITS move through the ultrasound beam. The high framerate and color M-mode allows for tracking of embolies in depth. In this study the NeoDoppler probe was attached to the anterior fontanelle of infants with CHD during CATH (n=15) and cardiac surgery (n=13). HITS were defined as high intensity signal creating skewed lines in the color M-mode Doppler moving away or towards the probe (blue/red) with a corresponding high intensity signal in the spectrogram. HITS were grouped into single HITS and HITS with curtain effect. Single HITS were defined as single skewed lines in the color M-mode Doppler and spectrogram. HITS with curtain effect were defined as skewed broad lines or multiple intensity increase lines in the color M-mode Doppler with corresponding intensity increase that filled the entire doppler curve. HITS with curtain effect are believed to represent numerous HITS that could not be separated from each other in the spectrogram. HITS were manually detected in an in-house MatLab application. Results: The study group consisted of 28 infants (17 males) with different CHD who underwent CATH or surgery. The median age and weight was 96 days (range 3-240 days) and 5650 g (range 2400-8085 g). HITS were detected in 13/15 patients during CATH with a total of 392 HITS (Median 12, Range 0-149) and in all patients during surgery with a total of 772 HITS (Median 45, Range 11-150). The picture shows examples of single HITS (panel A) and HITS with curtain effect (panel B). One can appreciate the embolic trajectory pattern in depth over time in the color M-mode Display. Conclusion: In this study we found that NeoDoppler enables detection of frequent HITS in patients with CHD undergoing surgery or CATH. NeoDoppler could become a useful tool to guide modifications of procedures, with aim to reduce the risk of silent stroke. However, further studies are needed to validate the technique.