Detection of coronary microembolisation by Doppler ultrasound during percutaneous coronary interventions

Abstract

Objective: To validate an intracoronary Doppler ultrasound device for high intensity transient signals (HITS) detection and to assess the incidence of HITS during percutaneous coronary intervention (PCI).

Methods and results: In an in vitro model, particle count and number of HITS detected by an intracoronary 0.014 inch Doppler wire were closely correlated (r = 0.97, p < 0.001). In the clinical study, 32 patients (mean (SD) age 61 (11) years; 23 men, nine women) with coronary artery disease were treated with balloon dilatation and stent implantation for a single vessel stenosis. In these patients HITS were detected during PCI in 84% (27 of 32). Reproducibility (r = 0.99, p < 0.001) and interobserver agreement (r = 0.84, p < 0.001) of HITS counts were significant. The number of HITS after stent implantation was significantly higher than after balloon dilatation (11 (7) v 2 (4), p < 0.001). Postprocedural coronary flow velocity reserve (CFVR) was < 2.0 in 55% (16 of 29) of all patients after balloon dilatation and < 2.0 in 23% (six of 26) after stent implantation. The number of HITS after stent implantation did not differ significantly between patients with CFVR < 2.0 and patients with CFVR > or = 2.0 (12 (8) v 10 (7), not significant).

Conclusions: Embolic particles can be detected as HITS by an intracoronary Doppler ultrasound device. Coronary microembolism is often observed during PCI, especially after stent implantation. However, the incidence of HITS alone does not explain a reduced CFVR after PCI.

Figure 1

Doppler images during percutaneous coronary interventions in patients. (A) High intensity transient signals (HITS) (arrows) after balloon dilatation. (B) HITS (arrows) after stent implantation. (C, D) Artefact signals (arrows).

Figure 2

Open loop system used in the in vitro studies. D indicates the tip of the Doppler guidewire.

Figure 3

Doppler images in the experimental open loop system with (A) HITS (arrow) representing a sand particle, and (B) without HITS for simulation of excavations.

Figure 4

Plot of linear regression analysis showing the relation between the number of particles counted and HITS detected (29 experiments, correlation r  =  0.97, p < 0.001).

Figure 5

Plots of linear regression analysis and mean difference. (A, B) Relation between the first and second number of HITS counted on different days by the same observer (n  =  32, correlation r  =  0.99, p < 0.001). (C, D) Comparison of number of HITS counted by two observers for analysis of interobserver agreement (n  =  32, correlation r  =  0.84, p < 0.001).

Figure 6

Number of HITS against coronary flow velocity reserve (CFVR) for all patients after balloon dilatation (black dots, correlation r  =  0.09, not significant) and stent implantation (white dots, correlation r  =  0.03, not significant).