Aortic cross-clamping during vascular surgery analyzed by the diastolic time-constant of arterial pressure waves

JEANNE VENTRE; MARIA TERESA POLITI; JUAN MANUEL FERNÁNDEZ; ARTHUR GHIGO; SANDRA WRAY; JULIEN GAUDRIC; ISMAÏL KHELIFA; RICARDO ARMENTANO; PIERRE-YVES LAGRÉE; CLAUDIA CAPURRO; JOSÉ MARÍA FULLANA

Dublín

Congreso; 8th World Congress of Biomechanics; 2018

World Council of Biomechanics

Background: Aortic cross-clamping is a common strategy during vascular surgery. However, immediate changes in hemodynamic parameters during this intervention remain widely unknown. Using a numerical model of the vascular network with a Windkessel approach, important vascular features –such as compliance and resistance– can be estimated from the time-constant of the diastolic portion of the arterial pressure waves. We designed a cross-sectional study to evaluate changes in the morphology and the time-constant of arterial pressure waves before and after aortic cross-clamping during vascular surgeries in adult patients. Methods: Experimental data were registered from continuous invasive arterial pressure measurements with a fluid-filled catheter from the radial artery of patients undergoing vascular surgery. A stable set of beats were chosen manually through a 30 to 60-second interval immediately before and after each aortic clamp event. By using a custom software developed in Matlab, we calculated from experimental data the time-constant of the diastolic portion of the pressure wave for each beat. We also obtained a mean beat for each condition as to compare with numerical simulations of arterial pressure from a finite volume code for 1D fluid structure interaction in a 10 to 55 artery network. Results: 5 patients undergoing vascular surgery were enrolled. Patients were mostly elder (75 ± 16.3 years-old) males (75%) with hypertension (100%) and a smoking history (75%). In all patients, there was a significant 9% median reduction in the time-constant of the diastolic portion of the radial arterial pressure wave during aortic clamping, as compared to before aortic clamping. Overall median time-constant before clamping was 2.08 s (IQR 1.83-2.22) while overall median time-constant after clamping was 1.79 s (IQR 1.75-1.88); this difference was statistically significant (p= 0.0431). Conclusions and perspectives: In adult patients undergoing vascular surgery, aortic clamping systematically reduces the time-constant of the diastolic portion of radial arterial pressure waves. This result warrants further research on the underlying mechanisms of aortic clamping using a numerical model of the vascular network. By fitting simulated to experimental data, the time-constant of arterial pressure waves may shed some light on changes in compliance and resistance during this intervention.