Echocardiographic assessment of aortic elastic properties with automated border detection in an ICU: in vivo application of the arctangent Langewouters model

We studied whether combined pressure and transesophageal ultrasound monitoring is feasible in the intensive care unit ( ICU) setting for global cardiovascular hemodynamic monitoring [ systemic vascular resistance ( SVR) and total arterial compliance ( C-PPM)] and direct estimation of local ascending and descending aortic mechanical properties, i.e., distensibility and compliance coefficients ( DC and CC). Pressurearea data were fitted to the arctangent Langewouters model, with aortic cross- sectional area obtained via automated border detection. Data were measured in 19 subjects at baseline, during infusion of sodium nitroprusside ( SNP), and after washout. SNP infusion lowered SVR from 1.15 +/- 0.40 to 0.80 +/- 0.32 mmHg center dot ml(-1)center dot s ( P < 0.05), whereas CPPM increased from 0.87 +/- 0.46 to 1.02 +/- 0.42 ml/ mmHg ( P < 0.05). DC and CC increased from 0.0018 +/- 0.0007 to 0.0025 +/- 0.0009 1/ mmHg ( P < 0.05) and from 0.0066 +/- 0.0028 to 0.0083 +/- 0.0026 cm(2)/ mmHg ( P < 0.05), respectively, at the descending, but not ascending, aorta. The Langewouters model fitted the descending aorta data reasonably well. Assessment of local mechanical properties of the human ascending aorta in a clinical setting by automated border detection remains technically challenging.