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Eur J Cardiothorac Surg 2000;17:272-278
© 2000 Elsevier Science NL

Increased aortic compliance maintains left ventricular performance at lower energetic cost

Haemodynamic Research Center, University of Liège, Liège, Belgium

Corresponding author. Cardiothoracic Surgery Department, University Hospital of Liège, B35 CHU Sart Tilman, 4000 Liège, Belgium. Tel.: +32-4-366-7163; fax: +32-4-366-7164
e-mail: philippe.kolh{at}chu.ulg.ac.be

Objective: The aim of this study was to investigate left ventricular contractility and energetic cost of cardiac ejection under conditions of acute increase in aortic compliance. Methods: In six anaesthetized pigs, ascending aortic compliance was increased by adding a volume chamber in parallel to the ascending aorta. Systemic vascular parameters, including characteristic impedance, peripheral resistance, total vascular compliance, and inertance, were estimated with a four-element windkessel model. Arterial elastance was derived from these parameters. Left ventricular systolic function was assessed by end-systolic pressure–volume relationship (end-systolic elastance), and stroke work. Pressure–volume area was used as a measure of myocardial oxygen consumption. Heart rate remained constant during the experimentation. Results: Adding the aortic volume chamber significantly increased vascular compliance from 0.95±0.08 to 1.17±0.06 ml/mmHg (P<0.01), while inductance, characteristic impedance, peripheral resistance, and arterial elastance remained statistically at basal values, respectively 0.0020±0.0003 mmHg.s²/ml, 0.105±0.009 mmHg.s/ml, 1.27±0.12 mmHg.s/ml, and 2.43±0.21 mmHg/ml. During the same interval, stroke work and pressure–volume area decreased respectively from 2700±242 to 2256±75 mmHg.ml (P<0.01), and from 3806±427 to 3179±167 mmHg.ml (P<0.01). Stroke work and pressure–volume area decreased at matched end-diastolic volumes. In contrast, end-systolic elastance, ejection fraction, and stroke volume remained statistically unchanged, respectively at 2.29±0.14 mmHg/ml, 48.1±2.1 %, and 32.4±1.7 ml. Conclusions: These data suggest that, when facing an increased aortic compliance, the left ventricle displays unchanged contractility, but the energetic cost of cardiac ejection is significantly decreased. These data may be of clinical importance when choosing an artificial prosthesis for ascending aortic replacement.

Key Words: Aortic compliance • Contractile function • Hemodynamics • End-systolic elastance • Pressure–volume area • Pigs

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