Mechanical properties of the aorta determined by the pressure-diameter relation

Abstract

Elastic properties of the aorta represent an important determinant of left ventricular function and coronary blood flow. Aortic pressure-diameter relation provides insights into the mechanism, involved in the alterations of the elastic properties of the aorta. Recently, we described a new method to obtain aortic pressure-diameter relation in conscious humans. Aortic strain, distensibility, pressure-diameter relation, stiffness constant, augmentation index and aortic energy loss are indexes of aortic elastic properties derived by this method. Coronary artery disease is a potent independent factor associated with aortic elastic performance. Smoking produced an acute decrease of the elastic properties of the aorta in habitual smokers. Passive smoking has a similar unfavourable effect on aortic elastic properties. Elastic properties of the aorta are deteriorated in hypertensive patients compared to normotensive subjects and energy loss due to aortic wall viscosity is increased in the first group. Tachycardia induced by ventricular pacing produces an acute increase of the aortic distensibility in humans. Intravenous 17 beta-estradiol produces an improvement of the elastic properties of the aorta in menopausal women both with and without coronary artery disease. A decrease of aortic stiffness is demonstrated during intraaortic balloon pumping, associated with significant increase of the cardiac index and significant reduction of myocardial oxygen consumption. Thus, therapeutic interventions alter the elastic properties of the aorta and improvement of the elastic properties of the aorta may be beneficial in altering the natural history of diseases.