Dynamic deformation characteristics of porcine aortic valve leaflet under normal and hypertensive conditions

• Published in: American journal of physiology. Heart and circulatory physiology 2010-02, Vol.298 (2), p.H395-H405
• Main Authors: Yap, Choon Hwai, Kim, Hee-Sun, Balachandran, Kartik, Weiler, Michael, Haj-Ali, Rami, Yoganathan, Ajit P
• Format: Article
• Language: English
• Subjects: Animals; Aorta - pathology; Aorta - physiopathology; Aortic Valve - pathology; Aortic Valve - physiopathology; Biomechanical Phenomena; Blood Pressure - physiology; Cardiology; Cardiovascular disease; Coronary vessels; Disease Models, Animal; Female; Heart rate; Heart Ventricles - pathology; Heart Ventricles - physiopathology; Hypertension; Hypertension - pathology; Hypertension - physiopathology; Models, Biological; Regional Blood Flow - physiology; Swine
• ISSN: 0363-6135; 1522-1539
• DOI: 10.1152/ajpheart.00040.2009

1 School of Biomedical Engineering, Georgia Institute of Technology and Emory University, and 2 School of Civil and Environmental Engineering, Georgia Institute of Technology, Atlanta, Georgia; and 3 School of Mechanical Engineering, Tel-Aviv University, Ramat Aviv, Israel Submitted January 13, 2009 ; accepted in final form November 6, 2009 Calcific aortic valve (AV) disease has a high prevalence in the United States, and hypertension is correlated to early onset of the disease. The cause of the disease is poorly understood, although biological and remodeling responses to mechanical forces, such as membrane tension, have been hypothesized to play a role. The mechanical behavior of the native AV has, therefore, been the focus of many recent studies. In the present study, the dynamic deformation characteristics of the AV leaflet and the effects of hypertension on leaflet deformation are quantified. Whole porcine aortic roots were trimmed and mounted in an in vitro pulsatile flow loop and subjected to normal (80/120 mmHg), hypertensive (120/160 mmHg), or severe hypertensive (150/190 mmHg) conditions. Local valve leaflet deformations were calculated with dual-camera photogrammetry method: by tracking the motion of markers placed on the AV leaflets in three dimensions and calculating their spatial deformations. The results demonstrate that, first, during diastole, high transvalvular pressure induces a stretch waveform which plateaus over the diastolic duration in both circumferential and radial directions. During systole, the leaflet stretches in the radial direction due to forward flow drag forces but compresses in the circumferential direction in a manner in agreement with Poisson's effect. Second, average diastolic and systolic stretch ratios were quantified in the radial and circumferential directions in the base and belly region of the leaflet, and diastolic stretch was found to increase with increasing pressure conditions. dynamic stretch; dynamic strain; hypertension; dual-camera photogrammetry Address for reprint requests and other correspondence: A. P. Yoganathan, Georgia Institute of Technology, Biomedical Engineering, 313 Ferst Dr., Atlanta, GA 30332 (e-mail: ajit.yoganathan{at}bme.gatech.edu ).