Komarakshi R. Balakrishnan

Dynamic analysis of the aortic valve using a finite element model

BACKGROUND The major aim of this study was to examine the leaflet/aortic root interaction during the cardiac cycle, including the stresses developed during the interaction. METHODS Dynamic finite element analysis was used along with a geometrically accurate model of the aortic valve and the sinuses. Shell elements along with proper contact conditions were also used in the model. Pressure patterns during the cardiac cycle were given as an input, and a linear elastic model was assumed for the material. RESULTS We found that aortic root dilation starts before the opening of the leaflet and is substantial by the time leaflet opens. Dilation of the root alone helps in opening the leaflet to about 20%. The equivalent stress pattern shows an instantaneous increase in stress at the coaptation surface during closure. Stresses increase as the point of attachment is approached from the free surface. CONCLUSIONS The complex interplay of the geometry of the valve system can be effectively analyzed using a sophisticated dynamic finite element model. Results not previously brought out by the earlier static analysis shed new light on the root/valve interaction.

Further insights into normal aortic valve function: role of a compliant aortic root on leaflet opening and valve orifice area

BACKGROUND This study aims to find the fundamental differences in the mechanism of opening and closing of a normal aortic valve and a valve with a stiff root, using a dynamic finite element model. METHODS A dynamic, finite element model with time varying pressure was used in this study. Shell elements with linear elastic properties for the leaflet and root were used. Two different cases were analyzed: (1) normal leaflets inside a compliant root, and (2) normal leaflets inside a stiff root. RESULTS A compliant aortic root contributes substantially to the smooth and symmetrical leaflet opening with minimal gradients. In contrast, the leaflet opening inside a stiff root is delayed, asymmetric, and wrinkled. However, this wrinkling is not associated with increased leaflet stresses. In compliant roots, the effective valve orifice area can substantially increase because of increased root pressure and transvalvular gradients. In stiff roots this effect is strikingly absent. CONCLUSIONS A compliant aortic root contributes substantially to smooth and symmetrical leaflet opening with minimal gradients. The compliance also contributes much to the ability of the normal aortic valve to increase its effective valve orifice in response to physiologic demands of exercise. This effect is strikingly absent in stiff roots.

False Aneurysm Following Modified Blalock-Taussig Shunt

A 3 1/2-year-old female child presented with massive hemoptysis 5 months after a modified Blalock-Taussig (BT) shunt for double-outlet right ventricle with pulmonary stenosis. Computerized tomographic scan and angiography showed a false aneurysm of the subclavian artery at the insertion of the shunt. Successful surgical management is discussed.

Primary Intracardiac Yolk Sac Tumor

Abstract. A 2-year-old male child presented with fever, complete heart block, and congestive cardiac failure. Echocardiography showed a dumbbell-shaped mass in the right ventricle and right atrium. He was operated on with a provisional diagnosis of rhabdomyoma. Histopathology and immunohistochemistry of the resected tumor revealed a malignant germ cell tumor with predominant yolk sac differentiation.

Surgical Closure of Atrial Septal Defect in Children under Two Years of Age

Infants with atrial septal defects are seldom symptomatic and usually require elective surgery between 2 and 4 years of age. However a small minority is symptomatic and management at this age has been controversial. This study evaluated surgical closure of atrial septal defect below 2 years of age. Eighteen infants with a mean age of 13.4 ± 5.7 months were operated on for secundum atrial septal defect from 1994 to 2001. Fourteen patients were symptomatic with failure to thrive in 7 and recurrent respiratory infections in 7, one had increasing cardiomegaly, and 3 were operated on early for social reasons. The defect was isolated in 11 patients (61%) and the other 7 (39%) had minor associated lesions requiring additional procedures such as ductal ligation, direct closure of a tiny ventricular septal defect, and inspection of the mitral valve. There were no early or late deaths. The postoperative course was complicated by pulmonary problems in 4 cases. Of the 16 patients available for follow-up, 14 were asymptomatic and 2 were symptomatically improved. Most showed a dramatic improvement in growth and development. These gratifying results indicate that consideration should be given to early surgical closure of atrial septal defect in symptomatic infants.

Effect of Calcification on Plaque Stresses and Vulnerability: A Finite Element Study

The factors responsible for atherosclerotic plaque rupture, the initiating event in the majority of acute coronary syndromes, have received a lot of attention in recent times. However, the effect of calcification on plaque vulnerability is still a matter of considerable debate. In order to clarify the effect of calcification on plaque stresses and vulnerability, parametric “what if” studies were conducted on a histology specimen of a coronary endarterectomy plaque using finite element analysis and the biomechanical stresses calculated. It was found that the maximum principle stresses may decrease, increase, or remain unchanged depending on the location of calcification within a plaque and the lumen shape. The effect of calcification on plaque stresses in a lipid-rich plaque is a consequence of a complex interplay of a number of factors including vessel geometry, lipid distribution, and patterns and site of calcification.

Long-Term Fate of a 4-mm PTFE Tube Graft Used in Takeuchi Repair for Anomalous Origin of the Left Coronary Artery From the Pulmonary Artery

2008;86:665 Ann Thorac Surg Komarakshi Balakrishnan, Narasimha Reddy and Ranjit Sahadevan Anomalous Origin of the Left Coronary Artery From the Pulmonary Artery Long-Term Fate of a 4-mm PTFE Tube Graft Used in Takeuchi Repair for http://ats.ctsnetjournals.org/cgi/content/full/86/2/665 located on the World Wide Web at: The online version of this article, along with updated information and services, is