Low Mean Perfusion Pressure Indexed to Body Surface Area is a Powerful Predictor of Poor Outcomes After Heart Transplantation in Patients With High Pre-Transplant Venous Pressure: A Clinical Study With Physiological Insights From Mathematical Modelling of Biventricular Heart Failure.

BACKGROUND & AIM: The deleterious consequences of chronically elevated venous pressure in patients with profound right ventricular or biventricular dysfunction are well known, including renal and hepatic dysfunction, and volume overload. The only option for these patients, if they fail optimal medical treatment, is a heart transplant, as they are not candidates for left ventricular assist device therapy. Mean perfusion pressure (MPP) is important in the outcomes of critically ill patients with high venous pressure. The question arises whether MPP is important for the outcomes of heart transplants in patients with elevated pre-transplant venous pressure. Medical management of heart failure patients with reduced ejection fraction involves lowering the systemic afterload with vasodilators while awaiting a transplant. We hypothesised that when venous pressure is elevated prior to transplant, a substantial reduction in systemic arterial elastance (Ea) through vasodilation may significantly decrease MPP, resulting in compromised end-organ function and consequent unfavourable outcomes after heart transplantation. This study aims to investigate whether a low MPP serves as a risk factor for adverse outcomes in heart transplant recipients with high venous pressure. METHOD: A retrospective analysis was conducted on 250 heart transplant recipients undergoing isolated heart transplantation at a single institution from October 2012 to March 2020. Right atrial pressure (RAP) of more than 15 mmHg was considered high. Additionally, Ea calculated as the ratio of end-systolic pressure to stroke volume, and MPP calculated as the difference between mean arterial pressure and RAP were considered in our analysis. The outcomes of transplantation were measured in terms of 90-day mortality and survival up to 7 years. RESULTS: High RAP was a significant risk factor for short-term and medium-term survival if Ea was low (<2.7 mmHg/mL, the median value). This group had 39.39% in-hospital mortality compared to 14.49% for RAP<15 mmHg (p∼0.005). When Ea was high, this difference in survival was not evident: 8% for RAP<15 mmHg vs 4.8% for RAP>15 mmHg (p∼0.550). This effect was mediated through a lower MPP, and the mortality due to lower MPP increased strikingly with higher body surface area (BSA). A negative correlation was observed between MPP indexed to BSA (MPPI) and the Model for End-Stage Liver Disease score (r∼-0.3580, p<0.0001) as well as creatinine (r∼-0.3551, p<0.0001). MPPI less than 40 mmHg/m2 was associated with poorer short-term (23.2% for MPPI<40 mmHg/m2 vs 7.1% for MPPI>40 mmHg/m2, p∼0.001) and medium-term survival. The impact of high RAP and low Ea on survival was evident even on medium-term follow-up; only 30% survival at 7 years follow-up for high RAP and low Ea vs 75% for RAP<15 mmHg (p∼0.0033). CONCLUSION: The acceptable blood pressure during vasodilator therapy in patients with high RAP needs to be higher, especially in those with higher BSA. MPPI less than 40 mmHg/m2 is a risk factor for survival, in the short and medium-term, after heart transplantation.

Virtual reality-guided left ventricular assist device implantation in pediatric patient: Valuable presurgical tool.

Virtual reality (VR) is increasingly used for presurgical planning and teaching during surgery. However, VR aided presurgical planning toolbox for left ventricular assist device (LVAD) implantation is not widely available. We investigated the use of a VR environment with wearable headsets and touch controllers in simulating an implant in an 11-year-old boy. The technology played a significant role in the optimal positioning of the LVAD.

Clinical profiles and risk factors for early and medium-term mortality following heart transplantation in a pediatric population: A single-center experience.

AIMS AND OBJECTIVES: There is a paucity of data regarding the outcomes of Heart transplantation in children from the Indian subcontinent. The data of patients under the age of 18 undergoing an isolated heart transplantation was analyzed for patient clinical profiles and risk factors for early and medium-term mortality. Hospital mortality was defined as death within 90 days of transplantation and medium-term survival as follow up of up to 6 years. MATERIALS AND METHODS: A total of 97 patients operated between March 2014 and October 2019 were included in this study. Data was collected about their INTERMACS status, pulmonary vascular resistance, donor heart ischemic times, donor age, donor to recipient weight ratio and creatinine levels. RESULTS: The age range was from 1 to 18 with a mean of 10.6 ± 4.6 years. 67 % patients were in INTERMACS category 3 or less.12 children were on mechanical circulatory support at the time of transplant. The 90 day survival was 89 %. The risk factors for hospital mortality was lower INTERMACS category (odd's ratio 0.2143, P = 0.026), elevated creatinine (odd's ratio 5.42, P = 0.076) and elevated right atrial pressure (odd's ratio 1.19, P = 0.015). Ischemic time, pulmonary vascular resistance (PVR) and PVR index (PVRI) had no effect on 90 day survival. Kaplan Meier estimates for 5 year survival was 73 %. The medium term survival was affected by INTERMACS category (Hazard ratio 0.7, P = .078), donor age > 25 (Hazard ratio 1.6, P = 0.26) and raised serum creatinine values.(Hazard ratio 2.7, P = 0.012). All the survivors are in good functional class. CONCLUSIONS: Excellent outcomes are possible after heart transplantation in a pediatric population even in a resource constrained environment of a developing economy. More efforts are needed to promote pediatric organ donation and patients need to be referred in better INTERMACS category for optimal outcomes.

Aortic valve dynamics using a fluid structure interaction model--The physiology of opening and closing.

Comparative study among aortic valves requires the use of an unbiased and relevant boundary condition. Pressure and flow boundary conditions used in literature are not sufficient for an unbiased analysis. We need a different boundary condition to analyze the valves in an unbiased, relevant environment. The proposed boundary condition is a combination of the pressure and flow boundary condition methods, which is chosen considering the demerits of the pressure and flow boundary conditions. In order to study the valve in its natural environment and to give a comparative analysis between different boundary conditions, a fluid-structure interaction analysis is made using the pressure and the proposed boundary conditions for a normal aortic valve. Commercial software LS-DYNA is used in all our analysis. The proposed boundary condition ensures a full opening of the valve with reduced valve regurgitation. It is found that for a very marginal raise in the ventricular pressure caused by pumping a fixed stroke volume, the cardiac output is considerably raised. The mechanics of the valve is similar between these two boundary conditions, however we observe that the importance of the root to raise the cardiac output may be overstated, considering the importance of the fully open nodule of arantius. Our proposed boundary condition delivers all the insights offered by the pressure and flow boundary conditions, along with providing an unbiased framework for the analysis of different valves and hence, more suitable for comparative analysis.

Normal aortic valves stay open much longer in systole than porcine substitutes.

OBJECTIVE: To compare the opening mechanics of porcine valve substitutes with those of a normal human aortic valve. BACKGROUND: All commercially available porcine valves are pretreated with glutaraldehyde. This study was undertaken to evaluate the consequences of such treatment on valve mechanics. METHODS: The opening mechanics of the aortic valve, especially the time taken to open fully from a closed position, and the duration for which the valve is maximally open, were compared in a normal aortic valve, a stent-mounted porcine valve, and a stentless porcine valve, using a finite element model. RESULTS: Despite a 4-fold higher gradient, stent-mounted porcine valves were slower in attaining the fully open position, and the time for which the valve was fully open was almost 25% less than a normal valve. In stentless valves, the compliant root made the initial opening mechanics similar to those of a normal valve. Once this effect was over, the effect of porcine leaflet properties took over, and there was a corresponding delay in the valve opening. CONCLUSIONS: Fixing the root with a stent and stiffening the leaflets with glutaraldehyde result in delayed valve opening and decrease the duration for which the valve is fully open, thus contributing to inferior hemodynamics.

Tetralogy of Fallot with pheochromocytoma: an unusual therapeutic challenge.

An adult with unoperated tetralogy of Fallot diagnosed simultaneously with pheochromocytoma is extremely rare. This poses obvious diagnostic and therapeutic challenges. A 29-year-old woman with these conditions was successfully operated on for both diseases in the same hospitalization. There is some interesting speculation regarding the association of pheochromocytoma with uncorrected cyanotic congenital heart disease.

Modified septosuperior approach for the repair of supracardiac total anomalous pulmonary venous return in infants.

An alternative technique for the repair of supracardiac total anomalous pulmonary venous return (TAPVR) is described. The pulmonary venous confluence (CPV) is identified below the right pulmonary artery between the aorta and superior vena cava. The atrial incisions are similar to a septosuperior approach of the mitral valve, modifying the incision on the roof of the left atrium to be parallel to the incision in the CPV. The common pulmonary vein is anastomosed to the roof of the left atrium. This approach offers optimal exposure for the repair without distorting the cardiac structures.

Severe coronary artery disease with coarctation of the aorta: role of off-pump coronary artery bypass grafting.

Severe coronary artery disease with coarctation of the aorta is an unusual and challenging clinical problem. We encountered three adults with severe coronary artery disease and tight coarctation of the aorta. Since angina was the dominant symptom in all, off-pump coronary artery bypass grafting (OPCABG) was done as a first stage. All survived the operation. After a gap of 3 weeks, coarctation repair has been done in 1 patient. We believe that OPCABG offers some unique advantages in this difficult situation.

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.

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.

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.