Bicuspid Aortic Valve-Associated Ascending Thoracic Aortic Aneurysm: Patient-Specific Finite Element Analysis.

BACKGROUND: Elective repair of bicuspid aortic valve (BAV)-associated ascending thoracic aortic aneurysm (aTAA) is recommended at lower size limits than tricuspid aortic valve (TAV)-associated aTAA. Rupture/dissection can occur when wall stress exceeds wall strength. Previously, a validated computational method was developed for determining aTAA wall stress, but to date this method has not applied to a patient-specific BAV aTAA. The study aim was to develop a patient-specific BAV aTAA computational model to determine regional wall stress, using the required zero-pressure geometry, wall thickness, material properties, and residual stress. METHODS: A BAV aTAA specimen was excised intact during elective repair, and zero-pressure geometry generated using micro-computed tomography. Residual stress was determined from the aTAA opening angle. aTAA material properties determined using biaxial stretch testing were incorporated into an Ogden hyperelastic model. Finite element analyses (FEAs) were performed in LS-DYNA to determine wall stress distribution and magnitudes at systemic pressure. RESULTS: The left aTAA region had the highest stiffness, followed by the right, and then anterior/posterior walls, suggesting regional variability in mechanical properties. During systole, the mean principal wall stresses were 108.8 kPa (circumferential) and 59.9 kPa (longitudinal), while peak wall stresses were 789.4 kPa (circumferential) and 618.8 kPa (longitudinal). Elevated wall stress pockets were seen in anatomic left aTAA regions. CONCLUSIONS: To the present authors' knowledge, this was the first patient-specific BAV aTAA model based on surgical specimens to be developed. Surgical specimens serve as the 'gold standard' for determining wall stress to validate models based on in-vivo imaging data alone. Regions of maximal wall stress may indicate sites most prone to rupture, and are crucial for evaluating rupture risk based on the wall stress/strength relationship.

Human pulmonary autograft wall stress at systemic pressures prior to remodeling after the Ross procedure.

BACKGROUND AND AIM OF THE STUDY: Remodeling of the pulmonary autograft upon exposure to systemic pressure can lead to progressive dilatation and aneurysmal pathology. Remodeling is driven by changes in autograft wall stress upon exposure to systemic pressure; however, the magnitude of these changes is unknown. Previously, a porcine autograft finite element model was developed to determine wall stress, but the porcine and human material properties differed significantly. Hence, the study aim was to understand human pulmonary autograft biomechanics that lead to remodeling by determining wall stress magnitudes immediately after the Ross procedure using finite element analysis (FEA). METHODS: Human pulmonary root was scanned by high-resolution microcomputed tomography to construct a realistic three-dimensional geometric mesh. Stress-strain data from biaxial stretch testing was incorporated into an Ogden hyperelastic model to describe autograft mechanical properties for an adult Ross patient. Autograft dilatation and wall stress distribution during pulmonic and systemic pressures prior to remodeling were determined using explicit FEA in LS-DYNA. RESULTS: Human pulmonary autograft demonstrated non-linear material properties, being highly compliant in the low-strain region, and stiffening at high strain. The majority of dilatation occurred with < 20 mmHg pressurization. From pulmonary to systemic pressures, the increases in autograft diameter were up to 17%. Likewise, the maximal wall stress increased approximately 14.6-fold compared to diastolic pressures (from 13.0 to 190.1kPa), and six-fold compared to systolic pressures (from 48.6 to 289.6kPa). CONCLUSION: The first finite element model of the human pulmonary autograft was developed and used to demonstrate how autograft material properties prevent significant dilatation upon initial exposure to systemic pressure. Mild dilatation was noted in the sinuses and sinotubular junction. Autograft wall stress was increased greatly when subjected to systemic pressures, and may trigger biomechanical remodeling of the autograft. Sustained exposure to higher wall stresses, coupled with inadequate remodeling, may lead to future autograft dilatation.

Patient-specific finite element analysis of ascending thoracic aortic aneurysm.

BACKGROUND AND AIM OF THE STUDY: Rupture/dissection of ascending thoracic aortic aneurysm (aTAA) is a cardiovascular emergency. Elective surgical repair is primarily based on maximum diameter, but complications have occurred under the size limits for surgical intervention. aTAA wall stress may be a better predictor of patient-specific rupture risk, but cannot be directly measured in vivo. The study aim was to develop an aTAA computational model associated with tricuspid aortic valve (TAV) to determine patient-specific wall stresses. METHODS: A TAV-associated aTAA was excised intact during surgery. Zero-pressure geometry was generated from microcomputed tomography, and an opening angle was used to calculate residual stress. Material properties determined from stress-strain data were incorporated into an Ogden hyperelastic model. Wall stress distribution and magnitudes at systemic pressure were determined using finite element analyses (FEA) in LS-DYNA. RESULTS: Regional material property differences were noted: the left aTAA region had a higher stiffness compared to the right, and anterior/posterior walls. During systole, the mean principal wall stresses were 172.0 kPa (circumferential) and 71.9 kPa (longitudinal), while peak wall stresses were 545.1 kPa (circumferential) and 430.1 kPa (longitudinal). Elevated wall stress pockets were seen in anatomic left and right aTAA regions. CONCLUSION: A validated computational approach was demonstrated to determine aTAA wall stresses in a patient-specific fashion, taking into account the required zero-stress geometry, wall thickness, material properties and residual stress. Regions of maximal wall stress may indicate the sites most prone to rupture. The creation of a patient-specific aTAA model based on a surgical specimen is necessary to serve as the 'gold standard' for comparing models based on in-vivo data alone. Validated data using the surgical specimen are essential for establishing wall stress and rupture-risk relationships.

Correlation of calcification on excised aortic valves by micro-computed tomography with severity of aortic stenosis.

BACKGROUND AND AIM OF THE STUDY: The quantification of incidentally found aortic valve calcification on computed tomography (CT) is not performed routinely, as data relating to the accuracy of aortic valve calcium for estimating the severity of aortic stenosis (AS) is neither consistent nor validated. As aortic valve calcium quantification by CT is confounded by wall and coronary ostial calcification, as well as motion artifact, the ex-vivo micro-computed tomography (micro-CT) of stenotic aortic valves allows a precise measurement of the amounts of calcium present. The study aim, using excised aortic valves from patients with confirmed AS, was to determine if the amount of calcium on micro-CT correlated with the severity of AS. METHODS: Each of 35 aortic valves that had been excised from patients during surgical valve replacement were examined using micro-CT imaging. The amount of calcium present was determined by absolute and proportional values of calcium volume in the specimen. Subsequently, the correlation between calcium volume and preoperative mean aortic valve gradient (MAVG), peak transaortic velocity (V(max)), and aortic valve area (AVA) on echocardiography, was evaluated. RESULTS: The mean calcium volume across all valves was 603.2 +/- 398.5 mm3, and the mean ratio of calcium volume to total valve volume was 0.36 +/- 0.16. The mean aortic valve gradient correlated positively with both calcium volume and ratio (r = 0.72, p < 0.001). V(max) also correlated positively with the calcium volume and ratio (r = 0.69 and 0.76 respectively; p < 0.001). A logarithmic curvilinear model proved to be the best fit to the correlation. A calcium volume of 480 mm3 showed sensitivity and specificity of 0.76 and 0.83, respectively, for a diagnosis of severe AS, while a calcium ratio of 0.37 yielded sensitivity and specificity of 0.82 and 0.94, respectively. CONCLUSION: A radiological estimation of calcium amount by volume, and its proportion to the total valve volume, were shown to serve as good predictive parameters for severe AS. An estimation of the calcium volume may serve as a complementary measure for determining the severity of AS when aortic valve calcification is identified on CT imaging.

Regional mechanical properties of human pulmonary root used for the Ross operation.

BACKGROUND AND AIM OF THE STUDY: Significant dilation of the pulmonary autograft after the Ross operation is problematic and requires reoperation. Autograft remodeling occurs in response to the immediate rise in pressure and consequent wall stress. The stress-strain response of the pulmonary root plays an important role in understanding the structural and functional changes of the autograft following the Ross procedure. At present, limited data are available on the mechanical properties of fresh human pulmonary roots; hence, the study aim was to determine the regional mechanical properties of human pulmonary roots. METHODS: Eighteen fresh healthy specimens of human pulmonary root were obtained from the California Transplant Donor Network (Oakland, CA, USA). Five regions of the pulmonary root--anterior and posterior pulmonary artery (PA), and each of the three sinuses--were subjected to displacement-controlled equibiaxial stretch testing within 24 h of cross-clamp time. Comparisons between the different regions of the pulmonary root were made based on tissue stiffness at physiologic stress. Histologic analyses were also performed of the fibrous structures of the PA and sinuses. RESULTS: Human PA and sinuses demonstrated a nonlinear response to loading, with no directional dependency to biaxial loading. The anterior PA was significantly more compliant than the posterior PA and the three sinuses in both circumferential and longitudinal directions (p < 0.04). However, there was no significant difference between the stiffness of the posterior PA and that of the three sinuses (p > 0.43), or among the three sinuses (p > 0.30) in the two directions. A tight, more dense weave of elastin was found in the anterior PA than in either the posterior PA or the sinuses. CONCLUSION: Significant inherent differences in compliance were demonstrated among different regions of the human pulmonary root. These regional differences may impact upon pulmonary autograft remodeling following the Ross operation, and also influence late autograft dilation.

Massive TAVR: Complex Transcatheter Aortic Valve Replacement in the Setting of an Enormous Adnexal Mass.

A 65-year-old woman with a large adnexal mass was found to have severe bicuspid aortic valve stenosis. Transcatheter aortic valve replacement was chosen rather than surgical aortic valve replacement because of concerns over risks. We demonstrate the value of pre-operative transcatheter aortic valve replacement before prompt noncardiac surgery. Furthermore, it illustrates some useful bailout techniques in this challenging scenario. (Level of Difficulty: Intermediate.).

The association between Chlamydia pneumoniae DNA in arherosclerotic plaque and major risk factors in patients undergoing coronary artery bypass grafting.

BACKGROUND AND AIM: This study was conducted to investigate the prevalence of Chlamydia pneumoniae pathogen inside the atherosclerotic plaque of patients undergoing CABG by using PCR assay and to determine whether there is any association between the presence of bacteria in atherosclerotic lesions and classical coronary risk factors. METHODS: In a cross-sectional study, 102 patients (20 to 79 years old; 73.5% male) undergoing CABG were evaluated in terms of major coronary risk factors and the presence of Chlamydia pneumoniae. RESULTS: Chlamydia pneumoniae was found in 23.4% of coronary plaque specimens. Of these, two patients had no risk factor and the rest of the patients had 1 to 3 risk factors. Patients with positive PCR were more likely to have hypercholesterolaemia (p = 0.009) and low HDL levels (p = 0.000) in comparison with the PCR-negative group. There were no statistical differences for other risk factors. CONCLUSION: Our results imply the synergic contribution of Chlamydia pneumoniae DNA and known dyslipidaemia to the development of atherosclerotic lesions in patients undergoing CABG.

Heart transplantation in iran; a comprehensive single-center review of 15-year performance.

BACKGROUND: Heart transplantation in Iran was first performed in July 1993. Since then, Shariati Hospital, affiliated to Tehran University of Medical Sciences, has been representing the most active center of cardiac transplantation in Iran and one of the major sites in the Middle East. This is a comprehensive review of our 15-year practice registry to make a scheme of our record and achievements. METHODS: Clinical data on all consecutive transplanted patients from the Department of Cardiac Surgery, Shariati Hospital, Tehran, Iran over the last 15 years were reviewed. Descriptive and analytical statistics were extracted in regard to recipients, donors, surgical characteristics, and current status of the patients on follow-up. RESULTS: Totally, 90 patients were transplanted since 1993; 11, 32, and 47 in three five-year periods, respectively. The mean age of the recipients was 29.30+/-13.17 years. Motor-vehicle accident was the main cause of brain death of donors (48.8%). The most common indication for surgery was idiopathic dilated cardiomyopathy (75.5%).The mean survival rate has been 6.66+/-0.87 years. One-year and five-year survivals had a rising trend through the five-year periods. Acute allograft rejection and infection were the two major events complicating our transplants. CONCLUSION: This study shows that despite a vast variety of obstacles, we have passed the primitive milestones. The number of transplants is increasing at a higher rate in recent years, and patients' survival rates and outcomes seem to be improving.

Transient bilateral cortical visual loss after coronary artery bypass grafting in a normotensive risk-free patient.

BACKGROUND: Postoperative blindness has been mentioned as a rare complication of heart surgery. The majority of reported cases are caused by retinal artery occlusion or ischemic optic neuropathy. We report a case of transient visual loss due to cortical ischemia after coronary artery bypass grafting (CABG). CASE REPORT: A 52-year-old nondiabetic man developed complete bilateral visual loss immediately after CABG. He had been normotensive throughout the operation. An ophthalmologic exam detected no causative ocular damage. The results of a Doppler study of the carotid, vertebral, and ophthalmic arteries were completely normal, and an echocardiography examination showed no left ventricular clot. Magnetic resonance imaging of the brain, however, showed several ischemic plaques in watershed areas and a small subacute infarct in the occipital lobe. Recovery began on postoperative day 4, and the patient's vision was restored in 6 months. CONCLUSION: Although most cases of visual loss after open heart surgery have been caused by injuries to the peripheral optic system, cortical blindness may occur following open heart surgery in the absence of any preexisting risk factor. Fortunately, the course of recovery is promising one, as it was for our patient.

Biomechanics of Failed Pulmonary Autografts Compared to Native Aortic Roots.

BACKGROUND: Progressive autograft dilatation after a Ross operation suggests that remodeling does not effectively reproduce native aortic root biomechanics. In the first of this two-part series, we compared mechanical properties of explanted autografts to pulmonary roots at pulmonary pressures. The goal of this study was to compare mechanical properties of explanted autografts to native aortic roots at systemic pressures. METHODS: Autograft specimens were obtained from patients undergoing reoperation after Ross operation. For comparison, native aortic roots were obtained from unused donor hearts. Biaxial stretch testing was performed to determine tissue mechanical properties. Tissue stiffness was determined at patient-specific physiologic stresses corresponding to systemic pressures (80 and 120 mm Hg) and hypertensive state (200 mm Hg). RESULTS: Nonlinear stress-strain curves were present for both failed autografts and native aortic roots. Explanted autografts were significantly more compliant than native aortic roots at 80 mm Hg (1.53 ± 0.68 versus 2.99 ± 1.34 MPa; p = 0.011), 120 mm Hg (2.54 ± 1.18 versus 4.93 ± 2.21 MPa; p = 0.013), and 200 mm Hg (4.79 ± 2.30 versus 9.21 ± 4.16 MPa; p = 0.015). Autograft tissue stiffness at 80, 120, and 200 mm Hg was not correlated with age at the time of Ross operation (p = 0.666, p = 0.639, and p = 0.616, respectively) or time in the systemic circulation (p = 0.635, p = 0.637, and p = 0.647, respectively). CONCLUSIONS: Failed pulmonary autografts retained a nonlinear response to mechanical loading typical of healthy arterial tissue. Despite similar wall thickness between autografts and aorta, autograft stiffness in this patient population was significantly reduced compared with native aortic roots. We demonstrated that biomechanical remodeling was inadequate in these specimens to achieve native aortic mechanical properties, which may have resulted in progressive autograft root dilatation.

Biomechanics of Failed Pulmonary Autografts Compared With Normal Pulmonary Roots.

BACKGROUND: Progressive dilatation of pulmonary autografts after the Ross operation may reflect inadequate remodeling of the native pulmonary root to adapt to systemic circulation. Understanding the biomechanics of autograft root dilatation may aid designing strategies to prevent dilatation. We have previously characterized normal human pulmonary root material properties; however, the mechanical properties of failed autografts are unknown. In this study, failed autograft roots explanted during reoperation were acquired, and their material properties were determined. METHODS: Failed pulmonary autograft specimens were obtained from patients undergoing reoperation after the Ross operation. Fresh human native pulmonary roots were obtained from the transplant donor network as controls. Biaxial stretch testing was performed to determine tissue mechanical properties. Tissue stiffness was determined at patient-specific physiologic stresses at pulmonary pressures. RESULTS: Nonlinear stress-strain response was present in both failed autografts and normal pulmonary roots. Explanted pulmonary autografts were less stiff than were their native pulmonary root counterparts at 8 mm Hg (134 ± 42 vs 175 ± 49 kPa, respectively) (p = 0.086) and 25 mm Hg (369 ± 105 vs 919 ± 353 kPa, respectively) (p = 0.006). Autograft wall stiffness at both 8 and 25 mm Hg was not correlated with age at the Ross procedure (p = 0.898 and p = 0.813, respectively) or with time in the systemic circulation (p = 0.609 and p = 0.702, respectively). CONCLUSIONS: Failed pulmonary autografts retained nonlinear response to mechanical loading typical of healthy human arterial tissue. Remodeling increased wall thickness but decreased wall stiffness in failed autografts. Increased compliance may explain progressive autograft root dilatation in autograft failures.

Material properties of CorCap passive cardiac support device.

BACKGROUND: Myocardial function deteriorates during ventricular remodeling in patients with congestive heart failure (HF). Ventricular restraint therapy using a cardiac support device (CSD) is designed to reduce the amount of stress inside the dilated ventricles, which in turn halts remodeling. However, as an open mesh surrounding the heart, it is unknown what the mechanical properties of the CSD are in different fiber orientations. METHODS: Composite specimens of CorCap (Acorn Cardiovascular, Inc, St. Paul, MN) CSD fabric and silicone were constructed in different fiber orientations and tested on a custom-built biaxial stretcher. Silicone controls were made and stretched to detect the parameters of the matrix. CSD coefficients were calculated using the composite and silicone matrix stress-strain data. Stiffness in different fiber orientations was determined. RESULTS: Silicone specimens exerted a linear behavior, with stiffness of 2.57 MPa. For the composites with 1 fiber set aligned with respect to the stretch axes, stiffness in the direction of the aligned fiber set was higher than that in the cross-fiber direction (14.39 MPa versus 5.66 MPa), indicating greater compliance in the cross-fiber direction. When the orientation of the fiber sets in the composite were matched to the expected clinical orientation of the implanted CorCap, the stiffness in the circumferential axis (with respect to the heart) was greater than in the longitudinal axis (10.55 MPa versus 9.70 MPa). CONCLUSIONS: The mechanical properties of the CorCap demonstrate directionality with greater stiffness circumferentially than longitudinally. Implantation of the CorCap clinically should take into account the directionality of the biomechanics to optimize ventricular restraint.

Biomechanical properties of human ascending thoracic aortic aneurysms.

BACKGROUND: Surgical management of ascending thoracic aortic aneurysms (aTAAs) relies on maximum diameter, growth rate, and presence of connective tissue disorders. However, dissection and rupture do occur in patients who do not meet criteria for surgical repair. This study investigated the mechanical properties of aTAAs compared with normal human ascending aortas for eventual development of biomechanical aTAA risk models. METHODS: aTAA specimens (n = 18) were obtained from patients undergoing surgical aneurysm repair, and fresh, healthy ascending aortas (n = 19) as controls were obtained from the transplant donor network. Biaxial stretch testing was performed to obtain tissue mechanical properties. Patient-specific aTAA physiologic stress was calculated based on preoperative computed tomography diameter. aTAA and ascending aorta tissue stiffness at respective physiologic stress were determined. RESULTS: Physiologic stress of aTAA was significantly greater (241.6 ± 59.4 kPa) than the 74 kPa for normal controls. Tissue stiffness of aTAAs was significantly greater than that of the ascending aortas at their respective physiologic stresses in the circumferential (3041.4 ± 1673.7 vs 905.1 ± 358.9 kPa, respectively; p < 0.001) and longitudinal (3498.2 ± 2456.8 vs 915.3 ± 368.9 kPa, respectively; p < 0.001) directions. Tissue stiffness of aTAAs positively correlated with aTAA diameter but did not correlate with patient age. No correlation was found between aTAA physiologic stress level and maximum aTAA diameter. CONCLUSIONS: aTAAs are much stiffer than normal ascending aortas at their respective physiologic stress, which was also significantly greater in ATAAs than ascending aortas. Patient-specific physiologic stress did not correlate with maximum aTAA diameter, and patient-specific aTAA wall stress may be a useful variable to predict adverse aTAA events.

Robotically controlled ablation for atrial fibrillation: the first real-world experience in Africa with the Hansen robotic system.

BACKGROUND: We report the first single-centre experience in Africa with the Sensei X robotic navigation system in an unselected subset of patients with atrial fibrillation (AF). METHODS: Data were recorded prospectively of all consecutive patients who underwent robotically assisted catheter ablation therapy using the Sensei X robotic navigation system at the Christiaan Barnard Memorial Hospital, Cape Town, South Africa, from July 2009 to July 2010. Outcomes were defined at one and nine months. RESULTS: A total of 95 patients were included: 63% had only AF and 37% had AF plus atrial flutter. AF was of the persistent type in 81% of patients. The mean procedure, fluoroscopy and ablation times were 220.6 ± 89.6 min, 31.0 ± 20.4 min, and 61.3 ± 28.1 min, respectively. Both fluoroscopy and procedure times were significantly longer for the first 19 patients compared with the remaining 76 patients (43.5 ± 22.7 vs 27.8 ± 18.5 min and 274.7 ± 90.2 vs 207.1 ± 84.7 min, respectively, p = 0.002). The procedural endpoint of the study was successfully achieved in all patients. After one attempt, 27% were discharged from hospital off anti-arrhythmic drugs (AADs). At a median of nine months' follow up, 74% were AF-free off AADs, and 11% were AF-free on AADs, yielding a total freedom from AF of 84% without any redo procedures. Freedom from relapse after 1.12 procedures was 88%. CONCLUSION: The Sensei X robotic navigation system offers a safe and effective approach for the treatment of AF. There was a learning curve with regard to fluoroscopy and procedure time, after which point reduction in radiation exposure and operator strain, as well as improvement in procedure throughputs were even more pronounced.

Incidental aortic valve calcification on CT scans: significance for bicuspid and tricuspid valve disease.

RATIONALE AND OBJECTIVES: The aim of this study was to evaluate the role of incidental aortic valve calcification on routine computed tomographic scans as a marker for stenosis, as assessed by echocardiography, in patients with bicuspid aortic valve (BAV) and tricuspid aortic valve. MATERIALS AND METHODS: Computed tomographic and echocardiographic studies were retrospectively reviewed for 182 consecutive, unselected patients and 426 patients identified by a record search for "aortic valve calcification." Location and severity of valve calcification were correlated with aortic valve morphology and stenosis. Differences between subgroups were assessed using χ(2) or Fisher's exact tests. RESULTS: In unselected patients, calcification was present in 25.8% with tricuspid aortic valves (46 of 178) and 75% (three of four) with BAV. In patients selected for valve calcification, the average age of those with tricuspid aortic valves (n = 395) was 14.3 years older than those with BAV (n = 31). Patients with BAV were more likely to have severe calcification (87% vs 50%, P < .001), and if severe calcification was present, it was more likely to involve only the valve leaflets (41% vs 9%, P < .001) and result in aortic stenosis (85% vs 58%, P = .006). Patients aged < 60 years with severe calcification were more likely to have BAV (56% vs 7%; odds ratio, 7.9; 95% confidence interval, 3.4-18.7). CONCLUSIONS: Aortic valve calcification was found 14 years earlier in patients with BAV and was more severe and strongly linked to aortic stenosis. Valve calcification on computed tomographic scans should be considered a marker for BAV if found before the seventh decade.

Comparison of mechanical properties of human ascending aorta and aortic sinuses.

BACKGROUND: Computational finite element models of the aortic root have previously used material properties of the ascending aorta to describe both aortic sinuses and ascending aorta. We have previously demonstrated significant material property differences between ascending aorta and sinuses in pigs. However, it is unknown whether these regional material property differences exist in humans. The main objective of this study was to investigate biomechanics of fresh human ascending aorta and aortic sinuses and compare nonlinear material properties of these regions. METHODS: Fresh human aortic root specimens obtained from the California Transplant Donor Network (Oakland, CA) were subjected to displacement-controlled equibiaxial stretch testing within 24 hours of harvest. Stress-strain data recorded were used to derive strain energy functions for each region. Tissue behavior was quantified by tissue stiffness and a direct comparison was made between different regions of aortic root at physiologic stress levels. RESULTS: All regions demonstrated a nonlinear response to strain during stretch testing in both circumferential and longitudinal directions. No significant difference in tissue stiffness was found between anterior and posterior regions of the ascending aorta or among the three sinuses in both directions. However, our results demonstrated that human ascending aorta is significantly more compliant than aortic sinuses in both circumferential and longitudinal directions within the physiologic stress range. CONCLUSIONS: Significant material and structural differences were observed between human ascending aorta and aortic sinuses. Regionally specific material properties should be employed in computational models used to assess treatments of structural aortic root disease.

Biomechanical comparison of human pulmonary and aortic roots.

OBJECTIVE: Significant dilation of the pulmonary autograft is problematic after the Ross operation and may require reoperation. Pulmonary autograft remodelling occurs in response to the immediate rise in pressure and consequently wall stress. Stress-strain response of the pulmonary root plays an important role in understanding autograft function and remodelling following the Ross procedure. However, limited data are available on mechanical properties of fresh human pulmonary roots. The aim of this study was to compare mechanical properties of fresh human pulmonary and aortic roots prior to the Ross operation. METHODS: Fresh healthy human hearts (n = 21) were obtained from California Transplant Donor Network (Oakland, CA, USA). Five regions of pulmonary and aortic roots, anterior and posterior artery and three sinuses, were subjected to displacement-controlled equibiaxial stretch testing within 24 h of cross-clamp time. Different regions of pulmonary and aortic roots were compared using a paired-comparison approach based on tissue stiffness at systemic pressure. Furthermore, histologic analysis was performed to compare the fibrous structure of pulmonary and aortic roots. RESULTS: Human pulmonary and aortic roots demonstrated nonlinear response to biaxial loading in both circumferential and longitudinal directions. Pulmonary artery was found to be significantly stiffer than ascending aorta at systemic pressure in the two principal directions (P < 0.001). Similarly, pulmonary sinuses were significantly stiffer than the aortic sinuses at systemic pressure in the two directions (P < 0.001). Histological analysis revealed that aortic roots had tight denser weave of elastin than pulmonary roots. CONCLUSIONS: Significant differences were found in the compliance and fibrous structure of human pulmonary and aortic roots. These regional differences may impact pulmonary autograft remodelling and influence late autograft dilation.

Operative risks and survival in veterans with severe aortic stenosis: surgery versus medical therapy.

BACKGROUND: Transcatheter aortic valves were developed as an alternative to surgery for the one third to two thirds of patients with severe aortic stenosis who do not undergo aortic valve replacement. In this study, we examined reasons for medical management of aortic stenosis in relation to operative risks and outcomes for veterans with and without valve replacement. METHODS: The echocardiography database was screened from 2000 to 2007 for severe aortic stenosis. The Society of Thoracic Surgeons risk scores and survival were determined for patients with and without aortic valve replacement. RESULTS: Of 132 severe aortic stenosis patients included, 42% were medically managed. Predicted operative mortality risk was lower for surgical patients than for medical patients (4.5%±4.2% versus 6.8%±5.1%, p=0.002). Overall, the most common reason for medical management of aortic stenosis was assumption that the patient was high risk for surgery (30.4%). The surgery group had significantly higher median survival (92.2 versus 32.4 months) and 5-year survival (71% versus 37%, p<0.001) than the medical group. Cardiac surgery was not consulted in 61% of medically managed patients, of whom only 18% had Society of Thoracic Surgeons risk score of 10 or greater. Aortic valve replacement was an independent predictor of lower mortality (hazard ratio 0.43, p=0.008). CONCLUSIONS: Although operative risk was higher among patients who did not undergo surgery, most were not the 10% or greater required for transcatheter valves. Given the significantly lower survival with medical therapy, aortic valve replacement should be carefully considered for most severe aortic stenosis patients whereas transcatheter aortic valves should be reserved for patients with high operative risks.

Valve-in-valve hemodynamics of 20-mm transcatheter aortic valves in small bioprostheses.

BACKGROUND: Transcatheter aortic valve (TAV) implantation is a treatment for selected patients with failing bioprostheses. We previously showed that currently available SAPIEN (Edwards Lifesciences, Irvine, CA) TAV sizes did not yield acceptable valve-in-valve (VIV) hemodynamics in small degenerated bioprostheses because optimal TAV function requires full stent expansion to its nominal size. The study objective was to determine (1) if 20-mm TAVs provide acceptable hemodynamics in small degenerated bioprostheses and (2) the effect of TAV spatial orientation on valvular hemodynamics and coronary flows. METHODS: Twelve 20-mm TAVs were created for implantation within 19-mm and 21-mm degenerated Carpentier-Edwards Perimount (Edwards Lifesciences) and porcine bioprostheses. Degenerated valves were sutured into human homograft roots and mounted in a pulse duplicator. TAVs were implanted within bioprostheses as VIV in standard orientation, in which TAV and bioprosthetic commissures were aligned, and later with 60-degree rotation. RESULTS: The 20-mm TAVs migrated retrograde into the left ventricle after VIV in the 21-mm Perimount bioprostheses. However, 20-mm TAVs in 19-mm Perimount (54.9±5.4 to 23.5±3.9 mm Hg, p=0.006) and 21-mm porcine bioprostheses (35.2±8.9 to 16.8±4.1 mm Hg, p=0.03) significantly reduced mean gradients. No significant reduction in pressure gradient occurred after VIV in 19-mm degenerated porcine bioprostheses. Mild regurgitation was observed after VIV. VIV with standard and 60-degree TAV orientation did not significantly alter hemodynamics or coronary flows. CONCLUSIONS: Valve-in-valve hemodynamics with 20-mm TAV improved for 19-mm Perimount and 21-mm porcine but not 19-mm porcine bioprostheses. No significant differences in hemodynamics were noted by orientation with TAV and bioprosthesis commissural alignment or 60-degree rotation.