Assessment of hemodynamic conditions in the aorta following root replacement with composite valve-conduit graft

This paper presents the analysis of detailed hemodynamics in the aortas of four patients following replacement with a composite bio-prosthetic valve-conduit. Magnetic resonance image-based computational models were set up for each patient with boundary conditions comprising subject-specific three-dimensional inflow velocity profiles at the aortic root and central pressure waveform at the model outlet. Two normal subjects were also included for comparison. The purpose of the study was to investigate the effects of the valve-conduit on flow in the proximal and distal aorta. The results suggested that following the composite valve-conduit implantation, the vortical flow structure and hemodynamic parameters in the aorta were altered, with slightly reduced helical flow index, elevated wall shear stress and higher non-uniformity in wall shear compared to normal aortas. Inter-individual analysis revealed different hemodynamic conditions among the patients depending on the conduit configuration in the ascending aorta, which is a key factor in determining post-operative aortic flow. Introducing a natural curvature in the conduit to create a smooth transition between the conduit and native aorta may help prevent the occurrence of retrograde and recirculating flow in the aortic arch, which is particularly important when a large portion or the entire ascending aorta needs to be replaced

In-vivo assessment of the morphology and hemodynamic functions of the BioValsalva (TM) composite valve-conduit graft using cardiac magnetic resonance imaging and computational modelling technology

BACKGROUND: The evaluation of any new cardiac valvular prosthesis should go beyond the classical morbidity and mortality rates and involve hemodynamic assessment. As a proof of concept, the objective of this study was to characterise for the first time the hemodynamics and the blood flow profiles at the aortic root in patients implanted with BioValsalva™ composite valve-conduit using comprehensive MRI and computer technologies. METHODS: Four male patients implanted with BioValsalva™ and 2 age-matched normal controls (NC) underwent cardiac magnetic resonance imaging (MRI). Phase-contrast imaging with velocity-mapping in 3 orthogonal directions was performed at the level of the aortic root and descending thoracic aorta. Computational fluid dynamic (CFD) simulations were performed for all the subjects with patient-specific flow information derived from phase-contrast MR data. RESULTS: The maximum and mean flow rates throughout the cardiac cycle at the aortic root level were very comparable between NC and BioValsalva™ patients (541 ± 199 vs. 567 ± 75 ml/s) and (95 ± 46 vs. 96 ± 10 ml/s), respectively. The maximum velocity (cm/s) was higher in patients (314 ± 49 vs. 223 ± 20; P = 0.06) due to relatively smaller effective orifice area (EOA), 2.99 ± 0.47 vs. 4.40 ± 0.24 cm(2) (P = 0.06), however, the BioValsalva™ EOA was comparable to other reported prosthesis. The cross-sectional area and maximum diameter at the root were comparable between the two groups. BioValsalva™ conduit was stiffer than the native aortic wall, compliance (mm(2) • mmHg(−1) • 10(−3)) values were (12.6 ± 4.2 vs 25.3 ± 0.4.; P = 0.06). The maximum time-averaged wall shear stress (Pa), at the ascending aorta was equivalent between the two groups, 17.17 ± 2.7 (NC) vs. 17.33 ± 4.7 (BioValsalva™ ). Flow streamlines at the root and ascending aorta were also similar between the two groups apart from a degree of helical flow that occurs at the outer curvature at the angle developed near the suture line. CONCLUSIONS: BioValsalva™ composite valve-conduit prosthesis is potentially comparable to native aortic root in structural design and in many hemodynamic parameters, although it is stiffer. Surgeons should pay more attention to the surgical technique to maximise the reestablishment of normal smooth aortic curvature geometry to prevent unfavourable flow characteristics. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1186/s13019-014-0193-6) contains supplementary material, which is available to authorized users

Pulse wave velocity and neutrophil gelatinase-associated lipocalin as predictors of acute kidney injury following aortic valve replacement

Background Accurate prediction, early detection and treatment of acute kidney injury (AKI) are essential for improving post-operative outcomes. This study aimed to examine the role of aortic stiffness and neutrophil gelatinase-associated lipocalin (NGAL) as predictors of AKI or need for early medical renal intervention following aortic valve replacement (AVR). Methods Aortic pulse wave velocity and plasma NGAL were measured pre-operatively in recruited patients undergoing AVR for aortic stenosis (AS). Plasma NGAL was also measured at 3 and 18–24 hours after cardiopulmonary bypass (CPB). AKI was defined using RIFLE criteria. Early medical renal intervention included diuretics or dopamine infusion exclusively for renal causes. Results Fifty-three patients aged 71 ± 9 years were included. Sixteen (30%) developed AKI (AKI-Yes) and 24 patients (45%) received early medical intervention (Intervention-Yes). There was no significant difference in the demographic, clinical or operative characteristics between the two groups for either outcome. PWV did not significantly correlate with AKI (r = 0.12, P = 0.13) or early intervention (r = 0.18, P = 0.18). At 3 h post-CPB, plasma NGAL was a much stronger predictor of both AKI and the need for early medical intervention than conventional markers such as creatinine (AKI: AUC 83%, 95% CI 0.70–0.95 vs. AUC 65%, 95% CI 0.47- 0.82; Medical intervention: AUC 84%, 95% CI 0.72–0.96 vs. AUC 56%, 95% CI 0.38–0.73). Post-CPB (3 hr) plasma NGAL was also significantly associated with AKI (r = 0.68, P < 0.001) at levels above 150 ng/ml; and significantly associated with early intervention (r = 0.64, P < 0.001) above 136 ng/ml. Simple linear regression showed no relationship between PWV and NGAL levels. Conclusion Aortic PWV does not correlate significantly with post-operative AKI or plasma NGAL levels in surgical AS patients. Post-operative NGAL is however an early and powerful predictive biomarker of both post-operative AKI and the need for early medical renal intervention and should consequently be considered in prediction models for AKI after cardiac surgery

Arterial stiffness is a predictor for acute kidney injury following coronary artery bypass graft surgery

Cardiac surgery-associated acute kidney injury (CSA-AKI) is a serious postoperative complication of cardiac surgery, an episode of which impacts on patient morbidity and mortality. Pulse wave velocity (PWV; a non-invasive measurement tool to assess arterial stiffness) has been shown to predict kidney disease progression, and cardiovascular and all-cause mortality in patients with chronic kidney disease. We hypothesised that PWV would also predict acute kidney injury in subjects who have undergone non-valve repair elective coronary artery bypass graft (CABG) surgery

Aortic stiffness is related to the ischemic brain injury biomarker N-methyl-D-aspartate receptor antibody levels in aortic valve replacement

Background. Aortic stiffness changes the flow pattern of circulating blood causing microvascular damage to different end-organ tissues, such as brain cells. The relationship between aortic stiffness measured by pulse wave velocity (PWV) and serum ischemic brain injury biomarker N-methyl-D-aspartate receptor antibody (NR2Ab) levels in aortic valve replacement has not been assessed. Methods. Patients undergoing aortic valve replacement (AVR) for aortic stenosis (AS) had their PWV and NR2Ab serum levels measured preoperatively. We analyzed PWV and NR2Ab in two ways: (1) as continuous variables using the actual value and (2) as dichotomous variables (PWV-norm and PWV-high groups) and (NR2Ab-low and NR2Ab-high groups). Results. Fifty-six patients (71 ± 8.4 years) were included in this study. The NR2Ab level (ng/mL) was significantly higher in the PWV-high group (n = 21) than in PWV-norm group (n = 35; median 1.8 ± 1.2 versus 1.2 ± 0.7, resp., P = 0.003). NR2Ab level was positively associated with PWV and negatively associated with male gender. Multiple regression revealed PWV independently related to NR2Ab level, and PWV cut-off was associated with a 7.23 times increase in the likelihood of having high NR2Ab (>1.8 ng/mL). Conclusion. Higher PWV in patients with surgical aortic stenosis is associated with higher levels of the ischemic brain biomarker NR2Ab

A systematic review of left ventricular cardio-endoscopic surgery

Better visualisation, accurate resection and avoidance of ventriculotomy associated with use of endoscopic devices during intracardiac surgery has led to increasing interest in their use. The possibility of combining a cardio-endoscopic technique with either minimally invasive or totally endoscopic cardiac surgery provides an incentive for its further development. Several devices have been used, however their uptake has been limited due to uncertainty around their impact on patient outcomes. A systematic review of the literature identified 34 studies, incorporating 54 subjects undergoing treatment of left ventricular tumours, thrombus or hypertrophic myocardium using a cardio-endoscopic technique. There were no mortalities (0%; 0/47). In 12 studies, the follow-up period was longer than 30 days. There were no post-operative complications apart from one case of atrial fibrillation (2.2%; 1/46). Complete resection of left ventricular lesion was achieved in all cases (100%; 50/50). These successful results demonstrate that the cardio-endoscopic technique is a useful adjunct in resection of left ventricular tumours, thrombus and hypertrophic myocardium. This approach facilitates accurate resection of pathological tissue from left ventricle whilst avoiding exposure related valvular damage and adverse effects associated with ventriculotomy. Future research should focus on designing adequately powered comparative randomised trials focusing on major cardiac and cerebrovascular morbidity outcomes in both the short and long-term. In this way, we may have a more comprehensive picture of both the safety and efficacy of this technique and determine whether such devices could be safely adopted for routine use in minimal access or robotic intra-cardiac surgery

The effect of off-pump coronary artery bypass on mortality after acute coronary syndrome: A meta-analysis

Background Patients requiring surgical revascularisation for acute coronary syndrome (ACS) form a clinically heterogeneous group ranging from haemodynamic stability to cardiogenic shock. Whilst 'off-pump' revascularisation (OPCAB) is often considered, patient selection and operative timing remain controversial. This study aims to identify whether OPCAB may confer a mortality benefit over ONCAB in revascularisation for ACS. Secondly, we review the impact of OPCAB on completeness of revascularisation (CR) and long-term re-intervention. Methods A systematic literature review identified 9 studies (1 randomised controlled trial) of which 8 fulfilled criteria for meta-analysis. Outcomes for a total of 3001 patients (n = 817 OPCAB, 2184 'on-pump' (ONCAB)) were meta-analysed using random effects modelling. Heterogeneity, subgroup analysis and quality scoring were assessed. Primary endpoints were 30-day and mid-term mortality. Secondary endpoints were CR, revascularisation index and re-intervention. Results OPCAB conferred comparable mortality to ONCAB at both 30-days and mid-term follow up (p = 0.08 and p = 0.46 respectively). OPCAB was also associated with less CR (WMD - 0.60, 95% CI [- 0.82, - 0.38], p < 0.00001) and a lower revascularisation index (WMD - 0.25, 95% CI [- 0.30, - 0.19], p < 0.00001), although no difference was observed in re-intervention rate (OR 1.33; 95% CI [0.99, 2.07], p = 0.99). Conclusions We conclude that OPCAB may be a safe and comparable alternative to ONCAB in clinically stable ACS patients requiring urgent/emergent revascularisation. However, in order to finally determine whether OPCAB may provide any more than just comparability to ONCAB in the setting of ACS, further research must clearly define selection criteria, better characterize this heterogeneous patient group and assess the effects of incomplete revascularisation on long-term outcomes. © 2013 Elsevier Ireland Ltd

Quality of life after mitral valve intervention

Advancements in surgical technique and understanding of the pathophysiology of mitral valve (MV) dysfunction have led to improved outcomes. Seen as a development beyond measures of morbidity and mortality, health-related quality-of-life (HRQOL) outcome measures are becoming increasingly popular. These measures are important because complications following routine (i.e. low-risk) operations on the MV are uncommon and further markers of outcome are needed. Surgeons are increasingly operating earlier on asymptomatic patients and will need to prove that HRQOL is not impacted. Novel minimally invasive and transcatheter technologies will also need to demonstrate satisfactory HRQOL outcomes prior to widespread use. This systematic review provides an overview of all available literature detailing HRQOL in patients receiving MV interventions. In the 43 studies included, 6865 patients underwent procedures ranging from open replacement to percutaneous repair using devices such as the Mitraclip Clip Delivery System (MitraClip) (Abbott Vascular, Santa Clara, CA, USA). Most studies performed baseline HRQOL assessment, allowing postinterventional comparison. While the underlying literature had deficiencies, most studies report acceptable postintervention HRQOL that was comparable to that of matched general populations. Patient-specific (e.g. female gender, renal dysfunction) and surgical-specific factors (e.g. replacement instead of repair, elevated transmitral gradient) were identified that predispose patients to poorer long-term HRQOL outcomes. These factors are important for clinicians developing strategies to maximize their HRQOL outcomes. Future randomized studies would benefit from HRQOL measurements at specific time points to allow large-scale comparisons. Establishing a common HRQOL instrument for use in MV intervention studies may support detailed comparisons between specific techniques. Physical activity monitors, physiological biomarkers and radiological markers could also be used as innovative indicators of functional outcome