Regularization of a Mathematical Model of the Wheatley Heart Valve.

This note considers the mathematical model published in the Journal of Biomechanical Engineering by McKee et al. [McKee, S., Cuminato, J. A., Stewart, I. W., and Wheatley, D. J., 2021, "A Mathematical Representation of the Wheatley Heart Valve," ASME J. Biomech. Eng., 143(8), p. 081006]. The model presented there suffers from the fact that there is a line discontinuity in the first derivative producing what appears to be a kink in each of the leaflets. This note is concerned with regularizing the shape of the valve while holding to Wheatley's essential idea [Wheatley, D. J., 2016, "Heart Valve," U.S. Patent No. 9,259,313, UK Patent No. 2,982,340 (2017), European Patent No. 2,979,666 (2017)].

A Mathematical Representation of the Wheatley Heart Valve.

Starting from a hand-drawn contour plot, this note develops a set of intersecting and contiguous circles whose perimeter, upon extending appropriately to three dimensions, can be seen to be a natural mathematical representation of the Wheatley heart valve.

Percutaneous heart valves; past, present and future.

Percutaneous heart valves provide a promising future for patients refused surgery on the grounds of significant technical challenges or high risk for complications. Since the first human intervention more than 10 years ago, over 50 different types of valves have been developed. The CoreValve and Edwards SAPIEN valves have both experienced clinical trials and the latter has gained FDA approval for implantation in patients considered inoperable. Current complications, such as major vascular bleeding and stroke, prevent these valves from being commonly deployed in patients considered operable in conventional surgery. This review focuses on the past and present achievements of these valves and highlights the design considerations required to progress development further. It is envisaged that, with continued improvement in valve design and with increased clinical and engineering experience, percutaneous heart valve replacement may one day be a viable option for lower-risk operable patients.

Microvascular preconditioning is not detectable by corrosion casting in the isolated perfused rat heart after 30 minutes of ischaemia.

OBJECTIVE: Ischaemic preconditioning protects the myocardium from ischaemic injury and may also protect the vascular endothelium from the deleterious effects of ischaemia and reperfusion. We examined the possibility that ischaemic preconditioning might preserve the integrity of the coronary microcirculation following ischaemia and reperfusion. METHODS: Isolated rat hearts were perfused in Langendorff mode for 30 minutes and then subjected to 30 minutes of global ischaemia with or without ischaemic preconditioning (threexthree minute cycles). Some hearts underwent an additional 60 minutes of reperfusion. At the end of each protocol, microvascular corrosion casts were made by methylmethacrylate injection. RESULTS: Median left ventricular capillary density [interquartile range] after ischaemia was slightly but not significantly better with preconditioning at 6.8 [4.0-14.7]x10(-2) mm3.mg(-1) vs. 5.2 [2.6-7.1]x10(-2) mm3.mg(-1) (p=0.13). After 60 min of reperfusion, capillary density in preconditioned left ventricles was 20.7 [10.7-22.8]x10(-2) mm3.mg(-1) vs. 16.0 [10.2-23.0]x10(-2) mm3.mg(-1) for untreated ventricles (p=0.47). Coronary blood flow and heart rate were unchanged from before ischaemia. CONCLUSIONS: Ischaemia for 30 minutes induced global left ventricular capillary loss which was unmodified by preconditioning. We did not demonstrate vascular preconditioning using this model.

Dynamic modelling of prosthetic chorded mitral valves using the immersed boundary method.

Current artificial heart valves either have limited lifespan or require the recipient to be on permanent anticoagulation therapy. In this paper, effort is made to assess a newly developed bileaflet valve prosthesis made of synthetic flexible leaflet materials, whose geometry and material properties are based on those of the native mitral valve, with a view to providing superior options for mitral valve replacement. Computational analysis is employed to evaluate the geometric and material design of the valve, by investigation of its mechanical behaviour and unsteady flow characteristics. The immersed boundary (IB) method is used for the dynamic modelling of the large deformation of the valve leaflets and the fluid-structure interactions. The IB simulation is first validated for the aortic prosthesis subjected to a hydrostatic loading. The predicted displacement fields by IB are compared with those obtained using ANSYS, as well as with experimental measurements. Good quantitative agreement is obtained. Moreover, known failure regions of aortic prostheses are identified. The dynamic behaviour of the valve designs is then simulated under four physiological pulsatile flows. Experimental pressure gradients for opening and closure of the valves are in good agreement with IB predictions for all flow rates for both aortic and mitral designs. Importantly, the simulations predicted improved physiological haemodynamics for the novel mitral design. Limitation of the current IB model is also discussed. We conclude that the IB model can be developed to be an extremely effective dynamic simulation tool to aid prosthesis design.

Interventional versus conservative treatment in acute non-ST elevation coronary syndrome: time course of patient management and disease events over one year in the RITA 3 trial.

OBJECTIVE: To determine whether, in acute non-ST elevation coronary syndrome, the benefit from early invasive coronary intervention compared with a conservative strategy of later symptom-guided intervention varies over time. METHODS: In RITA 3 (Randomised Intervention Trial of unstable Angina 3) patients were randomly assigned to coronary angiography (median 2 days after randomisation) and appropriate intervention (n = 895) or to a symptom-guided conservative strategy (n = 915). RESULTS: In the first week patients in both groups were at highest risk of death, myocardial infarction (MI) or refractory angina (incidence rate 40 times higher than in months 5-12 of follow up). There were 22 MIs and 6 deaths in the intervention group (largely due to procedure-related events, 14 MIs and 3 deaths) versus 17 MIs and 3 deaths in the conservative group. In the rest of the year there were an additional 12 versus 27 MIs, respectively (treatment-time interaction p = 0.021). Over one year in the intervention group there was a 43% reduction in refractory angina; 22% of patients underwent coronary artery bypass surgery and 35% underwent percutaneous coronary intervention only, which reduced refractory angina but provoked some early MIs; and 43% were still treated medically, mostly because of a favourable initial angiogram. CONCLUSION: Any intervention policy needs to recognise the high risk of events in the first week and the substantial minority of patients not needing intervention. Intervention may be best targeted at higher risk patients, as the early hazards of the procedure are then offset by reduced subsequent events.

5-year outcome of an interventional strategy in non-ST-elevation acute coronary syndrome: the British Heart Foundation RITA 3 randomised trial.

BACKGROUND: The long-term outcome of an interventional strategy in patients with non-ST-elevation acute coronary syndrome is unknown. We tested whether an interventional strategy (routine angiography followed by revascularisation) was better than a conservative strategy (ischaemia-driven or symptom-driven angiography) over 5 years' follow-up. METHODS: In a multicentre randomised trial, 1810 patients (from 45 hospitals in England and Scotland, UK) with non-ST-elevation acute coronary syndrome were randomly assigned to receive an early intervention (n=895) or a conservative strategy (n=915) within 48 h of the index episode of cardiac pain. In each group, the aim was to provide the best medical treatment, and also to undertake coronary arteriography within 72 h in the interventional strategy with subsequent management guided by the angiographic findings. Analysis was by intention to treat and the primary outcome (composite of death or non-fatal myocardial infarction) had masked independent adjudication. RITA 3 has been assigned the International Standard Randomised Control Trial Number ISRCTN07752711. FINDINGS: At 1-year follow-up, rates of death or non-fatal myocardial infarction were similar. However, at a median of 5 years' follow-up (IQR 4.6-5.0), 142 (16.6%) patients with intervention treatment and 178 (20.0%) with conservative treatment died or had non-fatal myocardial infarction (odds ratio 0.78, 95% CI 0.61-0.99, p=0.044), with a similar benefit for cardiovascular death or myocardial infarction (0.74, 0.56-0.97, p=0.030). 234 (102 [12%] intervention, 132 [15%] conservative) patients died during follow-up (0.76, 0.58-1.00, p=0.054). The benefits of an intervention strategy were mainly seen in patients at high risk of death or myocardial infarction (p=0.004), and for the highest risk group, the odds ratio of death or non-fatal myocardial infarction was 0.44 (0.25-0.76). INTERPRETATION: In patients with non-ST-elevation acute coronary syndrome, a routine invasive strategy leads to long-term reduction in risk of death or non-fatal myocardial infarction, and this benefit is mainly in high-risk patients. The findings provide support for national and international guidelines in the need for more robust risk stratification in acute coronary syndrome.

The future role of surgery in ischaemic heart disease.

The ability to restore myocardial perfusion in ischaemic heart disease has been one of the triumphs of surgery. Alternative, less invasive catheter-based methods have now taken the lead as favoured treatment. The resultant threat to surgical practice, as well as societal and organisational issues that impact on the life of surgeons, have caused many to question the future role of surgery in ischaemic heart disease. In spite of general awareness of risk factors, there is little to suggest that coronary disease will soon disappear; rather, obesity and unfavourable life-style of many will continue to recruit further patients and, additionally, an epidemic of heart failure is anticipated. At the same time, rapid advance in knowledge of the underlying disease is opening the prospect for more effective intervention for unstable coronary plaque. Of great relevance to the surgeon are recent advances in knowledge and technology that will lead to gene and cell-based therapy for ischaemic heart disease. The ability to modify or augment activity of myocytes in heart failure, and to promote angiogenesis, offers hope for repair of ischaemically damaged hearts undreamed of only a few years ago. Tissue engineering, encompassing gene and cell-based therapy, holds promise of reconstruction of the myocardium and its vasculature. Temporary cardiovascular support to enable application of these techniques will very likely provide one role for surgery. More importantly, the need to ensure optimal anatomic and functional repair will surely give rise to a new generation of surgeons with much expanded scientific and technical support to draw upon, and will ensure an important role for surgery in ischaemic heart disease for decades to come.

Fish oil before cardiac surgery: neutrophil activation is unaffected but myocardial damage is moderated.

Could pre-operative dietary intervention with fish oil reduce neutrophil activation and myocardial damage associated with cardiopulmonary bypass (CPB)? Patients were randomised to receive either 8 g/day fish oil (n=22) or placebo (n=18) for 6 weeks. Neutrophil activation, apoptosis and cardiac damage were measured. Demographics and operative variables were similar. Fish oil diet decreased plasma VLDL from 0.69+/-0.34 to 0.51+/-0.24 mmol/l and triglycerides from 1.68+/-0.70 to 1.39+/-0.54 mmol/l. HDL cholesterol increased from 0.94+/-0.27 to 1.03+/-0.26 mmol/l demonstrating significant treatment effects (P=0.007, 0.02 and 0.0003, respectively) as well as compliance with treatment. There were no significant differences in ex vivo N-formyl-methionyl-leucyl-phenylalanine-stimulated neutrophil superoxide anion generation or myeloperoxidase release at recruitment, pre-operatively and at end-CPB. Apoptosis at end-CPB was equally reduced in both groups from 23+/-9% to 13+/-4% in the fish oil group (P<0.001) and 35+/-14% to 15+/-3% in the placebo group (P=0.001). At end-CPB overall troponin I levels averaged 0.91+/-0.60 ng/ml which clearly exceeded diagnostic levels (0.15 ng/ml). At 24h troponin I fell significantly in the fish oil group to 46+/-23% of end-CPB levels (P=0.0002) whereas it peaked in the placebo group to 107+/-72% (P=0.098 vs. end-CPB); this difference was significant: P=0.013. At 48 h the placebo-treated patients had higher troponins but not significantly so (P=0.059). Area-under-the-curve analysis did not conclusively support this (P=0.068). We conclude that fish oil did not significantly decrease post-CPB neutrophil activation (as detected ex vivo) but may moderate post-operative myocardial damage.

Modelling chorded prosthetic mitral valves using the immersed boundary method.

The Immersed Boundary (IB) Method is an efficient method of modelling fluid structure interactions. However, it has two main limitations: ease of use and ability to model static loading. In this paper, the method is developed, so that it can efficiently and easily model any multileaflet elastic structure. The structure may include chordae, which attach to the leaflets and continue through the leaflet surfaces. In addition, an external surface pressure may be applied to the leaflets, thus enabling the deformations that arise under steady loads to be solved. This method is validated for a model of the native mitral valve under systolic loading and for a prosthetic aortic valve under static loading. It is then applied to a new chorded prosthetic mitral valve, housed in a cylindrical tube, subject to a physiological periodic fluid flow. Results are compared with those obtained by using the commercial package ANSYS as well as with experimental measurements. Qualitative agreements are obtained. There are some discrepancies due to the current IB method being unable to model bending and shear behaviour. In particular, the fibre structures of the new prosthetic valve model developed using the IB method may be prone to crimping. Further development of the IB method is necessary to include bending effects. This will improve the accuracy of both the dynamic and static analysis.

Twenty year comparison of a Bjork-Shiley mechanical heart valve with porcine bioprostheses.

OBJECTIVE: To compare survival and outcome in patients receiving a mechanical or bioprosthetic heart valve prosthesis. DESIGN: Randomised prospective trial. SETTING: Tertiary cardiac centre. PATIENTS: Between 1975 and 1979, patients were randomised to receive either a Bjork-Shiley or a porcine prostheses. The mitral valve was replaced in 261 patients, the aortic in 211, and both valves in 61 patients. Follow up now averages 20 years. MAIN OUTCOME MEASURES: Death, reoperation, bleeding, embolism, and endocarditis. RESULTS: After 20 years there was no difference in survival (Bjork-Shiley v porcine prosthesis (mean (SEM)): 25.0 (2.7)% v 22.6 (2.7)%, log rank test p = 0.39). Reoperation for valve failure was undertaken in 91 patients with porcine prostheses and in 22 with Bjork-Shiley prostheses. An analysis combining death and reoperation as end points confirmed that Bjork-Shiley patients had improved survival with the original prosthesis intact (23.5 (2.6)% v 6.7 (1.6)%, log rank test p < 0.0001); this difference became apparent after 8-10 years in patients undergoing mitral valve replacement, and after 12-14 years in those undergoing aortic valve replacement. Major bleeding was more common in Bjork-Shiley patients (40.7 (5.4)% v 27.9 (8.4)% after 20 years, p = 0.008), but there was no significant difference in major embolism or endocarditis. CONCLUSIONS: Survival with an intact valve is better among patients with the Bjork-Shiley spherical tilting disc prosthesis than with a porcine prosthesis but there is an attendant increased risk of bleeding.

Protecting the damaged heart during coronary surgery.

In coronary surgery, protective strategies that offer adequate safety for patients with healthy ventricles may not be adequate for those with severe impairment of ventricular function.

Are we negating the benefits of CABG by forgetting secondary prevention?

UNLABELLED: The objective of the study was to examine medically managed secondary prevention at one year after coronary artery bypass grafting (CABG). In all, 214 consecutive patients undergoing isolated elective CABG seen four weeks preoperatively and one year post-operatively. Preoperative systolic blood pressure averaged 135+/-20 mmHg, which increased to 148+/-25 mmHg (P<0.0001) as did diastolic pressure (81+/-12 to 87+/-13 mmHg; P<0.0001). Anginal symptoms were reported by 45.1% (P<0.0001) although median severity scored lower (4.0 [3.0-5.4] vs 0 [0-2.0]; P<0.0001). Breathlessness decreased from 93% to 64% (P<0.0001) and was scored less severely (4.0 [2.0-5.0] vs 2.0 [0-4.0]; P<0.0001. In all, 88% with postoperative angina reported dyspnoea against 44% of those without (P<0.0001). Calcium antagonist use was more common in patients with angina (27.2% vs 5.1%; P<0.0001), but not nitrates (P=0.8695), diuretics (P=0.4218), digoxin (P=0.2565), beta-blockers (P=0.0820), or ACE inhibitors (P=0.7256). Preoperatively 166 patients (80.2%) took aspirin vs 69.2% afterwards (P=0.0131). Twelve patients (6.5%) received warfarin after operation vs none preoperatively. Two took digoxin (0.97%) preoperatively and 14 (7.7%) postoperatively (P=0.001) for chronic atrial fibrillation. One of these took warfarin. Long-acting nitrate use fell from 63.4% to 15.8% (P <0.0001). Short-acting nitrate use fell similarly (P<0.0001). Preoperatively 37 patients (17.9%) took ACE inhibitors vs 44 postoperatively (24.2%); 39 had not received them before. Preoperatively 48 (23.2%) took diuretics vs 30 (16.5%) postoperatively (P=0.127); 24 had not previously taken diuretics. More patients took HMGCoA inhibitors postoperatively (P=0.0068) and total cholesterol was significantly reduced with a concomitant increase in HDL fraction. Smoking habit was virtually unchanged from 17.8% to 15.1% (P=0.5023). IN CONCLUSION: angina was common. Apart from statin prescribing, postoperative secondary prevention measures were poorly applied, less widespread and less effective than preoperatively. The implications are disturbing.

Coronary artery surgery at the dawn of the 21st century.

Since the 1970's coronary bypass surgery has evolved to become one of the commonest and most successful of all operative procedures. The symptomatic and survival benefit of this surgery is well recognised. However, developments in cardiological interventions, coupled with demographic and lifestyle changes, are altering the patient profile and referral pattern. Coronary surgery at the beginning of the new century frequently involves higher risk patients and more complex surgery as a result of changes in disease presentation and the success of competing cardiological interventional techniques for less extensive disease. Technological advances in endovascular devices are making significant inroads into traditional coronary surgical practice. Surgeons have responded by developing new strategies to maximise effectiveness of coronary surgery and minimise the injury associated with cardiopulmonary bypass. At the same time regulatory and media scrutiny is focussing attention on the cardiac surgeon, further adding to the stresses and complexity of cardiac surgical practice

Interventional versus conservative treatment for patients with unstable angina or non-ST-elevation myocardial infarction: the British Heart Foundation RITA 3 randomised trial. Randomized Intervention Trial of unstable Angina.

BACKGROUND: Current guidelines suggest that, for patients at moderate risk of death from unstable coronary-artery disease, either an interventional strategy (angiography followed by revascularisation) or a conservative strategy (ischaemia-driven or symptom-driven angiography) is appropriate. We aimed to test the hypothesis that an interventional strategy is better than a conservative strategy in such patients. METHODS: We did a randomised multicentre trial of 1810 patients with non-ST-elevation acute coronary syndromes (mean age 62 years, 38% women). Patients were assigned an early intervention or conservative strategy. The antithrombin agent in both groups was enoxaparin. The co-primary endpoints were a combined rate of death, non-fatal myocardial infarction, or refractory angina at 4 months; and a combined rate of death or non-fatal myocardial infarction at 1 year. Analysis was by intention to treat. FINDINGS: At 4 months, 86 (9.6%) of 895 patients in the intervention group had died or had a myocardial infarction or refractory angina, compared with 133 (14.5%) of 915 patients in the conservative group (risk ratio 0.66, 95% CI 0.51-0.85, p=0.001). This difference was mainly due to a halving of refractory angina in the intervention group. Death or myocardial infarction was similar in both treatment groups at 1 year (68 [7.6%] vs 76 [8.3%], respectively; risk ratio 0.91, 95% CI 0.67-1.25, p=0.58). Symptoms of angina were improved and use of antianginal medications significantly reduced with the interventional strategy (p<0.0001). INTERPRETATION: In patients presenting with unstable coronary-artery disease, an interventional strategy is preferable to a conservative strategy, mainly because of the halving of refractory or severe angina, and with no increased risk of death or myocardial infarction.

Nurse led shared care for patients on the waiting list for coronary artery bypass surgery: a randomised controlled trial.

OBJECTIVE: To evaluate the effectiveness of a nurse led shared care programme to improve coronary heart disease risk factor levels and general health status and to reduce anxiety and depression in patients awaiting coronary artery bypass grafting (CABG). DESIGN: Randomised controlled trial. SETTING: Community, January 1997 to March 1998. STUDY GROUPS: 98 (75 male) consecutive patients were recruited to the study within one month of joining the waiting list for elective CABG at Glasgow Royal Infirmary University NHS Trust. Patients were randomly assigned to usual care (control; n = 49) or a nurse led intervention programme (n = 49). INTERVENTION: A shared care programme consisting of health education and motivational interviews, according to individual need, was carried out monthly. Care was provided in the patients' own homes by the community based cardiac liaison nurse alternating with the general practice nurse at the practice clinic. OUTCOME MEASURES: Smoking status, obesity, physical activity, anxiety and depression, general health status, and proportion of patients exceeding target values for blood pressure, plasma cholesterol, and alcohol intake. RESULTS: Compared with patients who received usual care, those participating in the nurse led programme were more likely to stop smoking (25% v 2%, p = 0.001) and to reduce obesity (body mass index > 30 kg/m(2)) (16.3% v 8.1%, p = 0.01). Target systolic blood pressure improved by 19.8% compared with a 10.7% decrease in the control group (p = 0.001) and target diastolic blood pressure improved by 21.5% compared with 10.2% in the control group (p = 0.000). However, there was no significant difference between groups in the proportion of patients with cholesterol concentrations exceeding target values. There was a significant improvement in general health status scores across all eight domains of the 36 item short form health survey with changes in difference in mean scores between the groups ranging from 8.1 (p = 0.005) to 36.1 (p < 0.000). Levels of anxiety and depression improved (p < 0.000) and there was improvement in time spent being physically active (p < 0.000). CONCLUSIONS: This nurse led shared care intervention was shown to be effective for improving care for patients on the waiting list for CABG.

Platelet aggregatory responses to low-dose collagen are maintained in hirudin-anticoagulated whole blood for 24 h when stored at room temperature.

Whole blood from 15 volunteers was anticoagulated with hirudin (200U/l) and the response to a known submaximal concentration of collagen (0.6 microg/ml) was tested by impedance aggregometry. In 8 volunteers platelet counts were also taken before and after the maximum aggregatory response. These tests were repeated when the samples had rested for 24 h at room temperature. The median [interquartile range] aggregatory response immediately after sampling was 17.3 [16.7-18.4] ohms. At 24 h it was 17.7 [15.8-19.3] ohms (p = 0.88) although variance was increased (p = 0.006). The immediate platelet count before collagen exposure was 438 [381-510] x 10(9)/l and 258 [227-297] x 10(9)/l post-collagen. At 24 h the platelet count was 448 [443-473] x 10(9)/l (p = 0.224 versus immediate count) but variance was not increased (p = 0.215). After full aggregation the count fell to 284 [234-304] x 10(9)/l (p = 0.592 versus early post-collagen). Variances were similar (p = 0.558). Aggregate response ratios increased non-significantly after 24 h from 0.59 [0.53-0.62] to 0.64 [0.51-0.68] although variance was increased (p = 0.021). Full macroaggregatory responses by impedance aggregometry were seen after 24h storage of whole blood with hirudin at room temperature. This suggests both that distant assessment of platelet function using a standardized method is possible and a potential role of thrombin inhibition for platelet storage.

Hydrodynamic function of a biostable polyurethane flexible heart valve after six months in sheep.

Survival to six months for sheep with a non-biostable polyurethane mitral heart valve prosthesis has been reported previously, however, with surface degradation and accumulation of calcified fibrin/thrombus that impaired leaflet motion and compromised hydrodynamic function. Newly available biostable polyurethanes may overcome this problem. Six adult sheep with biostable polyurethane trileaflet heart valve prostheses of documented hydrodynamic performance, implanted in the mitral position, were allowed to survive for 6 months. Explanted valves were photographed, resubmitted to hydrodynamic function testing, and studied by light and electron microscopy. Explanted valves were structurally intact and differed little in appearance from their preimplant state. Hydrodynamic testing showed no deterioration in pressure gradient or energy losses compared with pre-implant values. Biostable polyurethanes demonstrated improved blood compatibility leaving leaflets flexible and valve function unimpaired. Biostable polyurethanes may thus improve prospects for prolonged function of synthetic heart valve prostheses.

A new design for polyurethane heart valves.

BACKGROUND AND AIM OF THE STUDY: The synthetic flexible tri-leaflet heart valve offers considerable potential for improvement in both hydrodynamic and biomechanical performance of replacement heart valves. To date, success with the synthetic leaflet heart valve has been limited, partly due to limitations in the biostability of the polyurethanes used. With the synthesis of new biostable polyurethanes, the integration of advancing technology, and better knowledge of the functional and biomechanical design requirements necessary to increase the long-term durability of the polyurethane heart valve, novel clinical solutions are now in sight. METHODS: This study describes the design characteristics, hydrodynamic and biomechanical performance of a new design of polyurethane heart valve. The function and durability characteristics of this novel design of heart valve, manufactured using a proven durable non-biostable polyurethane, was compared with that of a single AorTech porcine bioprosthetic heart valve and a single tilting disc mechanical heart valve, the Björk-Shiley Monostrut valve (BSM), of similar size. RESULTS: For equivalent sizes of valve, the new polyurethane heart valve design had significantly lower pressure gradients compared with the porcine valve at all flow rates and to the BSM valve at the higher flow rates. The effective orifice area of the polyurethane valve was greater than the other two valves studied; regurgitation and total energy loss were less. The new polyurethane valve design reached over 360 million cycles in an accelerated durability tester, without failure. CONCLUSION: This new design of polyurethane heart valve showed improved hydrodynamic function in comparison with either the porcine bioprosthetic or the BSM mechanical heart valve. The pulsatile flow results showed a lower total energy loss associated with this valve, indicating improved potential patient benefit. The durability of this new design of polyurethane heart valve was demonstrated when manufactured using a medical-grade polyurethane.

The influence of general health status and social support on symptomatic outcome following coronary artery bypass grafting.

OBJECTIVES: To assess health status, level of social support, and presence of coronary artery disease risk factors before and after coronary artery bypass grafting (CABG); to assess symptomatic relief approximately 12 months postoperatively; and to examine the association between preoperative health status and recurrence of symptoms. DESIGN: Observational study. SETTING: Preoperatively, in hospital outpatient department (1995-1996); postoperatively, at home (1996-97). SUBJECTS AND METHODS: Patients awaiting elective CABG were recruited one month before the expected date of operation. Preoperative assessment included severity of symptoms, coronary artery disease risk factors, short form 36 (SF-36) questionnaire, and social activities questionnaire. The presence and severity of angina and breathlessness were reported postoperatively (mean 16.4 months). Multiple regression analysis was used to identify factors associated with improved outcome following CABG. MAIN OUTCOME MEASURE: Patient reported presence and severity of angina and breathlessness. RESULTS: 183 patients were followed for a mean of 16. 4 months after CABG. Angina and breathlessness were completely relieved in 55% and 36% of patients, respectively. In patients with residual symptoms, the severity was significantly reduced (angina p < 0.001; breathlessness, p = 0.02). Patients with low SF-36 scores and low social network scores preoperatively were less likely to be relieved of symptoms (p < 0.001). Health status and social support levels preoperatively were lower than in other reported coronary artery disease patients groups. Preoperatively, coronary artery disease risk factors were higher than recommended in current guidelines: 67.4% had raised plasma cholesterol, 39.0% were hypertensive, 80% were moderately obese, and 22.9% were smokers. CONCLUSIONS: Recurrence of symptoms exceeded other published studies. Patients' perception of general health, symptoms, and social support influences outcome.