Biomedical subjects
Publications and source records attributed to S Westaby.
Surgical reduction has been proposed to reduce left ventricular wall stress and improve geometry in patients with left ventricular failure. We describe 2 cases of direct surgical reduction in ischemic cardiomyopathy. Although left ventricular function improved in both, late ventricular dysrhythmia negated the result.
We describe a patient with congenital absence of a single pulmonary valve cusp. A monocusp aortic homograft was used to repair the valve.
The management of prosthetic graft infection is still challenging. We report in situ repair of an infected mediastinal false aneurysm by ascending aortic replacement with a fresh aortic homograft.
Congenital diverticulum of the left ventricle is rare, and rupture of such a diverticulum is even more rare. We describe successful surgical repair of a ruptured left ventricular diverticulum in an 11-month-old infant.
BACKGROUND: We consider operative survival as the primary objective in acute type A dissection and believe that virtually all native aortic valves can be conserved. We sought to answer the question: "Does glue repair improve the long-term stability of proximal aortic repair?" METHODS: We retrospectively studied 64 patients with an acute type A dissection, an ascending aortic tear, and aortic regurgitation operated on by the same surgeon between 1988 and 1996. Three had Marfan's syndrome and 2 had a bicuspid valve. The valves in all patients without Marfan's syndrome were repaired with gelatin-resorcinol-formol glue. The valve and root were reinvestigated by echocardiography. Some patients underwent nuclear magnetic resonance imaging. RESULTS: There were four hospital (6%) and three late deaths. Aortic root reoperation was required in 2 of the 60 survivors (3.3%) and operation on the distal aorta in 2. Root reoperations were required within 3 years. The remaining proximal repairs remained stable. CONCLUSIONS: The native aortic valve can be conserved in most patients, and glue repair is durable. Simple root repair is associated with a low operative mortality.
BACKGROUND: Recent reports have documented left ventricular recovery in patients with dilated cardiomyopathy off-loaded long term with a left ventricular assist device. We sought to document the natural history of left ventricular recovery. METHODS: We implanted the TCI left ventricular assist device without the intention to perform transplantation in 2 patients with dilated cardiomyopathy who had been rejected for transplantation. Both were in New York Heart Association functional class IV and had renal failure. One was a diabetic. We studied left ventricular function with detailed echocardiography at 4, 6, and 8 weeks postoperatively. RESULTS: With the left ventricular assist device turned off, we observed a progressive increase in myocardial contractility beginning as early as 4 weeks after implantation and improving progressively. Histologic examination showed resolution of myocytolysis in both patients. CONCLUSIONS: Left ventricular recovery begins earlier than was previously suspected. Mechanical bridge to myocardial recovery is a potential approach to therapy for such patients.
METHODS: We developed a system for mechanical circulatory support based on the Jarvik 2000 intraventricular axial flow impeller pump (Jarvik Research, Inc., New York, N.Y.) and percutaneous electric power. The adult pump provides flow at a rate up to 10 L/min with an energy requirement of 7 to 10 watts. The device was implanted into the apex of the left ventricle through a left thoracotomy without cardiopulmonary bypass. A Dacron graft conveyed blood to the descending thoracic aorta. In patients, we will use a skull-mounted carbon pedestal to transmit fine electric wires through the scalp skin. Being highly vascular, the scalp skin is resistant to infection. RESULTS: We tested 16 adult systems and one pediatric system in 17 adult ewes weighing between 60 and 90 kg. Five died of perioperative complications. Twelve survived between 3 and 198 days (mean 44 days) with a functioning device. None of the sheep could receive adequate anticoagulation with warfarin (INR 1.0 to 1.5). Acute thrombotic occlusion occurred after a 3-hour power loss in one device (46 days) but was cleared with streptokinase. In a second animal with endocarditis, the pump inflow became occluded with vegetations. No other device-related problems or important hemolysis developed despite pump speeds between 10,000 and 18,000 rpm. Renal function remained normal in all animals. Autopsy studies showed no pannus ingrowth at the device inflow despite the restrictive left ventricular cavity size. No sign of thromboembolism could be detected in the brains or kidneys. CONCLUSION: Our findings indicate the Jarvik 2000 Oxford System to be a safe and effective circulatory assist device. Potential uses include permanent circulatory support, bridge to transplantation, or bridge to myocardial recovery in acute or chronic left ventricular failure.
INTRODUCTION: Embolization of gaseous and particulate matter is incriminated in the neuropsychological morbidity of CPB and can be reduced by membrane oxygenators and arterial line filtration. It is not known if the use of arterial line filtration in conjunction with membrane oxygenators might have an additive effect in reducing cerebral injury. METHODS: Forty patients undergoing elective coronary artery surgery were prospectively randomized to a 43 microns heparin coated arterial line filter (Cobe Sentry) or to no filtration (control group). All operations were performed by one surgeon (DPT) using intermittent ischaemia with nonpulsatile CPB, a COBE CML membrane oxygenator and alpha-stat paCO2 management. Flow rates were maintained between 2.0 and 2.4 l-1 m2 per min with a perfusion pressure of 50-80 mmHg and a systemic temperature of 34 degrees C. Cerebral injury was defined by careful neurological examination and serial measurement of the serum concentration of S-100 protein (a highly specific astroglial cell derivative, elevated serum levels of which correlate with proven cerebral injury). RESULTS: There was no difference [mean (S.D.)] in the control and filter groups with respect to age [61(9) vs. 62(9) years], ejection fraction, number of grafts [2.8(0.6) vs. 2.6(0.7)] or CPB times [55(19) vs. 57(18) min]. Preoperatively, no patient had detectable S-100. In the postoperative period 23 of 40 patients (58%) showed elevated S-100 levels. At 1, 5 and 24 h the respective number of patients in the control and filter groups with elevated S-100 was (14 vs. 9), (4 vs. 0), (4 vs. 0)) (P < 0.05). No patient had overt cerebral injury. CONCLUSIONS: This study suggests that (i) subclinical cerebral injury is common (58% of patients in this study) even after apparently uncomplicated surgery with short CPB times; (ii) serum S-100 protein is a valuable marker for investigating potentially cerebral protective innovations during CPB; and (iii) arterial line filtration significantly reduces but does not eliminate cerebral injury.
OBJECTIVE: To assess how left ventricular (LV) hypertrophy, geometry and function change after stentless aortic valve replacement for aortic stenosis, and to elucidate the physiological mechanism of the improvement in stentless valve haemodynamics. METHODS: 81 patients with aortic stenosis (age 75 +/- 6 years, 47 male) underwent aortic valve replacement (plus CABG in 33 patients) with a Freestyle stentless porcine valve (mean size 23 +/- 2 mm). They were prospectively investigated by Doppler echocardiography at 2 weeks, 3-6, 12, and 24 months after operation. Two hundred and forty-six echocardiograms were obtained and analysed. Aortic valve performance was assessed from its effective orifice area (EOA), the transvalvular increase in mean flow velocity (delta mV), the deceleration time of aortic flow velocity, and mean pressure drop (mPG). LV hypertrophy was assessed from LV mass index; LV geometry, from the ratio of wall thickness to the radius (T/R ratio) and LV function, from stroke volume index (LVSVI) and myocardial stroke work (SW). RESULTS: By 2 years after operation, LV mass index had fallen from 162 +/- 64 to 109 +/- 36, g/m2, and T/R ratio from 0.61 +/- 0.25 to 0.43 +/- 0.10. LVSVI increased from 29.4 +/- 10 to 42 +/- 17, ml/m2, and myocardial SW from 3.1 +/- 1.6 to 5.2 +/- 2.2, mJ/cm3 (all P < 0.001 by ANOVA), while LV outflow tract diameter remained unchanged. At the same time, stentless valve EOA increased from 1.59 +/- 0.75 to 2.2 +/- 0.72, cm2, and delta mV (from 82 +/- 31 to 49 +/- 24, cm/s) and mPG (from 9.7 +/- 5.0 to 5.2 +/- 3.7 mmHg) both fell significantly (all P < 0.001 by ANOVA): as the deceleration time of aortic flow velocity increased from 153.6 +/- 64.1 to 202.7 +/- 37.6 ms (P < 0.001 by ANOVA). CONCLUSION: After stentless aortic valve replacement, LV mass index and wall thickness both fall towards normal, and myocardial stroke work increases. These ventricular remodelling processes are accompanied by a more physiological flow jet at valve cusp level, which permits a greater stroke volume to be ejected with a smaller transvavular velocity increase, so that effective orifice area increases.
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Extensive thoracic aortic resections often require a period of profoundly hypothermic circulatory arrest. The extent of surgical dissection, damaging effects of cardiopulmonary bypass, and coagulation disturbances of hypothermia predispose to bleeding. Although impervious vascular grafts and biological glues have made an important contribution to eliminating the vicious cycle of transfusion of stored blood and worsening coagulopathy, hemorrhage remains an important cause of morbidity in these patients. Thrombin generation by activation of the coagulation cascades also leads to excessive fibrinolytic activity with the potential to disrupt the hemostatic process. Pharmacological antifibrinolytic therapy with aprotinin or other agents has been shown to preserve hemostasis, but the efficacy of antifibrinolytic therapy remains unproven in thoracic aortic operations with hypothermic circulatory arrest. This report discusses the interactions of hypothermia with the coagulation system, together with the efficacy of fibrinolytic therapy from existing surgical experience.
BACKGROUND: There is no simple method to determine the incidence or severity of brain injury after a cardiac operation. A serum marker equivalent to cardiac enzymes is required. S100 protein leaks from the cerebrospinal fluid to blood after cerebral injury. We sought to determine the pattern of release after extracorporeal circulation (ECC). METHODS: Thirty-four patients without neurologic problems underwent coronary bypass using ECC. Four had carotid stenoses. Nine others underwent coronary bypass without ECC. Serum S100 levels were measured before, during, and after the operation. RESULTS: S100 was not detected before sternotomy. Postoperative levels of S100 were related to duration of perfusion (r = 0.89, p < 0.001). Patients who did not have ECC had undetectable or fractionally raised levels except in 1 who suffered a stroke. No patient in whom ECC was used suffered an event, but those with carotid stenosis had greater S100 levels. CONCLUSIONS: S100 protein leaks into blood during ECC and may reflect both cerebral injury and increased permeability of the blood brain barrier. S100 is a promising marker for cerebral injury in cardiac surgery if elevated levels can be linked with clinical outcome.
Despite the incidence of heart disease during pregnancy falling to 1.5% over the last 25 years, when a cardiac operation is required the risk is obviously greater as two lives are at risk. The risk to the mother is now similar to that for nonpregnant female patients (3% overall) but the fetal mortality remains high (19%). Cardiac operation is ill advised except in extreme emergencies during the first two trimesters as the incidence of teratogenesis is high. During the third trimester, with improvements in the outcome for premature infants with modern neonatal intensive care, delivery of the child immediately before commencing cardiopulmonary bypass is a safe option. If this is inappropriate, high-flow, high-pressure, normothermic bypass for as brief a period as possible should be used. However, although it has theoretic advantages, the benefit of pulsatile perfusion is unproven. The fetal response to cardiopulmonary bypass is bradycardia thought to be due to hypoperfusion secondary to uterine contractions, and this dysrhythmia is reversible by increasing the perfusion rate. Fetal heart rate monitoring is therefore essential to allow these manipulations. The response of the fetoplacental unit is more complex, comprising two elements: an early vasoactive response is due to prostaglandin synthesis, whereas a more profound late acidosis appears to be related to a fetal stress response. Whether these responses can be modified by changes in our approach to cardiopulmonary bypass in pregnant women remains to be proven. Finally, uterine contractions occur in response to bypass, possibly due to a dilutional effect from the stabilizing influence of progesterone. Various techniques to modify this include the administration of progesterone, beta2-agonists, and intravenous alcohol, all with some effect. Uterine monitoring is essential to allow early control of these contractions as they are associated with significant fetal loss.
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OBJECTIVE: We sought to evaluate the ATS open pivot bileaflet valve with respect to haemodynamics and thromboembolism. METHODS: We prospectively studied 200 consecutive patients aged 13-80 years. One hundred and nineteen aortic, 103 mitral and 11 tricuspid valves were replaced in 172 single, 23 double and 5 triple valve procedures. Thirty-eight were re-operations and 51 underwent coronary bypass. Transvalvular gradients were determined by transoesophageal and transthoracic echocardiography. Patients were followed for 12 months to 3 years. RESULTS: There were four hospital (2%) and three late deaths, each non-valve related. Two patients were reoperated for partial valve dehiscence. One aortic reoperation patient suffered a potential transient thromboembolic event. One tricuspid prosthesis thrombosed after anticoagulation was discontinued but thrombolysis resolved this problem. There were no other thromboembolic events. Valve gradients were equivalent or better than those for other bileaflet valves. CONCLUSIONS: The ATS valve has excellent haemodynamic characteristics and a very low thromboembolic rate, probably related to the convex self-washing hinge mechanism. Consequently, we have reduced anticoagulant levels to INR (international normalised ratio) 1.5 to 2.0 for aortic valve patients in sinus rhythm. Early experience suggests that the ATS valve functions well in the tricuspid position.
OBJECTIVE: To determine late patency of the aortic false lumen and propensity for aneurysm formation after repair of type A dissection. DESIGN: Retrospective follow up study. SETTING: Regional cardiac surgical unit. PATIENTS: 28 patients after repair of type A dissection. METHODS: Magnetic resonance imaging (MRI) was performed between 6 weeks and 12 months after operation. RESULTS: A patent distal false lumen with demonstrable blood flow was found in 22 patients (78%). Only six patients had complete obliteration of the false lumen by thrombus. The conduct of operation did not influence this. Nine patients (32%) showed aneurysmal dilatation of the false lumen and three had a repeat operation. CONCLUSIONS: So-called "successful repair" of aortic dissection does not obliterate the distal false lumen. MRI is a safe and effective radiological procedure for determining patency and dilatation in the false lumen. Patients with type A dissection with blood flow in the false lumen should be studied every 6 months to look for aneurysmal dilatation.
Surgery for degenerative mitral regurgitation has become complex. Preservation of annulo-ventricular continuity through the chordae tendineae is an important determinant of operative survival, postoperative left ventricular function, long-term survival, and quality of life. Some cardiologists believe that NYHA I function is never achieved after conventional mitral replacement with chordal transection. Valve repair is the procedure of choice but when valve replacement is inevitable every effort should be made to preserve the posterior leaflet and its chordal attachments. Valve replacement with preservation of the subvalvar apparatus provides a functional outcome similar to that after valve repair but usually leads to life long anti-coagulation.