Biomedical subjects
Publications and source records attributed to S Westaby.
We describe a novel method for surgical repair of giant right coronary aneurysm. Instead of aneurysm ligation and coronary bypass we mobilized the inflow and outflow and performed end-to-end anastomosis. This preserved the native vessel. Restudy in both patients confirmed the effectiveness of this technique.
We describe a technique to transfer an anomalous left coronary artery originating in the left posterior pulmonary sinus to the aorta. Both autogenous aortic and pulmonary arterial flaps create an extended left main stem without the disadvantages of standard rerouting techniques and full potential for growth remains.
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The objective of this study was to determine normal Doppler and 2-dimensional characteristics of the Freestyle stentless aortic bioprosthesis. The Freestyle aortic bioprosthesis is a new type of aortic xenograft, and experience is limited. We therefore determined the normal range of echocardiographic and Doppler examinations of this valve. Three hundred thirty-nine consecutive patients with a Freestyle aortic bioprosthesis underwent an echocardiographic and Doppler examination according to a common protocol. Investigations were done within 4 weeks after operation, after 3 to 6 months, and after 1, 2, and 3 years. With a valve size from 19 to 27 mm, mean gradients decreased from 7.9 +/- 5.1 mm Hg at discharge to 5.5 +/- 3. 8 mm Hg after 3 to 6 months (P <.001). Thereafter, gradients remained stable. Effective orifice area 1 year after implantation was 1.59 +/- 0.58 cm(2) for the 21-mm valves, 1.92 +/- 0.74 cm(2) for the 23-mm valves, 2.03 +/- 0.64 cm(2) for the 25-mm valves, and 2.52 +/- 0.72 cm(2) for the 27-mm valves (P <.001). The performance index, the ratio of the measured effective orifice area in the patient divided by the effective orifice area measured in vitro, increased from 67% +/- 20% at discharge to 82% +/- 29% after 1, 2, and 3 years. Performance index was especially very high in the smaller-sized valves. After implantation with the subcoronary technique or root-inclusion technique, small cavities could be seen between the native aortic root and the Freestyle valve. Doppler values were evaluated for the Freestyle stentless porcine bioprostheses in the aortic root. Gradients appear to be close to those measured in native valves over a time period of 3 years.
OBJECTIVE: Although cannulation of the femoral artery is used routinely for thoracic aortic operations with hypothermic circulatory arrest, retrograde perfusion through the descending aorta carries the risk of cerebral malperfusion or embolism. We have, therefore, routinely used a central cannulation technique for distal arch and descending aortic operations since 1995. In this study, we compared neurological outcome in consecutive patients undergoing femoral versus ascending aortic perfusion for these aneurysms. METHODS: Between 1987 and 1998, 61 patients underwent aortic resection with circulatory arrest, but without retrograde cerebral perfusion, for lesions of the aortic arch and descending aorta. Thirty-one patients had fusiform true aneurysms, 19 had aortic dissection and 11 had extensive saccular or false aneurysms. Thirty-two patients (52%) were perfused via the femoral artery (group A), and 29 patients (48%) from the ascending aorta (group B). Operative mortality and morbidity, and neurological outcome, were reviewed. RESULTS: There were no differences between the groups in mean age, pathology, abdominal and peripheral vascular disease, net perfusion time, or circulatory arrest time. There were four hospital deaths (three in group A and one in group B; P = 0.61), including one neurological death in group A, group A suffered a higher incidence of neurological events (nine patients: 28%) than group B (two patients: 7%; P = 0.03). Temporary focal neurological deficits occurred in both groups (two patients in group A, 6% and two patients in group B, 7%; P > 0.99), but permanent injury occurred exclusively in group A (seven patients: four with monoplegia, one with hemiplegia, and two with diffuse cerebral injury with one death; P = 0.01). CONCLUSIONS: Anterograde perfusion using a proximal aortic cannula provides a low risk of cerebral embolism and allows extensive aortic resection with low morbidity.
The unquestionable aims for a less invasive operations are less morbidity, less discomfort, and a reduced hospital stay through an operation which proves equally durable to the conventional approach. Such an operation must be carried out without further risk to the patient or increased difficulty for the surgeon. Whilst most definitions of less invasive coronary surgery include the phrase without cardiopulmonary bypass, this is clearly not yet possible in valve surgery. In valve surgery, the definition of less invasive relates only to the size of incision and rate of recovery. As a result of the discussions during the Heart Lab International Workshop on video-assisted heart surgery in Zürich, October 22-25, 1998, the following conclusions emerged. The partial upper sternotomy with J- or L- shaped extension to the right is the preferred approach for minimally invasive aortic valve surgery. Other methods which sacrify the internal thoracic arteries, open pleural cavities or predispose to long hernia are less satisfactory. A detailed description of the technique proposed is given and its indications and contraindications are discussed.
Adverse events during coronary artery bypass graft (CABG) surgery have been described in patients receiving angiotensin converting enzyme (ACE) inhibitors, including hypotension on induction of anaesthesia and an increase in vasoconstrictor requirements after cardiopulmonary bypass (CPB). Omitting regular ACE inhibitor medication before surgery may improve cardiovascular stability during anaesthesia. We evaluated prospectively the effect of omitting regular ACE inhibitor medication before CABG surgery on haemodynamic variables and use of vasoactive drugs. We studied 40 patients with good left ventricular function, allocated randomly to omit or continue ACE inhibitor medication before surgery. Arterial pressure, cardiac output, systemic vascular resistance and use of vasoactive drugs were recorded during anaesthesia and in the early postoperative period. Patients who omitted their ACE inhibitors had greater mean arterial pressure during the study and required less vasopressors during CPB. However, these patients required more vasodilators to control hypertension after CPB and in the early postoperative period. There was no difference in hypotension on induction of anaesthesia or in the use of vasoconstrictors after CPB. We conclude that omitting ACE inhibitors before surgery did not have sufficient advantage to be recommended routinely.
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A number of recent reports have suggested that valve design has an influence on long-term survival after aortic valve replacement (AVR). The present study examines the clinical results of two large multicenter trials of the Hancock II stented and Medtronic Freestyle stentless bioprosthetic valves. In all cases a subcoronary implant technique was used. All patients were operated on between 1991 and 1994, and all patients were monitored for 5 years. The 5-year actuarial survival rate was 86% for Freestyle and 77% for Hancock patients (P<.05). Late mortality occurred in 40 Freestyle patients (8.8%) compared with 36 Hancock II patients (16.1%, P = .0074). Cox's proportional hazard models were used to identify independent predictors of 5-year survival for the two groups. Hazard ratio (HR) and P value are presented in parentheses. The final analysis included the interactive variable valve*age. The resultant model indicates that the interaction of age and valve type has a significant effect on outcome. In patients < or =60 years of age at the time of operation, AVR with a Hancock II valves was associated with nearly a fivefold risk of death compared with patients of the same age who received a Freestyle valve (HR = 4.97, P = .0004). However, this survival advantage decreased by 50% with each decade thereafter (valve*age interaction HR = 0.50, P = .0027). Our data indicate that AVR with a stentless valve confers a survival advantage to the patient. The probability of dying within 5 years of surgery is 50% greater in patients who received a Hancock II versus a Freestyle valve (HR = 1.50, P = .0442). However, this survival advantage is most prominent in younger patients (<60 years of age) where the probability of death is fivefold greater with Hancock than Freestyle valves. With advancing age the benefits of stentless valves are diminished.
The Medtronic Freestyle aortic root bioprosthesis has been implanted in patients since August 1992. This study reviews clinical and echocardiographic results at midterm (5 years) after implantation. The Freestyle bioprosthesis was implanted in 1,100 patients in a 21-center Food and Drug Administration clinical trial from August 1992 to October 1998. The device was implanted (1) as a subcoronary valve replacement, (2) as a complete aortic root replacement (full-root), or (3) as a root inclusion. Patients were followed annually by clinical examination and echocardiography. There were 47 deaths early after operation (7.1%). There were 2,478 patient-years of follow-up during which there were 99 deaths or 4.0/pt.-yr. Before implantation, 73% of patients were in New York Heart Association functional class III or IV. After operation, 95% were in class I or II. Transvalvular gradient 4 years after operation was low (7.5+/-5.3 mm Hg) for all valve sizes (subcoronary implant). Small valves (19 and 21 mm) had mean gradients (10.2+/-3.0, 9.1+/-4.4 mm Hg). There was no or mild valve insufficiency in 98% of patients. Actuarial analysis at 5 years showed the rate for freedom from thromboembolism of 86% in subcoronary implant and 93% in full root replacement. Freedom from endocarditis was 98%. Freedom from reoperation for explant of the valve highest in patients having full root replacement (98%) and lower with root inclusion (94%). There were 20 bioprostheses explanted; 10 for endocarditis, 8 for technical reasons, and 2 for structural deterioration. The Medtronic Freestyle bioprosthesis (1) has excellent hemodynamic performance, (2) techniques for insertion that result in a competent valve, (3) low rates of thromboembolism and endocarditis, and (4) a rare rate of structural deterioration at 5 years.
Stentless porcine xenografts have had significant impact on the hemodynamics, left ventricular remodeling, and survival after aortic valve replacement. We sought to establish a similar trend for the stentless pericardial valve. In a consecutive unselected series of 54 patients over 65 years of age, we refined the implant method for the stentless aortic pericardial valve and defined the pitfalls. We used a detailed echocardiographic study designed by the Food and Drug Administration to define the early valve hemodynamics and changes in left ventricular function. The valve is user friendly. With an easily reproducible implant technique, very low mean (7.1+/-3.4 mm Hg) and peak (13.6+/-6.3 mm Hg) transvalvular gradients were obtained, which did not decline significantly with time. Left ventricular mass index declined accordingly over 6 months (147+/-49 g/m2 to 125+/-39 g/m2). Mild aortic regurgitation, which did not influence left ventricular mass regression, occurred (26%) predominantly in the first half of the series because of size discrepancy between the annulus and a dilated sinotubular junction. Aortic regurgitation was virtually eliminated by tailoring of the sinotubular junction in the noncoronary sinus. The stentless pericardial valve provides excellent early hemodynamics and is a realistic alternative to the stentless porcine xenograft or aortic homograft for subcoronary aortic valve replacement in elderly patients. Valve durability is yet to be defined.
The hemodynamic benefits of using stentless valves for replacement of the human aortic valve have become more well known. These devices are associated with significant decrease in left ventricular (LV) mass and LV remodeling in the early postoperative period. However, no large study has examined patient-related and valve-related factors that may contribute to this phenomenon. This study examined 1,103 patients who underwent aortic valve replacement (AVR) with a stentless porcine valve (Freestyle = 840, SPV = 263). In all cases, a subcoronary implant technique was used. Valve performance was assessed by serial echocardiograms. At 3 years' post-AVR, mean gradient was 6.3+/-5.0 mm Hg, and effective orifice area (EOA) was 2.0+/-0.7 cm2. Indexed EOA was 1.2+/-0.4 cm2/m2. There was an association between indexed EOA and the extent of LV mass regression. At 3 years after surgery, LV mass index (LVMI) was reduced to 76.3% to 78.7% of baseline in patients whose indexed EOA was >0.8 cm2/m2. In contrast, for patients with an indexed EOA that was <0.8 cm2/m2, LVMI at 3 years was 95.5% of baseline (P = .0001). Multiple linear regression models were used to identify parameters that predicted the 3-year LVMI. Baseline LVMI (P<.0001), prior myocardial infarction (P = .0009), male gender (P = .0036), and carotid stenosis (P = .022) were independent predictors of LV mass regression. Valve type, valve size, preoperative New York Heart Association class symptoms, coronary disease, prior bypass surgery, chronic obstructive pulmonary disease, or underlying valve pathology had no effect on LV mass regression. Data indicate that baseline LVMI and patient-prosthetic mismatch have major effects on the extent of LV mass regression post-AVR. Long-term hemodynamic benefits of AVR can be optimized by proper selection of the prosthesis so as to avoid mismatch. Furthermore, because the baseline LVMI affects the extent of regression post-AVR, early intervention may result in more complete resolution of LV mass postoperatively, which may have important prognostic implications.
The goal of this study was to characterize medium-term changes in aortic root geometry after stentless aortic valve replacement, the relationship between aortic sinotubular junction and the competence of stentless valves. A total of 205 consecutive patients (mean age 73+/-6 years; 120 men, 85 women) received a Freestyle stentless porcine aortic valve and were studied prospectively by echocardiography from 1 week to 5 years. Internal diameters of outflow tract, annulus, sinus, sinotubular junction, and ascending aortic root were measured at early ejection and indexed to stentless valve size. The degree of stentless valve regurgitation was semiquantified by color Doppler echocardiography. A total of 701 echocardiographic studies were obtained and analyzed; 73% showed a fully competent stentless valve (nAR) and 13% and 14%, respectively, showed a trivial (tAR) or mild (mAR) regurgitation. Sinotubular junction of tAR or mAR was significantly greater than that of nAR (111+/-1.9, 117+/-2.2 vs. 104+/-1.0, percentage of valve size, P<.001). A preoperative diagnosis of aortic regurgitation (110+/-2.6 vs. 104+/-1.0, percentage of valve size, P<.001) and 4 to 5-year follow-up time (116+/-2.2 vs. 107+/-2.9, percentage of valve size, P = .023) were associated with a greater sinotubular junction, although the incidence and mean grade of stentless valve regurgitation did not change significantly during the follow-up period. Up to medium-term follow-up evaluation, the incidence of moderate stentless aortic regurgitation is less than 5%. The nature of valve disease and age-related increase in sinotubular junction may have reduced the cusp coaptation area of the stentless valve and may predict the presence of a trivial or mild regurgitation. Understanding the interrelations between the stentless valve and remodeling of the aging aorta has important implications for both surgical technique and long-term follow-up outcome.
The hemodynamic superiority of first-generation stentless xenografts over their stented equivalents is now clearly defined. Issues of durability remain. In light of considerable early experience, we sought to provide an "ideal" stentless valve design with the potential for improved durability by eliminating glutaraldehyde. The Carbomedics Oxford Photofix stentless valve (PSV) is a composite xenograft root constructed from three selected porcine noncoronary cusps fixed by the photofix process. The valve inflow has a low pericardial cuff. Consequently there are no coronaries, cloth, or muscle bar in the structure. The valve was tested in the descending aorta and subcoronary positions of juvenile sheep to compare the influence on calcification of photofixation and the alpha-amino-oleic-acid-treated Freestyle valve. There was a substantial difference between the valves, both in radiographic imaging of calcification and the elemental analysis of calcium and phosphorus. In the valve cusp, calcium content of PSV was 3.98+/-5.77 mg/g versus 14.3+/-19.29 mg/g for the Freestyle valve. Equivalent calcium values for the aortic wall were 1.99+/-3.39 mg/g versus 130.79+/-56.29 mg/g. We consider the composite root configuration without cloth, coronaries, or muscle bar to be a promising valve design. The photofix process minimizes xenograft tissue calcification and appears superior to existing methods.
BACKGROUND: Mechanical bridge to left ventricular recovery is an emerging strategy for the treatment of heart failure. We sought to validate the use of a new intracardiac axial flow impeller pump for this purpose. METHODS AND RESULTS: The Jarvik 2000 Heart was implanted into 30 sheep to ascertain mechanical reliability, biocompatibility, and hemodynamic function. We attempted but failed to anticoagulate with warfarin. Elective explants with survival were performed in 3 animals to simulate bridge to recovery. Extensive autopsy studies were performed in all other animals. At speeds between 8000 and 12 000 rpm the device pumped up to 8 L/min, captured all mitral flow, and augmented cardiac output with elevation of mean arterial pressure. The pump was silent and hemolysis negligible. Nonpulsatile flow did not adversely affect neurological or renal function. Device removal proved straightforward and safe. A fractured inflow bearing occurred in 1 early model. There were no other pump failures, but power interruption occurred when the sheep chewed the cables or head-butted the percutaneous pedestal. At autopsy, there was no thromboembolism or primary thrombus formation in any device. Pump occlusion occurred in 2 sheep with bacterial endocarditis. One electively explanted pump, previously switched off for 5 months, had no thrombus in the device or vascular graft. CONCLUSIONS: The Jarvik 2000 Heart is a major advance in blood-pump technology and increases the scope of mechanical circulatory support. Reliability and ease of removal favor its use for bridge to myocyte recovery, as well as for bridge to transplantation or long-term support.
BACKGROUND: Stentless aortic xenografts are an important addition to the range of prosthetic valves. So far their use has been restricted to a limited number of study centers. This report summarizes the principal findings from the Second International Symposium on Stentless Bioprostheses. Attention is focused on the Toronto SPV and Freestyle valves recently approved by the United States Food and Drug Administration. METHODS: Stentless xenografts are used predominantly in elderly patients with aortic stenosis. Implant techniques are more complex than for stented valves, as reflected by longer ischemic and cardiopulmonary bypass times. The valves have been subjected to detailed serial echocardiographic assessment and clinical follow-up. RESULTS: The hemodynamic characteristics resemble those of the aortic homograft. There is a progressive increase in effective orifice area and decrease in transvalvular pressure gradients with time. Left ventricular mass index and wall thickness normalize between 6 and 12 months postoperatively. Left ventricular remodeling is accompanied by improved symptomatic status and a low incidence of valve-related complications. Limited comparative studies suggest important benefits over stented xenografts. Improved hemodynamics may translate into better bioprosthetic durability. CONCLUSIONS: Reproducible and reliable implant methods should be taught carefully, but the hemodynamic advantages are substantial. Stentless xenografts are ideal for the elderly patient with aortic stenosis.
BACKGROUND: Driveline infection limits the event-free survival of patients with a left ventricular assist device. With the evolving prospect of improved left ventricular assist devices in the bridge-to-transplantation or recovery setting, we sought to reduce the risk of driveline complications. METHODS: As part of the Oxford Jarvik 2000 research program, we developed a carbon and then titanium pedestal to transmit the electric wires through the skin. In a sheep model, the pedestal was brought out through the skin of the shoulder (n = 10) or the scalp (n = 9) with underlying fixation to the skull. Exit wounds were carefully inspected for healing and infection. Power cable durability tests were performed in 6 additional animals without an implanted pump. RESULTS: The cumulative observation period was 1,491 days (mean time, 78 days; range, 14 days to 198 days). There was no difference in observation period between the two groups. Infection (n = 2) and impaired healing (n = 5) occurred in the mobile tissues at the shoulder. Skull-mounted pedestals were free from infection or healing problems. The electric cables were not interrupted by repeated neck flexion (cumulative observation period, 588 days). The carbon pedestal was replaced by a titanium pedestal when the head butting of the sheep fractured the carbon. CONCLUSIONS: The combination of rigid fixation and highly vascular scalp skin reduces the risk of percutaneous driveline infection and may solve an important outstanding problem in use of left ventricular assist devices.