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Biomedical subjects

T E David

Publications and source records attributed to T E David.

158 records · Page 9Linked to original sources
PubMed1978

Extended profundoplasty for limb salvage.

Extended profundoplasty was performed in 50 limbs of 39 patients for relief of rest pain or gangrene. This operation was effective in 95% of the limbs operated on because of rest pain, and in 54.5% of the limbs operated on because of gangrene. In 32 limbs the popliteal artery was patent. Profundoplasty was successful in relieving ischemic symptoms in all but two limbs. Postoperative ankle pressures were increased consistently in the improved limbs. In 18 limbs the popliteal artery was occluded. Profundoplasty abolished the ischemic symptoms in 13 limbs. Ankle pressures did not increase consistently in limbs that were clinically improved in this group. The authors believe that restoring blood flow and pressure to the profunda femoris artery and its branches, by means of open endarterectomy and patch graft, can salvage limbs which otherwise would be fated for amputation. As such, it represents a reasonable alternative to bypass grafting, and in some cases it is the procedure of choice for the patient with threatened tissue loss.

Adult↗
PubMed1977

Subannular mitral prosthesis in aortic position.

Björk-Shiley subannular mitral prostheses have been used in the aortic position in 36 patients with calcific aortic annulus. We believe that the flange in the sewing ring of these prostheses offers added protection against perivalvular leakage; over an 18-month period there have been no instances of periprosthetic leakage in these patients.

Aortic Valve Stenosis↗
PubMedDate not supplied

Aortic valve replacement with stentless porcine bioprostheses.

The implantation of stentless porcine valves (SPVs) is technically more demanding than implantation of stented bioprosthetic valves. Implantation of the Toronto SPV bioprosthesis requires an,understanding of the relationships between the leaflets and the aortic annulus and sinotubular junction. In addition to proper alignment of the three commissures within the aortic root, the diameter of sinotubular junction should not exceed the external diameter of the porcine aortic valve after completion of the operation. The Medtronic Freestyle porcine aortic root bioprosthesis can be used for subcoronary implantation as well as for aortic root replacement. Degenerative calcification of a tricuspid aortic valve is the most common cause of aortic valve disease in older patients. Implantation of stentless valves in the subcoronary position is usually feasible because the geometry of the aortic root is well maintained in these patients. The bicuspid aortic valve is the second most common cause of aortic valve disease in older patients and the most common in younger patients. These patients frequently have dilated aortic root, and the Medtronic Freestyle bioprosthesis is ideal for implantation using the root inclusion technique. Stentless porcine bioprostheses are minimally obstructive and associated with low mean systolic gradients. In addition, they have better hemodynamic performance during exercise than stented bioprostheses. For these reasons, patient-prosthesis mismatch has not been described with stentless valves. Left ventricular function after aortic valve replacement appears to be better with stentless than with stented bioprostheses. Comparative, nonrandomized studies of aortic valve replacement with stented and stentless valves suggest that the risk of cardiac death is reduced with stentless valves and the rates of valve-related complications also appear to be lower. What remains unknown is whether stentless valves are more durable than stented ones.

Aortic Valve↗
PubMedDate not supplied

Reoperations on the aortic valve combined with replacement of the ascending aorta.

OBJECTIVE: To review the experience with reoperations on the aortic valve combined with replacement of the ascending aorta. PATIENTS AND METHODS: From 1991 to 2000, 237 patients underwent reoperations on the aortic valve combined with replacement of the ascending aorta. The study consisted of 188 men and 49 women, with a mean age of 51 years. The operation was urgent or emergent in 44% of cases. Many patients (42%) were in New York Heart Association Class IV, and 24 had active infective endocarditis. The ascending aorta was replaced previously in 46 patients, while the remaining patients had aneurismal dilation. An aortic valve sparing operation was performed in 14 patients and aortic valve replacement in 223. The ascending aorta was replaced in all patients as follows: as a composite graft in 166 and supracoronary in 71. Mechanical valves were used in 145 (61%) patients. RESULTS: The operative mortality was 9%. Postoperative complications were common and 30% of patients suffered an adverse event (death or complication). No independent predictor of operative mortality could be identified but urgent/emergent surgery, advanced functional class, infective endocarditis, coronary artery disease, and replacement of the transverse aortic arch were associated with higher operative mortality by chi-square analysis. The survival at 5 years was 74%+/-4% for patients who had composite replacement of the aortic valve and ascending aorta. CONCLUSIONS: Reoperations on the aortic valve combined with replacement of the ascending aorta can be performed with acceptable operative risk and good mid-term survival.

Adult↗
PubMedDate not supplied

Recycled heart valves from transplant patients.

Forty heart transplantations were performed at the Toronto Western Hospital, University of Toronto, from October 1987 to December 1989. Each heart extracted from a recipient was examined with the view of using the aortic valve as a homograft for another patient requiring aortic valve replacement. Of the 40 explanted hearts, 26 had normal aortic valves that were potentially suitable for homografting, and 14 had aortic valves judged as unsuitable. Of the potentially suitable valves, four were preserved for ex vivo arrhythmia studies requiring aortic root perfusion and four were damaged during harvesting. The remaining 18 usable valves were sized at the time of explantation and stored in an antibiotic solution at 4 degrees C. Thirteen valves were transplanted within 10 days of harvesting, and five were discarded because no suitable recipients were available within this period. There were no operative deaths or valve-related complications in the 13 homograft valve recipients. Mean follow-up was 13 months (range, 3 to 27 months). One patient required replacement of the homograft with a mechanical prosthesis because of insufficiency and stenosis. All patients are alive, are New York Heart Association functional class status I, and have insignificant valve gradients based on Doppler echocardiography. Although hearts removed from transplant recipients are severely diseased, the aortic valves are frequently normal and should be considered for use as homografts for other patients requiring aortic valve replacement.

Adult↗
PubMedDate not supplied

Relationship between preoperative pulmonary status and outcome after heart transplantation.

To determine whether routine preoperative pulmonary function tests provide useful prognostic information in orthotopic heart transplant candidates, we evaluated the pulmonary status of 33 patients who subsequently underwent transplantation. There was one perioperative death and five other fatalities within 9 months after operation. Mean age of the six patients who died (mean +/- SD 51.8 +/- 5.0 years) was significantly different (p less than 0.05) from that of the survivors (44.6 +/- 11.1 years). Mean preoperative pulmonary vascular resistance was significantly different (p less than 0.05) between those patients who had a fatal outcome (mean, 4.4 +/- 2.0 mm Hg/L/min) and those who survived (2.7 +/- 1.0 mm Hg/L/min). By contrast, we found that measures of forced vital capacity, forced expired volume in 1 second, diffusion capacity for carbon monoxide, and arterial blood gases bore no apparent relationship to outcome. We conclude that standard noninvasive measures of pulmonary function may be useful in preoperative preparation of heart transplant candidates, but they do not appear to be helpful in predicting eventual outcome.

Adult↗
PubMedDate not supplied

Aortic valve replacement with a stentless porcine bioprosthesis: multicentre trial. Canadian Investigators of the Toronto SPV Valve Trial.

OBJECTIVE: To evaluate the clinical and hemodynamic performance of a new bioprosthesis for replacement of the aortic valve in humans. STUDY DESIGN: In a multicentre clinical trial between July 1991 and January 1994, 118 patients underwent aortic valve replacement with the Toronto SPV valve. RESULTS: Valvular pathology was aortic stenosis in 58%, insufficiency in 12% and mixed valvular disease in 30%; congenital bicuspid aortic valve was seen in 42% while heavy calcification was present in 86%. In approximately a third of the patients, concomitant coronary artery bypass surgery was performed. The mean period of aortic occlusion was 89 mins (range 48 to 180). Valve sizes implanted were: 22 mm (1%), 23 mm (7.6%), 25 mm (22.9%), 27 mm (37.3%) or 29 mm (31.4%). There were three deaths in the series: two from subacute bacterial endocarditis and one suicide. Early complications were cardiac arrest (0.8%), thromboembolism (2.5%) and arrhythmia (12.7%), while late complications were cardiac arrest (0.8%), arrhythmia (4.7%), angina (0.8%), thromboembolism (4.4%), endocarditis (1.7%) and other sepsis (0.8%). There were no valve related failures in 119 valve-years (mean follow-up 1.01 valve-year per patient). Follow-up echocardiography demonstrated an average decrease in mean systolic gradient of 36% from early to late postoperative period (P < 0.001) and an average increase in effective orifice area of 35% (P < 0.001) in the same period. No regurgitation was noted in 91% of patients at early, and 89% of patients at late, follow-up. CONCLUSIONS: The Toronto SPV valve offers excellent hemodynamics, is relatively easy to insert and has few valve related complications. The observed changes in transvalvular area over time are consistent with a hypothesis that the ventricle undergoes remodelling following aortic valve replacement with this bioprosthesis. Longer follow-up is required to determine durability.

Animals↗
PubMedDate not supplied

Porcine aortic leaflet arrangement may contribute to clinical xenograft failure.

Clinical experience with the first generation porcine xenograft shows significant deterioration and mechanical failure after 7-8 years post-implantation. Although many mechanisms of valve failure have been identified, the inherent differences between porcine and human aortic valves have not been emphasized. To determine if these differences are significant, the authors studied the anatomy of the aortic valve in 10 post-mortem porcine hearts. The authors found that the non-coronary leaflet was the smallest and the right leaflet was the largest based on the dimensions of area, perimeter, weight, and attached edge length (p < 0.05). These results differ from reported analyses of human aortic valves, in which the smallest cusp is generally the right the largest is the non-coronary. The authors believe that these differences between the human and porcine aortic valves may result in atypical mechanical stresses and the disruption of blood flow patterns in the sinuses of Valsalva, and may decrease the long-term stability of the porcine bioprostheses. In other words, the failure found with porcine bioprostheses after 8 years of implantation might be expected from the inherent structure (and associated fluid dynamics) of the porcine aortic valve positioned in the human aortic root.

Animals↗
PubMedDate not supplied

Current practice in Marfan's aortic root surgery: reconstruction with aortic valve preservation or replacement? What to do with the mitral valve?

BACKGROUND: Until recently the surgical treatment of aneurysms of the aortic root in patients with the Marfan syndrome consisted of composite replacement of the aortic valve and ascending aorta. At the present, almost one-half of these patients can have reconstruction of the aortic root with preservation of the aortic valve. The mitral valve can also be frequently preserved. PATIENTS AND METHODS: From 1988 to 1996, 46 patients with the Marfan syndrome and aortic root aneurysm underwent cardiac surgery; the aortic valve was preserved in 23 and replaced in 26. The mitral valve was repaired in 3 patients who had aortic valve-sparing operations, and it was repaired in 3 and replaced in 3 who had aortic valve replacement. Both groups of patients had similar clinical profile. RESULTS: There were 2 operative deaths among patients who had aortic valve replacement but neither one was valve-related. One patient who had aortic valve-sparing operation needed aortic valve replacement 2 years postoperatively. There were no other valve-related complications in this group. The actuarial survival was 100% at 5 years for this group. Four patients needed reoperations for valve-related complications in the group who had composite replacement of the aortic valve and ascending aorta. The actuarial survival was 88% +/- 4% at 5 years in this group. CONCLUSIONS: Although the number of patients in each group is small and the follow-up relatively short, aortic valve-sparing operations have given gratifying results and may prove superior to valve replacement in patients with the Marfan syndrome.

Adolescent↗
PubMedDate not supplied

Surgical management of aortic root abscess.

BACKGROUND: The mortality and morbidity associated with surgery for aortic root abscess is reportedly high. This is a review of our experience with radical resection of the abscess and reconstruction of the left ventricular outflow tract with pericardium. METHODS: Sixty-three consecutive patients with aortic root abscess were operated on since 1980. Their mean age was 47 years, range 16 to 75; 53 patients were men. Thirty-one patients had native and 32 had prosthetic valve endocarditis; of these 32, 13 had previous composite replacement of the aortic valve and ascending aorta. The most common offending microorganisms were staphylococci, which were cultured in 31 patients. The abscess was confined to the aortic annulus in 22 patients and had extended into surrounding structures in 41. The abscess involved the mitral valve in 13, the tricuspid valve in 2, and the pulmonary valve in 1. Radical resection of the abscess and reconstruction of the left ventricular outflow tract and other valve annull was accomplished with autologous or glutaraldehyde-fixed bovine pericardium. Aortic valve homograft was used in only three patients; prosthetic heart valves in 60. RESULTS: There were eight deaths; 26 patients experienced one or more non-fatal perioperative complication. Patients were followed up for a mean of 58 +/- 39 months. There were ten late deaths; the actuarial survival at 10 years was 55% +/- 10%. Nine patients developed late recurrent endocarditis 10 to 108 months postoperatively. The freedom from recurrent endocarditis at 10 years was 75% +/- 8%. CONCLUSIONS: Radical resection of aortic root abscess and reconstruction of the left ventricular outflow tract with pericardium is an effective method to eradicate the infection. These patients appear to have a relatively high risk of recurrent endocarditis.

Abscess↗