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Biomedical subjects

R W Stewart

Publications and source records attributed to R W Stewart.

At least 73 records · Page 4Linked to original sources
PubMed1988

Aortic valve replacement combined with myocardial revascularization. Late results and determinants of risk for 471 in-hospital survivors.

Among 500 patients consecutively undergoing primary aortic valve replacement combined with coronary bypass grafting from 1967 to 1981, there were 29 (5.8%) perioperative deaths. Follow-up of the late survivors ranged from 43 to 181 months (mean 85 months); actuarial survival rates were 88%, 77%, and 52% and event-free survival rates were 80%, 65%, and 32% at 2, 5, and 10 postoperative years. Cox proportional hazard analyses were used to identify determinants of late risk. Patient-related variables associated with decreased late survival rates included advanced age, cardiothoracic ratio 50% or greater, and preoperative New York Heart Association class III or IV symptoms. Moderate or severe impairment of left ventricular function as determined by angiography and advanced age were variables that decreased late event-free survival rates. Patients with bioprostheses had better survival rates (p less than 0.001) and event-free survival rates (p = 0.012) than did patients with mechanical valves. Analyses of subgroups according to the type of valve and postoperative anticoagulant management showed that both survival and event-free survival rates were decreased for patients with mechanical valves who were not taking warfarin and were enhanced for patients with bioprostheses who were not taking warfarin.

Aged↗
PubMed1988

Does bilateral internal mammary artery grafting increase surgical risk?

The risk of bilateral internal mammary artery grafting was studied in three groups of patients who were computer matched for recognized risk factors: year of operation, age, gender, extent of coronary artery disease, left ventricular function, completeness of myocardial revascularization, and history of congestive heart failure. The patient groups differed in the fact that they received veins only, one internal mammary artery graft, or two internal mammary artery grafts. The operative mortality rates for these three groups were 1.8%, 0.3%, and 0.9%, respectively (no significant difference). Analysis of perioperative morbidity demonstrated no significant differences except for a slight increase in transfusion requirements in the group receiving two internal mammary artery grafts (p = 0.04). None of the patients with only vein grafts had wound complications. One patient in the group with one internal mammary artery graft had a wound complication (0.03%). Eight patients receiving two internal mammary artery grafts had wound complications (2.4%) (p = 0.002). The prevalence of wound complications in patients with diabetes mellitus was 5.7% and in those without diabetes mellitus, 0.3% (p = 0.01). The prevalence of wound complications in patients less than 60 years of age was 0.2%, in patients in their 60s, 1.6%, and in patients older than 70, 3.1% (p = 0.01). Multivariate logistic regression analysis identified diabetes mellitus and age and not bilateral internal mammary artery grafting as risk factors for wound complications. We conclude that bilateral internal mammary artery grafting does not increase surgical mortality and increases surgical morbidity by a slight increase in the mean transfusion requirement.

Blood Transfusion↗
PubMed1987

Intermediate-term fate of cryopreserved allograft and xenograft valved conduits.

Actuarial freedom from reoperation for obstruction in 147 patients receiving cryopreserved or fresh allograft valved conduits between a ventricle and the pulmonary arteries was 94% at 3.5 years. The 2 patients undergoing reoperation were 6 and 36 months of age at the time of insertion of the allograft. Among 24 patients in whom cardiac catheterization was performed on indication late postoperatively, 5 had gradients of more than 40 mm Hg across the conduit. For comparison, among 78 patients receiving xenograft or irradiated allograft valved conduits, the percentages of freedom from conduit reoperation at 3.5, 5, 10, and 15 years were 99%, 95%, 59%, and 11%, respectively. The diameters of the allograft and xenograft valves inserted varied directly with the age and size of the patients, but in patients 3 to 5 years of age, allografts with a diameter of at least 21 mm could usually be used.

Aorta↗
PubMed1987

Fifteen hundred coronary reoperations. Results and determinants of early and late survival.

Fifteen hundred consecutive patients undergoing a first reoperation for coronary revascularization were reviewed to determine early and late results and predictors of survival. Patients were subdivided into cohorts on the basis of the year of reoperation: Group A (1967 to 1978, 436 patients); Group B (1979 to 1981, 439 patients); and Group C (1982 to 1984, 625 patients). Overall operative mortality was 3.4% (51 deaths): 4.6%, 2.3%, and 3.4% for Groups A, B, and C, respectively. Group C had significantly more women (p = 0.01) and patients with triple-vessel disease, left main coronary artery stenosis (greater than or equal to 50%), abnormal left ventricular function, age greater than or equal to 70 years, and graft failure as a surgical indication (all p less than 0.001). The mean interval between operations increased from 50 months for Group A to 84 months for Group C. At reoperation, Group C patients received more grafts, more internal mammary artery grafts, and had a higher prevalence of complete revascularization (all p less than 0.001). Univariate and multivariate analyses identified left main stenosis (p less than 0.0001), Class III or IV symptoms (p = 0.0002), advanced age (p = 0.0006), Group A (p = 0.02), and incomplete revascularization (p = 0.004) as predictors of increased in-hospital mortality. Follow-up of in-hospital survivors (mean interval 54 months, range 13 to 171 months) documented a 5 year survival rate of 90% and a 10 year survival rate of 75%. Multivariate testing identified advanced age (p less than 0.0001), hypertension (p less than 0.0001), and abnormal left ventricular function (p less than 0.0001) as predictors of decreased late survival.

Aged↗
PubMed1986

Influence of the internal-mammary-artery graft on 10-year survival and other cardiac events.

We compared patients who received an internal-mammary-artery graft to the anterior descending coronary artery alone or combined with one or more saphenous-vein grafts (n = 2306) with patients who had only saphenous-vein bypass grafts (n = 3625). The 10-year actuarial survival rate among the group receiving the internal-mammary-artery graft, as compared with the group who received the vein grafts (exclusive of hospital deaths), was 93.4 percent versus 88.0 percent (P = 0.05) for those with one-vessel disease; 90.0 percent versus 79.5 percent (P less than 0.0001) for those with two-vessel disease; and 82.6 percent versus 71.0 percent (P less than 0.0001) for those with three-vessel disease. After an adjustment for demographic and clinical differences by Cox multivariate analysis, we found that patients who had only vein grafts had a 1.61 times greater risk of death throughout the 10 years, as compared with those who received an internal-mammary-artery graft. In addition, patients who received only vein grafts had 1.41 times the risk of late myocardial infarction (P less than 0.0001), 1.25 times the risk of hospitalization for cardiac events (P less than 0.0001), 2.00 times the risk of cardiac reoperation (P less than 0.0001), and 1.27 times the risk of all late cardiac events (P less than 0.0001), as compared with patients who received internal-mammary-artery grafts. Internal-mammary-artery grafting for lesions of the anterior descending coronary artery is preferable whenever indicated and technically feasible.

Coronary Artery Bypass↗
PubMed1986

Reoperations for valve surgery: perioperative mortality and determinants of risk for 1,000 patients, 1958-1984.

One thousand consecutive cardiac reoperations for valve surgery in 897 patients were reviewed to determine in-hospital mortality and indicators of risk. Subgroups based on the number of previous cardiac procedures and the valve or valves replaced or repaired at reoperation (aortic valve, mitral valve, tricuspid valve, or multiple valves and mortality [deaths/number of procedures (% mortality)]) for those subgroups are as follows: (Table: see text) Predictors of increased risk for a first aortic valve reoperation were advanced age (p = .0002), endocarditis (p = .0018), female sex (p = .014), impaired left ventricular function (p = .039), and number of coronary vessels obstructed by 70% or more (p = .055). For a first mitral valve reoperation, the predictors were advanced age (p less than .0001), preoperative shock or cardiac arrest (p = .01), previous aortic or tricuspid valve operations (p = .02), type of mitral valve procedure (risk for repair of periprosthetic leak was greater than mitral valve replacement which was greater than mitral valve-conserving operation [p = .05]), and impaired left ventricular function (p = .059). For a first multiple valve reoperation, the predictors were diabetes (p = .04) and ascites (p = .02), whereas patients undergoing mitral valve replacement and tricuspid valve operations were at decreased risk (p = .01). Comparison of second reoperations with first reoperations indicates risk increases for multiple operations (p = .01) but not for aortic or mitral valve procedures. Rereplacement of a prosthesis (p = .007), coronary bypass grafting at reoperation (p = .006), and advanced age (p = .06) increased the risk for second reoperations. Age is the most consistent predictor of risk for patients undergoing valve reoperations.

Aortic Valve↗
PubMed1986

Free (aorta-coronary) internal mammary artery graft. Late results.

Free internal mammary artery grafts were placed in 156 patients (1971 to 1985). Preoperative clinical and angiographic variables were similar to those of other series of isolated coronary bypass grafts. Of 244 total internal mammary artery grafts, 166 were in the aorta-coronary position and were performed mainly because of unsuitable saphenous veins or to gain additional graft length. One patient (0.6%) died during hospitalization. Perioperative complications included respiratory dysfunction in 16 (10.3%), reoperation for bleeding in 13 (8.0%), stroke in four (2.6%), myocardial infarction in three (1.9%), and wound complications in two (1.3%). Morbidity occurred significantly more often in the 1971 to 1975 period. Subsequently, eight (7%) had reoperation (6 to 158 months; mean 99 months). After a 98 month mean follow-up, the 10 year actuarial survival rate (including all causes of death) was 73.3%. Of 40 free grafts restudied within 18 months of operation, 31 (77%) were patent. The higher rate of early closure is attributed to technical problems early in our experience, especially construction of the aortic anastomosis. However, 32 of 35 (91%) free grafts studied after more than 18 months (mean 94 months) were open. Fifty of 58 (86%) free internal mammary artery grafts placed to the anterior descending coronary artery, seven of nine (78%) to the circumflex, and six of eight (75.0%) to the right coronary artery were patent. Sequential catheterization showed that of 24 free grafts open at 9 months, 24 remained patent at 80 months; when six of these were restudied at 93 months (third catheterization) and two (fourth catheterization) at 125 months, all were patent. These late studies of free internal mammary artery grafts showed no evidence of graft atherosclerosis. Free internal mammary artery grafts, like in situ internal mammary artery grafts, appear to have relative immunity from atherosclerosis. These findings expand the versatility of internal mammary artery grafting and justify wider use of free internal mammary artery grafts.

Adult↗
PubMed1986

Early results of emergency surgery after coronary angioplasty.

During the period of our study 81 patients undergoing elective coronary artery angioplasty at our institution required emergency revascularization surgery within the ensuing 24 hr. The mean age of the 59 men and 22 women was 57 years (32 to 74 years). The principal indications for the emergency surgery were acute occlusion (n = 36), dissection (n = 28), unstable angina (n = 10), ventricular arrhythmias (n = 4), and unsuccessful balloon dilatation (n = 3). There were two early deaths and in 35 patients the presence of three criteria for myocardial infarction was noted postoperatively. Including these patients, 52 patients surviving their hospital course suffered 75 major complications. Emergency surgery after failed percutaneous transluminal coronary angioplasty can be performed with low mortality, but it carries a high incidence of major postoperative complications.

Adult↗
PubMed1986

Results of mitral valve reconstruction.

To evaluate the early results of mitral valve reconstruction for mitral insufficiency, 117 consecutive cases were analyzed. Sixty-four (57.7%) of the patients were men, and the mean age was 60 +/- 13 years (range 18 to 85). Eighty-nine (76%) of the patients were in NYHA functional class III or IV preoperatively. The cause of the mitral disease was degenerative in 94 (80%) and rheumatic in 13 (11%) patients. Isolated mitral valve repair was performed in 56 patients (47.9%); the remainder underwent associated procedures that included myocardial revascularization in 38 (32.5%). Ninety-nine (85%) underwent a ring annuloplasty but in only seven (6%) was this the only repair technique. Resection of the posterior leaflet was performed in 41 (35%). There were five operative deaths (4.3%); one (1.8%) occurred after isolated repair and four (6.5%) after repair with associated procedures. All deaths occurred in patients greater than 65 years of age who were in NYHA functional class III or IV. Mean follow-up was 13.5 months (range 1 to 62). Two year actuarial survival was 90.6%. Three patients required reoperation (incidence of 2.5% per patient-year). Two patients sustained embolic events (incidence of 1.6% per patient-year). There were no anticoagulant-related complications. After surgery, 100 survivors (96.2%) were in NYHA functional class I or II.

Adolescent↗
PubMed1986

Predictors of reoperation after myocardial revascularization.

The first 1,000 patients undergoing primary isolated myocardial revascularization each year from 1971 to 1978 were analyzed to define the incidence of reoperation and to elucidate the determinants of reoperation and reoperation-free survival. Six hundred sixty-six patients (9.7%) underwent reoperation in a mean of 6.9 +/- 3.2 years. Cumulative percent reoperation was 2.7% at 5 years, 11.4% at 10 years, and 17.3% at 12 years. The annual incidence of reoperation was 1.1% at 5 years and increased to 3.9% at 12 years. Twenty-five patient descriptors were analyzed for predictors of reoperation. Young age was found to be the most important predictor of potential for reoperation. Other risk factors in descending order of significance were absence of an internal mammary artery graft, incomplete revascularization, New York Heart Association Functional Class III/IV, and single or double vessel disease. Absence of an internal mammary artery graft was an important predictor for all age groups. In the multivariate analyses for risk factors for reoperation-free survival, absence of an internal mammary artery graft was the most important predictor. Other factors of major significance were smoking, incomplete revascularization, and moderate/severe left ventricular impairment. Internal mammary artery grafting neutralizes hypertension, serum cholesterol level higher than 300 mg/dl, and smoking as risk factors for reoperation-free survival.

Adult↗
PubMed1985

Determinants of 10-year survival after primary myocardial revascularization.

The first 1000 patients undergoing primary isolated myocardial revascularization each year from 1971 to 1978 were analyzed to elucidate the determinants of long-term survival. Five-year survival was 93.2%, and 10-year survival was 79.3%. Five-year survivals were 96.1%, 94.2%, 92.1%, and 90.8%, respectively, for single, double, triple, and left main disease. Ten-year survivals for the same subsets were 88.6%, 83.0%, 74.9%, and 70.9%. Five-year survivals were 95.3%, 92.4%, 88.0%, and 81.3% for patients with normal, mild, moderate, and severe impairment of the left ventricle. Ten-year survivals for the same subsets were 84.1%, 76.5%, 65.8% and 53.6%. Patients receiving internal mammary artery grafts had 95.6% and 85.8% 5- and 10-year survivals that were superior to 92.0% and 76.2% in patients with only vein grafts. Patients completely revascularized had 95.0% and 82.5% 5- and 10-year survivals, while incompletely revascularized patients had lower (90.5% and 75.2%) 5- and 10-year survivals. Advancing age was the most important factor influencing late survival. Other risk factors in descending order of significance were impaired left ventricular function, no mammary artery graft, smoking, abnormal EKG, three vessel or left main disease, left ventricular end diastolic pressure (LVEDP) greater than 24, hypertension, 1971 to 1974 surgical era, cholesterol greater than 300, incomplete revascularization, and two vessel disease.

Adult↗
PubMed1985

Mitral valve replacement combined with myocardial revascularization: early and late results for 300 patients, 1970 to 1983.

Of 300 consecutive patients undergoing primary operation for mitral valve replacement combined with coronary bypass grafting, 22 (7.3%) died in-hospital. Multivariate testing of preoperative and operative descriptors identified radiographic cardiac enlargement, preoperative paced rhythm or atrial fibrillation, 70% or more left main coronary obstruction, and serum bilirubin of more than 2 mg% as factors associated with an increase in in-hospital mortality. Follow-up of the 278 hospital survivors (mean interval 48 months, range 2 to 165 months) documented survival of 85%, 66%, and 31% and an event-free survival of 65%, 46%, and 21% at 2, 5, and 10 postoperative years, respectively. Cox proportional-hazard regression models of late risk implicated in-hospital ventricular arrhythmias, left ventricular dysfunction, and rheumatic or ischemic causes of mitral valve disease in decreasing long-term survival. In addition, patients with bioprostheses without warfarin anticoagulation had better survival and event-free survival than those with bioprostheses taking warfarin and those with mechanical prostheses with or without warfarin.

Aged↗
PubMed1985

Does mammary artery grafting increase surgical risk?

From 1980 through 1982, 7105 patients underwent primary isolated myocardial revascularization. Of these, 49.2% received only vein grafts and 50.2% received at least one internal mammary artery graft. The incidence of mammary artery grafting increased from 33.5% in 1980 to 67.1% in 1982. The operative mortality rate was 1.4% in the vein group and 0.2% in the mammary artery group (p less than .0001). A multivariate analysis identified six incremental risk factors for operative mortality. After adjusting for these risk factors, the use of vein grafts only was found to be an incremental risk factor (p less than .0001). In a subset of patients without major risk factors, there was no difference in the incidence of perioperative infarction, respiratory insufficiency, wound complication, stroke, use of intra-aortic balloon, reoperation for bleeding, or blood requirements. We conclude that internal mammary artery grafting is safe and is not associated with increased surgical morbidity or mortality.

Adult↗
PubMed1985

Myocardial revascularization: evolution of a surgical procedure.

Since its inception, myocardial revascularization has steadily evolved. The patient population is older with more extensive cardiac disease. Surgical mortality is currently 1% with a less than 1% perioperative myocardial infarction rate. The number of grafts done per patient has increased to more than three with 80% of the patients being completely revascularized. Ninety percent of the patients receive at least one internal mammary artery graft. With more complete revascularization and greater use of the internal mammary artery, the prospects for long-term survival and palliation have improved.

Adult↗
PubMed1985

Successful acute heart-lung transplantation after six hours preservation.

The lack of an appropriate and effective technique for prolonged heart-lung preservation has been one of the factors limiting the use of this therapeutic modality. Presently, the donor is transported to the transplant center, which is often an unacceptable burden to the donor's family. A reliable preservation technique that would allow long-distance procurement would markedly increase the use of heart-lung transplantation. Using a dog, a successful heart-lung transplantation was achieved following six hours of preservation of the graft. The experiment was terminated when the animal was able to maintain normal blood gases following extubation.

Animals↗
PubMed1985

In vivo hemodynamic comparison of porcine and pericardial valves.

The bovine pericardial valve and the SupraAnnular valve have been developed to improve the hemodynamic function of tissue valves. Hemodynamic performances of the standard Carpentier-Edwards porcine valve, the Carpentier-Edwards SupraAnnular valve, and the Carpentier-Edwards bovine pericardial valve were compared in the aortic position. One hundred patients undergoing aortic valve replacement were studied intraoperatively. Mean gradient across the valve decreased for standard and pericardial valves as valve size increased. At the same flow rate, the 23 mm pericardial valve had larger valve orifice areas, higher performance indices, and lower gradients than the 23 mm SupraAnnular valve. The SupraAnnular valve is hemodynamically superior to the standard Carpentier-Edwards porcine bioprosthesis. The Carpentier-Edwards pericardial valve, however, is less obstructive in the aortic position than either of the porcine valves.

Aortic Valve↗
PubMed1984

A simple method for extended heart-lung preservation by autoperfusion.

A modification of Robicsek's autoperfusing heart-lung preparation preserved normal structure in the canine lung for 8 hrs and in the heart for 12 hrs. Applicable to both heart and heart-lung transplantation, the system would permit a safe extension of preservation time limits.

Animals↗