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Biomedical subjects

G S Couper

Publications and source records attributed to G S Couper.

70 records · Page 4Linked to original sources
PubMed1990

Decreased operative risk of surgical treatment of mitral regurgitation with or without coronary artery disease.

The consecutive 2 year experience with patients undergoing first-time surgery for mitral regurgitation with and without coronary artery disease was reviewed. From January 1988 to January 1990, 127 patients with pure mitral regurgitation undergoing first-time operation were surgically treated. No other valve lesion, no reoperation and no congenital defects were included. The mean patient age was 62 years with 26% of the patients greater than 70 years. Twenty-six percent of the entire group was in functional class IV. Seventy-five patients received mitral valve repair and 52 underwent mitral valve replacement with a St. Jude or Hancock valve. In patients undergoing mitral valve repair, there was a higher incidence of those greater than 70 years old and of coronary artery disease and in patients undergoing mitral valve replacement there was a higher incidence of functional class IV. The operative mortality rate was 2.3% (3 of 127 patients). No patient failed to be discontinued from cardiopulmonary bypass and all three deaths occurred after mitral valve replacement, with one from complications of chronic renal failure and dialysis. There was no significant difference in patients who either did or did not have a concomitant coronary artery bypass graft and there was no difference related to age or functional class. Postoperative complications occurred in five patients in the valve repair group, including recurrent mitral regurgitation in two necessitating reoperation, and in three patients in the valve replacement group. With newer operative and postoperative management techniques, especially preservation of the papillary muscle annular continuity, the risk of mitral valve surgery, particularly of valve repair, is considerably lower than in previous years.

Coronary Disease↗
PubMed1990

Relative risks of left ventricular aneurysmectomy in patients with akinetic scars versus true dyskinetic aneurysms.

From 1971 to 1988, 303 patients underwent left ventricular aneurysm resection. We analyzed preoperative and procedure-related variables to ascertain risk factors for surgery. A distinction was made between akinetic and dyskinetic aneurysms to assess potential relation with postoperative outcome. Indications for surgery were arrhythmia in 20 patients, congestive heart failure in 81, angina in 133, congestive heart failure and angina in 42, and other combinations in the remaining 27 patients. The left ventricular aneurysm was dyskinetic in 180 patients and akinetic in 121. Risk factors and surgical procedures were similar in both groups. Left ventricular ejection fraction was less than or equal to 30% in 98 patients. Coronary bypass grafting was performed in 269 patients, with an average of 2.3 grafts per patient. Mitral valve replacement, the most common concomitant procedure, was performed in 16 patients. Intra-aortic balloon assist was required postoperatively in 47 patients. Overall operative mortality was 13% (38 patients) and was due to low cardiac output in 23 patients and arrhythmia in 12 patients. Univariate and multivariate analyses related early mortality to New York Heart Association functional classification of heart failure, the predominant indications of arrhythmia or congestive heart failure, left ventricular ejection fraction less than or equal to 30%, the need for intra-aortic balloon support, and the excision of an akinetic (18%) rather than dyskinetic (8%) left ventricular aneurysm. Over a follow-up period averaging nearly 5 years, the actuarial survival at 5 years was 63% in the dyskinetic group and 51% in the akinetic group.(ABSTRACT TRUNCATED AT 250 WORDS)

Coronary Artery Bypass↗
PubMed1990

Favorable results of coronary artery bypass grafting in patients older than 75 years.

There is controversy whether the short-term and long-term results of coronary artery bypass grafting in elderly patients justify performing the procedure. Between January 1977 and December 1986, 4580 patients underwent coronary artery bypass grafting, of whom 222 (4.9%) were 75 years old or older (mean 77 years). There were 143 men and 79 women and 139 (63%) were in New York Heart Association class IV. One hundred forty-six patients (66%) had had at least one preoperative myocardial infarction. Myocardial revascularization was performed under emergency conditions in 17 patients (18%). The mammary artery was used in 43%, 96% of the patients received two or more grafts. The mean number of bypass grafts was 3.1 per patient. The overall hospital mortality rate was 10.8% (24/222), 3.6% for elective procedures, 14.9% in urgent cases, and 35% in emergencies. In contrast, the overall early mortality rate was 3.1% in 4358 patients less than 75 years old. Complications occurred in 83 patients (37%). Of the patients discharged from the hospital, 198 were followed up for a mean of 48 months (1 to 130). Actuarial probability of survival was 75% at 48 months. Postoperatively 70% were in New York Heart Association class I or II and only 21% were rehospitalized for cardiac problems. During the follow-up period 77% of the patients were free from angina, and of those experiencing angina the mean time from operation to the first episode was 75 months. Although elderly patients have a somewhat increased operative mortality rate, particularly if operated on urgently or emergently, long-term survival and freedom from angina are excellent and justify continued performance of coronary bypass grafting in selected patients over 75 years of age.

Actuarial Analysis↗
PubMed1989

Fifteen-year experience with 1678 Hancock porcine bioprosthetic heart valve replacements.

The Hancock porcine valve was the first commercially available biologic heart valve and has been in continuous use at the Brigham and Women's Hospital since January 1972. Through December 1987 we implanted 1678 valves in 1533 patients (885 male; 648 female; 17 to 95 years of age, with a mean of 60 years). There were 825 aortic valve replacements (AVR), 562 isolated mitral valve replacements (MVR), and 146 aortic mitral replacements (DVR). Ninety-four per cent of the patients were functional class III or IV. Associated coronary bypass was done in 25% of patients. Four per cent of patients were lost to follow up during a 1- to 16-year period with a mean of 6 years. Morbidity and mortality rates on a actuarial basis were calculated 10 and 15 years after operation for AVR, MVR, and DVR. The data indicates that the probability of reoperation for structural valve failure is quite reasonable as of 10 years, but from 10 to 15 years the numbers sharply fall off so that the probable effective life of the valve is 10 years. However in the elderly age group (equal to or greater than 70 years of age) the incidence of structural valve degeneration is markedly diminished, making this an ideal valve substitute for the elderly. It is also an ideal valve substitute in any patient who has a contraindication to long-term anticoagulation because of current medical or surgical problems.

Adolescent↗
PubMed1989

Mitral valve repair for myxomatous degeneration and prolapse of the mitral valve.

From 1984 to 1988, 129 mitral valve reconstructions were done for primary pure mitral regurgitation. Sixty-two (48%) were done for myxomatous degeneration and prolapse of the mitral valve. Anterior leaflet resection was performed in seven patients, posterior leaflet resection in 46, anteroposterior resection in four; five patients received only a ring annuloplasty. Eight patients had coronary bypass grafts. Twenty-four patients received a Carpentier-Edwards annuloplasty ring, 24 a Duran ring, and 14 patients had no ring. Follow-up was 1 to 50 months (mean, 13 months). No patient was lost to follow-up. There was one operative death from gastrointestinal bleeding and two late deaths (one from suicide and one from a myocardial infarction), and the probability of survival at 48 months was 84% +/- 15%. There were no thromboembolic episodes or episodes of endocarditis. However, there were five reoperations (9%) with freedom from reoperation at 48 months of 85% +/- 5%. There was one major anticoagulant hemorrhage. Freedom from all morbidity at 48 months was 81% +/- 8%. Postoperative echocardiographic data in the three different groups of patients undergoing repair on the basis of annuloplasty treatment showed that the peak gradient was less and the valve area was slightly greater with no annuloplasty ring.

Adult↗
PubMed1984

Role of acidosis in early contractile dysfunction during ischemia: evidence from pHo measurements.

To investigate the contribution of acidosis to contractile dysfunction during early myocardial ischemia, miniature intramyocardial pH electrodes (0.2 mm tip diam) were used to correlate changes in extracellular pH (pHo) with tension in the isolated arterially perfused rabbit interventricular septum. A number of findings argue against acidosis as the major cause of contractile failure during early ischemia. During hypoxia without glucose present, the rate and pattern of tension decline was very similar to total ischemia, suggesting that a common mechanism is involved. Throughout the initial period in which tension declined by 50%, however, pHo increased in the six of eight preparations during hypoxia without glucose. During hypoxia with glucose present, tension fell less rapidly than during hypoxia without glucose despite a significantly greater fall in pHo in the former case. The maximal rate of relaxation (-dT/dt) was markedly more sensitive to ischemia, hypoxia, or exposure to inhibitors of aerobic metabolism (2,4-dinitrophenol and Na azide) than the maximal rate of force development (+dT/dt). In contrast, +dT/dt and -dT/dt decreased almost symmetrically during exposure to respiratory acidosis. During ischemia, the change in pHo associated with 50% reduction in tension was 0.11 +/- 0.04 units. During respiratory acidosis, this value was 0.45 +/- 0.02 units. From these observations we concluded that acidosis is unlikely to be a major factor in the early decline of tension during ischemia.

Acidosis↗
PubMed1984

Extracellular pH and tension during ischemia in the isolated rabbit ventricle.

To investigate the factors determining the rate of H+ accumulation during early ischemia, miniature intramyocardial pH electrodes (tip diam 0.2-0.5 mm) were used to record extracellular pH (pHo) in the isolated arterially perfused rabbit interventricular septum. Changes in pHo and the rate of fall of tension during global ischemia were compared under control conditions (37 degrees C, heart rate 75 beats/min) and after exposure to the following interventions: reduced heart rate (36 beats/min), hypothermia (27 degrees C), verapamil (0.5 microM), reduced extracellular Ca2+ concentration [( Ca2+]o 0.5 mM), norepinephrine (0.5 microM) in normal and catecholamine-depleted preparations, norepinephrine and reduced [Ca2+]o, and theophylline (4 mM). Under control conditions pHo declined by 0.61-0.73 pH units after 10 min of ischemia. The negative inotropic interventions and reduced temperature significantly decreased [H+]o accumulation during ischemia. Positive inotropic interventions did not affect the rate of [H+]o accumulation during ischemia except in reserpinized preparations. All of the interventions except for reduced temperature significantly altered the relationship between tension and pHo during ischemia.

Acidosis, Respiratory↗
PubMed1976

Mescaline: its effects on learning rate and dopamine metabolism in goldfish (Carassius auratus).

The pharmacological action of mescaline on goldfish was studied with the Bitterman-Agranoff shock-avoidance test. In short term experiments with high mescaline doses an increase in learning rates was observed. Similar results were obtained with apomorphine and L-dopa. However, when the fish were exposed to smaller mescaline doses (or to fluphenazine) for 3 days, their ability to avoid electric shock was reduced. Apparently, mescaline induced a release of dopamine which stimulated central dopaminergic systems. Subsequently, MAO destroys the liberated dopamine. Thus, the ensuing dopamine deficit appears to be responsible for the marked changes in behavior in the chronic experiment.

Animals↗
PubMedDate not supplied

Minimally invasive direct access heart valve surgery.

We review our experience with minimally invasive direct access (MIDA) heart valve surgery in 518 patients. Two hundred fifty-two patients underwent MIDA aortic valve replacement (AVR) or repair and 266 underwent MIDA mitral valve repair or replacement. Among the 250 AVRs, 157 (63%) were men, aged 63.2 +/- 14.6 years, NYHA functional Class 2.4 +/- 0.8. The surgical approach was right parasternal in 36 (14%) or upper hemisternotomy in 216 (86%). There were four (2%) operative deaths. Perioperative complications included 14 (5.6%) reexplorations for bleeding, 7 (3%) chest wound infections, 5 (2%) strokes, and 1 (0.4%) external iliac vein injury. Follow-up was complete in 193 (77%) patients, with a mean follow-up of 12 +/- 8 months. Late complications included 2 (0.8%) nonfatal myocardial infarctions, 4 (2%) reoperations for, respectively, 2 pericardial complications, 1 paravalvar leak, and 1 infected valve. There were five (2%) late deaths from congestive heart failure, pneumonia, hemorrhage, aneurysm, and cancer. Mean follow-up NYHA Class was 1.4 +/- 0.6. For the 266 mitral patients, 145 (54.5%) were men, age 58.7 +/- 13.6 years, functional Class 2.3 +/- 0.5. The surgical approach was right parasternal in 195 (73%), lower hemisternotomy in 53 (20%), right submammary thoracotomy in 9 (3.4%), or full sternotomy through a small skin incision in 9 (3.4%). There were 2 (0.8%) operative deaths. Perioperative complications included 4 (1.5%) reoperations for bleeding, 4 (1.5%) strokes, and 5 (2%) wound infections, and 3 (1%) ascending aortic complications. Follow-up was complete in 202 (76%) patients with a mean follow-up of 9.5 +/- 6.4 months. Late complications included one (0.4%) nonfatal myocardial infarction and three (1%) reoperations all converting repairs to replacements. There were three (1%) late deaths from suicide, pneumonia, and sudden death, respectively. Mean follow-up NYHA functional Class was 1.3 +/- 0.5. We conclude that MIDA heart valve surgery is safe and effective for the majority of patients requiring isolated elective aortic or mitral valve surgery.

Adolescent↗
PubMedDate not supplied

An engineering model of dynamic cardiomyoplasty. II. Clinical applications.

Previously, a modification to the Sunagawa engineering model for the isolated left ventricle and arterial system was proposed and validated for dynamic cardiomyoplasty in an acute goat preparation. To test the hypothesis that this model may be applied to the clinical scenario in cardiomyoplasty patients, we predicted human stroke volume using the model with human clinical data from the literature. Predicted stroke volume correlated well with published stroke volume in patients who have had the dynamic cardiomyoplasty procedure. These results suggest that the modest hemodynamic improvement commonly reported after the procedure is performed may be due to diminished latissimus dorsi strength after transformation. The validity of both the original Sunagawa model and the previously proposed modification for dynamic cardiomyoplasty is further supported with these results. A nomogram methodology for predicting stroke volume after dynamic cardiomyoplasty for any particular patient is presented.

Biomechanical Phenomena↗
PubMedDate not supplied

An engineering model of dynamic cardiomyoplasty. I.

Dynamic cardiomyoplasty (DCM) is an emerging surgical procedure for heart failure in which the patient's latissimus dorsi (LD) muscle is wrapped around the heart and stimulated to contract in synchrony with the heartbeat as a cardiac assist measure. A 6 week training protocol of progressive electrical stimulation renders the normally fatigueable skeletal muscle fatigue-resistant and suitable for chronic stimulation. To date, over 500 procedures have been performed in worldwide clinical trials. Investigators typically report symptomatic improvement and modest hemodynamic improvement in patients. Controversy exists regarding the exact mechanism of DCM. To test the hypothesis that DCM augments cardiac stroke volume through improvement in systolic function, we formulated an engineering model of dynamic cardiomyoplasty to predict stroke volume. The heart and the LD were modeled as nested (series) elastance chambers, and the vasculature was represented by a two-element Windkessel model. Using five healthy goats, we verified model predictions of stroke volume for both stimulator ON beats (y = 1.00x-0.08, r = 0.87, p < 0.0001) and OFF beats (y = 1.01x+1.06, r = 0.91, p < 0.0001), where x and y are the measured and predicted stroke volumes, respectively. The model confirms that using untrained latissimus dorsi applied to the normal myocardium produces only moderate increases in stroke volume and suggests that future research should focus on increasing LD strength after training.

Cardiomyoplasty↗
PubMedDate not supplied

Bench coronary angiography: a potentially useful method to assess coronary artery disease in the older donor heart without catheterization laboratory angiography.

To assess the diagnostic accuracy of ex vivo coronary artery arteriography, 12 sheep hearts were harvested, after random multiple coronary occlusions were created. The hearts were radiographed either in the flat (n = 6) or upright suspended (n = 6) position with the aorta cross-clamped. The aortic root was cannulated with an 18-gauge needle and flushed with cold normal saline solution. Five milliliters of iodinated contrast media was injected under constant hand pressure, and angiographic views were taken with a conventional, portable x-ray machine. The aortic root was then immediately flushed with normal saline solution under constant pressure to minimize contrast contact with the vascular endothelium. Total elapsed time including film development was 7 to 10 minutes. In hearts that were radiographed lying flat, a ventriculogram was obtained because of aortic incompetence. In hearts suspended in the upright position, normal coronary anatomy and previously placed coronary occlusions were easily detected in every heart that was read blindly by angiographers. To assess the effects of the contrast media on ventricular performance, five rabbit hearts were harvested and mounted on a Langendorff apparatus for functional analysis at controlled left ventricle volumes. Diastolic and systolic left ventricular pressures were unaffected by the dye injection. This simple and rapid method to evaluate coronary anatomy of the donor heart could be potentially useful in the assessment of older donor hearts in the operating room, thus increasing the volume of donor hearts available for transplantation.

Animals↗
PubMedDate not supplied

Changing patterns in donor and recipient risk: a 10-year evolution in one heart transplant center.

BACKGROUND: Expansion of the donor pool and liberalization of recipient criteria have occurred since the introduction of cyclosporine for heart transplantation. METHODS: We sought to evaluate the impact of these changes on outcome during a 10-year period in one program. A total of 251 transplantations were retrospectively reviewed and divided into two periods (1984 to 1989 and 1990 to 1994). RESULTS: In the latter period, there were increases in donor and recipient age, degree of weight mismatch, ischemic time, bypass time, and severity of illness in the recipient before transplantation as judged by status at the time of transplantation and preoperative requirements for pharmacologic or mechanical support. Despite these changes, time to hospital discharge decreased and a trend to improved survival was seen with the use of Kaplan-Meier analysis. CONCLUSIONS: These findings suggest that improvements in perioperative and posttransplantation care have permitted a safe expansion of both the donor pool and recipient criteria for transplantation.

Adult↗
PubMedDate not supplied

Role of panel-reactive antibody cross-reactivity in predicting survival after orthotopic heart transplantation.

To test the hypothesis that elevated preformed circulating antibody levels, as measured by panel-reactive antibody levels, predict survival after orthotopic heart transplantation, we analyzed 120 consecutive patients undergoing heart transplantation at the Brigham and Women's Hospital in a retrospective, chart-review format. Prospective, donor-specific lymphocyte crossmatches were performed in all patients with a panel-reactive antibody level of 10% or greater. Both the peak pretransplantation panel-reactive antibody level and the panel-reactive antibody level obtained on the day of transplantation were analyzed with respect to the end points of the number of acute rejection episodes, presence of coronary artery disease, and overall survival after transplantation. Patients with a panel-reactive antibody level on the day of transplantation of 25% or greater, despite a negative prospective donor-specific lymphocyte crossmatch, demonstrated a trend toward reduced actuarial long-term survival compared with patients with panel-reactive antibody values less than 25% (p < 0.05). Panel-reactive antibody levels were not predictive of the number of acute rejection episodes, early (< 60 days) versus late (> or = 60 days) death, or the development of graft coronary artery disease. No episodes of hyperacute rejection were observed, even in six patients with a positive retrospective donor-specific lymphocyte crossmatch. In conclusion, an elevated panel-reactive antibody value of 25% or greater at the time of heart transplantation may be a risk factor for decreased long-term survival. A trend toward an increased risk of death caused by rejection was also observed.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMedDate not supplied

Thromboxane A2 mediates reperfusion injury after heart preservation.

To assess the role of the eicosanoid thromboxane A2, a potent vasoconstrictor and platelet activator, in reperfusion injury after heart preservation, donor rats (n = 18) were anesthetized, and their hearts were rapidly excised, arrested with cardioplegic solution, and fitted with a left ventricular balloon. Seven hearts were subjected to 45 minutes of ischemia at 15 degrees C, simulating implantation, (group 1) during which the carotid and jugular vessels of support rats were cannulated for ex vivo blood reperfusion. Remaining hearts were preserved in 4 degrees C saline solution for 3 hours followed by 45 minutes at 15 degrees C (group 2, n = 11). Before reperfusion of group 2 hearts, support rats received either vehicle (group 2a, n = 6) or thromboxane A2 receptor antagonist SQ29548 (0.2 mg/kg) (group 2b, n = 5). After 1 hour of reperfusion, left ventricular peak-systolic pressure and end-diastolic pressure were measured in all hearts at incremental ventricular volumes. The slope of the peak-systolic pressure-volume relation and the volume-axis intercept of the end-diastolic pressure-volume relation were also measured. No significant differences were noted in mean peak-systolic pressure, at any left ventricular volume, nor slope of the peak-systolic pressure-volume relation between groups, indicating that neither preservation nor SQ29548 treatment affected systolic contractile performance in this model. Through all left ventricular volume, however, end-diastolic pressure was significantly lower (p < 0.05) in group 2b compared to group 2a, and overall did not differ significantly from group 1.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗