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Biomedical subjects

L H Cohn

Publications and source records attributed to L H Cohn.

At least 235 records · Page 13Linked to original sources
PubMed1982

Inotropic contractile reserve: a useful predictor of increased 5 year survival and improved postoperative left ventricular function in patients with coronary artery disease and reduced ejection fraction.

The increase in left ventricular ejection fraction produced by postextrasystolic potentiation or epinephrine infusion has been used to demonstrate inotropic contractile reserve in patients with coronary artery disease and a depressed ejection fraction (less than 0.50). Prior studies have shown that a change in ejection fraction of 0.10 or more after postextrasystolic potentiation or epinephrine infusion is helpful in discriminating those patients with a better short-term (1 year) prognosis whether treated medically or surgically. This study related inotropic contractile reserve to 5 year prognosis in 54 patients receiving postextrasystolic potentiation or epinephrine infusion between 1971 and 1974. Current left ventricular function in surviving patients was assessed with radionuclide ventriculograms whenever possible. Five year survival was significantly better in patients with an initial change in ejection fraction greater than 0.10 in both the surgically treated group (16 of 20 versus 5 of 15, p less than 0.01) and the medically treated group (6 of 8 versus 1 of 11, p less than 0.01). Furthermore, among the surviving patients in the surgical group, current ejection fraction in the radionuclide ventriculogram was significantly greater in patients who demonstrated inotropic contractile reserve in their 1971 to 1974 contrast left ventriculogram. These findings support the concept that coronary revascularization enhances function of ischemic but viable myocardium.

Angina Pectoris↗
PubMed1982

Determinants of operative survival following combined mitral valve replacement and coronary revascularization.

To determine the operative survival rate following combined mitral valve replacement (MVR) and coronary artery bypass graft (CABG) operation, we evaluated 100 patients, who were seen consecutively at the Peter Bent Brigham and Brigham and Women's Hospital from 1972 to 1982. There were 63 men and 37 women; the mean age was 62 years. Thirty-six patients were in New York Heart Association (NYHA) Functional Class III, and 64 were in functional Class IV. Mitral regurgitation was predominant in 76 patients; mitral stenosis, in 24. Emergency operations were performed in 15 patients, and elective or semielective operations were performed in 85. There were 18 operative deaths (18%): 9 in patients having elective operations (10.5%) and 9 in those having emergency operations (60%; p less than 0.01). Significant preoperative factors related to operative death were NYHA functional class, increased pulmonary vascular resistance, lower cardiac index, and lower ejection fraction in the nonsurvivors. The rate of survival did not differ according to sex, age, or degree of coronary artery disease. In addition, myocardial protection with potassium cardioplegia and complete coronary revascularization significantly reduced operative mortality in the elective group of patients but did not alter the mortality in the emergency group.

Adult↗
PubMed1982

The in-hospital risk of rereplacement of dysfunctional mitral and aortic valves.

From January 1, 1972, to January 1, 1981, 1282 consecutive valve replacements were performed at the Peter Bent Brigham Hospital. Fifty-eight of these (4.5%) were rereplacements: 14 for prosthetic valve subacute bacterial endocarditis (SBE), 29 for primary valve dysfunction (PVD) and 15 for perivalvular leak (PVL). Aortic rereplacement was done in 27 patients (eight for SBE, 10 for PVD and nine for PVL) and mitral rereplacement in 31 patients (six for SBE, 19 for PVD and six for PVL). Twenty-six patients were in New York Heart Association functional class III and 32 were in class IV. Ten class IV patients underwent emergency valve replacement (three for SBE, two for PVD and five for PVL). The overall in-hospital mortality rate for valve rereplacement was 14% (eight of 58 patients). For mitral valve rereplacement it was 13% (four of 31), compared with 6.4% (19 of 295) for initial mitral valve replacement. For aortic valve rereplacement, the mortality rate was 15% (four of 27), compared with 5.2% (23 of 440) for initial aortic valve replacement. The cause of death was low cardiac output in six patients, hemorrhage in one patient and sepsis in one patient. All of the patients who died were in functional class IV (p = 0.018). The in-hospital risk for rereplacement of a dysfunctional aortic or mitral valve is no different from that for primary valve replacement unless the patient deteriorates to class IV and requires an emergent operation.

Aortic Valve↗
PubMed1982

Limitation of myocardial infarct size after surgical reperfusion for acute coronary occlusion.

We investigated the effect of different forms of myocardial protection on infarct size and on the necrotic myocardial process after reperfusion for acute occlusion of the left anterior descending coronary artery (LAD) in dogs. Three control groups were formed: a 1 hour, 2 hour, and 6 hour locally ischemic control. Three experimental groups were locally ischemic for 1 hour and then reperfused after an additional hour of local ischemia on cardiopulmonary bypass with the heart protected by intermittent ischemia, cold potassium cardioplegia, or blood cardioplegia. To delineate the area at risk, the LAD was temporarily occluded 30 seconds before the 6 hour sacrifice time, and monastral blue dye was injected through a polyvinyl catheter placed in the left atrial appendage. The LAD area at risk (AR) was not stained. After 6 hours the heart was excised and treated with triphenyltetrazolium chloride (TTC) to define the area of myocardial necrosis (AN). The AN/AR ratio was determined for each animal by planimetry. Mean values were then computed in each of the six groups and evaluated by the Student's t test for paired data. The 1 hour control group had an AN/AR ratio of 64% +/- 5%; the 2 hour control group, 80% +/- 6%; and the 6 hour control group, 92% +/- 1%. The intermittent ischemia group had an AN/AR ratio of 83% +/- 2%; the crystalloid cardioplegic group (2 hours of ischemia) had a ratio of 69% +/- 4%, similar to the 1 hour control but significantly smaller than the 2 hour control (p less than 0.05); and the blood cardioplegia group had an AN/AR ratio of 48% +/- 8%, significantly better than any other group. These data demonstrate that myocardial necrosis after coronary occlusion is a time-related phenomenon and will increase to encompass a large fraction of the area at risk unless there is physical or pharmacologic modification during reperfusion, such as crystalloid or blood cardioplegia.

Animals↗
PubMed1981

Five to eight-year follow-up of patients undergoing porcine heart-valve replacement.

To evaluate the clinical course after porcine heart-valve replacement, we followed 128 patients for five to eight years after surgery. Aortic-valve replacement was performed in 47 patients, mitral-valve replacement in 62, and combined aortic-valve and mitral-valve replacement in 19. Four patients died within 30 days of surgery (operative mortality, 3 per cent), and 20 died later (16 per cent); the actuarial probability of survival at eight years for all patients was 80 +/- 4 per cent (mean +/- S.E.M.). Thromboemboli were found in two of 43 patients after aortic-valve replacement, in nine of 62 after mitral-valve replacement, and in four of 18 after combined aortic-valve and mitral-valve replacement. Valve dysfunction resulted from bacterial endocarditis in five patients (4 per cent) and from primary valve dysfunction in another five.

Actuarial Analysis↗
PubMed1981

Preservation of platelets and their function in prolonged cardiopulmonary bypass using prostacyclin.

The effects of prostacyclin (PGI2) with and without heparin were studied in 28 dogs that underwent 2 hours of cardiopulmonary bypass. Five groups were created: group I (six dogs) received heparin, 1.25 mg/kg; group II (six dogs) received low-dose heparin, 0.5 mg/kg, and PGI2, 500 ng/kg/min; group III (six dogs) received low-dose heparin alone; group IV (four dogs) received PGI2, 500--1000 ng/kg/min; and group V (six dogs) received ibuprofen, 12.5 mg/kg, dipyridamole, 1 mg/kg, PGI2, 20 ng/kg/min, and low-dose heparin. Significant clot deposition occurred in the oxygenators in groups III, IV and V. Platelet counts decreased to a mean of 36.8 +/- 5.7% (+/- SEM) of control in group I, which had normal clinical heparin dose for dogs, but to only 74 +/- 7% of control in group II. This improvement was significant (p less than 0.005). Platelet aggregation induced by adenosine diphosphate 60 minutes after CPB showed poor aggregation in group I but almost normal aggregation in group II. Protamine was unnecessary in groups that received PGI2. PGI2 in combination with low-dose heparin provides adequate anticoagulation during cardiopulmonary bypass in dogs, preserves platelet number and function and is associated with minimal postoperative bleeding.

Animals↗
PubMed1981

Emergency coronary revascularization.

Emergency operations for restoration of coronary artery blood flow are an effective means for treatment of unstable anginal syndromes. The risk of such operations is minimized by preoperative stabilization with medical therapy. Mechanical circulatory assistance may be a useful adjunct in some patients, especially in the presence of left main coronary obstruction. Utilization of emergency revascularization for patients with evolving myocardial infarction may be beneficial in some patients, but this approach remains controversial at present. Emergency revascularization for cardiogenic shock improves chances for survival in selected patients, and it may be combined with valve replacement, infarct resection, or repair of ruptured myocardium in patients with adequate residual contractile tissue.

Actuarial Analysis↗
PubMed1980

The effect of hemodilution on experimental myocardial infarct size.

Hemodilution is used frequently for patients undergoing elective coronary bypass surgery but relatively little is known about the effects of hemodilution on acute myocardial infarction. Left ventricular infarctions were planimetered after acute coronary occlusion in dogs treated with and without hemodilution. The control group was maintained at a normal hematocrit (40-45) while the intervention group was hemodiluted with 6% dextran in saline 30 min after left anterior descending coronary artery occlusion to a hematocrit less than 50% of control (20). Systemic arterial and left atrial pressure were maintained at control levels as were arterial pO2 and pH. Mean infarct size in the control group was 20.72 +/- 1.38% (SEM) of the left ventricle while the hemodiluted group had a mean infarct size of 18.80 +/- 2.11% of the left ventricle. Reduction of red cell mass to less than 50% of normal does not increase the size of myocardial infarction after acute coronary artery occlusion suggesting that oxygen supply to ischemic areas is maintained if systemic hypoxia is prevented.

Animals↗
PubMed1980

Functional comparison of coronary bypass grafts of the saphenous vein and internal mammary artery.

The magnitude and distribution of myocardial blood flow through a saphenous vein (SV) bypass graft and an internal mammary artery (IMA) graft (diameter greater than or equal to 2 mm) into the same left anterior descending coronary artery (LAD) (diameter congruent to 1.5 mm) were determined at rest, with atrial pacing, and with elevated left ventricular end-diastolic pressure (LVEDP) in 18 dogs. Blood flows through the native LAD, SV, and IMA grafts were similar in the resting heart. With atrial pacing (heart rate = 150% of control), flow in both the SV and IMA grafts increased but the difference was not significant. With elevated LVEDP (20 mm Hg) produced by transfusion, flow in both SV and IMA grafts increased, but, again, these increases were not significantly different. The SV and IMA bypass grafts have similar flow rates at rest and during increased functional demand, provided the grafts are larger than the vessels into which they are placed.

Animals↗
PubMed1980

Conservative operation for mitral insufficiency: critical analysis supported by postoperative hemodynamic studies of 72 patients.

From May, 1974, through December, 1978, 255 mitral annuloplasties have been performed at our institution. Forty-three Carpentier rings and 212 flexible rings were used. Simultaneously, 307 patients with predominant insufficiency were treated with a Hancock bioprosthesis. A critical analysis of the flexible ring group versus the Hancock group is presented: The average ages were 41.3 versus 43.3 years. Preoperatively, 55% versus 60% were in Functional Class III and 9.6 versus 25.4% were in Class IV. The valve lesion was caused by rheumatic disease in 91.2% versus 93.9%. A multiple valve operation was required by 51% versus 60%. There was a significant difference in the operative mortality rates (1.8% versus 11.4%). This difference was maintained for each preoperative functional class and for the isolated and multiple valve groups. There was no significant difference in the late mortality rates (1.4% versus 3.7%). The total actuarial survival rates were of 96.4% and 81% (maximum follow-up times 4.0 and 4.5 years). The incidence of embolism was 2.4% and 4.1% per patient-year, with both groups being subjected to the same anticoagulation policy. The incidence of dysfunctions was equal (3.9% per patient-year). Postoperative hemodynamic evaluation of 72 patients having annuloplasty and 129 patients having Hancock valve replacement showed basal mean transmitral gradients of 10.98 +/- 3.6 and 9.66 +/- 2.73 mm Hg. The average effective orifice areas were 1.93 +/- 0.74 and 2.25 +/- 0.46 cm2. While the bioprosthesis behaves hemodynamically like a flow-related variable orifice, the reconstructed valve orifice is dependent upon its preoperative anatomy. In conclusion, the comparison of flexible ring annuloplasty and Hancock valve replacement for mitral valve disease shows a lower operative mortality for the former and comparable medium-term postoperative course. Since both techniques have a limited durability, longer follow-up periods will soon resolve this controversial issue.

Adolescent↗
PubMed1979

Contributions of Thomas Jefferson to American medicine.

Thomas Jefferson, the third president of the United States and author of the Declaration of Independence, had a consuming interest in all fields of education and science, including the practice of medicine and public health. He actively developed medical education, supported measures for public health, and encouraged scientific research supported by the government without policy intervention. Although a close friend of eminent physicians, his rationalism and scientific method placed him ahead of many practitioners of his time. He disparaged medical quackery but actively supported therapies such as vaccination that were based on research and careful observation. The School of Medicine at the University of Virginia was Jefferson's concrete contribution to the advancement of medical education in the United States and epitomized his preoccupation with medicine and science as important cornerstones of a healthy American nation.

Education, Medical↗
PubMed1978

Changing indications for the surgical treatment of unstable angina.

From 1970 to 1977, 127 patients were operated on for unstable angina. On the basis of response to intensive medical therapy, patients were classified into a medically controlled, semielective surgery group (54 patients) and a medically uncontrolled, emergent/urgent surgical group (73 patients). There were five operative deaths. 1/54 in the medically controlled group (1.8%) and 4/73 (5%) in the medically uncontrolled group; 4/5 operative deaths occured with left main coronary stenosis. There were five late deaths during a follow-up period of 12 to 84 months, 37.5 with an actuarial survival of 83.5%. If patients with unstable angina can be medically controlled, operation can be delayed and the operative long-term survival is similar to that of elective coronary bypass. Patients who cannot be controlled medically, particularly those with left main coronary lesions, should be operated on urgently with selective use of preoperative balloon support.

Adult↗