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Biomedical subjects

L H Cohn

Publications and source records attributed to L H Cohn.

At least 127 records · Page 7Linked to original sources
PubMed1992

Improved distribution of antegrade cardioplegic solution with simultaneous coronary sinus occlusion following acute coronary artery occlusion.

This study was designed to evaluate the distribution of cardioplegic solution infused antegradely with simultaneous coronary sinus occlusion. After 1 hr LAD occlusion, sheep were placed on cardiopulmonary bypass. Hearts were arrested with 300 ml of cold cardioplegia and replenished with two additional doses. In group I (n = 10), antegrade cardioplegia (ACP) was given alone; in group II (n = 9), ACP was given in combination with simultaneous coronary sinus occlusion. Microspheres were infused into the cardioplegic line to determine the antegrade distribution of the solution, while a different microsphere was injected into the anterior interventricular vein to detect the venous backflow of the solution. The data showed that myocardium distal to LAD occlusion in group II received more antegrade (0.17 +/- 0.02 versus 0.06 +/- 0.02 ml/g/min, P less than 0.01, in subendocardium; and 0.15 +/- 0.03 versus 0.09 +/- 0.02 ml/g/min, P = NS, in subepicardium) and retrograde (2181 +/- 455 versus 0 counts/g/min, P less than 0.01, in subendocardium; and 2,146 +/- 527 versus 0 counts/g/min, P less than 0.01, in subepicardium) distribution of cardioplegic solution in comparison to group I. We therefore conclude that simultaneous coronary sinus occlusion significantly improves the distribution of antegrade cardioplegic solution to the regionally occluded myocardium by increasing collateral flow as well as venous backflow.

Animals↗
PubMed1992

Improved surgical approach to left atrial appendage aneurysm.

Left atrial appendage aneurysm is a rare anomaly, which usually presents with arrhythmia or cerebral embolism. Diagnostic evaluation traditionally required cardiac catheterization, and surgical resection required cardiopulmonary bypass. Utilizing intraoperative transesophageal echocardiography and surgical stapling devices, we have streamlined our operative technique, allowing resection of a left atrial appendage aneurysm without cardiopulmonary bypass. This report of two cases treated over the past decade demonstrates the evolution of our surgical technique.

Adult↗
PubMed1992

Complete prevention of myocardial stunning, contracture, low-reflow, and edema after heart transplantation by blocking neutrophil adhesion molecules during reperfusion.

This study tested the hypothesis that preventing neutrophil adhesion during reperfusion, by blocking either the neutrophil membrane CD18 integrin complex or its endothelial and myocyte ligand, intercellular adhesion molecule-1 (ICAM-1), would reduce myocardial inflammation and edema and improve reflow and ventricular function after heart preservation and transplantation. After cardioplegia and insertion of a left ventricular balloon, rabbit hearts were heterotopically transplanted into recipient rabbits either immediately (immediate, n = 12) or after preservation in 4 degrees C saline (3 hours of ischemia, n = 33). Forty-five minutes before reperfusion, recipients of preserved hearts received intravenous infusions of either saline (vehicle, n = 13), anti-CD18 monoclonal antibody (Mab) R15.7 (2 mg/kg) (anti-CD18, n = 10), or anti-ICAM-1 Mab R1.1 (2 mg/kg) (anti-ICAM, n = 10). During 3 hours of reperfusion the slope of the peak-systolic pressure-volume relation and its volume-axis intercept, the exponential elastic coefficient of the end-diastolic pressure-volume relation, the unstressed ventricular volume, and the time constant of the exponential left ventricular pressure decay after dP/dtmin were serially measured. Myocardial blood flow was measured with microspheres from which coronary vascular resistance was calculated. After explanation, the degree of myocardial inflammation, estimated by tissue neutrophil sequestration (myeloperoxidase assay) and myocardial water content were determined. Within each group no significant differences in measurements made at 1, 2, and 3 hours of reperfusion were noted. Compared with the immediate transplantation group, the vehicle group demonstrated a significant increase in myeloperoxidase activity (3380 +/- 456 versus 1712 +/- 552 microU/gm, p < 0.05), coronary vascular resistance (115.5 +/- 13.4 versus 70.5 +/- 10.6 U/gm, p < 0.05), and myocardial water content (79.8% +/- 0.4% versus 75.6% +/- 1.3%, p < 0.05), a significant decrease in unstressed ventricular volume (a leftward shift in the end-diastolic pressure-volume relation) (-0.49 +/- 0.24 versus 0.28 +/- 0.21 ml, p < 0.05), and a marked prolongation in exponential left ventricular pressure delay after dP/dtmin (156.64 +/- 3.81 versus 37.25 +/- 3.34 msec, p < 0.01).(ABSTRACT TRUNCATED AT 400 WORDS)

Abdomen↗
PubMed1992

Acute bacterial endocarditis. Optimizing surgical results.

BACKGROUND: Acute bacterial endocarditis continues to be a condition with high morbidity. Although the majority of patients are treated by high-dose antibiotics, a high-risk patient group requires surgical intervention, which is the subject of this article. METHODS AND RESULTS: From 1972 to 1991, 3,820 patients underwent heart valve replacement at the Brigham and Women's Hospital, Boston. Of this group, 158 patients underwent surgery for acute bacterial endocarditis: 109 had native valve endocarditis (NVE), and 49 had prosthetic valve endocarditis (PVE). There were 108 men and 50 women with a mean age of 49 years (range, 16-79 years); 64% were New York Heart Association functional class IV before surgery, and 12% of the group had a history of intravenous drug abuse. In both NVE and PVE groups, Streptococcus was the predominant infecting agent. Uncontrolled sepsis, progressive congestive failure, peripheral emboli, and echocardiographically demonstrated vegetations were the most common indications for surgery. Eighty-five percent of patients had a single-valve procedure, 15% had a multivalve procedure, and 34 patients had other associated major cardiac procedures. The operative mortality was 6% in NVE and 22% in PVE. Long-term survival at 10 years was 66% for NVE and 29% for PVE. Freedom from recurrent endocarditis at 10 years was 85% for NVE and 82% for PVE. The main factors associated with decreased survival overall were PVE and nonstreptococcal infection. CONCLUSIONS: The morbidity and mortality after surgical treatment of acute endocarditis depend on the site, the severity, and the subject infected. Early aggressive surgical intervention is indicated to optimize surgical results, especially in patients with nonstreptococcal infection or PVE.

Aortic Valve↗
PubMed1992

Improved recovery of heart transplants by combined use of oxygen-derived free radical scavengers and energy enhancement.

Oxygen free radical injury during reperfusion of ischemically stored heart transplants may further impair the ability of the transplanted heart to reuse substrate for recovery. We compared the effects of oxygen free radical scavengers, superoxide dismutase and catalase, either alone or combined with glucose-insulin-potassium, in an improved model of the heterotopically transplanted rat heart. Group 1 hearts (n = 8) received no preservation before transplantation and were transplanted immediately. Hearts in four other groups (n = 8 for each group) underwent cold storage (4 degrees to 6 degrees C) for 3 1/2 hours before transplantation. Five minutes before reperfusion of the transplanted hearts, recipient rats received one of the following intravenous treatments: saline (group 2), glucose-insulin-potassium (group 3), superoxide dismutase/catalase (group 4), and superoxide dismutase/catalase plus glucose-insulin-potassium (group 5). Left ventricular end-diastolic pressure, rate of rise of left ventricular pressure, myocardial blood flow, coronary resistance, and tissue adenosine triphosphate content of the heart transplants were assessed during or at the end of 2 hours of reperfusion. Hearts treated with superoxide dismutase/catalase alone showed improvement of end-diastolic pressure and myocardial blood flow. The use of glucose-insulin-potassium alone did not facilitate the recovery of transplanted hearts. In contrast, the combined use of superoxide dismutase/catalase plus glucose-insulin-potassium resulted in a superior recovery of all functional and hemodynamic parameters. These results indicate that free radical scavengers in the presence of glucose-insulin-potassium significantly improve functional recovery in the setting of heart transplantation.

Animals↗
PubMed1992

Controlled reperfusion of the regionally ischemic myocardium with leukocyte-depleted blood reduces stunning, the no-reflow phenomenon, and infarct size.

Open-chest sheep underwent 90 minutes' occlusion of the diagonal branch of the left anterior descending coronary artery, followed by vented cardiopulmonary bypass. After 30 minutes of cardioplegic arrest, simulating distal anastomoses, the occlusion on the coronary artery branch was released. Controlled reperfusion (40 to 50 mm Hg, 135 to 150 ml/min) for the first 20 minutes was delivered at the aortic root with either unmodified whole blood (control, n = 7) or blood passed through leukocyte filters (filters, n = 7). Serial measurements were made during 3 additional hours reperfusion off cardiopulmonary bypass. During ischemia, the major determinants of infarct size, which include area at risk, collateral myocardial blood flow, and rate-pressure product were not significantly different between groups. Overall, during reperfusion, mean left ventricular stroke work index in the filter group was greater than in the control group (28.7 +/- 5.8 versus 12.6 +/- 6.4 x 10(3) erg/gm, p less than 0.05), as was mean rate of rise of left ventricular pressure (1900 +/- 260 versus 1348 +/- 279 mm Hg/sec, p less than 0.05). Myocardial blood flow to the area at risk at 3 1/2 hours of reperfusion in the filter group was also significantly better than in the control group (0.57 +/- 0.15 versus 0.27 +/- 0.05 ml/min/gm, p less than 0.05), as was necrotic area as a percentage of area at risk (40% +/- 6% versus 70% +/- 5%, p less than 0.05). These results demonstrate amelioration of myocardial stunning and the no-reflow phenomenon, as well as decreased infarct size. We conclude that controlled reperfusion with leukocyte-depleted blood is superior to whole-blood reperfusion for the surgical treatment of acute regional ischemia.

Animals↗
PubMed1991

Mitral valve surgery: replacement vs reconstruction.

In comparative series, valve repair has been effective, with few of the problems--notably, thromboemboli--associated with replacement procedures. Although many patients are elderly and have coronary artery disease, reparative surgery not only is low-risk but also allows earlier intervention, before irreversible left ventricular damage occurs.

Echocardiography↗
PubMed1991

Doppler echocardiographic study of porcine bioprosthetic heart valves in the aortic valve position in patients without evidence of cardiac dysfunction.

To study the natural history of the hemodynamic performance of bioprosthetic heart valves, Doppler echocardiograms were recorded in a group of clinically stable patients at 2 and 5 years after replacement of native aortic valves with bioprosthetic valves. Eighteen patients completed a 2-year and 26 patients a 5-year follow-up examination. The effective orifice areas of identical models of bioprosthetic valves (Hancock II) were determined in vitro in a left-sided heart pulse duplicator system. In vivo Doppler-derived effective orifice areas were compared with the in vitro measurements for the same valve size. At both the 2- and 5-year follow-up examinations, the Doppler-derived effective orifice area was significantly less than the in vitro area (p less than 0.0001 at each interval). Ten of 16 valves evaluated serially decreased greater than 0.20 cm2 in the Doppler-derived effective orifice area between studies. The mean decrease in effective orifice area in valves evaluated serially was 0.25 +/- 0.29 cm2 (p less than 0.005). The peak transaortic gradient increased from 21 +/- 6 to 27 +/- 8 mm Hg (p less than 0.01). The mean transaortic gradient increased from 12 +/- 4 to 15 +/- 7 mm Hg (p less than 0.05). It is concluded that serial Doppler echocardiographic studies demonstrate a deterioration in the hemodynamic performance of bioprosthetic valves over time in patients with no symptoms or signs of valvular dysfunction and that Doppler echocardiography may be useful for identifying subclinical bioprosthetic valvular dysfunction.

Adult↗
PubMed1991

Doppler echocardiographic comparison of the Carpentier and Duran anuloplasty rings versus no ring after mitral valve repair for mitral regurgitation.

To compare the hemodynamic results of different anuloplasty techniques of primary valve repair for mitral regurgitation, 122 patients were prospectively studied with Doppler echocardiograms 5 to 10 days after operation. Seventy-seven patients had mitral valve prolapse, 27 had coronary artery disease, 13 patients had rheumatic mitral valve lesions and 5 patients had infective endocarditis. Forty-eight patients received the flexible Duran ring, 46 received the more rigid Carpentier ring and 28 patients received no ring. Doppler echocardiography demonstrated a significant decrease in mitral valve area estimated by the pressure half-time method in patients who received either a Carpentier (2.6 +/- 0.8 cm2) or Duran ring (2.8 +/- 0.8 cm2) when compared with patients who received no ring (3.2 +/- 0.7 cm2) (p = 0.01). No significant differences were observed for peak transmitral diastolic velocity, peak transmitral diastolic gradient, or the grade of mitral regurgitation by color flow Doppler mapping between patients with and without rings. The etiology of mitral disease and concomitant surgical procedures accompanying mitral valve repair did not significantly influence mitral valve area, peak velocity or peak gradient. These data suggest that Carpentier and Duran rings decrease the hemodynamic mitral valve area; however, the decrease in valve area is small and not associated with a clinically important increase in transvalvular gradient.

Echocardiography, Doppler↗
PubMed1991

Frequency of deep venous thrombosis in asymptomatic patients with coronary artery bypass grafts.

The frequency of deep vein thrombosis (DVT) in patients undergoing coronary artery bypass graft (CABG) surgery has not been established. Therefore to estimate the frequency of clinically silent DVT, we performed ultrasound examinations of the leg veins in 29 asymptomatic CABG patients before hospital discharge. We used high-resolution B-mode ultrasonography with color Doppler imaging. Fourteen (48.3%, 95% confidence interval 30.1 to 66.4%) had 20 documented leg vein thromboses, and all but one patient had DVT limited to the calf veins. Of the 20 thrombi 10 (50.0%) were present in the leg ipsilateral and 10 (50.0%) in the leg contralateral to the saphenous vein harvest site. None of the DVTs were suspected clinically. DVT was not associated with any local sign attributed to saphenous vein harvest such as pitting edema, incisional drainage, or local tenderness or with any putative risk factor for DVT such as cigarette use, distant history of malignancy, or varicose veins. Follow-up of these patients 5 to 11 months after CABG surgery showed no clinical evidence of DVT or pulmonary embolism. Our findings indicate that asymptomatic DVT of the calf occurs with surprisingly high frequency, 44.8% after CABG surgery. Future studies in patients undergoing CABG surgery should address the natural history of asymptomatic DVT, determine its clinical importance, and develop optimal strategies for prophylaxis and treatment.

Aged↗
PubMed1991

Pulmonary artery balloon counterpulsation for intraoperative right ventricular failure.

Two cases of severe low cardiac output and right ventricular failure after coronary artery bypass grafting necessitated pulmonary artery balloon counterpulsation after intraaortic balloon pumping and maximal inotropic/pressor support were unsuccessful in maintaining a satisfactory cardiac output. Hemodynamic improvement was sufficient to allow removal of the device 2 and 3 days postoperatively, with survival in 1 patient. Pulmonary artery counterpulsation is less morbid in comparison with other mechanical methods of right ventricular support and is applicable in right ventricular failure of intermediate severity.

Aged↗
PubMed1991

Atrioventricular valve replacement with a Hancock porcine xenograft.

The Hancock porcine xenograft valve was the first commercially prepared, quality-controlled tissue valve. The National Institutes of Health group began implantation of this valve in 1970 and reported on the first 5 years of their results, which was one of the longest follow-ups of that valve at that particular time. Since then there have been a number of centers that have had long-term experience with thousands of these valves. In retrospect, it is now clear that some of the conclusions made by the National Institutes of Health group have not come to pass, such as this valve being the "valve of choice" for all patients. "Valve of choice" is a relative term and may be one valve for one patient and another valve for another patient. This report was important in bringing together some of the first medium-term data and pointing out that, even in this valve, there was some small degree of thromboembolism. The paper also provided a historical look at the methods of data analysis that were in use in the early 1970s compared with those now used in 1991. Actuarial curves were not yet commonly used, nor were percent/patient-year linearized results. Valve types were mixed as well. Hemodynamic data, always a strong point of National Institutes of Health data analysis, were excellent. The use of this valve became a fairly standard device and has been retrospectively analyzed by a number of centers, suggesting that now it is better used in the older patient or in patients who cannot take warfarin sodium.(ABSTRACT TRUNCATED AT 250 WORDS)

Bioprosthesis↗
PubMed1991

Coronary bypass grafting with totally calcified or acutely dissected ascending aorta.

From August 1984 through November 1988, 10 of 2,658 patients undergoing coronary artery bypass grafting had ascending aortic disease that was not amenable to proximal anastomoses for coronary bypass grafting. This was due to a calcified aorta in 6 and acute aortic dissection in 4. There were 5 male and 5 female patients with a mean age of 71 years. Cannulation site was the femoral artery in 5, ascending aorta in 3, and aortic arch in 2. Profound hypothermia and ventricular fibrillation, with no cross-clamp or cardioplegia, was used in 9 patients, and circulatory arrest in 1. In 8 patients a single internal mammary artery was used as the total inflow with a saphenous vein graft brought off the internal mammary artery to one or more distal left-sided coronary vessels. Bilateral internal mammary arteries were used in 2 other patients. Operative mortality was zero. There was one perioperative myocardial infarction and one transient stroke without sequelae. All patients have done well from 1 to 6 years postoperatively. These data support the use of internal mammary arteries as single or bilateral proximal conduits for other venoarterial bypass grafts when the aorta is extensively diseased either by calcification or dissection.

Aged↗
PubMed1991

Load dependence of the effective regurgitant orifice area in a sheep model of aortic regurgitation.

Treatment of patients with aortic regurgitation with vasodilators reduces regurgitant volume, ventricular dilation and left ventricular mass. Although these effects are presumably due to afterload reduction, it is also possible that the aortic regurgitant orifice area is not constant. To test the latter hypothesis, aortic regurgitation was created in 10 open chest sheep by partial resection of the noncoronary leaflet under direct visualization. Regurgitant flow was measured with an aortic supravalvular electromagnetic probe; aortic and left ventricular pressures were measured with catheter-tipped micromanometer pressure transducers. The effective regurgitant orifice area was calculated by a modification of the continuity equation in a manner similar to the Gorlin equation. The regurgitant orifice area was measured three times: after aortic regurgitation was created, after mean arterial pressure was increased by 15 to 25 mm Hg with intravenous dopamine and after mean arterial pressure was reduced by 15 to 25 mm Hg with intravenous sodium nitroprusside. Comparison of regurgitant volumes and areas obtained after creation of aortic regurgitation and at the conclusion of the experiment in the absence of dopamine or sodium nitroprusside demonstrated no significant change over time. Dopamine administration was associated with an 86 +/- 81% increase in regurgitant volume (p less than 0.01) and a 38 +/- 44% increase in regurgitant orifice area (p less than 0.01). Sodium nitroprusside administration resulted in a 51 +/- 14% decrease in regurgitant volume (p less than 0.001) and a 28 +/- 21% reduction in regurgitant orifice area (p = 0.007). In this model of acute aortic regurgitation, the effective regurgitant orifice area was altered by increasing or decreasing the aortic transvalvular pressure gradient.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

Valvular surgery.

The collection of clinical cardiac surgical articles published in the last year about valvular heart disease emphasizes the continuing accrual of data that compare prosthetic and bioprosthetic valves and suggest advantages and disadvantages of both: the indications for and long-term results of aortic valve replacement, particularly in patients with left ventricular dysfunction; newer elements of mitral valve reconstruction; and debate about the best operation for the tricuspid valve. A miscellaneous collection of interesting articles discusses endocarditis and anticoagulation in the pregnant patient who undergoes heart surgery.

Bioprosthesis↗