Biomedical subjects
Publications and source records attributed to R J Shemin.
The increasing frequency of reoperation for coronary artery disease has led to the use of a variety of grafts. This report describes the catheter technique for selective opacification of a saphenous vein graft from the descending thoracic aorta to the posterior coronary circulation.
This study was undertaken to determine whether substrate enhancement with L-glutamate during periods of cold storage would improve ventricular function in transplanted hearts. Thirty-one rabbit hearts were rapidly excised and perfused with Krebs-Henseleit buffer (37 degrees C) on a Langendorff apparatus. They were arrested with hypothermic (4 degrees C), crystalloid, potassium (25 mEq/L) cardioplegia and stored at 3 degrees C for three hours, followed by reperfusion with Krebs-Henseleit buffer for one hour. Hearts were treated in one of several ways: Group 1 (n = 8) did not receive any L-glutamate and serve as controls; group 2 (n = 8) had L-glutamate (4 mmol/L) added to both the cardioplegic and reperfusate solutions; group 3 (n = 5) received L-glutamate only before ischemia; group 4 (n = 5) received L-glutamate only in the cardioplegic solution; and group 5 (n = 5) received L-glutamate only in the reperfusate. Hearts receiving L-glutamate in the reperfusate with or without its addition to the cardioplegic solution (groups 2 and 5) had the best recovery of the first derivative of positive and negative change in left ventricular peak systolic pressure and no significant changes in left ventricular compliance. Pretreatment with L-glutamate alone (group 3) resulted in no better recovery than in group 1 hearts. We conclude that addition of L-glutamate to reperfusate solutions after periods of cold storage for transplantation enhances the recovery of ventricular function.
When cold storage techniques used in cardiac transplantation are extended beyond 3 hours, there is significant depression in ventricular function. This study was undertaken to determine whether the addition of the amino acid L-glutamate or the oxygen free-radical scavengers superoxide dismutase (SOD) and catalase (CAT) during extended periods of cold storage would improve ventricular function. Fifteen rabbit hearts were placed on a Langendorff apparatus, arrested with crystalloid potassium cardioplegia, stored in iced saline solution (3 degrees C) for 5 hours, and then reperfused at 37 degrees C for 1 hour. In five hearts L-glutamate (4 mmol/L) was added to the cardioplegic and reperfusate solutions, and five hearts received SOD (1500 units/kg/L) and CAT (3500 units/kg/L), whereas in five others the cardioplegic and reperfusate solutions were unmodified. Hearts treated with L-glutamate had the best recovery of positive dP/dt (79%* glutamate vs 49%* SOD and CAT vs 36% unmodified), negative dP/dt (76%* glutamate vs 53% SOD and CAT vs 45% unmodified), developed pressure (67%* glutamate vs 51% SOD and CAT vs 45% unmodified), and coronary flow (81%* glutamate vs 79%* SOD and CAT vs 62% unmodified). We conclude that substrate enhancement with L-glutamate provides superior myocardial protection than is possible with the oxygen free-radical scavengers SOD and CAT during extended periods of cold storage for cardiac transplantation.
Neoplasms of the aorta are rare. In this report, we present a case of a malignant fibrous histiocytoma that nearly obliterated the lumen of the thoracic aorta. The neoplasm was resected and aortic continuity was reestablished with an interposition graft. This case is particularly unusual because the patient had an isolated lymph node excised 5 years previously that contained the same neoplasm.
Although coronary artery bypass grafting effectively reduces the symptoms of myocardial ischemia, its immediate effect on regional wall motion dysfunction is not well defined. This intraoperative study was undertaken to determine whether bypass grafting improves regional wall motion in areas of preoperative ischemic dysfunction. In 17 patients undergoing coronary bypass, short-axis echocardiograms were obtained with the chest open 30 minutes before and after cardiopulmonary bypass. Regional wall motion was calculated quantitatively as the percent increase in segmental wall thickness during systole, with 40% thickening or less defined as indicating ischemic dysfunction. Qualitatively, it was evaluated by visual changes in endocardial wall motion according to a graded score (0 = normal to 4 = dyskinesia). Of the 136 segments studied, 44 (32%) had evidence of ischemic dysfunction before coronary bypass. When regional wall motion was analyzed in all 136 segments after coronary bypass, there was no significant change in either quantitative indices (62% +/- 7% before grafting versus 58% +/- 6% after grafting) or qualitative indices (0.19 +/- 0.06 versus 0.17 +/- 0.06). However, in those segments with ischemic dysfunction before grafting, there was a significant increase in quantitative indices of regional wall motion after grafting (24% +/- 2% versus 50% +/- 5%; p less than 0.02). By contrast, qualitative indices continued to show no significant improvement (1.3 +/- 0.1 versus 1.05 +/- 0.2). We conclude that coronary artery bypass grafting significantly improves areas of ischemic regional wall dysfunction. These changes can be difficult to detect with visual qualitative methods and are best analyzed by techniques assessing changes in segmental wall thickness.
Mitral valve repair has been increasingly used at our hospital for mitral regurgitation with and without coronary disease. From January, 1984, to June, 1987, of 338 patients undergoing all forms of mitral valve surgery, 140 had first-time surgery for pure mitral regurgitation: 75 had valve repair, and 65 had valve replacement. Thirty-three of 75 (44%) had concomitant coronary bypass in the repair group, while 21 of 65 (32%) had coronary bypass in the replacement group. The mean functional class (3.4 versus 3.5), age (60 versus 61 years), and preoperative hemodynamics were similar in both groups. The cause of mitral regurgitation in the repair group was myxomatous change in 32 patients, ischemia in 27, rheumatic valve disease in 12, and endocarditis in 4. A Carpentier ring was used in 46, a Duran ring was used in 11, and none was used in 18. The operative mortality was 3 of 75 patients (4%) in the repair group, all with coronary artery bypass grafting, versus 2 of 65 patients (3%) in the replacement group, 1 of whom had undergone coronary artery bypass grafting. The mean postoperative functional class 15 months postoperatively was 1.12 in the repair group versus 1.15 in the replacement group. There were 7 late deaths in the replacement group and only 3 late deaths in the repair group. Actuarial survival at 30 months was 85 +/- 6% for the replacement group and 94 +/- 4% for the repair group. There were 5 late emboli (1 fatal, 4 nonfatal) after valve replacement and none after valve repair (p = 0.03).(ABSTRACT TRUNCATED AT 250 WORDS)
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The applicability of heart transplantation remains limited in part by the inability to preserve the excised heart for long periods of time. Free radical scavengers have been shown to protect the anoxic myocardium by preventing damage to the cell membrane and may, therefore, be effective in extending successful preservation of donor hearts. We perfused 10 sheep hearts for 8 hours in an ex vivo perfusion system. The effect of superoxide dismutase combined with catalase, 60,000 units/L, was studied in five sheep, and five received placebo. Control determinations and determinations after 8 hours of preservation were obtained with the heart perfused with autologous blood at 37 degrees C at an aortic perfusion pressure of 60 mm Hg and flow of 180 to 200 ml/min. After control readings, the hearts were arrested and perfused with a cold (6 degrees to 8 degrees C) oxygenated buffered crystalloid solution with or without superoxide dismutase and catalase at a perfusion pressure of 30 cm H2O for 8 hours. Left and right ventricular compliance was measured sequentially with separate intraventricular balloons. After 8 hours of ex vivo preservation, hearts receiving superoxide dismutase and catalase had significantly better left and right ventricular performance, higher myocardial oxygen consumption, and lower lactate production than the control group. The hearts preserved with superoxide dismutase and catalase showed significantly better left and right ventricular compliance, much less increase in heart weight, and no change in the diastolic pressures. The results suggest that superoxide dismutase combined with catalase may be effective in extending ex vivo preservation of hearts for cardiac transplantation.
We investigated the effects of diltiazem cardioplegia on myocardial function and infarct size in the region of the left anterior descending artery after acute occlusion and reperfusion during cardiopulmonary bypass. Sheep (30 kg) were subjected to 1 hour of regional myocardial ischemia by occlusion of the left anterior descending artery and assigned to a control (n = 8) or experimental group (n = 5). Control animals were placed on cardiopulmonary bypass and the heart arrested with potassium cardioplegia. The left anterior descending artery was released and two additional doses of 100 ml of cardioplegic solution were infused during the total cross-clamp time of 30 minutes. The animals were then weaned from bypass after 1 hour and beating, working reperfusion maintained for an additional 4 hours. The experimental group followed the same protocol except that the cardioplegic solution contained diltiazem (1.4 mg/L). Segmental myocardial function was determined by pairs of ultrasonic crystals in the area at risk, control segment, and minor axis. Global contractility was determined from maximum derivative of left ventricular pressure and cardiac output. The area at risk was determined by injecting monastral blue dye into the left atrium with the left anterior descending artery briefly reoccluded, and the area of necrosis was determined by measuring with a planimeter non-triphenyltetrazolium chloride stained areas in the sectioned left ventricle. After 5 hours of reperfusion, not only did the diltiazem group demonstrate better global contractility as defined by the derivative of left ventricular pressure (1853 +/- 292 versus 979 +/- 191, p = 0.05) but, in addition, the systolic shortening in the ischemic area improved significantly when compared with the control group (9.4 +/- 4 versus 2.13 +/- 0.77, p = 0.05). The group receiving diltiazem cardioplegia had an area of necrosis to area at risk ratio of 31.4% +/- 3%, which was significantly better than this ratio in the control group of 60.75% +/- 7% (p = 0.01). Diltiazem cardioplegia results in improved global and segmental contractility and limits the infarct size after occlusion of the left anterior descending artery and surgical reperfusion.
This study investigated the effects of the oxygen free radical scavengers superoxide dismutase and catalase, the peroxide ion inhibitor, in crystalloid potassium cardioplegic solution on infarct size and global and regional myocardial function after occlusion of the left anterior descending artery and surgical reperfusion in young sheep on cardiopulmonary bypass. After 1 hour of occlusion, the animals were randomized to receive either routine potassium cardioplegia or cardioplegia with superoxide dismutase and catalase. Global hemodynamics measured by maximum rate of pressure rise showed significant improvement after 5 hours of reperfusion in the group treated with superoxide dismutase and catalase (1843 +/- 163 versus 979 +/- 191, p less than 0.001). Regional myocardial function was measured by ultrasonic crystals implanted in the ischemic area and in a nonischemic control segment. The percent systolic shortening or bulging was calculated. At end of reperfusion in the animals treated with superoxide dismutase and catalase, there was active shortening in the ischemic area after reperfusion of +9.2% +/- 0.4% versus 2.1% +/- 0.8% in untreated animals (p less than 0.001). Infarct size measured by triphenyltetrazolium chloride staining showed significant difference (p less than 0.001) between animals treated with superoxide dismutase and catalase (0.9% +/- 0.1%) and control animals (61% +/- 70%). Superoxide dismutase and catalase given in the cardioplegic solution before reperfusion of an acutely ischemic area of myocardium enhances recovery of contractile function and results in a significant reduction in infarct size, which suggests improved salvage of the ischemic myocardium.
This study investigated the in vivo hemodynamics and pathologic changes of a unileaflet pericardial bioprosthetic valve 3 to 5 months after implantation in juvenile sheep. Group 1 had 10 sheep with tricuspid valve replacement. Group 2 had nine sheep with mitral valve replacement. Group 3 served as a control with 10 sheep that had tricuspid valve replacement with a trileaflet porcine bioprosthesis. Hemodynamic performance was satisfactory in all three groups despite prominent pathologic changes, particularly in unileaflet valves. Intrinsic cuspal calcification was present in 66% of the unileaflet tricuspid, 88% unileaflet mitral, and 25% porcine tricuspid valves. Neither cuspal tearing nor perforations were found. However, cuspal stretching and redundancy of the mobile cusp was present in six tricuspid, seven mitral unileaflet valves, and no porcine valves. Gross pericardial redundancy correlated with the microscopic appearance of distorted and separated collagen bundles. These findings suggest that multiple modes of primary tissue failure may limit the durability of this unileaflet pericardial valve.
The inhaled anesthetic nitrous oxide is used for sedation in the coronary care unit and has been advocated as an antihypertensive agent in patients after a cardiac operation. To delineate the hemodynamic effects of nitrous oxide after cardiac surgery, we studied 11 patients with a mean age of 63 years who had undergone isolated coronary artery bypass grafting. All patients had major coronary artery disease and normal preoperative hemodynamic function. When patients were in stable condition in the intensive care unit, hemodynamic measurements were made at an inspired oxygen concentration of 40% with progressive doses of nitrous oxide (0, 10, 20, 40, and 60%). Measured and calculated hemodynamic data were compared using analysis of variance. Nitrous oxide caused significant decreases in mean arterial pressure in a dose-related fashion; pressure fell 6 mm Hg at 10% nitrous oxide and 11 mm Hg at 60% nitrous oxide (6 and 13% decreases). These changes were not associated with significant alteration in pulmonary artery pressure or cardiac index. Left ventricular stroke work index decreased significantly with the administration of nitrous oxide. We conclude that, in patients with normal hemodynamic and ventricular function, the administration of nitrous oxide for its sedative and antihypertensive effects is safe in the postoperative period and may be useful, especially in patients who are candidates for early extubation.
Most patients with severe congestive heart failure have secondary pulmonary hypertension (PHT). Elevation of pulmonary vascular resistance (PVR) to greater than 480 dynes.sec.cm-5 (6 Wood units) is currently the principle hemodynamic contraindication to orthotopic cardiac transplantation. We performed serial two-dimensional Doppler echocardiographic examinations and right heart catheterizations in 24 recipients (21 men, 14-58 years old) of orthotopic cardiac transplants to determine the time course of resolution of PHT and the concomitant remodeling of the donor right ventricle. Right and left heart filling pressures declined in parallel and reached the upper normal range at 2 weeks after the transplant procedure and remained unchanged at 1 year follow-up. Mean pulmonary arterial pressure (mm Hg) decreased from 38 +/- 9 preoperatively to 22 +/- 5 at 2 weeks and was 19 +/- 5 at 1 year after the transplantation procedure. At 1 year after surgery, PVR had decreased from 202 +/- 89 dynes.sec.cm-5 preoperatively to 99 +/- 36 dynes.sec.cm-5 (p less than .001), while cardiac output increased from 3.7 +/- 1.2 to 6.3 +/- 1.5 liters/min (p less than .001). Echocardiographic analysis showed that transplant recipients had an enlarged right ventricle on day 1 after surgery, and a volume overload contraction pattern and tricuspid regurgitation was present in the majority. This increase in right ventricular size was maintained at 1 year follow-up while the incidence of tricuspid regurgitation decreased. We conclude that there is rapid resolution of moderately elevated pulmonary arterial pressures after cardiac transplantation.(ABSTRACT TRUNCATED AT 250 WORDS)
The present study was undertaken to assess the effect of L-glutamate on the extended preservation of the heart ex vivo added to a hypothermic preservative solution. Ten sheep hearts were removed after application of cold crystalloid potassium cardioplegia. The hearts were immersed in iced normal saline and right ventricular and left ventricular intraventricular balloons were connected to transducers to measure compliance. Thermistor probes were placed in the interventricular septum. The heart was mounted on a retrograde perfusion apparatus via the cannula in the brachiocephalic trunk and placed in an isolated glass cylinder. The perfusion apparatus consisted of a roller pump, a heat exchanger, and a pediatric membrane oxygenator. Control determinations and those after 8 hr of preservation were made while the hearts were perfused with enriched autologous blood. Right and left ventricular compliance, left ventricular systolic and diastolic pressures, right ventricular systolic and diastolic pressures, left ventricular dP/dt, coronary arteriovenous oxygen consumption, lactate production, and heart weight were measured. Results showed significantly improved left and right ventricular systolic function with L-glutamate preservation. Whole heart oxygen consumption in the L-glutamate group showed a 4% increase, while the placebo group showed a significant decrease in oxygen consumption after 8 hr of preservation. The glutamate-preserved hearts also showed no change in lactate production after 8 hr of preservation as compared with a 81% increase in the placebo group. After 8 hr of perfusion there was 67% increase in the heart weight of the control and a 42% increase in the L-glutamate group.(ABSTRACT TRUNCATED AT 250 WORDS)
The fabrication of the Hancock modified-orifice valve raised questions about its long-term durability. Since 1976, 315 patients (206 male, 109 female) with a mean age of 63 years underwent aortic valve replacement with 21 mm (n = 120), 23 mm (n = 153), 25 mm (n = 36), and 27 mm (n = 6) Hancock modified-orifice valves. There were five operative deaths (1.6% mortality). Two hundred sixty-two patients are alive 2 to 117 (mean 53) months postoperatively. Actuarial probability of survival at 96 months was 78% +/- 3%. Two hundred twenty-two survivors are in Functional Class I or II. Forty-three patients have had valve-related complications: thromboembolism in 25 (1.9%/pt-yr), primary valve dysfunction in eight (0.6%/pt-yr), and endocarditis in 11 (0.8%/pt-yr). Twelve patients have required reoperation (0.8%/pt-yr) for primary valve dysfunction (four patients), for endocarditis (five patients), and for perivalvular leak (three patients). At 96 months the actuarial probability of freedom from thromboembolism was 87% +/- 3%, from primary valve dysfunction 97% +/- 2%, and from endocarditis 92% +/- 3%. The probability of freedom from all valve-related complications was 78% +/- 4% and from reoperation 94% +/- 2%. The performance of this prosthesis justifies its continued use for aortic valve replacement.
Among 2,004 patients who underwent their first coronary artery bypass graft operation between January 1970 and December 1980 without concomitant valve replacement or aneurysmectomy, life-table survival was 89% at 5 years and 80% at 8 years after surgery. In a multivariate Cox model analysis, the independent correlates of long-term survival were emergent operation with cardiogenic shock (multivariate mortality rate ratio [RR] = 14.0), use of a postoperative intraaortic balloon pump (RR = 3.9), ejection fraction less than 50% (RR = 2.4), preoperative history of congestive heart failure (RR = 2.2), cardiopulmonary bypass time (RR = 1.4 for each 30-minute increment), uncorrected mitral regurgitation (RR = 1.5 for each increment of angiographic gradation), left main coronary artery narrowing (RR = 1.7) and diabetes (RR = 1.6). After controlling for these factors, age, sex and the percentage of narrowings that were bypassed were not independent correlates of long-term survival.
We compared dopamine and dobutamine following cardiac surgery in a sequential cross-over study of 9 patients who required inotropic support after volume replenishment. Seven patients had mitral valve replacement, 2 with simultaneous coronary revascularization (CABG), and 1 each with simultaneous tricuspid annuloplasty and aortic valve replacement; 1 had isolated CABG and 1 had repair of a postinfarction ventricular septal defect. Heart rate, right and left atrial pressures, pulmonary and mean arterial pressure, systemic and pulmonary vascular resistance, and cardiac index were measured and calculated. Inotropic support with dopamine or dobutamine was begun for treatment of low cardiac index within 12 hours postoperatively. Measurements were made after 20 minutes on either agent at 5-10 micrograms/kg per min when cardiac output and general clinical state were stable. Each patient was then switched to the other agent at approximately the same dose rate, titrating the dosage to the same cardiac output, and repeat measurements were made at 20 minutes when again stable. Similar dosages of dopamine (6.2 +/- 1.7 micrograms/kg/min) and dobutamine (6.7 +/- 2.5 micrograms/kg/min) produced equivalent heart rate (103 +/- 19 vs. 102 +/- 13 beats/min, p = NS), cardiac index (2.8 +/- 1.1 vs. 2.9 +/- 1.2 l/min/m2, p = NS), and pulmonary arterial pressure and vascular resistance. Mean systemic arterial pressure was significantly lower with dobutamine (59 +/- 5 vs. 67 +/- 7 mmHg, p less than 0.05) as were mean left (14 +/- 5 vs. 18 +/- 6 mmHg, p less than 0.0001) and right (9 +/- 2 vs. 11 +/- 2 mmHg, p less than 0.05) arterial pressures.(ABSTRACT TRUNCATED AT 250 WORDS)
A 31-year-old female had an ascending aortic conduit with a Bjork-Shiley valve placed for an aortic dissection. A year later she became pregnant and was placed on heparin instead of coumadin therapy. She then developed a distal aortic dissection and was hospitalized for close medical monitoring of fetal status and maturity. At 33 weeks of gestation the aortic valve thrombosed, resulting in pulmonary edema and cardiac arrest. Emergency cesarean section and replacement of the aortic valve and ascending aortic conduit was successful in salvaging mother and child. Both are well at 2 years followup. The case illustrates the hazards of prosthetic valves in pregnant patients and cardiac surgery during pregnancy. These issues are reviewed along with the details leading to successful surgical management.