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Biomedical subjects

R J Shemin

Publications and source records attributed to R J Shemin.

At least 73 records · Page 4Linked to original sources
PubMed1994

Reduction of myocardial necrosis by positioning the intra-aortic balloon pump in the ascending aorta.

The presence of severe peripheral vascular disease may necessitate inserting an intra-aortic balloon pump (IABP) directly into the ascending aorta. As positioning an IABP into the descending aorta may be hazardous and difficult through the ascending aorta, this experimental study sought to determine the effects of positioning an IABP in the ascending aorta on myocardial recovery during urgent surgical revascularization. The second and third diagonal coronary arteries in 30 pigs were occluded with snares for 90 min followed by 30 min of cardioplegic arrest and 180 min of reperfusion with the snares released. During the period of coronary occlusion, ten pigs received an IABP in the descending aorta, ten had an ascending aorta IABP and ten received no IABP support. The best recovery of wall motion, least tissue acidosis and lowest area of necrosis occurred when an IABP was positioned in the ascending aorta. It is concluded that myocardial recovery is enhanced when an IABP is positioned in the ascending aorta during urgent surgical revascularization.

Acidosis↗
PubMed1994

Inhomogeneous and complementary antegrade and retrograde delivery of cardioplegic solution in the absence of coronary artery obstruction.

Inhomogeneous delivery of cardioplegic solution may result in postischemic myocardial injury. This study compares the distribution of warm blood antegrade and retrograde cardioplegia to multiple discrete left ventricular myocardial regions in pigs with unobstructed coronary arteries. Cardioplegic solution was delivered antegradely and retrogradely at 150 ml/min, and flows to 1152 individual myocardial regions were determined twice for each route with four different radiolabeled microspheres. The antegrade system delivered greater flow to each gram of myocardium than did the retrograde system (1.37 +/- 0.31 versus 0.39 +/- 0.09 ml/gm per minute, p < 0.001). Flow to individual myocardial regions was significantly inhomogeneous for both antegrade and retrograde cardioplegia, but much more so for retrograde cardioplegia (coefficient of variation was 48% +/- 17% for antegrade cardioplegia and 106% +/- 16% for retrograde cardioplegia; p < 0.001). The pattern of flow to individual myocardial regions was highly reproducible for a given route of delivery as confirmed by repeated measurements with different radioactive microsphere isotopes (correlation coefficients 0.88 +/- 0.12 for AC1-AC2 and 0.84 +/- 0.10 RC1-RC2), but antegrade cardioplegia and retrograde cardioplegia patterns were significantly different and therefore complementary (correlation coefficients 0.03 +/- 0.04, p < 0.001). These findings support the routine combined use of antegrade cardioplegia and retrograde cardioplegia to enhance delivery of cardioplegic solution to all regions of the heart and minimize the potential risk of postischemic myocardial dysfunction.

Animals↗
PubMed1993

A simplified method for implantation of automatic cardioverter defibrillator in patients with previous cardiac surgery.

A method of extrapericardial automatic cardioverter defibrillator implantation using bilateral limited anterior thoracotomy approach is described. The approach was used in six patients who have had previous open heart surgery. The defibrillation threshold was 15 joules in four patients and 20 joules in two. One patient died of pulmonary embolism in the tenth postoperative day. All patients were extubated within 0-18 hours. Drainage of a recurrent pleural effusion was required in one patient. This approach was found to be simple, safe, and effective in patients with previous median sternotomy. It may also be useful in patients in whom a cardiac operation may be indicated later in the course of their disease.

Anesthesia, Endotracheal↗
PubMed1993

Delayed perforation of the esophagus by a closed thoracostomy tube.

We report on a previously undocumented complication of a trocar-free thoracostomy tube--delayed perforation of a normal esophagus. The complication presented clinically with fever and copious enteric drainage four days after thoracostomy tube insertion. Diagnosis was established by a contrast study of the esophagus. Retrospectively, the postinsertion chest radiograph showed the offending thoracostomy tube tip impinging on the posterior mediastinum, displacing an indwelling nasogastric tube. Early recognition and repositioning of the thoracostomy tube is the key in preventing this rare but serious complication.

Adult↗
PubMed1993

Detrimental effects of interrupting warm blood cardioplegia during coronary revascularization.

Warm blood cardioplegia has emerged as a substitute for cold blood cardioplegia as a method of myocardial protection. However, the continuous infusion of blood in this technique may obscure the operative field and necessitate interruption of warm blood cardioplegia. This experimental study was therefore undertaken to determine whether interrupting warm blood cardioplegia during coronary revascularization would increase myocardial damage. In 30 adult pigs, the second and third diagonal vessels were occluded with snares for 90 minutes. All animals underwent cardiopulmonary bypass and 45 minutes of cardioplegic arrest. During the period of cardioplegic arrest, 10 pigs received intermittent antegrade/retrograde infusion of cold blood cardioplegic solution (4 degrees C) 10 pigs received continuous retrograde infusion of warm blood cardioplegic solution (37 degrees C) at 100 ml/min, and 10 pigs received retrograde infusion of warm blood cardioplegic solution that was interrupted for three 7-minute periods. After aortic unclamping, the coronary snares were released and all hearts were reperfused for 180 minutes. Interrupting retrograde warm blood cardioplegia resulted in more tissue acidosis during cardioplegic arrest (6.20 +/- 0.16 interrupted retrograde warm blood cardioplegia and 6.45 +/- 0.12 continuous retrograde warm blood cardioplegia, both p < 0.05 compared with 6.98 +/- 0.17 intermittent antegrade and retrograde cold blood cardioplegia), decreased echocardiographic wall-motion scores (4 [normal] to -1 [dyskinesis]; 2.06 +/- 0.30 interrupted retrograde warm blood cardioplegia, p < 0.05 compared with 3.30 +/- 0.40 intermittent antegrade and retrograde cold blood cardioplegia, 2.80 +/- 0.40 continuous retrograde warm blood cardioplegia), and increased tissue necrosis as measured by the area of necrosis/area at risk (38% +/- 5% interrupted retrograde warm blood cardioplegia, p < 0.05 compared with 21% +/- 2% intermittent antegrade and retrograde cold blood cardioplegia; 25% +/- 2% continuous retrograde warm blood cardioplegia). We concluded that interrupting warm blood cardioplegia during coronary revascularization diminishes the effectiveness of warm blood cardioplegia and results in increased ischemic damage.

Animals↗
PubMed1993

Warm versus cold blood cardioplegia--is there a difference?

This experimental study sought to compare the effectiveness of warm blood cardioplegia versus cold blood cardioplegia in protecting areas of ischemic myocardium during urgent coronary revascularization. In 40 adult pigs, the second and third diagonal vessels were occluded with snares for 90 minutes. All animals were then placed on cardiopulmonary bypass and underwent 45 minutes of cardioplegic arrest followed by 3 hours of reperfusion during which time the coronary snares were released. During the period of cardioplegic arrest, 10 pigs received antegrade continuous warm blood cardioplegic solution (37 degrees C) at 100 ml/min; 10 animals received retrograde warm blood cardioplegic solution at 100 ml/min; 10 received intermittent, antegrade cold blood cardioplegic solution (4 degrees C), and 10 animals received intermittent, antegrade/retrograde cold blood cardioplegic solution. Hearts protected with antegrade warm blood cardioplegic solution had the lowest pH values in the area at risk (6.59 +/- 0.10 antegrade warm blood cardioplegia versus 6.80 +/- 0.10 retrograde warm blood cardioplegia versus 6.72 +/- 0.18 antegrade cold blood cardioplegia versus 6.85 +/- 0.15 antegrade/retrograde cold blood cardioplegia and the highest area of necrosis (42% +/- 3% antegrade warm blood cardioplegia versus 26% +/- 2% [p < 0.05 from antegrade warm blood cardioplegia] retrograde warm blood cardioplegia versus 31% +/- 2% [p < 0.05 from antegrade warm blood cardioplegia] antegrade cold blood cardioplegia versus 21% +/- 2% [p < 0.05 from antegrade warm blood cardioplegia] antegrade/retrograde cold blood cardioplegia). We conclude that in the presence of an acute coronary occlusion with ischemic myocardium, warm blood cardioplegic solution should be given in a continuous retrograde fashion and does not result in myocardial protection superior to the protection that can be achieved with antegrade/retrograde cold blood cardioplegic solution.

Animals↗
PubMed1992

Directed atraumatic coronary sinus cannulation for retrograde cardioplegia administration.

A simple method of coronary sinus cannulation for retrograde cardioplegia administration is described that reduces cardiac manipulation. Intraoperative transesophageal echocardiography is used to direct atraumatic coronary sinus cannulation, confirm the depth of insertion of the cannula tip in relation to the ostium, and reduce overall cannulation time.

Cardiac Catheterization↗
PubMed1992

Changing profiles of failed coronary angioplasty patients: impact on surgical results.

As more high-risk patients undergo percutaneous transluminal coronary angioplasty (PTCA), the changing profiles of PTCA patients who may require emergent coronary artery bypass grafting may alter operative morbidity and mortality. This study compared profiles of recent patients undergoing emergent coronary artery bypass grafting after a failed PTCA with earlier patients to determine their impact on operative results. From 1980 to 1988, 53 patients underwent emergent coronary artery bypass grafting after a failed PTCA at the Boston University Medical Center. These patients were divided into two groups based on the year of the PTCA: group I, 1980 to 1985 (n = 18); and group II, 1986 to 1988 (n = 35). Group II patients tended to be older (age greater than or equal to 65 years, 47% group II versus 11% group I), were more likely to have unstable angina before PTCA (74% versus 33%), and had lower ejection fractions (0.53 +/- 0.02 versus 0.63 +/- 0.05) and more vessels with 50% or greater stenosis (2.1 +/- 0.2 versus 1.6 +/- 0.2). Nevertheless, there was no significant difference in the incidence of perioperative myocardial infarcts using enzyme and electrocardiographic criteria (37% in group II versus 39% in group I), 30-day operative mortality (11% in group II versus 11% in group I), or major postoperative complications (14% in group II versus 22% in group I). We conclude that despite the changing profiles of patients undergoing PTCA, which include older patients with more extensive coronary artery disease and lower ejection fractions, operative results after emergent coronary artery bypass grafting for failed PTCAs remain unchanged.

Age Factors↗
PubMed1992

Reduction of infarct size with coronary venous retroperfusion.

BACKGROUND: The purpose of this study was to determine whether coronary venous retroperfusion with pressure-controlled intermittent coronary sinus occlusion (PICSO) alone and in combination with coronary venous substrate enhancement using L-glutamate would decrease ischemic damage after surgical revascularization for an acute coronary occlusion. METHODS AND RESULTS: In 40 pigs, the second and third diagonal vessels were occluded with snares for 90 minutes followed by 30 minutes of cardioplegic arrest and 180 minutes of reperfusion with the coronary snares released. During the period of coronary occlusion, 10 pigs received PICSO using a balloon-tipped triple-lumen catheter in the coronary sinus; 10 pigs received PICSO plus oxygenated blood transfused retrograde via the PICSO catheter (7 ml/min), 10 pigs received PICSO plus an oxygenated blood L-glutamate (13 mM) solution, and 10 pigs received neither PICSO, blood, nor L-glutamate through the coronary sinus (unmodified). Hearts treated with PICSO had higher wall motion scores (1.27 +/- 0.33 for unmodified, 2.40 +/- 0.40* for PICSO, 2.45 +/- 0.20* for PICSO plus blood, 2.85 +/- 0.30* for PICSO plus L-glutamate; *p < 0.05 from unmodified where 4 is normal to -1 is dyskinesia), lower area of necrosis-to-area of risk ratio using histochemical staining techniques (73 +/- 4% for unmodified, 27 +/- 4 for PICSO; 18 +/- 2* for PICSO plus blood, 12 +/- 1* PICSO plus L-glutamate; *p < 0.05 from unmodified), significantly less tissue acidosis (pH) compared with the unmodified group (pH, -0.41 +/- 0.13 for unmodified, -0.16 +/- 0.03* for PICSO, -0.19 +/- 0.02* for PICSO plus blood, -0.20 +/- 0.08* for PICSO plus L-glutamate; *p < 0.05 from unmodified). CONCLUSIONS: Coronary venous retroperfusion with PICSO alone and in combination with coronary venous substrate enhancement using L-glutamate significantly decreases ischemic damage during urgent surgical revascularization.

Angioplasty, Balloon, Coronary↗
PubMed1992

Impaired relaxation of the human mammary artery after temporary clamping.

Internal mammary artery specimens from 17 patients were each divided into three separate rings. One ring (control) remained in Krebs solution and the other two were clamped for 30 minutes with either a soft or hard jaw clamp. Isometric tensions were measured in an organ chamber by contracting the rings twice with a thromboxane A2 mimetic, U46619, and relaxing the rings first with the endothelium-dependent agent acetylcholine followed by the endothelium-independent agent sodium nitroprusside. Endothelium-dependent maximal relaxation of the rings was impaired from control after both soft (20% versus 91%; p < 0.01) and hard (1% versus 91%; p < 0.01) jaw clamps were used. However, relaxation after use of hard jaw clamps was significantly less than after use of soft jaw clamps (1% versus 20%; p < 0.05). Endothelium-independent maximal relaxation was not impaired from control after soft jaw clamps (89% versus 97%) were applied but was significantly impaired after use of the hard jaw clamps compared with control (73% versus 97%; p < 0.01) and compared with soft jaw clamps (73% versus 89%; p < 0.05). Rings of internal mammary artery specimens from 10 patients from each experimental group were silver stained. The percentage of intact endothelial cells was significantly greater after soft jaw clamping than after hard jaw clamping (39% versus 15%; p < 0.02). These data suggest that soft jaw clamps significantly reduce the degree of vasoactive dysfunction compared with hard jaw clamps. In addition, soft jaw clamps produce fewer morphologic changes in the human mammary artery after temporary occlusion.

Acetylcholine↗
PubMed1991

Superiority of retrograde cardioplegia after acute coronary occlusion.

Because antegrade cardioplegia may limit the distribution of cardioplegia beyond a coronary occlusion, this study was undertaken to determine whether retrograde coronary sinus cardioplegia provides superior myocardial protection during revascularization of an acute coronary occlusion. In 20 adult pigs, the second and third diagonal branches were occluded with a snare for 1 1/2 hours. Animals were then placed on cardiopulmonary bypass and underwent 30 minutes of ischemic arrest with multidose, potassium, crystalloid cardioplegia. In 10 animals, the cardioplegia was given antegrade through the aortic root, whereas in 10 others, it was given retrograde through the coronary sinus. After the arrest period, the coronary snares were released and all hearts were reperfused for 3 hours. Postischemic damage in the myocardium beyond the occlusions was assessed by wall motion scores using two-dimensional echocardiography (4 = normal to -1 = dyskinesia), the change in myocardial pH from preischemia, and the area of necrosis/area of risk (histochemical staining). Hearts protected with retrograde coronary sinus cardioplegia had less tissue acidosis (change in pH = 0.08 +/- 0.03 versus 0.41 +/- 0.13; p less than 0.05), higher wall motion scores (2.0 +/- 0.6 versus 1.3 +/- 0.3; not significant), and less myocardial necrosis (43.4% +/- 3.6% versus 73.3% +/- 3.5%; p less than 0.0001). We conclude that retrograde coronary sinus cardioplegia provides more optimal myocardial protection than is possible with antegrade cardioplegia after revascularization of an acute coronary occlusion.

Acid-Base Equilibrium↗
PubMed1991

Continuous versus intermittent cardioplegia in the presence of a coronary occlusion.

Coronary artery occlusions can alter the distribution of cardioplegia and result in ischemic damage. This study was undertaken to determine whether continuous antegrade cardioplegia delivery would result in colder temperatures and provide better washout of acid metabolites than is possible with intermittent antegrade cardioplegia when coronary occlusions are present. Twenty pigs were placed on cardiopulmonary bypass and underwent 2 hours of ischemic arrest with occlusion of the middle left anterior descending coronary artery followed by 1 hour of reperfusion without occlusion of that artery. Ten pigs received intermittent (every 20 minutes) antegrade potassium crystalloid cardioplegia (4 degrees C), and 10 others had the same solution given continuously (30 mL/min). Cardioplegia distribution was assessed by continuous monitoring of myocardial pH (Khuri pH probe) and temperature in the region beyond the occlusion of the left anterior descending coronary artery. Both cardioplegic techniques resulted in tissue acidosis (continuous group, 6.69 +/- 0.08, versus intermittent group, 6.73 +/- 0.07; not significant). Average temperature in the left anterior descending coronary artery during arrest was also similar in both groups (continuous group, 18.3 degrees +/- 0.5 degrees C, versus intermittent group, 18.2 degrees +/- 0.5 degrees C). Because of these metabolic changes, both cardioplegic techniques resulted in abnormal wall motion in the anteroseptal region using two-dimensional echocardiography, but the scores were not significantly different (continuous group, 1.5 +/- 0.3, versus intermittent group, 1.6 +/- 0.4; 4 = normal to 0 = dyskinesia).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

Role of percutaneous bypass in reducing infarct size after revascularization for acute coronary insufficiency.

This study compares the effectiveness of percutaneous bypass (PB) with that of the intra-aortic balloon pump (IABP) in reducing infarct size and ischemic damage after revascularization for acute coronary occlusion. In 30 adult pigs, the second and third diagonal vessels were occluded with snares for 1 1/2 hours, followed by 1/2 hour of cardioplegic arrest and 3 hours of reperfusion with the snares released. During the period of coronary occlusion before the institution of cardiopulmonary bypass, 10 pigs were placed on PB, 10 pigs received IABP, and 10 others received no intervention (unmodified). Ischemic damage in the area at risk was assessed by echo wall motion scores (ranging from 4 indicating normal to -1 indicating dyskinesia), changes in myocardial tissue pH (delta pH) from preischemia, and the area of necrosis/area of risk (AN/AR) ratio. Hearts treated with the IABP had the highest wall motion scores (1.27 +/- 0.33 for unmodified versus 1.40 +/- 0.30 for PB versus 2.04 +/- 0.30 for IABP), the least change in pH values from preischemia (delta pH: 0.41 +/- 0.13 for unmodified versus 0.60 +/- 0.10 for PB versus 0.25 +/- 0.09 for IABP, p less than 0.05 for IABP versus PB), and the least amount of myocardial necrosis (AN/AR ratio: 73 +/- 4% for unmodified versus 43 +/- 2 for PB versus 27 +/- 4 for IABP, p less than 0.05 for PB and IABP versus unmodified and for IABP versus PB). Although the PB group experienced less myocardial necrosis than did the unmodified group, the most optimal recovery occurred in the IABP group.

Angioplasty, Balloon, Coronary↗