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Biomedical subjects

R J Shemin

Publications and source records attributed to R J Shemin.

At least 55 records · Page 3Linked to original sources
PubMed1995

Pulmonary venous flow in constrictive pericarditis.

A 35-year-old white female patient presented with radiation-induced constrictive pericarditis. Intraoperative transesophageal echocardiography revealed a uniphasic diastolic flow pattern. This pulmonary flow pattern reverted to a normal biphasic systolic/diastolic profile immediately following radical pericardiectomy. This abnormal flow pattern was previously described as typical for restrictive cardiomyopathy. However, in this case it is most likely due to a marked decrease in left atrial compliance induced by the thick fibrous scar encasing the atrial.

Adult↗
PubMed1995

Combining percutaneous bypass with coronary retroperfusion limits myocardial necrosis.

After an acute coronary occlusion that results in hemodynamic instability, the institution of percutaneous bypass (PB) can effectively support the failing myocardium. However, PB cannot augment coronary blood flow, and substantial regional myocardial necrosis can still occur. This experimental study was undertaken to determine whether combining PB with coronary venous retroperfusion using pressure-controlled intermittent coronary sinus occlusion (PICSO) would limit myocardial necrosis after an acute coronary occlusion. In 30 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 snares released. During the period of coronary occlusion, 10 pigs were placed on PB, 10 pigs received PB+PICSO, and 10 pigs received no support (unmodified). Hearts treated with the combination of PB+PICSO had the highest wall motion scores (unmodified, 1.4 +/- 0.3; PB, 1.4 +/- 0.3; PB+PICSO, 2.8 +/- 0.3 [p < 0.05 versus unmodified and PB]) and the lowest area of necrosis in the area at risk (unmodified, 73% +/- 3%; PB, 43% +/- 2%; PB+PICSO, 14% +/- 2% [p < 0.05, PB and PB+PICSO versus unmodified; p < 0.05, PB+PICSO versus PB]). We conclude that combining PB with coronary venous retroperfusion significantly limits myocardial necrosis.

Animals↗
PubMed1995

Unexplained fever after aortic valve replacement with cryopreserved allografts.

The incidence of fever of unknown origin was studied in 3 groups of patients undergoing aortic valve replacement. Fever of unknown origin was defined as a fever greater than 38.3 degrees C detected after the third postoperative day and which initiated a negative "fever work-up." Fifty patients underwent aortic valve replacement using cyropreserved allografts. Of the 49 patients who survived the operation, 13 (26%) developed fever of unknown origin. Only 1 (2%) of 51 patients, and 4 (8%) patients undergoing aortic valve replacement with a mechanical prosthesis and porcine xenograft, respectively, developed fever of unknown origin (p = 0.0034). Fever of unknown origin after allograft aortic valve replacement developed between the fourth and sixth postoperative days, with no other associated symptoms or signs. It lasted for 24 to 48 hours, and resolved without treatment. Univariate analysis revealed that fever of unknown origin occurred in younger patients (39.9 +/- 9.4 versus 50.8 +/- 11.8 years of age). The mean white blood cell count in fever of unknown origin and afebrile patients were similar (10.4 +/- 3.2 and 8.9 +/- 2.3, p = NS), both of which were significantly lower than the white blood cell count in patients with documented infection (15.0 +/- 5.2, p = 0.02; p < 0.001). No association could be demonstrated between the fever of unknown origin and gender, previous endocarditis, operative technique, cardiopulmonary bypass or cross-clamp times, ABO match, or perioperative blood transfusions. We conclude that a significant number of patients undergoing allograft aortic valve replacement develop noninfectious postoperative fever. The etiology remains unknown, but low-grade rejection cannot be excluded.

Adult↗
PubMed1995

Limiting ischemic myocardial damage using glucose-insulin-potassium solutions.

BACKGROUND: This experimental study sought to determine whether the infusion of glucose-insulin-potassium (GIK) solutions to ischemic myocardium during revascularization would decrease myocardial damage. METHODS: 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. During the periods of coronary occlusion and reperfusion, 10 pigs received GIK (glucose = 300 g/L, insulin = 50 U/L, K+ = 80 mEq/L) through the jugular vein at 1 mL.kg-1.h-1 (GIK-IV group); 10 pigs received GIK through the coronary sinus (GIK-CS group); 5 pigs received GIK through the jugular vein during reperfusion only (GIK-R group); 5 pigs received GIK through the jugular vein 2 hours prior to coronary occlusion and then during the periods of coronary occlusion and reperfusion (GIK-Pre group); and 10 pigs received no GIK (Unmodified group). Ischemic damage was assessed by wall motion scores using two-dimensional echocardiography, changes in myocardial tissue pH, and the area of necrosis in the area of risk. RESULTS: Hearts treated with GIK had significantly less tissue acidosis, higher wall motion scores, and the least tissue necrosis (14% +/- 2% GIK-Pre versus 12% +/- 2% GIK-CS versus 16% +/- 2% GIK-IV versus 25% +/- 2% GIK-R versus 73% +/- 4% Unmodified; all, p < 0.05 versus Unmodified). CONCLUSIONS: We conclude that a glucose-insulin-potassium solution reduces ischemic myocardial damage during coronary revascularization.

Animals↗
PubMed1995

Human mammary artery endothelial sparing with fibrous jaw clamping.

BACKGROUND: Temporary clamping of the internal mammary artery pedicle is required for visualization during coronary artery bypass grafting. A nylon fibril jaw surface has been developed for these clamps that exerts pressure only at discrete sites on the pedicle surface. The effect of this new jaw surface on endothelial cell function and integrity after compression is investigated in this study. METHODS: Internal mammary artery specimens from 10 patients each were divided into three separate rings, and two of these rings were clamped for 30 minutes with either a smooth or fibrous jaw clamp. Isometric tensions were measured in organ chambers after contraction by relaxing the rings with the endothelium-dependent agent acetylcholine followed by the endothelium-independent agent sodium nitroprusside. The intimal surfaces of similar rings were silver stained to assess the percentage of intact endothelium. RESULTS: Endothelium-dependent relaxation was spared after fibrous jaw clamping (75% versus 89%) but significantly impaired after smooth jaw clamping (25% versus 89%; p < 0.001). Endothelium-independent relaxation was unaffected by either intervention. The percentage of remaining intact endothelium upon silver staining was significantly less after smooth than after fibrous jaw clamping (24% versus 48%; p < 0.01). CONCLUSIONS: Foam silicone with nylon fibrils on the jaw surface of internal mammary artery clamps preserves endothelial cell function and integrity. The remaining undamaged cells also may facilitate the subsequent regeneration of a confluent endothelial cell layer.

Acetylcholine↗
PubMed1995

Role of leukocyte depletion during cardiopulmonary bypass and cardioplegic arrest.

BACKGROUND: Leukocyte depletion (LD) has been shown to be beneficial during the reperfusion of acutely ischemic myocardium; however, its role during cardiopulmonary bypass (CPB) in hearts protected with blood cardioplegia (BCP) is unknown. This experimental study sought to determine whether LD filters inserted in the CPB circuit before cardioplegic arrest and in the BCP circuit during arrest would decrease ischemic myocardial damage. METHODS: In 20 pigs, the second and third diagonal vessels were occluded for 90 minutes, followed by 45 minutes of BCP arrest and 180 minutes of reperfusion on CPB. In 5 pigs, LD filters were inserted in both the CPB and BCP circuits (LD-CPB+BCP). Five pigs had LD during BCP (LD-BCP), 5 pigs had LD during CPB (LD-CPB), and 5 pigs had no LD. Ischemic damage was assessed by wall motion scores using two-dimensional echocardiography and the area of necrosis/area of risk. RESULTS: The LD-CPB and LD-CPB+BCP groups had the highest wall motion scores and the lowest area of necrosis/area of risk. The addition of LD to BCP alone did not significantly alter wall motion scores or the area of necrosis/area of risk. CONCLUSION: Leukocyte depletion filters significantly reduce ischemic damage during acute surgical revascularization and appear to be most effective when placed in the CPB circuit before cardioplegic arrest.

Animals↗
PubMed1995

Right coronary artery stenosis: an independent predictor of atrial fibrillation after coronary artery bypass surgery.

OBJECTIVES: This study attempted to determine the importance of severe proximal right coronary artery disease as a predictor of atrial fibrillation in patients after coronary artery bypass surgery. BACKGROUND: Studies in patients undergoing noncardiac surgery have suggested that ischemia in the right coronary artery distribution is associated with a high incidence of atrial fibrillation. However, the importance of right coronary artery disease as a predictor of atrial fibrillation after bypass surgery is unknown. METHODS: The occurrence of sustained postoperative atrial fibrillation was studied prospectively in 168 consecutive patients undergoing coronary artery bypass grafting. Patients were followed up postoperatively until discharge. Severe right coronary artery stenosis was defined as > or = 70% lumen narrowing. RESULTS: Of 104 patients with proximal or mid right coronary artery stenosis, 45 (43%) had atrial fibrillation postoperatively compared with 12 (19%) of the 64 patients without significant right coronary disease (p = 0.001). Univariate predictors of atrial fibrillation included right coronary artery stenosis (p = 0.001), advancing age (p = 0.0001) and lack of beta-adrenergic blocking agent therapy after bypass surgery (p = 0.0004). Multivariate adjusted risk of developing atrial fibrillation after bypass surgery increased with the presence of severe right coronary artery disease (odds ratio 3.69, 95% confidence interval [CI] 1.61 to 8.48), advancing age (odds ratio 2.24/10 years, CI 1.48 to 3.41) and male gender (odds ratio 2.36, CI 1.01 to 5.49). The use of beta-blockers postoperatively was associated with a protective effect (odds ratio 0.4, CI 0.17 to 0.80). CONCLUSIONS: The presence of severe right coronary artery stenosis is an independent and powerful predictor of atrial fibrillation after coronary artery bypass surgery. In association with age, gender and postoperative beta-blocker therapy, these variables can be used to identify patients at increased risk for developing this arrhythmia.

Aged↗
PubMed1995

Gastrointestinal complications following cardiac surgery.

This study sought to determine which factors influence the mortality rate in patients developing gastrointestinal complications following cardiac surgery. Between July 1988 and January 1992, 2054 patients underwent cardiac surgical procedures at the Boston University Medical Center. Of these, 29 (1.4%) developed postoperative gastrointestinal complications. The overall mortality rate among these patients was 27% (8/29). Those who died following such complications had a higher incidence of New York Heart Association (NYHA) class IV and unstable symptoms (8/8, 100% versus 3/21, 14%; P < 0.0001), and an increased need for preoperative intra-aortic balloon pump support (4/8, 50% versus 1/21, 5%; P < 0.004). The need for gastrointestinal surgical intervention increased the mortality rate significantly compared with patients managed medically (8/18, 44% versus 0/11, 0%; P < 0.01). Patients with ischemic bowel also had a significantly higher mortality (5/5, 100% versus 3/24, 12%; P < 0.001). It is concluded that most patients with gastrointestinal complications following cardiac surgery can be treated, and with acceptable mortality rates. The presence of unstable symptoms, preoperative intra-aortic balloon pump support, ischemic bowel and the need for gastrointestinal surgical intervention adversely affect mortality.

Aged↗
PubMed1994

Increased left ventricular diastolic chamber stiffness immediately after coronary artery bypass surgery.

OBJECTIVES: The aim of this study was to assess the incidence and severity of left ventricular diastolic dysfunction immediately after coronary artery bypass surgery by utilizing simultaneous transesophageal echocardiographic and hemodynamic monitoring. BACKGROUND: Left ventricular diastolic dysfunction has been documented after coronary bypass surgery, but its measurement has been technically difficult to acquire and limited by dependence on loading conditions. METHODS: End-diastolic pressure-area curves were constructed before and immediately after coronary bypass surgery in 20 patients. Transesophageal echocardiographic images at the midpapillary level of the left ventricle and hemodynamic data were recorded. Volume status was manipulated to alter loading conditions, and multiple measurements were taken at each loading condition. RESULTS: Diastolic function worsened in all patients, as manifested by a postoperative leftward shift of the end-diastolic pressure-area curve. At a comparable preload, mean end-diastolic area +/- SEM decreased by 15% from 17.6 +/- 0.8 to 14.9 +/- 0.8 cm2 postoperatively (p = 0.0001). CONCLUSIONS: Left ventricular diastolic chamber stiffness frequently increases immediately after coronary artery bypass surgery. Simultaneous hemodynamic and transesophageal echocardiographic monitoring, through the construction of end-diastolic pressure-area curves, is a useful method to evaluate diastolic function and guide management after cardiac surgery.

Aged↗
PubMed1994

Enhanced preservation of acutely ischemic myocardium with transseptal left ventricular assist.

Mechanical support for acute regional ischemia without hemodynamic collapse may be achieved percutaneously with an intraaortic balloon pump (IABP) or with transseptal left ventricular assist (TLVA) while awaiting revascularization. The relative benefits of these two percutaneous transfemoral techniques for the treatment of ischemia were compared in a representative animal model. During 90 minutes of regional coronary occlusion, four groups of 8 pigs were treated with either no support (control), IABP, TLVA, or both IABP and TLVA. Cardioplegic arrest for 30 minutes to simulate coronary grafting was followed by 180 minutes of global reperfusion on bypass. In all groups regional wall motion and interstitial pH in the area at risk were significantly depressed with ischemia, but wall motion fully recovered after reperfusion. However, histochemical staining of the area of necrosis/area at risk was significantly reduced with IABP versus control (20.2% versus 34.1%; p < 0.05) and further significantly reduced with TLVA and IABP + TLVA (10.7% and 6.7% versus IABP alone; p < 0.05). We conclude that in supporting even a modest-sized myocardial region at risk (12% of the left ventricle) the area that went on to infarction was significantly reduced with the use of TLVA over IABP. Regional wall motion and myocardial pH measurements did not reflect this difference in the early reperfusion period. The benefit of TLVA over IABP during more extensive or prolonged ischemia may have real clinical significance.

Acute Disease↗
PubMed1994

Enhanced recovery of ischemic myocardium by combining percutaneous bypass with intraaortic balloon pump support.

Although percutaneous bypass (PB) can support the failing myocardium, regional ischemic damage may still occur beyond a coronary occlusion. This study sought to determine whether the addition of intraaortic balloon pump (IABP) support to PB would result in more optimal salvage of ischemic myocardium. In 30 pigs, the second and third diagonal vessels were occluded with snares for 90 minutes followed by 30 minutes of cardioplegic arrest and 3 hours of reperfusion with the snares released. During the period of coronary artery occlusion, 10 pigs were placed on PB, 10 pigs received PB plus IABP support, and 10 pigs received no support (the unmodified group). The hearts treated with the combination of PB and IABP support exhibited the highest wall motion scores (3.3 +/- 0.20 for the PB plus IABP group [p < 0.05 from the unmodified group and from the PB group]; versus 1.40 +/- 0.30 for the PB group versus 1.37 +/- 0.33 for the unmodified group), the least tissue acidosis (change in pH, -0.30 +/- 0.2 for the PB plus IABP group [p < 0.05 from the PB group] versus -0.60 +/- 0.10 for the PB group versus -0.41 +/- 0.13 for the unmodified group), and the least area of necrosis (25% +/- 5% for the PB plus IABP group [p < 0.05 from the unmodified group and from the PB group]; versus 43% +/- 2% for the PB group [p < 0.05 from the unmodified group] versus 73% +/- 3% for the unmodified group).(ABSTRACT TRUNCATED AT 250 WORDS)

Acidosis↗
PubMed1994

Systolic anterior motion of the mitral valve after valve repair without an annular ring.

A 78-year-old woman underwent mitral reconstruction, consisting of a quadrangular posterior leaflet resection without a concomitant annular ring, for symptomatic mitral regurgitation. Postoperatively she became hypotensive while being treated with dopamine. Transesophageal echocardiography revealed systolic anterior motion of the mitral valve with significant mitral regurgitation. With discontinuation of the dopamine regimen, institution of phenylephrine administration, and volume loading of the ventricle the systolic anterior motion disappeared as did the mitral regurgitation. The patient recovered uneventfully.

Aged↗
PubMed1994

Thoracotomy for repair of left ventricular aneurysm in a patient with patent coronary bypass grafts.

A 72-year-old man presented with a posterior left ventricular aneurysm 5 years after undergoing quadruple coronary artery bypass grafting. An angiogram demonstrated patent saphenous vein grafts, but also showed incidental asymptomatic aortic aneurysms. Left ventricular endoaneurysmorrhaphy was performed through a left thoracotomy. This approach affords excellent exposure of a posterior left ventricular aneurysm, averts many of the risks associated with reoperation, and should be considered in patients who have undergone a median sternotomy and who do not require myocardial revascularization.

Aged↗
PubMed1994

Descending aortic dissection originating from a juxtaductal traumatic aneurysm: technical considerations.

A 65-year-old male presented with a descending aortic dissection. His past history was remarkable for severe blunt chest trauma 26 years prior to presentation. Operative and pathologic findings included a posttraumatic pseudoaneurysm of the thoracic aorta and an aortic dissection that originated from the orifice of the pseudoaneurysm. The ductal fovea, the mouth of the pseudoaneurysm, is an area that may be more susceptible to accelerated atherosclerosis and the complications of atherosclerosis including aortic dissection.

Aged↗
PubMed1994

Aortic valve replacement with cryopreserved allografts: mid-term results.

OBJECTIVE: Analysis of the clinical and echocardiographic mid-term results following aortic valve replacement (AVR) with cryopreserved allografts. DESIGN AND SETTING: A cohort study in a tertiary care center. PATIENTS: Fifty patients underwent allograft AVR during the years 1987 through 1992. There were 44 men and 6 women with a mean age of 47.6 +/- 12.2 years (range 22 to 72 years). Indications for operation included: aortic stenosis (AS) 15 patients, aortic regurgitation (AR) 24, and mixed 11. The etiology was: congenital 22, rheumatic 8, degenerative 5, senile calcific 4, malfunctioning aortic valve prosthesis 5, and active endocarditis 6. OUTCOME MEASURES: Early mortality and morbidity; mid-term survival, functional class, and valve related complications; and two-dimensional Doppler echocardiography to assess valve structure and function. RESULTS: Two patients (4%) died perioperatively of noncardiac or valve related causes. Long-term follow-up ranged from 4 to 60 months (median 34 months), with no late mortality, recurrence of endocarditis, or thromboembolic events. Thirty-nine patients were in New York Heart Association (NYHA) Class I (83%) and 7 (15%) in Class II. Of these, echocardiogram showed trace or no AR in 42 (98%) and 2+ AR in 1. One allograft was re-replaced with a mechanical valve due to technical failure. One patient was in NYHA Class III with normal allograft function and 4+ mitral regurgitation. CONCLUSIONS: Replacement of the aortic valve by a cryopreserved allograft can be performed safely, and is particularly useful in the setting of active endocarditis and failed prior prosthetic valve. Mid-term clinical results and valve durability at 5 years are excellent.

Adult↗
PubMed1994

Allograft aortic valve replacement. A comparison of the free-hand technique versus aortic root replacement.

OBJECTIVE: Comparing the results of aortic valve replacement (AVR) with cryopreserved allografts using two operative techniques: the free-hand and aortic root replacement. DESIGN AND SETTING: A cohort study in a tertiary care center. PATIENTS: Fifty eight patients underwent allograft AVR during the years 1987-1994. The free-hand technique was used in 40 patients (group A) and aortic root replacement in 18 (group B). OUTCOME MEASURES: Perioperative morbidity, mortality, blood transfusion requirement and length of hospital stay. Mid-term survival, functional class and valve related complications. RESULTS: Early mortality-2 patients (11%) in group B, none in group A (p = 0.09). Patients in group B received more donor exposure from blood products than group A (28.4 +/- 29.8 donors versus 3.8 +/- 6.1 donors, p < 0.00001). Perioperative complications occurred more often in group B (p = 0.042). However, the length of hospital stay was similar. Long-term follow-up ranged from 1 to 73 months (median 43 months). There was one non-valve related late death. No recurrence of endocarditis, or thromboembolic events were observed. 96% of the patients were in NYHA class I or II. Of these, echocardiogram showed trace or no aortic regurgitation (AR) in 96%. In group A one allograft was rereplaced with a mechanical valve for a technical failure, and mild and moderate AR were documented in two patients. This was not significantly different from group B. CONCLUSIONS: Aortic allograft durability at 6 years is excellent and the overall valve-related complication rate is extremely low. The differences between the two groups were too small to demonstrate a clear-cut superiority to any of the techniques. However, our results suggest that aortic root replacement is associated with increased early morbidity and mortality when used for more complex aortic valve and aortic root pathology, whereas the free-hand technique may be associated with more mid-term valvular insufficiency.

Adult↗