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Biomedical subjects

R S Bonser

Publications and source records attributed to R S Bonser.

At least 55 records · Page 3Linked to original sources
PubMed1999

Coronary revascularisation for postischaemic heart failure: how myocardial viability affects survival.

OBJECTIVE: To assess the impact of revascularisation of viable myocardium on survival in patients with postischaemic heart failure. METHODS: 35 patients (mean (SD) age 58 (7) years) with severe heart failure (New York Heart Association (NYHA) functional class > or = III), mean left ventricular ejection fraction (LVEF) 24 (7)% (range 10-35%), and limited exercise capacity (peak oxygen consumption (VO(2)) 15 (4) ml/kg/min) were studied. 21/35 patients had no angina. Myocardial viability was assessed with quantitative positron emission tomography and the glucose analogue (18)F-fluorodeoxyglucose (FDG) (viable segment = FDG uptake > or = 0.25 micromol/min/g) in all patients before coronary artery bypass grafting. Patients were divided into two groups: group 1, > or = 8 viable dysfunctional segments (mean 12 (2), range 8-15); and group 2, < 8 viable dysfunctional segments (mean 3.5 (3), range 0-7). The two groups were comparable for age, sex, NYHA class, LVEF, and peak VO(2). RESULTS: Two patients died perioperatively and seven patients died during follow up (mean 33 (14) months). All deaths were from cardiac causes. Kaplan-Meyer survival analysis showed 86% survival for group 1 patients versus 57% for group 2 (p = 0.03). Analysis by Cox proportional hazard model revealed three independent factors for cardiac event free survival: presence of > or = 8 viable segments (p = 0.006); preoperative LVEF (p = 0.002); and patient age (p = 0.01). CONCLUSION: Revascularisation for postischaemic heart failure can be associated with good survival, which is critically dependent upon the amount of viable myocardium.

Adult↗
PubMed1998

Validation of the conductance catheter method for measurement of ventricular volumes under varying conditions relevant to cardiac surgery.

The development of the conductance catheter method has enabled continuous measurement of intraventricular volume in vivo, thus making assessment of pump performance of the heart in vivo possible using pressure-volume analysis. However, this method has not been validated under conditions where pump rate, conductance, viscosity, and temperature of the fluid in the heart chamber is changed as happens in cardiac surgery. To validate the method, pressure-volume data were measured by conductance catheter in a physical model of the human left ventricle. The volume, salinity, viscosity, and temperature of the fluid inside the model were rigorously controlled. The measured pressure-volume data were compared with the actual values to assess the accuracy and dependence of the conductance-measured volumes on salinity, viscosity, temperature, and pump rate. Conductance-measured volumes were not significantly different over a range of heart rates extending from 60 to 100 beats/min, and they were not significantly different over a salinity range of 0.2 to 2 normal saline, a viscosity range of 2.7 to 3.5 centipoise, or over a temperature range of 20 degrees C to 39 degrees C. The percentage errors between actual stroke volumes and conductance-derived volumes were of the order of 10% on average. Our data shows that for a broad range of conditions normally encountered during cardiac surgery, there is no dependence of conductance-measured volume on heart rate, viscosity, temperature, or salinity, provided the correct value of fluid resistivity is used.

Cardiac Catheterization↗
PubMed1998

Coronary revascularization in the treatment of moderate and severe postischemic left ventricular dysfunction.

Chronic postischemic left ventricular (LV) dysfunction can improve following coronary revascularization (hibernating myocardium). However, it is not clear whether the severity of LV dysfunction determines functional outcome after revascularization and the accuracy of tests to predict myocardial viability. We studied 47 patients with coronary artery disease and chronic LV dysfunction. Before coronary bypass, patients underwent (18F)2-fluoro-2-deoxy-D-glucose (FDG) positron emission tomography (PET) during euglycemic hyperinsulinemic clamp to assess viability. Global and regional LV function were assessed before and 4 to 6 months after surgery. Patients were arbitrarily divided into 2 groups with moderate and severe LV dysfunction. Group 1 (n = 26) had an ejection fraction (EF) of < or = 30% and group 2 (n = 21) > 30%. After bypass, the EF (22+/-6% vs 31+/-10%; p <0.0001) and global wall motion score (WMS) (2.05+/-0.39 vs 1.56+/-0.34; p <0.001) improved in group 1, whereas the EF (43+/-9% vs 43+/-12%; p = NS) was unchanged in group 2, although WMS tended to improve (1.42+/-0.38 vs 1.32+/-0.39; p = 0.09). The proportion of dysfunctional segments (72% vs 32%; p <0.0001) and FDG uptake in these segments (0.44+/-0.15 vs 0.34+/-0.15 micromol/g/min, p <0.0001) were greater in group 1 than in group 2. The baseline EF influenced the predictive accuracy of PET, with highest positive predictive accuracy in group 2 and highest negative predictive accuracy in group 1. Thus, coronary revascularization has the potential for greatest benefit in patients with the most severe dysfunction, but with evidence of viability, and the entity of LV dysfunction affects the predictive accuracy of viability studies.

Adult↗
PubMed1998

Multiplanar reformatting and three-dimensional reconstruction: for pre-operative assessment of the thoracic aorta by computed tomography.

INTRODUCTION: Conventional CT demonstrates pathology of the thoracic aorta. This study aimed to evaluate the additional contributions to surgical planning of multiplanar reformatting, maximum intensity projections and three-dimensional (3-D) reconstruction. DESIGN: Retrospective. SUBJECT AND METHODOLOGY: Fifty-three patients with newly diagnosed pathology of the thoracic aorta were scanned over a 15-month period; 25 scans were spiral acquisitions. Scans were acquired during and following rapid injection of 100 ml of intravenous iopromide. The reconstructed data was displayed as axial images, oblique or other multiplanar reformats and shaded surface display 3-D reconstructions. Two radiologists and two surgeons reviewed the images. The axial images were assessed initially, subsequently the reformats and 3-D reconstructed views were examined looking particularly for additional information that might add to the surgical management. RESULTS: Pathologies encountered were aortic dissection (21 patients, including two with Marfan's syndrome), saccular aneurysms (eight), fusiform aneurysms (16), aortic root and ascending aortic dilatation (seven) and coarctation (one). The relationship of aneurysms and dissections to major vessels are better shown with 3-D reconstruction or oblique reformats. Morphology of saccular aneurysms, particularly the neck, is well shown with 3-D reconstruction. Coarctation was best demonstrated by oblique reformats. There was little additional information from 3-D reconstruction or reformats in assessment of type A dissection. Improved spatial orientation by visualization in varying projections was helpful for surgical planning in certain cases of type B dissection, fusiform aneurysms and aortic root and ascending aortic root dilatation. Spiral acquisitions have the advantage of speed and hence a greater anatomical coverage for a single breath-hold. CONCLUSION: Oblique reformats and 3-D reconstruction, although using identical data as the axial images, in specific cases were felt to aid surgical assessment of aneurysms and dissections, thus assisting pre-operative planning.

Aortic Dissection↗
PubMed1998

Coronary artery bypass surgery as treatment for ischemic heart failure: the predictive value of viability assessment with quantitative positron emission tomography for symptomatic and functional outcome.

OBJECTIVES: To determine the predictive value of quantitative evaluation of myocardial viability on changes in left ventricular function, exercise capacity, and quality of life after coronary artery bypass grafting in patients with ischemic heart failure (congestive heart failure, New York Heart Association class > or = III) with and without angina. METHODS: Thirty-five patients, 14 with congestive heart failure and angina (CHF-angina) and 21 with congestive heart failure without angina (CHF-no angina) were studied at baseline and 6 months after coronary bypass grafting. Left ventricular function was evaluated with transthoracic echocardiography and radionuclide ventriculography. Myocardial viability was assessed with [18F]-2-fluoro-2-deoxy-D-glucose using positron emission tomography. Peak aerobic capacity (peak oxygen consumption) and anaerobic threshold were assessed with treadmill exercise test and quality of life with a questionnaire. RESULTS: A total of 286 of 336 dysfunctional left ventricular segments were viable. There were two perioperative deaths (5.7%) and three late deaths. Left ventricular ejection fraction increased from 23% +/- 7% to 32% +/- 9% (p < 0.0001), and a linear correlation was found between the number of viable segments and the changes in ejection fraction (r = 0.65; p = 0.0001). Receiver operating characteristics curve identified eight viable segments as the best predictor for increase of ejection fraction more than 5 percentage points. Peak oxygen consumption increased from 15 +/- 4 to 22 +/- 5 ml/kg per minute (p < 0.0001). Preoperatively, anaerobic threshold was identified in one patient from the CHF-angina group and in all from the CHF-no angina group and increased from 13 +/- 4 to 19 +/- 4 ml/kg per minute (p < 0.0001). Quality of life scores improved significantly in both groups. No correlation was found between the amount of viable dysfunctional myocardium and changes in exercise capacity or quality of life. CONCLUSIONS: In patients with postischemic congestive heart failure the amount of viable myocardium dictates the degree of improvement in left ventricular function after revascularization.

Angina Pectoris↗
PubMed1998

von Willebrand factor and urinary albumin excretion are possible indicators of endothelial dysfunction in cardiopulmonary bypass.

OBJECTIVE: Experimental evidence suggests that cardiopulmonary bypass (CPB) associated inflammatory response leads to endothelial injury and increased permeability, but this has been difficult to show clinically. We have investigated the use of von Willebrand factor (vWF), and urinary albumin excretion, as measured by the urinary albumin creatinine ratio (ACR), to demonstrate this. METHODS: A total of 23 patients undergoing elective coronary artery bypass grafting were studied. Complement fragment C3a, leukotrienne B4 (LTB4), interleukin 6 (IL6), neutrophil elastase, vWF and ACR were measured on anaesthetic induction (baseline), 20 min after starting CPB, 5 min after cross-clamp removal, 5 min, 2, 6 and 24 h after termination of CPB. Anaesthetic, CPB and myocardial protection techniques were standardised. ANOVA was performed by using the distribution free Friedman test for each measured parameter. When significance differences were found (P < 0.05), post hoc analysis with Wilcoxon signed rank test was used for comparison of each time point with the base line level and differences were only accepted as significant following the Bonferroni correction (P < 0.008). Summary measures of peak versus peak and area under the cure were also analysed for ACR with vWF. RESULTS: Peak vs. baseline levels for C3a were 4.9 vs. 2.1 microg/ml (P < 0.0001), LTB4 was 800 vs. 20 pg/ml (P < 0.0001), neutrophil elastase was 250 vs. 115 ng/ml (P < 0.001), IL6 was 620 vs. 1.4 pg/ml (P < 0.0001), vWF was 2.2 vs. 1.3 IU/ml (P < 0.0001) and ACR was 17.6 vs. 2.0 mg/mmol (P < 0.0001). C3a, LTB4 and ACR peaked during the operation. Neutrophil elastase peaked at 2 h following CPB. IL6 and vWF peaked at 6 h following CPB. The correlation coefficient between vWF and ACR following peak versus peak analysis was 0.48 (P = 0.035), and area under the curve analysis was 0.6 (P < 0.01). CONCLUSION: These results demonstrate that endothelial permeability and injury, as measured by urinary albumin excretion and vWF, respectively, are related and the use of these easily detectable and sensitive biochemical markers warrants further investigation.

Aged↗
PubMed1998

Predictive value of dobutamine echocardiography and positron emission tomography in identifying hibernating myocardium in patients with postischaemic heart failure.

OBJECTIVE: To compare the predictive value of dobutamine echocardiography (DE) and positron emission tomography (PET) in identifying reversible chronic left ventricular (LV) dysfunction (hibernating myocardium) in patients with coronary artery disease (CAD) and overt heart failure. PATIENTS: 30 patients (four women) with CAD and heart failure undergoing coronary artery bypass grafting (CABG). METHODS: Myocardial viability was assessed with DE (5 and 10 micrograms/kg/min) and PET with [18F] 2-fluoro-2-deoxy-D-glucose (FDG) under hyperinsulinaemic euglycaemic clamp. Regional (echo) and global LV function (MUGA) were assessed at baseline and six months after CABG. RESULTS: 192 of the 336 (57%) dysfunctional LV segments improved function following CABG (hibernating) and the LV ejection fraction (EF) increased from 23(7) to 32(9)% (p < 0.0001) (in 17 patients > 5%). DE and PET had similar positive predictive values (68% and 66%) in the identification of hibernating myocardium, but DE had a significantly lower negative predictive value than PET (54% v 96%; p < 0.0001). A significant linear correlation was found between the number of PET viable segments and the changes in EF following CABG (r = 0.65; p = 0.0001). Stepwise logistic regression identified the number of PET viable segments as an independent predictor of improvement in EF > 5%, whereas the number of DE viable segments, the baseline LVEF, and wall motion were not. CONCLUSIONS: DE has a higher false negative rate than PET in identifying recoverable LV dysfunction in patients with severe postischaemic heart failure. The amount of PET viable myocardium correlates with the functional outcome following CABG.

Cardiotonic Agents↗
PubMed1998

Radiofrequency catheter ablation for atrial flutter following orthotopic heart transplantation.

A 26 year old woman with a diagnosis of limb girdle muscular dystrophy and peripartum cardiomyopathy underwent orthotopic heart transplantation using standard atrial anastomoses. Recurrent atrial flutter was demonstrated in the absence of histological evidence of cellular rejection. Radiofrequency ablation of the flutter circuit was successfully performed allowing the avoidance of long term antiarrhythmic therapy. Ten weeks following ablation and cessation of amiodarone, presyncopal symptoms were found, associated with daytime and nocturnal sinus pauses of 2.9 seconds and 4.2 seconds, respectively. There was no evidence of AV node conduction impairment. In view of the continued absence of cellular rejection and the evident denervated state of the heart, the pauses reflected significant donor sinus node dysfunction; therefore, an AAIR permanent pacing system was implanted. At the time of pacemaker implantation atrial pacing at 150 beats/min did not produce significant PR interval prolongation or AV block. This case serves to advise rigorous follow up in such patients to continue to seek evidence of sinus node dysfunction potentially requiring permanent pacemaker implantation.

Adult↗
PubMed1997

Novel approach to investigate a source of microbial contamination of central venous catheters.

The potential route of contamination by skin microorganisms onto the distal tip of central venous catheters during insertion was investigated. Thirty patients undergoing cardiac surgery who required a central venous catheter (CVC) as part of their clinical management were studied. Following catheter placement, the device insertion equipment and the skin at the insertion site were sampled for microorganisms. The distal tips of the CVCs were also sampled in situ within 90 min post insertion. Bacteria were isolated from 20 of 30 (66%) CVC skin insertion sites, from 15 of 30 (50%) guidewires, and from five of 30 (16%) catheter distal tips in situ. These findings suggest that despite rigorous skin disinfection and strict aseptic technique, viable microorganisms are impacted during insertion onto the distal tip of the CVC, which may act as a subsequent nidus of infection.

Adult↗
PubMed1997

Aprotinin in aortic surgery requiring profound hypothermia and circulatory arrest.

OBJECTIVE: The use of aprotinin in cardiac surgery to improve haemostasis and reduce blood loss particularly in patient groups at increased risk of bleeding is well established. Previous retrospective studies in profound hypothermic surgery have highlighted concerns that in this circumstances aprotinin may paradoxically cause increased bleeding and intravascular thrombosis. We therefore adopted a modified protocol for administering aprotinin, which was not started until cardiopulmonary bypass had been reinstituted after circulatory arrest. METHODS: Between April 1993 and June 1995, 45 patients underwent 46 thoracic aortic procedures which required hypothermic circulatory arrest; 25 of these were emergencies. All of these patients received aprotinin. RESULTS: There were five deaths (10.8%) in hospital. Two patients with preoperative oliguric renal failure required postoperative dialysis, and a further six (13%) developed transient renal dysfunction with complete recovery. Two patients suffered postoperative stroke; one from embolisation of a severely diseased aorta, while the other had signs of an acute evolving stroke before surgery. None of the patients suffered acute Q-wave perioperative myocardial infarction. The mean blood loss was 575 ml in the first 12 h, with a mean postoperative transfusion requirement of 1 U blood. CONCLUSIONS: We cannot implicate aprotinin in increased postoperative blood loss, renal dysfunction or mortality when used with hypothermic circulatory arrest according to this protocol. Elucidating the role of aprotinin in hypothermic circulatory arrest requires a randomised prospective study.

Adult↗
PubMed1996

Intestinal permeability, gastric intramucosal pH, and systemic endotoxemia in patients undergoing cardiopulmonary bypass.

OBJECTIVE: To examine the relationship between gastric intramucosal pH, intestinal permeability, endotoxemia, and oxygen delivery in patients undergoing cardiopulmonary bypass (CPB). DESIGN: Prospective, observational study. SETTING: Tertiary care center. PATIENTS: Fifty patients undergoing elective cardiac surgery and 10 patients awaiting elective cardiac surgery. INTERVENTIONS: Patients received chromium 51-labeled ethylenediaminetetraacetic acid (51Cr-EDTA) as a marker of intestinal permeability; insertion of a nasogastric tonometer to measure intramucosal pH (pHi); insertion of a pulmonary artery catheter to measure systemic oxygen delivery and consumption variables; arterial blood sampling for plasma endotoxin by the Limulus amebocyte lysate assay; and blood and urine sampling for measurement of 51Cr-EDTA. MAIN OUTCOME MEASURES: Systemic oxygen delivery, duration of gastric mucosal acidosis, absorption of 51Cr-EDTA, appearance of systemic endotoxemia, renal dysfunction, and duration of hospital stay. RESULTS: Median (range) 24-hour urinary recovery of 51Cr-EDTA in patients was 10.6% (2.1% to 40.2%) while that in controls was 1.2% (0.7% to 2.0%, P<.001). Intestinal permeability increased during CPB. The median (range) for the lowest pHi after bypass was 6.98 (6.74 to 7.17). The pHi did not decline until CPB was discontinued and the heart took over the load of the circulation. Endotoxin was detectable (>0.2 endotoxin unit per milliliter) in the plasma of 21 patients (42%) during the study, most of whom were endotoxemic by the end of CPB. There was no evident relationship between the degree of gut permeability, endotoxemia, gut ischemia, or systemic oxygen dynamics. CONCLUSIONS: Cardiopulmonary bypass is associated with increases in gut permeability, which precede gut mucosal ischemia. In cardiac surgical patients, a low pHi is not necessarily indicative of an adverse clinical outcome. Endotoxemia as measured by the Limulus amebocyte lysate assay is common. The increased intestinal absorption of 51Cr-EDTA and gastric mucosal acidosis occur as independent phenomena and are not related in severity or time of onset.

Acidosis↗