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Biomedical subjects

R Cartier

Publications and source records attributed to R Cartier.

At least 127 records · Page 7Linked to original sources
PubMed1993

Right ventricular rupture. A complication of postoperative mediastinitis.

Mediastinitis-related right ventricular rupture is an unusual but potentially life-threatening complication of cardiac operations. Between January 1981 and December 1990, a total of 10,182 patients underwent heart operations for ischemic, valvular, and congenital heart disease at the Montreal Heart Institute. Forty-eight patients (0.5%) had postoperative mediastinitis necessitating surgical exploration and sternal debridement. The mediastinum was left open for daily irrigation with povidone-iodine and chest reconstruction was postponed. During treatment, seven patients (0.07%) had right ventricular rupture necessitating immediate surgical repair. All had ischemic heart disease before the operation. There were five women and two men, ages ranging from 52 to 65 years (mean 58 +/- 5 years). Surgical repair consisted of autologous patch covered with omentoplasty assisted with cardiopulmonary bypass. Two patients died, one during the operation of massive hemorrhage and the other 10 days after the operation of uncontrolled sepsis. Five patients survived 2 to 29 months (mean 23 +/- 10 months) after right ventricular rupture, with an overall survival of 71%. Obesity was more frequent in the patients with right ventricular rupture and was found to be a significant risk factor (multivariate analysis, p < 0.05, relative risk 3.22). Histologic examination of the right ventricle in the patient who died after a successful repair revealed fatty infiltration of the right ventricular wall. This may have predisposed the patient toward ventricular rupture. In conclusion, right ventricular rupture, an unusual event in heart surgery, is related to open sternal debridement. Favorable outcome of this complication depends on immediate surgical management, autologous repair, and the use of omentoplasty.

Aged↗
PubMed1993

Pseudoaneurysm after Bentall repair: magnetic resonance imaging assessment.

The prevalence and natural history of pseudoaneurysms (PA) following Bentall procedure has not been established. To determine the follow-up of PA in patients, the authors report their experience with magnetic resonance imaging (MRI) since 1988. Spin-echo technique suspected PA in 19 of the 27 patients who underwent aortic valve and ascending aortic replacement between 1980 and 1991. Mean PA diameter was less than 4 cm in 13 patients (group 1) and at least 4 cm in six patients (group 2). Two patients in group 1 were lost at follow-up while two others in this group died after first spin-echo examination (one death was related to PA formation). Repeated MRIs were thus possible in nine patients in group 1 and in all patients in group 2, averaging 2.2 +/- 1.1 examinations per patient for group 1 and 1.8 +/- 1.1 for group 2. PA assessed in six group 1 patients and one group 2 patient suggested thrombosed PA or postoperative hematoma. PA remained stable in two group 1 patients and one group 2 patient. One patient from group 1, in whom PA increased at follow-up, died suddenly. Four patients in group 2 required correction of PA, which had increased in diameter. Recently, addition of cine MRI has allowed visualization of turbulent flow within PA, thus increasing MRI specificity for PA diagnosis. In conclusion, MRI constitutes a reliable noninvasive imaging technique for diagnosis and follow-up of PA after Bentall repair.

Aortic Dissection↗
PubMed1993

High blood pressure and metabolic disorders are associated in the Lyon hypertensive rat.

OBJECTIVE: A large population of F2 rats, obtained from a cross between male Lyon hypertensive (LH) rats and female Lyon normotensive (LN) rats, was studied in order to assess the relationship between increased body weight, hyperlipidaemia and high blood pressure which characterize LH rats. METHODS: Mean arterial pressure (MAP) was recorded in male, conscious, freely moving LH, LN, F1 and F2 rats aged 30 weeks. Plasma total cholesterol, high-density lipoprotein-, low-density lipoprotein- and very low-density lipoprotein-cholesterol, phospholipids, triglycerides, insulin and glucose were measured. RESULTS: In the F2 cohort it was observed that high MAP was a recessive trait that depends on several genes and was unrelated to body weight. The left ventricular weight, corrected for tibia length, was correlated with MAP. Plasma total and high-density lipoprotein-cholesterol and phospholipids concentrations were lower in the F1 rats than in the LN rats, suggesting an overdominance of the LN alleles. In the F2 rats MAP was related to total, high-density lipoprotein- and low-density lipoprotein-cholesterol. Plasma triglycerides, insulin and the insulin:glucose ratio, which were higher in the LH rats than in the LN rats, were also correlated with MAP in the F2 cohort. Using stepwise multiple regression analysis, MAP remained correlated with plasma total cholesterol, insulin and the insulin:glucose ratio, but not with triglycerides. CONCLUSIONS: Hypertension in LH rats is a recessive trait that is independent of body weight. In addition, the cosegregation of blood pressure with plasma cholesterol and, to a lesser degree, with insulin levels, which was observed in the present study provides the first direct evidence that these phenotypes are associated and are not due simply to genetic drift in the Lyon model.

Animals↗
PubMed1993

Induction of immunosuppression with rabbit antithymocyte globulin: five-year experience in cardiac transplantation.

Perioperative induction of immunosuppressive treatment with rabbit antithymocyte globulin (RATG) and late introduction of cyclosporine was used in a group of 77 patients to prevent early renal dysfunction related to cyclosporine. Peak value in plasma creatinine during hospitalization for transplantation averaged 148 +/- 49 mmol/L in patients treated with RATG compared with 215 +/- 21 mmol/L in 39 patients initially treated without RATG induction (P = 0.01). Of patients treated with RATG, 65 +/- 6% remained free from acute rejection at six months versus 40 +/- 8% of untreated patients (P = 0.03). Rates of freedom from infection, from allograft coronary artery disease and from cancer are similar in both groups. Actuarial survival rates were identical in the two groups. The total number of lymphocytes, the percentage of T lymphocytes and of helper T cells were significantly lower when RATG was used. In conclusion, RATG prophylaxis given immediately after transplantation was well tolerated without complication and resulted in adequate immunosuppression to allow delayed introduction of maintenance treatment with cyclosporine.

Adult↗
PubMed1992

Apolipoprotein E phenotyping by isoelectric focusing in immobilized pH gradients and silver staining.

A simple and high resolution procedure of apoprotein E (apo E) phenotyping by isoelectric focusing with immobilized pH gradients and silver staining is described. This method needs delipidated very low density lipoproteins (isolated from 1 mL of serum) but obviates immunoblotting as well as neuraminidase treatment in routine applications because the sialylated forms are clearly separated. Immunoblotting (with polyclonal and monoclonal anti-apo E antiserum), cysteamine and neuraminidase treatment, and pI markers allowed the localization of three main alleles, xi 2, xi 3, xi 4 and the detection of variants or rare alleles (6/450 determinations). The serum amyloid A (SAA) apolipoproteins (SAA1,SAA2) could be characterized unequivocally (especially with E3 and E4). Silver staining proved more sensitive than Coomassie Brilliant Blue and needs only 5 micrograms of protein in the sample. The results of 403 normo-or hyperlipidemic patients are shown. In the group of 191 normolipidemic patients (cholesterol less than 6.40 mmol/L triglycerides less than 2 mmol/L), the relative frequency of the xi 3 allele (0.83) is higher than in other reports on Caucasians (about 0.77) whereas the xi 4 allele is lower. As previously described, we find a high frequency of the 4/3 phenotype in hypercholesterolemia and 3/2 in hypertriglyceridemia. The high frequency of the E2/E2 phenotype, usually associated with hyperlipidemia, and variants in complex hypertriglyceridemia makes the apo E phenotyping necessary in many cases of dyslipidemias.

Acrylamides↗
PubMed1992

Effect of internal mammary artery dissection on sternal vascularization.

Internal mammary artery (IMA) dissection may cause sternal devascularization and ischemia resulting in sternal wound complication. To evaluate the effect of median sternotomy and IMA dissection on sternal vascular supply, sternal bone tomography was performed 7 days and 1 month after cardiac operation in 67 patients. Seventeen nondiabetic patients had single IMA grafts, 18 had double IMA grafts, and 12 had only saphenous vein grafts or valve replacement. Twenty diabetic patients were studied after any one of these operations. Seven patients were restudied 1 month after the operation. Sternal technetium-99m-methylene diphosphate tomography was performed. The sternum was visualized and focal zones of hypoactivity represented sternal hypoperfusion. The ratio of hypoactivity area over total sternal area was calculated for every patient. After median sternotomy without single or double IMA grafts, the averaged hypoperfusion ratio was 4% +/- 1% compared with 13% +/- 3% after single IMA grafts and 24% +/- 6% after double IMA grafts (p less than 0.0001). Diabetic patients without IMA, with single IMA, and with double IMAs showed hypoperfusion areas of 5% +/- 3%, 15% +/- 5%, and 23% +/- 9%, respectively, a result similar to that of nondiabetic patients. One month after operation the hypoperfusion area decreased to 2% +/- 2% (p less than 0.05) in restudied patients. Our results indicate that IMA dissection causes a significant although partial and temporary sternal ischemia, which is more severe after double IMA than single IMA mobilization and which may be incriminated in the development of sternal wound infection. This vascularization defect was not greater among patients with diabetes mellitus.

Body Mass Index↗
PubMed1992

Success, safety, and late electrophysiological outcome of low-energy direct-current ablation in patients with the Wolff-Parkinson-White syndrome.

BACKGROUND: Percutaneous ablation of accessory pathways with the use of a defibrillator can be accomplished with high-energy direct-current (DC) shocks of 150-400 J, but complications include cardiac tamponade and sudden cardiac death, mostly resulting from significant electrical arcing and barotrauma. A new low-energy DC power source with a brief time-constant capacitive discharge delivers shocks of 2-40 J and eliminates or greatly reduces arcing. This report describes our initial experience with this device in 60 consecutive patients (mean age, 34 years; range, 9-67 years) with Wolff-Parkinson-White syndrome. Accessory pathways were located in the left free wall in 36 patients, in the right free wall in two, were posteroseptal in 18, and anteroseptal in four. Most patients (77%) had their initial diagnostic electrophysiological study and catheter ablation during the same session. METHODS AND RESULTS: Selective ablation of accessory pathways was successful in 55 patients (92%). The mean cumulative energy was 312 +/- 284 J and the mean creatine kinase MB peak (normal, 0-30 units) was 42 +/- 27 units. Patients with left free wall accessory pathways required less procedure time for ablation (2.7 +/- 0.8 versus 3.6 +/- 1.5 hours, p less than 0.0007) and less fluoroscopy time (46 +/- 24 versus 66 +/- 33 minutes, p less than 0.002). Complications were limited to transient pericarditis (three patients), one iliac artery dissection, and cardiac tamponade probably caused by catheter repositioning in the coronary sinus (one patient). An electrophysiological study was repeated in 50 of the 55 successful cases at a mean of 9 +/- 5 months. This study was normal in 48 of 50 (96%) patients. CONCLUSIONS: Low-energy DC ablation is safe and effective treatment for accessory pathways in children and adults. The long-term outcome is excellent as documented by electrophysiological restudy.

Adult↗
PubMed1992

Rate-dependent effects of diltiazem on human atrioventricular nodal properties.

BACKGROUND: Tachycardia enhances the channel-blocking effects of antiarrhythmic drugs. In contrast to the extensive data regarding the rate-dependent effects of sodium channel blockers in humans, little is known about the frequency-dependent effects of calcium channel blockers on human atrioventricular (AV) nodal properties. Accordingly, the purpose of this study was to evaluate the importance of heart rate in modulating the electrophysiological effects of diltiazem in humans. METHODS AND RESULTS: Electrophysiological studies were performed in 25 patients. Sinus node, atrial, and AV nodal function were evaluated at multiple atrial rates under control conditions and after administration of one of three intravenous doses of diltiazem designed to produce low, intermediate, and high stable plasma concentrations (designated doses 1, 2, and 3, respectively). Results were analyzed in terms of the longest and shortest cycle lengths obtainable in each patient under control and drug conditions. Plasma concentrations of diltiazem were stable and averaged 43 +/- 4, 73 +/- 6, and 136 +/- 11 ng/ml for doses 1, 2, and 3, respectively. Sinus node recovery time, intra-atrial conduction time, atrial effective refractory period, and HV interval were unaffected by diltiazem infusion. Effects of diltiazem were limited to changes in AV nodal parameters. Stable, dose-dependent increases in Wenckebach cycle length were observed after all three doses of diltiazem (increases of 54 +/- 13, 84 +/- 18, and 174 +/- 33 msec for doses 1, 2, and 3, respectively). Small nonsignificant increases in AH interval and atrioventricular effective refractory period (AVERP) were observed after dose 1 of diltiazem. At long cycle lengths, diltiazem caused modest increases in AH interval (3 +/- 4 and 25 +/- 8 msec for doses 2 and 3, respectively) and AVERP (36 +/- 12 and 70 +/- 25 msec). Drug effects were far greater at short cycle lengths (45 +/- 17 msec, 58 +/- 12 msec for AH interval and 80 +/- 24 msec, 163 +/- 41 msec for AVERP; p less than 0.05 versus values at long cycle lengths). At rapid rates, effects of diltiazem on AVERP substantially exceeded those on AV conduction, a result that could account for the beneficial effects of diltiazem during paroxysmal AV reentrant tachycardia by decreasing the excitable gap. CONCLUSIONS: Depressant effects of diltiazem on human AV nodal function are highly dependent on atrial rate; the rate-dependent actions on AV nodal refractoriness probably contribute to beneficial effects of diltiazem in patients with supraventricular arrhythmias.

Atrioventricular Node↗
PubMed1992

[Salvage heart surgery after percutaneous mitral valvuloplasty].

Percutaneous mitral valvuloplasty (PMV) for selected patients with symptomatic mitral stenosis (MS) has been proposed as a safe alternative to open mitral commissurotomy (OMC) or mitral valvular replacement (MVR). Among 146 consecutive patients undergoing PMV from March 1987 to April 1990, 18 (12%) needed urgent (8) or delayed (10) (average 7 days) corrective surgery following PMV. There were 15 women and 3 men, with a clinical incapacity class II (3) or III (15), and with an intermediate risk for PMV according to echo score (mean = 8). The indications for corrective surgery were: massive mitral regurgitation due to tearing of the anterior leaflet (6), cardiac perforations (left atrium in 2, left ventricle in 3), PMV technical failure (5), severe atrial shunting (2). Operative procedures included MVR (14), cardiac wound suturing only (3), OMC (1). Operative mortality (30 days) was 22% (4/18), equally distributed among the urgent and delayed group. The causes of postoperative death were hemorrhage (2), severe cerebral ischemia (1) and sudden death (1). Compared to operative mortality after OMC (0/17.0%) or MVR (1/32, 3.1%) as the initial treatment for MS during the same time period, cardiac operation after failed or complicated PMV carried a significantly higher mortality (p = 0.004). Therefore, optimal patient selection and aggressive corrective surgery are necessary to decrease the PMV related mortality and morbidity.

Adult↗
PubMed1992

Prevention of herpes simplex virus infection by oral acyclovir after cardiac transplantation.

Infection with herpes simplex virus is common among immunosuppressed patients. In an attempt to prevent such infection, 58 patients (group 1) who underwent cardiac transplantation between 1987 and 1990 were given acyclovir (200 mg orally three times a day) prophylactically throughout their postoperative hospital stay (mean 22 days +/- 1 day). The patients' immunosuppressive protocol included cyclosporine, azathioprine and prednisone. The course of these patients was compared to that of 24 patients (group 2) who underwent cardiac transplantation between 1983 and 1986 but were not given prophylactic antiviral treatment postoperatively. The immunosuppressive protocol in these patients consisted of cyclosporine and prednisone. Herpes infection developed during the 1st year in 5 patients (9%) in group 1 and in 11 patients (46%) in group 2 (p < 0.05). The actuarial rates of freedom from herpes infection at 1, 6 and 12 months after transplantation were 100%, 98% +/- 2% and 95% +/- 3%, respectively, in group 1 and 82% +/- 7%, 58% +/- 11%, 53% +/- 11% in group 2. All viral infections were cutaneous or mucosal, except for one, which developed in a patient with pneumonia. All infections responded well to treatment, although one patient with an infected cornea was left with a permanent visual deficit. The authors conclude that prophylaxis of herpes simplex virus infection with acyclovir administered orally in the early postoperative period is effective in preventing viral infections during the 1st year after cardiac transplantation.

Acyclovir↗
PubMed1992

Results of a 4-week head-down tilt with and without LBNP countermeasure: I. Volume regulating hormones.

The volume regulating hormones were studied during a 4-week head-down tilt (CNES HDT) in five subjects with and without (controls) lower body negative pressure (LBNP). LBNP was applied 3 times a day for 3 weeks, 4 times a day for 4 d, and 6 times a day for 3 d the last week. In both groups we observed a significant decrease in body weight (3% in controls, 0.8% in LBNP), a significant increase in plasma renin activity and aldosterone (with an amplification of their rhythms), and a significant decrease in norepinephrine with no difference between the two groups. The only major hormonal difference was observed for atrial natriuretic factor (ANF), which decreased significantly in the control group and increased in the LBNP group. These results are compared with the improvement in orthostatic tolerance (OT) after HDT in the LBNP group in the same protocol (17). We conclude that many factors could be involved in the improvement of OT. The results suggest that better conservation of plasma volume in the LBNP group might have prevented a decrease in ANF. Whether ANF plays a role in the regulation of baroreceptor reflex with an improvement in OT is currently unknown.

Aldosterone↗
PubMed1991

Low energy direct current ablation in patients with the Wolff-Parkinson-White syndrome: clinical outcome according to accessory pathway location.

Forty-five patients with the Wolff-Parkinson-White syndrome underwent direct current (DC) ablation using a low energy power source (Cardiac Recorders). Anodal shocks of 10-40 joules were given to either a 6 French quadripolar catheter (Bard), a 7 French bipolar contoured catheter (Bard), or a 7 French deflectable catheter with a 4-mm distal electrode (Mansfield). The indifferent electrode consisted of a large patch that was positioned under the left scapula. There were 26 males and 19 females, with a mean age of 34 years (range 9-67). Accessory pathways were located in the left free wall in 30 patients (67%) and were posteroseptal in 15 patients (33%). The shortest ventriculoatrial interval during mapping (89 +/- 21 msec), the mean cumulative amount of energy per patient (322 +/- 283 joules), and the mean CK-MB rise (45 +/- 30 units, normal 0-30 units) were not significantly different between both groups. Ablation was successful in 29/30 patients (97%) with a left free-wall accessory pathway, and in 13/15 patients (87%) with a posteroseptal accessory pathway. All three patients with failure of ablation had multiple accessory pathways, and two of these patients had Ebstein's anomaly. Patients with left free-wall and posteroseptal accessory pathways, respectively, differed significantly in terms of: total session time (4.1 +/- 1 hours vs 5.3 +/- 1.3, p = 0.0001), total procedure time for ablation (2.6 +/- 0.8 hours vs 3.2 +/- 1.2, P = 0.02), and fluoroscopy time (46 +/- 24 min vs 64 +/- 29, P = 0.006). In 13 patients (29%) with a concealed accessory pathway, these variables were not significantly different from patients with overt preexcitation.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1991

Superoxide anion mediates the endothelium-dependent contractions to serotonin by regenerated endothelium.

The endothelium modulates vascular tone by releasing a variety of vasoactive compounds that relax or contract the underlying vascular smooth muscle. We have previously demonstrated that regenerated endothelium exhibits endothelium-dependent hypercontraction to the platelet-derived compound serotonin (or 5-HT). To determine if this hypercontraction is mediated by superoxide anion produced by the endothelium, we performed balloon catheter denudation on the thoracic and abdominal aorta of male Lewis rats. Eight weeks after arterial injury, endothelium-dependent responses to serotonin were examined in tissue bath experiments. Vascular rings (5 mm in length), with and without endothelium, were contracted with norepinephrine and then exposed to serotonin (10(-9) to 3 x 10(-5) mol/L). Vascular rings with regenerated endothelium exhibited hypercontraction to serotonin (251% +/- 25% of initial norepinephrine contraction; p less than 0.05 compared with control rings, 175% +/- 13%). Removal of the endothelium (133% +/- 6%) or treatment with superoxide dismutase (184% +/- 7%), with or without catalase, prevented the endothelium-dependent constrictor effect of the serotonin. Ketanserin suppressed the vasoconstrictor effect of serotonin on control (93% +/- 15%) and regenerated (105% +/- 9%) rings with endothelium, indicating that the serotonin effect is mediated through the 5-HT2-serotonergic receptor. Deferoxamine or heat-inactivated superoxide dismutase did not modify the response. These observations support the hypothesis that superoxide anion is an endothelium-derived contracting factor produced by regenerated endothelium after intimal injury.

Animals↗
PubMed1991

Morbidity and mortality of reoperation for coronary artery bypass grafting: significance of atheromatous vein grafts.

Reoperation ('redo') for coronary artery disease shows a significant increase in morbidity and mortality compared to primary surgery. Some technical approaches have been advocated to decrease myocardial injury, presumably due to coronary artery embolization from atheromatous vein grafts. From 1984 to 1989, 321 'redo' operations were performed at the Montreal Heart Institute. Patients with patent and atherosclerotic vein grafts at preoperative coronary angiography (239 patients) were compared to those with normal or occluded grafts (82 patients). Perioperative myocardial infarction and death rates were 19% and 13%, respectively. They were particularly high among patients with three or more patent and atherosclerotic vein grafts at reoperation (32% and 29%, respectively). Among the 239 patients with patent atherosclerotic grafts, the results of three different surgical techniques were studied retrospectively. A first group of 66 patients had early ligation of patent atheromatous grafts before cardioplegia was administered by antegrade infusion during single aortic clamping for coronary anastomoses, and maintained for the confection of aortic anastomoses. In a second group of 35 patients, early ligation of diseased graft, antegrade cardioplegic delivery, and partial aortic cross clamping for aortic anastomoses of vein grafts was done. In the third group of 138 patients, venous grafts were not interrupted before antegrade cardioplegic infusion and partial aortic cross clamping for aortic anastomoses of vein grafts was used. No significant difference in hospital mortality or perioperative myocardial infarction rate was observed between the three groups of patients. Thus, the modified techniques so far recommended for repeat coronary artery bypass grafting, such as early ligation of patent atherosclerotic grafts, have failed to improve the early results of 'redo' operations.

Adult↗
PubMed1991

[Post-sternotomy mediastinitis: strategy of treatment].

To determine the incidence, the mortality, the risk factors and the most appropriate method for treatment of sternal infections, 9,742 charts were reviewed retrospectively of patients having undergone a sternotomy for cardiac surgery at the Montreal Heart Institute. One hundred and eleven sternal infections (1.1%) were identified: 55 (0.57%) superficial, 56 (0.57%) profound (mediastinitis). The treatment for these profound infections was either debridement, open or closed with drainage irrigation, pectoral flap closure-repair, or epiplooplasty closure. The risk factors for those patients experiencing profound infections were diabetes, obesity, length of the surgical intervention, the time spent in the operating room, and the duration of endotracheal intubation. Eleven of the 111 patients died. The average length of hospitalization were similar for those patients treated by pectoral flap repair and by the epiplooplasty closure. All patients (100%) treated by the epiplooplasty closure developed an epigastric hernia. Six cases of recurrent infection were observed in the group treated by debridement. The average hospital stay was shortened for those patients benefiting from the pectoral flap and epiplooplasty closures. A high incidence of mortality is associated with profound sternal infection. The methods of treatment are various. We recommend as treatment of choice, the pectoral flap closure because there is relatively low risks with this procedure, little to no recurrence of infection, a shorter hospital stay and this procedure does not provoke epigastric hernia.

Adult↗
PubMed1991

Time course and extent of recovery of endothelium-dependent contractions and relaxations after direct arterial injury.

To determine the time course of the return of endothelium-dependent relaxations and contractions during intimal regeneration, we performed balloon endothelial denudation of the thoracic and abdominal aorta of male Lewis rats and examined smooth muscle function and endothelium-dependent responses in vitro at 1, 2, 4, and 8 weeks after aortic injury. At each study interval during endothelial cell regeneration, vascular smooth muscle contracted and relaxed normally to direct stimulation with norepinephrine and sodium nitroprusside. Endothelium-dependent contractions to serotonin returned to normal at 1 week and developed into a hypercontractile response at 8 weeks. Endothelium-dependent relaxations to acetylcholine returned to normal at 8 weeks, but endothelium-dependent relaxations to adenosine diphosphate remained impaired. These experiments demonstrate that regenerating endothelium regains the ability to produce contracting factor before relaxing factor, and it even exhibits potentiated contractile activity 8 weeks after injury. Thus, after direct arterial injury, regenerating endothelium has abnormal endothelium-dependent function that predisposes the vessel to vasospasm and thrombosis.

Acetylcholine↗
PubMed1991

Endothelial cell dysfunction after ischemic arrest and reperfusion: a possible mechanism of myocardial injury during reflow.

To determine the mechanism(s) responsible for decreased coronary flow after global cardiac ischemia and reperfusion, we studied 40 isolated rabbit hearts before and after 30 minutes of normothermic ischemic arrest and reperfusion. In the control group (n = 10) we evaluated the time course of recovery of coronary flow, vascular reactivity, and myocardial function. In experimental groups A (n = 10) and B (n = 10), metabolic control of autoregulation was assessed by plots of myocardial oxygen consumption versus coronary flow generated by incremental increases in heart rate. The slope and intercept of these plots suggested that autoregulation of coronary flow was maintained after ischemia. In group B hearts (n = 10) hyperosmolar reperfusion with mannitol decreased myocardial water by 2% (p less than 0.01) but did not increase coronary flow. Endothelium-dependent function was assessed in group C (n = 10) by the administration of an endothelium-dependent vasodilator (serotonin) and a smooth muscle vasodilator (adenosine). Coronary artery smooth muscle function was comparable in hearts before and after ischemia. However, endothelium-dependent increases in coronary flow to serotonin were significantly impaired after ischemia (p less than 0.01), and this was accompanied by a significant decrease in prostacyclin synthesis by the endothelium (p less than 0.001). Global cardiac ischemia and reperfusion damages coronary artery endothelium, causing increased coronary vasomotor tone; this may be an important mechanism of decreased coronary perfusion and subsequent myocardial injury during reflow.

Animals↗