Biomedical subjects
Publications and source records attributed to Michel Carrier.
Aspergillus endocarditis is an ominous condition whose prevalence is increasing in the hospital population. Despite the life-threatening nature of the disease, detection of the source, establishment of the diagnosis, and treatment remain highly challenging. A cluster of three cases of Aspergillus endocarditis recently encountered at the Montreal Heart Institute are presented.
BACKGROUND: Hypertrophic cardiomyopathy is a rare indication for cardiac transplantation, with only anecdotal reports in the literature. Transplantation has been proposed to patients with hypertrophic cardiomyopathy who remained symptomatic despite optimal medical treatment or who progressed to congestive heart failure, and when conventional surgical correction was not or was no longer possible. In this report, we analyze the clinical results of cardiac transplantation in these patients. METHODS: We retrospectively reviewed complete clinical data and prospectively gathered complete follow-up data for 14 patients who underwent orthotopic cardiac transplantation for hypertrophic cardiomyopathy at the Montreal Heart Institute and Ste-Justine Hospital between 1984 and 2001. RESULTS: Ten male (71.4%, 5 adults and 5 children) and 4 female (28.6%, 2 adults and 2 children) patients underwent heart transplantation for hypertrophic cardiomyopathy. The median age of the recipients in the pediatric group was 13 years (range, 6-16) and was 40 years (range, 22-46) in the adult group. Median duration of follow-up was 9.5 years (mean, 8.8 +/- 4.8 years; range, 1-18) and was 100% complete. We found no operative mortality and found 2 late deaths related to coronary graft atherosclerosis. Long-term survival at 5, 10, and 15 years was 100%, 85%, and 64%, respectively. Freedom from acute rejection at 1, 5, and 10 years was 73%, 32%, and 9%, respectively. The remaining 11 survivors exhibit few symptoms and are currently in New York Heart Association Class I or II. CONCLUSIONS: Cardiac transplantation is a valid therapeutic option for patients with symptomatic hypertrophic cardiomyopathy who do not respond to optimal medical management and who are not candidates for conventional surgical treatment. The long-term outcome is excellent in these patients.
OBJECTIVES: To compare hemodynamic and echocardiographic indexes of left ventricular performance. DESIGN: Retrospective database analysis of four clinical trials. SETTING: University hospital. PATIENTS: Cardiac surgery patients. INTERVENTION: Left ventricular performance was evaluated using left ventricular stroke work index (LVSWI) calculated from the pulmonary artery catheter and both fractional area change and regional wall motion score index (RWMSI) measured from transesophageal echocardiography. Measures of left ventricular performance were obtained before and after bypass (group 1, n = 30), during acute increase and decrease in preload (group 2, n = 14), after administration of inhaled prostacyclin or placebo in patients with pulmonary hypertension (group 3, n = 20), and in hemodynamically unstable patients in the intensive care unit at admission and at 2 and 4 hrs (group 4, n = 20). MAIN RESULTS: A total of 186 simultaneous LVSWI, fractional area change, and RWMSI were analyzed and compared. Patients with RWMSI <1.3 had a LVSWI of 23.4 +/- 10.3 g.m.m compared with 18.4 +/- 7.2 g.m.m in those with RWMSI >1.3 (p =.0349). Subdividing fractional area change into three different groups (> or =50%, 25% to 49%, and < or =24%), the corresponding values of LVSWI were 22.3 +/- 9.7 g.m.m, 22.2 +/- 10.8 g.m.m, and 17.7 +/- 5.5 g.m.m, respectively (p =.5114). Correlations between LVSWI and RWMSI changes ranged from -0.28 to 0.16 (p values from.31 to.94). Correlations between LVSWI and fractional area change changes ranged from -0.62 to 0.22 (p values from.07 to.95). CONCLUSION: There is a significant discrepancy and limited relationship between the hemodynamic and echocardiographic evaluation of left ventricular performance.
In October of 2002, a workshop was held as part of the Canadian Cardiovascular Congress in Edmonton, Canada, entitled "Under-Utilization of Mechanical Circulatory Support in Canada. Why and What Can Be Done?" The workshop examined various issues related to the use of mechanical circulatory support devices in the Canadian context. Representatives from all Canadian centers with active mechanical circulatory support programs were invited to participate and participants included surgeons and cardiologists, as well as other affiliated health professionals. Opinions were solicited from the workshop participants and a series of recommendations were formulated.
BACKGROUND: The Thoratec left ventricular assist device (LVAD; Thoratec Laboratories Corporation, USA) was used as a bridge to transplantation at the Montreal Heart Institute. LVAD patients were activated on the waiting list as soon as they were in suitable clinical status. OBJECTIVE: To analyze the effect of introducing the Thoratec LVAD in the heart transplantation program at the Montreal Heart Institute. METHODS: The results of 16 LVAD patients and 20 patients who underwent heart transplantation without LVAD support between January 2000 and February 2002 were reviewed. RESULTS: Sixteen patients in cardiogenic shock underwent emergency implantation of a Thoratec LVAD following acute myocardial infarction (five patients), acute viral cardiomyopathy (five patients), idiopathic cardiomyopathy (three patients), postpartum cardiomyopathy (two patients) and failure to wean from cardiopulmonary bypass (one patient). Thirteen of 16 (81%) LVAD patients underwent heart transplantation, and three LVAD patients were not listed and died from multiorgan failure. The wait for transplantation averaged 17+/-19 days in LVAD patients compared with 87+/-66 days for the 20 patients undergoing transplantation without LVAD support (P=0.01). Survival 12 months following transplantation averaged 84+/-10% in LVAD supported patients and 90+/-7% in those without LVAD support (P=0.6). CONCLUSION: The use of Thoratec LVAD as a bridge to transplantation did not prolong the wait for a donor of patients without LVAD support (United Network Organ Sharing status II). Moreover, listing patients as soon as they appear suitable for transplantation resulted in a short period of LVAD support and a good rate of survival one year after transplantation.
BACKGROUND AND AIM OF THE STUDY: Tricuspid regurgitation secondary to pulmonary hypertension due to left-sided heart valve lesions is common. Here, the results are reported of 25 years' experience with three surgical techniques; the De Vega semicircular annuloplasty, the Bex flexible linear reducer, and the Carpentier-Edwards prosthetic ring annuloplasty. METHODS: Between 1976 and 2002, 463 patients underwent 478 tricuspid annuloplasty procedures to correct valve regurgitation during associated left-sided valve surgery. Patients were followed prospectively at the Montreal Heart Institute Valve Clinic. RESULTS: A total of 107 patients (23%) underwent the De Vega semicircular annuloplasty, 267 (58%) the Bex flexible linear reducer, and 89 (19%) the Carpentier-Edwards prosthetic ring annuloplasty. Excluding 30-day mortality, the mean 5-, 10- and 15-year patient survival was 82+/-4%, 58+/-6% and 30+/-6% respectively after the De Vega semicircular annuloplasty, 76+/-3%, 54+/-4% and 36+/-6% respectively after the Bex flexible linear reducer, and the mean five-year patient survival was 88+/-4% after the Carpentier-Edwards prosthetic ring annuloplasty (p = 0.65, for comparison of the three survival curves). The mean freedom rate from tricuspid repair failure (clinical right heart failure, redo annuloplasty, tricuspid valve replacement at follow up) was 95+/-3%, 93+/-3% and 72+/-8% at 5, 10 and 15 years respectively after the De Vega semicircular annuloplasty, and 97+/-1%, 87+/-4% and 66+/-9% after the Bex flexible linear reducer. The mean freedom rate from repair failure was 94+/-3% at five years after the Carpentier-Edwards prosthetic ring annuloplasty (p = 0.18 for comparison of the three freedom from failure curves). CONCLUSION: All three techniques of tricuspid valve repair resulted in a low rate of failure, and in good patient survival at long-term follow up.
BACKGROUND: Patients with diabetes constitute a high-risk population for myocardial revascularization due to extensive coronary disease. OBJECTIVE: To compare the early postoperative outcomes of patients with diabetes undergoing off-pump or on-pump coronary artery bypass surgery. METHODS AND RESULTS: Over a four-year period (1995 to 1998), 885 diabetics were operated for primary isolated coronary bypass; 156 patients had off-pump and 729 had on-pump coronary artery bypass surgery. Patients in the off-pump group were significantly older, had a higher incidence of hypertension and renal failure, and received fewer distal anastomoses (2.7 versus 2.9, P=0.004). Postoperative myocardial infarction, reintubation and postoperative use of intra-aortic balloon pump occurred significantly more frequently in the off-pump group (10.3% versus 5.5%, P=0.04; 8.3% versus 3.6%, P=0.03; 7.7% versus 1.5%, P=0.0001, respectively). Multivariate analysis revealed that type of surgery was an independent predictor of these complications, which occurred 1.9, 2.7 and 7.9 times more often, respectively, in the off-pump group. The 30-day mortality rate was not significantly different between the groups. CONCLUSIONS: Off-pump coronary artery bypass surgery is associated with an increased early postoperative morbidity in patients with diabetes and, thus, should be used with caution.
OBJECTIVE: Pressure measurements at the level of the right atrium are commonly used in clinical anesthesia and the intensive care unit (ICU). There is growing interest in the use of peripheral venous sites for estimating central venous pressure (CVP). This study compared bias, precision, and covariance in simultaneous measurements of CVP and of peripheral venous pressure (PVP) in patients with various hemodynamic conditions. DESIGN AND SETTING: Operating room and ICU of a tertiary care university-affiliated hospital. PATIENTS: Nineteen elective cardiac surgery patients requiring cardiopulmonary bypass were studied. INTERVENTIONS: A PVP catheter was placed in the antecubital vein and connected to the transducer of the pulmonary artery catheter with a T connector. Data were acquired at different times during cardiac surgery and in the ICU. MEASUREMENTS AND RESULTS: A total of 188 measurements in 19 patients were obtained under various hemodynamic conditions which included before and after the introduction of mechanical ventilation, following the induction of anesthesia, fluid infusion, application of positive end expiratory pressure and administration of nitroglycerin. PVP and CVP values were correlated and were interchangeable, with a bias of the PVP between -0.72 and 0 mmHg compared to the CVP. CONCLUSIONS: PVP monitoring can accurately estimate CVP under various conditions encountered in the operating room and in the ICU.
OBJECTIVE: Endothelium-dependent G-protein mediated relaxations of epicardial coronary arteries is impaired with left ventricular hypertrophy. The objective of this study was to assess the effect of L-arginine, BH(4) and the combination of two antioxidants, superoxide dismutase and catalase, on endothelium-dependent relaxations in a swine left ventricular hypertrophy model. METHODS: Aortic banding was performed 3 cm above the coronary ostia. Vascular reactivity studies were performed in standard organ chamber experiments to assess the NO pathway in the presence of methyltetrahydropterin (a BH(4) analogue), L-arginine, superoxide dismutase and catalase. RESULTS: There was a statistically significant increase in endothelium-dependent relaxation to serotonin and to bradykinin with methyltetrahydropterin and with superoxide dismutase plus catalase (P<0.05) but not with L-arginine compared to untreated coronary arteries from left ventricular hypertrophy animals. Plasma 3-nitrotyrosine level increased significantly from 918+/-122 to 1844+/-300 microM (P<0.05 vs. control) after 60 days of aortic banding. Endothelial dysfunction was not associated with a reduced expression of endothelial nitric oxide synthase 2 months after pressure overload left ventricular hypertrophy. CONCLUSIONS: Treatment with BH(4) and antioxidants constitutes an interesting approach for the prevention of endothelial dysfunction in epicardial coronary arteries associated with left ventricular hypertrophy.
PURPOSE: Magnesium potentiates the effect of nondepolarizing neuromuscular blocking agents. It is used in cardiac anesthesia to prevent hypertension and arrhythmias. This study was performed to measure the interaction between magnesium and cisatracurium in cardiac surgery. METHODS: Twenty patients scheduled for elective cardiac surgery were randomly assigned to receive magnesium sulfate (70 mg x kg(-1) at induction followed by 30 mg x kg(-1) x hr(-1)) or placebo. The ulnar nerve was stimulated and the electromyographic response of the adductor pollicis was measured. Cisatracurium 0.1 mg x kg(-1) was given at induction, followed by 0.05 mg x kg(-1) when the first twitch in the train-of-four reached 25%. RESULTS: Ionized magnesium was 1.32 +/- 0.24 mmol x L(-1) in the treatment group vs 0.47 +/- 0.4 mmol x L(-1) in the control group. Duration of action of the intubating dose was longer in the magnesium group (74 +/- 20 min) than in the placebo group (42 +/- 6 min, P = 0.0001). Duration of the first maintenance dose was 69 +/- 16 min in the magnesium group vs 35 +/- 7 min in the placebo group (P = 0.0001). Total dose of cisatracurium administered throughout surgery was 0.19 +/- 0.07 mg x kg(-1) in the magnesium group compared with 0.29 +/- 0.01 mg x kg(-1) in the placebo group (P = 0.017). Hemodynamic variables and temperature were similar in both groups. CONCLUSION: In patients undergoing cardiac surgery, administration of magnesium sulfate, resulting in ionized levels of 1.3 mmol x L(-1), results in a 30-35 min prolongation of the neuromuscular blockade induced with intubating and maintenance doses of cisatracurium and does not alter hemodynamic stability.
BACKGROUND: Tricuspid valve replacement is seldom used in clinical practice, but the choice between mechanical and biologic prostheses remains controversial. METHODS: Between 1977 and 2002, 97 patients underwent tricuspid valve replacement and were followed at the Montreal Heart Institute Valve Clinic. Patients underwent replacement with bioprostheses (n = 82) and mechanical valves (n = 15). RESULTS: Patients with bioprosthetic tricuspid replacements averaged 53 +/- 13 years of age compared with 48 +/- 11 years in those with tricuspid mechanical valve replacements (p = 0.2). Isolated tricuspid valve replacement was performed in 11 patients (73%) in the mechanical valve group compared with 31 patients (38%. p = 0.01) in the bioprosthetic replacement group. In patients undergoing bioprosthetic tricuspid replacement, 51 (62%) underwent multiple associated valve replacements. The 5-year survival after tricuspid replacement averaged 60% +/- 13% in the mechanical valve group and 56% +/- 6% in the biologic replacement group (p = 0.8). The 5-year freedom rate from tricuspid valve reoperation averaged 91% +/- 9% in patients with mechanical valves and 97% +/- 3% in those with biologic valves (p = 0.2). CONCLUSIONS; Patient survival after tricuspid valve replacement is suboptimal but related to the clinical condition at operation. The use of biologic prostheses for tricuspid valve replacement remains a good option in young patients because of limited life expectancy unrelated to the type of tricuspid prostheses at long-term follow-up.
BACKGROUND: Radial artery infections secondary to catheterization for blood pressure monitoring are rare but potentially serious complications. The objective of the study was to evaluate the incidence, the risk factors and the evolution of radial artery infections following cardiac surgery. METHODS: A retrospective review of 8300 patients undergoing cardiac surgery between 1998 and 2002 at the Montreal Heart Institute (MHI) was undertaken. All patients with superficial radial artery infections, infected radial artery pseudoaneurysms, and arterial catheter-related bacteremia were considered using prospective global surveillance of all nosocomial infections over the study period by an infection control nurse. RESULTS: Thirteen patients with radial infections were encountered (0.2%) with bacteremia occurring in 9 patients (0.15%). Five patients developed infected radial artery pseudoaneurysms (0.05%) and 5 patients developed subsequent sternal wound infections. Two patients died in their early postoperative evolution. Mean patient age was 67 years old and mean duration of cannulation was 5.8 days. Only 1 patient had diabetes. Seven of 13 patients were positive for Staphylococcus aureus (54%). All patients had undergone cardiopulmonary bypass (CPB) for various procedures. All superficial infections responded well to antibiotic therapy. Early surgical intervention is essential in cases of infected radial artery pseudoaneurysms. CONCLUSIONS: The postoperative state and cardiopulmonary bypass put patients at risk for infectious complications. Strict systematic changing of arterial lines on a timely basis is unwarranted in our opinion. A high suspicion index, aggressive surgical treatment of bacterial arteritis and appropriate intravenous antibiotics are essential to improve the prognosis.
OBJECTIVES: Surgical radiofrequency ablation is increasingly used during open heart surgery for the treatment of chronic atrial fibrillation. The purpose of this study was to determine the effects of application of radiofrequency on coronary endothelial function and structure and establish the relationship between coronary lesions and distance of radiofrequency application. METHODS: Six Landrace swine (25.9+/-2.0 kg) were included in the study. With the heart kept beating, three epicardial radiofrequency lesions (20 W, 20 s duration, 60 degrees C) 2 cm in length each, were created 1, 5 and 10 mm away from the left anterior descending and the right coronary arteries. The circumflex artery served as control. Coronary rings were placed in organ chambers. After contraction to KCl and prostaglandin F2alpha, endothelium-dependent relaxations to bradykinin were studied. Gomori trichrome and hematoxylin-eosin safran staining were used for histological evaluation. RESULTS: Exposure to radiofrequency 1 mm from the coronary arteries caused a significant decrease in endothelium-independent contractions to KCl and endothelium-dependent relaxations to bradykinin compared to controls (P<0.05). No significant decrease of endothelium-dependent relaxations occurred for rings exposed to radiofrequency at a distance of 5 and 10 mm, compared to controls. Histological examination showed endothelial disruption and medial smooth muscle cells at different stages of necrosis up to 5 mm from the radiofrequency application site. CONCLUSIONS: Radiofrequency may induce coronary endothelial functional and morphological damages when applied less than 5 mm from the artery. Caution must be exerted during left atrial radiofrequency application due to the proximity of the circumflex artery.
OBJECTIVE: The incidence of heparin-induced thrombocytopenia is increasing, and the thrombin inhibitor danaparoid could be a useful alternative. The objective of the present study was to compare danaparoid and heparin in patients undergoing off-pump coronary artery bypass grafting. METHODS: In a prospective, randomized, double-blind clinical trial comparing heparin (bolus of 1 mg/kg) with danaparoid (bolus of 40 U/kg), 71 patients underwent off-pump coronary artery bypass grafting with one of the study drugs. The amount of blood lost, the number of homologous blood products transfused, the troponin T levels, and the amount of anti-Xa activity were monitored. RESULTS: Thirty-four patients underwent 2.6 +/- 0.7 bypasses with danaparoid, and 37 patients underwent 2.5 +/- 0.9 grafts with heparin (P =.8). Postoperative blood losses averaged 1394 +/- 1033 mL in patients receiving danaparoid and 1130 +/- 868 mL in patients receiving heparin (P =.2). The number of homologous blood products transfused averaged 3.6 +/- 7 units in patients receiving danaparoid and 1.9 +/- 4.4 units in patients receiving heparin (P =.2). The number of patients requiring homologous blood transfusion was higher in patients receiving danaparoid (18/34 [53%]) than in patients receiving heparin (10/37 [27%], P =.03). Serum anti-Xa activity averaged 1.6 +/- 0.6 U/mL in patients receiving danaparoid and 1.9 +/- 0.8 U/mL in patients receiving heparin 30 minutes after injection of the drugs (P =.1) and 0.3 +/- 0.1 and 0.04 +/- 0.08 U/mL, respectively, 12 hours after coronary artery bypass grafting (P =.001). Troponin serum levels were similar 48 hours after coronary artery bypass grafting (0.5 +/- 0.6 and 0.4 +/- 0.6 microg/L, respectively). CONCLUSION: Although off-pump coronary artery bypass grafting with danaparoid versus heparin increases the number of patients exposed to homologous blood transfusion (relative risk, 2; 95% confidence limits, 1-4), off-pump coronary artery bypass grafting with danaparoid is a valuable alternative to heparin in patients with thrombocytopenia requiring surgical intervention.
Coronary endothelial dysfunction in left ventricular hypertrophy (LVH) can reduce myocardial perfusion and result in an impaired global LV function. The objective of this study was to characterize the specific alterations of endothelial signal transduction of coronary arteries in a swine LVH model. Aortic banding was performed 3 cm above the coronary ostia. Vascular reactivity studies were performed to assess the nitric oxide (NO) and the EDHF-mediated relaxations. There was a significant increase in LV/body weight ratio associated with an increased in LV diastolic and end-diastolic pressure and decrease in dP/dT (P < 0.05), with no significant difference in coronary pressures 60 days after pressure-overload LVH. There was a significant decrease in endothelium-dependent relaxations to serotonin (5-HT) and to bradykinin (BK) (P < 0.05 for both) from LVH animals. There was no significant decrease of relaxations in the presence of BK and Nomega-l-arginine (EDHF pathway). Plasma NO(x) levels decreased significantly from 1.8% +/- 0.2% to 1.2% +/- 0.1% (P < 0.05 versus control). Chronic pressure-overload LVH is associated with an endothelial dysfunction involving both Gi and Gq protein-mediated relaxations in coronary arteries as well as the EDHF pathway.
BACKGROUND: A new penetrating stapled anastomotic system using nitinol microclips (Coalescent Surgical U-Clip) has been developed to facilitate the construction of compliant interrupted sutures for minimally invasive and robotic surgery as well as for conventional procedures. The purpose of this study was to determine the effect of nitinol U-Clips used for coronary anastomosis in the development of endothelial dysfunction, compared with conventional running sutures. METHODS: In a porcine model, both internal thoracic arteries were harvested, and the heart was removed. In a Krebs solution, 2 anastomoses were realized ex vivo between internal thoracic arteries and the left anterior descending artery. One was carried out with 12 Coalescent microclips, and the other used conventional running 7-0 polypropylene suture material (Prolene). Coronary rings on the anastomotic sites were then placed in organ chambers filled with oxygenated Krebs solution. Vascular reactivity studies were performed in standard organ chamber experiments. After the contraction of the coronary arteries in response to prostaglandin F2alpha, the endothelium-dependent relaxation response to bradykinin was studied. The other coronary arteries served as controls. RESULTS: There was no statistically significant difference among the groups (P >.05) in the amplitude of the contraction response to KCl and prostaglandin F2alpha. There were no statistically significant differences in endothelium-dependent relaxation response to bradykinin between the nitinol microclip group and controls, between the suture group and controls, and between the nitinol microclip and suture groups. CONCLUSIONS: Coalescent nitinol U-Clips used as anastomotic devices do not induce an endothelial dysfunction and allow a compliant anastomosis under satisfactory conditions.
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OBJECTIVE: The insertion of intracoronary shunts during off-pump coronary artery bypass surgery may induce severe endothelial dysfunction in the target arteries. The purpose of this study was to determine the role of the ratio of the shunt diameter to the target artery diameter in the development of endothelial dysfunction and to develop guidelines for selecting the most appropriate shunt size. METHODS: Nine swine (25 +/- 4 kg) were used for this study. Three ClearView shunts 3 mm, 2 mm, and 1.25 mm in diameter were inserted proximally to distally via 3 arteriotomies into the right coronary artery to obtain oversizing with the 3-mm shunt, undersizing with the 1.25-mm shunt, and a satisfying congruence with the 2-mm shunt. The shunts were left in place for 15 minutes, and the levels of bleeding were quantified. Coronary rings upstream and downstream from the arteriotomies were then harvested and placed in organ chambers to study endothelium-dependent relaxations to serotonin and bradykinin. Noninstrumented coronary arteries served as controls. RESULTS: A decrease of endothelium-dependent relaxation occurred with the 3-mm shunts (P <.005), which were associated with an adequate hemostasis. A decrease of endotheliumdependent relaxation occurred with the 2-mm shunts (P <.05), which were associated with intermittent bleeding, and no significant decrease of endothelium-dependent relaxation occurred with 1.25-mm shunts (P >.05), which were associated with continuous bleeding. CONCLUSIONS: Intracoronary shunts are associated with different disadvantages, depending on the mismatch to the target coronary artery, and whatever their size, shunts are not the ideal device for safely obtaining a satisfactory hemostasis. These results support our clinical attitude of the selective use of intracoronary shunts.