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Biomedical subjects

S Siu

Publications and source records attributed to S Siu.

At least 19 recordsLinked to original sources
PubMed2003

Pregnancy complicated by heart disease: a review of Canadian experience.

The physiological adaptations to pregnancy can potentially worsen the prognosis in women whose pregnancy is complicated by heart disease. A comprehensive systematic approach to risk identification is desirable. The ability to predict a subgroup of women that are at a particularly increased risk of pregnancy-related complications can enhance the obstetric care we provide to this population. A retrospective review of 276 pregnancies associated with pre-existing heart disease was undertaken in three Toronto teaching institutions. During the course of the pregnancy, 45 (18%) of 252 completed gestations were complicated by adverse cardiovascular events (congestive heart failure, arrhythmia and stroke). Poor maternal functional class or cyanosis, myocardial dysfunction, left heart obstruction, prior arrhythmia and prior cardiac events were predictive of maternal cardiac complications. These predictors were converted into a point score. If a point score was 0, 1 or more than 1, the risk of a given patient running into cardiovascular complication was 3%, 30% and 66%, respectively. The Canadian Prospective Multicenter Study offered the validation of this prediction rule. In this study, 13 centres recruited prospectively 599 patients with completed gestations. Similar factors were identified in their ability to predict adverse cardiac events. In addition, neonatal complications (20% of pregnancies) were associated with poor functional class or cyanosis, left heart obstruction, anticoagulation, smoking and multiple gestation. A sample of this prospective cohort (302 pregnancies) was compared to 572 matched pregnancies with no underlying heart disease. The neonatal complication rate was higher in the study group when compared to controls, 18% versus 7%, respectively. The highest neonatal complication rate (33%) was seen in gravidas with underlying heart disease who had previously identified cardiac risk factors, were at both extremes of reproductive age, had obstetrical risk factors, smoked or received anticoagulants. Both maternal and neonatal morbidity are increased significantly in gravidas with pre-existing heart disease, although mortality is low. Factors that place the mother and the neonate at risk can be identified before pregnancy. This allows informed counselling and development of a patient-specific management plan.

Canada↗
PubMed2003

Portopulmonary hypertension in decompensated cirrhosis with refractory ascites.

BACKGROUND: The prevalence of portopulmonary hypertension (PPHTN) in patients with cirrhosis and refractory ascites is unknown. Its presence may preclude patients from receiving a transjugular intrahepatic portosystemic shunt or liver transplantation as a definitive treatment for their end stage cirrhosis. PURPOSE: To determine the prevalence, possible aetiological factors, and predictive factors for the development of PPHTN in these patients. METHODS: Sixty two patients (53 males, nine females; mean age 54.5 (1.4) years) with biopsy proven cirrhosis and refractory ascites underwent angiographic measurements of pulmonary and splanchnic haemodynamics. Endothelin 1 levels were measured from the pulmonary artery. Forty nine patients underwent radionuclide angiography for measurements of central blood volume, pulmonary vascular, and cardiac chamber volumes. Forty seven patients also underwent two dimensional echocardiography for measurements of cardiac structural and functional parameters. Cardiac output, and systemic and pulmonary vascular resistance were calculated. RESULTS: Ten patients (16.1%) fulfilled the criteria for PPHTN (mean pulmonary artery pressure >/= 25 mm Hg and pulmonary vascular resistance >/= 120 dynxs/cm(5)), with significantly higher mean right atrial (15.4 (1.2) v 7.9 (0.5) mm Hg; p<0.001), and right ventricular pressures (24.7 (1.5) v 14.7 (0.6) mm Hg; p<0.001), and endothelin 1 levels (3.04 (0.40) v 1.98 (0.12) pg/ml; p=0.02). No significant differences in any of the other parameters measured were detected between the two groups. A right atrial pressure of >/= 14 mm Hg had a 83% positive predictive value for the presence of PPHTN. CONCLUSIONS: Portopulmonary hypertension is common in cirrhosis with refractory ascites, possibly due to excess endothelin 1 in the pulmonary circulation. An elevated right atrial pressure >/= 14 mm Hg predicts the presence of PPHTN, which may be helpful in deciding management options in these patients.

Ascites↗
PubMed2001

Right ventricular form and function after percutaneous atrial septal defect device closure.

OBJECTIVES: We sought to assess the right heart's response to percutaneous device closure of moderate sized atrial septal defects (ASDs) in adults over a one-year follow-up period. BACKGROUND: Percutaneous ASD device closure is a safe and effective means of reducing or eliminating interatrial shunting. The response of the adult's right heart to device closure is incompletely understood. METHODS: Forty consecutive patients had 40 device implantations (32 with the CardioSeal implant and 8 with the Amplatzer device). The patients were assessed with echocardiography, chest radiography and electrocardiography before the procedure and at 1, 6 and 12 months. RESULTS: The mean ASD size was 13+/-4 mm, and the device size ranged from 33 to 40 mm for CardioSeal and 12 to 36 mm for Amplatzer. At one month, heart size (49% vs. 46%), four-chamber right ventricular (RV) size (45 vs. 41 mm), paradoxical septal motion (60% vs. 5%), QRS duration (125 vs. 119 ms), PR interval (181 vs. 155 ms) and echocardiographically determined pulmonary artery systolic pressure decreased significantly and was maintained at 12-month follow-up. At six months, right atrial length decreased from 50 to 47 mm. At one year, 29% of patients had persistent RV enlargement. CONCLUSIONS: Right heart morphology undergoes rapid improvement within one month of defect closure, with associated mechanoelectrical benefit. A small number of patients had persistent RV enlargement or pulmonary hypertension, or both, at one year. Our data support the application of transcatheter methods in achieving excellent hemodynamic and anatomic outcomes.

Adult↗
PubMed2001

Aerobic capacity in adults with various congenital heart diseases.

As an increasing number of patients with congenital heart disease reach adulthood, more information is needed regarding outcomes. The first signs of impaired heart function may appear during exercise testing. The aim of the present study was to establish mean values for maximal oxygen uptake in adults with various congenital heart diseases. Patients from 6 major diagnostic groups were identified, including patients with atrial septal defect (ASD, n = 93), transposition of the great arteries corrected with the Mustard procedure (n = 84), congenitally corrected transposition of the great arteries (CCTGA, n = 41), Tetralogy of Fallot (n = 168), Ebstein's anomaly (n = 37), and Modified Fontan procedure (n = 52). Diminished maximal oxygen uptake was found in all diagnostic groups across age compared with healthy subjects. A significant decrease in maximal oxygen uptake with aging was found in those with ASD (p <0.0001), CCTGA (p = 0.01), and Tetralogy of Fallot (p <0.0001). There was no significant decline, however, in Ebstein's anomaly (p = 0.270), Fontan procedure (p = 0.182), and in the Mustard patients (p = 0.188). All patients achieved significantly lower heart rates than predicted (mean for all groups, p <0.0001). Forced vital capacity values (3.51 L, mean SD +/- 1.02) were lower than predicted values (4.10 L, mean SD +/- 0.90, p <0.0001) for all patients groups except those with ASD. Mean values, however, were within the accepted 20% range of variance. This study showed diminished aerobic capacity in all diagnostic groups when compared with a healthy population. The maximal oxygen uptake values across age groups can be used as reference values in patients with similar diagnoses and as the basis for further research.

Adolescent↗
PubMed2001

Cardiopulmonary exercise performance in adult survivors of the Mustard procedure.

Most patients with the Mustard procedure are now adults. To date, however, there have been few reports on resting and exercise hemodynamics in a large population of adults with this circulation. The aim of this study is to describe such parameters in one of the largest and oldest populations of adults with the Mustard procedure. The database of the University of Toronto Congenital Cardiac Centre for Adults was examined to identify 84 adults with the Mustard procedure who have undergone cardiopulmonary exercise tests. Magnetic resonance imaging and echocardiography studies were obtained in order to assess right ventricular size, function and baseline hemodynamics. Patients achieved lower maximum uptake of oxygen, maximal heart rate, forced vital capacity, forced expiratory volume in 1 second, and oxygen saturations at maximal exercise compared to a healthy population. Magnetic resonance imaging showed significantly different right ventricular ejection fractions between patients and controls. There were no effects of operative variables or preoperative hemodynamics on current exercise capacity. Patients after the Mustard procedure have subnormal exercise capacities. Factors such as chronotropic incompetence, peripheral deconditioning, and impaired lung function may be responsible for these results.

Adolescent↗
PubMed2001

Lung function and aerobic capacity in adult patients following modified Fontan procedure.

OBJECTIVE: To examine cardiopulmonary performance in 52 adult patients with a Fontan circulation. DESIGN: Retrospective cohort study. Values of maximum oxygen uptake (VO(2)max), maximum heart rate (HRmax), forced vital capacity (FVC), and forced expiratory volume in one second (FEV(1)) were compared with predictive values for different age groups. Patients were further subdivided into those with a pulmonary artery connection (RA-PA) or right atrium to right ventricle conduit (RA-RV). RESULTS: At late follow up (median 10 years, range 1 to 26 years), patients with Fontan circulation had greatly diminished VO(2)max, HRmax, FVC, and FEV(1) compared with predicted values. Early age at surgery had a positive impact on aerobic capacity. The FEV(1):FVC ratio indicated restrictive lung function. No differences were found with respect to any variable between patients with RA-PA connections and those with RA-RV connections. CONCLUSIONS: Patients with a Fontan circulation have greatly diminished values of aerobic capacity and a restrictive pattern of lung function. Patients with an early surgical procedure obtained higher values of VO(2)max. The theoretical benefits of including the right ventricle in a Fontan circulation were not apparent.

Adult↗
PubMed2001

The Fontan procedure in adults.

SETTING: Tertiary adult congenital cardiac referral centre. DESIGN: Retrospective cross sectional analysis. OBJECTIVES: To report our 20 year experience with adult Fontan operations, and to compare late outcome in patients with single ventricle with definitive aortopulmonary or cavopulmonary shunt palliation. PATIENTS AND MAIN OUTCOME MEASURES: Patients older than 18 years undergoing Fontan operation between 1 January 1982 and 31 December 1998 were identified. Mortality and late outcome were derived from hospital records. These patients were compared with a cohort of 50 adults with single ventricle who had not undergone a Fontan operation. RESULTS: 61 adults, median age 36 years (range 18-47 years), with a median follow up of 10 years (range 0-21 years) were identified. Actuarial survival was 80% at one year, 76% at five years, 72% at 10 years, and 67% at 15 years. Compared with before the Fontan operation, more patients were in New York Heart Association (NYHA) functional class I or II at the latest follow up (80% v 58%, p < 0.001). Systolic ventricular function deteriorated during follow up such that 34% had moderate to severe ventricular dysfunction at the latest follow up compared with 5% before Fontan (p < 0.001). Arrhythmia increased with time (10% before Fontan v 57% after 10 years, p < 0.001). Fontan patients had improved NYHA functional class, ventricular function, atrioventricular regurgitation, and fewer arrhythmias than the non-Fontan group at the latest follow up. CONCLUSION: The Fontan operation in adults has acceptable early and late mortality. Functional class, systolic ventricular function, atrioventricular regurgitation, and arrhythmia deteriorate late after surgery but to a lesser degree than in non-Fontan patients with a single ventricle.

Adolescent↗
PubMed2001

Brain natriuretic peptide: is it a predictor of cardiomyopathy in cirrhosis?

Subtle cardiac abnormalities have been described in patients with cirrhosis. Natriuretic peptide hormones have been reported to be sensitive markers of early cardiac disease. We postulate that plasma levels of N-terminal pro-atrial natriuretic peptide and brain natriuretic peptide could be used as markers of cardiac dysfunction in cirrhosis. The aim of the study was to evaluate the levels of N-terminal pro-atrial natriuretic peptide and brain natriuretic peptide and their relationship with cardiac structure and function in patients with cirrhosis. The study population comprised 36 patients with cirrhosis of mixed aetiologies, but with no cardiac symptoms; 19 of the patients had ascites and 17 did not. The subjects underwent (i) trans-thoracic two-dimensional echocardiography, and (ii) radionuclide angiography for measurements of cardiac structural parameters, diastolic and systolic function. Levels of N-terminal pro-atrial natriuretic peptide and brain natriuretic peptide were also measured. The results were compared with those from eight age- and sex-matched healthy volunteers. Compared with the controls, the baseline mean ejection fraction was increased significantly in both patient groups (P=0.02), together with prolonged deceleration times (P=0.03), left atrial enlargement (P=0.03) and interventricular septal thickening (P=0.02), findings that are compatible with diastolic dysfunction. Levels of N-terminal pro-atrial natriuretic peptide and brain natriuretic peptide were significantly higher in all patients with cirrhosis with ascites (P=0.01 and P=0.05 respectively), but in only some of the pre-ascitic cirrhotic patients, compared with controls. All high levels of brain natriuretic peptide were correlated significantly with septal thickness (P<0.01), left ventricular diameter at the end of diastole (P=0.02) and deceleration time (P<0.01). We conclude that elevated levels of brain natriuretic peptide are related to interventricular septal thickness and the impairment of diastolic function in asymptomatic patients with cirrhosis. Levels of brain natriuretic peptide may prove to be useful as a marker for screening patients with cirrhosis for the presence of cirrhotic cardiomyopathy, and thereby identifying such patients for further investigations.

Adult↗
PubMed1999

Arrhythmia and survival in patients >18 years of age after the mustard procedure for complete transposition of the great arteries.

Increasing numbers of patients who underwent Mustard repair as children are now adults. Loss of sinus rhythm, supraventricular arrhythmias, and sudden death have been described in pediatric series. However, little is known about the clinical course of adult patients. This retrospective cohort study examined 86 consecutive adults (age >18 years) who had undergone the Mustard procedure and were referred to an adult congenital cardiac clinic for ongoing follow-up. The incidence and predictors of arrhythmia, congestive heart failure, and death were determined. The median follow-up period was 8 years after age 18 or 23 years after Mustard repair. There were 8 deaths (9%), 2 were sudden. Congestive heart failure (CHF) requiring hospital admission occurred in 9 patients (10%). Pulmonary hypertension and systemic ventricular dysfunction were independent risk factors for death or CHF. Only 29 patients (34%) remained arrhythmia-free. Forty-one patients (48%) had at least 1 episode of supraventricular tachycardia (SVT), with most patients (30, 73%) having atrial flutter. SVT after the age of 18 was associated with CHF. Pulmonary hypertension, systemic ventricular dysfunction, and junctional rhythm before age 18 were independent risk factors for SVT. Pacemakers were implanted in 19 patients (22%); 13 of those were beyond age 18. Thus, adult survivors of the Mustard procedure continue to be at risk for premature death, CHF and supraventricular tachyarrhythmia.

Adolescent↗
PubMed1999

High treatment-related mortality in cardiac amyloid patients undergoing autologous stem cell transplant.

Dose-intensive chemotherapy with PBSC support was recently reported to be feasible in cardiac amyloidosis with some patients achieving post-transplant improvement in performance status. At our center, 11 patients with symptomatic primary systemic amyloidosis and predominant cardiac involvement confirmed by biopsy or increased wall thickness on echocardiogram were evaluated for high-dose therapy. The average time from diagnosis to referral was 11 months (4-26 months). Of the 11 patients, two were not candidates for high-dose therapy, based on poor performance status. The remaining nine patients proceeded to PBSC collection. Three patients died during the mobilization period: two of rapid atrial fibrillation, and the third secondary to progressive heart failure. Six patients proceeded to transplantation. However, one died of sudden cardiac arrest the day of melphalan administration, one following hypotension related to stem cell infusion, and one of hypotensive shock the day following stem cell infusion. Three patients recovered and left the hospital, but one died of a cardiorespiratory event at home within 6 weeks of discharge. Both surviving patients demonstrate objective improvement. A decision to use high-dose therapy and stem cell support in cardiac amyloidosis must balance the substantial morbidity of the procedure with the potential benefits. Transplant regimens should avoid cardiotoxic agents such as cyclophosphamide and DMSO and patients should receive anti-arrythmic therapy.

Amyloidosis↗
PubMed1999

Pneumocystis carinii pneumonia in patients receiving immunosuppressive drugs for dermatological diseases.

In recent years, Pneumocystis carinii pneumonia (PCP) has been increasingly reported in patients without human immunodeficiency virus (HIV) infection. The increased occurrence of PCP in non-HIV-immunocompromised subjects has been attributed to several factors: use of stronger immunosuppressive regimens, higher awareness of PCP, advanced diagnostic technology and nosocomial spread of P. carinii. Appearance of PCP subsequent to the use of immunosuppressive drugs has been noticed in many inflammatory diseases such as rheumatoid arthritis, systemic lupus erythematosus and ulcerative colitis. Dermatologists frequently use immunomodulating agents, but the occurrence of PCP in patients receiving immunosuppressive drugs for skin diseases is largely unknown. We report four cases where PCP appeared following the use of immunosuppressive drugs primarily for cutaneous diseases, namely pemphigus, cutaneous necrotizing vasculitis (two cases) and Behçet's syndrome. These cases were identified in a computerized database study (1979-95) to evaluate the occurrence of PCP among immunocompromised hosts without HIV infection.

Behcet Syndrome↗
PubMed1998

Incidence of latex sensitization among latex glove users.

BACKGROUND: Although there are several reports of the prevalence of latex sensitization among health care workers, the incidence of sensitization is unknown. OBJECTIVE: The objective of this study was to estimate the incidence of sensitization among latex glove users at a hospital in Hamilton, Ontario, Canada. METHODS: Workers with negative results to the skin test at baseline were followed prospectively over 1 year, some wearing powdered gloves and others using powder-free gloves. They were reevaluated in 1995 with a questionnaire and skin prick test (SPT) sensitivity to latex reagents, three common inhalants, and six foods. A conversion was defined as a (new) latex SPT with wheal diameter at least 4 mm greater than saline control. Glove extracts were assayed for antigenic protein, and air samples were obtained to estimate exposure to airborne latex protein. RESULTS: During powdered glove use, personal exposures ranged from 5 to 616 ng/m3, whereas during powder-free glove use, all but two results for air samples were below the limit of detection (about 0.1 ng/m3). During the study period, the protein concentration in the powdered gloves, initially mean 557 microg/gm of sample, declined at a rate of 295 microg/gm per year (p < 0.0001). Of the 1075 SPT-negative participants at baseline, 479 were working in eligible wards, and of these, 435 (91%) participated in follow-up, 227 using powder-free gloves and 208 using powdered gloves. We identified four conversions, two (1.0%) in the powdered glove group and two (0.9%) in the powder-free group. The two participants using powdered gloves were the only converters who were symptomatic. The significance of skin test conversions identified in the powder-free group, both asymptomatic patients, is unclear. The limitations of the study are discussed, including the limited power, the declines in latex protein concentrations, and the possibility of information (observer) bias. CONCLUSION: To our knowledge, this represents the first reported estimate (about 1%) of incidence of sensitization in hospital personnel using latex gloves.

Cross-Sectional Studies↗
PubMed1998

A bedside clinical prediction rule for detecting moderate or severe aortic stenosis.

OBJECTIVE: To evaluate a bedside clinical prediction rule for detecting moderate or severe aortic stenosis. DESIGN: Cross-sectional study with independent comparison to a diagnostic reference standard, doppler echocardiography. SETTING: Urban university hospital. PARTICIPANTS: Consecutive hospital inpatients (n = 124) who had been referred for echocardiography. MEASUREMENTS AND MAIN RESULTS: Participants were examined by a third-year general internal medicine resident and a staff general internist. We hypothesized in advance that absence of a murmur over the right clavicle would rule out aortic stenosis, while the presence of three or four associated findings (slow carotid artery upstroke, reduced carotid artery volume, maximal murmur intensity at the second right intercostal space, and reduced intensity of the second heart sound) would rule in aortic stenosis. Study physicians were unaware of echocardiographic findings. The outcome was echocardiographic moderate or severe aortic stenosis, defined as a valve area of 1.2 cm2 or less, or a peak instantaneous gradient of 25 mm Hg or greater. Absence of a murmur over the right clavicle ruled out aortic stenosis (likelihood ratio [LR] 0.10; 95% confidence interval [CI] 0.01, 0.44). The presence of three or four associated findings ruled in aortic stenosis (LR 40; 95% CI 6.6, 240). If a murmur was present over the right clavicle, but no more than two associated findings were present, then the examination was indeterminate (LR 1.8; 95% CI 0.93, 2.9). CONCLUSION: A clinical prediction rule, using simple bedside maneuvers, accurately ruled in and ruled out aortic stenosis.

Adult↗