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Biomedical subjects

Samuel S Lee

Publications and source records attributed to Samuel S Lee.

At least 19 recordsLinked to original sources
PubMed2007

Cardiac dysfunction in cirrhosis.

Cirrhosis is known to be associated with numerous cardiovascular abnormalities. These include increased cardiac output and decreased arterial pressure and total peripheral resistance. Despite this increased baseline cardiac output, patients with cirrhosis show an attenuated systolic and diastolic function in the face of pharmacological, physiological and surgical stresses, as well as cardiac electrical abnormalities such as QT prolongation. These abnormalities have been termed cirrhotic cardiomyopathy. The pathogenic mechanisms that underlie this syndrome include impairment of the beta-adrenergic receptor signalling, cardiomyocyte plasma membrane function, intracellular calcium kinetics, and humoral factors such as endogenous cannabinoids, nitric oxide and carbon monoxide. Cirrhotic cardiomyopathy is believed to contribute to the cardiac dysfunction that can be observed in patients with transjugular intrahepatic portosystemic stent-shunt insertion and liver transplantation. Insufficient cardiac contractile function may also play a role in the pathogenesis of hepatorenal syndrome precipitated by spontaneous bacterial peritonitis. In this review, the clinical features, pathogenic mechanisms, clinical consequences and management options for cirrhotic cardiomyopathy are discussed.

Cardiomyopathies↗
PubMed2006

Chronic hepatitis B--who should be treated?

Hepatitis B virus (HBV) can cause both acute and chronic infection and is an important human pathogen, with an estimated 350 million individuals chronically infected worldwide. HBV carriers are at risk for the development of cirrhosis and hepatocellular carcinoma (HCC), and patients with chronic infection require life-long monitoring. Effective hepatitis B antiviral treatment is important given the significant associated global morbidity and mortality from liver-related complications. The goals of treatment are to achieve sustained suppression of HBV replication and remission of liver disease. In the past decade, great progress has been made in the treatment of chronic HBV infection. Interferon alfa, longer-acting pegylated interferon, and nucleos(t)ide analogs such as lamivudine, adefovir dipivoxil, and entecavir are currently available for treatment of HBV infection. Effective treatment decisions require an understanding of the natural history of hepatitis B and the range of treatment options. This review includes criteria for determining when and how to most effectively intervene with antiviral therapy for chronically infected patients.

Antiviral Agents↗
PubMed2006

Hepatitis C: a review for primary care physicians.

Primary care physicians see many of the estimated 250 000 Canadians chronically infected with the hepatitis C virus (HCV). Of this number, about one-third are unaware they are infected, which constitutes a large hidden epidemic. They continue to spread HCV unknowingly and cannot benefit from advances in antiviral therapy that may clear them of the virus. Many HCV-infected people remain asymptomatic, which means it is important to assess for risk factors and test patients accordingly. The third-generation enzyme immunoassay for HCV antibodies is a sensitive and specific test, although the presence of the virus can be confirmed by polymerase chain reaction testing for HCV RNA in some circumstances. Pegylated interferon-alpha and ribavirin combination therapy clears the virus in about 45%-80% of patients, depending on viral genotype. Preventive strategies and counselling recommendations are also reviewed.

HIV Infections↗
PubMed2006

Cardiac and vascular changes in cirrhosis: pathogenic mechanisms.

Cardiovascular abnormalities accompany both portal hypertension and cirrhosis. These consist of hyperdynamic circulation, defined as reduced mean arterial pressure and systemic vascular resistance, and increased cardiac output. Despite the baseline increased cardiac output, ventricular inotropic and chronotropic responses to stimuli are blunted, a condition known as cirrhotic cardiomyopathy. Both conditions may play an initiating or aggravating pathogenic role in many of the complications of liver failure or portal hypertension including ascites, variceal bleeding, hepatorenal syndrome and increased postoperative mortality after major surgery or liver transplantation. This review briefly examines the major mechanisms that may underlie these cardiovascular abnormalities, concentrating on nitric oxide, endogenous cannabinoids, central neural activation and adrenergic receptor changes. Future work should address the complex interrelationships between these systems.

Blood Circulation↗
PubMed2006

A double-blind placebo-controlled study of emtricitabine in chronic hepatitis B.

BACKGROUND: Emtricitabine is a nucleoside analogue approved for treatment of human immunodeficiency virus 1 with clinical activity against hepatitis B virus (HBV). METHODS: To compare the safety and efficacy of emtricitabine with placebo in patients with HBV, we conducted a randomized (2:1), double-blind study at 34 sites in North America, Asia, and Europe that enrolled adults between November 2000 and July 2002 who had chronic HBV infection but had never been exposed to nucleoside or nucleotide treatment. Each patient received either 200 mg of emtricitabine (n=167) or placebo (n=81) once daily for 48 weeks and underwent a pretreatment and end-of-treatment liver biopsy. Histologic improvement was defined as a 2-point reduction in Knodell necroinflammatory score with no worsening in fibrosis. RESULTS: At the end of treatment, 103 (62%) of 167 patients receiving active treatment had improved liver histologic findings vs 20 (25%) of 81 receiving placebo (P<.001), with significance demonstrated in subgroups positive (P<.001) and negative (P=.002) for hepatitis Be (HBe) antigen. Serum HBV DNA readings showed less than 400 copies/mL in 91 (54%) of 167 patients in the emtricitabine group vs 2 (2%) of 81 in the placebo group (P<.001); alanine aminotransferase levels were normal in 65% (109/167) vs 25% (20/81), respectively (P<.001). At week 48, 20 (13%) of 159 patients in the emtricitabine group with HBV DNA measured at the end of treatment had detectable virus with resistance mutations (95% confidence interval, 8%-18%). The rate of seroconversion to anti-HBe (12%) and HBe antigen loss were not different between arms. The safety profile of emtricitabine during treatment was similar to that of placebo. Posttreatment exacerbation of HBV infection developed in 23% of emtricitabine-treated patients. CONCLUSION: In patients with chronic HBV, both positive and negative for HBe antigen, 48 weeks of emtricitabine treatment resulted in significant histologic, virologic, and biochemical improvement.

Adult↗
PubMed2006

Therapy insight: Cirrhotic cardiomyopathy.

Liver cirrhosis is associated with several cardiovascular disturbances. These disturbances include hyperdynamic systemic circulation, manifested by an increased cardiac output and decreased peripheral vascular resistance and arterial pressure. Despite the baseline increase in cardiac output, cardiac function in patients with cirrhosis is abnormal in several respects. Patients show attenuated systolic and diastolic contractile responses to stress stimuli, electrophysiological repolarization changes, including prolonged QT interval, and enlargement or hypertrophy of cardiac chambers. This constellation of cardiac abnormalities is termed cirrhotic cardiomyopathy. It has been suggested that cirrhotic cardiomyopathy has a role in the pathogenesis of cardiac dysfunction and even overt heart failure after transjugular intrahepatic portosystemic shunt placement, major surgery and liver transplantation. Cardiac dysfunction contributes to morbidity and mortality after liver transplantation, even in many patients who have no prior history of cardiac disease. Depressed cardiac contractility contributes to the pathogenesis of hepatorenal syndrome, especially in patients with spontaneous bacterial peritonitis. Pathogenic mechanisms underlying cirrhotic cardiomyopathy include cardiomyocyte-membrane biophysical changes, attenuation of the stimulatory beta-adrenergic system and overactivity of negative inotropic systems mediated via cyclic GMP. The clinical features, general diagnostic criteria, pathogenesis and treatment of cirrhotic cardiomyopathy are discussed in this review.

Cardiovascular Agents↗
PubMed2006

Recent variceal bleeding: Doppler US hepatic vein waveform in assessment of severity of portal hypertension and vasoactive drug response.

PURPOSE: To prospectively evaluate both the correlation between abnormal Doppler ultrasonography (US) hepatic vein waveforms and the hepatic venous pressure gradient (HVPG) and the response to drug treatment in patients with cirrhosis. MATERIALS AND METHODS: Ethics committee approval and informed consent of patients and control subjects were obtained. In 78 patients with cirrhosis (70 men, eight women; mean age, 49.4 years +/- 9.7 [standard deviation]) and a history of variceal bleeding, both the hepatic vein waveform--as measured with Doppler US--and the HVPG were measured, and the relationship between them was analyzed. Hepatic vein Doppler waveforms were classified as triphasic, biphasic, or monophasic. Severe portal hypertension was defined as an HVPG of more than 15 mm Hg. In a subgroup of 21 patients, changes in hepatic vein waveform and HVPG were evaluated after intravenous administration of 2 mg of terlipressin. Statistical analyses were performed with Spearman rank correlation, logistic regression analysis, and cross tabulation. RESULTS: Abnormal hepatic vein waveforms were seen in 72 patients (92%). Forty-four patients (56%) had biphasic waveforms, 28 (36%) had monophasic waveforms, and six (8%) had triphasic waveforms. A positive correlation was found between the extent of abnormalities in hepatic vein waveforms and the increase in HVPG (P < .05). Monophasic waveforms were associated with severe portal hypertension, with a sensitivity of 74% and a specificity of 95%. Twenty patients in the terlipressin subgroup had abnormal baseline waveforms; the baseline waveform improved in 18 patients in association with the HVPG reduction after injection of terlipressin. CONCLUSION: Doppler US hepatic vein waveform assessment is useful in the noninvasive evaluation of the severity of portal hypertension and the response to vasoactive drugs in patients with portal hypertension and variceal bleeding.

Antihypertensive Agents↗
PubMed2006

Acute management and secondary prophylaxis of esophageal variceal bleeding: a western Canadian survey.

BACKGROUND: Acute esophageal variceal bleeding (EVB) is a major cause of morbidity and mortality in patients with liver cirrhosis. Guidelines have been published in 1997; however, variability in the acute management and prevention of EVB rebleeding may occur. METHODS: Gastroenterologists in the provinces of British Columbia, Alberta, Manitoba and Saskatchewan were sent a self-reporting questionnaire. RESULTS: The response rate was 70.4% (86 of 122). Intravenous octreotide was recommended by 93% for EVB patients but the duration was variable. The preferred timing for endoscopy in suspected acute EVB was within 12 h in 75.6% of respondents and within 24 h in 24.6% of respondents. Most (52.3%) gastroenterologists do not routinely use antibiotic prophylaxis in acute EVB patients. The preferred duration of antibiotic therapy was less than three days (35.7%), three to seven days (44.6%), seven to 10 days (10.7%) and throughout hospitalization (8.9%). Methods of secondary prophylaxis included repeat endoscopic therapy (93%) and beta-blocker therapy (84.9%). Most gastroenterologists (80.2%) routinely attempted to titrate beta-blockers to a heart rate of 55 beats/min or a 25% reduction from baseline. The most common form of secondary prophylaxis was a combination of endoscopic and pharmacological therapy (70.9%). CONCLUSIONS: Variability exists in some areas of EVB treatment, especially in areas for which evidence was lacking at the time of the last guideline publication. Gastroenterologists varied in the use of prophylactic antibiotics for acute EVB. More gastroenterologists used combination secondary prophylaxis in the form of band ligation eradication and beta-blocker therapy rather than either treatment alone. Future guidelines may be needed to address these practice differences.

Acute Disease↗
PubMed2006

Emergency management of bleeding esophageal varices: drugs, bands or sleep?

Variceal bleeding is a severe complication of cirrhosis leading to significant morbidity and mortality. Treatment of acute variceal bleeding has improved dramatically since the era of the mechanical balloon tamponade. These advances include endoscopic band ligation or sclerotherapy, and vasoactive pharmacological options such as somatostatin, octreotide, vasopressin and terlipressin. Evidence from a multitude of clinical trials and meta-analyses comparing endoscopic and pharmacological treatments suggests near equivalence in efficacy for initial hemostasis, mortality and rate of rebleeding. This raises the question of whether on-call gastroenterologists should be performing emergency endoscopic treatment in the middle of the night or start pharmacological treatment and delay endoscopy until optimal patient and working conditions the next morning. The present review analyzes the available comparative data between endoscopic and pharmacological treatment options. Although the literature cannot yet definitively answer the question posed, the authors suggest that delaying endoscopic treatment until the next morning may be the most reasonable practical approach.

Critical Illness↗
PubMed2005

Role of endocannabinoids in the pathogenesis of cirrhotic cardiomyopathy in bile duct-ligated rats.

Cardiac contractility in cirrhosis is normal at baseline but hyporesponsive to stimuli, a phenomenon known as 'cirrhotic cardiomyopathy'. The pathogenesis remains unclear. Endocannabinoids are vasoactive, but have not previously been examined in the cirrhotic heart. We therefore aimed to systematically clarify a possible role of endocannabinoids in the pathogenesis of cirrhotic cardiomyopathy. Cirrhosis was induced in Sprague-Dawley rats by bile duct ligation; controls underwent a sham operation. At 4 weeks after operation, isolated left ventricular papillary muscle contractility was studied. Dose-response curve for a beta-adrenergic agonist isoproterenol was constructed in the presence and absence of a CB-1 antagonist AM251 (1 microM). Cirrhotic muscles had a blunted response to isoproterenol, which was completely restored by AM251. Dose-response curves to anandamide, and CB-1 and CB-2 protein and mRNA expression in Western blot and reverse transcriptase-polymerase chain reaction experiments were not significantly different between cirrhotic and sham muscles. Force-frequency relationship studies were performed in cirrhotic and normal muscles. At higher frequencies, anandamide reuptake blockers (VDM11 and AM404) significantly enhanced muscle relaxation in cirrhotic muscles, but not in controls. This effect was completely blocked by AM251 and pertussis toxin, whereas tetrodotoxin partially reversed it. Taken together, these results indicate a pathogenic role for increased local (neuronal) production of endocannabinoids, mediated by a G(i)-protein-dependent CB-1-responsive pathway in cirrhotic cardiomyopathy. The increased tachycardia-stress-induced release of endocannabinoids may help explain why contractility is normal at baseline but attenuated with stress.

Amidohydrolases↗
PubMed2005

Mitogen-induced upregulation of hepatitis C virus expression in human lymphoid cells.

Considering growing evidence indicating that hepatitis C virus (HCV) replicates in lymphoid cells, establishment of a reliable and sensitive method for detection of HCV in these cells may provide means for monitoring the infection and the efficacy of sterilizing antiviral therapy. In this study, conditions for ex vivo augmentation and detection of the HCV genome in peripheral blood mononuclear cells (PBMCs) from patients with chronic hepatitis C (CHC) or after a sustained virological response (SVR) to antiviral treatment were assessed. Following stimulation with combinations of mitogens and/or cytokines, PBMCs and, in certain cases, affinity-purified T and B cells were examined for HCV positive- and negative-strand RNA by using RT-PCR followed by nucleic acid hybridization, while the presence of viral NS3 protein was determined by flow cytometry. HCV RNA augmentation was assessed by quantification of Southern and dot-blot hybridization signals. The results showed that treatment of peripheral lymphoid cells with mitogens stimulating T- and B-cell proliferation and with cytokines supporting their growth significantly increased HCV RNA detection in patients with both CHC and SVR. This enhancement was up to 100-fold for the HCV genome and fivefold for the NS3 protein compared with untreated cells. In conclusion, HCV RNA can be readily detected in circulating lymphoid cells in progressing hepatitis C and following SVR after ex vivo cell stimulation. As such, this method offers a new investigative tool to study HCV lymphotropism and to monitor virus presence during the course of HCV infection.

Adult↗
PubMed2005

Transplant immunosuppressive agents in non-transplant chronic autoimmune hepatitis: the Canadian association for the study of liver (CASL) experience with mycophenolate mofetil and tacrolimus.

BACKGROUND: Conventional treatment of autoimmune hepatitis consists of either prednisone alone or in combination with azathioprine. Ten to 20% of patients do not respond to or are intolerant of this treatment. Novel drug treatments include immunosuppressive drugs such as tacrolimus (TAC), mycophenolate mofetil (MMF), methotrexate and cyclosporine. We describe a multi-centre Canadian experience with MMF and TAC. OBJECTIVE: To study a multi-centre patient population who had failed conventional therapy and were treated with non-conventional medical therapy for autoimmune hepatitis and document response. METHODS: Members of the Canadian Association for the Study of Liver (CASL) obtained MMF from Hoffmann-La Roche Ltd, as part of a compassionate release program, were contacted for standardized data on patients with AIH who received MMF or TAC. Response definitions based on aminotransferase changes were: Complete response (CR)-sustained normalization, partial response (PR)-improvement by greater than 50%, non-response (NR)-less than 50% improvement and relapse (RP)-initial CR or PR followed by an increase in aminotransferases. RESULTS: A total of 16 patients were identified: six in Ontario, one in Quebec, five in Alberta and four in British Columbia. Three were treated with TAC, eleven with MMF and two with combination MMF and TAC. CR was observed in 50%, PR in 12.5%, RP in 25% and NR occurred in 12.5%. The CR for MMF without TAC was approximately 64%. CONCLUSIONS: MMF is effective and well tolerated by patients with autoimmune hepatitis who do not respond to, or are intolerant of, conventional immunosuppressive agents.

Adult↗
PubMed2005

Acute hemodynamic effects of octreotide and terlipressin in patients with cirrhosis: a randomized comparison.

BACKGROUND: Octreotide and terlipressin are widely used in acute variceal hemorrhage to reduce the bleeding rate. They purportedly act by mesenteric arterial vasoconstriction, thus reducing portal venous flow (PVF) and portal pressure. Little is known about the immediate-early hemodynamic effects of these drugs. AIM: To compare the acute hemodynamic effects of octreotide and terlipressin in patients with cirrhosis. PATIENTS: Forty-two cirrhotic patients with a history of variceal bleeding were randomized to receive either octreotide 100 microg intravenous bolus followed by a continuous infusion at 250 microg/h (n = 21), or terlipressin 2 mg intravenous bolus (n = 21). METHODS: Mean arterial pressure (MAP), heart rate (HR), hepatic venous pressure gradient (HVPG), and PVF, assessed by duplex Doppler ultrasonography, were measured before and at 1, 5, 10, 15, 20, and 25 min after the start of drug administration. RESULTS: Octreotide markedly decreased HVPG (-44.5 +/- 17.8%) and PVF (-30.6 +/- 13.6%) compared to the baseline at 1 min (p < 0.05). Thereafter, both variables rapidly returned toward the baseline, and by 5 min, no significant differences in HVPG (-7.1 +/- 28.9%) and PVF (10.2 +/- 26.2%) were noted. A similar transient effect on MAP and HR was observed. Terlipressin significantly decreased HVPG (-18.3 +/- 11.9%) and PVF (-32.6 +/- 10.5%) at 1 min (p < 0.05) and sustained these effects at all time points. The effects on arterial pressure and HR were also sustained. CONCLUSIONS: Octreotide only transiently reduced portal pressure and flow, whereas the effects of terlipressin were sustained. These results suggest that terlipressin may have more sustained hemodynamic effects in patients with bleeding varices.

Blood Pressure↗
PubMed2005

Acute coinfection with hepatitis B and hepatitis C viruses.

Acute coinfection of hepatitis B virus (HBV) and hepatitis C virus (HCV) is rare. The few previously reported cases all describe acute HBV followed by acute HCV, leading to HBV clearance but chronic HCV. This is the first reported case of acute concurrent infection and spontaneous clearance of both HBV and HCV.

Acute Disease↗
PubMed2004

Histological response to interferon alfa-based therapies in hepatitis C.

Histological response is defined as an improvement in the severity of liver inflammation with or without an improvement in fibrosis in patients following treatment for an acute or chronic liver disorder. Histological response occurs in patients with chronic hepatitis C virus (HCV) infection who have had a sustained virological response following treatment with interferon (IFN) therapy and in a percentage of nonresponders. Continuing IFN long term as maintenance therapy has been shown to prevent histological progression in patients who had both a marked decline in serum HCV RNA level during treatment and a histological response on repeat histological analysis. Prospective controlled trials are currently evaluating the benefits of low-dose maintenance therapy with pegylated IFN in HCV patients who have failed to achieve sustained virological response. In the future, the development of serum markers of fibrosis may allow for monitoring of hepatic fibrosis and histological response to therapy without the need to perform repeat liver biopsy.

Antiviral Agents↗
PubMed2004

Management of hepatitis C virus genotype 4.

Hepatitis C virus (HCV) genotype 4 is predominantly found in the Middle East and North Africa. Because most of the large randomized controlled trials of antiviral therapy for chronic hepatitis C were conducted in North America and Europe, little is known about management of patients with this particular genotype. Based on the available data, sustained virological response rates to interferon-based therapies appear to be intermediate between the relatively resistant HCV genotype 1 and the readily responsive genotypes 2 and 3. Several large prospective studies of pegylated interferon plus ribavirin combination therapy, the current gold-standard treatment, have recently been completed and will be reviewed.

Antiviral Agents↗