Clinical Outcomes of Adult Fontan-Associated Liver Disease and Combined Heart-Liver Transplantation.

BACKGROUND: The impact of Fontan-associated liver disease (FALD) on post-transplant mortality and indications for combined heart-liver transplant (CHLT) in adult Fontan patients remains unknown. OBJECTIVES: The purpose of this study was to assess the impact of FALD on post-transplant outcomes and compare HT vs CHLT in adult Fontan patients. METHODS: We performed a retrospective-cohort study of adult Fontan patients who underwent HT or CHLT across 15 centers. Inclusion criteria were as follows: 1) Fontan; 2) HT/CHLT referral; and 3) age ≥16 years at referral. Pretransplant FALD score was calculated using the following: 1) cirrhosis; 2) varices; 3) splenomegaly; or 4) ≥2 paracenteses. RESULTS: A total of 131 patients (91 HT and 40 CHLT) were included. CHLT recipients were more likely to be older (P = 0.016), have a lower hemoglobin (P = 0.025), require ≥2 diuretic agents pretransplant (P = 0.051), or be transplanted in more recent decades (P = 0.001). Postmatching, CHLT demonstrated a trend toward improved survival at 1 year (93% vs 74%; P = 0.097) and improved survival at 5 years (86% vs 52%; P = 0.041) compared with HT alone. In patients with a FALD score ≥2, CHLT was associated with improved survival (1 year: 85% vs 62%; P = 0.044; 5 years: 77% vs 42%; P = 0.019). In a model with transplant decade and FALD score, CHLT was associated with improved survival (HR: 0.33; P = 0.044) and increasing FALD score was associated with worse survival (FALD score: 2 [HR: 14.6; P = 0.015], 3 [HR: 22.2; P = 0.007], and 4 [HR: 27.8; P = 0.011]). CONCLUSIONS: Higher FALD scores were associated with post-transplant mortality. Although prospective confirmation of our findings is necessary, compared with HT alone, CHLT recipients were older with higher FALD scores, but had similar survival overall and superior survival in patients with a FALD score ≥2.

Morbidity and Mortality in Adult Fontan Patients After Heart or Combined Heart-Liver Transplantation.

BACKGROUND: An increasing number of adult Fontan patients require heart transplantation (HT) or combined heart-liver transplant (CHLT); however, data regarding outcomes and optimal referral time remain limited. OBJECTIVES: The purpose of this study was to define survivorship post-HT/CHLT and predictors of post-transplant mortality, including timing of referral, in the adult Fontan population. METHODS: A retrospective cohort study of adult Fontan patients who underwent HT or CHLT across 15 centers in the United States and Canada was performed. Inclusion criteria included the following: 1) Fontan; 2) HT/CHLT referral; and 3) age ≥16 years at the time of referral. Date of "failing" Fontan was defined as the earliest of the following: worsening fluid retention, new ascites, refractory arrhythmia, "failing Fontan" diagnosis by treating cardiologist, or admission for heart failure. RESULTS: A total of 131 patients underwent transplant, including 40 CHLT, from 1995 to 2021 with a median post-transplant follow-up time of 1.6 years (Q1 0.35 years, Q3 4.3 years). Survival was 79% at 1 year and 66% at 5 years. Survival differed by decade of transplantation and was 87% at 1 year and 76% at 5 years after 2010. Time from Fontan failure to evaluation (HR/year: 1.23 [95% CI: 1.11-1.36]; P < 0.001) and markers of failure, including NYHA functional class IV (HR: 2.29 [95% CI: 1.10-5.28]; P = 0.050), lower extremity varicosities (HR: 3.92 [95% CI: 1.68-9.14]; P = 0.002), and venovenous collaterals (HR: 2.70 [95% CI: 1.17-6.20]; P = 0.019), were associated with decreased post-transplant survival at 1 year in a bivariate model that included transplant decade. CONCLUSIONS: In our multicenter cohort, post-transplant survival improved over time. Late referral after Fontan failure and markers of failing Fontan physiology, including worse functional status, lower extremity varicosities, and venovenous collaterals, were associated with post-transplant mortality.

Timing of pulmonary valve replacement: can we use the same volumetric thresholds in repaired tetralogy of Fallot and pulmonary stenosis?

The timing of pulmonary valve replacement in patients with pulmonary regurgitation following treatment of pulmonary stenosis is undefined. Although cardiac magnetic resonance-based right ventricular volumes in tetralogy of Fallot patients have been used as a guide in pulmonary stenosis patients, anatomic differences between tetralogy of Fallot and pulmonary stenosis patients complicate their application to pulmonary stenosis patients and could result in late referral for pulmonary valve replacement. We sought to determine if pulmonary stenosis patients referred for pulmonary valve replacement were at greater risk for morbidity or need for tricuspid valve intervention at the time of pulmonary valve replacement. A retrospective cohort study was performed on all adult patients with a diagnosis of pulmonary stenosis or tetralogy of Fallot followed at our centre. Clinical and imaging-based exposures were collected. Pre-specified endpoints included need for concomitant tricuspid valve repair or replacement and pre- and post-pulmonary valve replacement cardiac magnetic resonance-based volumetric measurements. Between 1/1999 and 1/2020, 235 patients underwent pulmonary valve replacement for pulmonary regurgitation (52 with pulmonary stenosis, 183 with tetralogy of Fallot). Pulmonary stenosis patients were more likely to have at least moderate tricuspid regurgitation (p = 0.010), undergo concomitant tricuspid valve intervention (p = 0.003), and require tricuspid valve repair or replacement secondary to annular dilation (p = 0.027) compared to tetralogy of Fallot patients. There was no difference in pre-pulmonary valve replacement right ventricular size between pulmonary stenosis and tetralogy of Fallot patients. These findings suggest that referral for pulmonary valve replacement may be occurring later in the disease course for pulmonary stenosis patients.

Cardiac MRI predictors of adverse outcomes in adults with a systemic right ventricle.

AIMS: Predicting risk in individuals with a systemic right ventricle (SRV) remains difficult. We assessed the value of cardiac MRI (CMR) for predicting death, heart transplantation (HT), or need for a ventricular assist device (VAD) in adults with D-transposition of the great arteries (DTGA) post Mustard/Senning and in adults with congenitally corrected transposition of the great arteries (ccTGA) at two large academic centres. METHODS AND RESULTS: Between December 1999 and November 2020, 158 adult patients with an SRV underwent CMR. Indexed right ventricular end-diastolic volume (RVEDVI), indexed right ventricular end-systolic volume (RVESVI), right ventricular ejection fraction (RVEF), and right ventricular mass (RV mass) were determined by a core laboratory. Receiver operating curves, area under the curve (AUC), and cut-points maximizing sensitivity and specificity for the endpoint for each CMR parameter were calculated. Over a median of 8.5 years, 21 patients (13%) met a combined endpoint of HT referral, VAD, or death. Each CMR parameter was significantly associated with the endpoint in both cohorts. The AUCs for RVEDVI, RVESVI, RVEF, and RV mass to predict the endpoint were 0.93, 0.90, 0.73, and 0.84 for DTGA and 0.76, 0.74, 0.71, and 0.74 for ccTGA, respectively. Optimized cut-points for RVEDVI were calculated for DTGA and ccTGA and were 132 and 126 mL/m2 , respectively. RVEDVI cut-points were simplified to 130 mL/m2 for survival analysis, which was significantly associated with survival in both cohorts. CONCLUSIONS: Cardiac MRI parameters are associated with an increased risk of death, HT, or VAD in patients with an SRV and should be considered to facilitate risk stratification.

COVID-19 in Adults With Congenital Heart Disease.

BACKGROUND: Adults with congenital heart disease (CHD) have been considered potentially high risk for novel coronavirus disease-19 (COVID-19) mortality or other complications. OBJECTIVES: This study sought to define the impact of COVID-19 in adults with CHD and to identify risk factors associated with adverse outcomes. METHODS: Adults (age 18 years or older) with CHD and with confirmed or clinically suspected COVID-19 were included from CHD centers worldwide. Data collection included anatomic diagnosis and subsequent interventions, comorbidities, medications, echocardiographic findings, presenting symptoms, course of illness, and outcomes. Predictors of death or severe infection were determined. RESULTS: From 58 adult CHD centers, the study included 1,044 infected patients (age: 35.1 ± 13.0 years; range 18 to 86 years; 51% women), 87% of whom had laboratory-confirmed coronavirus infection. The cohort included 118 (11%) patients with single ventricle and/or Fontan physiology, 87 (8%) patients with cyanosis, and 73 (7%) patients with pulmonary hypertension. There were 24 COVID-related deaths (case/fatality: 2.3%; 95% confidence interval: 1.4% to 3.2%). Factors associated with death included male sex, diabetes, cyanosis, pulmonary hypertension, renal insufficiency, and previous hospital admission for heart failure. Worse physiological stage was associated with mortality (p = 0.001), whereas anatomic complexity or defect group were not. CONCLUSIONS: COVID-19 mortality in adults with CHD is commensurate with the general population. The most vulnerable patients are those with worse physiological stage, such as cyanosis and pulmonary hypertension, whereas anatomic complexity does not appear to predict infection severity.

Cardiac transplantation in adult congenital heart disease with prior sternotomy.

BACKGROUND: Adult congenital heart disease (ACHD) patients who require orthotopic heart transplantation are surgically complex due to anatomical abnormalities and multiple prior surgeries. In this study, we investigated these patients' outcomes using our institutional database. METHODS: ACHD patients who had prior intracardiac repair and subsequent heart transplant were included (2008-2018). Adult patients without ACHD were extracted as a control. A comparison of patients with functional single ventricular (SV) and biventricular (BV) hearts was performed. RESULTS: There were 9 SV and 24 BV patients. The SV group had higher central venous pressure/pulmonary capillary wedge pressure (P = .028), hemoglobin concentration (P = .010), alkaline phosphatase (P = .022), and were more likely to have liver congestion (P = .006). Major complications included infection in 16 (48.5%), temporary dialysis in 12 (36.4%), and graft dysfunction requiring perioperative mechanical support in 7 (21.2%). Overall in-hospital mortality was 15.2%. Kaplan-Meier analysis showed a higher, but not statistically significant, survival after 10 years between the ACHD and control groups (ACHD 84.9% vs. control 67.5%, P = .429). There was no significant difference in 10-year survival between SV and BV groups (78% vs. 88%, P = .467). CONCLUSIONS: Complex ACHD cardiac transplant recipients have a high incidence of early morbidities after transplantation. However, long-term outcomes were acceptable.

Impact of Coronavirus Disease 2019 (COVID-19) on Patients With Congenital Heart Disease Across the Lifespan: The Experience of an Academic Congenital Heart Disease Center in New York City.

Background We sought to assess the impact and predictors of coronavirus disease 2019 (COVID-19) infection and severity in a cohort of patients with congenital heart disease (CHD) at a large CHD center in New York City. Methods and Results We performed a retrospective review of all individuals with CHD followed at Columbia University Irving Medical Center who were diagnosed with COVID-19 between March 1, 2020 and July 1, 2020. The primary end point was moderate/severe response to COVID-19 infection defined as (1) death during COVID-19 infection; or (2) need for hospitalization and/or respiratory support secondary to COVID-19 infection. Among 53 COVID-19-positive patients with CHD, 10 (19%) were <18 years of age (median age 34 years of age). Thirty-one (58%) had complex congenital anatomy including 10 (19%) with a Fontan repair. Eight (15%) had a genetic syndrome, 6 (11%) had pulmonary hypertension, and 9 (17%) were obese. Among adults, 18 (41%) were physiologic class C or D. For the entire cohort, 9 (17%) had a moderate/severe infection, including 3 deaths (6%). After correcting for multiple comparisons, the presence of a genetic syndrome (odds ratio [OR], 35.82; P=0.0002), and in adults, physiological Stage C or D (OR, 19.38; P=0.002) were significantly associated with moderate/severe infection. Conclusions At our CHD center, the number of symptomatic patients with COVID-19 was relatively low. Patients with CHD with a genetic syndrome and adults at advanced physiological stage were at highest risk for moderate/severe infection.

Effect of Ventricular Pacing on Morbidity in Adults After Fontan Repair.

Implantation of a permanent pacemaker is a negative prognostic marker in patients with Fontan palliation; however, data delineating outcomes in adult patients with pacemaker requirements are lacking. We hypothesize that high ventricular pacing burden is associated with adverse outcomes in adult Fontan patients. We performed a retrospective review comprising adult patients with history of Fontan repair. A high burden of ventricular pacing was defined as ≥40% pacing. Major adverse clinical events (MACE) were defined as all-cause mortality or need for advanced cardiac therapies (ventricular assist device or heart transplant). A total of 145 adult patients with Fontan were studied for a median of 3.1 years. Twenty (14%) patients had implanted pacemakers with ≥40% ventricular pacing. Twelve events occurred in those with ≥40% ventricular pacing (incidence 60.0%) versus 11 in those without (incidence 8.8%). In multivariable analysis, ≥40% ventricular-pacing (odds ratio 12.51, confidence interval [CI] 3.56 to 43.83, p <0.001) was associated with MACE independent of initial Fontan type, New York Heart Association functional class at baseline, or history of atrial tachyarrythmia. In survival analysis, patients with ≥40% ventricular pacing had nearly 8 times the risk of MACE compared with those with a lower ventricular pacing burden (hazard ratio 7.79, 95% CI 2.56 to 23.66, p <0.001), whereas patients with atrial-only or <40% ventricular pacing burden had a trend toward higher hazard of MACE compared with those without permanent pacemaker (hazard ratio 3.38, 95% CI 0.92 to 12.47, p = 0.07) that did not meet statistical significance. These findings suggest that high ventricular pacing burden contributes to poor outcomes in the adult Fontan patients and bear consideration when determining optimal treatment of tachyarrhythmias in this population.

Scimitar Syndrome in Children and Adults: Natural History, Outcomes, and Risk Analysis.

BACKGROUND: Scimitar syndrome involves congenital anomalous pulmonary venous return to the inferior vena cava. Optimal management remains controversial. We describe the natural history of disease, nonsurgical and surgical outcomes, and risk factors for poor outcomes at our institution. METHODS: Patients with anomalous pulmonary venous return to the inferior vena cava documented on echocardiography at our institution between January 1994 and January 2015 were reviewed retrospectively. The study protocol IRB-AAAO1805 was approved. RESULTS: Forty-seven patients were identified, including 20 infants with significant associated congenital heart defects (42.6%, including 7 with single ventricle physiology), and 10 infants (21.3%) and 16 noninfants (34.0%) with isolated scimitar syndrome. Median follow-up was 3.55 years. Noninfants exhibited lower incidences of right pulmonary artery hypoplasia (p < 0.001), aortopulmonary collaterals (p = 0.004), and scimitar vein obstruction at the caval confluence (p = 0.032). Eighteen patients (38.3%) underwent surgical repair for scimitar syndrome. Overall mortality after baffle repair or scimitar vein reimplantation was 37.5% (3 of 8) for infants and 0% (0 of 6) for noninfants (p = 0.209). Overall mortality for medically managed infants was 46.7% (7 of 15) compared with 0% (0 of 8) for noninfants (p = 0.052). Multivariable analyses identified infantile onset as an independent risk factor for stenosis or obstruction after repair (hazard ratio 9.34, p = 0.048), and single ventricle physiology as an independent risk factor for mortality among unrepaired patients (hazard ratio 29.8, p = 0.004). CONCLUSIONS: The severity of scimitar syndrome depends on presenting age and associated congenital heart disease. Nonsurgical and surgical outcomes are suboptimal for infantile disease, which is a risk factor for stenosis after repair. Single ventricle physiology is associated with poor prognosis.

Serial cardiac MRIs in adult Fontan patients detect progressive hepatic enlargement and congestion.

BACKGROUND: The progression of hepatic disease in adult Fontan patients is not well understood. They reviewed the experience with serial cardiac MRIs (CMR) in adult Fontan patients to determine if hepatic anatomic markers of prolonged Fontan exposure were present and if clinical predictors of progressive hepatic congestion could be identified. METHODS AND RESULTS: A retrospective cohort study of all adult Fontan patients who had undergone at least two CMRs was performed. Hepatic dimensions, inferior vena cava (IVC) size, right hepatic vein (RHV) size and spleen diameter were determined from images acquired at the time of clinically guided CMR. Two radiologists with expertise in hepatic imaging graded congestion and liver size independently using post-gadolinium contrast sequences. Twenty-seven patients met inclusion criteria. Over a mean time of 5.1 years between CMRs, there was a significant increase in mean lateral-medial hepatic dimension (P = .005), mean RHV diameter (P = .004), and mean splenic diameter (P = .001). Serial post-gadolinium imaging was available in 25/27 (93%) patients of which 15/27 (55%) showed evidence of progressive hepatic congestion across serial studies. Progressive hepatic congestion was associated with single ventricle ejection fraction (SVEF) less than 50% (P = .008), and larger indexed end-diastolic (EDVI) and end-systolic volume (ESVI). RHV diameter was the only anatomic variable significantly correlated with time from Fontan completion (P = .004). CONCLUSIONS: Serial CMRs detected progressive liver and hepatic vein enlargement in our cohort of adult Fontan patients over a mean time of 5.2 years. Progressive hepatic congestion occurs in a significant number of adult Fontan patients and may be associated with ventricular enlargement and decreased ventricular function by CMR.

Procedural Success and Adverse Events in Pulmonary Artery Stenting: Insights From the NCDR.

BACKGROUND: Risk factors associated with outcomes for pulmonary artery (PA) stenting remain poorly defined. OBJECTIVES: The goal of this study was to determine the effect of patient and procedural characteristics on rates of adverse events and procedural success. METHODS: Registry data were collected, and 2 definitions of procedural success were pre-specified for patients with biventricular circulation: 1) 20% reduction in right ventricular pressure or 50% increase in PA diameter; and 2) 25% reduction in right ventricular pressure or 50% decrease in PA gradient or post-procedure ratio of in-stent minimum to pre-stent distal diameter >80%. A separate definition of procedural success based on normalization of PA diameter was pre-specified for patients with single ventricle palliation. RESULTS: Between January 2011 and January 2014, a total of 1,183 PA stenting procedures were performed at 59 institutions across 1,001 admissions; 262 (22%) procedures were performed in patients with a single ventricle. The rate of procedural success was 76% for definition 1, 86% for definition 2, and 75% for single ventricle patients. In the multivariate analysis, ostial stenosis was significantly associated with procedural success for biventricular patients according to both definitions. The overall complication rate was 14%, with 9% of patients experiencing death or a major adverse event (MAE). According to multivariate analysis, weight <4 kg, having a single ventricle, and emergency status were significantly associated with death or MAEs. CONCLUSIONS: In our analysis, success was >75% across all definitions, and adverse events were relatively common. Biventricular patients with an ostial stenosis had a higher probability of a successful outcome. Patients who had a single ventricle, weight <4 kg, or who underwent an emergency procedure had a higher risk of death or MAE. These findings may help inform patient selection for PA stenting.

Postoperative tricuspid regurgitation after adult congenital heart surgery is associated with adverse clinical outcomes.

OBJECTIVE: Many patients with adult congenital heart disease will require cardiac surgery during their lifetime, and some will have concomitant tricuspid regurgitation. However, the optimal management of significant tricuspid regurgitation at the time of cardiac surgery remains unclear. We assessed the determinants of adverse outcomes in patients with adult congenital heart disease and moderate or greater tricuspid regurgitation undergoing cardiac surgery for non-tricuspid regurgitation-related indications. METHODS: All adult patients with congenital heart disease and greater than moderate tricuspid regurgitation who underwent cardiac surgery for non-tricuspid regurgitation-related indications were included in a retrospective study at the Schneeweiss Adult Congenital Heart Center. Cohorts were defined by the type of tricuspid valve intervention at the time of surgery. The primary end point of interest was a composite of death, heart transplantation, and reoperation on the tricuspid valve. RESULTS: A total of 107 patients met inclusion criteria, and 17 patients (17%) reached the primary end point. A total of 68 patients (64%) underwent tricuspid valve repair, 8 patients (7%) underwent tricuspid valve replacement, and 31 patients (29%) did not have a tricuspid valve intervention. By multivariate analysis, moderate or greater postoperative tricuspid regurgitation was associated with a hazard ratio of 6.12 (1.84-20.3) for the primary end point (P = .003). In addition, failure to perform a tricuspid valve intervention at the time of surgery was associated with an odds ratio of 4.17 (1.26-14.3) for moderate or greater postoperative tricuspid regurgitation (P = .02). CONCLUSIONS: Moderate or greater postoperative tricuspid regurgitation was associated with an increased risk of death, transplant, or reoperation in adult patients with congenital heart disease undergoing cardiac surgery for non-tricuspid regurgitation-related indications. Concomitant tricuspid valve intervention at the time of cardiac surgery should be considered in patients with adult congenital heart disease with moderate or greater preoperative tricuspid regurgitation.

Usefulness of magnetic resonance imaging to guide referral for pulmonary valve replacement in repaired tetralogy of Fallot.

The aim of this study was to determine if adult patients with repaired tetralogy of Fallot are being referred for pulmonary valve replacement (PVR) earlier on the basis of cardiac magnetic resonance imaging (CMR) parameters despite the absence of CMR-based recommendations in the American College of Cardiology and American Heart Association joint guidelines. Variables defined by the guidelines were analyzed in conjunction with CMR-based parameters across 3 groups defined by the release of the guidelines: (1) patients referred before the guidelines, (2) patients referred 0 to 3 years after the guidelines, and (3) patients referred ≥3 years after the guidelines. Seventy-nine patients were identified. No significant trend was observed in guideline-defined variables. Significant trends in indexed right ventricular end-diastolic volume (p = 0.034), indexed right ventricular end-systolic volume (p = 0.001), and the right ventricular ejection fraction (p = 0.005) were observed across groups. By multivariate regression, patients who underwent PVR ≥3 years after the release of the guidelines had a 29 ml/m(2) smaller indexed right ventricular end-diastolic volume (p = 0.01) and a 33 ml/m(2) smaller indexed right ventricular end-systolic volume (p <0.001) compared with patients who underwent PVR before the release of the guidelines. PVR 0 to 3 years after the guidelines was not a significant predictor of either indexed right ventricular end-diastolic volume (p = 0.93) or indexed right ventricular end-systolic volume (p = 0.18). Patients referred for PVR ≥3 years after the guidelines had significantly smaller CMR-based right ventricular volumes without significant trends in guideline-defined variables. Given the increased use of CMR to guide PVR referral, revisiting the guidelines to address appropriate use of CMR derived thresholds is indicated.

Ototoxicity in children treated for osteosarcoma.

BACKGROUND: Cisplatin is an effective agent against osteosarcoma. Ototoxicity from osteosarcoma treatment protocols has not been well defined. The aim of this study was to determine the incidence and risk factors for hearing loss in children treated for osteosarcoma. PROCEDURE: Eligible patients had osteosarcoma diagnosed and treated at the Dana-Farber Cancer Institute/Children's Hospital Boston from January 1, 1995 to December 12, 2004, were 3-18 years of age at diagnosis, and had a normal audiogram prior to the start of chemotherapy. Patients received cisplatin according to the standard practice or current open protocol. Patients who developed hearing loss during treatment had cisplatin held on an individualized basis. Hearing function was evaluated prior to the start of therapy, before each cycle, and off-therapy. Fisher's exact test and logistic regression models were used to identify univariate and independent predictors of hearing loss, respectively. RESULTS: Seven out of nine patients (78%) who received cisplatin 120 mg/m(2)/day on 1 day developed hearing loss compared to 8/27 (30%) who received 60 mg/m(2)/day for 2 days (P = 0.019). Logistic regression showed that age, cumulative cisplatin dose, and administration of cisplatin 120 mg/m(2)/day were independent predictors of hearing loss. Cisplatin administered as 60 mg/m(2)/day for 2 days resulted in a low incidence (30%) of any hearing loss and a very low incidence (4%) of educationally significant hearing loss. CONCLUSIONS: Cisplatin administered as 60 mg/m(2)/day for 2 days resulted in a low incidence of significant hearing loss. These results suggest that cisplatin as 120 mg/m(2)/day be avoided due to an unacceptable incidence of hearing loss.

An example of the healing powers of a human being.

A 60-year-old man was referred as an emergency with a 3 month history of left sided abdominal pain and weight loss. He had no other medical problems and took no medications. An endoscopy was performed. This demonstrated a normal oesophagus and stomach and a fleshy mass in the first part of the duodenum with surrounding slough. As this was presumed to be malignant, biopsies were taken. Computed tomography (CT) scan of the abdomen was performed which showed a large, complex, loculated intra-abdominal collection containing air. Results from duodenal biology showed the presence of ulcer slough and liver tissue. The patient was diagnosed with a perforated duodenal ulcer, which had occurred some months previously, and which had eroded into the liver. He was observed and treated with intravenous antibiotics. The patient was discharged on day 14. Follow-up CT scan at 6 weeks showed complete resolution of the collection.

Ethnic variation of thiopurine S-methyltransferase activity: a large, prospective population study.

UNLABELLED: The use of azathioprine (and its metabolite mercaptopurine) is limited by toxicity, especially myelosuppression, which is related to activity of the enzyme thiopurine S-methyltransferase (TPMT). TPMT activity varies between individuals and is considered deficient in one in 300 cases. AIMS & METHODS: We identified TPMT activity within an ethnically diverse population of patients attending an inner-city hospital phlebotomy service. A total of 1000 subjects were recruited and analyzed with respect to age, sex and ethnicity. RESULTS: Samples were analyzed from 456 Caucasians, 342 South Asians and 180 Afro-Caribbeans. Six subjects had deficient TPMT activity (0.6%: four women, two men; four Caucasians, one Afro-Caribbean, one South Asian). TPMT activity (nmol 6-methylthioguanine (6-MTG)/gHb/h) ranged 0-76 (median [interquartile range]: 33 [28-39]). Enzyme activity was lower in Afro-Caribbeans (30 [25-37.5]) than Caucasians (34 [29-40]) and South Asians (33 [29-38]), which was significant after adjustment for age and sex (p < 0.0001). Activity was lower in women (p = 0.022), especially South Asian females (n = 194; 32 [28-36]), compared with (35 [30-40]) in men (n = 148; p = 0.002). CONCLUSIONS: A higher prevalence of TPMT deficiency was recorded than in previous studies. Afro-Caribbeans have lower activity than Caucasians and South Asians. TPMT enzyme activity was lower among females, especially in South Asians.

Reference intervals for thiopurine S-methyltransferase activity in red blood cells using 6-thioguanine as substrate and rapid non-extraction liquid chromatography.

BACKGROUND: Although widely used, thiopurine drugs have a narrow therapeutic index and treatment can result in life-threatening toxicity, the basis being pharmacogenetic variation in thiopurine metabolism by thiopurine S-methyltransferase (TPMT). We recently developed a modified phenotyping assay to determine TPMT activity in red blood cells. Here we describe improvements to the method and establish reference intervals in a large prospective study. METHODS: A modified enzyme assay for TPMT activity is reported. It uses 6-thioguanine as substrate with heat treatment of the incubate to stop the reaction and precipitate protein prior to high-performance liquid chromatographic (HPLC) analysis. Measurement of the reaction product, 6-methylthioguanine (6-MTG), uses HPLC with fluorimetric detection. RESULTS: The assay shows excellent characteristics, with clear discrimination of patients who are deficient in TPMT activity (< 5 nmol 6-MTG per g Hb per h) from heterozygotes (5-24 nmol 6-MTG per g Hb per h) and patients with normal activity (>25 nmol 6-MTG per g Hb per h). CONCLUSION: A modified TPMT assay is described which is suited for routine analysis in a regional centre. The method overcomes the need for extraction and has speeded up the chromatographic determination of 6-MTG, enabling large numbers of samples to be analysed. A prospective study of 1000 individuals has established the distribution of TPMT activity using the assay.