Characteristics of REPRIEVE Trial Participants Identifying Across the Transgender Spectrum.

Because persons who identify across the transgender spectrum (PATS) are a key population in human immunodeficiency virus (HIV) yet are underreported in HIV and cardiovascular research, we aimed to characterize this population within the REPRIEVE global clinical trial (n = 7770). Acceptance of gathering gender identity was high (96%). Participation by PATS was 1.7% overall, 2.4% among natal males, 0.3% among natal females, and varied across geographic regions (from 0% in sub-Saharan Africa to 2.3% in High Income Region). Thirty percent of natal male PATS identified other than transgender. Some characteristics differed by gender. Most notably, 38% of natal male PATS receiving gender-affirming treatment had waist circumference >102 cm (compared with ≤25% in other groups). Given that PATS is a key population, HIV research should routinely report trial participation and outcomes by gender in addition to natal sex, to provide the results needed to optimize medical care to PATS.

The National MDS Natural History Study: design of an integrated data and sample biorepository to promote research studies in myelodysplastic syndromes.

Myelodysplastic syndromes (MDS), a spectrum of heterogeneous hematopoietic stem cell diseases, vary in clinical severity, response to therapy, and propensity toward progression to acute myeloid leukemia. These are acquired clonal disorders resulting from somatic mutations within the hematopoietic stem or progenitor cell population. Understanding the natural history and the risk of developing leukemia and other adverse outcomes is dependent on access to well-annotated biospecimens linked to robust clinical and molecular data. To facilitate the acquisition and distribution of MDS biospecimens to the wider scientific community and support scientific discovery in this disease, the National MDS Natural History study was initiated by the National Heart, Lung, and Blood Institute (NHLBI) and is being conducted in collaboration with community hospitals and academic medical centers supported by the National Cancer Institute (NCI). The study will recruit up to 2000 MDS patients or overlapping myeloproliferative neoplasms (MDS/MPN) and up to 500 cases of idiopathic cytopenia of undetermined significance (ICUS). The National MDS Natural History Study (NCT02775383) will offer the world's largest disease-focused tissue biobank linked to longitudinal clinical and molecular data in MDS. Here, we report on the study design features and describe the vanguard phase of 200 cases. The study assembles a comprehensive clinical database, quality of life results, laboratory data, histopathology slides and images, genetic information, hematopoietic and germline tissues representing high-quality biospecimens and data from diverse centers across the United States. These resources will be available to the scientific community for investigator-initiated research.

Rationale and design of the Mechanistic Substudy of the Randomized Trial to Prevent Vascular Events in HIV (REPRIEVE): Effects of pitavastatin on coronary artery disease and inflammatory biomarkers.

BACKGROUND: People with HIV (PWH) have increased cardiovascular events, inflammation, and high-risk coronary atherosclerosis. Statin therapy has been shown to lower the risk of cardiovascular disease (CVD) in the general population, but whether this results from reductions in coronary atherosclerosis and is mediated by decreased inflammation remains unknown. METHODS: REPRIEVE is a randomized, placebo-controlled trial of pitavastatin calcium (4 mg/day) vs. placebo enrolling at least 7500 PWH between 40-75 years, on antiretroviral therapy (ART), with low to moderate traditional CVD risk. The Mechanistic Substudy of REPRIEVE (A5333s) is co-enrolling 800 participants from 31 US sites. These participants undergo serial contrast enhanced coronary computed tomography angiography (CCTA) and measurements of biomarkers of inflammation and immune activation at baseline and after 2 years of follow-up. The primary objectives are to determine the effects of pitavastatin on noncalcified coronary atherosclerotic plaque (NCP) volume, low attenuation plaque, and positive remodeling and on changes in immune activation and inflammation and to assess relationships between the two. Changes in CAD will be assessed in a standardized fashion by a core lab with expert readers blinded to time points and participant information; immune activation and inflammation assessment is also performed centrally. RESULTS: To date the Mechanistic Substudy has completed planned enrollment, with 805 participants. CONCLUSION: This study represents the first large, randomized, CCTA-based assessment of the effects of a primary prevention strategy for CVD on high-risk CAD, immune activation and inflammation among PWH. The study will assess pitavastatin's effects on coronary plaque, and the interrelationship of these changes with biomarkers of immune activation and inflammation in PWH to determine mechanisms of CVD prevention and improved outcomes in this population.

Rationale and design of the Randomized Trial to Prevent Vascular Events in HIV (REPRIEVE).

BACKGROUND: Cardiovascular disease (CVD) is more frequent among people with HIV (PWH) and may relate to traditional and nontraditional factors, including inflammation and immune activation. A critical need exists to develop effective strategies to prevent CVD in this population. METHODS: The Randomized Trial to Prevent Vascular Events in HIV (REPRIEVE) (A5332) is a prospective, randomized, placebo-controlled trial of a statin strategy for the primary prevention of major adverse cardiovascular events (MACE) in PWH with low to moderate traditional risk. At least 7,500 PWH, 40-75 years of age, on stable antiretroviral therapy, will be randomized to pitavastatin calcium (4 mg/d) or identical placebo and followed for up to 8 years. Participants are enrolled based on the 2013 American College of Cardiology (ACC)/American Heart Association (AHA) atherosclerotic cardiovascular disease (ASCVD) risk score and low-density lipoprotein cholesterol (LDL-C) level with a goal to identify a low- to moderate-risk population who might benefit from a pharmacologic CVD prevention strategy. Potential participants with a risk score ≤ 15% were eligible based on decreasing LDL-C thresholds for increasing risk score >7.5% (LDL-C <190 mg/dL for risk score <7.5%, LDL-C <160 mg/dL for risk score 7.6%-10%, and LDL-C<130 mg/dL for risk score 10.1%-15%). The primary objective is to determine effects on a composite end point of MACE. Formal and independent adjudication of clinical events will occur using standardized criteria. Key secondary end points include effects on MACE components, all-cause mortality, specified non-CVD events, AIDS and non-AIDS events, and safety. RESULTS: To date, REPRIEVE has enrolled >7,500 participants at approximately 120 sites across 11 countries, generating a diverse and representative population of PWH to investigate the primary objective of the trial. CONCLUSIONS: REPRIEVE is the first trial investigating a primary CVD prevention strategy in PWH. REPRIEVE will inform the field of the efficacy and safety of a statin strategy among HIV-infected participants on antiretroviral therapy and provide critical information on CVD mechanisms and non-CVD events in PWH.

Central sensitization associated with low fetal hemoglobin levels in adults with sickle cell anemia.

BACKGROUND AND AIMS: Pain is the hallmark of sickle cell anemia (SCA), presenting as recurrent acute events or chronic pain. Central sensitization, or enhanced excitability of the central nervous system, alters pain processing and contributes to the maintenance of chronic pain. Individuals with SCA demonstrate enhanced sensitivity to painful stimuli however central mechanisms of pain have not been fully explored. We hypothesized that adults with SCA would show evidence of central sensitization as observed in other diseases of chronic pain. METHODS: We conducted a prospective study of static and dynamic quantitative sensory tests in 30 adults with SCA and 30 matched controls. RESULTS: Static thermal testing using cold stimuli showed lower pain thresholds (p=0.04) and tolerance (p=0.04) in sickle cell subjects, but not for heat. However, SCA subjects reported higher pain ratings with random heat pulses (p<0.0001) and change in scores with temporal summation at the heat pain threshold (p=0.002). Similarly, with the use of pressure pain stimuli, sickle cell subjects reported higher pain ratings (p=0.04), but not higher pressure pain tolerance/thresholds or allodynia to light tactile stimuli. Temporal summation pain score changes using 2 pinprick probes (256 and 512mN) were significantly greater (p=0.004 and p=0.008) with sickle cell, and delayed recovery was associated with lower fetal hemoglobin (p=0.002 and 0.003). CONCLUSIONS: Exaggerated temporal summation responses provide evidence of central sensitization in SCA. IMPLICATIONS: The association with fetal hemoglobin suggests this known SCA modifier may have a therapeutic role in modulating central sensitization.

Skeletal and myocardial microvascular blood flow in hydroxycarbamide-treated patients with sickle cell disease.

In sickle cell disease (SCD), abnormal microvascular function combined with chronic anaemia predisposes patients to perfusion-demand mismatch. We hypothesized that skeletal muscle and myocardial perfusion, normalized to the degree of anaemia, is reduced at basal-state compared to controls, and that this defect is ameliorated by hydroxycarbamide (HC; also termed hydroxyurea) therapy. Twenty-one SCD patients, of whom 15 were treated with HC, and 27 controls underwent contrast-enhanced ultrasound (CEU) perfusion imaging of the forearm as well as the myocardium. HC treatment was associated with lower white cell and reticulocyte counts, and higher fetal haemoglobin and total haemoglobin levels. When corrected for the degree of anaemia in SCD patients, skeletal flow in HC-treated patients was significantly higher than in untreated SCD patients (217·7 ± 125·4 vs. 85·9 ± 40·2, P = 0·018). Similarly, when normalized for both anaemia and increased myocardial work, resting myocardial perfusion was also significantly higher in HC-treated patients compared with untreated SCD patients (0·53 ± 0·47 vs. 0·13 ± 0·07, P = 0·028). Haemoglobin F (HbF) levels correlated with skeletal muscle microvascular flow (r = 0·55, P = 0·01). In conclusion, patients with SCD not on HC therapy have resting flow deficits in both skeletal muscle and myocardial flow. HC therapy normalizes flow and there is a direct correlation with HbF levels. Clinical trial registration ClinicalTrials.gov Identifier: NCT01602809; https://clinicaltrials.gov/ct2/show/NCT01602809?term=sACHDEV&rank=9.

Fasting and refeeding differentially regulate NLRP3 inflammasome activation in human subjects.

BACKGROUND: Activation of the NLRP3 inflammasome is associated with metabolic dysfunction, and intermittent fasting has been shown to improve clinical presentation of NLRP3 inflammasome-linked diseases. As mitochondrial perturbations, which function as a damage-associated molecular pattern, exacerbate NLRP3 inflammasome activation, we investigated whether fasting blunts inflammasome activation via sirtuin-mediated augmentation of mitochondrial integrity. METHODS: We performed a clinical study of 19 healthy volunteers. Each subject underwent a 24-hour fast and then was fed a fixed-calorie meal. Blood was drawn during the fasted and fed states and analyzed for NRLP3 inflammasome activation. We enrolled an additional group of 8 healthy volunteers to assess the effects of the sirtuin activator, nicotinamide riboside, on NLRP3 inflammasome activation. RESULTS: In the fasting/refeeding study, individuals showed less NLRP3 inflammasome activation in the fasted state compared with that in refed conditions. In a human macrophage line, depletion of the mitochondrial-enriched sirtuin deacetylase SIRT3 increased NLRP3 inflammasome activation in association with excessive mitochondrial ROS production. Furthermore, genetic and pharmacologic SIRT3 activation blunted NLRP3 activity in parallel with enhanced mitochondrial function in cultured cells and in leukocytes extracted from healthy volunteers and from refed individuals but not in those collected during fasting. CONCLUSIONS: Together, our data indicate that nutrient levels regulate the NLRP3 inflammasome, in part through SIRT3-mediated mitochondrial homeostatic control. Moreover, these results suggest that deacetylase-dependent inflammasome attenuation may be amenable to targeting in human disease. TRIAL REGISTRATION: ClinicalTrials.gov NCT02122575 and NCT00442195. FUNDING: Division of Intramural Research, NHLBI of the NIH.

Importance of angina in patients with coronary disease, heart failure, and left ventricular systolic dysfunction: insights from STICH.

BACKGROUND: Patients with left ventricular (LV) systolic dysfunction, coronary artery disease (CAD), and angina are often thought to have a worse prognosis and a greater prognostic benefit from coronary artery bypass graft (CABG) surgery than those without angina. OBJECTIVES: This study investigated: 1) whether angina was associated with a worse prognosis; 2) whether angina identified patients who had a greater survival benefit from CABG; and 3) whether CABG improved angina in patients with LV systolic dysfunction and CAD. METHODS: We performed an analysis of the STICH (Surgical Treatment for Ischemic Heart Failure) trial, in which 1,212 patients with an ejection fraction ≤35% and CAD were randomized to CABG or medical therapy. Multivariable Cox and logistic models were used to assess long-term clinical outcomes. RESULTS: At baseline, 770 patients (64%) reported angina. Among patients assigned to medical therapy, all-cause mortality was similar in patients with and without angina (hazard ratio [HR]: 1.05; 95% confidence interval [CI]: 0.79 to 1.38). The effect of CABG was similar whether the patient had angina (HR: 0.89; 95% CI: 0.71 to 1.13) or not (HR: 0.68; 95% CI: 0.50 to 0.94; p interaction = 0.14). Patients assigned to CABG were more likely to report improvement in angina than those assigned to medical therapy alone (odds ratio: 0.70; 95% CI: 0.55 to 0.90; p < 0.01). CONCLUSIONS: Angina does not predict all-cause mortality in medically treated patients with LV systolic dysfunction and CAD, nor does it identify patients who have a greater survival benefit from CABG. However, CABG does improve angina to a greater extent than medical therapy alone. (Comparison of Surgical and Medical Treatment for Congestive Heart Failure and Coronary Artery Disease [STICH]; NCT00023595).

Clinical characteristics and outcomes of patients with and without diabetes in the Surgical Treatment for Ischemic Heart Failure (STICH) trial.

AIMS: Hypothesis 1 of the Surgical Treatment for Ischemic Heart Failure (STICH) trial enrolled 1212 patients with an LVEF of ≤35% and CAD amenable to coronary artery bypass grafting (CABG). Patients were randomized to CABG and optimal medical therapy (MED) or MED alone. The objective was to assess whether or not patients with diabetes mellitus (DM) enrolled in the STICH trial would have greater benefit from CABG than patients without DM. METHODS AND RESULTS: The characteristics and clinical outcomes of patients with and without DM randomized to CABG and MED or MED alone were compared. DM was present in 40%. At baseline, patients with DM had more triple vessel CAD, higher LVEF, and smaller left ventricular volumes. In patients with DM, the primary outcome of all-cause mortality occurred in 39% of patients in the MED group and 39% in the CABG group [hazard ratio (HR) with CABG 0.96, 95% confidence interval (CI) 0.73-1.26]. In patients without DM, the primary outcome occurred in 41% of patients in the MED group and 32% in the CABG group (HR with CABG 0.80, 95% CI 0.63-1.02). While numerically it would appear that the treatment effect of CABG is blunted in patients with DM, there was no significant interaction between DM and treatment group on formal statistical testing. CONCLUSIONS: Patients with DM enrolled in the STICH trial had more triple vessel disease, smaller hearts, and higher LVEF than those without DM. CABG did not exert greater benefit in patients with DM.

Immunologic effects of hydroxyurea in sickle cell anemia.

BACKGROUND AND OBJECTIVE: Susceptibility to encapsulated bacteria is well known in sickle cell disease (SCD). Hydroxyurea use is common in adults and children with SCD, but little is known about hydroxyurea's effects on immune function in SCD. Because hydroxyurea inhibits ribonucleotide reductase, causing cell cycle arrest at the G1-S interface, we postulated that hydroxyurea might delay transition from naive to memory T cells, with inhibition of immunologic maturation and vaccine responses. METHODS: T-cell subsets, naive and memory T cells, and antibody responses to pneumococcal and measles, mumps, and rubella vaccines were measured among participants in a multicenter, randomized, double-blind, placebo-controlled trial of hydroxyurea in infants and young children with SCD (BABY HUG). RESULTS: Compared with placebo, hydroxyurea treatment resulted in significantly lower total lymphocyte, CD4, and memory T-cell counts; however, these numbers were still within the range of historical healthy controls. Antibody responses to pneumococcal vaccination were not affected, but a delay in achieving protective measles antibody levels occurred in the hydroxyurea group. Antibody levels to measles, mumps, and rubella showed no differences between groups at exit, indicating that effective immunization can be achieved despite hydroxyurea use. CONCLUSIONS: Hydroxyurea does not appear to have significant deleterious effects on the immune function of infants and children with SCD. Additional assessments of lymphocyte parameters of hydroxyurea-treated children may be warranted. No changes in current immunization schedules are recommended; however, for endemic disease or epidemics, adherence to accelerated immunization schedules for the measles, mumps, and rubella vaccine should be reinforced.

Weight Loss Programs May Have Beneficial or Adverse Effects on Fat Mass and Insulin Sensitivity in Overweight and Obese Black Women.

OBJECTIVE: Weight loss interventions have produced little change in insulin sensitivity in black women, but mean data may obscure metabolic benefit to some and adverse effects for others. Accordingly, we analyzed insulin sensitivity relative to fat mass change following a weight loss program. DESIGN AND METHODS: Fifty-four black women (BMI range 25.9 to 54.7 kg/m2) completed the 6-month program that included nutrition information and worksite exercise facilities. Fat mass was measured by dual-energy X-ray absorptiometry, and insulin sensitivity index (SI) was calculated from an insulin-modified intravenous glucose tolerance test using the minimal model. RESULTS: Baseline SI (range 0.74 to 7.58 l/mU-1•min-1) was inversely associated with fat mass (r = -0.516, p < 0.001), independent of age. On average, subjects lost fat mass (baseline 40.8 ± 12.4 to 39.4 ± 12.6 kg [mean ± SD], P < 0.01), but 17 women (32 %) actually gained fat mass. SI for the group was unchanged (baseline 3.3 ± 1.7 to 3.2 ± 1.6, P = 0.67). However, the tertile with greatest fat mass loss (-3.6 kg, range -10.7 to -1.7 kg) improved insulin sensitivity (SI +0.3 ± 1.2), whereas the tertile with net fat mass gain (+0.9 kg, range -0.1 to +3.8 kg) had reduced insulin sensitivity (SI -0.7 ± 1.3) from baseline values (P < 0.05 by ANOVA). CONCLUSIONS: Black women in a weight loss program who lose fat mass may have improved insulin sensitivity, but fat mass gain with diminished sensitivity is common. Additional support for participants who fail to achieve fat mass loss early in an intervention may be required for success.

Hydroxyurea and growth in young children with sickle cell disease.

BACKGROUND: Growth impairment is a known complication of sickle cell disease. Effects of hydroxyurea (HU) on growth in very young children are not known. METHODS: Height, weight, BMI, and head circumference (HC) were compared with World Health Organization (WHO) standards in BABY HUG, a multicenter, randomized, double-blinded, placebo-controlled 2-year clinical trial of HU in 193 children 9 to 18 months of age. Anthropometric data were closely monitored and converted to z scores by using WHO standardized algorithms for descriptive analyses. The treatment and placebo groups were compared longitudinally by using a mixed model analysis. RESULTS: At entry, the z scores of BABY HUG children were higher than WHO norms. After 2 years of HU or placebo treatment, there were no significant differences between the groups, except for the mean HC z scores at study exit (HU: +0.8 versus placebo: +1.0, P = .05). Baseline z scores were the best predictors of z scores at study exit. The absolute neutrophil count, absolute reticulocyte count, and total white blood cell count had significant negative correlations with growth measures. CONCLUSIONS: Both groups had normal or near normal anthropometric measures during the study. The HC z scores at study entry and exit were slightly greater than WHO norms. Higher baseline white blood cell count, absolute reticulocyte count, and absolute neutrophil count were associated with poorer growth. The significance of the slightly lower HC in the treatment group at study exit is not clear. Trends toward normalization of weight and height and effects on HC will be monitored in ongoing BABY HUG follow-up studies.

NHLBI clinical trials workshop: an executive summary.

On September 13-14, 2010, the National Heart, Lung and Blood Institute (NHLBI) organized a workshop: 'Clinical Trials: Past, Present and Future'. The workshop covered many areas in clinical trials, including the history of clinical trials at NHLBI, Bayesian clinical trials, surrogate endpoints, reporting clinical trials, handling missing data, flexible designs and adaptive trials, personalized medicine and genomic clinical trials, and comparative effectiveness research. In this report, we summarize the main discussions and conclusions based on the presentations of the invited speakers at the workshop.

Changes in exercise capacity in subjects with cardiac asymptomatic hereditary hemochromatosis during a follow-up after 5 yrs.

OBJECTIVE: A long-term effect of hereditary hemochromatosis (HH) on aerobic exercise capacity (AEC) has not been well described. DESIGN: Forty-three HH and 21 volunteer control subjects who were asymptomatic underwent cardiopulmonary exercise testing using the Bruce protocol. AEC was assessed with minute ventilation (V(E)), oxygen uptake (V(O)(2)), and carbon dioxide production (V(CO)(2)) at baseline and at a follow-up assessment after 5 yrs. A paired t test was used for analyses of normality data; otherwise, Wilcoxon's signed rank-sum test was used. RESULTS: Thirty-three HH subjects and 18 volunteer control subjects returned for a repeat cardiopulmonary exercise testing at the fifth-year follow-up (80% overall return rate). At the fifth-year follow-up, AEC was not different between the two groups. Compared with baseline measurements, exercise time, peak V(O)(2), and the V(E)/V(CO)(2) slope did not differ statistically at the fifth-year follow-up between both groups. Iron depletion through phlebotomy for 5 yrs did not significantly affect AEC in newly diagnosed HH subjects at baseline (n = 14) and cardiac arrhythmias during exercise tended to decrease after 5 yrs of therapy in this group. CONCLUSIONS: The AEC of asymptomatic HH subjects treated using conventional therapy is not statistically affected by the disease during a 5-yr period.

High-density lipoprotein cholesterol efflux, nitration of apolipoprotein A-I, and endothelial function in obese women.

Subjects at risk of atherosclerosis might have dysfunctional high-density lipoprotein (HDL) despite normal cholesterol content in the plasma. We considered whether the efflux of excess cellular cholesterol to HDL from obese subjects is associated with impaired arterial endothelial function, a biomarker of cardiovascular risk. A total of 54 overweight (body mass index [BMI] 25 to 29.9 kg/m(2)) or obese (BMI ≥30 kg/m(2)) women, aged 46 ± 11 years, were enrolled in a worksite wellness program. The HDL cholesterol averaged 57 ± 17 mg/dl and was inversely associated with the BMI (r = -0.419, p = 0.002). Endothelial function was assessed using brachial artery flow-mediated dilation. Cholesterol efflux from (3)H-cholesterol-labeled baby hamster kidney cells transfected with the adenosine triphosphate-binding cassette transporter 1 showed 8.2% to 22.5% cholesterol efflux within 18 hours when incubated with 1% serum and was positively correlated with brachial artery flow-mediated dilation (p <0.05), especially in the 34 subjects with BMI ≥30 kg/m(2) (r = 0.482, p = 0.004). This relation was independent of age, HDL or low-density lipoprotein cholesterol concentrations in plasma, blood pressure, or insulin resistance on stepwise multiple regression analysis (ß = 0.31, R(2) = 0.21, p = 0.007). Nitration of apolipoprotein A-I tyrosine residues (using sandwich enzyme-linked immunosorbent assay) was significantly greater in women with a BMI ≥30 kg/m(2) and the lowest cholesterol efflux than in women with a BMI of 25 to 29.9 kg/m(2) and the greatest cholesterol efflux (p = 0.01). In conclusion, we have shown that decreased cholesterol efflux by way of the adenosine triphosphate-binding cassette transporter 1 is associated with increased nitration of apolipoprotein A-I in HDL and is an independent predictor of impaired endothelial function in women with a BMI of ≥30 kg/m(2). This finding suggests that the functional measures of HDL might be better markers for cardiovascular risk than the HDL cholesterol levels in this population.

Incidence of cardiac arrhythmias in asymptomatic hereditary hemochromatosis subjects with C282Y homozygosity.

It is not well known whether systemic iron overload per se in hereditary hemochromatosis (HH) is associated with cardiac arrhythmias before other signs and symptoms of cardiovascular disease occur. In the present study, we examined the incidence of cardiac arrhythmia in cardiac asymptomatic subjects with HH (New York Heart Association functional class I) and compared it to that in age- and gender-matched normal volunteers. The 42 subjects with HH and the 19 normal control subjects were recruited through the National Heart, Lung, and Blood Institute-sponsored "Heart Study of Hemochromatosis." They completed 48-hour Holter electrocardiography ambulatory monitoring at the baseline evaluation. The subjects with HH were classified as newly diagnosed (group A) and chronically treated (group B) subjects. All subjects with HH had C282Y homozygosity, and the normal volunteers lacked any HFE gene mutations known to cause HH. Although statistically insignificant, the incidence of ventricular and supraventricular ectopy tended to be greater in the combined HH groups than in the controls. Supraventricular ectopy was more frequently noted in group B compared to in the controls (ectopy rate per hour 11.1 ± 29.9 vs 1.5 ± 3.5, p < 0.05, using the Kruskal-Wallis test). No examples of heart block, other than first-degree atrioventricular node block, were seen in any of the subjects. The incidence of cardiac arrhythmias was not significantly reduced after 6 months of intensive iron removal therapy in the group A subjects. No life-threatening arrhythmias were observed in our subjects with HH. In conclusion, our data suggest that the incidence of cardiac arrhythmias is, at most, marginally increased in asymptomatic subjects with HH. A larger clinical study is warranted to further clarify our observation.