Daniel M. Bloomfield

Rolofylline, an Adenosine A1−Receptor Antagonist, in Acute Heart Failure

BACKGROUND Worsening renal function, which is associated with adverse outcomes, often develops in patients with acute heart failure. Experimental and clinical studies suggest that counterregulatory responses mediated by adenosine may be involved. We tested the hypothesis that the use of rolofylline, an adenosine A1-receptor antagonist, would improve dyspnea, reduce the risk of worsening renal function, and lead to a more favorable clinical course in patients with acute heart failure. METHODS We conducted a multicenter, double-blind, placebo-controlled trial involving patients hospitalized for acute heart failure with impaired renal function. Within 24 hours after presentation, 2033 patients were randomly assigned, in a 2:1 ratio, to receive daily intravenous rolofylline (30 mg) or placebo for up to 3 days. The primary end point was treatment success, treatment failure, or no change in the patients clinical condition; this end point was defined according to survival, heart-failure status, and changes in renal function. Secondary end points were the post-treatment development of persistent renal impairment and the 60-day rate of death or readmission for cardiovascular or renal causes. RESULTS Rolofylline, as compared with placebo, did not provide a benefit with respect to the primary end point (odds ratio, 0.92; 95% confidence interval, 0.78 to 1.09; P=0.35). Persistent renal impairment developed in 15.0% of patients in the rolofylline group and in 13.7% of patients in the placebo group (P=0.44). By 60 days, death or readmission for cardiovascular or renal causes had occurred in similar proportions of patients assigned to rolofylline and placebo (30.7% and 31.9%, respectively; P=0.86). Adverse-event rates were similar overall; however, only patients in the rolofylline group had seizures, a known potential adverse effect of A1-receptor antagonists. CONCLUSIONS Rolofylline did not have a favorable effect with respect to the primary clinical composite end point, nor did it improve renal function or 60-day outcomes. It does not show promise in the treatment of acute heart failure with renal dysfunction. (Funded by NovaCardia, a subsidiary of Merck; ClinicalTrials.gov numbers, NCT00328692 and NCT00354458.).

Microvolt T-Wave Alternans Distinguishes Between Patients Likely and Patients Not Likely to Benefit From Implanted Cardiac Defibrillator Therapy A Solution to the Multicenter Automatic Defibrillator Implantation Trial (MADIT) II Conundrum

Background—In 2003, the Centers for Medicaid and Medicare Services recommended QRS duration as a means to identify MADIT II–like patients suitable for implanted cardiac defibrillator (ICD) therapy. We compared the ability of microvolt T-wave alternans and QRS duration to identify groups at high and low risk of dying among heart failure patients who met MADIT II criteria for ICD prophylaxis. Methods and Results—Patients with MADIT II characteristics and sinus rhythm had a microvolt T-wave alternans exercise test and a 12-lead ECG. Our primary end point was 2-year all-cause mortality. Of 177 MADIT II–like patients, 32% had a QRS duration >120 ms, and 68% had an abnormal (positive or indeterminate) microvolt T-wave alternans test. During an average follow-up of 20±6 months, 20 patients died. We compared patients with an abnormal microvolt T-wave alternans test to those with a normal (negative) test, and patients with a QRS >120 ms with those with a QRS ≤120 ms; the hazard ratios for 2-year mortality were 4.8 (P=0.020) and 1.5 (P=0.367), respectively. The actuarial mortality rate was substantially lower among patients with a normal microvolt T-wave alternans test (3.8%; 95% confidence interval: 0, 9.0) than the mortality rate in patients with a narrow QRS (12.0%; 95% confidence interval: 5.6, 18.5). The corresponding false-negative rates are 3.5% and 10.2%, respectively. Conclusion—Among MADIT II–like patients, a microvolt T-wave alternans test is better than QRS duration at identifying a high-risk group and also better at identifying a low-risk group unlikely to benefit from ICD therapy.

Effect of the cholesteryl ester transfer protein inhibitor, anacetrapib, on lipoproteins in patients with dyslipidaemia and on 24-h ambulatory blood pressure in healthy individuals: two double-blind, randomised placebo-controlled phase I studies

BACKGROUND The inhibition of cholesteryl ester transfer protein (CETP) is considered a potential new mechanism for treatment of dyslipidaemia. Anacetrapib (MK-0859) is a CETP inhibitor currently under development. We aimed to assess anacetrapibs effects as monotherapy on low-density lipoprotein cholesterol (LDL-C) and high-density lipoprotein cholesterol (HDL-C) and on 24-h ambulatory blood pressure. METHODS We did two double-blind, randomised, placebo-controlled phase I studies. In the first study, 50 patients with dyslipidaemia (LDL-C 100-190 mg/dL; 40 active, 10 placebo) aged 18-75 years received anacetrapib doses of 0, 10, 40, 150, or 300 mg orally once a day with a meal for 28 days. Standard lipid and lipoprotein monitoring, safety monitoring, and anacetrapib concentrations for pharmacokinetics were done. In the second study, 22 healthy participants aged 45-75 years received either 150 mg of anacetrapib once a day or matching placebo with a meal for 10 days in each crossover period, in a randomised sequence, with at least a 14-day washout between the treatment periods. Continuous 24-h ambulatory blood pressure monitoring was done on day -1 and day 10 of each treatment period in this study. The primary or secondary endpoints of safety and tolerability were assessed in both studies by monitoring clinical adverse experiences, physical examinations, vital signs, 12-lead electrocardiogram, and laboratory safety. Analysis was per protocol. These trials are registered with ClinicalTrials.gov, number NCT00565292 and NCT00565006. FINDINGS In the dyslipidaemia study, one patient withdrew consent and one was excluded from the data analysis for HDL-C and LDL-C because complete pre-dose measurements were not available. Anacetrapib produced dose-dependent lipid-altering effects with peak lipid-altering effects of 129% (mean 51.1 [SD 3.8]-114.9 [7.9] mg/dL) increase in HDL-C and a 38% (138.2 [11.4]-77.6 [7.9] mg/dL) decrease in LDL-C in patients with dyslipidaemia. In the 24-h ambulatory blood pressure study in healthy individuals, least squares difference between anacetrapib and placebo groups on day 10 were 0.60 (90% CI -1.54 to 2.74; p=0.634) mm Hg for systolic blood pressure and 0.47 (90% CI -0.90 to 1.84; p=0.561) mm Hg for diastolic blood pressure. INTERPRETATION Anacetrapib seems to exhibit HDL-C increases greater than those seen with other investigational drugs in this class and LDL-C lowering effects similar to statins. Despite greater lipid-altering effects relative to other members of this class, anacetrapib seems not to increase blood pressure, suggesting that potent CETP inhibition by itself might not lead to increased blood pressure.

Efficacy and safety of the cholesteryl ester transfer protein inhibitor anacetrapib as monotherapy and coadministered with atorvastatin in dyslipidemic patients.

BACKGROUND High-density lipoprotein cholesterol (HDL-C) levels are inversely associated with cardiovascular risk. Cholesteryl ester transfer protein inhibition is one strategy for increasing HDL-C. This study evaluated the lipid-altering efficacy and safety of the cholesteryl ester transfer protein inhibitor anacetrapib as monotherapy or coadministered with atorvastatin in patients with dyslipidemia. METHODS A total of 589 patients with primary hypercholesterolemia or mixed hyperlipidemia (53.8% of the study population had low HDL-C) were randomized equally to one of 10 groups: 5 groups received background statin therapy of atorvastatin 20 mg and 5 did not, and each of these was randomized to placebo, anacetrapib 10, 40, 150, and 300 mg once daily for 8 weeks. An equal proportion of patients had triglycerides >150 mg/dL in each group. RESULTS For placebo and anacetrapib monotherapy (10, 40, 150, and 300 mg), least squares mean percent changes from baseline to week 8 for low-density lipoprotein cholesterol (LDL-C) were 2%, -16%, -27%, -40%, and -39%, respectively, and for HDL-C were 4%, 44%, 86%, 139%, and 133%, respectively (P < .001 vs placebo for all doses). Coadministration of anacetrapib with atorvastatin produced significant incremental LDL-C reductions and similar HDL-C increases versus atorvastatin monotherapy. For both anacetrapib monotherapy and coadministration with atorvastatin, the LDL-C reductions were similar in patients with baseline triglyceride levels greater than and less than or equal to the median. Anacetrapib was well tolerated, and the incidence of adverse events was similar for placebo and all active treatment groups. There were no increases in systolic or diastolic blood pressure in any treatment arm. CONCLUSIONS Anacetrapib, as monotherapy or coadministered with atorvastatin, produced significant reductions in LDL-C and increases in HDL-C; the net result of treatment with anacetrapib + atorvastatin was approximately 70% lowering of LDL-C and more than doubling of HDL-C. Anacetrapib was generally well tolerated with no discernable effect on blood pressure.

Usefulness of microvolt T-wave alternans for prediction of ventricular tachyarrhythmic events in patients with dilated cardiomyopathy: results from a prospective observational study

OBJECTIVES This study was designed to evaluate the ability of microvolt-level T-wave alternans (MTWA) to identify prospectively patients with idiopathic dilated cardiomyopathy (DCM) at risk of ventricular tachyarrhythmic events and to compare its predictive accuracy with that of conventional risk stratifiers. BACKGROUND Patients with DCM are at increased risk of sudden death from ventricular tachyarrhythmias. At present, there are no established methods of assessing this risk. METHODS A total of 137 patients with DCM underwent risk stratification through assessment of MTWA, left ventricular ejection fraction, baroreflex sensitivity (BRS), heart rate variability, presence of nonsustained ventricular tachycardia (VT), signal-averaged electrocardiogram, and presence of intraventricular conduction defect. The study end point was either sudden death, resuscitated ventricular fibrillation, or documented hemodynamically unstable VT. RESULTS During an average follow-up of 14 +/- 6 months, MTWA and BRS were significant univariate predictors of ventricular tachyarrhythmic events (p < 0.035 and p < 0.015, respectively). Multivariate Cox regression analysis revealed that only MTWA was a significant predictor. CONCLUSIONS Microvolt-level T-wave alternans is a powerful independent predictor of ventricular tachyarrhythmic events in patients with DCM.

The PROTECT pilot study: a randomized, placebo-controlled, dose-finding study of the adenosine A1 receptor antagonist rolofylline in patients with acute heart failure and renal impairment.

BACKGROUND Rolofylline, an adenosine A(1) receptor antagonist, facilitates diuresis and preserves renal function in patients with acute heart failure (AHF) with renal impairment. Although not powered around any specific hypothesis, this pilot study was designed to identify an efficacious dose while refining inclusion criteria and end points. METHODS A total of 301 patients hospitalized for AHF with an estimated creatinine clearance of 20 to 80 mL/min and elevated natriuretic peptide levels were enrolled within 24 hours of presentation to placebo or rolofylline 10, 20, or 30 mg administered as 4-hour infusions for 3 days in addition to intravenously administered loop diuretics. Post hoc analyses for end points chosen for subsequent Phase III studies were performed. RESULTS Compared with placebo, rolofylline produced trends toward greater proportions of patients with marked or moderately improved dyspnea and fewer patients with worsening heart failure or renal function. Serum creatinine increased in patients receiving placebo and remained stable or tended to decrease in those receiving rolofylline. On day 14 the absolute differences between placebo and rolofylline for change in creatinine increased with increasing rolofylline dose, reflecting the lesser increase in creatinine in rolofylline-treated patients (r = -0.12, P = .030). Treatment with 30 mg, the dose selected for the pivotal trials, was associated with a trend toward reduced 60-day mortality or readmission for cardiovascular or renal cause (hazard ratio, 0.55; 95% confidence interval, 0.28-1.04). CONCLUSION These results demonstrate that adenosine A(1) receptor blockade with rolofylline can prevent renal impairment in patients with AHF and may positively affect acute symptoms and 60-day outcome. A 2000-patient trial of this agent is now under way.

Autonomic nervous system influences on QT interval in normal subjects

OBJECTIVES We sought to determine whether the relationship between heart rate (HR) and QT interval (QT) differs as HR increases in response to exercise, atropine and isoproterenol. BACKGROUND Autonomic nervous system influences on repolarization are poorly understood and may complicate the interpretation of QT measurements. METHODS Twenty-five normal subjects sequentially underwent graded-intensity bicycle exercise, atropine injection and isoproterenol infusion. Serial 12-lead electrocardiograms were recorded at steady state during each condition and analyzed using interactive computer software. The HR-QT data were modeled linearly and the slopes (quantifying QT adaptation to HR) as well as the QT intervals at 100 beats/min for each intervention were compared by repeated-measures analysis of variance. RESULTS As HR increased, QT was longer for isoproterenol in comparison to exercise or atropine, which were similar. The HR-QT slope (ms/beats/min) was less steep for isoproterenol (-0.83 +/- 0.53) than for atropine (-1.45 +/- 0.21) or exercise (-1.37 +/- 0.23) (p < 0.0001). In comparison to men, women had more negative HR-QT slopes during all interventions. At 100 beats/min, the QT was 364 ms during isoproterenol, which was significantly longer than that during exercise (330 ms) or atropine (339 ms) (p < 0.0001). Isoproterenol produced a dose-dependent increase in U-wave amplitude that was not observed during exercise or atropine. CONCLUSIONS In comparison to exercise and atropine, isoproterenol is associated with much less QT shortening for a given increase in HR and, therefore, greater absolute QT intervals. Our findings demonstrate that autonomic conditions directly affect the ventricular myocardium of healthy subjects, causing differences in QT that are independent of HR.

EXERCISE AND AUTONOMIC FUNCTION IN HEALTH AND CARDIOVASCULAR DISEASE

Autonomic nervous system activity contributes to the regulation of cardiac output during rest, exercise, and cardiovascular disease. Measurement of HRV has been particularly useful in assessing parasympathetic activity, while its utility for assessing sympathetic function and overall sympathovagal balance remains controversial. Studies have revealed that parasympathetic tone dominates the resting state, while exercise is associated with prompt withdrawal of vagal tone and subsequent sympathetic activation. Conversely, recovery is characterized by parasympathetic activation followed by sympathetic withdrawal, although clarification of the normal trajectory and autonomic basis of heart rate decay following exercise is needed. Abnormalities in autonomic physiology--especially increased sympathetic activity, attenuated vagal tone, and delayed heart rate recovery--have been associated with increased mortality. Exercise training is associated with a relative enhancement of vagal tone, improved heart rate recovery after exercise, and reduced morbidity in patients with cardiovascular disease. However, whether exercise training leads to reduced mortality in this population because of its ability to specifically modulate autonomic function is unknown at the present time. Although the results of a recent randomized study in patients with CHF and a meta-analysis in the setting of a recent myocardial infarction determined that exercise training leads to improved outcomes in these populations, neither study measured autonomic function. Improved autonomic function due to exercise training is a promising rationale for explaining improvements in outcome, although more research is needed to confirm this hypothesis.

The Effect of Moxifloxacin on QTc and Implications for the Design of Thorough QT Studies

A number of issues have remained unanswered in the design of “thorough QT” (TQT) studies. In this randomized, placebo‐controlled, two‐period crossover study in 20 healthy subjects, replicate electrocardiograms (ECGs) were recorded on a digital 12‐lead Holter recorder, extracted in a core ECG laboratory, and interpreted manually by a cardiologist. The observed within‐subject variability was slightly greater when time‐matched baselines were employed than when predose baselines were employed, whereas the magnitude of the increase in QTc was similar for both. Moxifloxacin 400 mg was associated with an observed 7.5–12.5 ms increase in the mean placebo‐ and baseline‐corrected QTc interval. A PK‐QTc model estimated a 3.9 ms increase in the QTc interval for every 1,000 ng/ml increase in moxifloxacin concentration. The QTc increases associated with moxifloxacin support the appropriateness of its use as a positive control in TQT studies. This crossover study failed to justify the use of time‐matched baselines rather than the less resource‐intensive predose definition of baseline.

Exercise and autonomic function.

The complex interplay between the dichotomous subdivisions of the autonomic nervous system establishes and maintains a delicately tuned homeostasis in spite of an ever‐changing environment. Aerobic exercise training can increase activity of the parasympathetic nervous system and decrease sympathetic activity. Conversely, it is well‐documented that cardiac disease is often characterized by attenuated parasympathetic activity and heightened sympathetic tone. A correlation between autonomic disequilibrium and disease has led to the hypothesis that exercise training, as a therapy that restores the autonomic nervous system towards normal function, may be associated with, and possibly responsible for, outcome improvements in various populations. This is merely one of the many benefits that is conferred by chronic exercise training and reviewed in this issue.