Prevention of suboptimal beta-blocker treatment in patients with myocardial infarction

β-blocker dosage and outcomes after acute coronary syndrome

BACKGROUND

Although β-blockers increase survival in acute coronary syndrome (ACS) patients, the doses used in trials were higher than doses used in practice, and recent data do not support an advantage of higher doses. We hypothesized that rates of major adverse cardiac events (MACE), all-cause death, myocardial infarction, and stroke are equivalent for patients on low-dose and high-dose β-blocker.

METHODS

Patients admitted to Intermountain Healthcare with ACS and diagnosed with ≥70% coronary stenosis between 1994 and 2013 were studied (N = 7,834). We classified low dose as ≤25% and high dose as ≥50% of an equivalent daily dose of 200 mg of metoprolol. Multivariate analyses were used to test association between low-dose versus high-dose β-blocker dosage and MACE at 0-6 months and 6-24 months.

RESULTS

A total of 5,287 ACS subjects were discharged on β-blockers (87% low dose, 12% high dose, and 1% intermediate dose). The 6-month MACE outcomes rates for the β-blocker dosage (low versus high) were not equivalent (P = .18) (hazard ratio [HR] = 0.76; 95% CI, 0.52-1.10). However, subjects on low-dose β-blocker therapy did have a significantly decreased risk of myocardial infarction for 0-6 months (HR = 0.53; 95% CI, 0.33-0.86). The rates of MACE events during the 6-24 months after presentation with ACS were equivalent for the 2 doses (P = .009; HR = 1.03 [95% CI, 0.70-1.50]).

CONCLUSIONS

In ACS patients, rates of MACE for high-dose and low-dose β-blocker doses are similar. These findings question the importance of achieving a high dose of β-blocker in ACS patients and highlight the need for further investigation of this clinical question.

Ensuring that Patients Receive Full Cardiac Pharmacotherapy Services: A Pharmacist's Call to Arms

While clinical trials have proven that use of certain cardiovascular drugs improves morbidity and mortality, these drugs are not widely used, they are by and large prescribed in suboptimal doses, and their benefit is further diminished by nonadherence. Pharmacists have the ability to improve the survival of patients with cardiovascular risks. This can only be accomplished through the efforts of the individual pharmacist and the further development of health-system management services. Pharmacists need to leverage their access to patients, their large patient base, and their knowledge of refill dates to improve patient care. Support and development of more pharmacist-directed anticoagulation, hyperlipidemia, and hypertension clinics are also needed.

Impact of an acute coronary syndrome pathway in achieving target heart rate and utilization of evidence-based doses of beta-blockers

Beta-blockers remain a cornerstone of therapy in the management of acute coronary syndrome (ACS). The 2007 American College of Cardiology/American Heart Association unstable angina/non-ST elevation myocardial infarction guideline revisions recommend a target heart rate (HR) of 50-60 beats per minute (bpm). Despite improved trends toward utilization of beta-blockers therapy, beta-blockers continue to be underdosed. Guideline-based tools have been shown to improve adherence to evidence-based therapy in patients with ACS. Implementation of a standardized ACS pathway would lead to titration of beta-blockers to recommended dosages with improved HRs in eligible patients. The ACS clinical protocol was implemented at the University of Toledo Medical Center in May 2007. A retrospective study of 516 patients admitted during a comparable 6-month period, before and after the institution of the protocol, was conducted. The preprotocol and protocol group included 237 and 279 patients, respectively. Patient information extracted from the medical records included age, gender, HR on admission, blood pressure on admission, duration of hospital stay, preadmission use of beta-blocker, type of beta-blocker and dosage, discharge beta-blocker and dosage, peak troponin levels, and therapeutic intervention. A target HR of less than 60 bpm was achieved in 19% of the protocol group, as compared with 6% in the preprotocol group (P < 0.001). The protocol group had a significantly lower mean discharge HR than the preprotocol group (67 vs. 74 bpm; P < 0.001). The mean discharge dose of metoprolol in the protocol group was noted to be significantly higher (118 vs. 80 mg/d; P < 0.001). The institution of an ACS clinical pathway led to utilization of beta-blockers in significantly higher dosages, resulting in improved HR control and increased attainment of target HR.

The Impact of Catecholamines on Defibrillation Threshold in Patients with Implanted Cardioverter Defibrillators

OBJECTIVES

To determine the effect of physiologic catecholamine concentrations on the defibrillation threshold (DFT) in patients with implanted cardioverter defibrillators.

BACKGROUND

DFT is the minimum energy delivered by an implanted cardioverter defibrillator that successfully converts ventricular fibrillation. DFT testing is performed under conscious sedation. Since activities of daily living enhance sympathetic tone substantially over these nadir levels, it is important to explore the impact of catecholamines on DFT.

METHODS

In this double-blind study, we determined DFT by the step-down method. Patients (n = 50) were stratified by beta-blocker use and then randomized to a 7-minute infusion of epinephrine, norepinephrine, or placebo. After study infusion, DFT testing was repeated. Changes in DFT with different study medications were compared. Subgroup analyses of the effects of catecholamines on DFT, based on beta-blocker use, were also performed.

RESULTS

Norepinephrine reduced DFT from baseline measurements by 22.6% (P = 0.008). Neither epinephrine nor placebo impacted DFT (P = 0.999, P = 0.317, respectively). In the subgroup analyses, DFT was reduced with norepinephrine regardless of beta-blocker use, while epinephrine reduced DFT among those receiving beta-blockers. No change in DFT was observed in either of the placebo subgroups.

CONCLUSIONS

Elevation of plasma norepinephrine concentrations reduces the DFT, while elevations in epinephrine had no effect. Norepinephrine seems to reduce DFT regardless of beta-blocker therapy but epinephrine's effects are beta-blocker dependent.

Anemia Management in Heart Failure: A Thick Review of Thin Data

Heart failure is defined as the inability of the heart to pump blood at an amount sufficient to meet the metabolic needs of the body. In heart failure, the inability to meet the body's metabolic needs is based on hemodynamic derangement and suboptimal oxygen-carrying capacity of the blood itself. Current pharmacologic therapy attempts to improve survival and reduce symptomatology by optimizing hemodynamics to increase oxygen delivery, but does not address oxygen-carrying capacity. Unfortunately, there is a high prevalence of anemia in patients with heart failure, which compromises oxygen-carrying capacity, is an independent predictor of mortality, and may be caused in part by pharmacologic agents that confer morbidity and mortality benefits in this population. Recombinant human erythropoietin supplementation improves the functional capacity of the failing myocardium, reverses and antagonizes the detrimental remodeling induced by autoimmune activity, and may reduce mortality and morbidity among patients receiving maximal pharmacologic therapy for heart failure. However, limited clinical data prohibit widespread recommendations for its use in patients with heart failure.

Life-years gained from coronary heart disease mortality reduction in Scotland: prevention or treatment?

Coronary Heart Disease (CHD) death rates have fallen considerably in many countries. We estimated the life-years-gained (LYG) in Scotland between 1975 and 1994 attributable to cardiology treatments, and population reductions in major CHD risk factors, using a previously validated mortality model. This combines published effectiveness data with information on uptake of CHD treatments; risk factor trends; and median survival by age and sex. Compared with 1975, there were 4,536 fewer CHD deaths in 1994, resulting in approximately 48,016 LYG among those aged 45-84 (maximum estimate 53,317; minimum estimate 36,867). Medical and surgical treatments for CHD patients gained approximately 12,025 life-years; the largest contribution coming from pharmacologic secondary prevention. Population reductions in major risk factors (smoking, cholesterol, and blood pressure) accounted for some 35,991 LYG, reductions in smoking accounted for over 50% of this. Modern cardiologic treatments gained many thousands of life-years in Scotland, but modest reductions in risk factors gained almost three times as many life-years.

Effect of intravenous metoprolol or intravenous metoprolol plus glucagon on dobutamine-induced myocardial ischemia

STUDY OBJECTIVE

To determine the effect of metoprolol on dobutamine stress testing with technetium-99m sestamibi single-photon emission computed tomography imaging and ST-segment monitoring, and to assess the impact of intravenous glucagon on metoprolol's effects.

DESIGN

Randomized, double-blind, placebo-controlled trial.

SETTING

Community hospital.

PATIENTS

Twenty-two patients with known reversible perfusion defects.

INTERVENTION

Patients underwent dobutamine stress tests per standard protocol. Before dobutamine was begun, no therapy was given during the first visit, and patients were randomized on subsequent visits to receive metoprolol or metoprolol plus glucagon 1 mg. Metoprolol was dosed to achieve a resting predobutamine heart rate below 65 beats/minute or a total intravenous dose of 20 mg.

MEASUREMENTS AND MAIN RESULTS

Metoprolol reduced maximum heart rate 31%, summed stress scores 29%, and summed difference scores 43% versus control. Metoprolol plus glucagon also reduced the maximum heart rate 29% versus control. Summed stress and summed difference scores were not significantly reduced, although they were 18% and 30% lower, respectively, than control. No significant differences were found in any parameter between metoprolol and metoprolol-glucagon.

CONCLUSION

During dobutamine stress testing, metoprolol attenuates or eliminates evidence of myocardial ischemia. Glucagon 1 mg, although somewhat effective, does not correct this effect to the extent that it can be administered clinically.