Post-myocardial infarction beta-blocker therapy: the bradycardia conundrum. Rationale and design for the Pacemaker & beta-blocker therapy post-MI (PACE-MI) trial

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.

Antianginal medications and long-term outcomes after elective catheterization in patients with coronary artery disease

BACKGROUND

Antianginal medications are a class I recommendation by the American College of Cardiology/American Heart Association guidelines for stable ischemic heart disease. We sought to better understand guidance in drug selection and real-life outcomes of antianginal medication use.

HYPOTHESIS

In patients with stable ischemic heart disease, antianginal medications lower mortality.

METHODS

We evaluated 5608 patients with obstructive coronary artery disease (CAD) on elective cardiac catheterization with follow-up through self-administered questionnaires. Patients were classified as being prescribed a particular medication if they received that medication at index catheterization, or within 3 months postcatheterization. The association between antianginal medication use and outcomes was evaluated using Cox proportional hazards models.

RESULTS

Compared with the 11% not prescribed any antianginal medication, patients prescribed antianginal medication were more likely to be older and female; have a history of hypertension, diabetes mellitus, peripheral vascular disease, or 3-vessel CAD; have lower adjusted mortality (hazard ratio [HR]: 0.75, 95% confidence interval [CI]: 0.63-0.89); and experience mortality or myocardial infarction (HR: 0.83, 95% CI: 0.71-0.98). Compared with patients not taking β-blockers (17%), those taking β-blockers had a lower risk of mortality (HR: 0.76, 95% CI: 0.66-0.88). Patients prescribed calcium channel blockers or long-acting nitrates had a higher risk of mortality compared with nonusers (HR: 1.16, 95% CI: 1.04-1.29; HR: 1.20, 95% CI: 1.08-1.34; respectively).

CONCLUSIONS

Antianginal medications are not universally prescribed among obstructive CAD patients; nonuse was associated with higher mortality. For CAD patients with or without prior myocardial infarction, β-blockers were associated with improved long-term survival.

Effect of Beta-Blocker Dose on Survival After Acute Myocardial Infarction

BACKGROUND

Beta-blocker therapy after acute myocardial infarction (MI) improves survival. Beta-blocker doses used in clinical practice are often substantially lower than those used in the randomized trials establishing their efficacy.

OBJECTIVES

This study evaluated the association of beta-blocker dose with survival after acute MI, hypothesizing that higher dose beta-blocker therapy will be associated with increased survival.

METHODS

A multicenter registry enrolled 7,057 consecutive patients with acute MI. Discharge beta-blocker dose was indexed to the target beta-blocker doses used in randomized clinical trials, grouped as >0% to 12.5%, >12.5% to 25%, >25% to 50%, and >50% of target dose. Follow-up vital status was assessed, with the primary endpoint of time-to-death right-censored at 2 years. Multivariable and propensity score analyses were used to account for group differences.

RESULTS

Of 6,682 patients with follow-up (median 2.1 years), 91.5% were discharged on a beta-blocker (mean dose 38.1% of the target dose). Lower mortality was observed with all beta-blocker doses (p < 0.0002) versus no beta-blocker therapy. After multivariable adjustment, hazard ratios for 2-year mortality compared with the >50% dose were 0.862 (95% confidence interval [CI]: 0.677 to 1.098), 0.799 (95% CI: 0.635 to 1.005), and 0.963 (95% CI: 0.765 to 1.213) for the >0% to 12.5%, >12.5% to 25%, and >25% to 50% of target dose groups, respectively. Multivariable analysis with an extended set of covariates and propensity score analysis also demonstrated that higher doses were not associated with better outcome.

CONCLUSIONS

These data do not demonstrate increased survival in patients treated with beta-blocker doses approximating those used in previous randomized clinical trials compared with lower doses. These findings provide the rationale to re-engage in research to establish appropriate beta-blocker dosing after MI to derive optimal benefit from this therapy. (The PACE-MI Registry Study-Outcomes of Beta-blocker Therapy After Myocardial Infarction [OBTAIN]: NCT00430612).

Influence of second- and third-degree heart block on 30-day outcome following acute myocardial infarction in the drug-eluting stent era

This study was conducted to investigate the prognostic value of heart block among patients with acute myocardial infarction (AMI) treated with drug-eluting stents. A total of 13,862 patients with AMI, registered in the nation-wide AMI database from January 2005 to June 2013, were analyzed. Second- (Mobitz type I or II) and third-degree atrioventricular block were considered as heart block in this study. Thirty-day major adverse cardiac events (MACE) including all causes of death, recurrent myocardial infarction, and revascularization were evaluated. Percutaneous coronary intervention with implantation of drug-eluting stent was performed in 89.8% of the patients. Heart block occurred in 378 patients (2.7%). Thirty-day MACE occurred in 1,144 patients (8.2%). Patients with heart block showed worse clinical parameters at initial admission, and the presence of heart block was associated with 30-day MACE in univariate analyses. However, the prognostic impact of heart block was not significant after adjustment of potential confounders (p = 0.489). Among patients with heart block, patients with a culprit in the left anterior descending (LAD) coronary artery had worse clinical outcomes than those of patients with a culprit in the left circumflex or right coronary artery. LAD culprit was a significant risk factor for 30-day MACE even after controlling for confounders (odds ratio 5.28, 95% confidence interval 1.22 to 22.81, p = 0.026). In conclusion, despite differences in clinical parameters at the initial admission, heart block was not an independent risk factor for 30-day MACE in adjusted analyses. However, a LAD culprit was an independent risk factor for 30-day MACE among patients with heart block.

Changes in under-treatment after comprehensive geriatric assessment: an observational study

BACKGROUND

Under-treatment is frequently present in geriatric patients. Because this patient group often suffer from multiple diseases, polypharmacy (defined as the concomitant chronic use of five or more drugs) and contraindications to indicated drugs may also frequently be present.

OBJECTIVE

To describe the prevalence of under-treatment with respect to frequently indicated medications before and after comprehensive geriatric assessment (CGA) and the prevalence of contraindications to these medications.

PATIENTS AND METHODS

The geriatric outpatients evaluated in this study had previously been included in a prospective descriptive study conducted in 2004. Demographic data, medical history, co-morbidity and medication use and changes were documented. The absence of drugs indicated for frequently under-treated conditions before and after CGA was compared. Under-treatment was defined as omission of drug therapy indicated for the treatment or prevention of 13 established diseases or conditions known to be frequently under-treated. Co-morbid conditions were independently classified by two geriatricians, who determined whether or not a condition represented a contraindication to use of these drugs.

RESULTS

In 2004, 807 geriatric outpatients were referred for CGA. Of these, 548 patients had at least one of the 13 selected diseases or conditions. Thirty-two of these patients were excluded from the analysis, leaving 516 patients. Before CGA, 170 of these patients were under-treated (32.9%); after CGA, 115 patients (22.3%) were under-treated. Contraindications were present in 102 of the patients (19.8%) and were more frequent in under-treated patients. After CGA, mean drug use and the prevalence of polypharmacy increased. Although 393 drugs were discontinued after CGA, the overall number of drugs used increased from 3177 before CGA to 3424 after CGA. Five times more drugs were initiated for a new diagnosis than for correction of under-treatment.

CONCLUSIONS

Under-treatment is significantly reduced after CGA. Patients with contraindications to indicated medicines are more frequently under-treated. CGA leads to an increase in polypharmacy, mainly because of new conditions being diagnosed and despite frequent discontinuation of medications.

Poor tolerance of beta-blockers by elderly patients with heart failure

Despite the well-understood importance of beta-blocker therapy in heart failure, it is sometimes not possible to use beta-blockers in elderly patients due to poor tolerance. In this report, we describe the case of an 83-year-old patient with severe systolic heart failure complicated by aortic valve stenosis and atrial fibrillation. A simple therapeutic approach involving discontinuation of beta-blockers remarkably alleviated the symptoms such as left ventricular ejection fraction, and improved the chest radiography and laboratory findings; further, atrial fibrillation converted to sinus rhythm. It is important to carefully administer beta-blocker therapy to elderly patients with heart failure, especially after considering cardiac output.

beta-Blocker use following myocardial infarction: low prevalence of evidence-based dosing

BACKGROUND

Quality improvement programs have shown increased use of beta-blockers post-myocardial infarction (MI), but there are no data on whether appropriate doses are administered.

METHODS

In a prospective registry that enrolled consecutive patients with MI, we evaluated beta-blocker dosing at discharge after MI and 3 weeks later and assessed clinical predictors for treatment with very low doses. We studied 1,971 patients (70.8% male) with a mean age of 63.9 +/- 13.7 years, of whom 48.2% had an ST-elevation MI.

RESULTS

beta-Blocker utilization rates following MI were 93.2% at discharge: 20.1% received <25% of target dose, 36.5% received 25% of target dose, 26.4% received 26% to 50% of target dose, and 17.0% received >50% of target dose. Between discharge and 3 weeks, 76.4% had no change in beta-blocker dose, with 11.9% and 11.6% having their dose reduced and increased, respectively. Absence of hypertension, acute percutaneous coronary intervention, older age, and no angiotensin-converting enzyme inhibitor therapy were consistent predictors of treatment with very low beta-blocker doses.

CONCLUSIONS

Underdosing of beta-blockers is highly prevalent among patients post-MI. This represents an important opportunity in quality improvement for the care of patients who have suffered an MI.