Type of β-blocker use among patients with versus without diabetes after myocardial infarction

Impact of Diabetes Mellitus on Benefit of β-Blocker Therapy After Myocardial Infarction

Beta blockers are uniformly recommended for all patients after myocardial infarction (MI), including those with diabetes mellitus (DM). This study assesses the impact of β-blocker type and dosing on survival in patients with DM after MI. A cohort of 6,682 patients in the Outcomes of Beta-blocker Therapy After Myocardial INfarction registry were discharged after MI. In this cohort, 2,137 patients had DM (32%). Beta-blocker dose was indexed to the target daily dose used in randomized clinical trials and reported as percentage. Dosage groups were: no β blocker, >0% to 12.5%, >12.5% to 25%, >25% to 50%, and >50% of the target dose. The overall mean discharge β-blocker dose in patients with DM was 42.7 ± 34.1% versus 35.9 ± 27.4% in patients without DM (p <0.0001). Patients with DM were prescribed carvedilol at a higher rate than those without DM (27.8% vs 19.6%). The 3-year mortality estimates were 24.4% and 12.8% for patients with DM versus without DM (p <0.0001), respectively, with an unadjusted hazard ratio = 1.820 (confidence interval 1.587 to 2.086, p <0.0001). Patients with DM in the >12.5% to 25% dose category had the highest survival rates, whereas patients in the >50% dose had the lowest survival rate among patients discharged on β blockers (p <0.0001). In the multivariable analysis among patients with DM after MI, all β-blocker dose categories demonstrated lower mortality than no therapy; however, only the >12.5% to 25% dose had a statistically significant hazard ratio 0.450 (95% confidence interval 0.224 to 0.907, p = 0.025). In patients with DM, there was no statistically significant difference in 3-year mortality among those treated with metoprolol versus carvedilol. In conclusion, our analysis in patients with DM after MI suggested a survival benefit from β-blocker therapy, with no apparent advantage to high- versus low-dose β-blocker therapy; although, physicians tended to prescribe higher doses in patients with DM. There was no survival benefit for carvedilol over metoprolol in patients with DM.

Cardiac cAMP-PKA Signaling Compartmentalization in Myocardial Infarction

Under physiological conditions, cAMP signaling plays a key role in the regulation of cardiac function. Activation of this intracellular signaling pathway mirrors cardiomyocyte adaptation to various extracellular stimuli. Extracellular ligand binding to seven-transmembrane receptors (also known as GPCRs) with G proteins and adenylyl cyclases (ACs) modulate the intracellular cAMP content. Subsequently, this second messenger triggers activation of specific intracellular downstream effectors that ensure a proper cellular response. Therefore, it is essential for the cell to keep the cAMP signaling highly regulated in space and time. The temporal regulation depends on the activity of ACs and phosphodiesterases. By scaffolding key components of the cAMP signaling machinery, A-kinase anchoring proteins (AKAPs) coordinate both the spatial and temporal regulation. Myocardial infarction is one of the major causes of death in industrialized countries and is characterized by a prolonged cardiac ischemia. This leads to irreversible cardiomyocyte death and impairs cardiac function. Regardless of its causes, a chronic activation of cardiac cAMP signaling is established to compensate this loss. While this adaptation is primarily beneficial for contractile function, it turns out, in the long run, to be deleterious. This review compiles current knowledge about cardiac cAMP compartmentalization under physiological conditions and post-myocardial infarction when it appears to be profoundly impaired.

Metoprolol and bisoprolol ameliorate hypertrophy of neonatal rat cardiomyocytes induced by high glucose via the PKC/NF-κB/c-fos signaling pathway

Hyperglycemia caused by diabetes mellitus could increase the risk of diabetic cardiomyopathy. However, to the best of our knowledge, the underlying mechanism of this process is still not fully explored. Thus, developing ways to prevent hyperglycemia can be beneficial for diabetic patients. The present study was designed to investigate the influence of metoprolol and bisoprolol on the cardiomyocytic hypertrophy of neonatal rat cardiomyocytes. Cardiomyocytes were cultured in two types of media: One with low glucose levels and one with high glucose levels. Cardiomyocytes cultured in high glucose were further treated with the following: A protein kinase C (PKC) inhibitor, an NF-κB inhibitor, metoprolol or bisoprolol. The pulsatile frequency, cellular diameter and surface area of cardiomyocytes were measured. Protein content and [³H]-leucine incorporation were determined, atrial natriuretic peptide (ANP), α-myosin heavy chain (α-MHC) and β-myosin heavy chain (β-MHC) mRNA levels were calculated by reverse transcription-quantitative PCR, while the expression and activation of PKC-α, PKC-β₂, NF-κB, tumor necrosis factor-α (TNF-α), and c-fos were detected by western blotting. Metoprolol or bisoprolol were also used in combination with PKC inhibitor or NF-κB inhibitor to determine whether the hypertrophic response would be attenuated to a lower extent compared with metroprolol or bisoprolol alone. Cardiomyocytes cultured in high glucose presented increased pulsatile frequency, cellular diameter, surface area, and protein content and synthesis, higher expression of ANP and β-MHC, and lower α-MHC expression. High glucose levels also upregulated the expression and activation of PKC-α, PKC-β₂, NF-κB, TNF-α and c-fos. Metoprolol and bisoprolol partly reversed the above changes, while combined use of metoprolol or bisoprolol with PKC inhibitor or NF-κB inhibitor further ameliorated the hypertrophic response mentioned above to lower levels compared with using metroprolol or bisoprolol alone. In conclusion, metoprolol and bisoprolol could prevent hypertrophy of cardiomyocytes cultured in high glucose by the inhibition of the total and phospho-PKC-α, which could further influence the PKC-α/NF-κB/c-fos signaling pathway.

Outcomes of "diabetes-friendly" vs "diabetes-unfriendly" β-blockers in older nursing home residents with diabetes after acute myocardial infarction

AIMS

To assess whether nursing home (NH) residents with type 2 diabetes mellitus (T2D) preferentially received "T2D-friendly" (vs "T2D-unfriendly") β-blockers after acute myocardial infarction (AMI), and to evaluate the comparative effects of the two groups of β-blockers.

MATERIALS AND METHODS

This new-user retrospective cohort study of NH residents with AMI from May 2007 to March 2010 used national data from the Minimum Data Set and Medicare system. T2D-friendly β-blockers were those hypothesized to increase peripheral glucose uptake through vasodilation: carvedilol, nebivolol and labetalol. Primary outcomes were hospitalizations for hypoglycaemia and hyperglycaemia in the 90 days after AMI. Secondary outcomes were functional decline, death, all-cause re-hospitalization and fracture hospitalization. We compared outcomes using binomial and multinomial logistic regression models after propensity score matching.

RESULTS

Of 2855 NH residents with T2D, 29% initiated a T2D-friendly β-blocker vs 24% of 6098 without T2D (P < 0.001). For primary outcomes among residents with T2D, T2D-friendly vs T2D-unfriendly β-blockers were associated with a reduction in hospitalized hyperglycaemia (odds ratio [OR] 0.45, 95% confidence interval [CI] 0.21-0.97), but unassociated with hypoglycaemia (OR 2.05, 95% CI 0.82-5.10). For secondary outcomes, T2D-friendly β-blockers were associated with a greater rate of re-hospitalization (OR 1.26, 95% CI 1.01-1.57), but not death (OR 1.06, 95% CI 0.85-1.32), functional decline (OR 0.91, 95% CI 0.70-1.19), or fracture (OR 1.69, 95% CI 0.40-7.08).

CONCLUSIONS

In older NH residents with T2D, T2D-friendly β-blocker use was associated with a lower rate of hospitalization for hyperglycaemia, but a higher rate of all-cause re-hospitalization.

THE IMPACT OF CARDIOVASCULAR DRUGS ON GLYCEMIC CONTROL: A REVIEW

OBJECTIVE

The prevalence of diabetes mellitus (DM) is steadily rising in the U.S., both in the general population and among those with cardiovascular disease (CVD). Understanding how to treat a patient with both conditions is becoming increasingly important. With multiple therapeutic options for CVD management, some medications will invariably impact glycemia in this group of patients. The concept of "DM-friendly" management of CVD is based on a treatment approach of selecting medications that do not impair glycemic control and provide equivalent cardioprotective effects. This article reviews the glycemic effects of various classes of medications commonly used to treat CVD.

METHODS

Data sources were all PubMed- and Google Scholar-referenced articles in English-language peer-reviewed journals from 1980 through April 2016. Studies selected could include observational studies or prospective clinical trials. Prospective clinical trials included in this review focused on investigating the association of the medication of interest with glycemic outcomes. Meta-analyses and systematic reviews were also included.

RESULTS

The data on glycemic effects were lacking for many of the medication classes and individual medications examined. However, in our review, certain beta-blockers and renin angiotensin aldosterone system inhibitors, and select calcium channel blockers were consistently shown to have favorable glycometabolic profiles when compared with other commonly used cardiovascular therapies.

CONCLUSION

Several commonly prescribed medications for the treatment of CVD, such as certain beta-blockers and renin angiotensin aldosterone system inhibiting agents, are associated with favorable glycometabolic effects. As clinicians are more often faced with the challenge of treating patients with DM and concomitant CVD, consideration of how common cardiovascular medications may affect glycemia should be incorporated into the clinical decision making process.

ABBREVIATIONS

A1C = hemoglobin A1C ACE = angiotensin-converting enzyme ARB = angiotensin II receptor blocker CCB = calcium channel blocker CI = confidence interval CVD = cardiovascular disease DM = diabetes mellitus MI = myocardial infarction RR = relative risk.

Predictors of β-Blocker Initiation After Myocardial Infarction in Patients With Type 2 Diabetes

Background: Beta-blockers remain important for secondary prevention after myocardial infarction (MI). Despite clinical guideline recommendations, underutilization of this pharmacotherapy continues in patients with type 2 diabetes (T2DM) compared to the general post-MI population. Objective: This study aimed to (1) quantify the proportion of T2DM patients utilizing β-blocker therapy within 30 days of hospital discharge after MI and (2) identify clinical and demographic characteristics predicting initiation of β-blocker therapy. Methods: A retrospective cohort of US employed, commercially insured individuals was assembled using de-identified enrollment files, medical claims, and pharmacy claims from 2007 to 2009. Inclusion criteria were the following: (1) type 2 diabetes, (2) ≥18 years old, (3) continuous eligibility, (4) MI. Multivariable logistic regression with adjusted odds ratios (ORadj) using manual backward elimination was used to identify predictors of β-blocker initiation within 30 days of discharge from index hospitalization. Results: Of 341 T2DM patients, 167 (49.0%) were new users and 174 (51.0%) were nonusers of β-blockers within 30 days of post-MI hospital discharge. Patients on a calcium channel blocker (ORadj 2.63) and patients taking 1 to 5 medications (ORadj 3.59) were more likely to initiate β-blockers post-MI. Patients with heart failure (ORadj 0.45) or an arrhythmia (ORadj 0.44) were less likely to initiate β-blockers as well as patients with renal failure not taking a diuretic (ORadj 0.17). Conclusions: These results confirm previous findings that β-blockers are underutilized in T2DM patients post-MI. Predictors from the regression model can guide future research investigating how this deviation from guidelines is attributed to prescriber versus patient behavior.

Recognition of incident diabetes mellitus during an acute myocardial infarction

BACKGROUND

Diabetes mellitus (DM) is common in patients hospitalized with an acute myocardial infarction (AMI), representing in some cases the first opportunity to recognize and treat DM. We report the incidence of new DM and its recognition among patients with AMI.

METHODS AND RESULTS

Patients in a 24-site US AMI registry (2005-08) had glycosylated hemoglobin assessed at a core laboratory, with results blinded to clinicians and local clinical measurements left to the discretion of the treating providers. Among 2854 AMI patients without known DM on admission, 287 patients (10%) met criteria for previously unknown DM, defined by a core laboratory glycosylated hemoglobin of ≥6.5%. Among these, 186 (65%) were unrecognized by treating clinicians, receiving neither DM education, glucose-lowering medications at discharge, nor documentation of DM in the chart (median glycosylated hemoglobin of unrecognized patients, 6.7%; range, 6.5-12.3%). Six months after discharge, only 5% of those not recognized as having DM during hospitalization had been initiated on glucose-lowering medications versus 66% of those recognized (P<0.001).

CONCLUSIONS

Underlying DM that has not been previously diagnosed is common among AMI patients, affecting 1 in 10 patients, yet is recognized by the care team only one third of the time. Given its frequency and therapeutic implications, including but extending beyond the initiation of glucose-lowering treatment, consideration should be given to screening all AMI patients for DM during hospitalization. Inexpensive, ubiquitous, and endorsed as an acceptable screen for DM, glycosylated hemoglobin testing should be considered for this purpose.