Carvedilol Versus Metoprolol in the Acute Phase of Myocardial Infarction:. Differing Effects on Heart Rate Turbulence

HRT assessment reviewed: a systematic review of heart rate turbulence methodology

Heart rate turbulence (HRT) is a biphasic reaction to a ventricular premature contraction (VPC) mainly mediated by the baroreflex. It can be used for risk stratification in different disease patterns. Despite existing standards there is a lot of variation in terms of measuring and calculating HRT, which complicates research and application.

OBJECTIVE

This systematic review outlines and evaluates the methodological spectrum of HRT research, especially filtering criteria, parameter calculation and thresholds.

APPROACH

The analysis includes all research papers written in English that have been published before 12.10.2018, are listed on PubMed and involve calculation of HRT parameter values.

MAIN RESULTS

HRT assessment is still being performed in various ways and important specifications of the methodology are not given in many articles. Nevertheless, some suggestions regarding HRT methodology can be made: a normalised turbulence slope should be used to uncouple the parameter from heart rate and frequency of extrasystoles. Filtering criteria as formerly reviewed in the guidelines should be met and mentioned. The minimal number of VPC snippets (VPCSs) as well as new cut-off values for different risks need to be further evaluated. Most importantly, the exact and complete methodology must be described to ensure reproducibility and comparability.

SIGNIFICANCE

Methodical variation hinders comparability of research and medical application. Our continuing questions help to further standardise the measurement and calculation of HRT and increase its value for medical risk stratification.

Comparison of Pyrroloquinoline Quinone and/or Metoprolol on Myocardial Infarct Size and Mitochondrial Damage in a Rat Model of Ischemia/Reperfusion Injury

The cardioprotective effectiveness of low-dose pyrroloquinoline quinone (PQQ, 3 mg/kg) was compared with metoprolol, a β1-selective adrenoceptor antagonist. Rats underwent 30 minutes of left anterior descending coronary artery occlusion and 2 hours of reperfusion. Metoprolol and/or PQQ were given at the onset of reperfusion to mimic clinical treatment. Metoprolol and/or PQQ reduced infarct size and protected against ischemia-induced left ventricular dysfunction after 2 hours of reper-fusion. Combined therapy augmented left ventricular developed pressure at the end of reperfusion. Metoprolol or PQQ alone enhanced mitochondrial respiratory ratios in ischemic and nonischemic myocardium. Although the PQQ/metoprolol combination therapy increased respiratory ratio values, the effects were small when compared with PQQ alone. Only PQQ decreased lipid peroxidation. Metoprolol and/or PQQ given at the onset of reperfusion reduce infarct size and improve cardiac function. Combination therapy further reduces infarct size. PQQ is superior to metoprolol in protecting mitochondria from ischemia/reperfusion oxidative damage

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

BACKGROUND

Discharge β-blocker prescription after myocardial infarction (MI) is recommended for all eligible patients. Numerous β-blocker choices are presently available with variable glycometabolic effects, which could be an important consideration in patients with diabetes mellitus (DM). Whether patients with DM preferentially receive β-blockers with favorable metabolic effects after MI and if this choice is associated with better glycemic control postdischarge is unknown.

METHODS

Among patients from 24 US hospitals enrolled in an MI registry (2005-2008), we investigated the frequency of "DM-friendly" β-blocker prescription at discharge by DM status. β-Blockers were classified as DM-friendly (eg, carvedilol and labetalol) or non-DM-friendly (eg, metoprolol and atenolol), based on their effects on glycemic control. Hierarchical, multivariable logistic regression examined the association of DM with DM-friendly β-blocker use. Among DM patients, we examined the association of DM-friendly β-blockers with worsened glycemic control at 6 months after MI.

RESULTS

Of 4,031 MI patients, 1,382 (34%) had DM. β-Blockers were prescribed at discharge in 93% of patients. Diabetes mellitus-friendly β-blocker use was low regardless of DM status, although patients with DM were more likely to be discharged on a DM-friendly β-blocker compared with patients without DM (13.5% vs 10.3%, P = .003), an association that remained after multivariable adjustment (odds ratio 1.41, 95% CI 1.13-1.77). There was a trend toward a lower risk of worsened glucose control at 6 months in DM patients prescribed DM-friendly versus non-DM-friendly β-blockers (Relative Risk 0.80, 95% CI 0.60-1.08).

CONCLUSION

Most DM patients were prescribed non-DM-friendly β-blockers-a practice that was associated with a trend toward worse glycemic control postdischarge. Although in need of further confirmation in larger studies, our findings highlight an opportunity to improve current practices of β-blockers use in patients with DM.

Heart rate turbulence: standards of measurement, physiological interpretation, and clinical use: International Society for Holter and Noninvasive Electrophysiology Consensus

This consensus statement has been compiled on behalf of the International Society for Holter and Noninvasive Electrophysiology. It reviews the topic of heart rate turbulence (HRT) and concentrates on technologies for measurement, physiologic background and interpretation, and clinical use of HRT. It also lists suggestions for future research. The phenomenon of HRT refers to sinus rhythm cycle-length perturbations after isolated premature ventricular complexes. The physiologic pattern of HRT consists of brief heart rate acceleration (quantified by the so-called turbulence onset) followed by more gradual heart rate deceleration (quantified by the so-called turbulence slope) before the rate returns to a pre-ectopic level. Available physiologic investigations confirm that the initial heart rate acceleration is triggered by transient vagal inhibition in response to the missed baroreflex afferent input caused by hemodynamically inefficient ventricular contraction. A sympathetically mediated overshoot of arterial pressure is responsible for the subsequent heart rate deceleration through vagal recruitment. Hence, the HRT pattern is blunted in patients with reduced baroreflex. The HRT pattern is influenced by a number of factors, provocations, treatments, and pathologies reviewed in this consensus. As HRT measurement provides an indirect assessment of baroreflex, it is useful in those clinical situations that benefit from baroreflex evaluation. The HRT evaluation has thus been found appropriate in risk stratification after acute myocardial infarction, risk prediction, and monitoring of disease progression in heart failure, as well as in several other pathologies.