Lipophilic versus hydrophilic beta(1) blockers and the cardiac sympatho-vagal balance during stress and daily activity in patients after acute myocardial infarction

Effect of propranolol on heart rate variability in hyperthyroidism

Objectives

We aimed to determine the effect of propanolol on heart rate variability (HRV) in hyperthyroidism before antithyroid treatment. This was a before and after study, on ten patients presenting overt hyperthyroidism naïve to treatment. In each patient, a resting electrocardiogram was done followed by estimation of cardiac autonomic dysfunction during five maneuvers (Ewing battery tests). Long term HRV measurement was done using 24 h ambulatory electrocardiographic recording. This automatically provided estimation of HRV using SDNN and RMSSD index, LF, HF, and HF/LF ratio. After baseline investigations, 40 mg of propanolol was given twice a day for 3 days and same parameters were measured after 72 h of treatment.

Results

Our patients were aged 40 ± 10 years. Propanolol significantly reduced RR and HR interval (669 ms vs 763 ms and 91 vs 79 bpm; p < 0.01). QT and PR space were significantly extended (360 vs 384 ms and 133 vs 172 ms; p = 0.01). It increases QRS complex and blood pressure response to sustained handgrip but failed to modify previously decreased heart response to deep breathing. HRV parameters such as SDNN, RMSSD, LF, HF and sympathovagal balance estimate by HF/LF ratio remained unchanged. Although a significant reduction in heart excitability, propanolol failed to restore a good sympathovagal balance in hyperthyroidism.

Trial registration NCT03393728 “Retrospectively registered”

Potential of biochar filters for onsite sewage treatment: Adsorption and biological degradation of pharmaceuticals in laboratory filters with active, inactive and no biofilm

This study investigated the potential of biochar filters as a replacement or complement for sand filters for removal of pharmaceutically active compounds (PhACs) from wastewater in onsite sewage facilities (OSSF). Specifically, the study investigated the effects of biodegradation, adsorption and a combination of these processes on removal of four model PhACs from wastewater in biochar filters operated under hydraulic loading conditions mimicking those found in onsite infiltration beds. Concentrations and removal of the four PhACs (i.e. carbamazepine, metoprolol, ranitidine and caffeine) were investigated over 22weeks in four treatments: biochar (BC) with active or inactive biofilm (BC-active-biofilm, BC-inactive-biofilm), biochar without biofilm (BC-no-biofilm) and sand with active biofilm (Sand-active-biofilm). The adsorption of carbamazepine was high in BC-no-biofilm (99% removal after 22weeks), while biodegradation was very low in Sand-active-biofilm (7% removal after 22weeks). Removal of carbamazepine in BC-active-biofilm was high and stable over the 22weeks (>98%), showing a significant role of biofilm in filter biogeneration. However, carbamazepine removal declined over time in BC-inactive-biofilm, from 99% in week 13 to 73% in week 22. Metoprolol was poorly degraded in Sand-active-biofilm (37% after 22weeks), while adsorption seemed to be the major pathway for removal of metoprolol in biochar. Ranitidine and caffeine were efficiently removed by either adsorption (97% and 98%, respectively, after 22weeks) or biodegradation (99% and >99%, respectively, after 22weeks). In conclusion, biochar is a promising filter medium for OSSF, especially for persistent PhACs such as carbamazepine and metoprolol.

Pilot study of the effect of lipophilic vs. hydrophilic beta-adrenergic blockers being taken at time of intracardiac defibrillator discharge on subsequent PTSD symptoms

A pathophysiological model of posttraumatic stress disorder (PTSD) posits that an overly strong stress response at the time of the traumatic event leads to overconsolidation of the event's memory in part through a central β-adrenergic mechanism. We hypothesized that the presence of a β-blocker in the patient's brain at the time of the traumatic event would reduce the PTSD outcome by blocking this effect. The unpredictable, uncontrollable discharge of an implantable intracardiac defibrillator (ICD) is experienced by most patients as highly stressful, and it has previously been shown to be capable of causing PTSD symptoms. The present pilot study evaluated a convenience sample of 18 male cardiac patients who had been taking either a lipophilic β-blocker (which penetrates the blood-brain barrier) or a hydrophilic β-blocker (which does not) at the time of a discharge of their ICD. The self- report PTSD Checklist-Specific Version quantified 17 PTSD symptoms pertaining to the ICD discharge during the month preceding the evaluation. There was a statistical trend for patients who had been taking a lipophilic β-blocker at the time of the ICD discharge to have (35%) less severe PTSD symptoms than patients who had been taking a hydrophilic β-blocker (one-tailed p=0.07, g=0.64). Further, prospective, randomized, controlled studies are suggested.

Atenolol is associated with lower day-of-surgery heart rate compared to long- and short-acting metoprolol

OBJECTIVES

The authors analyzed the association between outpatient β-blocker type and day-of-surgery (DOS) heart rate in ambulatory surgical patients. They further investigated whether differences in DOS heart rate between atenolol and metoprolol could be explained by once-daily versus twice-daily dosing regimens.

DESIGN

Retrospective observational study.

SETTING

Veterans Administration hospital.

PARTICIPANTS

Ambulatory surgical patients on long-term atenolol or metoprolol.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Using a propensity-score-matched cohort, DOS heart rates were compared in patients prescribed atenolol versus metoprolol. Then, once-daily and twice-daily metoprolol formulations were differentiated and DOS heart rates were compared within a general linear model. DOS heart rates in patients prescribed atenolol versus any metoprolol formulation were slower by a mean of 5.1 beats/min (66.6 v 71.7; 95% confidence interval [CI] of difference, 1.9-8.3; p = 0.002), a difference that was not observed in preoperative primary care visits. The general linear model showed that patients prescribed atenolol (typically once-daily dosing) had a mean DOS heart rate 5.6 beats/min lower compared with patients prescribed once-daily metoprolol succinate (68.9 v 74.5; 95% CI of difference, -8.6 to -2.6; p < 0.001) and 3.8 beats/min lower compared with patients prescribed twice-daily metoprolol tartrate (68.9 v 72.7; 95% CI of difference, -6.1 to -1.6; p < 0.001). DOS heart rates were similar between different formulations of metoprolol (95% CI of difference, -1.0 to +4.6; p = 0.22).

CONCLUSIONS

Atenolol is associated with a lower DOS heart rate versus metoprolol. The heart rate difference is specific to the day of surgery and is not explained by once-daily versus twice-daily dosing regimens.

Baroreflex sensitivity is higher during acute psychological stress in healthy subjects under β-adrenergic blockade

Acute psychological stress challenges the cardiovascular system with an increase in BP (blood pressure), HR (heart rate) and reduced BRS (baroreflex sensitivity). β-adrenergic blockade enhances BRS during rest, but its effect on BRS during acute psychological stress is unknown. This study tested the hypothesis that BRS is higher during acute psychological stress in healthy subjects under β-adrenergic blockade. Twenty healthy novice male bungee jumpers were randomized and studied with (PROP, n=10) or without (CTRL, n=10) propranolol. BP and HR responses and BRS [cross-correlation time-domain (BRSTD) and cross-spectral frequency-domain (BRSFD) analysis] were evaluated from 30 min prior up to 2 h after the jump. HR, cardiac output and pulse pressure were lower in the PROP group throughout the study. Prior to the bungee jump, BRS was higher in the PROP group compared with the CTRL group [BRSTD: 28 (24-42) compared with 17 (16-28) ms·mmHg-1, P<0.05; BRSFD: 27 (20-34) compared with 14 (9-19) ms·mmHg-1, P<0.05; values are medians (interquartile range)]. BP declined after the jump in both groups, and post-jump BRS did not differ between the groups. In conclusion, during acute psychological stress, BRS is higher in healthy subjects treated with non-selective β-adrenergic blockade with significantly lower HR but comparable BP.

Atenolol is inferior to metoprolol in improving left ventricular function and preventing ventricular remodeling in dogs with heart failure

OBJECTIVES

beta-Blockers are standard therapy for patients with heart failure (HF). This study compared the effects of chronic monotherapy with 2 different beta(1)-selective adrenoceptor blockers, namely atenolol and metoprolol succinate, on left ventricular (LV) function and remodeling in dogs with coronary microembolization-induced HF [LV ejection fraction (EF) 30-40%].

METHODS

Twenty HF dogs were randomized to 3 months of therapy with atenolol (50 mg once daily, n = 6), metoprolol succinate (100 mg, once daily, n = 7) or to no therapy (control, n = 7). LV EF and volumes were measured before initiating therapy and after 3 months of therapy. The change (Delta) in EF and volumes between measurements before and after therapy was calculated and compared among study groups.

RESULTS

In controls, EF decreased and end-systolic volume increased. Atenolol prevented the decrease in EF and the increase in ESV. In contrast, metoprolol succinate significantly increased EF and decreased end-systolic volume. DeltaEF was significantly higher and Deltaend-systolic volume significantly lower in metoprolol succinate-treated dogs compared to atenolol-treated dogs (EF: 6.0 +/- 0.86% vs. 0.8 +/- 0.85%, p < 0.05; end-systolic volume: -4.3 +/- 0.81 ml vs. -1 +/- 0.52 ml, p <0.05).

CONCLUSIONS

In HF dogs, chronic therapy with atenolol does not elicit the same LV function and remodeling benefits as those achieved with metoprolol succinate.

Comparative Dose Titration Responses to the Introduction of Bisoprolol or Carvedilol in Stable Chronic Systolic Heart Failure

INTRODUCTION

Several beta blocking drugs (BB) reduce mortality in systolic heart failure (LVSD). We have compared the initial response to introduction of carvedilol and bisoprolol during the standard dose titration protocols for each drug.

METHODS

Approximately 31 unselected patients with stable LVSD were randomised to either carvedilol or bisoprolol measuring blood pressure, heart rate responses and both time and frequency domain heart rate variability (HRV).

RESULTS

One subject died; five withdrew due to intolerable BB related side effects. Carvedilol (n = 13) and bisoprolol (n = 12) attained similar maximal heart rate reduction and induced comparable falls in systolic and diastolic blood pressure. Higher carvedilol doses were associated with lower blood pressure compared to baseline. Individual time domain HRV indices remained unchanged over the initial titration period. Significant increases in triangular Index (TI) were seen with both BB. Carvedilol demonstrated greater (but non-significant) rises in TI compared to Bisoprolol.

CONCLUSIONS

In this study we found similar degrees and rate of onset of HR, HRV and BP response to both carvedilol and bisoprolol in treated LVSD patients. Carvedilol appears to show superior HRV rises compared to bisoprolol during initial titration. Any significant increases in HRV attributable to carvedilol compared to bisoprolol may emerge over a longer treatment interval in LVSD.

Effect of beta-blockade on autonomic modulation of heart rate and neurohormonal profile in decompensated heart failure

BACKGROUND

One of the putative mechanisms for the salutary effects of beta-blockers in patients with congestive heart failure (CHF) is their ability to improve autonomic dysfunction. However, patients with profound neurohumoral abnormalities derive little survival benefit from beta-blockers. The purpose of the current study was to evaluate the effect of beta-blockers on heart rate variability (HRV) in decompensated CHF.

METHODS

Time and frequency domain HRV indices were obtained from 24-hour Holter recordings and compared to assess the role of beta-blockade in 199 patients (mean age 60 +/- 14 years) with decompensated CHF. Neurohormonal differences were assessed by measuring norepinephrine, endothelin-1, tumor necrosis factor-alpha, and interleukin-6 in a subset of 64 patients.

RESULTS

All HRV indices were markedly suppressed but were substantially higher in patients who were on beta-blockers. Time domain measures of parasympathetic cardiac activity, the percentage of R-R intervals with > 50 ms variation (4.9 +/- 0.6 vs 7.7 +/- 1.2%, P = 0.006) and the square root of mean squared differences of successive R-R intervals (22.7 +/- 2.0 vs 31.6 +/- 4.1 ms, P = 0.004), were higher in the beta-blocker group. Spectral analysis revealed that the total power and the ultra-low frequency power were significantly higher in patients on beta-blockers (82% and 59%, respectively). The high frequency power, a spectral index of parasympathetic modulation, was 41% higher in the beta-blocker group (121 +/- 25 vs 171 +/- 27 ms(2), P = 0.02). Norepinephrine and interleukin-6 levels were substantially lower in patients on beta-blockers (28% and 61%, respectively). However, these differences did not reach statistical significance.

CONCLUSIONS

Beta-blockers improve the impaired cardiac autonomic regulation during high sympathetic stress of decompensated CHF. This effect may play an important role in protecting the myocardium and preventing arrhythmias during transient increases in sympathetic activity.

Relation between pharmacodynamic and anthropometric parameters during ergometry at rest and after repeated intake of metoprolol in healthy volunteers: results of a pilot study

Metoprolol is a widely used beta1-selective beta-blocker in hypertension and tachycardia. The influence on vital signs at rest and during ergometry (exercise heart rate or blood pressure, effect areas above baseline) was investigated in a pilot study with 18 healthy volunteers (mean age 29.1 years) by means of multiple and pairwise correlation analysis. At rest, the difference between predose and day 5 values were not associated with anthropometric characteristics. During ergometry for weight and height significant negative correlations were found corresponding to marked beta-values in the multiple regression models. Therefore heart rate decreases less markedly in slim persons which should be taken into consideration in exercise tests during metoprolol intake.

Lipid solubility of vasodilatory vanilloid-type beta-blockers on the functional and binding activities of beta-adrenoceptor subtypes

Various vanilloid-type beta-adrenoceptor blockers were studied on guinea pig right atrium and trachea and rat colon. In addition, we also investigated their beta(1)-, beta(2)-, and beta(3)-adrenoceptor binding affinities. All these beta-adrenergic antagonists inhibited (-)isoproterenol-induced positive chronotropic effects of the right atrium and tracheal relaxation responses in a concentration-dependent manner. Some of these agents prevented the inhibition of rat colon spontaneous motility by (-)isoproterenol. Of the agents tested, we found that ferulidilol, eugenodilol, eugenolol, isoeugenolol, and ferulinolol, as well as propranolol and metoprolol, possessed beta(3)-adrenoceptor blocking activities, others were nearly without effectiveness. Furthermore, the binding characteristics of vanilloid-type beta-adrenergic antagonists were evaluated in [3H]CGP-12177, a beta(1)/beta(2)-adrenoceptor blocker and a beta(3)-adrenoceptor agonist, binding to beta(1)-, beta(2)-, and beta(3)-adrenoceptor sites in rat ventricle, lung, and interscapular brown adipose tissue (IBAT) membranes, respectively. Eugenodilol, eugenolol, metoprolol, isoeugenolol, and ferulinolol were less potent than both propranolol and ferulidilol in competing for the beta(3)-adrenoceptor binding sites. From the results of in vitro functional and binding studies, we suggested that propranolol, ferulidilol, eugenodilol, eugenolol, metoprolol, isoeugenolol, and ferulinolol all possessed beta(3)-adrenoceptor blocking activities. On the other hand, we also found that eugenodilol, eugenolol, metoprolol, isoeugenolol, and ferulinolol had a low lipid solubility in comparison with propranolol and ferulidilol. In conclusion, we proposed that beta(3)-adrenoceptor antagonistic actions of these vanilloid-type beta-blockers were positively correlated with their lipid solubility.

Sympathetic restraint of respiratory sinus arrhythmia: implications for vagal-cardiac tone assessment in humans

Clinicians and experimentalists routinely estimate vagal-cardiac nerve traffic from respiratory sinus arrhythmia. However, evidence suggests that sympathetic mechanisms may also modulate respiratory sinus arrhythmia. Our study examined modulation of respiratory sinus arrhythmia by sympathetic outflow. We measured R-R interval spectral power in 10 volunteers that breathed sequentially at 13 frequencies, from 15 to 3 breaths/min, before and after beta-adrenergic blockade. We fitted changes of respiratory frequency R-R interval spectral power with a damped oscillator model: frequency-dependent oscillations with a resonant frequency, generated by driving forces and modified by damping influences. beta-Adrenergic blockade enhanced respiratory sinus arrhythmia at all frequencies (at some, fourfold). The damped oscillator model fit experimental data well (39 of 40 ramps; r = 0.86 +/- 0.02). beta-Adrenergic blockade increased respiratory sinus arrhythmia by amplifying respiration-related driving forces (P < 0.05), without altering resonant frequency or damping influences. Both spectral power data and the damped oscillator model indicate that cardiac sympathetic outflow markedly reduces heart period oscillations at all frequencies. This challenges the notion that respiratory sinus arrhythmia is mediated simply by vagal-cardiac nerve activity. These results have important implications for clinical and experimental estimation of human vagal cardiac tone.

Effect of beta-blockade on heart rate variability in decompensated heart failure

BACKGROUND

One of the putative mechanisms for the salutary effects of beta-blockers in patients with congestive heart failure is their ability to improve autonomic dysfunction. However, patients with profound neurohumoral abnormalities derive little survival benefit from beta-blockers. The purpose of the current study was to evaluate the effect of beta-blockers on heart rate variability in decompensated heart failure.

METHODS

Time and frequency domain heart rate variability indices were obtained from 24-h Holter recordings and compared to assess the role of beta-blockade in 199 patients (mean age 60+/-14 years [range 21 to 87]) with decompensated heart failure (New York Heart Association functional class III [66%] and IV [34%]).

RESULTS

All heart rate variability indices were markedly suppressed but were substantially higher in patients who were on beta-blockers. Time domain measures of parasympathetic cardiac activity, the percentage of RR intervals with >50 ms variation (4.9+/-0.6 vs. 7.7+/-1.2%, P=0.006) and the square root of mean squared differences of successive RR intervals (22.7+/-2.0 vs. 31.6+/-4.1 ms, P=0.004), were higher in the beta-blocker group. Spectral analysis revealed that the total power and the ultra low frequency power were significantly higher in patients on beta-blockers (82% and 59%, respectively). The high frequency power, a spectral index of parasympathetic modulation, was 41% higher in the beta-blocker group (121+/-25 vs. 171+/-27 ms(2), P=0.02). Multiple linear regression, adjusted for clinical parameters and drug therapies, revealed a strong positive relationship between beta-blockade and higher values of time and frequency domain measures. The mean number of ventricular tachycardia episodes were significantly lower in patients on beta-blocker therapy (3.6+/-1.5 vs. 19.0+/-5.3, P=0.04).

CONCLUSIONS

beta-blockers improve the impaired cardiac autonomic regulation during high sympathetic stress of decompensated heart failure.