Beta2-agonist induced ventricular dysrhythmias secondary to hyperexcitable conduction system in the absence of a long QT syndrome

Electronic health record (EHR) based postmarketing surveillance of adverse events associated with pediatric off-label medication use: A case study of short-acting beta-2 agonists and arrhythmias

PURPOSE

Use electronic health record (EHR) data to (1) estimate the risk of arrhythmia associated with inhaled short-acting beta-2 agonists (SABA) in pediatric patients and (2) determine whether risk varied by on-label versus off-label prescribing.

METHODS

Retrospective cohort study of 335 041 children ≤18 years using EHR primary care data from 2 pediatric health systems (2011-2013). A series of monthly pseudotrials were created, using propensity score methodology to balance baseline characteristics between SABA-exposed (identified by prescription) and SABA-unexposed children. Association between SABA and subsequent arrhythmia for each health system was estimated through pooled logistic regression with separate estimates for children initiating under and over 4 years old (off-label and on-label, respectively).

RESULTS

Eleven percent of the cohort received a SABA prescription, 57% occurred under the age of 4 years (off-label). During the follow-up period, there were 283 first arrhythmia events, most commonly atrial tachyarrhythmias and premature ventricular/atrial contractions. In 1 health system, adjusted risk for arrhythmia was increased among exposed children (OR 1.89, 95% CI 1.31-2.73) without evidence of interaction between label status and risk. The absolute adjusted rate difference was 3.6/10 000 person-years of SABA exposure. The association between SABA exposure and arrhythmias was less strong in the second system (OR 1.26, 95% CI 0.30-5.33).

CONCLUSION

Using EHR data, we could estimate the risk of a rare event associated with medication use and determine difference in risk related to on-label versus off-label status. These findings support the value of EHR-based data for postmarketing drug studies in the pediatric population.

The increase in rat ventricular automaticity induced by salbutamol is mediated through β(1)- but not β(2)-adrenoceptors: role of phosphodiesterases

AIMS

While β(2)-adrenoceptor (AR) agonists are useful bronchodilators, they also produce cardiac arrhythmias. These agents are not fully selective and also activate β(1)-AR, but the involvement of β(1)-AR and β(2)-AR in the observed pro-arrhythmic effect has not been established. We studied the effect of β(1)-AR and β(2)-AR activation on ventricular automaticity and the role of phosphodiesterases (PDE) in regulating this effect.

MAIN METHODS

Experiments were performed in the spontaneously beating isolated right ventricle of the rat heart. We also measured cAMP production in this tissue.

KEY FINDINGS

The β(2)-AR agonist salbutamol (1-100 μM) produced a concentration-dependent increase in ventricular automaticity that was not affected by 50nM of the β(2)-AR antagonist ICI 118551. This effect was enhanced by the non-selective PDE inhibitor theophylline (100 μM) and by the selective PDE4 inhibitors rolipram (1 μM) and Ro 201724 (2 μM), but not modified by the selective PDE3 inhibitors cilostamide (0.3 μM) or milrinone (0.2 μM). The effects of salbutamol alone and in the presence of either theophylline or rolipram were virtually abolished by 0.1 μM β(1)-AR antagonist CGP 20712A. Salbutamol (10 μM) increased the cAMP concentration, and this effect was abolished by CGP 20712A (0.1 μM) but enhanced by theophylline (100 μM) or rolipram (1 μM). Cilostamide (0.3 μM) failed to modify the effect of salbutamol on cAMP concentration.

SIGNIFICANCE

These results indicate that the increase of ventricular automaticity elicited by salbutamol was exclusively mediated through β(1)-AR and enhanced by non-selective PDE inhibition with theophylline or selective PDE4 inhibition. However, PDE3 did not appear to regulate this effect.

Inhaled beta2-adrenoceptor agonists: cardiovascular safety in patients with obstructive lung disease

Although large surveys have documented the favourable safety profile of beta(2)-adrenoceptor agonists (beta(2)-agonists) and, above all, that of the long-acting agents, the presence in the literature of reports of adverse cardiovascular events in patients with obstructive airway disease must induce physicians to consider this eventuality. The coexistence of beta(1)- and beta(2)-adrenoceptors in the heart clearly indicates that beta(2)-agonists do have some effect on the heart, even when they are highly selective. It should also be taken into account that the beta(2)-agonists utilised in clinical practice have differing selectivities and potencies. beta(2)-agonist use has, in effect, been associated with an increased risk of myocardial infarction, congestive heart failure, cardiac arrest and sudden cardiac death. Moreover, patients who have either asthma or chronic obstructive pulmonary disease may be at increased risk of cardiovascular complications because these diseases amplify the impact of these agents on the heart and, unfortunately, are a confounding factor when the impact of beta(2)-agonists on the heart is evaluated. Whatever the case may be, this effect is of particular concern for those patients with underlying cardiac conditions. Therefore, beta(2)-agonists must always be used with caution in patients with cardiopathies because these agents may precipitate the concomitant cardiac disease.

Adverse effects of beta-agonists

Short-acting beta-adrenergic receptor agonists have pharmacologically predictable dose-related and potency-related adverse effects, including tachycardia and tremor, and they also affect serum potassium and glucose. These effects all show tolerance with continued exposure. The potential for arrhythmia is increased by comorbidity and hypoxemia. Nonpharmacologically predictable effects include airway hyperresponsiveness to nonspecific and specific stimuli, including allergen and exercise, and increased airway inflammation. Genetic variants of the beta-adrenergic receptor alter susceptibility to adverse effects of beta-agonists on airway function. The impact of the enantiomers of beta-agonists on adverse effects remains unclear. The two epidemics of asthma death among young people were temporally associated with introduction of potent short-acting beta-agonists (isoproterenol and fenoterol) and appear to be related to adverse effects of these drugs on airway function and airway hyperresponsiveness rather than to cardiotoxicity. Compared with short-acting agents, long-acting beta-agonists show similar but less pronounced pharmacologically predictable effects, and they have not been shown to increase airway hyperresponsiveness in adults. Postmarketing surveillance studies have not suggested significant adverse effects of long-acting beta-agonists on morbidity and mortality.

Standard dose of inhaled albuterol significantly increases QT dispersion compared to low dose of albuterol plus ipratropium bromide therapy in moderate to severe acute asthma attacks in children

BACKGROUND

Beta-2 agonist therapy has previously shown to increase the QT dispersion (QTd) in asthmatic patients and increased QTd has been well documented in association with cardiac arrhythmias and sudden death. However, the data concerning the effect of low doses of beta-2 agonist therapy in combination with the anticholinergic agents to potentiate bronchodilatation on QTd in asthmatic children are limited. The objectives of this study was to investigate the changes on QTd during both the standard dose of nebulized albuterol therapy and low dose nebulized albuterol plus inhaled ipratropium therapyn to assess the potential arrhythmogenic risk of these two treatment strategies in children with acute asthmatic attacks.

METHODS

Forty-three children with the diagnosis of moderate to severe acute asthma were enrolled in the study. Standard dose of nebulized albuterol therapy (0.15 mg/kg) were administered to 20 patients (group 1) and low dose of nebulized albuterol (0.075 mg/kg) plus nebulized ipratropium bromide therapy (250 microg/dose) were given to the remaining 23 patients (group 2). Respiratory distress score, peak expiratory flow rate, arterial blood pressure, O2 saturation, serum potassium and urea nitrogen levels were studied and QT interval parameters were measured from the standard 12-lead electrocardiograms at baseline and after treatment.

RESULTS

Significant improvement was achieved in respiratory distress score and peak expiratory flow rate after three dose inhalation. No significant difference was observed between the pre and post-treatment values of serum potassium, blood urea nitrogen, O2 saturation and arterial blood pressure values. The evaluation of the corrected QTd (QTcd) showed that while there was no statistical difference in the pre and post-treatment values in group 2 (30.4+/-3.1 msn vs 32.1+/-3.9 msn), QTcd was found to be significantly increased in group 1 after treatment (29.0+/-3 msn vs 40.6+/-5.1 msn, P<0.0001).

CONCLUSION

The data of the present study suggest that the increase of the QTd is more prominent with the use of a standard dose of albuterol compared to low dose albuterol plus ipratropium therapy. Therefore, it may be concluded that a low dose of albuterol plus ipratropium bromide therapy may be preferred to avoid rhythm disturbances in asthmatic children.

Lower arrythmogenic risk of low dose albuterol plus ipratropium

OBJECTIVE

Wheezy infants are in need of urgent bronchodilatation owing to their intermittent bronchoconstriction. beta 2 agonists are frequently used in emergencies and have previously shown to increase the QT dispersion (QTd), which may be associate with high risk of cardiac arrhythmia, in asthmatics. However, effect of low dose beta 2 agonist therapy in combination with the anticholinergic agents on QTd in wheezy infants is not known. This study aimed to assess the effect of standard dose of nebulized albuterol (NAB) and low doses of NAB combined with ipratropium-bromide (NIB) on QTd in wheezy infants.

METHODS

Twenty-nine children, under 2 years old, with the diagnosis of wheezy infant with acute exacerbation were enrolled in the study. Thirteen were treated by standard dose of NA therapy (0.15 mg/kg) and low doses of NAB (0.075 mg/kg) plus NIB (250 micrograms/dose) therapy was given to the remaining subjects. Respiratory distress score, O2 saturation and side effects were studied and QTd were measured from the standard electrocardiograms at baseline and after treatment. Significant improvement was achieved in clinical score and oxygenation of both groups.

RESULT

The evaluation of the corrected QTd (QTcd) showed that there was no significant difference between pretreatment values of both groups (p > 0.05). However, while there was no statistically significant difference in the pre and post-treatment values of QTcd of infants treated with combination therapy, QTcd was found to be significantly increased in NAB group after treatment (p < 0.05).

CONCLUSION

Our results suggest that, while clinical improvement is same, the increase of the QT dispersion is more prominent with the use of standard dose of NAB compared to low dose NAB plus NIB therapy. So, low dose of beta 2 agonist in combination with anticholinergic agents may much safer than the use of standard dose of beta 2 agonists alone in regard to preventing the possibility of arrythmogenic effects in wheezy infants with acute exacerbation.

Serum potassium levels, CPK-MB and ECG in children suffering asthma treated with beclomethasone or beclomethasone-salmeterol

Asthma morbidity and mortality has increased. One of the possible causes is the excessive use of beta agonists. The aim of this study is to compare the effects of six week treatment with beclomethasone alone (Ibec) or the combination of beclomethasone-salmeterol (Ibe + Isal) on serum potassium (K), CPK-MB and ECG in children suffering asthma. It was a prospective, randomised, open cross-over trial. Patients received either Ib2 (2 puff/12 hr, 100 micrograms per puff) or Ibe + Isal (B 2 puff/12 hr, 100 micrograms per puff and S 2 puff/12 hr, 25 micrograms per puff) with dose meter inhaler by 6 weeks, with a four-week wash-out period between the treatments. K, CPK-MB and ECG were assessed at baseline, and after each treatment period. There were 9 girls and 20 boys, aged 11 +/- 2.18 (mean +/- SD) years, baseline K was 4.57 +/- 0.43 mEq/l, after B K 4.38 +/- 0.39 IU and after BS K 4.38 +/- 0.40. The CPK-MB level were baseline 14.75 +/- 4.5, after B 20.10 +/- 6.9 and after BS 21 +/- 8.05 (p < 0.05). Baseline QTc was 0.416 +/- 0.02 msec, after B 0.425 +/- 0.027, and after BS 0.415 +/- 0.029. We conclude that the treatment of children with asthma with 400 micrograms per day of Ibec or concomitantly with 100 micrograms of Isal for 6 weeks does not alter the serum K+ or the QTc. However, the CPK-MB has a significant increment with both treatments but without clinical and/or ECG changes. We can't affirm that Ibec or Ibec plus Isal have a cardiotoxic side-effect by the only presence of high levels of CPK-MB. We agree that it is necessary a close follow up of these apparently asymptomatic patients not induce important cardiovascular changes although CPK-MB was increased.