Introduction Intravenous (IV) aminophylline has an established role in the management of acute severe asthma, with beneficial bronchodilatory, anti-inflammatory and immunomodulatory effects. However, concern is often raised regarding its potential to prolong the QT interval and precipitate cardiac arrhythmias, given its catecholamine enhancing effect.1 Despite this, the influence of IV aminophylline on electrocardiographic (ECG) parameters in patients with acute severe asthma is not fully known. We routinely perform 12-lead electrocardiography on all patients before and 24 h after commencing IV aminophylline.
Objective To evaluate the effect of intravenous aminophylline on ECG parameters in patients with acute severe asthma.
Method We assessed electrocardiographic parameters in 26 (21 female) consecutive patients, with a mean (SD) age of 48 (11) years, admitted with severe asthma. We measured serum electrolytes, aminophylline levels and ECG parameters at baseline and within 48 h of commencing IV aminophylline. ECGs were independently assessed by a cardiologist blinded to patient identity and ECG timings.
Results No significant difference in mean QTc, PR or QRS interval was found following treatment (Abstract P109 table 1). Furthermore, there was no difference in number of atrial or ventricular ectopics, T-wave amplitude or frequency of arrhythmias. However, in four patients the QTc was prolonged above the upper limit of normal (447 ms to 519 ms, 450 ms to 516 ms, 516 ms to 568 ms and 471 ms to 548 ms).
Conclusions These findings are largely reassuring with regard to the safety of IV aminophylline in severe asthma, in terms of its effects on standard electrocardiographic variables and the incidence of arrhythmias. There was, however, evidence of QTc prolongation in four subjects indicating a need for caution and ECG checks, especially with concomitant use of QT prolonging drugs.