Clinical Significance of Tachycardia in Cystic Fibrosis Patients: A Case Report

Abstract

Khalid Abou Farha

Background: Post-bronchodilator evaluation of pulmonary function and collection of expectorated sputum samples are commonly used tests in cystic fibrosis (CF) clinical trials. β2 adrenergic receptor agonists, such as salbutamol, are used for this purpose.Supraventricular tachycardia is a known dose-related side effect of inhaled salbutamol. Under normal breathing conditions, CF patients have been found to be tachycardiac compared to healthy subjects. In addition, mutation in the cardiac CF transmembrane conductance regulatorgene may result in (subclinical) myocardial dysfunction and a deficiency in ischaemic preconditioning, resulting in an increased risk for ischemic heart disease in the CF patient. Nevertheless, the impact of β2agonists on the CF- associated tachycardia is often an ignored safety parameter in CF clinical trials.

Case presentation: A 21 year old CF female patient received an inhalation dose of 400ug salbutamol, in the context of a clinical trial, to perform post-bronchodilator pulmonary function tests and collect spontaneously expectorated sputum. The patient’s cardiac electrical activities were monitored before and after salbutamol inhalation. The prebronchodilator (baseline) recording demonstrated large fluctuation in heart rate coupled with short episodes of sinus tachycardia. Post salbutamol administration, the tachycardia increased in rate and was associated with dynamic ST-T segment changes including flattening of the T wave and ST segment depression in at least 2 adjacent limb leads, ECG features suggestive of myocardial ischemia. Approximately 4 hours post salbutamol administration, heart rate and ST- T segment abnormalities returned to baseline morphology.

Conclusion: CF patients might have tachycardia as part of their disease natural history. The presence of continuous or fluctuating tachycardia should be verified in this group of patients. Administration of inhalation β2 agonists to tachycardiac CF patients should be considered with caution. This may entail individualized dose adjustment and telemetry monitoring of patients’ cardiac electrical activity. This helps early detection and facilitates timely medical management of any emerged cardiovascular adverse effects such as myocardial ischemia in this medically fragile group of patients, particularly those with subclinical myocardial pathology

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