Abstract
Background: 5-FU a cytostatic agent is used to treat various malignancies. Cardiotoxicity is infrequent complication of 5-FU. Previously we had observed ECG changes in our patients on 5-FU viz sinus bradycardia, atrial fibrillation. We also found that 5-FU bradycardia might be a hypervagotonia as vagolytics abolished it. This study was undertaken to assess the impact of this commonly used chemotherapeutic agent on basic physiologic parameters of impulse initiation and conduction in human heart. The aim was to study effect of 5-FU on electrophysiological properties of SA node and conduction system of heart.Methods: Pre -5 FU state patients were subjected to electrophysiological study and following parameters were checked viz heart rate, CSNRT. SACT, AH and HV intervals and wenckebach point. Post 5- FU state these parameters were again checked. Response to Atropine was seen in patients who developed sinus bradycardia.Results: Sinus bradycardia was seen in 8% (n=2) of patients in post 5FUstate Their electrophysiological parameters SNRT, CSNRT, SACT, AH were mildly prolonged (above the normal) in post 5FU state. Post atropine there was increase in heart rate and the deranged electrophysiological parameters came back to normal. Atrial fibrillation was seen in two patients while performing sinus nodal functions in post 5FU state.Conclusions: Sinus bradycardia is a rare cardiotoxic side effect of 5FU, is a result of an autonomic imbalance viz hypervagotonia which is abolished by atropine and more common in infusuion form than bolus. Infra-his conduction is not altererd and threshold for inducing atrial arrhythmias is decreased in post 5-FU state.
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