PMC10337585_01
(A) Electrocardiogram during flecainide toxicity demonstrating 1:1 AV conduction with a prolonged PR interval, left axis deviation, nonspecific intra-ventricular conduction block and prolonged QTC. Rate 125 bpm, PR interval 190 ms, QRS duration 100 ms, QTc 494 ms. (B) Electrocardiogram following sodium bicarbonate treatment demonstrating sinus bradycardia with normalization of the QRS duration, diffusely flat T wave changes and prolonged QTc. Rate 88 bpm, PR interval 146 ms, QRS duration 70 ms, QTc 529 ms.
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F1
Cardiac telemetry initially identified an irregular predominantly wide-complex rhythm with long RP morphology, occasional narrow complex beats, and frequent wide-complex couplets and triplets at a rate of 150 bpm (Figure 1A). Flecainide toxicity could not be excluded in the presence of rate-dependent aberrancy during sinus rhythm, and therefore, 1 mEq/kg of sodium bicarbonate was administered leading to normalization of the QRS duration (Figure 1B).
Bedside telemetry demonstrating a regular, narrow complex tachycardia with long RP morphology and deeply negative P waves in the inferior leads with PJRT.
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F2
Several episodes began with aberrantly conducted wide-complex beats, consistent with the Ashman phenomenon, followed by narrow complex tachycardia of long RP morphology with deeply negative P waves in the inferior leads and rates 180-220 bpm consistent with a rare and often medically refractory form of SVT called persistent junctional reciprocating tachycardia (PJRT) (Figure 2).