Bicarbonate refractory QRS prolongation and left bundle-branch block following escitalopram and lamotrigine overdose: A case report and literature review of toxic left bundle-branch block.

WHAT IS KNOWN AND OBJECTIVE: Toxic prolongation of the QRS interval most often results from blockade of cardiac voltage-gated sodium channels and manifests on electrocardiogram with a right bundle-branch block-like morphology. Rarely, a left bundle-branch block (LBBB) morphology has been reported.

CASE REPORT: We report a case of transient LBBB resultant from ingestion of lamotrigine and citalopram which was refractory to sodium bicarbonate therapy and eventually resolved spontaneously.

WHAT IS NEW AND CONCLUSION: Cases of toxic LBBB are less likely to respond to bicarbonate therapy, suggesting that this finding is due to a mechanism other than sodium channel blockade.