Reversible complete left bundle branch block and a wide QRS complex following administration of sodium-glucose cotransporter-2 inhibitor and volume reduction in a patient with systolic heart failure: a case report.

Background: Guidelines recommend optimal medical therapy before cardiac resynchronization therapy (CRT) implantation. Herein, we report the potential effect of sodium-glucose cotransporter-2 inhibitors (SGLT2is) in improving the QRS duration and volume reduction in a patient with complete left bundle branch block (CLBBB) and reduced cardiac function. Case summary: A 68-year-old man with a history of ischaemic cardiomyopathy and decreased cardiac function had exacerbation of heart failure (HF) at an outpatient clinic. His QRS duration increased remarkably with a CLBBB of 143 ms on an electrocardiogram, and left ventricular desynchrony was assessed by echocardiography, suggesting an indication of CRT implantation. Administration of an SGLT2i and multimodal treatment for HF stabilized his HF condition and improved the QRS duration and volume reduction thereafter. The CLBBB recovered to incomplete LBBB with a QRS duration of 112 ms on electrocardiography after 6 months. The patient has been stably followed up with continuous medications, including SGLT2i, without requiring CRT implantation or worsening of HF for 12 months. Discussion: This case presents a unique scenario wherein electrical and mechanical reverse remodelling occurred in a patient with systolic HF and CLBBB, highlighting the potential benefits of SGLT2i in HF management. It may be important to carefully consider CRT indications when seeking other options to treat HF conditions and recognize an unusual phenomenon of reverse LBBB in clinical cases.