Short coupled Ventricular Fibrillation in a patient with TRPM4 mutation

Inherited channelopathies are a cause of syncope in a structurally normal heart with subtle signs on baseline ECG, but sometimes these signs may be absent. The precipitant may either be a tachy or a bradyarrhythmia needing prompt diagnosis and treatment institution. One such cause is short coupled Ventricular fibrillation (VF) where the baseline ECG has a normal corrected QT interval (QTc) with multiple Ventricular Premature Complexes (VPCs) noted in the ECG especially around an event of syncope. The TRPM4 gene, encoding the Transient Receptor Potential Melastatin 4 ion channel, currently a variant of unknown significance is a calcium activated channel which is involved in regulation of the diastolic depolarization in the Sinoatrial (SA) node. Loss of function mutation of the gene may present as bradyarrhythmias or atrial arrhythmias due to conduction disturbances. We present a case of intractable short coupled VF with a coexistent tachy-brady syndrome, attributed to TRPM4 mutation. Due to persistent intractable VF despite antiarrhythmic therapy and implantable cardioverter-defibrillator (ICD), patient was given quinine instead of quinidine due to non-availability of the same, which led to significant alleviation of symptoms. This case underscores the complexity of managing ventricular arrhythmias and highlights the potential therapeutic role of quinine in select cases, in the scenario of unavailability of quinidine, offering insights into personalized treatment approaches for these challenging conditions.