Electrophysiological characterization of a 19-years-old male marathon runner suffering a sudden cardiac death

1 in 50,000 of athletes suffers a cardiac student death (SCD) per year, more of them under 35 years of age. Around 25% of these patients had normal structure, implying that other electrical disorder cause these SCD. Determine the electrophysiological causes of a SCD of a young 19-years-old occurred during a marathon with any heart structural diseases. Pathologic left ventricle (PLV) (n = 1, male, 19-years-old) and control left ventricle (CLV) (n = 1, female, 56-years-old) were perfused and imaged using high resolution optical mapping and Di-4-ANEPPS like a dye. Endocardial and endocardial free wall and his bundle were paced to obtain activation time (AT), repolarization time (RT) and action-potential duration (APD). Purkinje-muscle junctions (PMJs) were determine like activation origins far from the his bundle pacing. Effective refractory period (ERP) was determined using S1S2S3S4 short-coupled pacing. The protocol was repeated after isoplenalie injection [500 nM] like β-adrenergic receptor agonist. His-ventricle activation at high frequency pacing was higher in PLV (143ms) than in control (84ms) and decrease in both at similar levels under ISO (≈60ms). APD gradient increase was observed in PLV near PMJs under ISO (from 3ms/mm to 40ms/mm) and any gradient was observed in the control one. Ectopic episodes were observed in PLV under ISO and 82% of the origins had less that 4 mm of distance with the PMJs. In PLV, the ERP in His-pacing is always lower (320, 260, 250 ms) than endocardial (350, 315, 285 ms) pacing but in CLV, the His-pacing ERP was always higher (320, 260, 240 ms) that endocardial pacing (280, 240, 220 ms). Ventricular fibrillation (VF) was observed in PLV after his bundle pacing at high frequency (more than 330 ms) and any VF was observed in CLV. During this VF, 76% of the focal activities had less than 4 mm of distance with the PMJs. Conduction system (CS) of the PLV shows high sensitivity to high frequency pacing and to presence of ISO. Ectopic episodes and APD gradient near PMJs may show the role of Purkinje network like arrhythmic source. Indeed, the shorter ERP during His-pacing than in the endocardium, give the possibility to produce a macro-re-entry in the conduction system and maintain the arrhythmia with focal activities. CS abnormalities likely played a critical role in arrhythmogenicity and maintenance of VF in this patient during sudden cardiac death.