Ventricular preexcitation in children and young adults - Atrial myocarditis as a possible trigger of sudden death

Background-Sudden death (SD) in ventricular preexcitation (VP) syndrome is believed to be the result of atrial fibrillation with rapid ventricular res ponse over the accessory pathway. Previous reports are anecdotal and often lack autopsy validation. Methods and Results-Prevalence and clinicopathological features of VP were investigated in a series of 273 SDs in children and young adults (aged less than or equal to 35 years), Site of accessory atrioventricular (AV) connec tion was predicted by 12-lead ECC, Right and left AV ring together with the sinoatrial and AV septal junction were studied in serial histological sect ions, Ten patients (3.6%; male, mean age 24+/-7 years) had VP: 8 had Wolff- Parkinson-White (WPW) and 2 had Lown-Ganong-Levine (LGL) syndrome. Six pati ents had previous symptoms, and SD occurred at rest in all but 1, Pathologi cal substrates of LGL consisted of AV-node hypoplasia and right-sided atrio -Hisian tract, respectively. In the 8 WPW patients, 10 total accessory AV p athways consisting of ordinary myocardium were found (7 left lateral, 2 rig ht posterolateral, and 1 septal). These pathways were close to the endocard ium (mean distance, 750+/-530 mum) and 310+/-190 mum thick. In 4 WPW patien ts (50%), isolated acute atrial myocarditis was found, which was polymorpho us in 1 and lymphocytic in 3. Coclusions-VP accounted for 3.6% of SD in young people and was not preceded by warning symptoms in 40%. A left accessory pathway was the most frequent substrate, and its subendocardial location supports the feasibility of cat heter ablation, Isolated atrial myocarditis may act as a trigger of paroxys mal atrial fibrillation that leads to SD.