Conundrum of Sudden Cardiac Death

Abstract

e58T he cause of sudden cardiac death (SCD) in a young patient without any previous cardiac history can oftentimes be challenging, particularly if there are ≥2 equally plausible but improbable pathogenesis. As part of a thorough evaluation, electrophysiological, anatomic/functional, and genetic testing results may be illuminating but at other times can be misleading unless the nuances of test results and their interpretation are fully appreciated. We report a case of a patient who survived an out-of-hospital cardiac arrest after vigorous exercise and who was found to have a decrementally conducting Mahaim-like accessory pathway (AP), as well as a dilated right ventricle (RV) and a missense mutation identified in the plakophilin-2 (PKP2) gene. We examine the challenges of interpreting results of such screening tests and how to distinguish the probable pathogenesis of SCD when there are 2 competing findings, neither of which is entirely dispositive. CaseA 29-year-old white woman with multiple congenital anomalies, including coarctation of the aorta and bicuspid aortic valve, was admitted to the hospital after sudden cardiac arrest. Several years earlier, she was reported to have a transient irregular wide complex tachycardia thought to be because of preexcited atrial fibrillation (AF). On the day of presentation, she experienced abrupt syncope immediately after playing tennis. A bystander initiated cardiopulmonary resuscitation and delivered 2 shocks with an automatic external defibrillator ( Figure 1). Emergency medical services arrived shortly afterward and delivered an additional external shock, resulting in a return of spontaneous circulation. Rhythm strips shortly after resuscitation showed an irregular rhythm with a narrow complex configuration and runs of an irregular rhythm with a wide complex morphology. She was brought to her local emergency room where her initial laboratory studies were all within normal limits. A toxicology screen was negative. A 12-lead ECG showed sinus bradycardia at 38 beats per minute with a short PR interval and anterior T-wave inversion in leads V1 and V2 (Figure 2A). The QT interval was normal. She received intravenous amiodarone on admission, but this was discontinued because of QT prolongation. She was transferred to our hospital for further care. When she regained consciousness and lucidity, she reported a history of monthly palpitations, lasting between 5 and 30 minutes, not associated with lightheadedness. She denied the use of any recreational drugs before the event. Her only medication was gabapentin. There was no previous history of syncope or family history of syncope, SCD, or heart disease.Although the patient's baseline ECG showed no evidence for preexcitation, hospital telemetry recorded an occasional atrial bigeminal pattern associated with aberrancy or preexcitation of the premature beat ( Figure 2B). An echocardiogram demonstrated normal left ventricular size and function and moderate tricuspid regurgitation. Cardiac MRI revealed normal left ventricular size and f...

Cardiomyopathic mutations in essential light chain reveal mechanisms regulating the super relaxed state of myosin

“…We previously reported that transgenic mice expressing the truncated N-ELC (Δ43 mice) display near-physiological cardiac remodeling with an increase in left ventricular (LV) wall thickness but no changes in cardiac morphology or function or in myofilament contraction/relaxation parameters are observed ( Sitbon et al, 2020 ). On the other hand, pathological hypertrophy due to hypertrophic cardiomyopathy (HCM) or restrictive cardiomyopathy (RCM) is characterized by interstitial fibrosis, myofilament disarray, reduced LV cavity, and impaired heart’s relaxation phase and can lead to diastolic dysfunction and sudden cardiac death ( Seidman and Seidman, 1998 ; Spirito et al, 2000 ; Arad et al, 2002 ; Ip et al, 2013 ). RCM is additionally manifested by biatrial enlargement, increased stiffness of the LV wall with no increase in wall thickness ( Kushwaha et al, 1997 ; Yuan et al, 2017 ).…”