HRCR Rare Diseases Article Collection
Lyme carditis presenting with an incessant atrioventricular nodal reentrant tachycardia masking a variable atrioventricular blockLyme disease is a common tick-borne illness with a high prevalence in the Northeast region of the United States.1 It is an infection caused by Borrelia burgdorferi, a gram-negative spirochetal bacterium carried by infected ticks such as Ixodes scapularis. They are found outdoors, latched onto blades of grass until they can attach to a host. If not treated early, serious complications can develop. Since Lyme antibodies can take several weeks to develop, false-negatives can arise in about 50% of cases when testing is done too early.
Leadless atrioventricular synchronous pacing in Eisenmenger syndromeEisenmenger syndrome is at the extreme end of the phenotypic spectrum of pulmonary arterial hypertension associated with congenital heart disease. Over time, a large nonrestrictive left-to-right shunt provokes progressive pulmonary vascular disease that results in the shunt becoming bidirectional or reversing direction (ie, right-to-left). When the need for pacing arises, transvenous leads are generally considered contraindicated owing to a prohibitively high risk of paradoxical thromboembolism.
Cardiac magnetic resonance imaging–negative cardiac sarcoidosisSarcoidosis is a multisystem inflammatory granulomatous disease of unknown etiology. Up to 55% of patients with systemic sarcoidosis have documented cardiac involvement.1 Albeit less common, cardiac manifestations can be the first clinical presentation of sarcoidosis. These include conduction disturbances, ventricular arrhythmias, heart failure, and sudden cardiac death, accounting for 13%–25% of sarcoidosis-related death.1 Initial diagnostic workup often requires comprehensive cardiac imaging, including echocardiography, cardiac magnetic resonance imaging (CMR), and 18F-FDG positron emission tomography (PET); nonetheless, the diagnosis of cardiac sarcoidosis remains challenging.