Cavotricuspid isthmus ablation and subcutaneous monitoring device implantation in a 2-year-old baby with 2 SCN5A mutations, sinus node dysfunction, atrial flutter recurrences, and drug induced long-QT syndrome: a tricky case of pediatric overlap syndrome?

An Adolescent Patient with Sick Sinus Syndrome Complicated by Hypothyroidism Carrying an SCN5A Variant

Previous studies have reported that hypothyroidism can lead to sick sinus syndrome (SSS) or other rhythm disturbances. Variants in the alpha subunit of the cardiac sodium channel (SCN5A) are known to be among the genetic causes of SSS. We encountered an adolescent patient with SSS and hypothyroidism who also harbored an SCN5A variant. The patient was a 13-year-old girl who was referred to our hospital because of bradycardia identified during a school electrocardiography screening. Clinical examination revealed severe hypothyroidism due to Hashimoto thyroiditis and SSS. After levothyroxine supplementation, her symptoms of hypothyroidism improved; however, the SSS did not. Genetic testing revealed a heterozygous variant (c.1066 G>A, p.Asp356Asn) in SCN5A. This is the first report of the coexistence of SSS due to an SCN5A variant and severe hypothyroidism in an adolescent patient. While patients with SCN5A variants exhibit phenotypic heterogeneity due to the presence of various modifiers, the presence of severe hypothyroidism may affect the development of SSS. This case highlights the importance of genetic analysis, including testing for SCN5A variants, in patients with hypothyroidism complicated by SSS or cardiac conduction disorders.

Genetic Complexity of Sinoatrial Node Dysfunction

The pacemaker cells of the cardiac sinoatrial node (SAN) are essential for normal cardiac automaticity. Dysfunction in cardiac pacemaking results in human sinoatrial node dysfunction (SND). SND more generally occurs in the elderly population and is associated with impaired pacemaker function causing abnormal heart rhythm. Individuals with SND have a variety of symptoms including sinus bradycardia, sinus arrest, SAN block, bradycardia/tachycardia syndrome, and syncope. Importantly, individuals with SND report chronotropic incompetence in response to stress and/or exercise. SND may be genetic or secondary to systemic or cardiovascular conditions. Current management of patients with SND is limited to the relief of arrhythmia symptoms and pacemaker implantation if indicated. Lack of effective therapeutic measures that target the underlying causes of SND renders management of these patients challenging due to its progressive nature and has highlighted a critical need to improve our understanding of its underlying mechanistic basis of SND. This review focuses on current information on the genetics underlying SND, followed by future implications of this knowledge in the management of individuals with SND.

Cost comparison of two implantable cardiac monitors in two different settings: Reveal XT in a catheterization laboratory vs. Reveal LINQ in a procedure room

AIMS

Implantable cardiac monitors (ICMs) are used for long-term heart rhythm monitoring, e.g. to diagnose unexplained syncope or for detection of suspected atrial and ventricular arrhythmias. The newest ICM, Reveal LINQ™ (Medtronic Inc.), is miniaturized and inserted with a specific insertion tool kit. The procedure is therefore minimally invasive and can be moved from catheterization laboratory (cath lab) to a less resource intensive setting. This study aims to assess the change in procedure costs when performed outside the cath lab.

METHODS AND RESULTS

A bottom-up costing methodology was used. Data were collected from interviews with physicians, cath lab managers, and financial controllers. Hospitals in the Netherlands, France, and the UK were included in this study. The cost comparison of a Reveal XT implantation in a cath lab setting vs. a Reveal LINQ insertion outside a cath lab resulted in an estimated reduction of €662 for the UK, €682 for the Netherlands, and €781 for France. These cost savings were primarily realized through fewer staff, less equipment, and overhead costs. The net effect on savings depends on the price differential between these two technologies. The patient care pathway can be improved due to the possibility to move the procedure out of the cath lab.

CONCLUSION

Inserting the miniaturized version of the ICM is simpler and faster, and the procedure can take place outside the cath lab in a less resource intensive environment. Hospitals save resources when the higher price of the Reveal LINQ does not outweigh these savings.