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Francesco Del Monte, Filippo Angelini, Anna Maria Villar, Fulvio Gabbarini, The arrhythmic risk in Kearns–Sayre syndrome: still many questions unanswered, EP Europace, Volume 23, Issue 6, June 2021, Pages 980–981, https://doi.org/10.1093/europace/euab104
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We read with extreme interest the study by Di Mambro et al.,1 describing the progressive involvement of cardiac conduction system in 15 paediatric patients with a diagnosis of Kearns–Sayre Syndrome (KSS). This represents the first prospective work on KSS providing a useful algorithm for the arrhythmic risk stratification in KSS patients developing cardiac conduction disorders.
Kearns–Sayre Syndrome is a progressive multisystem disorder generally suspected on the basis of clinical features. However, in the early stages clinical diagnosis may be challenging: in such cases, genetic testing and muscle biopsy confirm the diagnosis and allow early initiation of cardiologic follow-up.
Cardiac involvement is frequent in KSS: the most common manifestations are conduction disorders which may rapidly progress to complete atrioventricular block.1
In patients with KSS, current guidelines suggest implanting a permanent pacemaker (PM) in case of any conduction disorder (with 1:1 atrioventricular conduction), and advice for defibrillator (ICD) implantation ‘if appropriate’; however, evidence supporting these indications is limited.2,3
Di Mambro et al. highlighted the progressive deterioration of the cardiac conduction system in KSS: in their cohort, left anterior fascicular block preceded right bundle branch block and bi-fascicular block rapidly degenerated into advanced or complete atrioventricular block in 40% of patients (median time 1.7 years). Therefore, they suggest a timely PM implantation since bi-fascicular block development. The authors strongly support the need for an electrocardiographic screening in KSS and a close follow-up in order to determine each patient’s arrhythmic risk. Due to the paucity of data, it remains uncertain if routine electrophysiological study (EPS) and His-ventricular interval determination may be of any prognostic utility.4
After PM implantation, sudden cardiac death may also occur because of ventricular arrhythmias (VAs), such as polymorphic ventricular tachycardia and ventricular fibrillation. Despite VAs can be triggered by early afterdepolarizations due to bradycardia, they could also be connected to delayed afterdepolarizations due to the increased intracellular calcium concentration secondary to mitochondrial dysfunction. Therefore, PM would protect only from bradycardia-triggered VAs.5 Moreover, VAs could also be favoured by structural abnormalities not evident at transthoracic echocardiography in the early phases of the disease, and the role of Cardiac Magnetic Resonance (CMR) may become pivotal in this scenario.4
Di Mambro et al. describe that only one patient received an ICD for a non-sustained ventricular tachycardia at 24-h electrocardiogram (ECG)-Holter, and a sustained ventricular tachycardia during EPS. Nevertheless, ECG-Holter allows a very limited time registration, and many ventricular events may remain undetected. Implantable loop recorders (ILR) may represent a valid alternative to monitor these patients before PM implantation and guide proper decisions.
We acknowledge the authors’ effort in performing this study prospectively, and we want to emphasize that this may represent a first step in optimizing cardiology management in KSS. In fact, the role of EPS, ILR, exercise stress test, and CMR remain uncertain. Moreover, given the rarity of KSS, such important issues should not be inferred by case reports and small observational studies, but a multicentric working group on KSS is warranted.
Conflict of interest: none declared.
