Suspected Kearns-Sayre-associated Tachy-Brady Syndrome

Kearns–Sayre syndrome (KSS) is a rare mitochondrial disorder characterized by a triad of onset before the age of 20 years, chronic progressive external ophthalmoplegia (CPEO), and pigmentary retinopathy, together with systemic features such as cardiac conduction disease. Deletions or mutations in mitochondrial deoxyribonucleic acid (mtDNA) can disrupt cellular function, affecting the myocardial intercalated discs, resulting in arrhythmias. We hereby present the case of a 65-year-old Caucasian male of German origin with a pre-existing diagnosis of KSS, who presented with tachy-brady syndrome (TBS) with paroxysmal atrial fibrillation (PAF) and sinus bradycardia (SB) with a first-degree atrioventricular block (AVB). He was treated with guideline-directed medical therapy (GDMT) for heart failure with preserved ejection fraction (HFpEF) and direct oral anticoagulation (DOAC) for PAF. He deferred device therapy despite extensive counseling for sudden cardiac death (SCD) associated with KSS. Given the relative paucity of conventional risk factors, suspected Kearns-Sayre-associated tachy-brady syndrome (TBS) was deemed the likely diagnosis.