A twenty-seven year old pregnant woman in her twenty-eighth week, suffering from Danon ‘s disease, goes to the emergency room due to inappropriate shock of the ICD on high frequency atrial tachyarrhythmia. Three days before admission, Nadolol was replaced with Metoprolol due to difficulties related to obtaining the drug; since then the patient develops episodes of palpitations and chest pain.The medical history includes Hashimoto ‘s thyroiditis, obesity and a family history of hypertrophic cardiomyopathy and CAD. The 12-lead ECG shows arrhythmia due to atrial fibrillation at a rate of 100 bpm, LBBB with secondary repolarization changes. Device interrogation revealed episodes of high frequency atrial fibrillation and atrial flutter. The ECOCG shows a non-dilated left ventricle with slightly increased thicknesses at the level of the interventricular septum and apex, with slight apical hypokinesia and preserved systolic function indices. During hospitalization, the patient ‘s condition is stabilized and she always presents with good hemodynamic compensation. Nadolol is reintroduced together with anti-coagulant therapy with low molecular weight heparins.
Danon ‘s disease represents a rare phenocopy of hypertrophic cardiomyopathy and atrial fibrillation is of particular interest in this population subgroup. Pregnancy is a hypercoagulable state and AF is an arrhythmia associated with significant thromboembolic complications. Patients with hypertrophic cardiomyopathy that develop atrial fibrillation are especially at a higher risk of thrombosis. Furthermore, exposure to beta-blockers during pregnancy has been associated with intrauterine fetal growth restriction, preterm birth and perinatal mortality. There is a non-negligible risk connected to poor fetal growth, but the risk/benefit ratio leans in favor of maternal electrical stability, which, if lacking, would still cause damage to the fetus due to hypoperfusion phenomena.