Familial pulmonary embolism in two siblings with first presentation as sudden cardiac arrest: a clinical case report from the Indian subcontinent

Pulmonary Embolism (PE) is recognized as a reversible cause of cardiac arrest, but continues to pose a diagnostic challenge. Additionally, a subset of patients with PE has an underlying genetic predisposition. In such cases, conventional scoring systems for PE may underestimate the probability of PE. Undiagnosed hereditary PE with first presentation as sudden cardiac arrest is an especially challenging diagnosis to make. A 21-year-old male presented to the Emergency Department with Out-of-Hospital sudden cardiac arrest, with downtime under 15 min. Cardiopulmonary resuscitation (CPR) was commenced immediately. Rhythm was persistent pulseless electrical activity, and bedside screening echocardiography during resuscitation showed a dilated right atrium and right ventricle. There were no preceding symptoms or known risk factors for pulmonary embolism at the time of resuscitation. A presumptive diagnosis of massive pulmonary embolism leading to sudden cardiac arrest was made in view of persistent pulseless electrical activity, and based on the bedside screening echocardiography findings. The patient was thrombolysed with intravenous 40 mg Tenecteplase during ongoing resuscitation. Return of spontaneous circulation was achieved within two minutes of thrombolysis, with total duration of resuscitation 21 min. Massive pulmonary embolism was confirmed subsequently on computed tomography pulmonary angiography. Patient was discharged after one week with full neurological recovery and no haemorrhagic complications. It was subsequently learned that there was a similar history of massive pulmonary embolism leading to sudden cardiac arrest in a younger sibling (which at the time had been labelled as unprovoked pulmonary embolism, and no genetic testing was advised as there was no family history of sudden cardiac arrest). As the patient was brought by by-standers, this information was not disclosed initially, but learned later. This prompted testing for genetic mutation, which revealed a heterozygous missense variant of uncertain significance in both siblings in exon 2 of SERPINC1 gene resulting in Anti-Thrombin III deficiency and leading to Haemophilia 7. This clinical case report aims to highlight non-cardiac causes of sudden, unexplained cardiac arrest; and the pertinent role of genetic testing in such cases, especially in young individuals in order to prevent future sudden cardiac deaths.