Stephen Clarkson

Background Mitochondrial cardiomyopathy (MCM) is an alteration in cardiac structure and function caused by gene mutations or deletions affecting components of the mitochondrial respiratory chain. We report a case of MCM presenting as cardiogenic shock, ultimately requiring left ventricular assist device (LVAD) placement. Case summary A 35-year-old woman with chronic weakness and non-ischaemic cardiomyopathy, on home dobutamine, was referred to our institution for heart transplantation evaluation. She was admitted to the hospital for suspected cardiogenic shock after laboratory tests revealed a lactate level of 5.4 mmol/L (ref: 0.5–2.2 mmol/L). Her hospital course was complicated by persistently undulating lactate levels (0.2–8.6 mmol/L) that increased with exertion and did not correlate with mixed venous oxygen saturation measurements obtained from a pulmonary artery catheter. Electrodiagnostic testing demonstrated a proximal appendicular and axial myopathy. A left deltoid muscle biopsy was performed that demonstrated evidence of a mitochondrial disease on light and electron microscopy. Muscle genetic testing revealed two large-scale mitochondrial deoxyribonucleic acid sequence deletions, confirming the diagnosis of MCM. She subsequently underwent LVAD placement, which was complicated by significant right ventricular failure requiring early mechanical support. She was ultimately discharged home with chronic inotropic support. Discussion Mitochondrial cardiomyopathy in adults is a diagnostic and therapeutic challenge. Prompt diagnosis should be made in patients with unknown causes of heart failure via skeletal muscle histopathology guided by electrodiagnostic studies, and targeted genetic testing in affected tissue. Outcomes in adult MCM patients who receive an LVAD are unknown and warrant further investigation.

Background Over the past 2 years, the utilization of venovenous extracorporeal membrane oxygenation (VV-ECMO) for the treatment of coronavirus disease 2019 (COVID-19) acute respiratory distress syndrome (ARDS) has increased. While supporting respiratory function, VV-ECMO requires large-bore indwelling venous cannulas, which risk bleeding and infections, including endocarditis. Case summary We describe two adults hospitalized for COVID-19 pneumonia who developed ARDS and right-ventricular failure, requiring VV-ECMO and ProtekDuo cannulation. After over 100 days with these devices, both patients developed tricuspid valve vegetations. Our first patient was decannulated from ECMO and discharged, but re-presented with a segmental pulmonary embolism and tricuspid mass. The Inari FlowTriver system was chosen to percutaneously remove both the tricuspid mass and pulmonary thromboembolism. Pathological examination of the mass demonstrated Candida albicans endocarditis in the setting of Candida fungemia. Our second patient developed a tricuspid valve vegetation which was also removed with the FlowTriever system. Pathological examination demonstrated endocarditis consistent with Pseudomonas aeruginosa in the setting of Pseudomonas bacteremia. Both patients experienced resolution of fungemia and bacteremia after percutaneous vegetation removal. After ECMO decannulation and percutaneous debulking, both patients experienced prolonged hospital stays for ventilator weaning and were eventually discharged with supplemental oxygen. Discussion VV-ECMO and right-ventricular support devices are invasive and create various risks, including bloodstream infection and infective endocarditis. Percutaneous debulking of valvular vegetations associated with these right-sided indwelling devices may be an effective means of infection source control. It is unclear whether prolonged use of VV-ECMO provides a mortality benefit in COVID-19 ARDS.