Low-Flow, Low-Gradient Aortic Stenosis in Transthyretin Cardiac Amyloidosis: Diagnostic and Therapeutic Challenges-A...

Background: In low-flow, low-gradient aortic stenosis (LFLG AS), restricted aortic valve opening may represent either fixed valvular obstruction or flow-dependent incomplete leaflet opening due to reduced forward flow. Aortic stenosis (AS) and transthyretin cardiac amyloidosis (ATTR-CM) may coexist, making it difficult to distinguish myocardial disease-driven low-flow physiology from clinically relevant valvular obstruction. Case Presentation: An 88-year-old man presented with decompensated heart failure and paradoxical LFLG AS. Dobutamine stress echocardiography (DSE) failed to restore normal flow, and the calculated aortic valve area remained within the severe range despite stress. Computed tomography showed a low aortic valve calcium score (AVCS) of 313 Agatston units, leaving true-severe versus pseudo-severe AS indeterminate. Further evaluation confirmed wild-type ATTR-CM. Because the contribution of AS to heart failure was uncertain, the patient was initially managed with optimized heart failure therapy. Approximately two years later, he was readmitted with recurrent acute decompensated heart failure, severe left ventricular systolic dysfunction, dobutamine dependency, end-organ congestion, and a classical LFLG AS phenotype. Although AS severity remained indeterminate, a clinically relevant valvular afterload component could not be excluded. At that time, tafamidis was not immediately available because of local access limitations. Because left ventricular assist device implantation and heart transplantation were not feasible and surgical aortic valve replacement carried prohibitive risk, transcatheter aortic valve implantation (TAVI) was performed after discussion by the Heart Team. Left ventricular ejection fraction improved early after TAVI, from 19.9% before the procedure to 29.4% at 3 days and 44.1% at 35 days. At 1-year follow-up, left ventricular ejection fraction remained improved at 51%, and more than two years after TAVI, the patient continues regular outpatient follow-up without recurrent heart failure hospitalization. Conclusions: In ATTR-CM with LFLG AS, DSE and AVCS may not definitively determine AS severity. Carefully selected TAVI, combined with ATTR-directed and optimized heart failure therapy, may be associated with early left ventricular functional recovery and sustained clinical improvement.