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Cardiac amyloidosis is an under-recognized and potentially fatal cause of heart failure and other cardiovascular manifestations. It is caused by deposition of misfolded precursor proteins as fibrillary amyloid deposits in cardiac tissues. The two primary subtypes of systemic amyloidosis causing cardiac involvement are immunoglobulin light chain (AL), a plasma cell dyscrasia, and transthyretin (ATTR), itself subdivided into a hereditary subtype caused by a gene mutation of the ATTR protein, and an age-related wild type, which occurs in the absence of a gene mutation. Clinical recognition requires a high index of suspicion, inclusive of the extracardiac manifestations of both subtypes. Diagnostic workup includes screening for serum and/or urine monoclonal protein suggestive of immunoglobulin light chains, along with serum cardiac biomarker measurement and performance of cardiac imaging for findings consistent with amyloid infiltration. Modern cardiac imaging techniques, including the use of nuclear scintigraphy with bone-seeking radiotracer to noninvasively diagnose ATTR cardiac amyloidosis, have reduced reliance on the gold standard endomyocardial biopsy. Disease-modifying therapeutic approaches have evolved significantly, particularly for ATTR, and pharmacologic therapies that slow or halt disease progression are becoming available. This Canadian Cardiovascular Society/Canadian Heart Failure Society joint position statement provides evidence-based recommendations that support the early recognition and optimal diagnostic approach and management strategies for patients with cardiac amyloidosis. This includes recommendations for the symptomatic management of heart failure and other cardiovascular complications such as arrhythmia, risk stratification, follow-up surveillance, use of ATTR disease-modifying therapies, and optimal clinical care settings for patients with this complex multisystem disease.

We present a case of digoxin toxicity in the context of dehydration, renal dysfunction and concomitant use of the macrolide antibiotic, clarithromycin, which is known to inhibit P-glycoprotein-mediated efflux mechanisms of digoxin. A focused review of the literature is presented. Health care providers need to be vigilant of this mechanism of drug-drug interaction, which is also relevant to other commonly used cardiovascular drugs.