Purpose of Review <p>To summarize the recent literature examining the degree of overlap among atrial fibrillation (AF), heart failure (HF), and left atrial (LA) dysfunction, the prognostic relevance of finding a second condition in one of the other disease states, and the treatment effects for one condition on the secondary entities.</p> Recent Findings <p>If one condition (AF, HF, or LA dysfunction) is present, there are very high prevalences of a second condition demonstrated across several cohorts. Additionally, the presence of a second condition consistently has a negative impact on prognosis. Treatment effects for AF or HF tend to show bidirectional benefit, whereas data is limited toward impacts on LA dysfunction.</p> Summary <p>Patients with AF, HF, or LA dysfunction often have more than one of these conditions (either clinically manifest or occult), which may influence prognosis. Established treatment pathways for AF or HF tend to show benefits in the second condition, whereas there is limited data to determine effects on LA dysfunction, or whether LA dysfunction may be directly targeted for therapy.</p>