Which of the following conditions is indicated if atrial fibrillation is present without a clear secondary cause?

Atrial fibrillation can occur without a clear secondary cause, and in such cases, it is often associated with certain valvular heart diseases. Specifically, conditions like mitral stenosis or mitral regurgitation can create structural and hemodynamic changes in the heart that predispose patients to the development of atrial fibrillation. These valvular issues disrupt normal blood flow through the heart and can lead to atrial dilation and fibrosis, facilitating the arrhythmia.

Considering other conditions, while myocardial infarction, hypertensive crisis, and systemic electrolyte imbalances can lead to atrial fibrillation, they are typically identified as secondary causes for the rhythm disturbance. If atrial fibrillation arises without an obvious contributing factor, assessing for underlying valvular heart diseases becomes critical, as they represent a primary and chronic predisposition to this arrhythmia. Thus, in this scenario, the presence of atrial fibrillation suggests an investigation into these specific heart conditions.