A patient with a history of mitral valve prolapse presents with palpitations and chest discomfort. What is the initial nursing action?

Mitral valve prolapse is a structural valvular abnormality characterized by systolic displacement of the mitral valve leaflets into the left atrium, potentially causing mitral regurgitation, arrhythmias, and autonomic symptoms such as palpitations, chest discomfort, and episodic sympathetic activation due to altered valvular mechanics. Rationale: A. Lying flat may worsen venous return changes and does not address underlying cardiac rhythm or valvular function. It may also increase perception of palpitations in some patients. It is not an appropriate initial assessment intervention. B. Assessing vital signs and auscultating the heart is the priority initial action to determine hemodynamic stability and identify potential arrhythmias or murmurs. This guides further intervention and ensures early detection of complications such as tachyarrhythmias. C. Administering antiarrhythmic medications without assessment is unsafe and inappropriate. Drug therapy should follow confirmation of rhythm disturbance and clinical evaluation. Premature administration may mask symptoms or cause adverse effects. D. Providing reassurance and deep breathing may reduce anxiety-related sympathetic stimulation, but it should only follow a focused cardiovascular assessment. It does not replace immediate evaluation of potential cardiac instability.