This asymptomatic patient has a diastolic murmur and should undergo transthoracic echocardiography (TTE). TTE is indicated for asymptomatic patients with a systolic murmur that is grade 3/6 or higher, a late or holosystolic murmur, or a diastolic or continuous murmur; TTE is also indicated for patients with a murmur and accompanying symptoms.

Chest CT may be helpful in the further evaluation of patients with documented aortic valve pathology (such as identification of a bicuspid valve or screening for concomitant aortopathy in a patient with a bicuspid aortic valve), but it would not be the first step in identifying the cause of this patient's murmur and would expose the patient to unnecessary radiation.

Exercise echocardiography stress testing is most commonly used to evaluate for coronary heart disease in those ineligible for electrocardiographic stress testing, although in selected patients it may be helpful in evaluating the hemodynamic significance of valvular disease. Diastolic murmurs tend not to vary with exercise; therefore, exercise echocardiography stress testing would not be an appropriate initial test to help clarify the cause of the murmur.

Although there are multiple benign causes of systolic murmurs, diastolic murmurs are virtually always considered abnormal. Therefore, further evaluation of this patient's cardiac findings is needed.