During auscultation, the nurse hears a loud ______ sound immediately after S2, suggesting possible aortic regurgitation.

A diastolic murmur occurring immediately after S2 is characteristic of aortic regurgitation. This high-pitched, blowing sound is caused by blood flowing backward through an incompetent aortic valve during diastole.

Aortic Regurgitation (AR):
- Early diastolic decrescendo murmur
- Best heard at left sternal border, 3rd/4th intercostal space
- Associated symptoms: wide pulse pressure, water-hammer pulse
- Causes: endocarditis, rheumatic fever, aortic root dilation
- Austin Flint murmur: mid-diastolic rumble in severe AR
- Physical findings: head bobbing, Corrigan's pulse, pistol-shot sounds
- ECG changes: left ventricular hypertrophy
- Complications: left ventricular failure
- Treatment options: valve replacement, medical management
- Diagnostic tests: echocardiogram, cardiac catheterization
- Risk factors: hypertension, connective tissue disorders
- Grading: mild, moderate, severe based on regurgitant fraction
- Prevention: endocarditis prophylaxis in high-risk patients