A nurse is auscultating a client's heart sounds and hears an extra heart sound before what should be considered the first heart sound S1. The nurse should document this finding as which of the following heart sounds?

A. An S4 heart sound occurs just before S1 during late diastole, caused by atrial contraction forcing blood into a stiff or hypertrophic ventricle. It is often heard in clients with hypertension, aortic stenosis, or ischemic heart disease. S4 is a pathologic finding in adults and should be documented as an extra heart sound preceding S1. B. S3 occurs just after S2 during early diastole, often associated with rapid ventricular filling. It can be normal in children and young adults but is considered abnormal in older adults, where it may indicate heart failure or volume overload. It does not occur before S1. C. A pericardial friction rub is a scratchy, high-pitched sound caused by pericardial inflammation. It is not timed with the cardiac cycle in the same way as S3 or S4 and is usually heard throughout systole and diastole. D. A split S2 occurs when the aortic and pulmonic valves close at slightly different times, producing a split during inspiration, and it is heard after S1, not before.