What is the clinical significance and management of a Split S1 (first heart sound)?

From the Guidelines

A split S1 heart sound is generally a normal variant that rarely requires specific management, and its clinical significance is minimal in most cases, as it can be heard in healthy individuals. The split S1 occurs when the mitral and tricuspid valve closures are not perfectly synchronized, creating two distinct components to the first heart sound 1. This phenomenon can be influenced by various factors, including respiratory phase, with the split becoming more pronounced during expiration due to prolonged right-sided filling time. In certain conditions, such as right bundle branch block, Ebstein's anomaly, or left atrial myxoma, a split S1 may become more noticeable. However, management should focus on addressing any underlying cardiac condition if present, rather than treating the split S1 itself. Key points to consider in the management and interpretation of a split S1 include:

• Distinguishing a split S1 from other cardiac findings like S4 gallops or ejection clicks, as these may have different clinical implications.
• Recognizing that a split S1 is best heard at the lower left sternal border or apex using the diaphragm of the stethoscope.
• Considering further cardiac evaluation, including ECG, echocardiography, or referral to a cardiologist, if a patient presents with a newly identified split S1 along with symptoms such as dyspnea, palpitations, or syncope, to rule out pathological causes. It's also important to note that the presence of a normally split second heart sound can be a reliable finding in excluding the possibility of severe aortic stenosis, as indicated in guidelines for the management of patients with valvular heart disease 1. Overall, the approach to a split S1 should prioritize the evaluation and management of any underlying cardiac conditions, with the split S1 itself not typically requiring specific treatment.

From the Research

Clinical Significance of Split S1

• The clinical significance of a split S1 (first heart sound) is related to its differentiation from other heart sounds, such as the fourth heart sound (S4) and ejection sounds 2.
• A split S1 can be distinguished from an S4 by applying pressure on the stethoscope, which eliminates the S4 but not the splitting of S1 2.
• The splitting of S1 is a common finding and can be recorded graphically in a significant percentage of subjects, regardless of the presence of disease 3.

Management and Diagnosis

• The management of a split S1 involves accurate diagnosis and differentiation from other heart sounds and murmurs 2.
• The technique of "inching" can be used to accurately time heart sounds and murmurs, helping to diagnose conditions such as systolic clicks and diastolic gallops 2.
• Echocardiography can be used to evaluate patients with heart failure and to identify those who may benefit from biventricular pacing, although the presence of a split S1 is not a specific indicator for this treatment 4.

Relationship to Other Conditions

• A split S1 can be associated with various conditions, including coronary heart disease, hypertensive heart disease, and dilated cardiomyopathy 2.
• The presence of a split S1 does not necessarily denote heart failure, and its clinical significance should be evaluated in the context of other diagnostic findings 2.
• Incomplete right bundle branch block (IRBBB) can also present with a split S1, and clinicians should be aware of the challenges in diagnosing this condition using electrocardiogram (ECG) 5.