HEART SOUNDS AND MURMURS

Heart Sounds and Murmurs

Heart sounds and murmurs are fundamental components of cardiovascular examination and remain essential tools in clinical cardiology despite advances in imaging techniques such as echocardiography. Careful auscultation provides valuable information about cardiac structure, function, hemodynamics, and valvular integrity. Understanding the mechanisms that produce normal and abnormal heart sounds enables clinicians to diagnose a wide range of cardiac conditions at the bedside.

Normal Heart Sounds

The normal cardiac cycle produces two primary heart sounds: S1 and S2.

S1 (First Heart Sound)
S1 marks the onset of systole and is caused by the closure of the atrioventricular valves—the mitral and tricuspid valves. It is best heard at the apex of the heart. The intensity of S1 varies depending on factors such as PR interval, valve mobility, and ventricular contractility. A loud S1 may be heard in conditions like mitral stenosis, whereas a soft S1 may occur in mitral regurgitation or reduced ventricular function.

S2 (Second Heart Sound)
S2 signals the end of systole and the beginning of diastole. It results from closure of the semilunar valves—the aortic and pulmonary valves. S2 is best heard at the base of the heart. Physiological splitting of S2 occurs during inspiration due to delayed pulmonary valve closure. Abnormal splitting patterns (fixed, wide, or paradoxical) can indicate conditions such as atrial septal defect, right bundle branch block, or aortic stenosis.

Additional Heart Sounds

Beyond S1 and S2, additional sounds may be heard under certain physiological or pathological circumstances:

S3 (Third Heart Sound)
S3 occurs during early diastole and is associated with rapid ventricular filling. It may be normal in children, young adults, and pregnant women. In older adults, however, it often indicates volume overload or heart failure.

S4 (Fourth Heart Sound)
S4 occurs in late diastole and results from atrial contraction against a stiff ventricle. It is commonly associated with left ventricular hypertrophy, hypertension, or ischemic heart disease.

Other abnormal sounds include:

• Ejection clicks – Associated with aortic or pulmonary stenosis.

• Opening snaps – Characteristic of mitral stenosis.

• Pericardial friction rub – A scratchy sound caused by inflamed pericardial layers rubbing together, often seen in pericarditis.

Heart Murmurs

Heart murmurs are prolonged sounds produced by turbulent blood flow within the heart or great vessels. They may be innocent (physiological) or pathological.

Murmurs are classified based on timing within the cardiac cycle:

Systolic Murmurs

Occur between S1 and S2. They include:

• Ejection systolic murmurs – Caused by outflow obstruction (e.g., aortic or pulmonary stenosis).

• Pansystolic (holosystolic) murmurs – Typically due to mitral regurgitation, tricuspid regurgitation, or ventricular septal defect.

• Late systolic murmurs – Often associated with mitral valve prolapse.

Diastolic Murmurs

Occur between S2 and S1 and are almost always pathological:

• Early diastolic murmurs – Commonly due to aortic or pulmonary regurgitation.

• Mid-diastolic murmurs – Often caused by mitral or tricuspid stenosis.

Continuous Murmurs

These persist throughout systole and diastole. A classic example is patent ductus arteriosus.

Grading of Murmurs

Murmurs are graded on a scale from I to VI based on intensity:

• Grade I – Barely audible

• Grade II – Soft but clearly heard

• Grade III – Moderately loud

• Grade IV – Loud with a palpable thrill

• Grade V – Very loud, heard with stethoscope partly off chest

• Grade VI – Heard without a stethoscope

Intensity alone does not determine severity; the underlying pathology must be assessed.

Clinical Evaluation

Systematic auscultation involves examining the four primary valve areas:

1. Aortic area – Right second intercostal space

2. Pulmonary area – Left second intercostal space

3. Tricuspid area – Lower left sternal border

4. Mitral area – Apex (fifth intercostal space, midclavicular line)

Dynamic maneuvers such as inspiration, expiration, Valsalva maneuver, squatting, and handgrip can alter murmur intensity and assist in diagnosis. For example, right-sided murmurs typically increase with inspiration, while hypertrophic cardiomyopathy murmurs increase with Valsalva.

Diagnostic Significance

Although echocardiography is now the gold standard for evaluating valvular disease, auscultation remains indispensable for screening and initial assessment. Recognition of characteristic heart sounds and murmurs helps guide further investigations and management decisions.

In resource-limited settings, careful physical examination may be the primary diagnostic tool. Even in advanced healthcare environments, early detection through auscultation can expedite appropriate referral and treatment.

Conclusion

Heart sounds and murmurs reflect the mechanical events of the cardiac cycle and provide crucial insights into cardiac health. Mastery of auscultation skills enables clinicians to distinguish normal from pathological findings, assess severity, and initiate timely management. Despite technological advances, the stethoscope remains a powerful and essential instrument in cardiovascular medicine.