Heart Murmurs Classification and Characteristics

Types of Heart Murmurs

• The American Heart Association describes innocent murmurs as common in children and adults, representing turbulent flow not associated with structural cardiac defects 1
• The American College of Cardiology notes that pathologic murmurs are associated with structural cardiac defects that require further evaluation 1
• Still's murmur is an innocent murmur with medium pitched, vibratory character heard at the apex and sternal borders 1
• Venous hum is the closest to a "croaking" sound, with medium pitched, blowing character and diastolic accentuation, heard at right or left upper sternal border 1, 2
• Innocent pulmonary systolic murmur is a medium pitched, harsh character heard at left middle and upper sternal border 1

Characteristics of Venous Hum

• Venous hum is heard at the right or left upper sternal border 1
• It has a medium pitched, blowing character with diastolic accentuation 1
• Venous hum disappears with jugular venous compression or when the patient lies supine 2
• It is common in children and pregnant women 3

Other Continuous Innocent Murmurs

• Mammary souffle is a medium or high pitched, blowing character with continuous flow and systolic accentuation heard over or above the breasts 1
• Mammary souffle disappears with compression of breast tissue 1
• It is heard in late stages of pregnancy or early puerperium 3

Clinical Significance and Evaluation

• Referral to a cardiologist is recommended for diastolic murmurs (except confirmed venous hum) 4
• Holosystolic murmurs require referral to a cardiologist 4
• The American College of Cardiology recommends considering patient position and maneuvers that can alter murmur characteristics during evaluation 4
• Failing to recognize that innocent murmurs can sometimes be relatively loud (grade 3) and still not represent pathology can lead to over-investigation 5