What is the difference between systolic and diastolic heart murmurs and how can they be remembered?

Understanding Heart Murmurs: Systolic vs. Diastolic

The Critical Distinction

Diastolic murmurs virtually always represent pathological conditions and require further cardiac evaluation, while most systolic murmurs are benign and related to physiological increases in blood flow velocity. 1

Timing in the Cardiac Cycle

Systolic Murmurs (Between S1 and S2)

Systolic murmurs occur during ventricular contraction and are classified into four types: 1

• Holosystolic (Pansystolic): Begin with S1 and continue throughout systole until S2, generated when blood flows between chambers with widely different pressures throughout systole (left ventricle to left atrium or right ventricle) 2, 3

  • Common causes: Mitral regurgitation, tricuspid regurgitation, ventricular septal defect 2
  • Key feature: Plateau-shaped configuration 2

• Midsystolic (Ejection): Crescendo-decrescendo configuration, starting shortly after S1 when ventricular pressure rises sufficiently to open the semilunar valve 1

  • Common causes: Aortic stenosis, pulmonic stenosis, or innocent flow murmurs 1
  • Key feature: Diamond-shaped, peaks in mid-systole 1

• Early systolic: Begin with S1 but fade before S2 1

• Late systolic: Begin mid-to-late in systole, classic example is mitral valve prolapse with click 1

Diastolic Murmurs (After S2)

Diastolic murmurs occur during ventricular filling and are categorized by timing: 1, 4

• Early diastolic: High-pitched, decrescendo murmurs starting immediately after S2 4

  • Common causes: Aortic regurgitation, pulmonic regurgitation 4

• Mid-diastolic: Lower-pitched rumbling murmurs 1, 4

  • Common causes: Mitral stenosis, tricuspid stenosis 4

• Presystolic: Crescendo murmurs occurring just before S1 1

The "Inching" Technique for Timing

Use the "inching" method to accurately time murmurs: keep S2 in mind as your reference point and move the stethoscope from the aortic area to the apex. 5

• If the murmur occurs before S2, it is systolic 5
• If the murmur occurs after S2, it is diastolic 5
• This simple bedside technique prevents misclassification 5

Mnemonic for Remembering Key Murmurs

"PASS" for Pansystolic Murmurs:

• Prolapse (mitral valve with severe regurgitation)
• Atrial septal defect with shunt (actually causes midsystolic, but helps remember VSD)
• Septal defect (ventricular)
• Systolic regurgitation (mitral and tricuspid) 2, 3

"DREAD" for Diastolic Murmurs (Always Pathologic):

• Diastolic = Disease (always pathologic) 1
• Regurgitation (aortic or pulmonic) - early diastolic
• Early diastolic = high-pitched, decrescendo
• Aortic regurgitation most common
• Decrescendo or rumbling (stenosis) 4

Clinical Pearls for Differentiation

Location and Radiation

• Mitral regurgitation: Best heard at apex, radiates to axilla 2
• Tricuspid regurgitation: Loudest at lower left sternal border 2
• Aortic stenosis: Right upper sternal border, radiates to carotids 1

Dynamic Maneuvers

• Right-sided murmurs: Increase with inspiration (increased venous return) 2, 4
• Left-sided murmurs: Louder during expiration 2, 4
• Hypertrophic cardiomyopathy: Increases with Valsalva maneuver 4

Innocent vs. Pathologic Systolic Murmurs

An innocent murmur is grade 1-2/6, crescendo-decrescendo, mid-systolic without radiation, often position-dependent, and requires no workup in asymptomatic patients with normal physical capacity. 6

Pathologic features requiring echocardiography: 6, 7

• Holosystolic or any diastolic murmur 6, 7
• Grade ≥3/6 intensity 1
• Maximal intensity at upper left sternal border 7
• Radiation to neck or axilla 7
• Associated symptoms or abnormal cardiac findings 1

Common Pitfalls to Avoid

• Do not assume systolic murmurs are always benign: Up to 86% of patients with moderate aortic regurgitation present with systolic murmurs, not the classic diastolic murmur 8

• Pressure on the stethoscope eliminates S4 gallops but not ejection sounds or split S1: This helps differentiate extra sounds from murmurs 5

• Fixed splitting of S2 with midsystolic murmur suggests atrial septal defect: This associated finding changes the differential diagnosis entirely 1, 4

• Summation gallops (S3 + S4 occurring simultaneously) can mimic valvular murmurs: These occur in decompensated heart failure and may be louder than S1 or S2 5

When to Order Echocardiography

Echocardiography is essential for all diastolic murmurs, continuous murmurs (except venous hums and mammary souffles), and any systolic murmur with pathologic features or in patients at risk for valvular disease. 1, 3

Specific indications: 3, 7

• Any diastolic murmur 1
• Pansystolic murmurs of unknown cause 3
• Symptomatic patients with any murmur 3
• Systolic murmurs in patients at risk for aortic valve disease 8
• Any abnormal physical examination findings suggesting structural heart disease 7