Types of Heart Murmurs
Heart murmurs are classified primarily by their timing in the cardiac cycle as systolic, diastolic, or continuous murmurs, with diastolic and continuous murmurs almost always representing pathological conditions requiring further cardiac evaluation. 1
Classification of Heart Murmurs
1. Systolic Murmurs
Holosystolic (Pansystolic) Murmurs
- Occur throughout systole (from S1 to S2)
- Generated by flow between chambers with widely different pressures
- Examples: Mitral regurgitation, tricuspid regurgitation, ventricular septal defect
- Almost always pathological 1
- Best heard at apex (mitral regurgitation) or left lower sternal border (tricuspid regurgitation)
Midsystolic (Ejection) Murmurs
- Crescendo-decrescendo configuration
- Start after S1 and end before S2
- Common causes:
- Aortic/pulmonic stenosis (pathological)
- Increased flow across normal valves (innocent)
- Flow into dilated vessels
- Most innocent murmurs in children and young adults are midsystolic 1
Early Systolic Murmurs
- Begin with S1 and end in mid-systole
- Less common than other systolic murmurs
Mid-to-Late Systolic Murmurs
- Begin in mid-systole and extend to S2
- Example: Mitral valve prolapse
2. Diastolic Murmurs
Early High-Pitched Diastolic Murmurs
- Begin immediately after S2
- Decrescendo configuration
- Example: Aortic regurgitation
Middiastolic Murmurs
- Begin after S2 with a delay
- Example: Mitral stenosis (low-pitched, rumbling quality at apex) 2
Presystolic Murmurs
- Occur at end of diastole
- Often associated with mitral stenosis
3. Continuous Murmurs
- Present throughout systole and diastole
- Examples: Patent ductus arteriosus, arteriovenous fistula
- Benign continuous murmurs include venous hums and mammary souffles 1
Characteristics of Murmurs
Intensity Grading (1-6)
- Grade 1: Barely audible
- Grade 2: Soft but easily audible
- Grade 3: Moderately loud, no thrill
- Grade 4: Loud with a palpable thrill
- Grade 5: Very loud, thrill palpable with stethoscope partially off chest
- Grade 6: Audible with stethoscope off the chest
Configuration
- Crescendo: Increasing intensity
- Decrescendo: Decreasing intensity
- Crescendo-decrescendo (diamond-shaped): Increases then decreases
- Plateau: Uniform intensity
Differentiating Innocent vs. Pathological Murmurs
Innocent Murmurs
- Usually grade 1-2/6 intensity
- Typically midsystolic and crescendo-decrescendo
- Lower frequencies (below 200 Hz) 3
- More harmonic frequency structure
- Often position-dependent
- No radiation
- Normal S1 and S2
- No associated symptoms or abnormal findings 4, 5
Red Flags for Pathological Murmurs
- Holosystolic or diastolic timing
- Grade 3/6 or higher intensity
- Harsh quality
- Abnormal S2
- Maximal intensity at upper left sternal border
- Systolic click
- Increased intensity on standing 6
- Frequency components over 200 Hz 3
- Murmur length over 80% of systolic duration 3
Dynamic Auscultation
Heart murmurs can change with various maneuvers, helping to identify their origin:
Respiration
- Right-sided murmurs: Increase with inspiration
- Left-sided murmurs: Louder during expiration 2
Valsalva Maneuver
- Most murmurs decrease in intensity
- Hypertrophic cardiomyopathy murmurs increase
- Mitral valve prolapse murmurs become longer/louder 2
Standing
- Most murmurs diminish
- Hypertrophic cardiomyopathy and mitral valve prolapse murmurs become louder 2
Handgrip
- Increases murmurs of mitral regurgitation, ventricular septal defect, and aortic regurgitation 2
Clinical Implications
Virtually all diastolic and continuous murmurs (except venous hums and mammary souffles) require further cardiac evaluation, typically with echocardiography 1, 4. While most systolic murmurs in children are innocent (>90%), holosystolic murmurs almost always indicate pathology requiring further evaluation 6, 5.
The presence of symptoms, abnormal physical examination findings, or conditions that increase the likelihood of structural heart disease should prompt referral to a cardiologist 6.