How do I differentiate between systolic and diastolic murmurs?

Distinguishing Between Systolic and Diastolic Murmurs

Systolic and diastolic murmurs can be distinguished primarily by their timing in relation to heart sounds, with systolic murmurs occurring between S1 and S2, and diastolic murmurs occurring between S2 and the next S1. 1

Timing and Classification

Systolic Murmurs

Systolic murmurs occur during ventricular contraction, between the first (S1) and second (S2) heart sounds. They can be further classified as:

1. Holosystolic (pansystolic) murmurs:

   • Begin with S1 and continue throughout systole until S2
   • Constant intensity throughout systole
   • Caused by flow between chambers with widely different pressures (e.g., mitral regurgitation, tricuspid regurgitation, ventricular septal defects) 1, 2

2. Midsystolic (ejection) murmurs:

   • Start shortly after S1 and end before S2
   • Typically crescendo-decrescendo (diamond-shaped) configuration
   • Associated with blood flow across semilunar valves (aortic/pulmonic)
   • Can be innocent or pathological (e.g., aortic stenosis) 1

3. Early systolic murmurs:

   • Begin with S1 and end in midsystole
   • Often due to tricuspid regurgitation without pulmonary hypertension or acute mitral regurgitation 1

4. Late systolic murmurs:

   • Start well after ejection and end before or at S2
   • Often high-pitched at the apex
   • Commonly associated with mitral valve prolapse 1

Diastolic Murmurs

Diastolic murmurs occur during ventricular relaxation, between S2 and the next S1. They are almost always pathological and include:

1. Early diastolic murmurs:

   • Begin with or shortly after S2
   • Usually high-pitched and decrescendo
   • Typically caused by aortic or pulmonic regurgitation 1

2. Middiastolic murmurs:

   • Occur during early ventricular filling
   • Usually due to mitral or tricuspid stenosis
   • Can also occur with increased flow across normal valves 1

3. Presystolic murmurs:

   • Begin during ventricular filling after atrial contraction
   • Require sinus rhythm
   • Usually due to mitral or tricuspid stenosis 1

Distinguishing Features

Pitch and Quality

• Systolic murmurs: Often medium to high-pitched
• Diastolic murmurs: Early diastolic murmurs are typically high-pitched, while mid and late diastolic murmurs are low-pitched and rumbling 1

Clinical Significance

• Most systolic murmurs, especially midsystolic ones, may be innocent (physiological)
• Diastolic murmurs are virtually always pathological and require further cardiac evaluation 1

Dynamic Auscultation Techniques

Dynamic maneuvers can help differentiate between various murmurs:

Maneuver	Effect on Murmur
Respiration	Right-sided murmurs increase with inspiration; left-sided murmurs are louder during expiration [1]
Valsalva	Most murmurs decrease in intensity, except HCM (increases) and MVP (becomes longer/louder) [1]
Standing	Most murmurs diminish, except HCM and MVP which become louder [1]
Squatting	Most murmurs become louder, except HCM and MVP which soften [1]
Handgrip	Increases murmurs of MR, VSD, and AR [1]

Practical Approach to Auscultation

1. Identify S1 and S2 as reference points

   • Use the "inching" technique: move the stethoscope gradually from the aortic area to the apex to accurately time sounds 3
   • Remember that S1 coincides with carotid upstroke

2. Determine timing of the murmur:

   • If between S1 and S2 → systolic murmur
   • If between S2 and next S1 → diastolic murmur
   • If spanning S2 → continuous murmur

3. Analyze configuration and duration of the murmur:

   • Holosystolic vs. midsystolic vs. early/late systolic
   • Early diastolic vs. middiastolic vs. presystolic

4. Apply dynamic maneuvers to further characterize the murmur

Common Pitfalls to Avoid

1. Mistaking a split S1 or S2 for a murmur

   • Apply pressure with the stethoscope: pressure doesn't eliminate splitting of heart sounds but may diminish certain murmurs 3

2. Confusing tachycardia-induced summation gallops for murmurs

   • When S3 and S4 occur simultaneously, they can create a sound louder than S1 or S2 3

3. Overlooking diastolic murmurs

   • These are quieter and higher-pitched than systolic murmurs
   • Use the diaphragm of the stethoscope and have the patient lean forward and exhale

4. Assuming all systolic murmurs are benign

   • Holosystolic murmurs, harsh quality, and grade 3 or greater intensity suggest pathology 2, 4

5. Missing murmurs in patients with emphysema

   • Listen over the xiphoid or epigastric area in patients with increased anteroposterior chest diameter 3

Remember that while cardiac auscultation is valuable for initial evaluation, echocardiography is recommended for definitive diagnosis when pathological murmurs are suspected or when the exact cause of a murmur cannot be determined with certainty 5.