Diastolic Murmurs: Types and Auscultatory Findings
Diastolic murmurs are categorized into three distinct types based on their timing in diastole: early diastolic, middiastolic, and presystolic murmurs, each with characteristic acoustic properties and underlying pathophysiology. 1
Early Diastolic Murmurs
Early diastolic murmurs begin immediately with or shortly after S2, occurring when ventricular pressure drops below aortic or pulmonary artery pressure 1:
High-Pitched Decrescendo Murmurs
- Aortic regurgitation (AR): High-pitched, decrescendo quality reflecting rapid decline in regurgitant flow during diastole
- Pulmonic regurgitation with pulmonary hypertension: Similar high-pitched, decrescendo character 1
Low-to-Medium Pitched Murmurs
- Pulmonic regurgitation without pulmonary hypertension: Low-to-medium pitched with slightly delayed onset because regurgitant flow is minimal at valve closure when the reverse pressure gradient is minimal
- Common after tetralogy of Fallot repair 1
Key distinguishing feature: The pitch directly correlates with the pressure gradient—high pressure gradients (AR, pulmonary hypertension) produce high-pitched murmurs, while low gradients produce lower-pitched sounds.
Middiastolic Murmurs
Middiastolic murmurs originate primarily from the mitral and tricuspid valves during early ventricular filling, reflecting disproportion between valve orifice size and diastolic blood flow volume 1:
Primary Causes
- Mitral stenosis: Most common cause
- Tricuspid stenosis: Less common
Flow-Related Causes (Increased Diastolic Flow)
- Severe mitral or tricuspid regurgitation (flow across regurgitant valve)
- Ventricular septal defect or patent ductus arteriosus (flow across normal mitral valve)
- Atrial septal defect (flow across normal tricuspid valve) 1
Austin-Flint Murmur
- Characteristics: Low-pitched, rumbling diastolic murmur at LV apex in severe chronic AR
- Timing: May be middiastolic or presystolic
- Critical finding: Opening snap is absent in isolated AR, distinguishing it from mitral stenosis 1
Presystolic Murmurs
Presystolic murmurs begin during ventricular filling following atrial contraction and require sinus rhythm 1:
Primary Causes
- Mitral stenosis: Most common
- Tricuspid stenosis
- Atrial myxoma (right or left): Can mimic stenotic valve murmurs 1
Critical caveat: These murmurs disappear in atrial fibrillation due to loss of organized atrial contraction.
Modifying Maneuvers
Understanding how murmurs change with physiologic maneuvers aids diagnosis 1:
- Respiration: Right-sided diastolic murmurs increase with inspiration; left-sided murmurs louder during expiration
- Exercise/Handgrip: Murmurs from AR increase with handgrip; stenotic valve murmurs (MS) increase with both isotonic and isometric exercise
- Amyl nitrite: Distinguishes Austin-Flint murmur (decreases) from true MS (increases during tachycardia phase) 1
Clinical Pitfalls to Avoid
Prosthetic valves: Diastolic murmurs of prosthetic AR and MS are often very soft and difficult to hear on auscultation—maintain high index of suspicion 2
Hypertrophic cardiomyopathy: Can produce diastolic murmurs (mid-diastolic or early diastolic) related to impaired LV compliance or mid-ventricular obstruction—not widely recognized but clinically important 3, 4, 5
Any diastolic murmur warrants investigation: Unlike systolic murmurs (which may be innocent), diastolic murmurs indicate important underlying valvular pathology requiring echocardiography 6, 7
Sensitivity limitations: In population studies, diastolic murmurs are rare but highly specific (>99%) when detected; however, their absence does not exclude valvular disease 7