From the Guidelines
Systolic murmurs occur during heart contraction, typically between the first and second heart sounds, and are often caused by blood flowing through narrowed valves or abnormal flow, whereas diastolic murmurs happen during heart relaxation and are almost always pathological. The key difference between systolic and diastolic murmurs lies in their timing and the phase of the cardiac cycle during which they occur. Systolic murmurs are generated by the flow of blood from the ventricles into the arteries or other chambers during contraction 1.
Types of Systolic Murmurs
- Holosystolic (pansystolic) murmurs, which occur throughout the entire systolic phase, are often associated with regurgitant flow between chambers with significantly different pressures, such as between the left ventricle and the left atrium or right ventricle 1.
- Midsystolic (systolic ejection) murmurs start after the first heart sound and are typically crescendo-decrescendo in configuration, occurring when blood is ejected across the aortic or pulmonic outflow tracts 1.
- Early systolic murmurs begin with the first sound and end in midsystole, often due to tricuspid regurgitation without pulmonary hypertension or acute mitral regurgitation 1.
- Late systolic murmurs are soft, high-pitched murmurs at the left ventricular apex, starting well after ejection and ending before or at the second heart sound, often due to apical tethering and malcoaptation of the mitral leaflets 1.
Diastolic Murmurs
Diastolic murmurs, on the other hand, occur during the relaxation phase of the heart, between the second and first heart sounds, and are almost always indicative of a pathological condition 1. They are typically caused by conditions such as aortic or pulmonic valve regurgitation, or mitral stenosis, where there is an abnormal flow of blood into the ventricles during diastole 1. Early diastolic murmurs begin with or shortly after the second heart sound, when the ventricular pressure drops below that in the aorta or pulmonary artery, and are often high-pitched 1. The distinction between systolic and diastolic murmurs, based on their timing and characteristics, is crucial for the diagnosis and management of underlying cardiac conditions.
From the Research
Systolic Murmur vs Diastolic Murmur
- A systolic murmur is a common presentation of aortic regurgitation detected by echocardiography, as found in a study published in 2004 2.
- Systolic murmurs are the most common murmurs in clinical practice, and their proper examination is fundamental to cost-effective care 3.
- The loudness of a systolic murmur in aortic stenosis correlates best with peak momentum transfer, and thus with body size, making it less reliable in larger patients 4.
- Echocardiography can provide insights into the origin of systolic murmurs, and the diagnostic accuracy of physical examination for pathologic murmurs can be improved by considering the distribution of the murmur on the chest wall 5.
- Diastolic murmurs, on the other hand, indicate important underlying valvular pathology requiring further investigation, typically with echocardiography 3.
- A study published in 2004 found that diastolic murmurs were rare, occurring in only 2% of patients with no aortic regurgitation, and in 14% of patients with moderate aortic regurgitation 2.
Key Differences
- Systolic murmurs occur during systole, while diastolic murmurs occur during diastole.
- Systolic murmurs are more common and can be benign, while diastolic murmurs are less common and often indicate significant valvular pathology.
- The intensity of systolic murmurs can be influenced by body size, while diastolic murmurs are often associated with specific valvular lesions.
Clinical Implications
- A systolic murmur in patients at risk for aortic valve disease should prompt a more thorough physical examination for aortic regurgitation 2.
- The assessment of the patient with a systolic murmur should be reappraised, and guidelines should be followed to improve the recognition of aortic stenosis in the community 6.
- Echocardiography is a valuable tool in the diagnosis and management of patients with systolic and diastolic murmurs 3, 5.