From the Guidelines
Mild Systolic Anterior Motion (SAM) of the Mitral Valve (MV) is primarily caused by conditions such as hypertrophic cardiomyopathy, and it can be incidental or progress depending on the underlying cause, with regular monitoring and management being crucial to prevent complications. The causes of mild SAM can be varied, including:
- Hypertrophic cardiomyopathy, as stated in the 2024 AHA/ACC/AMSSM/HRS/PACES/SCMR guideline for the management of hypertrophic cardiomyopathy 1
- Post-mitral valve repair
- Dehydration
- Use of certain medications that increase heart contractility Mild SAM may not necessarily progress in all cases, particularly if it's related to temporary conditions like dehydration or medication effects. However, if it's associated with underlying structural heart disease like hypertrophic cardiomyopathy, it may worsen over time, as the 2024 guideline highlights the dynamic nature of left ventricular outflow tract obstruction (LVOTO) in HCM, which is sensitive to ventricular preload, afterload, and contractility 1. Some key points to consider in the management of mild SAM include:
- Regular cardiac follow-up with repeat echocardiograms every 1-2 years to monitor for progression
- Avoiding dehydration and excessive physical exertion
- Potential use of beta-blockers like metoprolol to reduce contractility and outflow obstruction in cases related to hypertrophic cardiomyopathy, as suggested by the 2024 guideline 1 The mechanism behind SAM involves abnormal flow patterns in the left ventricle that pull the mitral valve leaflet toward the septum during systole, potentially causing left ventricular outflow tract obstruction in severe cases, which can be identified and managed according to the guidelines 1.
From the Research
Causes of Mild Systolic Anterior Motion (SAM) of the Mitral Valve (MV)
- Systolic anterior motion (SAM) of the mitral valve can be caused by various factors, including hypertrophic cardiomyopathy (HCM) 2, 3, 4, 5, valvular or chordal SAM 2, and postural changes 6.
- In HCM, SAM can occur due to the asymmetrically hypertrophied left ventricle, which can cause the mitral valve to move anteriorly during systole, resulting in left ventricular outflow tract (LVOT) obstruction 2, 3, 4.
- SAM can also occur in patients without HCM, such as those undergoing left intrapericardial pneumonectomy, and can be a cause of unexplained sudden hypotension in perioperative settings 6.
Incidental or Progressive SAM
- Mild SAM can be incidental, as seen in a case where a 29-year-old male was found to have asymmetrically hypertrophied left ventricle with systolic motion of anterior mitral valve on 2D transthoracic echocardiography (TTE) 2.
- However, SAM can also progress over time, as seen in a case where a 78-year-old woman with progressive HCM developed significant LVOT obstruction and prominent SAM, which later regressed after extensive left atrial (LA) and left ventricle (LV) remodeling 4.
- The progression or regression of SAM can depend on various factors, including the underlying cardiac condition, geometric and kinetic changes, and the presence of mitral regurgitation 4, 5.
Diagnosis and Management
- Echocardiography, including 2D and 3D imaging, and stress echocardiography, plays a central role in diagnosing SAM and assessing its severity 2, 5.
- Cardiac magnetic resonance imaging can also be used to understand the dynamic nature of SAM, especially in anatomically atypical hearts 5.
- Management of SAM can include medical therapy, aggressive volume loading, and beta-adrenoceptor blockade, with surgery being the final option 5.