What is the management of Systolic Anterior Motion (SAM) of the mitral valve identified on a 2D (two-dimensional) echo?

Management of Systolic Anterior Motion (SAM) of the Mitral Valve

Beta-blockers and volume loading are the first-line medical therapy for systolic anterior motion of the mitral valve, followed by septal reduction therapy for drug-refractory cases with significant obstruction. 1

Diagnosis and Assessment

• SAM is defined as abnormal anterior movement of the mitral valve leaflet(s) toward the interventricular septum during systole, causing left ventricular outflow tract obstruction (LVOTO) and mitral regurgitation

• Echocardiographic evaluation is essential for:

  • Measuring LVOT gradient at rest and with provocative maneuvers
  • Assessing mitral regurgitation severity and direction
  • Examining mitral valve anatomy for intrinsic abnormalities
  • Evaluating left ventricular hypertrophy pattern

• Key diagnostic findings:

  • Posteriorly directed mitral regurgitation jet suggests SAM-related MR
  • Centrally or anteriorly directed jets suggest intrinsic mitral valve disease 1
  • Hemodynamically significant LVOT obstruction is defined as ≥50 mmHg 2

Management Algorithm

1. Medical Management (First-Line)

• Beta-blockers: First-line therapy to reduce contractility and LVOT gradient
• Volume loading: Aggressive fluid resuscitation to increase LV cavity size
• Avoid vasodilators and inotropes: These can worsen LVOT obstruction
• Discontinue vasopressors if possible, as they can exacerbate SAM 3

2. Monitoring Response

• Repeat echocardiography to assess:
  • LVOT gradient reduction
  • Improvement in mitral regurgitation
  • Resolution of SAM
• Conservative management is successful in most cases (93% of patients) 4
• In post-mitral valve repair patients, SAM resolves before hospital discharge in 71% of cases 4

3. Septal Reduction Therapy (For Refractory Cases)

For patients with persistent symptoms and LVOT obstruction ≥50 mmHg despite optimal medical therapy:

• Surgical myectomy: Preferred for younger patients and those with concomitant cardiac conditions requiring surgery

• Alcohol septal ablation: Alternative for older patients or those at high surgical risk

• During surgical intervention:

  • Intraoperative transesophageal echocardiogram (TEE) is recommended to assess mitral valve anatomy and adequacy of septal myectomy 2
  • For patients undergoing alcohol septal ablation, TTE or intraoperative TEE with intracoronary ultrasound-enhancing contrast injection is recommended 2

Special Considerations

In Hypertrophic Cardiomyopathy (HCM)

• SAM is present in approximately 75% of HCM patients 1
• Provocative maneuvers (standing, Valsalva, exercise) are recommended if minimal gradients (<30 mmHg) are observed at rest 2
• Dobutamine should NOT be used to identify latent LVOTO due to lack of specificity 2

Post-Mitral Valve Repair

• Risk factors for SAM after mitral valve repair include:
  • Lower ratio of anterior to posterior leaflet heights
  • Younger age
  • Lower end-systolic left ventricular volume
  • Presence of bileaflet prolapse
  • Male sex 4
• Use of an incomplete annuloplasty band rather than a complete ring is associated with lower incidence of SAM 5

Follow-up and Monitoring

• For patients with HCM and SAM, repeat transthoracic echocardiography every 1-2 years to assess:

  • Degree of myocardial hypertrophy
  • Dynamic LVOTO
  • Mitral regurgitation
  • Myocardial function 2

• For patients who have undergone septal reduction therapy, TTE within 3-6 months after the procedure is recommended to evaluate results 2

• More frequent monitoring is warranted if there is a change in clinical status or new symptoms develop 2