What causes palpitations in a patient with mitral stenosis?

Palpitations in Mitral Stenosis: Pathophysiological Mechanisms

Palpitations in mitral stenosis are primarily caused by atrial fibrillation resulting from left atrial enlargement and increased left atrial pressure. This occurs due to the obstructed mitral valve opening that forces blood to back up into the left atrium 1.

Pathophysiological Sequence in Mitral Stenosis

1. Narrowing of the Mitral Valve Opening

   • Mitral stenosis is characterized by restricted leaflet mobility and narrowed valve opening
   • Typically caused by rheumatic heart disease with commissural fusion 1
   • Can also occur in degenerative/calcific mitral stenosis without commissural fusion 2

2. Increased Left Atrial Pressure and Enlargement

   • The stenotic valve creates resistance to blood flow from left atrium to left ventricle
   • This leads to pressure buildup in the left atrium
   • Multiple regression analysis shows that severity of mitral stenosis accounts for 38% of left atrial enlargement 3
   • Left atrial enlargement is significantly greater in patients with mitral stenosis and atrial fibrillation (37.6 ± 10.8 cm²) compared to those in sinus rhythm (27.8 ± 7.7 cm²) 3

3. Development of Atrial Fibrillation

   • Chronic pressure overload causes marked structural and electrical remodeling of the left atrium 4
   • Atrial fibrillation is a common complication of mitral stenosis
   • The frequency of persistent AF increases with age 4
   • Atrial fibrillation contributes to further enlargement of both left and right atria 3

4. Manifestation as Palpitations

   • Atrial fibrillation causes irregular heartbeats perceived as palpitations
   • The rapid, irregular rhythm is often the first symptom that brings patients to medical attention
   • Palpitations may be intermittent (paroxysmal AF) or persistent 4

Clinical Implications and Management

1. Diagnostic Approach

   • Echocardiography is essential for diagnosis and evaluation of mitral stenosis 1
   • Assess mitral valve area, transmitral gradient, and pulmonary artery pressure 1
   • Evaluate for left atrial enlargement and presence of thrombi 1

2. Management of Atrial Fibrillation in Mitral Stenosis

   • Mandatory anticoagulation regardless of CHA₂DS₂-VASc score 4
   • Rate control with beta-blockers, digoxin, or heart rate-regulating calcium channel blockers 1
   • Vitamin K antagonists are preferred over NOACs in moderate to severe mitral stenosis 1, 4

3. Definitive Treatment

   • Percutaneous mitral balloon valvotomy (PMC) is first-line therapy for severe symptomatic mitral stenosis with favorable valve morphology 1
   • Surgical intervention (repair or replacement) for unfavorable valve anatomy 1
   • PMC does not prevent AF occurrence but should be considered when AF is associated with severe symptomatic mitral stenosis 4

Important Considerations

• Atrial fibrillation worsens hemodynamic tolerance of mitral stenosis and increases thromboembolic risk 4
• The presence of atrial fibrillation has a negative impact on natural history of mitral stenosis and outcomes after commissurotomy 4
• Cardioversion may be considered after successful intervention if atrial fibrillation is of recent onset and left atrium only moderately enlarged 1
• Regular follow-up with clinical and echocardiographic assessment is essential 1

Common Pitfalls to Avoid

• Failing to anticoagulate patients with mitral stenosis and atrial fibrillation
• Using NOACs instead of vitamin K antagonists in moderate to severe mitral stenosis
• Attempting cardioversion without addressing the underlying valve pathology
• Overlooking the need for regular follow-up in asymptomatic patients with mild stenosis

In conclusion, palpitations in mitral stenosis primarily result from atrial fibrillation, which develops due to left atrial enlargement and increased pressure caused by the narrowed mitral valve opening. Management should focus on both rhythm/rate control and addressing the underlying valvular pathology.