What is most likely increased in a patient with severe mitral stenosis, presenting with shortness of breath and fatigue?

Pulmonary Artery Pressure is Most Likely Increased in Severe Mitral Stenosis

In a patient with severe mitral stenosis presenting with progressive shortness of breath and fatigue, pulmonary artery pressure is most likely increased. 1

Pathophysiology of Mitral Stenosis and Pulmonary Hypertension

Mitral stenosis (MS) causes mechanical obstruction to left ventricular inflow at the level of the mitral valve. This obstruction leads to:

1. Increased left atrial pressure
2. Pulmonary venous congestion
3. Elevation of pulmonary vascular resistance
4. Development of pulmonary hypertension

According to the ACC/AHA guidelines, "elevation of pulmonary vascular resistance is an important physiological event in MS, and the level of pulmonary pressure is an indicator of the overall hemodynamic consequence." 1

Clinical Evidence in This Patient

Several clinical findings in this patient strongly support pulmonary hypertension:

• Progressive shortness of breath over 5 years
• Fatigue and dyspnea with mild exertion
• Respiratory rate of 26/min (tachypnea)
• Right ventricular lift along left sternal border (indicating right ventricular pressure overload)
• History of severe shortness of breath during pregnancy (when cardiac output increases)

Hemodynamic Changes in Mitral Stenosis

When evaluating the options:

• Pulmonary artery pressure: Significantly increased due to the backward transmission of pressure from the stenotic mitral valve 1
• Blood flow to lower lung fields: Actually decreased, not increased, as pulmonary hypertension leads to redistribution of blood flow to upper lung zones
• Diastolic filling time: Decreased, not increased, due to tachycardia (pulse 100/min) which shortens diastole
• Left-to-right shunt: Not present in isolated mitral stenosis
• Left ventricular end-diastolic pressure: Usually normal or decreased in pure MS as the stenotic valve protects the left ventricle from volume overload 1

Quantifying Pulmonary Hypertension in Mitral Stenosis

The guidelines indicate that moderate pulmonary hypertension is defined as pulmonary artery systolic pressure greater than 50 mm Hg at rest 1. In severe MS, pulmonary artery pressures can be significantly higher, especially with exertion.

Hemodynamic studies in patients with MS show:

• Mean pulmonary artery pressures in the mid-40s mm Hg or higher 1
• Pulmonary artery systolic pressures can reach 76/37 mm Hg (mean 52 mm Hg) in severe cases 1

Clinical Implications

The development of pulmonary hypertension in MS has important prognostic and therapeutic implications:

• Indicates advanced disease with significant hemodynamic compromise
• Associated with worse outcomes and higher mortality
• May warrant earlier intervention even in asymptomatic patients 1
• Patients with moderate pulmonary hypertension at rest and pliable mitral valve leaflets may be considered for percutaneous mitral valvotomy 1

Common Pitfalls in Assessment

• Underestimating the severity of MS based on symptoms alone
• Failing to recognize pulmonary hypertension as a marker of hemodynamic significance
• Not considering intervention in patients with significant pulmonary hypertension even if they deny symptoms 1

The presence of right ventricular lift in this patient is a critical physical finding that directly indicates right ventricular pressure overload from pulmonary hypertension, making pulmonary artery pressure the parameter most likely to be increased in this scenario.