Mitral stenosis Flashcards
What is the pathophysiology of mitral stenosis?
Mitral stenosis (MS) arises from a thickening of the mitral valve leaflets that obstructs blood flow from the left atrium to the left ventricle. This obstruction results in increased pressure within the left atrium, the pulmonary vasculature, and the right ventricle and atrium. Increased pressure due to obstruction of blood flow from the left atrium to the left ventricle leading to left atrial pressure increases and elevation in pulmonary pressures.
What is the pitch (high or low) associated with mitral stenosis?
The murmur of mitral stenosis is a soft, low-pitched rumble best heard with the bell of the stethoscope at the cardiac apex, which is located in the fifth intercostal space (between the 5th and 6th ribs) at the left mid-clavicular line. It is often helpful if the patient exhales and lies in the left lateral decubitus position. The murmur is an opening snap followed by a mid diastolic rumble with a loud S1 and a loud P2.
A shorter interval in mitral stenosis is a positive finding or negative finding?
Negative finding. A shorter interval indicates more severe stenosis. On auscultation, the best indicator of mitral stenosis (MS) severity is the length of time between S2 (specifically the A2 component, caused by aortic valve closure) and the opening snap (OS). The OS occurs due to abrupt tensing of the valve leaflets as the mitral valve reaches its maximum diameter during forceful opening. As MS worsens, left atrial pressures increase due to impaired movement of blood into the left ventricle. Higher pressure causes the valve to open more forcefully; as a result, the A2-OS interval becomes shorter as left atrial pressure increases. The current standard for diagnosis and determination of MS severity is measurement of mean transvalvular pressure gradients via 2-D Doppler echocardiography.
What is the Normal Mitral Valve Area at the mitral annulus and when does stenosis of the mitral valve become problematic?
- The normal opening is 5 to 6 cm^2 at the mitral annulus.
- Below 1.5 cm^2 is when symptoms tend to appear.
What is the most common risk factor for development of mitral stenosis?
The most common cause of MS is rheumatic fever. Involvement of the mitral valve is thought to occur in up to 90% of individuals with rheumatic heart disease. Rheumatic heart disease can develop as late as 10-20 years after the initial episode of rheumatic fever following infection with Group A Streptococcus (S. pyogenes). It is important to note that early antibiotics for Group A Strep will mitigate the risk for developing rheumatic heart disease however early antibiotics do not prevent the development of poststreptococcal glomerulonephritis.
Why is pregnancy a high risk condition with mitral stenosis?
Pregnant women with MS are at risk for atrial fibrillation and pulmonary edema due to physiologic hypervolemia and increased left atrial and pulmonary venous pressure. Increased cardiovascular demand can hasten symptom development in patients with mitral stenosis. The normal physiologic changes of pregnancy include increases in plasma volume, heart rate, and cardiac output starting in the first trimester. These changes create increased flow across the mitral valve (evidenced by a prominent diastolic murmur at the apex), which can lead to worsening symptoms in previously stable patients with mitral stenosis. These patients may experience a relatively abrupt worsening of dyspnea on exertion and should be evaluated for pregnancy as the precipitating cause.
What clinical symptoms are associated with mitral stenosis due to increased pulmonary pressures?
Exertional Dyspnea (shortness of breath with exercise), decreased exercise tolerance, coughing up blood (hemoptysis). Patients can progress to right sided heart failure (peripheral edema and hepatomegaly). Chronic mitral stenosis can progress to compression of the esophagus (more common) leading to dysphagia or odynophagia or the recurrent laryngeal nerve leading to hoarseness.
Why does mitral stenosis lead to right ventricular hypertrophy?
Chronic elevated pulmonary pressure leads to fibrosis, requiring the right ventricle to work harder to pump blood into the pulmonic circulation. Eventually right axis deviation from right ventricular hypertrophy causes right high failure.
What EKG findings are associated with right ventricular hypertrophy?
peaked R-waves in V1 and V2
What are the clinical symptoms secondary to right ventricular heart failure secondary to mitral stenosis?
Mitral facies (pinkish-purple patches on cheeks), paroxysmal nocturnal dyspnea, orthopnea, and JVD. Advanced disease may lead to edema, pleural effusions, and hepatic congestion.
What EKG finding is commonly associated with mitral stenosis?
p-mitrale; this is a biphasic (double) p-wave which follows left atrial enlargement, “broad-notched p-wave.”
What clinical symptom is common due to mitral stenosis secondary to atrial enlargement?
- compression of the esophagus (more common).
- voice hoarseness due to compression of the recurrent laryngeal nerve (Ortner syndrome).
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The posterior mediastinal portion of the esophagus lies just behind the left atrium and is at risk of being compressed and/or displaced by an enlarged left atrium, leading to dysphagia (difficulty swallowing). The more common clinical manifestation in mitral stenosis is esophageal compression due to left atrial (LA) enlargement. Esophageal compression occurs with severe mitral stenosis with left atrial enlargement >5 cm.Compression of the recurrent laryngeal nerve (Ortner’s syndrome) is less common but a classic finding. The vagus nerves lie posterior to the hila of the lungs bilaterally. They are therefore unlikely to be compressed by cardiac enlargement with massive left atrial enlargement (>6 cm). Patients may then present with hoarseness of voice.
Why does hemoptysis occur in mitral stenosis?
Bronchial venous dilation.
What arrhythmia is associated with mitral stenosis?
atrial fibrillation
What murmur is associated with mitral stenosis?
Opening snap followed by a low-pitched mid-diastolic rumble.
Where is mitral stenosis best heard?
Apex of the heart (5th intercostal space, midclavicular line).
Is the pitch for mitral stenosis high or low, and does this have any implications for how to auscultate this murmur?
The murmur associated with mitral stenosis is a low-pitched mid-diastolic murmur with an opening snap that is best heard at the midclavicular line at the apex.
What is the best position to appreciate mitral stenosis?
Left lateral decubitus position.
Describe the S1 in mitral stenosis?
“loud FIRST heart sound”
What maneuver would decrease the intensity of mitral stenosis?
Inspiration.
Mitral stenosis is dependent on left atrial pressure to drive blood through a stenotic mitral valve, a decreased left atrial volume transiently reduces murmur intensity during inspiration. Inspiration may slightly decrease the murmur intensity of mitral stenosis, but this effect is often subtle. The lager effect is often more appreciated with valsalva or abrupt standing.
Inspiration = ↑ right-sided murmurs, ↓ left-sided murmurs (including MS).
How does expiration alter the intensity of mitral stenosis?
The best phase of respiration to appreciate mitral stenosis is during expiration (increases left-sided murmur intensity).
Expiration = ↑ left-sided murmurs (e.g., mitral stenosis, aortic regurgitation).
Describe the P2 in mitral stenosis
Also loud!
What is the method of diagnosing mitral stenosis?
Echo (transthoracic) with CXR and EKG as supportive.
Echocardiography: increased LA size with normal LV size, increased transmitral flow velocity, mitral valve thickening and calcification, and decreased valve mobility.
When patients experience atrial fibrillation, what anticoagulation is used to prevent thrombotic events?
warfarin.
