Mitral stenosis: Clinical sciences

Chapters:

Watch video only

Introduction 0:00–1:09

Mitral stenosis is a condition in which mitral valve opening is narrowed, most commonly due to calcification of the leaflets, or rheumatic heart disease.
This narrowing obstructs the inflow of blood into the left ventricle resulting in reduced diastolic filling, stroke volume, and, in turn, cardiac output.
Additionally, the valvular narrowing can cause build-up of blood within the left atrium leading to elevated pressure within it as well as the pulmonary artery, which can lead to pulmonary edema.
Now, as the right side of the heart has to pump harder to overcome the increased pressures, right ventricular hypertrophy develops.
Over time, this can progress to right heart failure. Because the right heart can no longer pump enough blood to fill the left heart, there is an inadequate preload to the left ventricle, leading to reduced ejection fraction.
Mitral stenosis is classified into 4 stages A through D, which represent the progressing severity of the disease. Alright, when a patient presents with a chief concern suggestive of mitral stenosis, your first step is to perform the ABCDE assessment to determine if they are stable or unstable.

Unstable 1:09–4:57

If unstable, initiate acute management by stabilizing the airway, breathing, and circulation. Make sure to obtain IV access and provide supplemental oxygen, in addition to continuous vital sign monitoring.
Next, obtain a focused history and physical exam. as well as labs including CBC, CMP, BNP, and cardiac enzymes.
Be sure to get an ECG and a transthoracic echocardiogram, or TTE. Now, the history might reveal dyspnea at rest or on exertion, orthopnea, weakness, extremity swelling, abdominal bloating, rapid weight gain, and palpitations.
Exam might reveal tachycardia with or without hypotension, respiratory distress, and pitting edema of the extremities. Since we are talking about cardiogenic shock, the patient will appear cool and clammy, cyanotic, with cold extremities, and cold sweat.
On auscultation, you might hear a diastolic rumble, a loud S1, and an opening snap. In some patients, you might even find an irregular heart rhythm due to atrial fibrillation or A fib.
Labs might show normal CBC, electrolyte abnormalities, and elevated BNP, but normal cardiac enzymes. On ECG, you might see left axis deviation, P mitrale, and A fib in some cases.
Finally, on echo you can expect to see severe mitral stenosis with decreased ventricular function. Okay, if these are your findings, you can diagnose decompensated heart failure from severe mitral stenosis.
Here’s a high-yield fact! If the patient presents with cardiogenic shock but has elevated cardiac enzymes, think acute coronary syndrome.
And here’s a clinical pearl! Some ECG findings in mitral stenosis come from the left atrium enlargement.
For example, P mitrale is a bifid or biphasic P wave seen on leads II and V1. It is a common finding in patients with rheumatic heart disease.
This occurs when the left atrium becomes enlarged leading to slower depolarization creating the bifid look of the P wave.
Similarly, A fib in patients with mitral stenosis occurs as a result of atrial stretching and remodeling from the backed-up blood in the left atrium.
As the left atrium stretches to accommodate the increased blood volume, it disrupts the neural fibers responsible for the conduction of the heart.
Alright, let’s talk about treatment. Medical management of these patients is focused on improving heart function, starting with inotropic support.
Once the heart is able to squeeze harder and push blood through the restricted valve, you can attempt diuresis. Taking the volume down helps the heart get back on the Starling curve which improves contractility.
Next is rate control. This is best done by cardioversion in the setting of atrial fibrillation and hypotension.
Keep in mind that medications are only a temporary measure until the patient can get to the cath lab. So, obtain an emergent cardiology consultation for a percutaneous mitral balloon commissurotomy, or PMBC for short.
If the cardiology team cannot successfully open the valve, get an emergent surgical consultation for valve replacement. Okay, now that the unstable patients are taken care of, let’s go back to ABCDE and talk about stable ones.

Stable 4:57–6:07

Your next step here is to obtain a focused history and physical exam. Keep in mind that most individuals with early-stage disease can be asymptomatic.
However, some patients might report decreased exercise tolerance, dyspnea on exertion, fatigue, weight gain, and palpitations.
They might also have risk factors such as a history of rheumatic fever, atherosclerotic disease, hypertension, or diabetes.
On physical exam, you might see mauve discoloration of the patient’s cheeks, also known as mitral facies, due to vasoconstriction secondary to the low cardiac output.
You may also see lower extremity edema indicating heart failure. On auscultation, you can expect to hear a diastolic rumble, loud S1, and an opening snap.
In some cases, you might also find a new-onset arrhythmia, most commonly atrial fibrillation. If these are your findings, suspect mitral stenosis.
The next step of your workup includes an ECG, chest x-ray, and an echocardiogram, which is the diagnostic modality of choice.

Diagnostic evaluation 6:07–7:47

ECG might reveal right ventricular hypertrophy, left atrial enlargement, P mitrale, and atrial fibrillation in some cases.
The chest X-ray might show pulmonary congestion and a double-density sign created by the silhouette of the enlarged left atrium appearing near the silhouette of the right atrium.
Now, on echo, you can expect to see a reduced mitral valve opening area with thickened leaflets, calcifications, and reduced mitral leaflet motion.
These findings confirm your diagnosis of mitral stenosis. Once you’ve made the diagnosis, your next step is to assess the stage of stenosis.
This is done by grading the stenosis based on echo findings. Stage A shows valve changes with nothing that meets the criteria for stenosis.
B is mild to moderate, while C and D are severe. Here’s a clinical pearl!
The velocity of blood flowing across a valve is a great estimate of how narrow the valve is. This is because flow accelerates when it is pushed through a small opening.
This is similar to what happens when you put your thumb over the end of a garden hose. The flow speeds up and sprays out harder.
Also, back pressure in the hose develops, just like it would in the left atrium, causing enlargement. Finally, the water coming out under pressure makes sound, which is the same reason we can hear a heart murmur through a stenotic valve.
Alright, stage A is the mildest form of the disease. These patients have some changes on echo putting them at risk of developing stenosis, but they are not affecting the blood flow across the valve.

Stage A 7:47–8:07

Medical management includes annual follow-up with an echo every 3 to 5 years to monitor for disease progression. Next up, stage B refers to mild to moderate mitral stenosis.

Stage B 8:07–8:44

This stage indicates progressive disease because here, you can see the stenosis of the valve and the beginning stages of the compensatory mechanisms of backed-up blood flow.
Medical management includes diuretics to avoid fluid overload, rate control with beta-blockers or calcium channel blockers, and anticoagulation if there is A fib.
These patients will also need a stress test and a follow-up echo every 3 to 5 years or sooner if they develop symptoms. Now, stage C means that the patient has severe mitral stenosis with signs of heart compensation, but no symptoms yet.

Stage C 8:44–9:15

This is referred to as asymptomatic severe disease. The medical management includes diuretics, beta-blockers or calcium channel blockers, and anticoagulation if A fib is present.
These patients will need an echo every 1 to 2 years. Make sure to refer the patient for multidisciplinary consultation for PMBC.
Finally, stage D refers to symptomatic severe disease. Patients require medical management that includes diuretics, beta-blockers or calcium channel blockers, and anticoagulation if A fib is present.

Stage D 9:15–9:40

More importantly, these patients need an urgent multidisciplinary consultation for PMBC or a surgical mitral valve repair or replacement.
Alright, as a quick recap… Mitral stenosis refers to the narrowing of the mitral valve opening commonly from calcifications or rheumatic heart disease.

Review 9:40–10:18

Unstable patients presenting with decompensated heart failure need to be treated right away with an urgent PMBC or surgical valve replacement.
For stable patients, treatment is based on the stage of the disease. Treatment typically involves medical management to optimize cardiac function as well as multidisciplinary consultation for PMBC or valve repair or replacement in severe disease.