Mitral stenosis: Clinical sciences

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. 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. 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.