Myocarditis: Clinical sciences

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Introduction0:00–0:25

Myocarditis refers to the inflammation of the myocardium, which can occur due to various reasons, including viral infections, medications, as well as systemic conditions, like sarcoidosis.
Based on severity, myocarditis can range from asymptomatic and mild to life-threatening fulminant myocarditis, which is associated with heart failure!

Unstable Patient0:25–1:16

Now, if your patient presents with chief concerns suggesting myocarditis, you should first perform an ABCDE assessment to determine if they are unstable or stable.
If unstable, stabilize the airway, breathing, and circulation, which may require endotracheal intubation and mechanical ventilation.
Next, obtain IV access and start continuous vital sign monitoring, including blood pressure, heart rate, and pulse oximetry, as well as cardiac telemetry.
Myocardial inflammation can completely compromise myocardial function, so these patients could present with cardiogenic shock, requiring mechanical circulatory support and inotropes, like dobutamine!
Finally, don’t forget to provide supplemental oxygen to maintain oxygen saturation above 90 percent. Once you stabilize the patient, obtain a focused history and physical examination.

H&P, labs, ECG, TTE1:16–5:02

Next, order labs, including CRP, ESR, and cardiac troponin, and don’t forget to obtain an ECG and transthoracic echocardiography or TTE.
History typically reveals a young adult with no risk factors for ischemic heart disease, such as tobacco use, hyperlipidemia, and hypertension.
Some patients might also report recent flu-like symptoms, including fever, malaise, and headaches. Finally, myocardial inflammation results in chest pain, palpitations, as well as dyspnea, and fatigue.
Additionally, in unstable patients, there is impaired heart function, which eventually leads to congestive heart failure and symptoms, such as orthopnea and leg swelling.
Additionally, the physical exam will reveal signs of congestive heart failure, including jugular venous distention, S3 gallop, as well as lower extremity pitting edema.
Next, elevated CRP and ESR confirm the presence of inflammation, while elevated cardiac troponin confirms the myocyte damage.
Myocardial inflammation will also affect cardiac action potential and cause nonspecific ECG changes, including ST-segment elevation or depression, and T-wave inversion.
Keep in mind that the involvement of pacemaker cells can result in conduction abnormalities, like AV block! Finally, the TTE will show increased myocardial wall thickness, reduced ejection fraction, and dilation of one or both ventricles.
At this point, suspect fulminant myocarditis and order an endomyocardial biopsy, which is the gold standard to diagnose this condition, as well as cardiac magnetic resonance imaging.
Now, here’s another high-yield fact! Both ischemic heart disease and myocarditis can present with chest pain, elevated cardiac enzymes, and an abnormal echocardiogram.
However, the treatment is different, so be sure to differentiate two conditions on time! Let’s begin with chest pain.
The pain associated with ischemic heart disease is typically anginal, causing patients to feel a sensation of chest tightness and squeezing.
Additionally, this pain gets worse with physical activity and alleviates with rest. On the flip side, in myocarditis, chest pain tends to be milder, more constant, and does not change with exertion.
Moving on to the cardiac enzymes, in ischemic heart disease, you’ll find that they are markedly elevated while myocarditis tends to cause only mild elevations.
Next, the echocardiogram in acute ischemia will show wall motion abnormalities, which are limited to the area specific to the affected coronary artery.
On the flip side, in myocarditis, the echocardiogram will show abnormalities involving the entire heart. Finally, you may consider cardiac catheterization to definitively rule out ischemic heart disease, especially in cases where symptoms overlap significantly.
Now, here’s a clinical pearl to keep in mind! Occasionally, myocarditis and pericarditis can occur simultaneously, a condition known as myopericarditis.
In such cases, the physical exam will reveal a pericardial rub on heart auscultation, whereas the ECG shows diffuse ST-segment elevations and PR-segment depression.
Additionally, the TTE might reveal the presence of a pericardial effusion. Now, if the endomyocardial biopsy reveals myocardial inflammatory infiltration with or without myocyte necrosis, and cardiac magnetic resonance imaging shows myocardial edema, diagnose fulminant myocarditis!

Fulminant myocarditis5:02–6:44

Now, once you diagnose fulminant myocarditis, assess the biopsy findings! If the biopsy reveals lymphocyte infiltration, myocyte necrosis, and possible PCR identification of the viral pathogen, diagnose lymphocytic myocarditis, which typically occurs due to viral infections!
Here’s a high-yield fact to keep in mind! While viral pathogens such as coxsackievirus, influenza virus, and coronavirus, are by far the most common cause of infectious myocarditis, this condition can be associated with bacterial and protozoal infections as well.
For example, Lyme disease caused by the spirochete bacteria Borrelia burgdorferi, and Chagas disease caused by the protozoan Trypanosoma cruzi are also known to cause myocarditis.
On the other hand, if the biopsy reveals eosinophilic infiltration with no multinucleated giant cells and no granulomas, diagnose eosinophilic myocarditis!
However, if the biopsy reveals multinucleated giant cells, lymphocytes, eosinophils, and histocytes, in the absence of granulomas, diagnose Giant-cell myocarditis!
Finally, if you do find granulomas, with no eosinophils and no necrosis, diagnose sarcoidotic myocarditis! Now, once you confirm the diagnosis, focus on management.

Treatment6:44–8:04

In most cases, the management relies on supportive treatment, which primarily includes medications used to treat heart failure!
These include inotropes, as well as diuretics, ACE inhibitors, and aldosterone antagonists! If ECG reveals arrhythmias, don’t forget to treat them appropriately.
For example, some patients might require antiarrhythmics while others might benefit from a pacemaker! Additionally, in most cases, your patient will require some form of immunosuppressive therapy to reduce the myocardial inflammation!
Most commonly, this includes the use of corticosteroids, but sometimes you might need to start your patient on cyclosporine or azathioprine!
Finally, don’t forget to continue mechanical circulatory support until your patient recovers their heart function! In severe cases, the inflammation can permanently damage myocytes, leaving heart transplantation as the only treatment option.
Now, here’s a clinical pearl to keep in mind! If myocarditis occurs as a result of bacterial or parasitic infection, be sure to initiate antimicrobial medications, like doxycycline for Lyme disease, and antiprotozoals like nifurtimox for Chagas disease.
Alright, now that we’re done with unstable patients, let’s go back and take a look at stable individuals! In this case, you should also start by obtaining a focused history and physical examination, as well as labs, including inflammatory parameters CRP and ESR, and cardiac troponin!

Stable patients - H&P, Labs, ECG, TTE8:04–9:27

Also, be sure to order ECG and TTE! Again, history will usually reveal a young adult with no risk factors for ischemic heart disease, sometimes with a report of recent flu-like symptoms.
Next, your patient will often report mild chest pain or palpitations, often in combination with mild dyspnea and exercise intolerance!
Next, since there’s no impairment of heart function, the physical exam will reveal no signs of congestive heart failure.
However, labs will also reveal elevated inflammatory markers and mildly elevated cardiac troponin levels! Additionally, on rare occasions, the ECG might reveal nonspecific changes, like ST-segment elevation or depression and T-wave inversion.
Finally, the TTE will show increased myocardial wall thickness with normal or mildly reduced ejection fraction. With these findings, you should suspect mild myocarditis, so be sure to order cardiac magnetic resonance imaging.

Mild myocarditis9:27–10:59

If the cardiac magnetic resonance imaging confirms myocardial edema, diagnose mild myocarditis. Keep in mind that mild myocarditis can be caused by the same conditions as fulminant myocarditis, but since you are not going to pursue a myocardial biopsy you will be unable to make a definitive diagnosis.
Regardless of the cause, the management of mild myocarditis primarily relies on rest and a physical exercise restriction, for at least six months!
Finally, don’t forget to perform regular follow-ups with ECG and TTE to evaluate the patient’s myocardial function! Now, here’s one last clinical pearl to keep in mind!
In both mild and fulminant myocarditis, you should always rule out medication- or toxin-induced myocarditis! In this case, your patient will often report using specific medications or drugs known to trigger myocardial inflammation.
Examples include certain antibiotics like penicillin, antipsychotics such as clozapine, immune checkpoint inhibitors like pembrolizumab, and even some vaccines, including COVID-19 and smallpox.
Additionally, some substances can trigger myocardial inflammation, most commonly cocaine and amphetamines. Finally, don’t forget to check for accidental exposure to known cardio-toxins, like snake venom or insect stings, which can also result in myocardial inflammation!

Review10:59–11:50

Alright, as a quick recap… Myocarditis refers to the inflammation of the myocardium. It is commonly seen in younger patients, with symptoms including fever, chest pain, exercise intolerance, and features of congestive heart failure.
Workup typically reveals arrhythmias, elevated cardiac enzymes, and echocardiogram findings consistent with heart failure.
The gold standard for diagnosis is the endomyocardial biopsy, revealing inflammatory infiltrate and myocyte necrosis. The most common cause of myocarditis is viral infection, but it can also result from medication or toxin exposure.
Management involves addressing the underlying cause, providing supportive treatment to improve cardiac symptoms and preserve myocardial function, and immunosuppressive therapy to reduce myocardial inflammation.
Myocarditis: Clinical Sciences: Video and Causes | Osmosis