Acquired Myocarditis

00:01 So let's shift gears away from the endocardium into the myocardium or the muscle of the heart, and let's talk about acquired myocarditis.

00:11 Most acquired myocarditis is viral.

00:16 That's a pretty high-yield question right there -- Coxsackie B virus causing viral myocarditis.

00:22 Other viruses absolutely cause it, though, including adenovirus, hepatitis C, Epstein-Barr virus or cytomegalovirus.

00:30 Most viruses can cause it, Coxsackie B is the most common culprit.

00:37 COVID-19 virus can also cause acute myocarditis.

00:42 If myocarditis is not viral, it could be from another infection.

00:47 Examples of this are bacteria, for example, Rickettsial diseases can cause it.

00:54 Lyme disease can cause it -- remember Lyme disease is Borrelia burgdorferi.

00:58 And not seen so much in the United States but in South America, Chaga's Disease can cause it, and that's a protozoa.

01:05 There are also non-infectious causes of myocarditis: autoimmune or environmental.

01:13 Autoimmune diseases like Kawasaki Disease, rheumatic fever, collagen vascular disease can all cause inflammation of the myocardium.

01:21 And then very rarely, environmental causes exist as well, a variety of toxins and drugs.

01:27 But these other infectious causes and environmental and autoimmune causes are quite rare compared to the viral causes which are by far the most common.

01:37 When you think of viral causes you often think, "Well, it's gonna be a benign condition," but acquired myocarditis, even if viral, can be very, very dangerous.

01:49 These viral causes often causes fever, flu-like symptoms, and irritability in children.

01:55 If they get severe, they can go into congestive heart failure.

01:59 And they can have complete muscle failure of that ventricle which can cause all kinds of systemic problems.

02:06 They can develop dyspnea, they can have a poor appetite, they can have exercise intolerance.

02:13 You may notice hepatosplenomegaly or an S3 or an S4 on exam.

02:18 Remember, the S3 and the S4 are a resulting sound from a non-compliant stiff ventricle.

02:26 Well, if that myocardium is inflamed it's not gonna be very compliant.

02:30 These patients can develop arrhythmias because of irritation and interruption of the electrical system through the myocardium.

02:40 They may develop ventricular tachycardia or any degree of heart block that you can find on EKG.

02:47 They can also have an associated pericarditis and we'll talk about that in a bit, but you may hear a friction rub on exam if they have an associated pericarditis.

02:58 So you're worried about this. You obtain a chest x-ray and oftentimes a chest x-ray will just show a large heart.

03:05 You may have pulmonary vascular congestion if they're having some right-sided failure as well.

03:11 An EKG will show low voltage QRSes, and that's very important to remember.

03:19 The voltage on those QRSes across the board on that EKG are gonna be a lot lower as you can see in this picture.

03:25 Patients may have inverted T waves; they may have wide QRS complexes; and they may have ST-segment changes, and all of these are possible in acquired myocarditis.

03:39 The echo is really where you're gonna get at what the problem is and you can see visually on the echocardiogram that there's poor functioning of that myocardium.

03:49 If you suspect acquired myocarditis, we will often obtain viral serology, especially Coxsackie titers.

03:58 But you'all also get any other blood testing as indicated depending on what the suspected cause is as we discussed in the various causes.

04:06 But remember: Coxsackie and viral titer testing is usually obtained.

04:12 So, how do we treat it? Well, in cases of acquired myocarditis that are mild, it's mostly supportive therapy.

04:21 We may provide ionotropes and provide some afterload reduction, and there's some controversy about IVIg.

04:31 Most people use IVIg simply because we think it might help.

04:36 But when you look at the evidence it's somewhat controversial.

04:40 There's a Cochrane review showing not much benefit.

04:43 But then again, these patients are potentially so sick we worry they may get worse off an IVIg as indicated.

04:50 In severe disease, we may provide with a ventricular assist device or patients may require a heart transplant.