00:01
So, let's come back to COVID. And I said, you know, earlier
it's really probably not a cause
of myocarditis. So fact or fiction? A very small percentage
of patients who developed
COVID overall developed some degree of cardiac
decompensation. So a lot of people
potentially infected, not all of them are symptomatic. If
you take all comers, there's very
little incidence of cardiac decompensation. Clearly, cardiac
decompensation is much
more common in fatal cases but this in fact is certainly
multifactorial. In fact, when we
look at the histology of fatal cases of COVID-associated
myocarditis we don't see
myocarditis, we don't see a lymphocyte and macrophage-rich
infiltrate. Rather what we
see is microvascular infaraction. And in fact, we know for a
fact that in COVID we get a
hypercoagulable state and we are also stressing these
patients, they are hypoxic
so you have increased catecols, a combination of vasospasm
and increased
hypercoagulability causes microvascular thrombosis and then
we're getting
microvascular infarction but it is not myocarditis. Take it
from me. There has also been
reports of increased incidence of Kawasaki's vasculitis so
you may recall from having
listened to the vasculitis talk that we had at some other
point and Kawasaki's disease,
Kawasaki vasculitis is associated with a variety of viral
infections in kids and one of the
most feared complications is a vasculitis involving the
coronary arteries. There had been
a report of increased incidence of this particular entity in
kids who got COVID. This does
not appear to be the case. So, fact or fiction, you can tell
your friends now "Nah, there is
not really a COVID-associated myocarditis, there are cardiac
complications and
manifestations but it is not a primary infection of the
heart. Okay, what manifestations of
myocarditis can we see? So you can have an absent or minimal
symptoms. So this is really
subclinical. You can have acute disease where heart failure
develops in less than 3 months
at relatively rapid phase. We can have heart failure that
develops over greater than
3 months. So there are a whole variety of kind of temporal
sequencing of what can
happen once you have inflammation in the heart. Signs and
symptoms are related to
myocardial dysfunction. These patients will have dyspnea and
orthopnea that's due to
left heart failure. They may have chest pain or tachycardia
depending whether the
inflammation is affecting the pericardial nerves and causing
then firing of those. They
may have arrhythmias because we are destroying individual
myocytes and we therefore
may have not normal conduction cell to cell to cell. They
may have abdominal pain. Again,
this is largely related to heart failure. They may also have
right-sided heart failure with
distended jugular veins, jugular venous distention,
indicating that the heart is not
pumping well on the right side and this is another
manifestation that you get systemic
peripheral edema. When we are trying to diagnose this, as a
laboratory test we can look
for elevated troponins basically reflecting myocyte damage.
And on ECG, we see a variety
of very nonspecific things. So we can see a sinus
tachycardia as the heart is not pumping
effectively. We do see increased heart rate. We can see
nonspecific ST–T wave changes.
03:41
So the repolarization because of the myocyte injury is
abnormal, but it's in a nonspecific
pattern. And we can see a variety of arrhythmias from atrial
fibrillation to supraventricular
tachycardia to heart block depending on where the
inflammation is occurring within the
myocardium. On MRI or echocardiogram imaging, on MRI you may
see an increased
signalling for inflammation and on echocardiogram you're
going to see diminished
contractility. But again, this can be somewhat nonspecific.
And then finally, the gold
standard for diagnosing myocarditis is not the clinical
diagnostics that I've just mentioned,
but it's endomyocardial biopsy going in, taking some
snippets of the heart and sending
it off to your friendly cardiac pathologist. And with that,
we'll conclude our discussion
of myocarditis.