The subject line was ominous: “Probably the scariest thing I've read about Covid in months.” The email was from a physician and friend of mine who has both had Covid-19 and taken care of Covid-19 patients who are hospitalized.
This must be serious.
What news could be scary to the guy who had already been infected when the numbers of infected patients, ICU admissions, and positive test rate across the country hadn’t really changed recently? Just when we start to feel like we’re understanding how to treat this thing, now do we have to confront new horrors?
The story he sent me was an article from STAT news on the lasting impact Covid-19 leaves on the heart. This news made it to the daily American College of Cardiology email blast and quite a few major news outlets.
There are two different papers that these headlines are based on - one that found damage to cardiac tissue on MRI and one that found virus particles on autopsy in the hearts of patients who died.
Let’s take a look at what the 2 papers showed and, more importantly, what it means in reality.
How much heart damage does Covid-19 really cause?
The cardiac MRI study looked at a randomly selected group of 100 patients with confirmed Covid infection, about a third of whom required hospital admission.
They did cardic MRIs on the Covid-19 patients about 10 weeks after confirmed infection and compared the results to cardiac MRIs done on patients who weren’t infected.
The top line report is scary - more than 3/4 of the patients had “structural changes to their hearts” or “evidence of a biomarker signaling cardiac injury typically found after a heart attack.”
But when you actually dig into the numbers, things look a little bit less grave.
We measure cardiac function with something called an ejection fraction. A normal value is over 55%. The average patient in the Covid group had an ejection fraction of 56%, compared to about 60% for the non-Covid group.
This was statistically significant, but of questionable clinical significance.
The same pattern extends to the biomarkers - an absolute difference in the numbers, but overall magnitude of the numbers being fairly unimpressive quantitatively.
In my view, the most notable part of the study is the description of scar tissue forming in the heart (late gadolinium enhancement, or LGE, for those MRI aficionados). Patients with Covid were twice as likely as matched non-Covid patients to have evidence of scar in the heart.
The scar tissue data suggests the cardiac impact may be permanent.
Is this all that different than the flu?
Unfortunately, the answer is yes.
I looked to see if there were any cardiac MRI studies done after flu infection to see if this leg to lasting changes on cardiac imaging. I found a study looking at patient 3 months post H1N1 infection who were suspected to have cardiac involvement at the time of their illness.
All of the patients with the flu had their cardiac MRIs normalize at 3 months post infection.
So the fact that these findings persist with Covid-19 raise some alarms.
What about the SARS-CoV-2 that they found in the hearts of dead people?
The autopsy study looked at 39 patients who had died with a confirmed diagnosis of Covid-19.
They performed autopsies on the bodies and found viral genetic material (RNA) in the muscle tissue of the heart in 24 of them (around 60% of the patients).
Two thirds of the patients with viral RNA had very high levels of RNA in there, indicating a lot of virus in the heart. Interestingly, there didn’t seem to be different amounts of inflammation related to the presence of viral genetic material.
The patients in this study didn’t die of cardiac dysfunction - they predominantly died of pneumonia - and they didn’t even seem to have clinical evidence of cardiac dysfunction before death.
This is food for thought without clear real world relevance - after all, the presence of viral particles in the heart may just be a reflection of how sick you were. And who cares if you have viral fragments in your heart if you survive and go back to your regular life?
We know that the influenza virus can also be found in cells from the heart on autopsy - but it’s not immediately clear what to think about the real world relevance of this info.
So what do we take from this?
This doesn’t really change much about how I think of Covid-19 right now.
We already know that a lot of people have died. We already know that there’s potential for long term effects from this virus. But these findings do raise alarm bells.
The two studies put together start to tell a story of a physiologic explanation for cardiac dysfunction (viral particles found in the heart on autopsy) with evidence of cardiac dysfunction seen in patients (mildly reduced cardiac function on MRI).
But I’m not persuaded we know enough to draw conclusions. Do the cardiac findings that we’ve just discussed actually matter?
It certainly raises a number of additional questions:
How does this cardiac damage evolve over a longer time frame?
Do these patients have increased risk of congestive heart failure? Of death from cardiac causes?
Does treating patients with cardio-protective medications like beta blockers reduce the cardiac damage from Covid?
What is the long term functional status of these patients? Are their lives limited by cardiac dysfunction?
Smart researchers are tackling these questions as we speak.
So I’ll leave you with this: just because something is statistically significant doesn’t mean that it is clinically significant. But just because you don’t want something to be clinically significant doesn’t mean that it isn’t.
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