5. Cytokine Storm
Clinicians think the “cytokine storm” may be the reason why some sick patients’ health is deteriorating so quickly. A cytokine storm is when the level of cytokines needed to signal a healthy immune response is beyond what is needed to fight the virus. As a result, the immune cells fight against the virus, but also against healthy tissues by mistake. This can cause drops in blood pressure, blood clots, leaky blood vessels and organ failure.
High levels of cytokines have been present in the blood of infected patients in some studies. “The real morbidity and mortality of this disease is probably driven by this out of proportion inflammatory response to the virus,” says pulmonologist Jamie Garfield, from his experience at Temple University Hospital treating COVID-19 patients.
However, others disagree. Pulmonary critical care physician Joseph Levitt at the Stanford University School of Medicine argues, “There seems to have been a quick move to associate COVID-19 with these hyperinflammatory states. I haven’t really seen convincing data that that is the case.” Levitt is concerned that reducing the cytokine response could cause other damage. Current clinical trials are testing certain cytokines in infected patients. Levitt worries these drugs may inhibit the immune system from fighting the virus. He says, “There’s a real risk that we allow more viral replication.”
4. Reviewing the Heart
Other scientists are studying the virus’s impact on the heart and blood vessels and arguing this is the real reason the virus can become deadly.
In Italy, a woman in her 50s entered the emergency room with all the signs of a heart attack. Tests of her heart and blood indicated her heart muscles were showing scarring and swelling. In addition, more testing showed an incredibly weak left ventricle only pumping a third of the typical amount of blood. However, when dye was injected into her coronary arteries, they showed no blockages to prove a heart attack. How was this possible? Another test came back positive, this one for COVID-19.
At this time, it is unknown how the virus damages blood vessels and the heart, but studies are showing this is common. JAMA Cardiology confirmed that around 80 of 416 coronavirus patients studied in Wuhan, China had heart damage. Heart arrhythmias were also present in 44% of patients from another Wuhan study.
The blood itself is also being affected. According to a paper in Thrombosis Research, in a Dutch ICU, 38% of the 184 COVID-19 patients experienced abnormal blood clots and a third of them have preexisting clots. In COVID-19 patients, pulmonary embolism has proven deadly when blood clots break up and end up blocking critical arteries in the lungs. Stroke can also occur if these arteries clots transfer to the brain. Behnood Bikdeli, who specializes in cardiovascular medicine at Columbia University Medical Center, has seen many infected patients with a high number of blood clot byproducts such as D-dimer. Bikdeli says, “The more we look, the more likely it becomes that blood clots are a major player in the disease severity and mortality from COVID-19.”
Constriction in the blood vessels has also been occurring in infected patients. Some experience reduced blood flow in the fingers and toes, causing pain, swelling, and tissue damage.
Blood clots play an important role in the COVID-19 infection, making it deadly to some patients. In trying to understand how COVID-19 has caused pneumonia in some patients, blood vessel constriction in the lungs may be the answer. This also explains why some patients’ blood oxygen levels are very low, but they aren’t gasping for air. One theory is that the virus may be offsetting the hormones responsible for blood pressure regulation and allowing the blood vessels to the lungs to become constricted. The constriction instead of the clogged sacs in the lungs causes the lack of oxygen. Levitt says, “One theory is that the virus affects the vascular biology and that’s why we see these really low oxygen levels.”
This theory explains why patients with high blood pressure and diabetes are at higher risk since their blood vessels are already damaged. The CDC produced data that in 14 states, over half of hospitalized patients had high blood pressure, and a third had lung disease or diabetes.
“It’s very striking to us that risk factors seem to be vascular: diabetes, obesity, age, hypertension,” says Mangalmurti. She expected there to be more patients with preexisting respiratory diseases such as asthma.
The damage to the heart and blood vessels is still perplexing to scientists. This could be because they both contain large amounts of ACE2 receptors. Another thought is that the damage is from the lack of oxygen and the overall state of the lungs during the infection, while an additional theory is that the cytokine storm might be inflicting damage to the heart in the same way as the lungs.
Krumholz says, “We’re still at the beginning. We really don’t understand who is vulnerable, why some people are affected so severely, why it comes on so rapidly … and why it is so hard [for some] to recover.”
3. Kidney Damage
The world has been worried about potential shortages of ventilators due to the prevalence of lung failure. However, we should be worried about the lack of enough machines for dialysis. The kidneys are rich in ACE2 receptors, making them a target for the virus. Neurologist Jennifer Frontera has reported from her experience treating coronavirus patients that “if these folks are not dying of lung failure, they’re dying of renal failure.” In order to support all the patients, her hospital is developing different machines for dialysis.
“The lung is the primary battle zone. But a fraction of the virus possibly attacks the kidney. And as on the real battlefield, if two places are being attacked at the same time, each place gets worse,” says neuroscientist Hongbo Jia.Related: 12 Steps to Maintaining Kidney Health