While doctors still aren't 100 per cent sure how the clot stayed completely intact on its way up the man's throat, Dr Wieselthaler suspected it was because the man had more fibrinogen in his blood.
The unidentified patient was receiving treatment in the Intensive Care Unit at the University of California San Francisco Medical Center, according to a November 29 article in the New England Journal of Medicine.
Per the Atlantic, Wieselthaler said that the use of the pump requires anticoagulants to "make the blood thinner and prevent clots from forming", though that comes with the risk of uncontrolled internal bleeding.
While that, in and of itself, is something astounding, the medical staff treating the unnamed man were astonished to find that, given his unique medical circumstances, the man had actually expectorated a perfectly intact cast of his right bronchial tree, one of the tubular networks that brings air to and from the lungs.
A 36-year-old man was admitted to the ICU with an acute exacerbation of chronic #heartfailure.
A man who went into the hospital with heart problems ended up literally coughing up a lung.
One week after extubation, he died from complications of heart failure (volume overload and poor cardiac output) despite placement of the ventricular assist device.
The 36-year-old patient had been had been coughing up tiny blot clots for days and after an extreme coughing spell, this "very, very, very rare" clot emerged. But blood is less sticky and sturdy than these other substances, meaning that a cast made of blood is less likely to hold together when coughed up, the Atlantic reported.
In 2005, a heavily pregnant woman coughed up a similar but smaller bronchial tree clot.