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Don't Deny Cannabis Consumers Heart Transplants, Say Cardiologists

By Alexander Beadle

Published: Oct 27, 2022   
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In a new paper published in the journal Circulation: Heart Failure, cardiologists and researchers from the Indiana University School of Medicine argue that the medical establishment should work to expand its understanding and find a new approach to determining transplant candidacy for cannabis users.

This is especially important, they say, as clinician biases and a lack of consensus on how to treat cannabis-using patients with heart failure may potentially exacerbate racial, ethnic, and regional disparities in organ allocation.

Current policy for organ transplants

As the researchers highlight, the federal prohibition of cannabis is at odds with many state-level policies that allow for recreational and/or medical cannabis use. In response to the growing prevalence of cannabis, and a situation where there are now more patients on the waiting list for a transplant than there are donor hearts, some US states have passed legislation that forbids transplant centers from disqualifying transplant candidates based on medical cannabis use.

Surveys of transplant center practices analyzed in this review showed large disparities in how cannabis users were treated. One survey found that although most transplant centers supported listing medical cannabis patients to receive a transplant after a period of abstinence, significantly fewer would do the same for recreational users. Some centers even had explicit prohibitions against cannabis use in patients seeking heart, lung, liver, and pancreas transplants.

“This is a dilemma in a time of increasingly favorable legislation regarding medical and recreational cannabis use,” lead author Onyedika Ilonze, who is an assistant professor of medicine at IU School of Medicine and member of the Cardiovascular Institute, said in a statement. “The dilemma is compounded by a rising need for heart transplants.”

“Clinician bias, lack of consensus, and a dearth of research limit standard decision-making and worsen disparities in heart transplantation,” he added.

Patient outcomes seem largely unaffected by cannabis use

In this paper, the researchers reviewed several studies aiming to evaluate post-transplant outcomes in cannabis users. While post-transplant outcomes have been investigated in kidney and liver recipients, they found no similar reviews for heart transplants.

Still, these kidney and liver studies did not find clear evidence of transplanted tissue dysfunction. One study of cannabis-using kidney recipients found no significant differences in renal function, graft failure, or death rates between cannabis users and non-users at one year post-transplant. Another retrospective review of liver transplant recipients found no difference in survival rate between current and former cannabis users versus non-users.

However, a diagnosis of cannabis dependence or abuse was linked to a two-fold increase in graft failure and death in one review of kidney transplant patient data. Another found that concomitant tobacco use alongside cannabis use could reduce the risk of graft survival, though cannabis use alone did not.

One of the concerns cited by transplant centers is that smoking cannabis can be an additional risk factor for postoperative fungal infection, since cannabis flower can sometimes harbor Aspergillus mold.

As heart transplant patients typically require more aggressive immunosuppressive medications following surgery than patients undergoing other procedures, this increased risk for fungal infection may be a more serious concern for such patients. The authors suggest that heart transplant patients could be advised to avoid smoking or vaping cannabis shortly before and after the operation in order to nullify this risk.

Finally, the researchers examined whether cannabis use by potential heart donors might cause any unintended ill-effects on recipients.

Despite the scarcity of donor organs, some transplant centers are still hesitant to accept organs from cannabis-using donors due to concerns over the cardiovascular impact of cannabis. While the American Heart Association does caution that cannabis use may harm heart health, a retrospective review of extended criteria heart donors found no significant differences in survival when comparing transplant recipients who received a heart from a “high-risk” donor with a history of cannabis use, versus a low-risk donor.

Further research needed to plug widening knowledge gaps

The rapid pace of cannabis decriminalization coupled with an increasing incidence of heart failure will likely worsen the current knowledge gaps relating to cannabis use and heart transplant procedures, the Indiana University researchers say. However, it can also be an opportunity for the scientific establishment to re-evaluate its position on cannabis use and organ transplants.

The researchers highlight several key areas for future research, including the need to determine how cannabis might interact with immunosuppressant drugs, the prevalence of cannabis use disorder (CUD) among patients with heart failure, the presence of biases in physician attitudes, and the post-transplant health outcomes of both cannabis-using patients who receive a transplant and non-user who receive an organ from a cannabis-using donor.

“We need to learn more about the interactions between cannabis and immunosuppressants, and to study the association between cannabis use and transplant survival,” Ilonze said. “Clarifying this will move us forward and help us establish a standardized evaluation process.”

The field must work to ensure that the process used to determine transplant candidacy is data-driven and able to distribute organs in an equitable way. While more research is needed to properly lay the groundwork for such a method, the Indiana University researchers suggest that heart transplant selection committees may wish to consider not excluding patients from transplant listing based on cannabis usage alone. Instead, they say that patients should be screened for CUD, which may be treatable.

Additionally, selection committees may consider treating medical cannabis patients similarly to other transplant candidates who use prescription opiates; most transplant programs do consider prescription opiate use as acceptable, and cannabis is generally accepted as having a safer side effect profile than these opiates.


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