Cannabis Use Is a Growing Concern in Heart Transplant

Literature review summarizes existing data to help inform international guidelines

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Legalization of cannabis for medicinal or recreational use in many countries has created controversy in the heart transplant field. Current International Society for Heart and Lung Transplantation (ISHLT) guidelines, last updated in 2016, provide no guidance about cannabis use in transplant candidates. As a result, policies are varied across centers, sometimes to the detriment of transplant recipients.

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“Cannabis use in heart transplantation is a bigger concern than some providers realize,” says Eileen Hsich, MD, Medical Director of the Heart Transplant Program at Cleveland Clinic. “Data on the topic were limited in 2016. Today we have more data, as cannabis use among transplant patients has become more common.”

International heart transplant guidelines are due for an update, she notes. In preparation, Dr. Hsich and colleagues summarized existing data on cannabis and transplantation, including research on graft failure and death, infection, cancer and cardiovascular complications. The review was recently published in The Journal of Heart and Lung Transplantation.

“We hope this paper will help steer discussion and serve as a resource for the ISHLT as it considers updating transplant guidelines,” says Dr. Hsich. “There are very few articles published on cannabis use and the heart, and ours is the only one that focuses on heart transplantation.”

“We also hope this review highlights the need for future research to further understanding of the impact of cannabis use in heart transplantation,” adds co-author Caroline Olt, MD, an internal medicine resident at Cleveland Clinic.

Prevalence of cannabis use

Asking heart transplant candidates about use of cigarettes, nicotine products, alcohol and illicit drugs is uniform across U.S. transplant centers, says Dr. Hsich. But asking about cannabis use isn’t. In fact, laws in some states prevent centers from declining transplant candidates due to cannabis use. As a result, some providers don’t view cannabis use as a heart transplant concern.

Moreover, urine toxicology screens are not reliable screening tools, Dr. Hsich notes. “When patients abstain from use before screening, cannabis isn’t always detected in urine toxicology,” she says. “Patients may claim they don’t use it, but we sometimes discover after transplant that the use is more frequent than originally admitted.”

Prevalence appears to be growing, at least anecdotally, she adds. Legalization of cannabis in many states has made products readily available online and at retail outlets including pharmacies and hair salons.

Legal but detrimental

According to the review article, chronic cannabis use is problematic in heart transplantation, mostly because it interferes with immunosuppression.

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Cannabis compounds like cannabidiol (CBD) and Δ9-tetrahydrocannabinol (THC) interact with enzymes that may affect the potency of immunosuppressive medications like tacrolimus. The challenge of maintaining therapeutic immunotherapy levels is further complicated by inaccurate concentrations of CBD and THC in cannabis products due to lack of regulatory standards.

In addition, chronic cannabis use can cause cannabinoid hyperemesis syndrome, which leads to reduced absorption of immunosuppressants.

“Some patients use cannabis for medicinal purposes, such as to decrease anxiety or pain,” says Dr. Hsich. “We tell them anxiety and pain may intensify after transplantation — but there are safer and more effective ways to address them than using cannabis.”

Key takeaways for heart specialists

Other key takeaways from the literature review include:

  • Route of administration, frequency of use and dependency need to be addressed in future transplant guidelines. Inhaling cannabis, which generates carcinogens like smoking tobacco, tends to be more harmful than consuming cannabis through edible and topical products. Also, frequency of use and addiction are more important in determining transplant candidacy than is purpose of use (recreational versus medicinal).
  • Casual cannabis use should be distinguished from cannabis use disorder. Infrequent, casual use may have minimal effect on transplant outcomes. However, cannabis use disorder —use for at least a year with history of intoxication, withdrawal, cravings, risky behavior, social impairment and addiction — is associated with noncompliance, graft failure and death among transplant recipients. That conclusion is based on a large analysis of outcomes data in kidney transplant patients, who receive immunosuppressive regimens similar to those for heart transplantation.

“Cannabis may be less addictive than substances like heroin and cocaine, but addiction is still possible and should be viewed like any other addiction,” says Dr. Hsich. “Cannabis use disorder shares the same destructive properties.”

According to ISHLT 2016 guidelines, substance abuse is a contraindication to transplantation. Cannabis use disorder should be considered likewise, says Dr. Hsich, noting that not all providers concur. “I am surprised by the controversy surrounding cannabis,” she says. “Our field more readily accepts avoidance of grapefruit juice since it interferes with many transplant drugs.”

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Following Canada’s lead

In 2020, the Canadian Cardiovascular Society/Canadian Cardiac Transplant Network addressed cannabis in a position statement of its own. Despite Canada’s nationwide legalization of cannabis, the statement recommended that patients abstain from smoking, inhaling or vaping it for six months before being listed for heart transplantation. The statement also recommended that patients with cannabis use disorder complete a treatment program with a minimum of six months of abstinence before being listed.

“Based on the data available for cannabis and transplantation, we support the Canadian statement and hope that ISHLT adopts similar guidelines,” says Dr. Hsich.

Meanwhile, all transplant programs can offer treatment consistent with the spirit of the Canadian statement, notes her colleague Edward Soltesz, MD, MPH, a heart transplant surgeon and Surgical Director of the Kaufman Center for Heart Failure Treatment and Recovery. “At Cleveland Clinic, we have established a comprehensive team of multidisciplinary providers to help treat substance use disorders in our patients with heart failure undergoing advanced therapies,” says Dr. Soltesz. “Addiction specialists, social workers and psychiatric providers all collaborate during heart transplant eligibility assessment as well as after listing and transplant to enhance the motivation toward abstinence.”

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