Pubdate: Tue, 27 Oct 2020
Source: New York Times (NY)
Copyright: 2020 The New York Times Company
Author: Jane E. Brody


Do you have the heart to safely smoke pot? Maybe not, a growing body
of medical reports suggests.

Currently, increased smoking of marijuana in public, even in cities
like New York where recreational use remains illegal (though no longer
prosecuted), has reinforced a popular belief that this practice is
safe, even health-promoting.

"Many people think that they have a free pass to smoke marijuana," Dr.
Salomeh Keyhani, professor of medicine at the University of
California, San Francisco, told me. "I even heard a suggestion on
public radio that tobacco companies should switch to marijuana because
then they'd be selling life instead of selling death."

But if you already are a regular user of recreational marijuana or
about to become one, it would be wise to consider medical evidence
that contradicts this view, especially for people with underlying
cardiovascular diseases.

Compared with tobacco, marijuana smoking causes a fivefold greater
impairment of the blood's oxygen-carrying capacity, Dr. Keyhani and
colleagues reported.

In a review of medical evidence, published in January in the Journal
of the American College of Cardiology, researchers described a broad
range of risks to the heart and blood vessels associated with the use
of marijuana.

The authors, led by Dr. Muthiah Vaduganathan, cardiologist at Brigham
and Women's Hospital in Boston, point out that "marijuana is becoming
increasingly potent, and smoking marijuana carries many of the same
cardiovascular health hazards as smoking tobacco."

Edible forms of marijuana have also been implicated as a possible
cause of a heart attack, especially when high doses of the active
ingredient THC are consumed.

With regard to smoking marijuana, Dr. Vaduganathan explained in an
interview, "The combustion products a tobacco smoker inhales have a
very similar toxin profile to marijuana, so the potential lung and
heart effects can be comparable. When dealing with patients, we really
have to shift our approach to the use of marijuana."

His team reported, "Although marijuana is smoked with fewer puffs,
larger puff volumes and longer breath holds may yield greater delivery
of inhaled elements." In other words, when compared to tobacco
smoking, exposure to chemicals damaging to the heart and lungs may be
even greater from smoking marijuana.

Dr. Vaduganathan said he was especially concerned about the increasing
number of heart attacks among marijuana users younger than 50. In a
registry of cases created by his colleagues, in young patients
suffering a first heart attack, "marijuana smoking was identified as
one factor that was more common among them." The registry revealed
that, even when tobacco use was taken into account, marijuana use was
associated with twice the hazard of death among those under age 50 who
suffered their first heart attack.

Other medical reports have suggested possible reasons. A research team
headed by Dr. Carl J. Lavie of the John Ochsner Heart and Vascular
Institute in New Orleans, writing in the journal Missouri Medicine,
cited case reports of inflammation and clots in the arteries and
spasms of the coronary arteries in young adults who smoke marijuana.

Another damaging effect that has been linked to marijuana is
disruption of the heart's electrical system, causing abnormal heart
rhythms like atrial fibrillation that can result in a stroke. In one
survey of marijuana smokers, the risk of stroke was increased more
than threefold.

These various findings suggest that a person need not have underlying
coronary artery disease to experience cardiovascular dysfunction
resulting from the use of marijuana. There are receptors for
cannabinoids, the active ingredients in marijuana, on heart muscle
cells and blood platelets that are involved in precipitating heart

Cannabinoids can also interfere with the beneficial effects of various
cardiovascular medications, including statins, warfarin,
antiarrhythmia drugs, beta-blockers and calcium-channel blockers, the
Boston team noted.

The researchers found that in an analysis of 36 studies among people
who suffered heart attacks, the top three triggers were use of
cocaine, eating a heavy meal and smoking marijuana. And 28 of 33
systematically analyzed studies linked marijuana use to an increased
risk of what are called acute coronary syndromes - a reduction of
blood flow to the heart that can cause crushing chest pain, shortness
of breath or a heart attack.

"In settings of an increased demand on the heart, marijuana use may be
the straw on the back, the extra load that triggers a heart attack,"
Dr. Vaduganathan said. He suggested that the recent decline in
cardiovascular health and life expectancy among Americans may be
related in part to the increased use of marijuana by young adults.

"We should be screening and testing for marijuana use, especially in
young patients with symptoms of cardiovascular disease," Dr.
Vaduganathan urged.

He expressed special concern about two recent practices: the vaping of
marijuana and the use of more potent forms of the drug, including
synthetic marijuana products.

"Vaping delivers the chemicals in marijuana smoke more effectively,
resulting in increased doses to the heart and potentially adverse
effects that are more pronounced," the cardiologist said. "Marijuana
stimulates a sympathetic nervous system response - an increase in
blood pressure, heart rate and demands on the heart that can be
especially hazardous in people with preexisting heart disease or who
are at risk of developing it."

Dr. Vaduganathan's team estimated that more than two million American
adults who say they have used marijuana also have established
cardiovascular disease, according to data from the National Health and
Nutrition Examination Surveys in 2015 and 2016.

According to Dr. Keyhani, who works at the San Francisco VA Medical
Center, the combination of marijuana smoking and pre-existing heart
disease is especially concerning because inhaling particulate matter
of any kind can harm the heart and blood vessels.

"Marijuana is a leafy green, and combustion of any plant is probably
toxic to human health if the resulting products are inhaled," she
explained. "Unfortunately, the research base is inadequate because
marijuana hasn't been studied in randomized clinical trials."

A major problem in attempts to clarify the risks of marijuana is its
classification by the U.S. Drug Enforcement Administration as a
Schedule I drug, making it illegal to study it rigorously in
controlled clinical trials.

Scientists must then resort to the next best research method:
prospective cohort studies in which large groups of people with known
habits and risk factors are followed for long periods to assess their
health status. "The challenge is to recruit a cohort of daily cannabis
users," Dr. Keyhani said. "It's absolutely important to look at the
health effects of cannabis now that the prevalence of daily use is
increasing. The absence of evidence is not evidence of absence."

While there are currently no official guidelines, Dr. Vaduganathan's
team urged that anyone known to be at increased risk of cardiovascular
disease should be advised to minimize the use of marijuana or, better
yet, quit altogether.
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