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EP-EDGE brings you the latest in cardiac electrophysiology — from breakthrough research and clinical insights to future-shaping innovations. Hosted by Dr. Niraj Sharma, an electrophysiologist with over 15 years of experience, each episode delivers clear, evidence-based updates designed to inform, inspire, and elevate your practice.
Hello everyone and welcome back to another episode of EP Edge Heart Talk. This is your host Doctor. Sharma, cardiac electrophysiologist. As we enter the holiday season with Christmas lights up, family gatherings underway, and the end of the year approaching, I want to take a moment to thank all of you: colleagues, clinicians, trainees, researchers and patients who follow the EP EDGE platform. Your engagement and enthusiasm are what make this work meaningful.
Niraj Sharma:Today, we are bringing you a very special December mega issue. It's one of the most important and timely topics of 2025. The big marijuana issue, cannabis, cardiovascular risk, and electrophysiology clearing the haze. Cannabis use is expanding rapidly in The United States, in Canada, across Europe, and increasingly worldwide. At the same time, THC potency has risen to levels unimaginable twenty or thirty years ago.
Niraj Sharma:As clinicians, we are now seeing the cardiovascular and electrophysiologic consequences in real time. In this episode, we will walk through the science, the mechanisms, the clinical data, and the electrophysiology implications. And we will talk about what all of this means for patient care in 2025 and beyond. With that, let's begin our deep dive into the cardiovascular impact of modern, high potency cannabis. Let's start with the mechanistic foundations: how cannabinoids affect the heart and vasculature.
Niraj Sharma:Cannabinoids exert cardiovascular effects primarily through two receptors: CB1 and CB2. These receptors are distributed across the myocardium, coronary vessels, autonomic nervous system, platelets, and immune cells. HypotCTHC is a strong agonist at the CB1 receptor. CB1 receptors are found in myocardial tissue, in coronary endothelium, in sympathetic nerve terminals, and in vascular smooth muscle. When THC activates CB1, several harmful downstream effects follow.
Niraj Sharma:First, autonomic activation. We see tachycardia, elevations in blood pressure, and increased myocardial oxygen demand. THC can produce a swinging pattern of sympathetic and parasympathetic tone, setting up oscillations that can trigger atrial fibrillation and other arrhythmias. Second, endothelial dysfunction. THC reduces nitric oxide bioavailability, increases reactive oxygen species, and activates inflammatory pathways such as MAP kinase and ERK.
Niraj Sharma:These changes promote endothelial apoptosis and set the stage for premature atherosclerosis. Third, coronary microvascular dysfunction. CB1 activation can provoke vasoconstriction and frank vasospasm, leading to the classic picture of myocardial infarction with angiographically normal epicardial coronaries. Fourth, a prothrombotic state. THC enhances platelet activation, including thromboxane A2 signaling and aggregation.
Niraj Sharma:The result is an increased tendency toward microthrombosis and vascular occlusion. CB2 receptors, by contrast, are expressed mainly on immune cells. They can exert anti inflammatory effects but in practice CB2 activity does not meaningfully counterbalance the dominant CB1 mediated cardiovascular stress produced by modern high THC products. Importantly for EP practice, THC also produces a biphasic autonomic response. Phase I: A sympathetic surge, heart rate and blood pressure go up and catecholamines rise.
Niraj Sharma:Phase II: A parasympathetic rebound. Blood pressure can fall and bradyarrhythmias or vaguely mediated atrial fibrillation may be triggered. At the cellular level, THC promotes mitochondrial dysfunction in cardiomyocytes, lowers ATP reserves, and increases oxidative stress. This combination creates an arrhythmogenic substrate that is especially problematic in the presence of other insults, such as ischemia, scar, or structural heart disease. Now that we have talked about the basic mechanisms, let's step back and answer a very practical question.
Niraj Sharma:When we say cannabis, what exactly are we talking about? Not all cannabis products are created equal. The cardiovascular and electrophysiologic effects depend heavily on the type of product, the THC potency, the route of use, and the dose. The cannabis of the 1970s at 2% to 4% THC is very different from the modern dispensary products of 2025, which often contain 20% to 30% THC in flour and 70% to 90% THC in concentrates and vape oils. Let's start with the main actor, THC.
Niraj Sharma:THC is a potent partial agonist at the CB1 receptor. It's highly lipophilic, crosses rapidly into the brain, and in the heart and vasculature it drives sympathetic activation, endothelial dysfunction, platelet activation, and changes in calcium handling that can set up arrhythmias. Higher THC levels mean stronger CB1 activation, more catecholamine surge, more endothelial injury, and greater electrophysiologic instability. In other words, the higher the THC dose and the faster it gets into the system, the higher the arrhythmia risk. Other cannabinoids matter too.
Niraj Sharma:CBD is not a major arrhythmia trigger on its own, but it does inhibit liver enzymes like CYP3, A four, and 2D6, and the P glycoprotein transporter. That means CBD can raise blood levels of direct oral anticoagulants, amiodarone, sotalol, flecainide, and even beta blockers, all drugs we use every day in electrophysiology. So even so called CBD only products can interact with medications especially if they are mislabeled and contain more THC than advertised. At the other end of the spectrum are synthetic cannabinoids like K2 and Spice. These are full CB1 agonists, often 10 to 100 times more potent than THC, with no CBD or other plant compounds to buffer the effect.
Niraj Sharma:They have been repeatedly linked to myocardial infarction, ventricular fibrillation, stroke, seizures, and sudden death. From a cardiac standpoint, they are better thought of as cardiotoxic agents than as recreational drugs. Now let's talk about routes and products because route of administration strongly shapes the electrophysiologic risk. Smoked flower with 10% to 25% THC delivers THC to the bloodstream within seconds to minutes. Peak levels are reached quickly, producing a brisk sympathetic surge, a rise in heart rate and blood pressure, and a rapid increase in packs, PVCs, and susceptibility to atrial fibrillation or SVT.
Niraj Sharma:Vaped oils and distillates, often 60 to 85% THC, are even more concerning. They deliver very high THC doses in small volumes with excellent bioavailability. Compared with smoking, vaped THC produces higher peak levels, more abrupt autonomic shifts, and in large EHR data sets has been associated with markedly higher rates of atrial fibrillation and more than a threefold increase in ventricular tachycardia and fibrillation. Concentrates such as DABs, wax, shatter, and resin at seventy-ninety 5% THC sit near the top of the risk ladder. Here we are delivering massive THC boluses in a single inhalation.
Niraj Sharma:The result can be a sudden intense CB1 stimulus, a huge catecholamine release, coronary vasospasm, and a setup for polymorphic VT or VF in susceptible patients. Edibles are a different animal. Instead of a rapid spike, edibles create a delayed and prolonged exposure. Peak levels often occur one to three hours after ingestion, and the psychoactive metabolite eleven hydroxy THC can be even more potent than THC itself. Clinically, that means a long window of autonomic instability with sympathetic and parasympathetic swings that can trigger vaguely mediated atrial fibrillation, exacerbate PVCs, and worsen endothelial dysfunction.
Niraj Sharma:Many patients who took one gummy actually consumed one hundred or more milligrams of THC without realizing it. Topical products such as creams and lotions generally have minimal systemic absorption and negligible electrophysiologic risk unless they are combined with smoked or ingested THC. So when do adverse cardiac and electrophysiologic effects tend to occur? At low doses (two-five mg THC), most healthy users will experience mild tachycardia and small hemodynamic shifts. At ten-twenty mg, especially in edibles or repeated inhalations, we begin to see clinically relevant changes: bigger heart rate and blood pressure swings and occasional atrial fibrillation or SVT in predisposed individuals.
Niraj Sharma:Between twenty and fifty milligrams or with repeated hits of high potency vapes or concentrates, autonomic instability becomes more pronounced, PVC burden increases, and the risk of atrial and ventricular arrhythmias rises sharply. Above fifty-one hundred mg or even very high potency concentrates, we enter the zone where myocardial infarction from vasospasm, sustained arrhythmias, and even ventricular tachycardia or ventricular fibrillation become realistic possibilities, especially in those with underlying structural disease or scar. The highest risk is seen in younger adults, daily or near daily users, high potency vape and dab users, patients with congenital or acquired substrate such as HCM, scar, or long QT, and those who combine cannabis with stimulants like cocaine or amphetamines. From an electrophysiologist's perspective, the key takeaway is this: We should not ask only Do you use cannabis? Instead, we should ask What type?
Niraj Sharma:What potency? Smoked, vaped, dabbed, or edible? How many milligrams per session and how many days per week? Cannabis is best thought of as a dose dependent cardiovascular drug, not a single uniform recreational substance. Root and potency directly determine its arrhythmia risk.
Niraj Sharma:With the mechanisms in mind, let's move to clinical outcomes: myocardial infarction and stroke. The most important study in this space is the TriNetX multicenter cohort published in JACC Advances in 2025. This large, real world, multicenter analysis included 4,600,000 adults between 18 and 50 years of age across 53 health systems. Crucially, the investigators excluded patients with traditional cardiovascular risk factors: hypertension, diabetes, dyslipidemia, tobacco use, established coronary artery disease, prior myocardial infarction or stroke, and significant renal disease. What remained was a cohort of metabolically healthy young adults.
Niraj Sharma:Within this population, cannabis users had more than a six fold increase in myocardial infarction risk compared with matched non users. That effect size is on par with familial hypercholesterolemia, cocaine use, or severe uncontrolled hypertension. Ischemic stroke risk increased by about fourfold, particularly within forty eight hours of documented cannabis exposure. Events clustered within one to twenty four hours of use, a pattern highly consistent with THC driven vasospasm, autonomic surges, microvascular ischemia, endothelial dysfunction, and transient hypercoagulability. The composite of major adverse cardiovascular events, myocardial infarction, stroke, and cardiovascular death, was approximately three times higher in cannabis users.
Niraj Sharma:Heart failure risk doubled, and all cause mortality increased by roughly fifty percent, even after tobacco users were excluded. Despite limitations such as coded rather than biochemical exposure and limited potency data, any misclassification would be expected to bias results toward the null. In other words, the true risk may be even higher. From an EP edge perspective, TriNetX is a defining paper. It demonstrates that cannabis is not benign, especially in young adults, and that high potency THC products materially increase the risk of premature myocardial infarction and stroke.
Niraj Sharma:A complementary international meta analysis pooling about 75,000,000 individuals from 12 population level studies provides further support. Across North America, Europe, Australia, and Asia, cannabis use was associated with a twenty nine to fifty percent increase in myocardial infarction risk and about a twenty percent increase in ischemic stroke risk. In some cohorts, cardiovascular mortality was up to two times higher, particularly in high frequency, high potency users. A clear dose response emerged. Daily or near daily use conferred the highest risk, while occasional use still carried a measurable, although smaller signal.
Niraj Sharma:Risk was consistently higher in adults 50 and in markets with legalized, high potency recreational cannabis. Smoked and vaped roots showed the strongest associations, though high dose edibles also contributed. Polysubstance use cocaine, amphetamines, alcohol, and tobacco amplified risk substantially. A systematic review in the journal Heart published in 2025 synthesized observational data on myocardial infarction, stroke, and cardiovascular mortality. Across multiple cohort and case control studies, acute coronary syndrome and myocardial infarction risk increased by about twenty nine percent, stroke risk by about twenty percent, and cardiovascular mortality by more than twofold.
Niraj Sharma:Again, the strongest signals appeared in younger adults, in high potency environments, and in heavy daily users. Studies repeatedly showed clustering of events within one to two hours after cannabis consumption, reinforcing a temporal trigger relationship. Not every dataset shows an increased risk. A Veterans Affairs cohort of older adults with established coronary disease reported no significant association between cannabis use and major adverse cardiovascular events. However, this neutral signal must be interpreted carefully.
Niraj Sharma:Older veterans often used lower potency, legacy cannabis, and typically consumed it intermittently, often for chronic pain. They also carried a heavy burden of competing risks: hypertension, diabetes, decades of tobacco exposure, and known coronary disease, which can mask incremental THC effects. Many of these older users also represent a kind of healthy survivor cohort. Those who were highly susceptible may have stopped using cannabis years earlier. Exposure was self reported rather than biochemically confirmed, with poor characterization of dose, root, and potency.
Niraj Sharma:Perhaps most importantly, 1970s or 1980s cannabis at two-seven percent THC is biologically very different from twenty twenty five products containing twenty-ninety percent THC. Taken together, the VA cohort reflects low potency, low frequency older use patterns. Modern cannabis risk is driven by age times potency times frequency. The neutral older veteran data do not contradict the robust MI and stroke signals seen in younger, high potency users. Next, let's zoom in on the vascular level: endothelial dysfunction.
Niraj Sharma:The CANDIDE trial, published in JAMA Cardiology in 2025, studied 55 healthy adults with no tobacco or vaping exposure. Participants were divided into three groups: non users, smoked cannabis users, and edible cannabis users. Flow mediated dilation, a marker of endothelial function, was approximately ten point four percent in non users, about six percent in smokers, and only four point six percent in edible users. In other words, chronic cannabis use was associated with substantially impaired endothelial function, with the worst impairments seen in frequent edible users. The study also showed a clear dose response relationship, with more frequent THC exposure associated with the worse endothelial performance.
Niraj Sharma:Measures of nitric oxide bioavailability were reduced in cannabis users, consistent with the mechanistic data we discussed earlier. Complementary work from Stanford examined THC in cellular, animal, and population models. In human endothelial cells, THC exposure increased inflammatory signaling and markers of vascular injury. In hyperlipidemic mice, daily THC accelerated atherosclerosis, and in large observational cohorts such as the UK Biobank, monthly or more frequent cannabis use was associated with increased risk of premature myocardial infarction. Taken together, these studies show that cannabis is not only an acute hemodynamic stressor but also a chronic vascular toxin, promoting endothelial dysfunction and early atherosclerosis.
Niraj Sharma:Atrial flutter, atrial tachycardia, and supraventricular tachycardia are consistently more common in cannabis users. Premature atrial and ventricular beats are about seventy five percent more frequent and ventricular tachycardia and fibrillation risk can increase threefold or more. The arrhythmic burden is higher in younger adults, in high potency legal markets, in daily or near daily users, and in those who combine cannabis with stimulants or alcohol. Mechanistically, these clinical findings align with THC driven sympathetic surges, parasympathetic rebound, microvascular ischemia, endothelial dysfunction, platelet activation, and direct myocyte stress. From an EP clinical perspective, cannabis functions both as a trigger and as a substrate amplifier that can worsen long term arrhythmia burden, particularly atrial fibrillation and ventriculolectomy.
Niraj Sharma:Before we close, let's briefly touch on an intriguing area of research: genistein and peripheral CB1 blockade. Investigators at Stanford have studied genestine, a soy derived compound as a peripheral CB1 antagonist. In preclinical models, genestine appears to block THC induced endothelial inflammation and slow atherosclerotic progression without crossing the blood brain barrier. In theory, this could attenuate vascular harm while preserving central psychoactive effects. But at this stage all data remain preclinical: No human trials, no standardized dosing, and no clinical recommendations.
Niraj Sharma:So where does this leave us? Modern high THC cannabis is not the mild substance of the past. The totality of evidence now shows measurable cardiovascular and electrophysiologic consequences: increased risk of myocardial infarction, increased risk of stroke, endothelial dysfunction, more atrial fibrillation and supraventricular tachycardia, increased ectopy, and elevated risk of ventricular tachycardia and ventricular fibrillation. For the EP community, the arrhythmia data are striking. Cannabis has become a true atrial fibrillation risk factor in multiple contemporary data sets.
Niraj Sharma:SVT and ectopy rise significantly. VT and VF risk climbs, especially in high potency users or in the presence of scar or ischemia. Young adults show the strongest risk signal, a theme we are now seeing repeatedly in clinics and in the electrophysiology lab. Clinically, cannabis must now be treated as a modifiable arrhythmia and vascular risk factor. Ask every AFib, SVT, PVC, or VT patient about cannabis use: potency, route, and frequency.
Niraj Sharma:Counsel appropriately, especially in younger patients, and integrate cannabis into your routine risk factor discussion. If you would like to review all references, figures, and infographics from this episode, you can find them in the EP Edge LinkedIn newsletter December issue, The Big Marijuana Issue. If you have any questions or concerns or would like to suggest future topics please email me at epedgecast@gmail . com. This is Doctor. Sharma and this has been EP Edge.
Niraj Sharma:Thank you for listening. Bye for now