Cardiovascular Effects

A case of an abnormal heart rhythm. Is cannabis to blame?

Article title: Atrioventricular Nodal Reentrant Tachycardia Triggered by Marijuana Use: A case report and review of the literature

Summary:

The effect of cannabis on the heart is not yet well-understood. This report highlights a case of one 40-year-old patient who had, an hour after smoking cannabis, a specific type of cardiac rhythm abnormality (arrhythmia) called atrioventricular nodal reentrant tachycardia (AVNRT).  There is a physical component of this abnormality, an errant track where aberrant rhythms re-enter the heart and can cause rapid heartbeats (tachycardia.) In the discussion, the authors suggest that cannabis use, at higher doses, may stimulate the parasympathetic system, which happens to be involved in electrical current tracks in our heart. The authors further hypothesize that in susceptible people, as in this case, cannabis may affect this electrical pathway in the heart, and may disrupt a stable rhythm.

Dr Caplan and the #MDTake:

Abnormal heart rhythm disorders can be life-concerning conditions, however, there have only been 17 or so reported cases (see Table 1) of life-threatening cases in the medical literature. As it is exceedingly rare, it can be difficult to determine if cannabis is implicated or not.

Clinical Impressions:

Including rare, serious heart conditions, relatively benign circumstances, and conditions related to structural heart disease, arrhythmias are a relatively uncommon condition. Nevertheless, CED Clinic has seen many patients who have atrial fibrillation, a smaller but significant number of patients who have stable low or elevated heart rates, and a rare few with irregularly irregular abnormalities. Some patients have embraced cannabis while anticoagulated (helpful to reduce the risks of potentially dangerous clots), and some who are engaging with cannabis have been treated surgically. The approach to cannabis that most seem to prefer is a slow, gradually increasing dosage routine, where one can become accustomed to low doses, prior to advancing to something which may be more therapeutic, while minimizing the potential cardiac impact. Fortunately, to date, we have observed no grave repercussions that seemed caused, correlated or attributable to cannabis.

ECG showing AVNRT at the time of presentation.

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This paper is also stored here:    http://bit.ly/2MPc7Rl     inside the CED Foundation Archive

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Benjamin Caplan, MDA case of an abnormal heart rhythm. Is cannabis to blame?
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Does Cannabis affect blood pressure, heart rate, brain blood flow?

Article title: Acute Cardiovascular Effects of Marijuana Use

The Review:

The authors of this systematic review combed through multiple previously published studies, looking at the short-term cardiovascular effects of THC on the body. The cardiovascular effects they covered included: changes in blood pressure, heart rate, and blood flow to the brain (cerebrovascular circulation).

This review showed that for blood pressure, the results were undecided, as some studied showed a drop in blood pressure, while others did not. For heart rate, the studies showed an increase after consuming marijuana, but quantity and duration were not mentioned. As for blood flow to the brain, only one study showed a potential decrease while the others found no change. The THC percentage of the products used (mainly inhaled ones) ranged from 1.2% to 17.5%.

Dr Caplan and the #MDTake:

This limited review aims to evaluate the effects of THC on blood pressure, heart rate and blood flow to the brain, but it has important limitations. In terms of how the changes were recorded in the studies and the relevant amounts (of what is changing) were not mentioned. For instance, while the study did show that THC may increase heart rate in the short term, it is not clear what the relevance is, what risk this may poses to consumers if any. Past literature has shown that heart muscle can respond to specific cannabinoids, both in the lab and in animals trails. Several case studies have reported individuals with grave reactions, although these concerns have yet to be replicated in a controlled manner, nor correlated with any specific circumstances or components of cannabis. Toward a goal of maximizing safety, caution is likely warranted for those consuming cannabis with known cardiac risk factors (including heart dysfunction, blood pressure concerns, rhythm abnormalities, and others) particularly with regard to the consumption of high THC products.

Clinical Impressions:

Clinically, there is a distinct trend of people who have found heart rate effects with their cannabis use, mostly increased heart rates at the beginning of use (both when first beginning to consume cannabis as well as early on during an episode of consumption.) There seems to be a tolerance to the heart rate effects because many report that this effect wanes over time. There are a clear group of patients for whom cannabis lowers blood pressure, but also groups for who it either has no effect or increases blood pressure. The long-term trend again seems that tolerance plays a role in bringing all extremes to the middle ground. Regarding blood flow, there seems to be a clear increase in local blood flow with topicals and, at least among CED Clinic patients, no observable relationship between cannabis use and blood flow, from a macroscopic perspective.

View this review (yellow link) or download:

This paper is also stored here:    http://bit.ly/2MLkihz     inside the CED Foundation Archive

To explore related information, click the keywords below:

Benjamin Caplan, MDDoes Cannabis affect blood pressure, heart rate, brain blood flow?
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