Triggering Myocardial Infarction by Marijuana
http://circ.ahajournals.org/content/103/23/2805.long
Copyright © 2001 by American Heart Association
(Unlike the April 2014 report, this was based on interviews with heart attack survivors. There was no investigation into the drug habits of those who died.)
"Marijuana use in the age group prone to coronary artery disease is higher than it was in the past."
This 2001 report points out that marijuana "has several well-described effects on the cardiovascular system."
1. Dose dependent increase in the resting heart rate of 20% to 100%
2. Increase in blood pressure, especially when lying on one's back
3. Dizzy spells when changing positions
4. Carbon Monoxide (carboxyhemoglobin) forms in red blood cells decreasing their oxygen-carrying capacity. This causes the heart to demand more oxygen, resulting in an increase in chest pain (angina).
"Thus, taken together, smoking marijuana is associated with an increase in myocardial oxygen demand and a concomitant decrease in oxygen supply." - In other words, your heart is caught in a "Catch-22."
As was stated, the greatest risk is to adults who are on their way to developing heart disease.
What I didn't know before was that besides the brain, we also have marijuana receptors in the cells of the immune system, spleen, blood vessels, and the heart.
"Furthermore, there are several reports of myocardial infarction occurring in close proximity to marijuana use in otherwise low-risk individuals."
"Of the 124 patients who reported smoking marijuana, 37 reported smoking it within 24 hours of myocardial infarction onset and 9 reported use within 1 hour of myocardial infarction symptom onset. In addition to these 9 patients, 3 patients reported using marijuana between 60 and 120 minutes before the onset of symptoms. Of the 37 patients who reported smoking marijuana within 24 hours of myocardial infarction symptoms, only 5 reported smoking it once per month or less, and 28 (76%) reported smoking it at least weekly. Similarly, 7 of the 9 patients (78%) who reported smoking marijuana within 1 hour of symptom onset reported smoking it at least once per week."
"The risk of myocardial infarction onset was elevated almost 5-fold in the hour after smoking marijuana ..."
"Aronow and Cassidy demonstrated that among patients with chronic stable angina, the anginal threshold is acutely diminished after smoking a single marijuana cigarette."
“An Institute of Medicine report on marijuana and medicine released in 1999 noted that although the cardiovascular effects of marijuana do not seem to pose a health problem for healthy young users, they may present a serious problem for older subjects. The report also noted that any effect of marijuana use on cardiovascular disease could have a substantial impact on public health.”
Copyright © 2001 by American Heart Association
(Unlike the April 2014 report, this was based on interviews with heart attack survivors. There was no investigation into the drug habits of those who died.)
"Marijuana use in the age group prone to coronary artery disease is higher than it was in the past."
This 2001 report points out that marijuana "has several well-described effects on the cardiovascular system."
1. Dose dependent increase in the resting heart rate of 20% to 100%
2. Increase in blood pressure, especially when lying on one's back
3. Dizzy spells when changing positions
4. Carbon Monoxide (carboxyhemoglobin) forms in red blood cells decreasing their oxygen-carrying capacity. This causes the heart to demand more oxygen, resulting in an increase in chest pain (angina).
"Thus, taken together, smoking marijuana is associated with an increase in myocardial oxygen demand and a concomitant decrease in oxygen supply." - In other words, your heart is caught in a "Catch-22."
As was stated, the greatest risk is to adults who are on their way to developing heart disease.
What I didn't know before was that besides the brain, we also have marijuana receptors in the cells of the immune system, spleen, blood vessels, and the heart.
"Furthermore, there are several reports of myocardial infarction occurring in close proximity to marijuana use in otherwise low-risk individuals."
"Of the 124 patients who reported smoking marijuana, 37 reported smoking it within 24 hours of myocardial infarction onset and 9 reported use within 1 hour of myocardial infarction symptom onset. In addition to these 9 patients, 3 patients reported using marijuana between 60 and 120 minutes before the onset of symptoms. Of the 37 patients who reported smoking marijuana within 24 hours of myocardial infarction symptoms, only 5 reported smoking it once per month or less, and 28 (76%) reported smoking it at least weekly. Similarly, 7 of the 9 patients (78%) who reported smoking marijuana within 1 hour of symptom onset reported smoking it at least once per week."
"The risk of myocardial infarction onset was elevated almost 5-fold in the hour after smoking marijuana ..."
"Aronow and Cassidy demonstrated that among patients with chronic stable angina, the anginal threshold is acutely diminished after smoking a single marijuana cigarette."
“An Institute of Medicine report on marijuana and medicine released in 1999 noted that although the cardiovascular effects of marijuana do not seem to pose a health problem for healthy young users, they may present a serious problem for older subjects. The report also noted that any effect of marijuana use on cardiovascular disease could have a substantial impact on public health.”
- ORIGINAL REPORT
- Clinical Investigation and Reports
- Murray A. Mittleman, MD, DrPH;
- Rebecca A. Lewis;
- Malcolm Maclure, ScD;
- Jane B. Sherwood, RN;
- James E. Muller, MD
- From the Institute for the Prevention of Cardiovascular Disease, Cardiovascular Division, Department of Medicine, Beth Israel Deaconess Medical Center, Harvard Medical School (M.A.M., R.A.L.); the Department of Epidemiology (M.A.M., M.M.) and the Department of Health and Social Behavior (J.B.S.), Harvard School of Public Health; and the Division of Cardiology, Department of Medicine, Massachusetts General Hospital, Harvard Medical School (J.E.M.), Boston, Mass.
- Correspondence to Murray A. Mittleman, MD, DrPH, Cardiovascular Division, Beth Israel Deaconess Medical Center, 1 Autumn Street, Fifth Floor, Boston, MA 02215. E-mail[email protected]
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AbstractBackground—Marijuana use in the age group prone to coronary artery disease is higher than it was in the past. Smoking marijuana is known to have hemodynamic consequences, including a dose-dependent increase in heart rate, supine hypertension, and postural hypotension; however, whether it can trigger the onset of myocardial infarction is unknown.
Methods and Results—In the Determinants of Myocardial Infarction Onset Study, we interviewed 3882 patients (1258 women) with acute myocardial infarction an average of 4 days after infarction onset. We used the case-crossover study design to compare the reported use of marijuana in the hour preceding symptoms of myocardial infarction onset to its expected frequency using self-matched control data. Of the 3882 patients, 124 (3.2%) reported smoking marijuana in the prior year, 37 within 24 hours and 9 within 1 hour of myocardial infarction symptoms. Compared with nonusers, marijuana users were more likely to be men (94% versus 67%, P<0.001), current cigarette smokers (68% versus 32%, P<0.001), and obese (43% versus 32%, P=0.008). They were less likely to have a history of angina (12% versus 25%, P<0.001) or hypertension (30% versus 44%,P=0.002). The risk of myocardial infarction onset was elevated 4.8 times over baseline (95% confidence interval, 2.4 to 9.5) in the 60 minutes after marijuana use. The elevated risk rapidly decreased thereafter.
Conclusions—Smoking marijuana is a rare trigger of acute myocardial infarction. Understanding the mechanism through which marijuana causes infarction may provide insight into the triggering of myocardial infarction by this and other, more common stressors.
Key Words:Marijuana is the most widely used illicit drug in the United States. In 1998, >72 million Americans, accounting for 33% of the population older than 12 years, had used marijuana or hashish at least once in their lifetime, with 8.6% reporting using the drug in the past year and 5.0% reporting use in the past month.1 Self-reported use of marijuana is greatest among adults between 18 and 25 years of age.1 Historically, the prevalence of smoking marijuana was very low among older adults. However, as the generation born in the 20 years after the end of the Second World War ages, the prevalence of marijuana use in the age group prone to coronary artery disease has increased.
Marijuana has several well-described effects on the cardiovascular system. For example, smoking marijuana is associated with a dose-dependent increase in the resting heart rate of 20% to 100%.2 3 4 5 6 7 8 9 10 Blood pressure is typically increased in the supine position,3 6 7 9 and postural hypotension, which is often symptomatic, is common. Overall, there is a net increase in myocardial oxygen demand with a decrease in oxygen supply, which is due in part to an increase in carboxyhemoglobin3 ; this results in a lower anginal threshold in patients with chronic stable angina.3 11 Furthermore, there are several reports of myocardial infarction occurring in close proximity to marijuana use in otherwise low-risk individuals.12 13 14
An Institute of Medicine report on marijuana and medicine released in 1999 noted that although the cardiovascular effects of marijuana do not seem to pose a health problem for healthy young users, they may present a serious problem for older subjects.15 The report also noted that any effect of marijuana use on cardiovascular disease could have a substantial impact on public health. The magnitude of the impact remains to be determined: long-term marijuana users from the late 1960s are now entering the years during which coronary arterial and cerebrovascular diseases become common. The report recommends that “studies to define the individual health risks of smoking marijuana should be conducted, particularly among populations in which marijuana use is prevalent.”15
To evaluate whether marijuana is a trigger of the onset of an acute myocardial infarction, we collected data on marijuana use in 3882 patients (1258 women) who sustained an acute myocardial infarction and were interviewed for the Determinants of Myocardial Infarction Onset Study.16 17 In this multicenter, interview-based study, we used a case-crossover study design to compare the reported use of marijuana in the hour preceding the onset of myocardial infarction symptoms to its expected frequency using self-matched control data.
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MethodsStudy PopulationBetween August 1989 and September 1996, a total of 3882 patients (2624 men and 1258 women aged 20 to 92 years) were interviewed at 64 medical centers a median of 4 days after their myocardial infarction.
Interviewers identified eligible cases by reviewing coronary care unit admission logs and patients’ charts. For inclusion in the study, patients were required to meet all of the following criteria: at least one creatine kinase level above the upper limit of normal for the clinical laboratory performing the test, positive MB isoenzymes, an identifiable onset of pain or other symptoms typical of infarction, and the ability to complete a structured interview. The institutional review board at each participating center approved the protocol, and informed consent was obtained from each patient.
Detailed chart reviews and patient interviews were conducted by research personnel trained as previously described.16 17 18 Data were collected on standard demographic variables and risk factors for coronary artery disease. The interview identified the time, place, and quality of myocardial infarction pain and other symptoms, as well as the timing and estimated usual frequency of exposure to potential triggers of myocardial infarction onset during the prior year. In addition, patients were asked if they had smoked marijuana in the year preceding their infarction. Patients who reported smoking marijuana were also asked to report the last time that they had smoked marijuana and their usual frequency of smoking marijuana over the prior year. Patients were also asked to report the timing of exposure to marijuana and other potential triggers for each of the 26 hours preceding the onset of their symptoms.
Study DesignThe design of the Onset Study has been described in detail elsewhere.16 17 18 19 20 21 In brief, we used a case-crossover study design16 19 20 22 to assess the change in the risk of acute myocardial infarction during a brief “hazard period” after exposure to marijuana and other potential triggers of myocardial infarction onset. An important feature of the case-crossover design is that control information for each patient is based on his or her own past exposure experience.16 19 20 Self-matching results in freedom from confounding by risk factors that are stable over time but often differ between study subjects.
Marijuana use in the hazard period, the 1-hour period immediately preceding the onset of myocardial infarction symptoms, was compared with its expected frequency based on control data obtained from the patients. We used the usual frequency of marijuana use over the year before myocardial infarction to estimate its expected frequency in an average 1-hour period in this patient population.
Statistical AnalysisThe analysis of case-crossover data is an application of standard methods for stratified data analysis.19 20 23 24 In this analysis, the stratifying variable is the individual patient, as in a crossover experiment. The ratio of the observed exposure frequency in the hazard period to the expected frequency (from the control information) was used to calculate estimates of the odds ratio as a measure of relative risk.16 19 20 The amount of person-time exposed to marijuana was estimated by multiplying the reported usual annual frequency of exposure by the duration of its hypothesized physiological effect (1 hour). Unexposed person-time was then calculated by subtracting the exposed person-time in hours from the number of hours in a year. The data were analyzed using methods for cohort studies with sparse data in each stratum.19 20 25
Sensitivity AnalysesTo evaluate whether exposure to other triggering behaviors could account for the observed effect of smoking marijuana, we conducted a sensitivity analysis excluding patients who smoked marijuana and engaged in other potentially triggering activities in the hour preceding their infarction.
In another sensitivity analysis, we evaluated the timing of marijuana use among the patients who reported smoking it in the 24 hours before the onset of their infarction symptoms. In this analysis, we compared the number of patients who reported smoking marijuana in the hour before symptom onset to the expected number that would arise if smoking marijuana was unrelated to myocardial infarction onset and the frequency of smoking marijuana was evenly distributed over the prior day.
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ResultsThe characteristics of the patients interviewed are presented in Table 1⇓. Of the 3882 patients with myocardial infarction who were interviewed, 124 (3.2%) reported that they had smoked marijuana in the year preceding their myocardial infarction. The frequency of smoking marijuana was significantly related to age, with 12.5% of patients younger than 50 years reporting smoking marijuana in the past year. The mean age of users was 44±8 years, compared with 62±13 years for nonusers (P<0.001). Compared with nonusers, patients who smoked marijuana were more likely to be men (94% versus 67%, P<0.001), current cigarette smokers (68% versus 32%, P<0.001), and obese (43% versus 32%,P=0.008). They were less likely to have a history of angina (12% versus 25%, P<0.001) or hypertension (30% versus 44%, P=0.002).
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Table 1.Characteristics of the Study Population
Table 2⇓ shows the distribution of the usual frequency of marijuana use among the 124 patients who reported smoking marijuana in the year before their myocardial infarction. The majority of patients who smoked marijuana reported using it at least once per month (67.7%), with 41.2% smoking marijuana at least weekly.
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Table 2.Usual Frequency of Marijuana Smoking Among 124 Patients Who Reported Using Marijuana in the Year Before Myocardial Infarction
Of the 124 patients who reported smoking marijuana, 37 reported smoking it within 24 hours of myocardial infarction onset and 9 reported use within 1 hour of myocardial infarction symptom onset. In addition to these 9 patients, 3 patients reported using marijuana between 60 and 120 minutes before the onset of symptoms. Of the 37 patients who reported smoking marijuana within 24 hours of myocardial infarction symptoms, only 5 reported smoking it once per month or less, and 28 (76%) reported smoking it at least weekly. Similarly, 7 of the 9 patients (78%) who reported smoking marijuana within 1 hour of symptom onset reported smoking it at least once per week.
On the basis of a case-crossover analysis that controlled for differences between patients, we found that within 1 hour after smoking marijuana, the risk of myocardial infarction onset was elevated 4.8-fold (95% confidence interval, 2.9 to 9.5; P<0.001) compared with periods of nonuse. In the second hour after smoking, the relative risk was 1.7 (95% confidence interval, 0.6 to 5.1; P=0.34), suggesting a rapid decline in the cardiac effects of marijuana (Figure⇓).
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