Letter by Čulić Regarding Article, “Physical Activity and Anger or Emotional Upset as Triggers of Acute Myocardial Infarction: The INTERHEART Study”
To the Editor:
A recent analysis of data from the INTERHEART study1 confirmed that physical exertion and anger or emotional upset can trigger acute myocardial infarction (AMI) and that those triggers have an additive effect when they come together. At the same time, the results confute some previous observations on effect modification by individual characteristics or cardiovascular prevention medication.1 However, 2 issues seem to be worth noting.
In the INTERHEART study, physical exertion was reported by 13.6% of participants during the case period.1 The estimated population attributable risk (ie, number of AMIs that could have been avoided if there has been no exposure to physical exertion) is 7.7% of all AMIs.1 However, in the INTERHEART study,1 mild-to-moderate physical activity, alone preceding 28.6% of AMI onsets,2 was not separately investigated as a trigger. Although heavy exertion has a more powerful acute effect, more often leading to an AMI in exposed vulnerable subjects, moderate physical activity is also an important trigger on the population level because of its frequent occurrence in everyday life. Moderate physical activity per se increases the relative risk of triggering AMI by 1.6 times and has been estimated to be responsible for −4.2% of all AMIs.3 Hence, it would be particularly interesting to investigate the possible additive effect of triggering by both moderate physical activity and anger or emotional upset.
The authors of the INTERHEART study mentioned that external triggers precipitate AMI only in the presence of biologically active vulnerable plaques.1 Another possibility is that more vulnerable coronary lesions require a less obvious external trigger to cause the plaque rupture or endothelial erosion, whereas trigger-related AMIs are associated with less vulnerable lesions requiring a more powerful biomechanical stress produced by triggering activity or event to cause AMI.4,5 Intensity of biomechanical stress correlates with intensity of cardiac work, and every heart beat induces deformation, stretching, and squeezing of coronary arteries, occasionally capable of triggering plaque rupture and AMI.4 We may additionally speculate that patients with a worse overall health condition less often perform heavy physical activities because of limitations caused by their comorbidities, whereas those individuals who look and feel healthier more easily and more often expose themselves to physical exertion regardless of the presence of cardiovascular risk factors.4 The latter hypothesis may be related to an intriguing part of the INTERHEART results regarding the risk of triggering according to baseline physical activity. Although the odds ratios were similar, the population attributable risks provided in Figure 1 of the INTERHEART study suggest that the excess risk and the number of AMIs directly attributable to physical exertion are approximately double among those regularly engaged in moderate-to-strenuous exertion (14.3%) than among mainly sedentary (6.7%) or those usually exposed to mild exertion (6.5%).1 This finding stresses the importance of physician’s caution in recommending intense physical activity to individuals with undetermined cardiovascular status. The best advice for people with suspected coronary artery disease is probably to avoid intense activities until a full cardiological diagnostic evaluation is completed.
Circulation is available at http://circ.ahajournals.org.
- © 2017 American Heart Association, Inc.