Specific Activities as Potential Triggers of Acute Myocardial Infarction

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Morning and awakening appears to trigger acute coronary syndromes. Other environmental changes, such as the transition from weekend to work week and changes in weather cycles, may also function as triggers. Many investigators have sought specific events identifiable by patients as triggers. Studies using interview techniques to determine the fraction of patients reporting a suspected "triggering activity" in the time period immediately preceding the onset of symptoms have found that 25 to >50% of patients describe moderate to heavy physical exertion, unusual emotional stress, lack of sleep, overeating or use of alcohol, noncardiac illness or surgery, or some other activity as ongoing at the time of, or in the 24 h preceding, the onset of infarction (82-85). However, these data are limited by recall bias and by the difficulty of obtaining appropriate control data, i.e., the frequency with which the activity occurs without an acute event following.

New epidemiological techniques have allowed a more sophisticated study of the relationship between specific patient activities and the onset of acute cardiac events. One such approach is the case-crossover method, which uses the patient as his or her own control to calculate the relative risk of a rare acute event such as a myocardial infarction following an intermittently performed activity suspected of being a trigger (86). This method reduces some of the bias inherent in this type of study.

Table 1

Relative Risk of Myocardial Infarction Following Triggering Events, Including the Effect of Exercise Frequency on Risk

Trigger (reference)

Duration of risk increase

Overall RR MI of triggering MI

RR of triggering MI stratified by exercise frequency

Trigger (reference)

Duration of risk increase

Overall RR MI of triggering MI

RR of triggering MI stratified by exercise frequency

Exercise (88)

1 h

5.9 (4.6-7.7)

107 (67-171)

8.6 (3.6-20.5)

Sexual intercourse (94)

2 h

2.5 (1.7-3.7)

3.0 (2.0-4.5)

1.2 (0.4-3.7)

Anger (103)

2 h

2.3 (1.7-3.2)

*

*

Morning (36)

*

1.38 (1.37-1.40)

*

*

Cocaine use (105)

1 h

23.8 (8.3-66.3)

*

*

Marijuana use (106)

1 h

4.8 (2.4-9.5)

*

*

RR, relative risk (95% confidence intervals); MI, myocardial infarction.

Duration, time period after trigger for which relative risk of infarction remained >1.0.

Anger, "very angry, furious, or enraged".

Exercise frequency, sessions of >6 METS of effort (vigorous exertion with panting, overheating). *, not reported.

RR, relative risk (95% confidence intervals); MI, myocardial infarction.

Duration, time period after trigger for which relative risk of infarction remained >1.0.

Anger, "very angry, furious, or enraged".

Exercise frequency, sessions of >6 METS of effort (vigorous exertion with panting, overheating). *, not reported.

Physical Exertion

The role of physical exertion as a trigger of myocardial infarction has been a subject of controversy, since most infarctions occur at rest or with mild activity (Table 1). One study of 1194 German patients reported 7.1% of infarct patients to have engaged in > 6 metabolic equivalents (METS) of exertion at the onset of infarction vs 3.9% of a control group (87). From case-crossover analysis, the relative risk of having engaged in this level of activity within 1 h of the onset of infarction was 2.1 (95% confidence interval 1.1-3.6). This increased risk was modified by the frequency with which the patient engaged in physical exercise on a routine basis. Exercise >4X/wk was associated with a relative risk of only 1.3 (95% confidence interval 0.8-2.2), whereas exercise <4X/wk imparted a relative risk of 6.9 (95% confidence interval 4.1-12.2). Similar findings emerged from the Myocardial Infarction Onset Study of 1228 patients, which also used the case-crossover method (88). Although only 4.4% of patients reported heavy physical exertion within 1 h of the onset of myocardial infarction, the relative risk of infarction within 1 h of heavy exertion (> 6 METS) was 5.9 (95% confidence interval 4.6-7.7). This risk increase persisted for 1 h after exercise (Fig. 8). These investigators also found that regular exercise lowered the risk of exertion-related infarction. The relative risks of infarction following exertion among individuals who exercised 1, 1 to 2, 3 to 4, and >5 X/wk were 107, 19.4, 8.6, and 2.4, respectively (Fig. 9) (Table 1). Known coronary artery disease, age, sex, and a variety of other clinical variables did not influence the increased relative risk of myocardial infarction imparted by exercise, with the exception of diabetes mellitus, where the relative risk was significantly higher (18.9 vs 5.4 for nondiabetics).

Similar results concerning the incidence of sudden cardiac death during exercise and the protective effect of regular exercise, were reported by Siscovick et al. (89) In a group of men who spent less than 20 min/wk engaged in vigorous exercise, the risk of sudden death during exercise was increased 56-fold, as compared to a five-fold increase in risk seen in men exercising more than 20 min/d. The absolute risk of sudden death was very

Fig. 8. Time of onset of myocardial infarction after an episode of heavy physical exertion (>6 METS) in 1228 patients. The relative risk is increased nearly 6-fold for the first hour after exertion, then decreases to approx the baseline risk of 1.0 (dotted line). Whiskers indicate the 95% confidence limits. Reprinted with permission from ref. 88.

Fig. 8. Time of onset of myocardial infarction after an episode of heavy physical exertion (>6 METS) in 1228 patients. The relative risk is increased nearly 6-fold for the first hour after exertion, then decreases to approx the baseline risk of 1.0 (dotted line). Whiskers indicate the 95% confidence limits. Reprinted with permission from ref. 88.

Fig. 9. Relation between risk of exertion triggered myocardial infarction and weekly frequency of heavy exertion. The relative risk of myocardial infarction (Y-axis) following heavy exertion is approx 100-fold in individuals who perform no heavy exertion during the week and falls to approx 2.4-fold for individuals with >5 sessions of heavy exertion per week. Whiskers indicate the 95% confidence limits. The dotted line indicates the baseline risk. Reprinted with permission from ref. 88.

Fig. 9. Relation between risk of exertion triggered myocardial infarction and weekly frequency of heavy exertion. The relative risk of myocardial infarction (Y-axis) following heavy exertion is approx 100-fold in individuals who perform no heavy exertion during the week and falls to approx 2.4-fold for individuals with >5 sessions of heavy exertion per week. Whiskers indicate the 95% confidence limits. The dotted line indicates the baseline risk. Reprinted with permission from ref. 88.

low, 1 cardiac death per 20,000 joggers per year. In marathon runners, the sudden death incidence was lower still: among over 200,000 participants in separate marathon races, 3 such deaths occurred during or immediately after the race (90). The Physician's Health Study, involving 21,481 male physicians initially free of self-reported cardiovascular disease, identified 122 cases of sudden death over 12 yr of follow-up. The relative risk of sudden death during and up to 30 min after exercise was 16.9 (95% confidence interval 10.5-27.0). This study also identified a protective effect of habitual exercise, with a gradient of relative risk from 74.1 for individuals exercising < 1 X/wk to 10.9 for those exercising >5 X/wk (91).

Sexual Activity

Anecdotal reports have related sexual intercourse to the onset of myocardial infarction (92,93), but there are little systematic data addressing this question. The Myocardial Infarction Onset Study interviewed 858 patients who were sexually active in the year prior to their myocardial infarction: 9% reported sexual activity within 24 h and 3% reported sexual activity within 2 h of the index acute myocardial infarction (94). From case-crossover analysis, the relative risk of myocardial infarction following intercourse was 2.5 (95% confidence interval 1.7-3.7). In contrast to the data for physical exertion, where the period of increased risk persisted for 1 h, the post-coital risk remained elevated for 2 h. There was no difference between patients with and without a history of angina pectoris; however, it was observed that regular exercise at >6 METs >3 X/wk decreased the relative risk to a nonsignificant 1.2 (95% confidence interval 0.4-3.7) (Table 1).

Mental Stress and Anger

Several studies have suggested that psychologically stressful life events, such as the death of a spouse, are potential triggers for myocardial infarction and sudden death (95,96). Other data have shown that periods of general calamity increase the frequency of myocardial infarction. For example, during the 1991 Persian Gulf War, Iraqi missile attacks on Israel nearly doubled the relative frequency of cardiovascular deaths in that country on the day of attack (97) (Fig. 10). Immediately following severe earthquakes in Athens (98), Hyogo, Japan (99), and Los Angeles (100), researchers documented an increase in cardiovascular mortality. In Los Angeles, there were 24 sudden cardiac deaths on the day of the quake, compared to an average of 5 such deaths per day the preceding week. Only 3 of the 24 deaths occurred in relation to unusual physical exertion (100).

Events such as the death of a loved one, earthquake, and war occur rarely and thus are of lesser importance when one is considering daily activities that may function as triggers of acute cardiovascular disease onset. The relation between acute cardiac events and more commonly experienced periods of high emotion, such as anger, has been suggested by work examining post-myocardial infarction prognosis in relation to personality characteristics. For example, one study addressing the controversial subject of the "Type A" personality found that increased first year post-myocardial infarction mortality correlated not with "global Type A" test scores, but with scores reflecting the subcomponents of anger expression, cynicism, and irritability (101). A relation between mental stress and cardiac prognosis is suggested by another study of 126 patients, over half of whom demonstrated a mental stress-induced fall in left ventricular ejection fraction (102). The relative risk of cardiac death, nonfatal myocardial infarction, or coronary revasculariza-

Trigger Worksheets For Mental Health

Fig. 10. The daily frequency of deaths in Israeli citizens >24 yr of age during the Persian Gulf War (bottom plot) compared to the same time period the year before (top plot) On January 18, 1991 (left vertical line) missiles launched from Iraq exploded in the Tel Aviv and Haifa areas. Daily warnings and attacks followed (larger filled points) until February 25 (right vertical line). The chi-square good-ness-of-fit test demonstrated significant inhomogeneity for the daily mortality during the 5-wk period, almost entirely due to the excess of cardiovascular deaths during the 24-h period of January 18. Reprinted with permission from ref. 97.

Fig. 10. The daily frequency of deaths in Israeli citizens >24 yr of age during the Persian Gulf War (bottom plot) compared to the same time period the year before (top plot) On January 18, 1991 (left vertical line) missiles launched from Iraq exploded in the Tel Aviv and Haifa areas. Daily warnings and attacks followed (larger filled points) until February 25 (right vertical line). The chi-square good-ness-of-fit test demonstrated significant inhomogeneity for the daily mortality during the 5-wk period, almost entirely due to the excess of cardiovascular deaths during the 24-h period of January 18. Reprinted with permission from ref. 97.

tion in that group was 2.4 X (95% confidence interval 1.13-5.14) that of the patients who had no mental stress-induced change in left ventricular ejection fraction.

A more precise relation between anger and acute myocardial infarction was elucidated by the Myocardial Infarction Onset Study, again using the case-crossover design (103). The relative risk of onset of myocardial infarction following an episode of anger was 2.3 (95% confidence interval 1.7-3.2), and remained at this level for 2 h (Table 1). Further analysis of these data found that the relative risk increase was influenced by the socioeconomic status of the individual subject (104). In patients with less than a high school education, the risk increase was greater (relative risk 3.3), and the risk increase was least in patients with some college education (relative risk 1.6).

Exposure to Specific Substances

Further analysis of the data from the Myocardial Infarction Onset Study has identified an increased risk of myocardial infarction following exposure to specific substances. One such analysis identified a nearly 24-fold increase in the risk of myocardial infarction in the 60 min following cocaine use (95% confidence interval 8.5-66.3) (105). Another report from the same group found a 4.8-fold increase in risk of infarction in the 60 min after smoking marijuana (95% confidence interval 2.4-9.5) (106). The Myocardial Infarction Onset Study, which was conducted in the Boston area, also identified small but statistically significant risk increases (1.48-1.69) for myocardial infarction on days of higher concentrations of particulate airborne pollutants in that city (107).

Superimposition of Triggers

One study compared the change in acute myocardial infarction incidence immediately following an earthquake between two intense quakes that occurred in Los Angeles in 1994 and San Francisco in 1989 (108). Interestingly, there was no statistically significant increase in hospital admission for acute myocardial infarction for the San Francisco quake, which occurred at 5:04 pm, compared to the Los Angeles quake which occurred at 4:31 am and was followed by a highly significant increase in myocardial infarction admission rate for that day. This suggests that in some circumstances, specific triggers may need to act in concert with circadian variations in cardiac vulnerability to produce their effect.

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