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Acute myocardial infarction after manual or automated snow removal
Acute Myocardial Infarction After Manual or Automated Snow Removal Barry A. Franklin, PhD, Peter George, MD, Richard Henry, DO, Seymour Gordon, Gerald C. Timmis, MD, and William W. O’Neill, MD older temperatures and major snowfalls are often followed by an increased number of cardiovascuC lar events from ischemic heart disease, especially among men.1– 8 Considering the body’s normal thermoregulatory responses to cold, including increased platelet aggregability and plasma viscosity,9 coronary spasm or vasoconstriction,10 the marked increases in heart rate and systolic blood pressure that can occur when clearing snow from sidewalks and driveways,11 as well as ischemia at a lower rate–pressure product,12 it appears that a variety of pathophysiologic mechanisms for acute myocardial infarction (AMI) may be operative in this environment. On January 2, 1999, the greater metropolitan Detroit area experienced a major snowfall (28 cm), followed by an unusually large amount of heavy wet snow over the next 12 days (total 61 cm). Average temperature and windchill for this period were ⫺10.2°C and ⫺26.1°C, respectively. •••
We retrospectively reviewed all patient admission records (n ⫽ 158) from our emergency department (chest pain center), which serves a community of approximately 400,000 people, during the period of January 2 to 14, 1999, to identify patients admitted with AMI. Patients were interviewed during the hospital admission by an emergency center nurse or physician using standardized forms. When patients were unable to be interviewed personally or during the admission, the information was obtained from interview with the spouse or family member. Medical records were reviewed by a study physician to obtain demographic data and clinical characteristics of the patients with specific reference to age, gender, coronary risk factors, history of coronary artery disease, associated symptomatology, and the specific activities engaged in before the AMI. Our review of the hospital’s chest pain center records identified 20 patients with AMIs, 5 of whom (all men) had experienced their infarction during or soon after snow removal (Table 1).13 •••
Although cardiovascular events occur regularly after heavy snow shoveling,1 our findings suggest that even the reduced aerobic and cardiac demands of automated snow removal11 may trigger AMI in patients at risk for heart disease. Of 20 patients who were From the Department of Medicine, Division of Cardiology (Cardiac Rehabilitation), William Beaumont Hospital, Royal Oak, Michigan. Dr. Franklin’s address is: Cardiac Rehabilitation and Exercise Laboratories, Beaumont Rehabilitation and Health Center, 746 Purdy Street, Birmingham, Michigan 48009. E-mail: [email protected]. Manuscript received October 4, 2000; revised manuscript received and accepted January 5, 2001.
1282
©2001 by Excerpta Medica, Inc. All rights reserved. The American Journal of Cardiology Vol. 87 June 1, 2001
MD,
admitted with AMI over a 12-day period of cold temperatures and blizzard conditions, 5 (25%) habitually sedentary men, aged 55 to 77 years, were engaged in snow removal. Two of the 5 patients had been using an automated snow thrower, rather than shoveling. Three of the acute cardiovascular events were classified as non–Q-wave AMIs and 2 as Q-wave AMIs. Medical histories and coronary risk factors for these patients included: previous AMI (1 patient), previous percutaneous transluminal coronary angioplasty (2 patients), obesity (4 patients), sedentary lifestyle (5 patients), family history of heart disease (3 patients), systemic hypertension (1 patient), hypercholesterolemia (2 patients), and cigarette smoking (2 patients). In each case, symptoms transiently subsided with rest, following nitroglycerin administration, or both, perhaps suggesting musculoskeletal trauma or angina rather than AMI. Nevertheless, their continued snow removal despite symptoms, which may portend an obsessive-compulsive or type A behavior pattern, resulted in a universal delay in seeking medical attention. All 5 patients underwent successful percutaneous transluminal coronary angioplasty with stenting and were discharged within 5 days. Four of the 5 patients who experienced cardiovascular events during snow removal were clearing their driveways between 6 and 8 A.M., a period of the day associated with an already heightened risk for AMI.14 Presumably, potential triggers of coronary plaque rupture and thrombosis are activated during the early morning hours, including circadian surges in heart rate, blood pressure, catecholamines, and cortisol, platelet aggregability, coronary vascular tone, plasma viscosity, and fibrinolytic activity associated with awakening and assuming an upright posture. Superimposed physical, cognitive, and environmental stresses can accentuate these responses, and exacerbate the risk of acute cardiovascular events.15 Recently, in response to an emerging body of scientific evidence, the American Heart Association reclassified obesity (defined as a body mass index ⱖ30 kg/m2) as major modifiable risk factor for coronary heart disease.16 Using this definition, 4 of the 5 men who sustained an AMI during or soon after snow removal were classified as obese, whereas the remaining subject was overweight. Previous studies have shown that obesity is associated with disproportionate increases in the rate–pressure product during physical exertion.17 Excessive cardiac demands, especially in a cold environment, may precipitate angina pectoris, AMI, or both. The most common coronary risk factor among those who experienced an AMI during snow removal 0002-9149/01/$–see front matter PII S0002-9149(01)01520-X
TABLE 1 Cardiovascular Clinical Data in the 5 Sedentary Men*
Patient 1 2 3 4 5
Age Previous Previous Previous (Years) SH CS 1C AP AMI PTCA 55 58 64 70 77
E E E E ⫹
⫹ E E E ⫹
E ⫹ E E ⫹
E E ⫹ E E
E ⫹ E E E
E ⫹ E ⫹ E
BMI (kg/m2) 34.6 30.7 33.8 27.7 30.8
Snow Removal Technique
Symptoms During Snow Removal
Confirmed Shoveling EST Substernal CP Sweating AMI ⫹ E E ⫹ ⫹
E ⫹ ⫹ E E
⫹ ⫹ ⫹ ⫹ ⫹
E ⫹ E E ⫹
⫹ ⫹ ⫹ ⫹ ⫹
Time of AMI pm am am am am
*Persons not participating in a regular exercise program or meeting the minimal physical activity recommendations from the U.S. Surgeon General’s report.13 AP ⫽ angina pectoris; BMI ⫽ body mass index; C ⫽ cholesterol; CP ⫽ chest pain; CS ⫽ cigarette smoker; EST ⫽ electric snow thrower; PTCA ⫽ percutaneous transluminal coronary angioplasty; SH ⫽ systemic hypertension.
was a history of physical inactivity (n ⫽ 5). The notion that strenuous physical activity (ⱖ6 METs) can trigger AMI, particularly among persons with known or occult coronary artery disease and who are habitually sedentary, has been substantiated by several recent studies.18 –20 This may occur with abrupt increases in heart rate and blood pressure giving rise to hemodynamic stresses that disrupt vulnerable atherosclerotic plaque and lead to thrombotic occlusion of a coronary vessel.21 An increase in platelet activation and hyperreactivity, which could contribute to (or even initiate) coronary thrombosis, has also been reported in sedentary subjects, but not physically conditioned ones, who engaged in sporadic high intensity exercise.22 In summary, our findings suggest that habitually sedentary middle-aged and older patients at risk for heart disease, including obese and/or overweight individuals, current and former smokers, those with a history of hypercholesterolemia and/or systemic hypertension, as well as those with previous AMI or coronary revascularization, should be cautioned regarding the risk of AMI following manual or even automated snow removal, especially during the early morning hours. 1. Heppell R, Hawley SK, Channer KS. Snow shoveller’s infarction (letter). BMJ
1991;302:469 – 470. 2. Glass RI, Zack MM. Increase in deaths from ischemic heart-disease after
blizzards. Lancet 1979;1:485– 487. 3. Rogot E, Padgett SJ. Associations of coronary and stroke mortality with
temperature and snowfall in the United States, 1962–1966. Am J Epidemiol 1976:103:565–572. 4. Glass RI, Wiesenthal AM, Zack MM, Preston M. Risk factors for myocardial infarction associated with the Chicago snowstorm of Jan 13–15, 1979. JAMA 1981;245:164 –165. 5. Faich G, Rose R. Blizzard morbidity and mortality: Rhode Island, 1978. Am J Public Health 1979;69:1050 –1052.
6. Auliciems A, Frost D. Temperature and cardiovascular deaths in Montreal. Int J Biometeorol 1989;33:151–156. 7. Baker-Blocker A. Winter weather and cardiovascular mortality in Minneapolis-St. Paul. Am J Public Health 1982;72:261–265. 8. Gorjanc ML, Flanders WD, VanDerslice J, Hersh J, Malilay J. Effects of temperature and snowfall on mortality in Pennsylvania. Am J Epidemiol 1999; 149:1152–1160. 9. Keatinge WR, Coleshaw SR, Cotter F. Increases in platelet and red cell counts, blood viscosity, and arterial pressure during mild surface cooling: factors in mortality from coronary and cerebral thrombosis in winter. BMJ 1984;289:1405– 1408. 10. Kawahara J, Sano H, Fukuzaki H, Saito K, Hirouchi H. Acute effects of exposure to cold on blood pressure, platelet function and sympathetic nervous activity in humans. Am J Hypertens 1989;2:724 –726. 11. Franklin BA, Hogan P, Bonzheim K, Bakalyar D, Terrien E, Gordon S, Timmis GC. Cardiac demands of heavy snow shoveling. JAMA 1995;273:880 – 882. 12. Juneau M, Johnstone M, Dempsey E, Waters DD. Exercise-induced myocardial ischemia in a cold environment. Effect of antianginal medications. Circulation 1989;79:1015–1020. 13. United States Department of Health, and Human Services. Physical activity and health: a report of the Surgeon General. Atlanta, GA: US Department of Health and Human Services, Centers for Disease Control and Prevention, National Center for Chronic Disease Prevention and Health Promotion, 1996. 14. Muller JE. Morning increase of onset of myocardial infarction. Implications concerning triggering events. Cardiology 1989;76:96 –104. 15. Willich SN, Maclure M, Mittleman M, Arntz HR, Muller JE. Sudden cardiac death: support for a role of triggering in causation. Circulation 1993;87:1442– 1450. 16. Eckel RH, Krauss RM. American Heart Association call to action: obesity as a major risk factor for coronary heart disease. Circulation 1998;97:2099 –2100. 17. Alexander JK. Obesity and cardiac performance. Am J Cardiol 1964;14:860 – 865. 18. Mittleman MA, Maclure M, Tofler GH, Sherwood JB, Goldberg RJ, Muller JE. Triggering of acute myocardial infarction by heavy physical exertion. N Engl J Med 1993;329:1677–1683. 19. Willich SN, Lewis M, Lo¨wel H, Arntz HR, Schubert F, Schroder R. Physical exertion as a trigger of acute myocardial infarction. N Engl J Med 1993;329: 1684 –1690. 20. Giri S, Thompson PD, Kiernan FJ, Clive J, Fram DB, Mitchel JF, Hirst JA, McKay RG, Waters DD. Clinical and angiographic characteristics of exertionrelated acute myocardial infarction. JAMA 1999;282:1731–1736. 21. Richardson PD, Davies MJ, Born GV. Influence of plaque configuration and stress distribution on fissuring of coronary atherosclerotic plaques. Lancet 1989; 2:941–944. 22. Kestin AS, Ellis PA, Barnard MR, Errichetti A, Rosner BA, Michelson AD. Effect of strenuous exercise on platelet activation state and reactivity. Circulation 1993;88:1502–1511.
BRIEF REPORTS
1283
We retrospectively reviewed all patient admission records (n ⫽ 158) from our emergency department (chest pain center), which serves a community of approximately 400,000 people, during the period of January 2 to 14, 1999, to identify patients admitted with AMI. Patients were interviewed during the hospital admission by an emergency center nurse or physician using standardized forms. When patients were unable to be interviewed personally or during the admission, the information was obtained from interview with the spouse or family member. Medical records were reviewed by a study physician to obtain demographic data and clinical characteristics of the patients with specific reference to age, gender, coronary risk factors, history of coronary artery disease, associated symptomatology, and the specific activities engaged in before the AMI. Our review of the hospital’s chest pain center records identified 20 patients with AMIs, 5 of whom (all men) had experienced their infarction during or soon after snow removal (Table 1).13 •••
Although cardiovascular events occur regularly after heavy snow shoveling,1 our findings suggest that even the reduced aerobic and cardiac demands of automated snow removal11 may trigger AMI in patients at risk for heart disease. Of 20 patients who were From the Department of Medicine, Division of Cardiology (Cardiac Rehabilitation), William Beaumont Hospital, Royal Oak, Michigan. Dr. Franklin’s address is: Cardiac Rehabilitation and Exercise Laboratories, Beaumont Rehabilitation and Health Center, 746 Purdy Street, Birmingham, Michigan 48009. E-mail: [email protected]. Manuscript received October 4, 2000; revised manuscript received and accepted January 5, 2001.
1282
©2001 by Excerpta Medica, Inc. All rights reserved. The American Journal of Cardiology Vol. 87 June 1, 2001
MD,
admitted with AMI over a 12-day period of cold temperatures and blizzard conditions, 5 (25%) habitually sedentary men, aged 55 to 77 years, were engaged in snow removal. Two of the 5 patients had been using an automated snow thrower, rather than shoveling. Three of the acute cardiovascular events were classified as non–Q-wave AMIs and 2 as Q-wave AMIs. Medical histories and coronary risk factors for these patients included: previous AMI (1 patient), previous percutaneous transluminal coronary angioplasty (2 patients), obesity (4 patients), sedentary lifestyle (5 patients), family history of heart disease (3 patients), systemic hypertension (1 patient), hypercholesterolemia (2 patients), and cigarette smoking (2 patients). In each case, symptoms transiently subsided with rest, following nitroglycerin administration, or both, perhaps suggesting musculoskeletal trauma or angina rather than AMI. Nevertheless, their continued snow removal despite symptoms, which may portend an obsessive-compulsive or type A behavior pattern, resulted in a universal delay in seeking medical attention. All 5 patients underwent successful percutaneous transluminal coronary angioplasty with stenting and were discharged within 5 days. Four of the 5 patients who experienced cardiovascular events during snow removal were clearing their driveways between 6 and 8 A.M., a period of the day associated with an already heightened risk for AMI.14 Presumably, potential triggers of coronary plaque rupture and thrombosis are activated during the early morning hours, including circadian surges in heart rate, blood pressure, catecholamines, and cortisol, platelet aggregability, coronary vascular tone, plasma viscosity, and fibrinolytic activity associated with awakening and assuming an upright posture. Superimposed physical, cognitive, and environmental stresses can accentuate these responses, and exacerbate the risk of acute cardiovascular events.15 Recently, in response to an emerging body of scientific evidence, the American Heart Association reclassified obesity (defined as a body mass index ⱖ30 kg/m2) as major modifiable risk factor for coronary heart disease.16 Using this definition, 4 of the 5 men who sustained an AMI during or soon after snow removal were classified as obese, whereas the remaining subject was overweight. Previous studies have shown that obesity is associated with disproportionate increases in the rate–pressure product during physical exertion.17 Excessive cardiac demands, especially in a cold environment, may precipitate angina pectoris, AMI, or both. The most common coronary risk factor among those who experienced an AMI during snow removal 0002-9149/01/$–see front matter PII S0002-9149(01)01520-X
TABLE 1 Cardiovascular Clinical Data in the 5 Sedentary Men*
Patient 1 2 3 4 5
Age Previous Previous Previous (Years) SH CS 1C AP AMI PTCA 55 58 64 70 77
E E E E ⫹
⫹ E E E ⫹
E ⫹ E E ⫹
E E ⫹ E E
E ⫹ E E E
E ⫹ E ⫹ E
BMI (kg/m2) 34.6 30.7 33.8 27.7 30.8
Snow Removal Technique
Symptoms During Snow Removal
Confirmed Shoveling EST Substernal CP Sweating AMI ⫹ E E ⫹ ⫹
E ⫹ ⫹ E E
⫹ ⫹ ⫹ ⫹ ⫹
E ⫹ E E ⫹
⫹ ⫹ ⫹ ⫹ ⫹
Time of AMI pm am am am am
*Persons not participating in a regular exercise program or meeting the minimal physical activity recommendations from the U.S. Surgeon General’s report.13 AP ⫽ angina pectoris; BMI ⫽ body mass index; C ⫽ cholesterol; CP ⫽ chest pain; CS ⫽ cigarette smoker; EST ⫽ electric snow thrower; PTCA ⫽ percutaneous transluminal coronary angioplasty; SH ⫽ systemic hypertension.
was a history of physical inactivity (n ⫽ 5). The notion that strenuous physical activity (ⱖ6 METs) can trigger AMI, particularly among persons with known or occult coronary artery disease and who are habitually sedentary, has been substantiated by several recent studies.18 –20 This may occur with abrupt increases in heart rate and blood pressure giving rise to hemodynamic stresses that disrupt vulnerable atherosclerotic plaque and lead to thrombotic occlusion of a coronary vessel.21 An increase in platelet activation and hyperreactivity, which could contribute to (or even initiate) coronary thrombosis, has also been reported in sedentary subjects, but not physically conditioned ones, who engaged in sporadic high intensity exercise.22 In summary, our findings suggest that habitually sedentary middle-aged and older patients at risk for heart disease, including obese and/or overweight individuals, current and former smokers, those with a history of hypercholesterolemia and/or systemic hypertension, as well as those with previous AMI or coronary revascularization, should be cautioned regarding the risk of AMI following manual or even automated snow removal, especially during the early morning hours. 1. Heppell R, Hawley SK, Channer KS. Snow shoveller’s infarction (letter). BMJ
1991;302:469 – 470. 2. Glass RI, Zack MM. Increase in deaths from ischemic heart-disease after
blizzards. Lancet 1979;1:485– 487. 3. Rogot E, Padgett SJ. Associations of coronary and stroke mortality with
temperature and snowfall in the United States, 1962–1966. Am J Epidemiol 1976:103:565–572. 4. Glass RI, Wiesenthal AM, Zack MM, Preston M. Risk factors for myocardial infarction associated with the Chicago snowstorm of Jan 13–15, 1979. JAMA 1981;245:164 –165. 5. Faich G, Rose R. Blizzard morbidity and mortality: Rhode Island, 1978. Am J Public Health 1979;69:1050 –1052.
6. Auliciems A, Frost D. Temperature and cardiovascular deaths in Montreal. Int J Biometeorol 1989;33:151–156. 7. Baker-Blocker A. Winter weather and cardiovascular mortality in Minneapolis-St. Paul. Am J Public Health 1982;72:261–265. 8. Gorjanc ML, Flanders WD, VanDerslice J, Hersh J, Malilay J. Effects of temperature and snowfall on mortality in Pennsylvania. Am J Epidemiol 1999; 149:1152–1160. 9. Keatinge WR, Coleshaw SR, Cotter F. Increases in platelet and red cell counts, blood viscosity, and arterial pressure during mild surface cooling: factors in mortality from coronary and cerebral thrombosis in winter. BMJ 1984;289:1405– 1408. 10. Kawahara J, Sano H, Fukuzaki H, Saito K, Hirouchi H. Acute effects of exposure to cold on blood pressure, platelet function and sympathetic nervous activity in humans. Am J Hypertens 1989;2:724 –726. 11. Franklin BA, Hogan P, Bonzheim K, Bakalyar D, Terrien E, Gordon S, Timmis GC. Cardiac demands of heavy snow shoveling. JAMA 1995;273:880 – 882. 12. Juneau M, Johnstone M, Dempsey E, Waters DD. Exercise-induced myocardial ischemia in a cold environment. Effect of antianginal medications. Circulation 1989;79:1015–1020. 13. United States Department of Health, and Human Services. Physical activity and health: a report of the Surgeon General. Atlanta, GA: US Department of Health and Human Services, Centers for Disease Control and Prevention, National Center for Chronic Disease Prevention and Health Promotion, 1996. 14. Muller JE. Morning increase of onset of myocardial infarction. Implications concerning triggering events. Cardiology 1989;76:96 –104. 15. Willich SN, Maclure M, Mittleman M, Arntz HR, Muller JE. Sudden cardiac death: support for a role of triggering in causation. Circulation 1993;87:1442– 1450. 16. Eckel RH, Krauss RM. American Heart Association call to action: obesity as a major risk factor for coronary heart disease. Circulation 1998;97:2099 –2100. 17. Alexander JK. Obesity and cardiac performance. Am J Cardiol 1964;14:860 – 865. 18. Mittleman MA, Maclure M, Tofler GH, Sherwood JB, Goldberg RJ, Muller JE. Triggering of acute myocardial infarction by heavy physical exertion. N Engl J Med 1993;329:1677–1683. 19. Willich SN, Lewis M, Lo¨wel H, Arntz HR, Schubert F, Schroder R. Physical exertion as a trigger of acute myocardial infarction. N Engl J Med 1993;329: 1684 –1690. 20. Giri S, Thompson PD, Kiernan FJ, Clive J, Fram DB, Mitchel JF, Hirst JA, McKay RG, Waters DD. Clinical and angiographic characteristics of exertionrelated acute myocardial infarction. JAMA 1999;282:1731–1736. 21. Richardson PD, Davies MJ, Born GV. Influence of plaque configuration and stress distribution on fissuring of coronary atherosclerotic plaques. Lancet 1989; 2:941–944. 22. Kestin AS, Ellis PA, Barnard MR, Errichetti A, Rosner BA, Michelson AD. Effect of strenuous exercise on platelet activation state and reactivity. Circulation 1993;88:1502–1511.
BRIEF REPORTS
1283