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Exercise-Induced Oxidative Stress in Patients During Thallium Stress Testing
Exercise-Induced Oxidative Stress in Patients During Thallium Stress Testing DAVID ALEXANDER LEAF, MD, MPH,* MICHAEL T. KLEINMAN, PHD,:\:
MARK YUSIN, MD,t
ABSTRACT Background: Free radical injury is implicated ~n the ~athogenesis of coronary artery disease, ~ncludmg atherogenesis and reperfusionlinJUry. Strenuous physical exercise can cause oxidative stress by several mechanisms, includingreperfusionlinjury. We hypothesize that exercise-induced lipid peroxidation is greater among those with than those without exerciseinduced myocardial ischemia. Methods: The effect of physical exercise stress testing on plasma malonaldehyde (MDA) levels was compared between patients with (Group A, N = 8) and without (Group B) exer~ise-i!lduced myocardial ischemia by thallium ImagIng. Analysis: Two-way ANOVA was used to compare plasma MDA levels pre- and post-exercise and paired t-test comparisons were conducted for percent MDA changes between Group A and Group B patients. Results: Two-way ANOVA revealed a significant (P = 0.002) directional difference in response to exercise between the groups' mean plasma MDA levels (Group A increased by 46 ± 12.7 percent, Group B decreased by 16.8 ± 4.6 percent). Conclusions: Differences in exercise-induced lipid peroxidation between patients with and without thallium documentation of myocar~ial ischemia have important implications In the development of clinical markers of coronary artery disease and further research related to atherogenesis. KEY INDEXING TERMS: Myocardial ischFrom the *Division General Internal Medicine, West Los Angeles VAMC and UCLA School of Medicine, tDivision of Cardiology, West .Los Angeles VAMC, Los Angeles, and Wepartment of Commu~nty and Environmental Medicine, University of California at Irvme, Irvine, California. Received June 6, 1997; accepted in revised form September 23 1997. ' Correspondence: David Alexander Leaf, MD, Division of General Internal Medicine, 111G, West Los Angeles VAMC, Wilshire & Sawtelle Boulevards, Los Angeles, CA 90073. THE AMERICAN JOURNAL OF THE MEDICAL SCIENCES
DONNA GALLIK, MD,t
emia; Oxidative stress; Lipid peroxidation. [Am J Med Sci 1998;315(3):185-187.]
re~ radical injury is implicated in the pathogenF eSIS of coronary artery disease including atherogenesis! and reperfusion or inju;y.2-4 Strenuous physical exercise can cause oxidative stress by several mechanis.ms, including reperfusion or injury. 5 We hypothesIze that exercise-induced oxidative stress is greater among those with exercise-induced myocardial ischemia than in those without it. The significance of this study is that if differences can be demons.trated us~ng relatively simple techniques, more specIfic expenments can be designed and implemented to apportion the importance of mechanis~s indicative.of oxidative stress to the etiology of cardIOvascular dIsease. This could also be relevant to the deve~op~ent o~ cost-ef~ective adjuncts to improve the specIficIty of dIagnostIc exercise stress testing. Materials and Methods
Eighteen patients who were referred for exercise testing with thallium imaging CETT-thallium) were enrolled into this prospective study. Exclusion criteria included ethanol abuse and the use of antioxidant compounds, such as probucol and vitamin supplements. Based on thallium stress testing, patients were divided into 2 groups: Group A (n = 8; all male) had reversible thallium defects and Group B (n = 10; nine male, 1 female) had normal thallium studies. Patient profiles revealed sim~lar cl~nical characteri.stics (Group A vs. Group B) mcludmg: personal hIstory of myocardial infarc~ion (4 vs. 3), diabetes mellitus (1 vs. 2), hypertenSIOn (4 vs. 6) and/or dyslipidemia (4 vs. 3)' and c~rdiac medications: beta blockers (4 vs. 4): calCIUm channel blockers (5 vs. 4), and angiotensinconverting enzyme inhibitors (3 vs. 4). Monitor~d ~xercise testing was conducted using a symptom-hmited standard Bruce protocol. Immediately post-exercise, single photon emission computed tomography (SPECT) imaging was performed 185
Thallium Stress Testing
Table 1. Patient Exercise Results
Age (years)
Exercise Duration (minutes)
MAX Predicted HR (percent)
Group A (N MEAN ±SD
62.4 ±12.5
5.6 ±2.8
MEAN ±SD
55.5 ±10.2
7.4 ±2.7
Group B (N
=
8)
80 ±16.4 =
MAXRPP (bpm X mmHg)
21,596 ±7,889
10)
85.9 ±13.8
24,680 ±4,932
Group A = positive exercise thallium study, Group B = negative exercise thallium study; MAX = maximum; HR = heart rate; RPP = rate pressure product.
(ADAC Laboratories, Milpitas, CA). Image acquisition was 1800 using a 64 (ts) 16 matrix with 20 seconds of stop. Redistribution images were obtained 4 hours later. Number, location, and degree of reversibility of defects was reported. Plasma samples for measurements of malonaldehyde (MDA), a marker of lipid peroxidation, were obtained immediately prior to and following completion of the exercise stress test. These samples were submitted in a blind manner and duplicate analyses were performed to determine the extent of lipid peroxidation as thiobarbituric reactive substances. 6 Results of duplicate analyses were ± 8% by this method. Results
The exercise stress test results are shown in Table 1. Two-way ANOVA comparing plasma MDA levels pre-and post-exercise, shown in Table 2, revealed that plasma MDA levels did not differ between groups A and B before and after exercise. While there was significant inter-individual variation, a significant P = 0.002) directional difference in response to exercise was noted among the groups (ie, an exercise-induced increase in plasma MDA levels was observed in Group A but there was a decrease in plasma MDA levels in Group B patients). Paired t-test comparisons conducted for percent MDA changes between Group A and Group B subjects revealed significant differences. MDA change between Group A (46 ± 12.7%) and Group B (-16.8 ± 4.6%) patients P < 0.001). Spearman rank order correlation coefficients between changes in plasma MDA levels and duration of exercise, percent maximal predicted heart rate, and peak rate-pressure product (r = -0.18, -0.05, and -0.12 respectively) were not significant. Patients were classified according to positive or negative changes in plasma MDA levels. Plasma MDA levels after exercise were unchanged in 2 patients. Of those patients who developed increased MDA levels with ex186
ercise (n = 7), all but 1 had at least 1 reversible thallium defect. Among patients with decreased plasma MDA levels (n = 9), 8 had no observable thallium defects and 1 had a mixed (1 reversible and 1 fixed area of decreased perfusion) defect. Discussion
This study did not attempt to differentiate whether or not the increased levels of exercise-induced oxidative stress among those patients with positive thallium stress tests (one thallium defect or more) is attributable to the presence of atherosclerosis in this group, to increased innate level of susceptibility to oxidative stress, or to the effects of exercise-induced myocardial ischemia and reperfusion. However, it is noted that all 8 subjects with exerciseinduced increases in plasma MDA levels had ischemia by exercise-thallium testing (completed In = 71 or partial [n = IJ reversibility of thallium defects), suggesting that exercise-induced oxidative stress is related to ischemia and reperfusion. The source of
Table 2. Exercise-Induced Changes in Plasma Malonaldehyde (MDA) Levels Compared Between Patients with Positive (Group Al and Negative (Group Bl Thallium Stress Tests"
Subject
Preexercise MDA
Postexercise MDA
Group A (N
8)
=
-18'Yr +1480/,. +72'Yr +31% + 83'7c + 48'Yr. +53% +34'Yr
1 3 5 6 7 10 11 14
5.0 5.6 2.6 4.9 1.8 3.3 2.1 2.3
4.1 13.9 4.9 6.4 3.3 4.9 3.2 3.1
Mean ± SD
3.45 ± 1.50
5.4 7 ± 1.02t
Group B (N 2 4 8 9 12 13 15 16 17 18
5.0 6.4 4.1 4.9 6.6 5.7 5.8 6.4 3.9 4.2
Mean:+: SD
5.30 :+: 1.02
=
Percent Change
+46:+: 12.7%:j:
10) -18% -23% -20% -33% -14% -33% -14% -47% -36% 0%
4.1 4.9 3.3 3.3 5.7 3.8 5.0 3.4 2.5 4.2 4.07 :+: 0.96
* Using two-way ANOVA (serum MDA
=
-16.8 :+: 4.6%
nanomolesI mL). (P = 0.002,
t MDA in response to exercise significantly different
F value = 13.63). :j: Paired t-test comparison of MDA percent change between groups is significant (P < 0.0001). March 1998 Volume 315 Number 3
Leaf et 01
exercise-induced lipid peroxidation is uncertain, and could be related to regional (ie, myocardial) or global (ie, other body tissues) oxidative stress. Further study of this might include analysis of MDA levels from blood reflecting myocardial blood flow, such as the coronary sinus. Another possibility, requiring evaluation with longitudinal studies, is that exercise-induced increases in plasma MDA levels are an a priori predictor of 'chose who develop exercise-induced ischemia. The interpretation of these findings is limited by the relatively small number of patients and the high prevalence of men studied. In a previous study of healthy young athletes, we found although some markers of lipid peroxidation (expired ethane and pentane) increased during maximal exercise stress testing, plasma MDA levels did not increase. 7 Plasma MDA levels were not measured during the course of exercise; hence we cannot exclude the possibility of MDA redistribution occurring from serum to tissue membranes during exercise, nor the effect of endogenous antioxidant systems in the healthy individuals and in Group B subjects. A limitation comparing these findings with our previous findings and those of others stems from differences in exercise protocols and the timing of MDA sampling. Another limitation is the potential lack of specificity of the use of the thiobarbituric acid (TBA) assay as a determinant of plasma MDA. 8 The repeated measures used in this study, however, enabled us to observe that there are population-derived response differences. Marked differences in exercise-related changes in plasma MDA levels between those with and without
THE AMERICAN JOURNAL OF THE MEDICAL SCIENCES
exercise-induced ischemia are noted, which may have implications in the development of adjuncts to diagnostic exercise stress testing. Acknowledgements
This project was funded by the American Heart Association (Greater Los Angeles Affiliate), Grant Award No. 991 GI-2, and is part of programs supported by the University of California Irvine Center for Occupational and Environmental Health. References 1. Steinberg D, Parthsarathy S, Carew TE, Khoo JC, Wit-
2.
3. 4.
5. 6. 7. 8.
zum JL. Beyond cholesterol: modifications oflow-density lipoprotein that increase its atherogenicity. N Engl J Med. 1989; 320:915-24. De Scheerder IK, Van de Kraay AMM, Lamers JMJ, Koster JF, de Jong JW, Serruys PW. Myocardial malonaldehyde and uric acid release after short-term coronary occlusion during coronary angioplasty: potential mechanisms of free radical generation. Am J Cardiol. 1991;68:392-5. Davies SW, Ranjadayalan K, Wickens DG, Dormandy TL, Timmis AD. Lipid peroxidation associated with successful thrombolysis. Lancet. 1990;335:741-3. Roberts MJD, Young IS, Trouton TG, Trimble ER, Khan MM, Webb SW, et al. Transient release of lipid peroxides after coronary artery balloon angioplasty. Lancet. 1990; 336:143-5. Li JJ. Exercise and oxidative stress: role ofthe cellular antioxidant systems. Exerc 8ports 8ci Rev. 1995;23:135-6. Esterbauer H, Cheeseman KH. Determination of aldehydic lipid peroxidation products: malonaldehyde and 4-hydroxynonenal. Methods Enzymol. 1990; 186:504-8. Leaf DA, Kleinman MT, Hamilton M, Barstow TJ. The effect of exercise intensity on lipid peroxidation. Med 8ci 8ports Exerc. 1997;29(8):1036-9. Bowen PE, Mobarhan S. Evidence from cancer intervention and biomarker studies and the development ofbiochemical markers. Am J Clin Nutr. 1995;62(8):14038-14098.
187
MARK YUSIN, MD,t
ABSTRACT Background: Free radical injury is implicated ~n the ~athogenesis of coronary artery disease, ~ncludmg atherogenesis and reperfusionlinJUry. Strenuous physical exercise can cause oxidative stress by several mechanisms, includingreperfusionlinjury. We hypothesize that exercise-induced lipid peroxidation is greater among those with than those without exerciseinduced myocardial ischemia. Methods: The effect of physical exercise stress testing on plasma malonaldehyde (MDA) levels was compared between patients with (Group A, N = 8) and without (Group B) exer~ise-i!lduced myocardial ischemia by thallium ImagIng. Analysis: Two-way ANOVA was used to compare plasma MDA levels pre- and post-exercise and paired t-test comparisons were conducted for percent MDA changes between Group A and Group B patients. Results: Two-way ANOVA revealed a significant (P = 0.002) directional difference in response to exercise between the groups' mean plasma MDA levels (Group A increased by 46 ± 12.7 percent, Group B decreased by 16.8 ± 4.6 percent). Conclusions: Differences in exercise-induced lipid peroxidation between patients with and without thallium documentation of myocar~ial ischemia have important implications In the development of clinical markers of coronary artery disease and further research related to atherogenesis. KEY INDEXING TERMS: Myocardial ischFrom the *Division General Internal Medicine, West Los Angeles VAMC and UCLA School of Medicine, tDivision of Cardiology, West .Los Angeles VAMC, Los Angeles, and Wepartment of Commu~nty and Environmental Medicine, University of California at Irvme, Irvine, California. Received June 6, 1997; accepted in revised form September 23 1997. ' Correspondence: David Alexander Leaf, MD, Division of General Internal Medicine, 111G, West Los Angeles VAMC, Wilshire & Sawtelle Boulevards, Los Angeles, CA 90073. THE AMERICAN JOURNAL OF THE MEDICAL SCIENCES
DONNA GALLIK, MD,t
emia; Oxidative stress; Lipid peroxidation. [Am J Med Sci 1998;315(3):185-187.]
re~ radical injury is implicated in the pathogenF eSIS of coronary artery disease including atherogenesis! and reperfusion or inju;y.2-4 Strenuous physical exercise can cause oxidative stress by several mechanis.ms, including reperfusion or injury. 5 We hypothesIze that exercise-induced oxidative stress is greater among those with exercise-induced myocardial ischemia than in those without it. The significance of this study is that if differences can be demons.trated us~ng relatively simple techniques, more specIfic expenments can be designed and implemented to apportion the importance of mechanis~s indicative.of oxidative stress to the etiology of cardIOvascular dIsease. This could also be relevant to the deve~op~ent o~ cost-ef~ective adjuncts to improve the specIficIty of dIagnostIc exercise stress testing. Materials and Methods
Eighteen patients who were referred for exercise testing with thallium imaging CETT-thallium) were enrolled into this prospective study. Exclusion criteria included ethanol abuse and the use of antioxidant compounds, such as probucol and vitamin supplements. Based on thallium stress testing, patients were divided into 2 groups: Group A (n = 8; all male) had reversible thallium defects and Group B (n = 10; nine male, 1 female) had normal thallium studies. Patient profiles revealed sim~lar cl~nical characteri.stics (Group A vs. Group B) mcludmg: personal hIstory of myocardial infarc~ion (4 vs. 3), diabetes mellitus (1 vs. 2), hypertenSIOn (4 vs. 6) and/or dyslipidemia (4 vs. 3)' and c~rdiac medications: beta blockers (4 vs. 4): calCIUm channel blockers (5 vs. 4), and angiotensinconverting enzyme inhibitors (3 vs. 4). Monitor~d ~xercise testing was conducted using a symptom-hmited standard Bruce protocol. Immediately post-exercise, single photon emission computed tomography (SPECT) imaging was performed 185
Thallium Stress Testing
Table 1. Patient Exercise Results
Age (years)
Exercise Duration (minutes)
MAX Predicted HR (percent)
Group A (N MEAN ±SD
62.4 ±12.5
5.6 ±2.8
MEAN ±SD
55.5 ±10.2
7.4 ±2.7
Group B (N
=
8)
80 ±16.4 =
MAXRPP (bpm X mmHg)
21,596 ±7,889
10)
85.9 ±13.8
24,680 ±4,932
Group A = positive exercise thallium study, Group B = negative exercise thallium study; MAX = maximum; HR = heart rate; RPP = rate pressure product.
(ADAC Laboratories, Milpitas, CA). Image acquisition was 1800 using a 64 (ts) 16 matrix with 20 seconds of stop. Redistribution images were obtained 4 hours later. Number, location, and degree of reversibility of defects was reported. Plasma samples for measurements of malonaldehyde (MDA), a marker of lipid peroxidation, were obtained immediately prior to and following completion of the exercise stress test. These samples were submitted in a blind manner and duplicate analyses were performed to determine the extent of lipid peroxidation as thiobarbituric reactive substances. 6 Results of duplicate analyses were ± 8% by this method. Results
The exercise stress test results are shown in Table 1. Two-way ANOVA comparing plasma MDA levels pre-and post-exercise, shown in Table 2, revealed that plasma MDA levels did not differ between groups A and B before and after exercise. While there was significant inter-individual variation, a significant P = 0.002) directional difference in response to exercise was noted among the groups (ie, an exercise-induced increase in plasma MDA levels was observed in Group A but there was a decrease in plasma MDA levels in Group B patients). Paired t-test comparisons conducted for percent MDA changes between Group A and Group B subjects revealed significant differences. MDA change between Group A (46 ± 12.7%) and Group B (-16.8 ± 4.6%) patients P < 0.001). Spearman rank order correlation coefficients between changes in plasma MDA levels and duration of exercise, percent maximal predicted heart rate, and peak rate-pressure product (r = -0.18, -0.05, and -0.12 respectively) were not significant. Patients were classified according to positive or negative changes in plasma MDA levels. Plasma MDA levels after exercise were unchanged in 2 patients. Of those patients who developed increased MDA levels with ex186
ercise (n = 7), all but 1 had at least 1 reversible thallium defect. Among patients with decreased plasma MDA levels (n = 9), 8 had no observable thallium defects and 1 had a mixed (1 reversible and 1 fixed area of decreased perfusion) defect. Discussion
This study did not attempt to differentiate whether or not the increased levels of exercise-induced oxidative stress among those patients with positive thallium stress tests (one thallium defect or more) is attributable to the presence of atherosclerosis in this group, to increased innate level of susceptibility to oxidative stress, or to the effects of exercise-induced myocardial ischemia and reperfusion. However, it is noted that all 8 subjects with exerciseinduced increases in plasma MDA levels had ischemia by exercise-thallium testing (completed In = 71 or partial [n = IJ reversibility of thallium defects), suggesting that exercise-induced oxidative stress is related to ischemia and reperfusion. The source of
Table 2. Exercise-Induced Changes in Plasma Malonaldehyde (MDA) Levels Compared Between Patients with Positive (Group Al and Negative (Group Bl Thallium Stress Tests"
Subject
Preexercise MDA
Postexercise MDA
Group A (N
8)
=
-18'Yr +1480/,. +72'Yr +31% + 83'7c + 48'Yr. +53% +34'Yr
1 3 5 6 7 10 11 14
5.0 5.6 2.6 4.9 1.8 3.3 2.1 2.3
4.1 13.9 4.9 6.4 3.3 4.9 3.2 3.1
Mean ± SD
3.45 ± 1.50
5.4 7 ± 1.02t
Group B (N 2 4 8 9 12 13 15 16 17 18
5.0 6.4 4.1 4.9 6.6 5.7 5.8 6.4 3.9 4.2
Mean:+: SD
5.30 :+: 1.02
=
Percent Change
+46:+: 12.7%:j:
10) -18% -23% -20% -33% -14% -33% -14% -47% -36% 0%
4.1 4.9 3.3 3.3 5.7 3.8 5.0 3.4 2.5 4.2 4.07 :+: 0.96
* Using two-way ANOVA (serum MDA
=
-16.8 :+: 4.6%
nanomolesI mL). (P = 0.002,
t MDA in response to exercise significantly different
F value = 13.63). :j: Paired t-test comparison of MDA percent change between groups is significant (P < 0.0001). March 1998 Volume 315 Number 3
Leaf et 01
exercise-induced lipid peroxidation is uncertain, and could be related to regional (ie, myocardial) or global (ie, other body tissues) oxidative stress. Further study of this might include analysis of MDA levels from blood reflecting myocardial blood flow, such as the coronary sinus. Another possibility, requiring evaluation with longitudinal studies, is that exercise-induced increases in plasma MDA levels are an a priori predictor of 'chose who develop exercise-induced ischemia. The interpretation of these findings is limited by the relatively small number of patients and the high prevalence of men studied. In a previous study of healthy young athletes, we found although some markers of lipid peroxidation (expired ethane and pentane) increased during maximal exercise stress testing, plasma MDA levels did not increase. 7 Plasma MDA levels were not measured during the course of exercise; hence we cannot exclude the possibility of MDA redistribution occurring from serum to tissue membranes during exercise, nor the effect of endogenous antioxidant systems in the healthy individuals and in Group B subjects. A limitation comparing these findings with our previous findings and those of others stems from differences in exercise protocols and the timing of MDA sampling. Another limitation is the potential lack of specificity of the use of the thiobarbituric acid (TBA) assay as a determinant of plasma MDA. 8 The repeated measures used in this study, however, enabled us to observe that there are population-derived response differences. Marked differences in exercise-related changes in plasma MDA levels between those with and without
THE AMERICAN JOURNAL OF THE MEDICAL SCIENCES
exercise-induced ischemia are noted, which may have implications in the development of adjuncts to diagnostic exercise stress testing. Acknowledgements
This project was funded by the American Heart Association (Greater Los Angeles Affiliate), Grant Award No. 991 GI-2, and is part of programs supported by the University of California Irvine Center for Occupational and Environmental Health. References 1. Steinberg D, Parthsarathy S, Carew TE, Khoo JC, Wit-
2.
3. 4.
5. 6. 7. 8.
zum JL. Beyond cholesterol: modifications oflow-density lipoprotein that increase its atherogenicity. N Engl J Med. 1989; 320:915-24. De Scheerder IK, Van de Kraay AMM, Lamers JMJ, Koster JF, de Jong JW, Serruys PW. Myocardial malonaldehyde and uric acid release after short-term coronary occlusion during coronary angioplasty: potential mechanisms of free radical generation. Am J Cardiol. 1991;68:392-5. Davies SW, Ranjadayalan K, Wickens DG, Dormandy TL, Timmis AD. Lipid peroxidation associated with successful thrombolysis. Lancet. 1990;335:741-3. Roberts MJD, Young IS, Trouton TG, Trimble ER, Khan MM, Webb SW, et al. Transient release of lipid peroxides after coronary artery balloon angioplasty. Lancet. 1990; 336:143-5. Li JJ. Exercise and oxidative stress: role ofthe cellular antioxidant systems. Exerc 8ports 8ci Rev. 1995;23:135-6. Esterbauer H, Cheeseman KH. Determination of aldehydic lipid peroxidation products: malonaldehyde and 4-hydroxynonenal. Methods Enzymol. 1990; 186:504-8. Leaf DA, Kleinman MT, Hamilton M, Barstow TJ. The effect of exercise intensity on lipid peroxidation. Med 8ci 8ports Exerc. 1997;29(8):1036-9. Bowen PE, Mobarhan S. Evidence from cancer intervention and biomarker studies and the development ofbiochemical markers. Am J Clin Nutr. 1995;62(8):14038-14098.
187