- Email: [email protected]
Chest pain is an unreliable measure of ischemia in men and women during PTCA
Chest pain is an u n r e l i a b l e m e a s u r e of i s c h e m i a in m e n a n d w o m e n during PTCA M a r y A. C a l d w e l l , RN, MS, M B A , M i c h e l e M. Pelter, RN, MS, a n d B a r b a r a J. D r e w , RN, P h D , F A A N , S a n F r a n c i s c o , Calif.
OBJECTIVE: To investigate the differences between m e n and w o m e n in ischemia-induced pain, the a m o u n t of ST-segment deviation (the "ST deviation score"), and the relation between pain intensity and ST deviation score. D E S I G N : Retrospective, comparative descriptive.
SETTING: Cardiac catheterization laboratory of a large, urban, university-affiliated medical Center with full cardiac services, PATIENTS: Adults who u n d e r w e n t percutaneous transluminal coronary angioplasty (PTCA) and had
electrocardiographic (ECG) evidence of myocardial ischemia during balloon inflation. M E T H O D S : Continuous 12-lead ECGs were recorded during balloon inflation in patients undergoing
PTCA. Patients rated pain on a scale of 0 to 10. The total ST deviation score equaled baseline ECG ST minus maximal ST deviation; absolute deviations were totaled. Frequencies, measures of central tendency, or chi-square or t tests were used for data analysis with significance established at p < 0.05. RESULTS: There was no difference in the degree of chest pain between m e n and w o m e n during balloon inflation, nor was ST deviation score associated with pain in either gender. Pain intensity did not correlate with total ST deviation in m e n (r = 0.02) or w o m e n (r = -0.07). CONCLUSIONS: In this study, pain was a poor indicator of ischemia in both sexes during PTCA, and the degree of pain did not correlate with the magnitude of ST deviation. More than one third of m e n and more than one fourth of w o m e n experienced no chest pain during balloon inflation. Clinicians should consider continuous ST-segment monitoring and patient symptoms to monitor accurately for ischemia. (Heart Lung | 1996;25:423-9.)
imely recognition of myocardial ischemia is critical in protecting and saving myocardial muscle cells. Angina is the symptom most associated with myocardial ischemia ~ However, the use of pain as a diagnostic tool is problematic. Among other things, chest pain is a highly individual, subjective experience that is influenced by a person's intelligence, education, and social
T
From the Department of Physiological Nursing, School of Nursing, Universityof California, San Francisco. Conducted as part of a largerstudy funded by grant RO1NR03435 from the National Institute of Nursing Research, National Institutes of Health. Reprint requests: Mary A. Caldwell, RN, 776 Green St., San Francisco, CA 94133 Copyright 9 1996by Mosby-YearBook, Inc. 0147-9563/06/$5.00 + 0 2/1/76444 HEART & L U N G VOL 25, NO. 6
and cultural background. 2 Pain can be modified by narcotic drugs and analgesic drugs and can be provoked by anxiety. Many other clinical syndromes can mimic angina. Gender may also influence the pain experience. Angina is the major presenting symptom in women with coronary artery disease, whereas myocardial infarction (MI) is the primary presenting condition in men. 3 Research indicates that women with cardiovascular disease receive diagnoses later and are treated less aggressively than are men. 4,5 Women tend to have chest pain that is more atypical than that of men; women!s different socialization may influence the way they experience and describe pain. 6,7 In addition, women's presentation patterns of MI may be dif423
ferent, a There may also be physiologic distinctions that explain differences in angina. For example, syndrome X--a clinical pattern of angina, positive results on exercise treadmill tests, and normal coronary arteries on angiography--is more often associated with women and is thought to be due to microvascular rather than epicardial obstructions. 9 The degree of chest pain may not necessarily be associated with the amount of ischemic myocardium. Studies examining silent and symptomatic ischemia have suggested that symptomatic ischemia is associated with a greater mass of ischemic myocardium, lo, l I However, other work has contradicted that conclusion. 12 PURPOSE
The purpose of this study was to investigate the differences between men and women in ischemia-induced pain, the amount of ST-segment deviation (the "ST deviation score"), and the relation between pain intensity and ST deviation score in patients with ischemia during percutaneous transluminal coronary angioplasty (PTCA) balloon inflation. Questions researched were as follows: (I) Do more women than men report angina? (2) Among persons with angina, do women report a greater degree of pain than do men? (3) Is pain a better indicator of ischemia in men than in women? METHODS
This study applied a comparative descriptive design. It involved a secondary analysis of data collected in an ongoing prospective research project, "Nursing Strategy for Cardiac Ischemia Monitoring" (National institute of Nursing Research, RO1NR03435) that is investigating the value of continuous i2-1ead electrocardiograms (ECG) for detecting myocardial ischemia in patients in the coronary care unit and the catheterization laboratory during PTCA.13 Sample and setting. A convenience sample of cognizant, consenting patients who understood English well enough to answer the pain identification question and who underwent PTCA with a nonperfusion balloon were considered for the study. Patients with left bundle branch block or ventricular paced rhythm were excluded because of the difficulty in interpreting ST-segment changes. Also excluded were patients previously enrolled in the parent study who were undergoing a repeated PTCA. For patients in whom more than one vessel was dilated, the vessel with the largest ST-segment deviation was selected. Upon bal424
loon inflation, evidence of ischemia was considered to be 1 mm or more of ST-segment deviation in at least one lead. Deviation of 1 mm or more has been described by others as representing the minimum threshold for detection of ischemia, j4 Data were collected in the cardiac catheterization laboratory of a large, urban, university-affiliated medical center with full cardiac services. Instruments. Continuous 12-lead EGG rhythm strips were recorded during PTCA with a HewlettPackard Pagewriter XLI Cardiograph (McMinnville, Ore.). The paper speed was 25 mm/sec; filter settings were 0.05 to 109 Hz; and standard calibration was 10 mm/mV, as recommended by the American Heart Association. 15 Verbal feedback regarding chest pain was elicited from patients during balloon inflation by using the Numeric Rating Scale of Pain Intensity (NRS). Patients were asked, "On a scale of 0 to 10, with 0 being no pain and 10 being the worst pain you could imagine, how much pain are you having?" The pain described had to be considered classic angina or anginal equivalent. The pain was considered ischemic in origin if it appeared concurrently with balloon inflation and disappeared with deflation. Pain related to the procedure itself (e.g., groin or incisional pain or positional discomfort) was not rated. Because pain is a dynamic phenomenon, the reliability of pain rating scales has been difficult to establish. However, descriptive numeric rating scales have been found to be valid and reproducible measures of pain intensity. 16-18 ST deviation score. The ST deviation score was used as a representation of the total ischemia experienced by the patient at a given moment. The following methods were used to calculate these scores. When there were multiple inflations, the inflation with the maximum ST devia~ tion was analyzed. The measurements were determined at end-inflation. The T-P segment of the ECG served as the isoelectric line for ST-segment deviation scores. ST segments were measured at 80 msec from the J point (the junction marking the end of the QRS complex and the beginning of the ST segment) during the baseline state before balloon inflation and again at endinflation when maximal ischemia was present. Absolute deviations (in millimeters) were calculated and totaled for all 12 leads to produce the ST deviation score. The concept of using 12 ECG leads to measure ischemic burden during balloon inflation has only recently been introduced. Various studies have used different formulas for calculating the total ST NOVEMBER/DECEMBER1996 HEART & LUNG
Table I Characteristics of subjects (n = 68) M e n (n = 42) Age (yr) Mean Range Diagnosis Unstable angina MI Congestive heart failure Balloon inflation time (sec) Mean Median Mode Vessel dilated Left anterior descending Right coronary Left circumflex
W o m e n (n = 26)
p Value
62.3 41-85
65.6 26-88
NS
37 (88%) 4 (10%) 1 (2.4%)
25 (96%) 1 (4%) 0 (0%)
NS
107.25 90 90
95.2 90 90
NS
13 (31%) 15 (36%) 14 (33%)
14 (54%) 7 (27%) 5 (19%)
NS
NS, Differencenot significant.
deviation or ischemic burden, depending on the emphasis of the study. 19"25 For example, researchers have used the sum of deviations over all 12 leads, 11 leads without the aVR lead, or leads specific to a region of myocardium. Because ischemia during balloon inflation produces segmental (rather than global) ischemia, it was considered important in this study to use deviations in all 12 leads to capture the maximum amount of information regarding ECG changes. Data collection. Female research assistants specifically trained in patient preparation, electrode placement, and e q u i p m e n t monitoring ensured consistency among ECG tracings, as described previously. 13 The research assistants also were trained for consistency in asking the NRS question on pain. Patient responses were recorded directly on ECG recordings by research assistants or on a standardized PTCA information form. Statistical analysis. The statistical software program CRUNCH (Crunch Software Corporation, 1992) was used to analyze the data. Sample characteristics were analyzed using frequencies, measures of central tendency, or chi-square or t tests as appropriate. Chi-square analysis was used to analyze whether more women than men reported anginal pain. To examine whether women reported a greater degree of pain than did men, t tests were used. The t test was also used to determine whether there were differences between men and HEART & LUNG VOL. 25, NO. 6
women in the presence and intensity of chest pain and ST deviation score. The Pearson product moment correlation coefficient was used to test whether there was a relation between pain intensity and ST deviation score. Significance was established at p < 0.05. RESULTS
Table I describes the characteristics of the patients by gender. Of the 68 patients who met the inclusion criteria, 42 (62%) were men; the patients' mean age was 63.5 years (range 26 to 88 years). A majority (62 [91%1) of the patients had a diagnosis of unstable angina; 5 (7%) had acute MI; and 1 (2%) had coronary artery disease with congestive heart failure. In addition, 23 (34%) of patients had diabetes as a coexisting condition. There were no statistically significant differences between men and women in any of these variables. The mean balloon inflation time was 103 seconds (range 30 to 300 seconds). The left anterior descending artery was dilated in 40% of patients; the right coronary artery in 32%; and the circumflex in 28%. In 40%, the maximum deviation occurred during the first inflation, 31% during the second inflation, 19% during the third, and the remaining 10% during one of the fourth through eleventh inflations. There were no statistically significant differences between men and women 425
Table II Presence and intensity of p a i n in m e n a n d w o m e n w i t h ECG evidence of myocardial ischemia during PTCA Men
No pain M e a n pain intensity (0-10) SD
M e a n ST deviation scores
Women
(n -- 42)
(n = 26)
p Value
35.7% 5.4
26.9% 6
NS NS
3.2
2.8
NS, Difference not significant.
with respect to balloon inflation time or the artery dilated. Thirty-two percent of the study patients were asymptomatic during balloon inflation despite ST-segment changes indicating ischemia. Although a slightly lower proportion of women (27%) experienced silent ischemia than men (36%), this difference was not statistically significant (Table 11). In addition, men and women appeared to experience pain with similar intensity (NRS = 5.4 and 6.0, respectively). The mean ST deviation score was 13.3 (SD 8.1) for men and 14.5 (SD 8.4) for women; this difference was not statistically significant. The magnitude of ST deviation was not greater in men and women who experienced pain compared with those who were asymptomatic (Table 11I). However, men with pain had a tendency to exhibit greater ST deviation than men without pain, but this difference was not statistically significant. This trend was not observed in women. In fact, women without pain tended to exhibit a higher ST deviation score than did women with pain (but the difference was not statistically significant). When the entire group was examined, there was no relation between pain intensity and the amount of ischemic myocardium (r = -0.01) (Figure 1). Likewise, there was no correlation when men (r = 0.021 and women (r = -0.07) were examined separately (Figures 2 and 3, respectively).
DISCUSSION The results of the current study indicate that women and men have similar experiences with respect to angina and ST deviation during balloon inflation-induced ischemia. Women experienced angina with ischemia at a frequency similar to that 426
Table III Relation b e t w e e n pain a n d ST deviation by gender
Men
(n = 42) Pain No pain
14.7 10.9 NS
Women
(n = 26) i4.2 15.2 NS
p Value NS NS
NS, Difference not significant.
of men. The converse situation also is noteworthy: 27% of the women and 36% of men had no chest pain despite obvious ST-segment changes during balloon inflation. When pain was present, it was felt with the same intensity. In the absence of pain, the differences in ischemic burden between genders also were not significant. In both men and women, there was no correlation between ST deviation and pain intensity. Pain resulting from ischemic heart disease is a symptom that is well known to all clinicians and is relied upon as an indicator of ischemia. At one point in the evolution of the diagnosis of cardiovascular disease, angina and coronary artery disease were synonymous. However, the mechanisms underlying cardiac pain and its relation to ischemia are poorly understood, and the results of research in this area are conflicting. 1~ These studies primarily have analyzed symptoms during exercise-induced ischemia and have measured ST-segment changes from ambulatory recordings. The current study examined controlled inflation-induced ischemia recorded by continuous 12-lead ECG. This setting also allowed quantitative measurements of pain intensity during periods of documented ischemia. Some studies have linked the presence of angina with a more ischemic myocardium,! ~,27but the current study does not support that contention. Patients with pain had similar amounts of ST deviation as did those without pain. There was no statistically significant difference between the total ST deviation score for those with silent ischemia and those with symptomatic ischemia in the group as a whole or in men and women as subgroups. Of particular interest was the examination of gender differences because it has been suggestNOVEMBER/DECEMBER 1996 HEART & LUNG
...........
10
-- .......
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9
9
.,~
~. . . . . .
9 r = -.01
8 7 6 r
== Z-
5 4 3
9
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41~
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1 0
~
0
10
20
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30
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T o t a l ST s c o r e ( m m )
F i g . 1 P a i n i n t e n s i t y v s ST d e v i a t i o n s c o r e i n e n t i r e g r o u p (n = 68); r = -0.01.
10 9
r = .02
8 7 6 5 4 3 2 1 0
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T o t a l ST s c o r e (mm)
F i g . 2 P a i n i n t e n s i t y v s ST d e v i a t i o n s c o r e i n m e n (n = 4 2 ) ; r = 0 . 0 2 .
1C 9 E
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T o t a l ST s c o r e (ram)
F i g . 3 P a i n i n t e n s i t y v s ST d e v i a t i o n r = -0.07.
HEART & LUNG
VOL. 25, NO. 6
score in women
(n = 2 6 ) ;
427
ed that women experience pain more often or differently than men. 6,7 Qualitative studies have described women's underreporting of pain for several reasons. Women typically describe their cardiac symptoms, in the office or in the emergency department, to a male physician. Some women's communication styles are different d e p e n d i n g on whether they are talking with a male or a female physician, and this difference may affect the way in which women's pain is reported or interpreted. 2s,29 That the physician is a man and that he is considered the "expert" may place some women in a potentially intimidating situation that can jeopardize their ability to convey their symptoms accurately. 6 In another regard, women have also been described as "complainers" whose statements may be taken less seriously than those of men. Their symptoms have been dismissed as psychosomatic, overemotional, or "all in the head." This s t u d y appeared not to support these suggestions of underreporting in women. In a study examining patterns of chest pain in patients hospitalized for MI, pain was assessed according to requirement for narcotic medications, the estimated duration of pain, the number of pain attacks, and the occurrence of pain later than 24 hours after admission. 3~ Although there was great variability in the findings, women required less pain medication, a result implying that women experienced less pain. This finding is limited, h o w e v e r , because the number of requests for pain medication is a highly individualistic variable that is not necessarily indicative of the pain experience. Other factors such as a higher tolerance for pain or a staff reluctance to medicate women adequately may also have influenced the findings. Physiologic theory of myocardial ischemia also supports p o t e n t i a l gender differences with respect to pain and ischemic burden. Syndrome X is more prevalent in women and is associated with disorders of the microvasculature, as opposed to epicardial arteries. 29,3~ In addition, estrogen appears to have a vasodilatory affect on the coronary arteries in women, a benefit not accorded to men. 3~,32 Researchers have noted that the sum of STsegment deviations on admission tended to be higher (though not s t a t i s t i c a l l y ) i n men than in women for patients admitted with a possibility of MI. 21 It also has been noted that during angioplasty, men have more pronounced maximum ST vector magnitude deviation during inflation when compared with women, 33 although this finding
428
tOO did not reach statistical significance. The results of the current analysis contradicts these findings: men and women had similar amounts of ST deviation during balloon inflation.
LIMITATIONS This study was performed under the controlled conditions that exist in the cardiac catheterization laboratory and therefore may not be generalizable to non-PTCA situations such as those that may occur in the home. Supply-related ischemia, seen during balloon inflation, may not produce the same kind of pain experience as that experienced in the critical care unit, the general ward, or the patient's home. In addition, demand-related ischemia may produce different pain patterns. Pain is a complex, individualized process and is exceedingly difficult to analyze and generalize, particularly in a stressful environment such as the catheterization laboratory. Although the NRS has been validated in several studies, 18 it is relatively rigid in its design, and information may have been lost by not allowing patients more freedom to describe their pain rather than give it a numerical rating. Future studies with larger study groups may help to determine whether pain is a better measure of ischemia in men than in women.
IMPLICATIONS The results of this analysis indicate that pain is a poor indicator of ischemia in both men and women during ischemia produced by balloon inflation during PTCA. In addition, pain does not appear to correlate with the amount of ischemic myocardium as measured by the total ST deviation score. Recurrent ischemia in the catheterization laboratory or in the coronary care unit may signal reocclusion of the operative artery, indicating an emergency. Rapid assessment and diagnosis at the bedside is imperative if myocardial damage is to be minimized. Clinicians who monitor and diagnose potential ischemia, particularly in situations such as the postangioplasty period, should not rely on angina alone as a diagnostic tool. Other bedside methods, such as continuous ST-segment monitoring, may aid in the detection of ischemia and ischemic burden and should be considered. REFERENCES
1. West CM. Ischemia. In: Carrieri-KohlmanV, Lindsey AM, West CM, editors. Pathophysiologicalphenomenain nursing: human responses to illness. Philadelphia: WB Saunders, 1993:13-49.
NOVEMBER/DECEMBER 1996 HEART & LUNG
2. O'Rourke RA. Chest pain. In: Schlant RC, Alexander RW, editors. The heart: arteries and veins. New York: McGraw-Hill, 1994:459-67. 3. Lerner DJ, Kannel WB. Patterns of coronary heart disease morbidity and mortality in the sexes: a 26-year follow-up of the Framingham population. Am Heart J 1986;l 1 l:383-90. 4. Ayanian JZ, Epstein AM. Differences in the use of procedures between women and men hospitalized for coronary heart disease. N Engl I Med 1991;325:221-5. 5. Steingart RM, Packer M, Harem P, Coglianese ME, Gersh B, Geltman EM, et al, and Survival and Ventricular Enlargement Investigators. Sex differences in the management of coronary artery disease. N Engl J Med 1991;325:226-30. 6. Fisher S. In the patient's best interest: women and the politics of medical decisions. New Brunswick (N/): Rutgers University Press, 1988:59-85. 7. Todd AD. Intimate adversaries: cultural conflict between doctors and patients. Bloomington: Indiana University Press, 1989:32-6. 8. Weisberg MC, Rankin SH, Denham DA, Carlson NG, Dukes MA. Women's MI presentation patterns [abstract]. Commun Nurs Res 1994;27:318. 9. Kemp HG Jr. Syndrome X revisited. J Am Coil Cardio] 1991;17:507-8. 10. Bandu L, Friedman HS, Raggi P, Fishman S, Prasada S, Sacchi T, et ah Symptoms of patients with silent ischemia as detected by thallium stress testing. Chest 1994; 105:100912 11. Travin MI, Flores AR, Bouther CA, Newell JB, LaRaia PJ. Silent versus symptomatic ischemia during a thallium-201 exercise test. Am J Cardiol 1991;68:1600-8. 12. Klein J, Chao SU, Berman DS, Rozanski A. Is "silent" myocardial ischemia really as severe as symptomatic ischemia? The analytical effect of patient selection biases. Circulation 1994;89:1958-66. 13. Drew B J, Adams MA, Pelter MM, Wung S. ST segment monitoring with a derived 12-lead electrocardiogram is superior to routine CCU monitoring. Am ] Crit Care 1996;5:198206. 14. Krucoff MW, Pope JE, Bottner RK, Renzi RH, Wagner GS, Kent KM, et al. Computer*assisted ST-segment monitoring: experience during and after brief coronary occlusion. ] Electrocardiol 1987;20(Suppl):l 5-2 l. 15. Mirvis DM, Berson AS, Goldberger AL, Green LS, Heger JJ, Hinohara T, et al. Instrumentation and practice standards for electrocardiographic monitoring in special care units: a report for health professionals by a Task Force of the Council on Clinical Cardiology, American Heart Association. Circulation 1989;79:464-71. 16. Downie WW, Leatham PA, Rhind VM, Wright V, Branco ]A, Anderson JA, et al. Studies with pain rating scales. Ann Rheum Dis 1978;37:378-8l. 17. Huskisson EC. Measurement of pain. Lancet 1974;2:112731. 18. Ohnhaus EE, Adler R. Methodological problems in the measurement of pain: a comparison between the verbal rating scale and the visual analogue scale. Pain 1975;1:379-84.
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19. Aldrich HR, Wagner NB, Boswick J, Corsa AT, Jones MG, Grande P, et al. Use of initial ST-segment deviation for prediction of final electrocardiographic size of acute myocardial infarcts. Am I Cardiol 1988i61:749-53. 20. Weyne AE, DeBuyzere ML, Bauwens FR, Clement DL. Assessment of myocardial ischemia by 12-lead electro* cardiography and Frank recto system during coronary angioplasty: value of a new orthogonal lead system for quantitative ST segment monitoring. J Am Coll Cardiol 1991;18:1704-10. 21. Raitt MH, Litwin PF, Martin JS, Weaver WD. ECG findings in acute myocardial infarction: are there sex differences? J Electrocardiol 1995;28:13-6. 22. Schroder R, Dissmann R, Bruggemann T, Wegscheider K, Linderer T, Tebbe U, et al. Extent of early ST segment elevation resolution: a simple but strong predictor of outcome in patients with acute myocardial infarction. J Am Coil Cardiol 1994;24:384-91. 23. Tomai E Crea F, Gaspardone A, Versaci F, Esposito C, Chiariello L, et al. Mechanisms of cardiac pain during coronary angioplasty. J Am Coil Cardiol 1993;22:1892-6. 24. Wong CK, Freedman SB. Usefulness of continuous ST monitorin~ in inferior wall acute myocardial infarction for describing the relation between precordial ST depression and inferior ST elevation. Am J Cardiol 1993;72:532-7. 25. Cohen M, Scharpf SJ, Rentrop KP Prospective analysis of electrocardiographic variables as markers for extent and location of acute wall motion abnormalities observed during coronary angioplasty in human subjects. I Am Coll Cardiol 1987;10:17-24. 26. Maseri A, ChierchJa S, Davies G, Glazier I. Mechanisms of ischemic cardiac pain and silent myocardial ischemia. Am J Med 1985;79(Suppl 3A):7-I I. 27. Nihoyannopoulos P, Marsonis A, loshi J, Athanassopoulos G, Oakley CM. Magnitude of myocardial dysfunction is greater in painful than in painless myocardial ischemia: an exercise echocardiographic study. J Am Coil Cardiol 1995;25:1507-12. 28. Karlson BW, Sjolin M, Herlitz h Clinical factors associated with pain in acute myocardial infarction. Cardiology 1993;83:107-17. 29. Reaven GM Syndrome X: is one enough? [editorial]. Am Heart J 1994;I27:1439-42. 30. Cannon RO. The sensitive heart: a syndrome of abnormal cardiac pain perception. JAMA 1995;273:883-7. 31. Gilligan DM, Ouyyumi AA, Cannon RO. Effects of physiological levels of estrogen on coronary vasomotor function in postmenopausal women. Circulation 1994;89:2545-51. 32. Sarrel PM, Lindsay D, Rosano GM, Poole-Wilson PA. Angina and normal coronary arteries in women: gynecologic findings. Am J Obstet Gynecol 1992; 167:467-71. 33. Dellborg M, Herlitz J, Emanuelsson H, Swedberg K. ECG changes during myocardial ischemia: differences between men and women, l Electrocardiol 1994;27(Suppl):42-5.
429
OBJECTIVE: To investigate the differences between m e n and w o m e n in ischemia-induced pain, the a m o u n t of ST-segment deviation (the "ST deviation score"), and the relation between pain intensity and ST deviation score. D E S I G N : Retrospective, comparative descriptive.
SETTING: Cardiac catheterization laboratory of a large, urban, university-affiliated medical Center with full cardiac services, PATIENTS: Adults who u n d e r w e n t percutaneous transluminal coronary angioplasty (PTCA) and had
electrocardiographic (ECG) evidence of myocardial ischemia during balloon inflation. M E T H O D S : Continuous 12-lead ECGs were recorded during balloon inflation in patients undergoing
PTCA. Patients rated pain on a scale of 0 to 10. The total ST deviation score equaled baseline ECG ST minus maximal ST deviation; absolute deviations were totaled. Frequencies, measures of central tendency, or chi-square or t tests were used for data analysis with significance established at p < 0.05. RESULTS: There was no difference in the degree of chest pain between m e n and w o m e n during balloon inflation, nor was ST deviation score associated with pain in either gender. Pain intensity did not correlate with total ST deviation in m e n (r = 0.02) or w o m e n (r = -0.07). CONCLUSIONS: In this study, pain was a poor indicator of ischemia in both sexes during PTCA, and the degree of pain did not correlate with the magnitude of ST deviation. More than one third of m e n and more than one fourth of w o m e n experienced no chest pain during balloon inflation. Clinicians should consider continuous ST-segment monitoring and patient symptoms to monitor accurately for ischemia. (Heart Lung | 1996;25:423-9.)
imely recognition of myocardial ischemia is critical in protecting and saving myocardial muscle cells. Angina is the symptom most associated with myocardial ischemia ~ However, the use of pain as a diagnostic tool is problematic. Among other things, chest pain is a highly individual, subjective experience that is influenced by a person's intelligence, education, and social
T
From the Department of Physiological Nursing, School of Nursing, Universityof California, San Francisco. Conducted as part of a largerstudy funded by grant RO1NR03435 from the National Institute of Nursing Research, National Institutes of Health. Reprint requests: Mary A. Caldwell, RN, 776 Green St., San Francisco, CA 94133 Copyright 9 1996by Mosby-YearBook, Inc. 0147-9563/06/$5.00 + 0 2/1/76444 HEART & L U N G VOL 25, NO. 6
and cultural background. 2 Pain can be modified by narcotic drugs and analgesic drugs and can be provoked by anxiety. Many other clinical syndromes can mimic angina. Gender may also influence the pain experience. Angina is the major presenting symptom in women with coronary artery disease, whereas myocardial infarction (MI) is the primary presenting condition in men. 3 Research indicates that women with cardiovascular disease receive diagnoses later and are treated less aggressively than are men. 4,5 Women tend to have chest pain that is more atypical than that of men; women!s different socialization may influence the way they experience and describe pain. 6,7 In addition, women's presentation patterns of MI may be dif423
ferent, a There may also be physiologic distinctions that explain differences in angina. For example, syndrome X--a clinical pattern of angina, positive results on exercise treadmill tests, and normal coronary arteries on angiography--is more often associated with women and is thought to be due to microvascular rather than epicardial obstructions. 9 The degree of chest pain may not necessarily be associated with the amount of ischemic myocardium. Studies examining silent and symptomatic ischemia have suggested that symptomatic ischemia is associated with a greater mass of ischemic myocardium, lo, l I However, other work has contradicted that conclusion. 12 PURPOSE
The purpose of this study was to investigate the differences between men and women in ischemia-induced pain, the amount of ST-segment deviation (the "ST deviation score"), and the relation between pain intensity and ST deviation score in patients with ischemia during percutaneous transluminal coronary angioplasty (PTCA) balloon inflation. Questions researched were as follows: (I) Do more women than men report angina? (2) Among persons with angina, do women report a greater degree of pain than do men? (3) Is pain a better indicator of ischemia in men than in women? METHODS
This study applied a comparative descriptive design. It involved a secondary analysis of data collected in an ongoing prospective research project, "Nursing Strategy for Cardiac Ischemia Monitoring" (National institute of Nursing Research, RO1NR03435) that is investigating the value of continuous i2-1ead electrocardiograms (ECG) for detecting myocardial ischemia in patients in the coronary care unit and the catheterization laboratory during PTCA.13 Sample and setting. A convenience sample of cognizant, consenting patients who understood English well enough to answer the pain identification question and who underwent PTCA with a nonperfusion balloon were considered for the study. Patients with left bundle branch block or ventricular paced rhythm were excluded because of the difficulty in interpreting ST-segment changes. Also excluded were patients previously enrolled in the parent study who were undergoing a repeated PTCA. For patients in whom more than one vessel was dilated, the vessel with the largest ST-segment deviation was selected. Upon bal424
loon inflation, evidence of ischemia was considered to be 1 mm or more of ST-segment deviation in at least one lead. Deviation of 1 mm or more has been described by others as representing the minimum threshold for detection of ischemia, j4 Data were collected in the cardiac catheterization laboratory of a large, urban, university-affiliated medical center with full cardiac services. Instruments. Continuous 12-lead EGG rhythm strips were recorded during PTCA with a HewlettPackard Pagewriter XLI Cardiograph (McMinnville, Ore.). The paper speed was 25 mm/sec; filter settings were 0.05 to 109 Hz; and standard calibration was 10 mm/mV, as recommended by the American Heart Association. 15 Verbal feedback regarding chest pain was elicited from patients during balloon inflation by using the Numeric Rating Scale of Pain Intensity (NRS). Patients were asked, "On a scale of 0 to 10, with 0 being no pain and 10 being the worst pain you could imagine, how much pain are you having?" The pain described had to be considered classic angina or anginal equivalent. The pain was considered ischemic in origin if it appeared concurrently with balloon inflation and disappeared with deflation. Pain related to the procedure itself (e.g., groin or incisional pain or positional discomfort) was not rated. Because pain is a dynamic phenomenon, the reliability of pain rating scales has been difficult to establish. However, descriptive numeric rating scales have been found to be valid and reproducible measures of pain intensity. 16-18 ST deviation score. The ST deviation score was used as a representation of the total ischemia experienced by the patient at a given moment. The following methods were used to calculate these scores. When there were multiple inflations, the inflation with the maximum ST devia~ tion was analyzed. The measurements were determined at end-inflation. The T-P segment of the ECG served as the isoelectric line for ST-segment deviation scores. ST segments were measured at 80 msec from the J point (the junction marking the end of the QRS complex and the beginning of the ST segment) during the baseline state before balloon inflation and again at endinflation when maximal ischemia was present. Absolute deviations (in millimeters) were calculated and totaled for all 12 leads to produce the ST deviation score. The concept of using 12 ECG leads to measure ischemic burden during balloon inflation has only recently been introduced. Various studies have used different formulas for calculating the total ST NOVEMBER/DECEMBER1996 HEART & LUNG
Table I Characteristics of subjects (n = 68) M e n (n = 42) Age (yr) Mean Range Diagnosis Unstable angina MI Congestive heart failure Balloon inflation time (sec) Mean Median Mode Vessel dilated Left anterior descending Right coronary Left circumflex
W o m e n (n = 26)
p Value
62.3 41-85
65.6 26-88
NS
37 (88%) 4 (10%) 1 (2.4%)
25 (96%) 1 (4%) 0 (0%)
NS
107.25 90 90
95.2 90 90
NS
13 (31%) 15 (36%) 14 (33%)
14 (54%) 7 (27%) 5 (19%)
NS
NS, Differencenot significant.
deviation or ischemic burden, depending on the emphasis of the study. 19"25 For example, researchers have used the sum of deviations over all 12 leads, 11 leads without the aVR lead, or leads specific to a region of myocardium. Because ischemia during balloon inflation produces segmental (rather than global) ischemia, it was considered important in this study to use deviations in all 12 leads to capture the maximum amount of information regarding ECG changes. Data collection. Female research assistants specifically trained in patient preparation, electrode placement, and e q u i p m e n t monitoring ensured consistency among ECG tracings, as described previously. 13 The research assistants also were trained for consistency in asking the NRS question on pain. Patient responses were recorded directly on ECG recordings by research assistants or on a standardized PTCA information form. Statistical analysis. The statistical software program CRUNCH (Crunch Software Corporation, 1992) was used to analyze the data. Sample characteristics were analyzed using frequencies, measures of central tendency, or chi-square or t tests as appropriate. Chi-square analysis was used to analyze whether more women than men reported anginal pain. To examine whether women reported a greater degree of pain than did men, t tests were used. The t test was also used to determine whether there were differences between men and HEART & LUNG VOL. 25, NO. 6
women in the presence and intensity of chest pain and ST deviation score. The Pearson product moment correlation coefficient was used to test whether there was a relation between pain intensity and ST deviation score. Significance was established at p < 0.05. RESULTS
Table I describes the characteristics of the patients by gender. Of the 68 patients who met the inclusion criteria, 42 (62%) were men; the patients' mean age was 63.5 years (range 26 to 88 years). A majority (62 [91%1) of the patients had a diagnosis of unstable angina; 5 (7%) had acute MI; and 1 (2%) had coronary artery disease with congestive heart failure. In addition, 23 (34%) of patients had diabetes as a coexisting condition. There were no statistically significant differences between men and women in any of these variables. The mean balloon inflation time was 103 seconds (range 30 to 300 seconds). The left anterior descending artery was dilated in 40% of patients; the right coronary artery in 32%; and the circumflex in 28%. In 40%, the maximum deviation occurred during the first inflation, 31% during the second inflation, 19% during the third, and the remaining 10% during one of the fourth through eleventh inflations. There were no statistically significant differences between men and women 425
Table II Presence and intensity of p a i n in m e n a n d w o m e n w i t h ECG evidence of myocardial ischemia during PTCA Men
No pain M e a n pain intensity (0-10) SD
M e a n ST deviation scores
Women
(n -- 42)
(n = 26)
p Value
35.7% 5.4
26.9% 6
NS NS
3.2
2.8
NS, Difference not significant.
with respect to balloon inflation time or the artery dilated. Thirty-two percent of the study patients were asymptomatic during balloon inflation despite ST-segment changes indicating ischemia. Although a slightly lower proportion of women (27%) experienced silent ischemia than men (36%), this difference was not statistically significant (Table 11). In addition, men and women appeared to experience pain with similar intensity (NRS = 5.4 and 6.0, respectively). The mean ST deviation score was 13.3 (SD 8.1) for men and 14.5 (SD 8.4) for women; this difference was not statistically significant. The magnitude of ST deviation was not greater in men and women who experienced pain compared with those who were asymptomatic (Table 11I). However, men with pain had a tendency to exhibit greater ST deviation than men without pain, but this difference was not statistically significant. This trend was not observed in women. In fact, women without pain tended to exhibit a higher ST deviation score than did women with pain (but the difference was not statistically significant). When the entire group was examined, there was no relation between pain intensity and the amount of ischemic myocardium (r = -0.01) (Figure 1). Likewise, there was no correlation when men (r = 0.021 and women (r = -0.07) were examined separately (Figures 2 and 3, respectively).
DISCUSSION The results of the current study indicate that women and men have similar experiences with respect to angina and ST deviation during balloon inflation-induced ischemia. Women experienced angina with ischemia at a frequency similar to that 426
Table III Relation b e t w e e n pain a n d ST deviation by gender
Men
(n = 42) Pain No pain
14.7 10.9 NS
Women
(n = 26) i4.2 15.2 NS
p Value NS NS
NS, Difference not significant.
of men. The converse situation also is noteworthy: 27% of the women and 36% of men had no chest pain despite obvious ST-segment changes during balloon inflation. When pain was present, it was felt with the same intensity. In the absence of pain, the differences in ischemic burden between genders also were not significant. In both men and women, there was no correlation between ST deviation and pain intensity. Pain resulting from ischemic heart disease is a symptom that is well known to all clinicians and is relied upon as an indicator of ischemia. At one point in the evolution of the diagnosis of cardiovascular disease, angina and coronary artery disease were synonymous. However, the mechanisms underlying cardiac pain and its relation to ischemia are poorly understood, and the results of research in this area are conflicting. 1~ These studies primarily have analyzed symptoms during exercise-induced ischemia and have measured ST-segment changes from ambulatory recordings. The current study examined controlled inflation-induced ischemia recorded by continuous 12-lead ECG. This setting also allowed quantitative measurements of pain intensity during periods of documented ischemia. Some studies have linked the presence of angina with a more ischemic myocardium,! ~,27but the current study does not support that contention. Patients with pain had similar amounts of ST deviation as did those without pain. There was no statistically significant difference between the total ST deviation score for those with silent ischemia and those with symptomatic ischemia in the group as a whole or in men and women as subgroups. Of particular interest was the examination of gender differences because it has been suggestNOVEMBER/DECEMBER 1996 HEART & LUNG
...........
10
-- .......
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9
9
.,~
~. . . . . .
9 r = -.01
8 7 6 r
== Z-
5 4 3
9
2
41~
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1 0
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0
10
20
v
v
30
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T o t a l ST s c o r e ( m m )
F i g . 1 P a i n i n t e n s i t y v s ST d e v i a t i o n s c o r e i n e n t i r e g r o u p (n = 68); r = -0.01.
10 9
r = .02
8 7 6 5 4 3 2 1 0
v
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v
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T o t a l ST s c o r e (mm)
F i g . 2 P a i n i n t e n s i t y v s ST d e v i a t i o n s c o r e i n m e n (n = 4 2 ) ; r = 0 . 0 2 .
1C 9 E
r = -.07
7 6 5 4 3 2 1 0 10
20
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T o t a l ST s c o r e (ram)
F i g . 3 P a i n i n t e n s i t y v s ST d e v i a t i o n r = -0.07.
HEART & LUNG
VOL. 25, NO. 6
score in women
(n = 2 6 ) ;
427
ed that women experience pain more often or differently than men. 6,7 Qualitative studies have described women's underreporting of pain for several reasons. Women typically describe their cardiac symptoms, in the office or in the emergency department, to a male physician. Some women's communication styles are different d e p e n d i n g on whether they are talking with a male or a female physician, and this difference may affect the way in which women's pain is reported or interpreted. 2s,29 That the physician is a man and that he is considered the "expert" may place some women in a potentially intimidating situation that can jeopardize their ability to convey their symptoms accurately. 6 In another regard, women have also been described as "complainers" whose statements may be taken less seriously than those of men. Their symptoms have been dismissed as psychosomatic, overemotional, or "all in the head." This s t u d y appeared not to support these suggestions of underreporting in women. In a study examining patterns of chest pain in patients hospitalized for MI, pain was assessed according to requirement for narcotic medications, the estimated duration of pain, the number of pain attacks, and the occurrence of pain later than 24 hours after admission. 3~ Although there was great variability in the findings, women required less pain medication, a result implying that women experienced less pain. This finding is limited, h o w e v e r , because the number of requests for pain medication is a highly individualistic variable that is not necessarily indicative of the pain experience. Other factors such as a higher tolerance for pain or a staff reluctance to medicate women adequately may also have influenced the findings. Physiologic theory of myocardial ischemia also supports p o t e n t i a l gender differences with respect to pain and ischemic burden. Syndrome X is more prevalent in women and is associated with disorders of the microvasculature, as opposed to epicardial arteries. 29,3~ In addition, estrogen appears to have a vasodilatory affect on the coronary arteries in women, a benefit not accorded to men. 3~,32 Researchers have noted that the sum of STsegment deviations on admission tended to be higher (though not s t a t i s t i c a l l y ) i n men than in women for patients admitted with a possibility of MI. 21 It also has been noted that during angioplasty, men have more pronounced maximum ST vector magnitude deviation during inflation when compared with women, 33 although this finding
428
tOO did not reach statistical significance. The results of the current analysis contradicts these findings: men and women had similar amounts of ST deviation during balloon inflation.
LIMITATIONS This study was performed under the controlled conditions that exist in the cardiac catheterization laboratory and therefore may not be generalizable to non-PTCA situations such as those that may occur in the home. Supply-related ischemia, seen during balloon inflation, may not produce the same kind of pain experience as that experienced in the critical care unit, the general ward, or the patient's home. In addition, demand-related ischemia may produce different pain patterns. Pain is a complex, individualized process and is exceedingly difficult to analyze and generalize, particularly in a stressful environment such as the catheterization laboratory. Although the NRS has been validated in several studies, 18 it is relatively rigid in its design, and information may have been lost by not allowing patients more freedom to describe their pain rather than give it a numerical rating. Future studies with larger study groups may help to determine whether pain is a better measure of ischemia in men than in women.
IMPLICATIONS The results of this analysis indicate that pain is a poor indicator of ischemia in both men and women during ischemia produced by balloon inflation during PTCA. In addition, pain does not appear to correlate with the amount of ischemic myocardium as measured by the total ST deviation score. Recurrent ischemia in the catheterization laboratory or in the coronary care unit may signal reocclusion of the operative artery, indicating an emergency. Rapid assessment and diagnosis at the bedside is imperative if myocardial damage is to be minimized. Clinicians who monitor and diagnose potential ischemia, particularly in situations such as the postangioplasty period, should not rely on angina alone as a diagnostic tool. Other bedside methods, such as continuous ST-segment monitoring, may aid in the detection of ischemia and ischemic burden and should be considered. REFERENCES
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