Psychological factors in silent myocardial ischemia

Psychological Factors in Silent Myocardial Ischemia

KENNETH E. FREEDLAND, PHD, ROBERT M. CARNEY, PHD,RONALD J. KRONE, MD, LAURIE J. SMITH, BA,MICHAEL W. RICH, MD, GAIL EISENKRAMER, RN, ANDKEITH C. FISCHER, MD

To determine whether psychological factors differentiate patients with silent versus sympto-matic myocardial ischemia, a battery of psychometric tests was administered to 68 patientswith positive thallium stress tests. Compared with patients who became symptomatic (n = 25),patients with silent ischemia on the treadmill (n = 24} were less often aware of cardiac andother bodily sensations (p < 0.005) and were less avoidant of harm or pain in general [p <0.05). They did not differ on variables associated with symptom reporting biases. To clarify therelationship between ischemia and symptom reporting, symptomatic patients were subgroupedon the basis of anginal pain latency. Psychologically, the patients with silent ischemia weremost similar to patients with the longest pain latencies and most different from those whoreported angina before the onset of ST depression. The psychological profile of patients withsilent ischemia during exercise testing is consistent with a reduced sensitivity to pain andother bodily sensations.

INTRODUCTION

Although angina pectoris is the mostcommon symptom of myocardial ische-mia in patients with coronary artery dis-ease (CAD), the majority of out-of-hospitalischemic episodes are asymptomatic (1-3). Some individuals with CAD arecompletely asymptomatic despite docu-mented ischemia, but silent ischemic ep-isodes are also common among patientswho do experience angina (2, 4). Silentischemia complicates the detection andtreatment of CAD, and it may be associ-ated with an increased risk of lethal ar-rhythmias and myocardial infarction (5).

From the Washington University School of Med-icine, St. Louis, Missouri.

Address reprint requests to: Kenneth E. Freed-land, Ph.D., Department of Psychiatry, WashingtonUniversity School of Medicine, P.O. Box 14109, St.Louis, MO 63178.

Received April 2,1990; revision received October3, 1990.

The mechanisms that determinewhether symptoms accompany ischemicepisodes are not well understood. Thereare no consistent differences in the sever-ity or duration of myocardial ischemiabetween silent and symptomatic episodes(6-8). There are, however, generalizeddifferences in pain threshold and toler-ance between individuals with predomi-nantly silent versus predominantly symp-tomatic ischemia (9-12). These differ-ences may be associated with underlyingvariation in endogenous opioid activity,but other central nervous system (CNS)factors are probably involved as well (13-19). Cognitive and personality factors,learned behavior, and affective state areknown to influence pain sensitivity andsymptom reporting (20, 21).

Similar factors have been shown to af-fect the perception and expression of an-gina pectoris. Early studies in this areadetermined that anxiety, depression, andsomatization correlate with the globalpresence and severity of angina among

Psychosomatic Medicine 53:13-24 (1991) 13

K. E. FREEDLAND et al.

patients with CAD (22-25). More recentstudies have focused on the psychologicalcorrelates of anginal symptoms duringactual ischemic episodes, usually onesprovoked by exercise testing. Droste andRoskamm (9) found that symptomaticpatients differed from asymptomatic pa-tients on the Nervousness, Excitability,Dominance, and Masculinity scales of theFreiberger Personality Inventory. Sheps etal. (26) reported that patients who com-plained of anginal symptoms during ex-ercise testing scored significantly higherthan patients with silent ischemia on theDepression Scale of the Minnesota Multi-phasic Personality Inventory (MMPI).

It is difficult to determine from existingstudies whether silent ischemia repre-sents the absence of pain perception orthe absence of symptom complaints de-spite pain perception. Some patients withapparently silent ischemia may actuallyexperience anginal symptoms but deny,misinterpret, or fail to report them. Psy-chological defenses, personality charac-teristics, and attitudes such as denial ofillness, social inhibition, or a reluctanceto entrust medical professionals with con-trol over one's health care, could producethis effect. For example, patients withdocumented CAD who exhibit Type Abehavior are less likely than Type B con-trols to report a history of typical anginaor anginal symptoms during treadmilltesting (27, 28). Certain personality char-acteristics such as neuroticism and affec-tive states such as depression are knownto have the opposite effect of increasingthe tendency to complain about physicalsymptoms (29, 30).

Some symptomatic patients tend tocomplain of chest pain early in the courseof ischemic episodes, even if their symp-toms are relatively mild, whereas othersendure prolonged ischemia before report-

ing any symptoms (12, 31). The rela-tionship between delayed reporting andnonreporting (i.e., silent ischemia) has notbeen systematically investigated. Silentischemia may represent an extreme on acontinuum of anginal symptom reportingbehavior rather than a distinct subtype ofCAD. If so, the psychological profile ofpatients with silent ischemia should re-semble that of patients who exhibit de-layed symptom reporting, and it shoulddiffer from the profile of patients whotend to report symptoms early in thecourse of ischemic events.

This study compares the psychologicalprofiles of patients with silent ischemiaon exercise stress testing to those withsymptomatic ischemia, and examines thepsychological correlates of early versusdelayed symptom reporting among symp-tomatic patients. The battery of psycho-logical tests assembled for this study in-cludes measures related to pain sensitiv-ity and others related to symptomreporting tendencies.

METHODS

SubjectsA consecutive series of 500 patients undergoing

exercise stress testing with lhallium-201 scintigra-phy at a university teaching hospital were screenedfor recruitment over a 10-month period. Informedconsent to participate in the study was solicitedduring the waiting period prior to the exercise test.In order to minimize the risk of false-positive tests,consenting patients were subsequently included inthe study only if their stress ECG and thalliumresults were both unequivocally positive for revers-ible myocardial ischemia. Patients with evidence ofmyocardial infarction or diabetes mellitus were ex-cluded in order to eliminate extraneous influenceson anginal symptomatology. Patients who had othertests or appointments scheduled after the stress testand who would thus be unavailable for participationwere also excluded. Nine patients were unavailable

14 Psychosomatic Medicine 53:13-24 (1991)

PSYCHOLOGICAL FACTORS IN SILENT ISCHEMIA

or refused to participate; of these, five would havebeen excluded on the basis of their stress test results,three had silent ischemia, and one had symptomaticischemia. Of those who consented to participate. 423were excluded on the basis of stress test results,evidence of previous myocardial infarction, or dia-betes. Fisher's Exact Test revealed no significantdifference in the proportion of patients with silentischemia who refused to participate (6.5%) versusthe proportion of symptomatic patients who refused(3.8%).

The resulting sample consisted of 43 (34 male,nine female) patients with no chest pain or discom-fort (i.e., silent ischemia) during the stress test and25 (20 male, five female) patients who did reportchest pain (i.e., symptomatic ischemia). Fifty-eightpercent of the silent versus 84% of the symptomaticpatients were being evaluated specifically for an-ginal complaints (x2 = 4.83, p < 0.03). The remainingpatients in both groups were undergoing routinescreening. Ninety-three percent of the silent ische-mia patients and 80% of the symptomatic patientswere white; the remaining patients in both groupswere black. The mean ages (±SD) of the silent andsymptomatic groups were 63.5 (±10.9) and 59.1 (±8.7), respectively. There were no significant differ-ences between the groups in sex ratio, racial com-position, or age. The groups also did not differ withrespect to hypertension (47% vs. 48%), current smok-ing (14% vs. 12%), or reported use of nitroglycerin(21% vs. 20%), beta-blockers (26% vs. 28%), or cal-cium channel blockers (37% vs. 36%).

ProcedureExercise Testing. Patients underwent a symptom-

limited standard or modified Bruce protocol exercisetreadmill test using a Marquette Case 12 system witha 6-second per 30-second ECG sampling rate. AllECGs were interpreted or reviewed by a senior car-diologist (RJK) with extensive experience in exercisestress testing who was blinded to psychometric data.The exercise ECG was considered positive for myo-cardial ischemia if there was >1 mm of horizontalor downsloping ST segment depression below theisoelectric line 80 msec after the J point. At the startof the test, patients were given standardized verbalinstructions to report any chest discomfort, fatigue,or other symptoms. Patients who continued exercis-ing without complaint despite apparent fatigue ordiscomfort were again encouraged to report anysymptoms, and all patients were asked to report the

time at which they expected to be able to continueexercising only 1 more minute. The onset time ofreported chest pain was recorded in 20 of the 25symptomatic cases.

Thallium Scintigraphy. At peak exercise or whensymptoms occurred, 2.5 mCi of IV thallium-201 wasadministered, and the patient was encouraged toexercise for 1 additional minute. The myocardiumwas then imaged as rapidly as possible using emis-sion tomographic technique. If the patient was una-ble to tolerate tomography, planar imaging was per-formed. For tomography, 80 12-second images wereperformed over a 180° arc from a 45° right anterioroblique (RAO) to a 135° left posterior oblique (LPO)projection. These images were processed by filteredback projection on an Adac Laboratories system andcompared with images collected 3 to 4 hours laterby similar technique. If planar imaging was per-formed, three 10-minute images in the 45° left an-terior oblique (LAO), anterior, and left lateral pro-jections were performed initially and again 3 to 4hours later. All films were interpreted by an expe-rienced radiologist (KCF) blinded to psychometricdata, clinical information, and ECG results.

Psychometric Tests. A battery of self-report psy-chometric tests was administered during the intervalbetween the initial and redistribution thalliumscans. The battery was designed to sample two dis-tinct domains: psychological correlates of sensitivityto aversive somatic sensations, especially pain anddiscomfort; and psychological factors that could po-tentially bias symptoms reporting behavior, eitherin the direction of reduced reporting or increasedreporting. Two tests were selected to sample corre-lates of pain sensitivity: (1) A modified version ofthe Aufonomic Perception Questionnaire (APQ) (32).The APQ is a 21-item rating scale which assesseshow frequently the respondent perceives sensationsassociated with autonomic nervous system activity.The standard APQ is limited to sensations that occurwhen the individual is anxious. The modified ver-sion is not restricted in this manner, and the itemsassess perception of autonomic and other bodilysensations in general. It was hypothesized that pa-tients with silent ischemia would score lower thansymptomatic patients on the APQ. (2) The 100-itemversion of the Tridimensional Personality Question-naire (TPQ) (33-35). The subscales of this personalityinventory measure novelty seeking, the tendency torespond with intense excitement to novel stimuli,cues for potential rewards, and cues for relief fromaversive stimuli; harm avoidance, the tendency torespond intensely to cues for aversive stimuli and toinhibit behavior in order to avoid punishment; and



reward dependence, the tendency to respond in-tensely to cues for reward and to persist in behaviorspreviously associated with rewards or relief frompunishment. Low levels of harm avoidance, noveltyseeking, and reward dependence are associated withrelative insensitivity to pain, whereas high levelsare associated with neuroticism, high pain sensitiv-ity, low pain tolerance, and rapid escape from pain-ful stimulation (33, 36). Thus, symptomatic patientswere predicted to score higher than patients withsilent ischemia on all TPQ subscales. Three testswere chosen to sample potential symptom reportingbiases: (1) A modified version of the Cardiac DenialScale (CDS) (37). The eight-item CDS assesses denialof cardiac illness, minimization of its impact, andconscious suppression of thoughts about it. Thestandard CDS is specific to post-MI patients, whereasthe modified version assesses psychological defensesagainst the threat of any cardiac illness. It was hy-pothesized that higher scores would be associatedwith reduced symptom reporting, i.e., silent ische-mia. (2) The Beck Depression Inventory (BD/) (38).The BD1 is a 21-item measure of the severity ofdepressive symptoms. It assesses dysphoric moodsthat are frequently associated with increased com-plaints of physical symptoms. Thus, symptomaticpatients were expected to score higher than patientswith silent ischemia on this measure. (3) The Mul-tidimensional Health Locus of Control Scale (MHLCS)(40). This 18-item instrument assesses beliefs regard-ing who or what determines the respondent's health,i.e., the patient (Internal subscale), doctors andnurses (Powerful Other subscale), or fate (Chancesubscale). It was designed to differentiate betweenpatients with divergent behavioral responses toequivalent medical problems, such as women whoseek immediate medical attention upon discoveringa breast mass versus those who delay reporting theirsymptoms to a physician as long as possible (39).Patients obtain high scores on the Powerful Othersubscale by endorsing items such as "Whenever Idon't feel well, I should consult a medically trainedprofessional." High scores on this scale thus reflectthe patient's belief that it is important to reportsymptoms to their physician or nurse. In contrast,patients with low scores on this subscale or highscores on the Internal or Chance subscales are lesslikely to believe that symptom reporting is importantor beneficial. Thus, in comparison to symptomaticpatients, subjects with silent ischemia were pre-dicted to score lower on the Powerful Other subscaleand higher on the Internal and Chance subscales.

Statistical Analyses. Two-tailed t tests were usedfor comparisons of continuous stress test variables,

and a two-tailed Fisher's Exact Test (FET) was usedto evaluate reason for stress test termination. MAN-OVAs for unbalanced designs were used forsubgroup comparisons of psychometric variables. Inthe primary analysis, separate MANOVAs were per-formed on the two dependent variable sets. ANOVAsfor unbalanced designs were used for subgroup com-parisons of other continuous variables. Duncan'smultiple range was used for subsequent tests. Chi-square was used to compare the distributions ofcategorical variables. Pearson product-moment cor-relations and stepwise linear regression were usedto determine the relationship between the psycho-metric variables and pain latency (the time lag be-tween onset of ST depression and the onset of chestdiscomfort). The significance criterion for all statis-tical tests was 0.05.

RESULTS

The results of the stress test are sum-marized in Table 1. There were no signif-icant differences between the groups withrespect to total exercise duration, timefrom onset of electrocardiographic indi-cations of ischemia to the end of exercise,maximum double product, or estimatedMETs. The groups did differ, however,with respect to the primary reason for testtermination. Whereas chest discomfortwas the most common reason amongsymptomatic patients, 48% of the silentischemia patients exercised until theywere too fatigued to continue. Thus, thereis no evidence that the patients classifiedas having silent ischemia simply exer-cised less strenuously or for less time thantheir symptomatic counterparts.

The psychological characteristics of thesilent and symptomatic groups are listedin Table 2. There was a significant overallbetween-group effect in the "pain sensi-tivity" dependent variable set (multivar-iate F(4,61) = 2.54, p < 0.05). The silentischemia group scored significantly lowerthan the symptomatic patients on the



TABLE 1. Stress test results."

Silentn = 43

Symptomaticn = 25

Total duration (minutes)Time from onset of 1 mm ST-

segment depression to end oftest

Maximum double productEstimated METsPrimary reason for termination

of stress (percent of patients)Achieved target heart rateChest discomfortFatigueOther

7.77 ± 3.054.48 ± 2.73

27290.16 ±5734.198.39 ± 3.60

16.3%0.0%

48.8%34.9%

7.27 ±3.203.99 ±3.59

24873.27 ± 6915.147.26 ± 2.34

24.0%32.0%16.0%28.0%

0.62 NS"0.56 NS

1.45 NS1.49 NS

FET§ p < 0.0001

' Plus-minus values are means ± SD.'' NS, not significant.§ Fisher's Exact Test, 2-tailed.

TABLE 2. Psychometric Characteristics of the Silent and Symptomatic Groups."

"Pain sensitivity" measuresAutonomic perception questionnaireTridimensional Personality Question-

naireNovelty seekingHarm avoidanceReward dependance

"Symptom reporting bias" measuresCardiac denial scale

DenialMinimizationSuppression

Multidimensional health locus of con-trol scaleInternalPowerful otherChance

Beck Depression Inventory

Silentn = 43

46.5 ± 25.0

12.3 ± 3.69.7 + 5.5

19.9 ± 3.5

0.8 ±0.82.2 ± 1.10.9 ± 0.9

24.6 ± 5.521.3 ± 5.115.3 ± 5.76.9 ± 5.4

Symptomaticn = 25

68.9 ± 32.4

11.5 ± 3.812.7 ± 6.220.0 ± 3.7

0.7 ±0.82.0 ± 1.31.1 ±0.8

23.9 ±6.220.7 ± 6.017.3 ± 6.39.7 ± 7.1

F

2.549.82

0.564.010.011.12

0.200.890.19

0.360.071.203.15

P

<0.05<0.005

NSC

<0.05NSNS

NSNSNS

NSNSNSNS

D(s)"

14.53

1.862.941.81

0.400.600.43

2.942.803.023.17

•' Plus-minus values are means ± SD. F values listed at the top of each set of dependent variables are multivariatetests of the hypothesis of no overall between-group effect for the set.'' D(s) value is the smallest detectable population mean difference given the observed sample sizes andvariances, by a power analysis procedure described by Cohen (45).' NS, not significant.

Autonomic Perception Questionnaire (F= 9.82, p < 0.005) and the TPQ HarmAvoidance scale (F = 4.01, p < 0.05). Thegroups did not differ on the TPQ Novelty

Seeking and Reward Dependence sub-scales. There was no overall effect in the"symptom reporting bias" set (multivar-iate F(7,52) = 1.12, p > 0.05). None of the



univariate comparisons within this setwere significant, although there was atrend towards higher scores on the BeckDepression Inventory in the symptomaticgroup (F = 3.15, p = 0.07).

Pain latency data were collected on asubsample of 20 symptomatic patients,but complete psychometric data were notavailable in two of these cases. A stepwiselinear regression of pain latency on thepsychometric variables was then per-formed. As shown in Table 3, the TPQReward Dependence and Harm Avoid-ance scales were retained in the final stepand accounted for 57% of variance in painreporting latency. Higher Reward De-pendence and Harm Avoidance scoreswere associated with shorter pain laten-cies. There was a significant inverse cor-relation between the Beck Depression In-ventory and pain latency (r = —0.53, p =0.02), but this variable was dropped fromthe multiple regression equation as it didnot significantly improve the model afterthe other predictors had been entered.

The first chest pain report preceded theonset of ST depression in nine patients.Table 4 compares the times to ST segmentdepression, ages, and psychometric pro-files of these "pre-ST" reporters to the fivepatients who reported pain within 1 min-

TABLE 3. Stepwise Multiple Regression of PainReporting Lag on the Psychometric Variables.

df Mean Square

Regression 2Error 15Total 17

Variable

(Intercept)Reward dependenceHarm avoidanceTotal R2

66.116.61

B

13.50-0.50-0.23

Partial

0.430.140.57

F P

10.01 0.002

R2 F

12.074.96

P

0.0030.04

ute after onset of ST depression ("earlypost-ST reporters"), the six who reportedpain more than 1 minute post-onset ("latepost-ST reporters"), and the 42 patientswith silent ischemia on the treadmill. Toreduce the risk of Type I error, only thosepsychometric variables found to be sig-nificant in the previously described anal-yses were included in this post hoc com-parison. There were no differences amongthe groups on time to onset of ST depres-sion (F(3,50) = 0.29, p > 0.05), but theearly post-ST reporters were significantlyyounger than the pre-ST reporters andsilent ischemics (F(3,59) = 3.46, p = 0.02).MANOVA revealed significant between-group differences on all of the psycho-metric measures included in this analysis(i.e., the Autonomic Perception Question-naire, Beck Depression Inventory, TPQHarm Avoidance, and TPQ Reward De-pendence scales; multivariate F(12,145) =2.46, p < 0.01; p < 0.05 for all omnibus Ftests). Pairwise subsequent tests of be-tween-group differences are reported inTable 4.

DISCUSSION

This study identified significant psy-chometric differences between patientswith symptomatic versus asymptomaticischemia on exercise stress testing. Thedifferences are consistent with a relativeinsensitivity to pain and discomfortamong patients with silent ischemia.There were no differences on the CardiacDenial Scale, the MultidimensionalHealth Locus of Control Scale, or the BeckDepression Inventory, which measurepsychological factors believed to influ-ence symptom reporting behavior. Therewere, however, significant differences on



TABLE 4. Comparison of Patients with Silent Ischemia to Those Who Reported Chest Discomfort Priorto, Early after, or Late after the Onset of ST Segment Depression during Exercise Treadmill Testing,"

Variable

Lag between onst of STdepression and re-ported pain (minutes)

ST depression onset (min-utes)

Age

Autonomic perceptionquestionnaire

Beck depression inven-tory

TPQ harm avoidance

TPQ reward dependence

F

0.29

3.46*

3.93*

4.31"

3.21*

3.47*

Pre-STReporters

n = 9

-2.1 ± 1.7

4.2 ± 2.1

63.7 ± 6.4A

78.0 ± 34.1

A12.2 ±6.5

A15.3 ±5.7

A21.8 ±4.1

A

Early Post-STReporters

n = 5

0.3 ±0.3

3.9 ± 1.8

50.6 ±8.1B

72.6 ± 34.9

A, B10.4 ±6.8

A11.6 ± 6.3

A, B21.8 ± 3.0

A

Late Post-STReporters

n = 6

5.0 ±2.3

3.1 ±4.4

55.3 ± 6.9A, B

51.5 ± 33.9

A, B2.7 ±2.7

B7.3 ± 5.0

B16.3 ± 1.5

B

SilentIschemics

n = 43

3.3 + 2.7

63.5 + 11.0A

46.5 ± 25.0

B6.9 ± 5.4

A, B9.7 ±5.5

A, B19.9 + 3.5

A

' Plus-minus values are means ± SD. For the psychometric variables, multivarite F(12, 145) = 2.46, p < 0.01.Within rows, means sharing the same letter A or B, are not significantly different from Duncan's multiple rangetest.*p<0.05.* *p<0.01.

the Autonomic Perception Questionnaireand on the TPQ Harm Avoidance scale,which measure psychological factors re-lated to pain sensitivity.

The asymptomatic patients exercised asvigorously and, in many cases, more vig-orously than their symptomatic counter-parts. It is, therefore, unlikely that theabsence of symptoms among the patientswith silent ischemia could be due to sub-maximal effort. The groups also did notdiffer with respect to other medical ordemographic variables. Since these werepatients being screened for coronary heartdisease, none of them had undergone car-diac catheterization. Thus, it was not pos-sible to determine whether the groupsdiffered with respect to the severity ofcoronary artery disease. The possibility of

sampling bias also cannot be completelyruled out, as it is not known whetherpatients who did not have time or whorefused to participate in the study mighthave differed from participating subjects.However, neither the availability of timeto participate nor the decision to consentcould have been influenced by the stresstest results. Furthermore, most patientswho were excluded from the study didnot meet the cardiological inclusion cri-teria, and the ratio of silent to sympto-matic cases in the present sample is sim-ilar to that reported in other studies (41,42). It is possible that the treadmill expe-rience may have influenced the psycho-metric test results. However, few of thequestionnaire items pertained specificallyto cardiac symptoms or heart disease. The



Cardiac Denial Scale is the principal ex-ception to this, but no differences be-tween groups was found on this measure.Furthermore, some of the cardiac itemson the Autonomic Perception Question-naire differentiated the groups, but so didsome of the non-cardiac items. In sum-mary, there were no obvious confoundsin the relationship between symptom sta-tus and psychometric profile, but this can-not be ruled out altogether.

An item analysis of the Autonomic Per-ception Questionnaire revealed signifi-cant differences in the frequency of per-ception of both cardiac (e.g., increasedheart rate) and noncardiac (e.g., drymouth, headache) items, as well as onitems pertaining to the awareness of bod-ily sensations in general. Thus, the mark-edly lower Autonomic Perception scoresin the silent ischemia group do not simplyreflect differences in anginal symptoma-tology, but instead suggest a generalizeddifference in awareness of bodily sensa-tions. This is consistent with previous re-search demonstrating differences be-tween patients with silent versus symp-tomatic ischemia in perceptual thresholdfor a variety of painful stimuli (9-11).

Among the symptomatic patients, thebest predictors of pain latency were theTPQ Reward Dependence and HarmAvoidance scales. Although not an inde-pendent predictor, the Beck DepressionInventory also correlated with pain la-tency. Thus, higher levels of reward de-pendence, harm avoidance, and depres-sion were associated with shorter painlatencies. High levels of harm avoidanceare associated with low tolerance for pain-ful stimulation, and high levels of rewarddependence are associated with greatersensitivity to signals of relief of pain andother aversive stimuli (36). The relation-ship between the Beck Depression Inven-

tory and pain latency is consistent withthe increased somatic complaints associ-ated with depression (30). These findingssuggest that differences in pain latencyamong patients who do experience anginaduring exercise stress testing may reflectdifferences both in pain sensitivity and insymptom reporting tendencies.

The onset of anginal pain typically fol-lows rather than precedes the onset of STsegment depression. Both of these eventstend to occur relatively late in the path-ophysiological sequence of ischemic epi-sodes (43). The finding that pain reportingin some cases precedes the onset of STdepression by as much as several minutessuggests that these patients may learn toidentify early signs of impending ischemicevents before they experience more se-vere anginal symptoms. It has long beensuspected that anginal symptoms may bemodified by conditioning (44). Pre-ST re-porters may learn to avoid severe anginaby terminating strenuous effort whenmild anginal symptoms, exertion-relatedcues, or other precursors are perceived.

The pre-ST reporters were relativelyolder and more harm avoidant, rewarddependent, and dysphoric than the latepost-ST reporters. The mean Beck Depres-sion Inventory score in the pre-ST groupwas in fact above the cutoff for mild clin-ical depression. Although there was atrend towards higher scores on severalpsychometric measures (APQ, BDI, andTPQ Harm Avoidance) in the pre-ST thanin the early post-ST group, none of thesedifferences were statistically significant.Studies of larger samples are needed todetermine whether pre-ST reporters dif-fer psychologically from early post-ST re-porters.

It is conceivable that the seemingly pre-mature reporting of chest discomfort inthe pre-ST subgroup could be an artifact



in that electrocardiography is relativelyinsensitive to posterior ischemia. Perhapspatients with posterior ischemia begin toexperience ischemic pain before ST seg-ment changes become evident. However,posterior ischemia was not detected onthallium scintigraphy in any patient inthe pre-ST subgroup, whereas all patientswere found to have ischemia in one ormore other regions.

There was only one significant psycho-metric difference between the patientswith silent ischemia and the subgroup ofsymptomatic patients with the longestpain latencies: The late post-ST reporterswere less reward dependent than all othersubgroups, including the patients with si-lent ischemia. Furthermore, the psycho-metric scores of the pre-ST and early post-ST reporters were generally higher thanthe scores of the late reporters and silentischemics. These results must be inter-preted with caution, given the relativelylow statistical power of the comparisons.Nevertheless, they suggest that patientswho exhibit silent ischemia during exer-cise treadmill testing are most similarpsychologically to patients who are symp-tomatic but who tolerate prolonged ische-mia before complaining of chest discom-fort, and least like patients who reportchest discomfort prior to the onset of STdepression. Thus, silent ischemia does ap-pear to represent a relatively extremepoint on a continuum of anginal symptomreporting behavior, rather than a condi-tion that is categorically different thanfrom symptomatic ischemia.

Patients who report anginal symptomseither prior to or several minutes after theonset of ST segment depression are partic-ularly interesting subgroups and deservefurther investigation. Age and psycholog-ical differences among pre-ST, early post-ST, and late post-ST reporters reveal con-

siderable heterogeneity among sympto-matic patients. This heterogeneity shouldbe taken into account in future studies ofsilent ischemia which utilize sympto-matic control groups.

The inclusion of relevant psychologicalvariables in future research on the mech-anisms underlying silent myocardial is-chemia and angina pectoris is clearly war-ranted. Further refinement of the emerg-ing psychological profile of patients withsilent ischemia is also needed in order topromote early detection of asymptomaticCAD. This could have important clinicalimplications in reducing the proportion ofpatients presenting with myocardial in-farction or sudden cardiac death as theinitial manifestation of CAD. Further-more, the assessment of relevant psycho-logical characteristics may augment thepredictive utility of anginal symptoms (ortheir absence) in cardiological evaluationsof patients at risk for coronary artery dis-ease.

SUMMARY

Patients with evidence of silent ische-mia on thallium exercise stress testingwere less aware of cardiac and other bod-ily sensations and less avoidant of harmand pain in general than patients withsymptomatic ischemia. No differenceswere found on measures of denial orhealth locus of control. These results areconsistent with previous reports of gen-eralized pain threshold differences be-tween patients with silent or symptomaticischemia, and inconsistent with the hy-pothesis that ischemia is "silenced" by abias against reporting perceived symp-toms. Furthermore, symptomatic patientswere classified on the basis of anginal pain



latency. Psychologically, patients with si- point on a continuum of symptom report-lent ischemia were most similar to pa- ing behavior,tients whose first report of chest discom-fort lagged at least 1 minute after the onset Support for this project was provided inof electrocardiographic indications of is- part by a grant from the American Heartchemia, and least like those who reported Association, St. Louis Chapter,symptoms prior to the ECG onset. This The authors wish to thank Robert B.suggests that from a behavioral perspec- Case, M.D., C. Robert CJoninger, M.D., andtive, silent ischemia and angina pectoris AJJan S. Jaffe, M.D. for their helpful sug-are not discretely different expressions of gestions on this project, and Karen CJarkischemic heart disease. Instead, silent is- for her assistance with the preparation ofchemia appears to represent an extreme this manuscript.

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Psychological factors in silent myocardial ischemia