Ambulatory (Holter) electrocardiography and myocardial ischemia

Association of hypoglycemia and cardiac ischemia: a study based on continuous monitoring

OBJECTIVE

In some studies intensive diabetes treatment in patients with type 2 diabetes may be associated with increased cardiovascular events. It is not clear whether these events are related to hypoglycemic episodes. To determine whether episodes of hypoglycemia were more likely to be associated with cardiac ischemia than normoglycemia or hyperglycemia, we carried out a study in 21 patients with coronary artery disease (CAD) and type 2 diabetes treated with insulin who had good glycemic control.

RESEARCH DESIGN AND METHODS

We carried out 72-h continuous glucose monitoring along with simultaneous cardiac Holter monitoring for ischemia. Patients also recorded symptoms of cardiac ischemia (chest pain) and symptoms of hypoglycemia.

RESULTS

Satisfactory continuous glucose monitoring system recordings were obtained in 19 patients. We recorded 54 episodes of hypoglycemia (blood glucose <70 mg/dl; 26 of these were symptomatic) and 59 episodes of hyperglycemia (blood glucose >200 mg/dl; none symptomatic). Of the 54 episodes of hypoglycemia, 10 were associated with symptoms of chest pain, during 4 of which electrocardiographic abnormalities were documented. In contrast, only 1 episode of chest pain occurred during 59 episodes of hyperglycemia. No chest pain or electrocardiographic abnormalities occurred when the blood glucose was within the normal range. The difference between the frequency of ischemia during hypoglycemia and the frequency during both hyperglycemia and normoglycemia was statistically significant (P < 0.01). There were 50 episodes during which the blood glucose changed by >100 mg over a 60-min period, and ischemic symptoms occurred during 9 of these episodes (P < 0.01 compared with stable normoglycemia or hyperglycemia).

CONCLUSIONS

Hypoglycemia is more likely to be associated with cardiac ischemia and symptoms than normoglycemia and hyperglycemia, and it is particularly common in patients who experience considerable swings in blood glucose. These data may be important in the institution of insulin treatment and attempting near-normal glycemia in patients with known CAD. Further research is needed to determine strategies to prevent ischemia associated with hypoglycemia.

Cardiac arrhythmias and silent myocardial ischemia during hemodialysis

Cardiac arrhythmias are noted in a significant proportion of chronic renal failure (CRF) patients on hemodialysis (HD), and may contribute to cardiovascular mortality. A number of factors have been implicated in the genesis of these arrhythmias. The role of silent myocardial ischemia (SMI), however, has not been evaluated systematically. We prospectively studied 38 unselected CRF patients on regular HD by continuous Holter monitoring starting 24 hours before HD, lasting through the dialysis session and continued for 20 hours thereafter. The recordings were analyzed for frequency, timing and severity of supraventricular and ventricular arrhythmias and SMI as identified by ST-segment depression. Ventricular arrhythmias during HD were noted in 11 (29%) patients (group I), and were potentially life-threatening (Lown Class III and IVa) in 13%. The remaining 27 patients (group II) had no ventricular arrhythmias during HD. There was no difference in the age, sex ratio, duration of HD, blood pressure, fluctuations in weight, hematocrit, predialysis creatinine, sodium, potassium, calcium or inorganic phosphate levels between patients in the two groups. The number of patients with clinical ischemic heart disease was significantly greater in group I. SMI was noted in 72% and 33% of group I and II patients respectively (p = 0.026). 46% of those with and 25% of those without ST changes during HD developed ventricular arrhythmias during HD. Both SMI and ventricular arrhythmias were noted most frequently during the last hour of dialysis. Hypertension, diabetes mellitus and ischemic heart disease were observed more frequently amongst patients with SMI. Ventricular arrhythmias are detected in a significant proportion of CRF patients on HD. These are probably related to coronary artery disease since silent myocardial ischemia is also noted more frequently during HD in these patients. Further studies incorporating coronary angiography are needed in a larger number of patients to establish a definite causal relationship.

A pilot study of continuous ambulatory electrocardiography in patients donating blood for autologous use in elective coronary artery bypass grafting

BACKGROUND

A pilot study was conducted to evaluate the impact of a single autologous blood donation on the presence or absence of myocardial ischemic episodes in patients with coronary artery disease.

STUDY DESIGN AND METHODS

Fifty patients scheduled for elective coronary artery bypass grafting underwent two 24-hour periods of ambulatory electrocardiogram monitoring, one before and one after their first autologous blood donation. The presence or absence and the number, duration, and integral area of episodes of ST segment depression for each 24-hour monitoring period were determined.

RESULTS

Forty-two patients had legible electrocardiogram recordings for both monitoring periods. Of these, 36 patients (86%) had at least one episode of ST segment depression during any monitoring period. The number of patients who had at least one episode of ST segment depression before donation was not significantly different from the number of those who had at least one episode after donation (31 and 33 patients, respectively; p = 0.73).

CONCLUSION

Donating a unit of blood had no demonstrable effect on the presence or absence of myocardial ischemic episodes in this sample of 42 autologous blood donors with coronary artery disease. The results of this study should be validated in further trials.

Automated ST-segment analysis during cesarean delivery: effects of ECG filtering modality

STUDY OBJECTIVES

To determine the effect of different electrocardiographic (ECG) filtering modalities on ST-segment changes during cesarean delivery. We compared the use of narrow and standard bandwidth ECG filtering modes in assessing ECG-detected ischemic changes in healthy patients undergoing routine, elective cesarean delivery.

DESIGN

Prospective, nonrandomized clinical trial.

SETTING

Academic medical center.

PATIENTS

20 healthy parturients undergoing elective cesarean delivery with regional anesthesia.

INTERVENTION

Continuous 5-lead ECG monitoring was performed in all 20 study parturients. The same incoming ECG signal was divided by a special cable and displayed on two Marquette 7010 monitors. Leads I, II, and V5 were analyzed. One of the monitors filtered the signal with a 0.07 to 100 Hz filter (DIAG), the other with a 0.3 to 40 Hz filter (MON). The ST segment was analyzed continuously by electronic comparison with a template established as a baseline at the beginning of the case. This continuous output was led in digital form every 15 seconds to an IBM PC computer for data analysis.

MEASUREMENTS AND MAIN RESULTS

In each of the leads analyzed, the mean MON versus DIAG different showed a bias, with MON showing consistently lower (ie, more negative) readings than DIAG. Using different criteria for ST depression (> 0.25, > 0.5, or > 1.0mm), we categorized patients as showing more ST depression on either MON or DIAG. With the 0.25 mm criterion, ST depression was identified significantly more often in MON then DIAG in leads H and V5 (p < 0.05). Using the other criteria, the differences were similar, but were not statistically significant. In general, very few instances of ST depression were identified in lead I. No patient had sequelae indicative of intraoperative myocardial ischemia, such as chest pain, dyspnea, persistent ectopy, or hemodynamic instability.

CONCLUSIONS

In patients at low risk for myocardial ischemia, narrow bandwidth (monitor mode) ECG filtering reveals greater degrees of ST-segment depression than does standard (diagnostic mode) ECG filtering. Studies examining ST-segment phenomena would be facilitated by including a description of the ECG filtering-technique.

Validation testing of the SEER real-time digital holter monitor

OBJECTIVES

Perioperative myocardial ischemia, detected by off-line Holter ST-segment monitoring, has been associated with adverse cardiac outcome. Technical advances in digital signal processing have facilitated development of digital Holter recorders that allow 24- to 48-hour recording, full disclosure storage, and "real-time" quantitative analysis of ST-segment levels. These recorders may be useful for "on-line" clinical detection of perioperative ischemia. However, little data are available, independent of manufacturers' claims, to validate their accuracy. Using a previously validated digital electrocardiogram (ECG) simulator, a commercially available device was evaluated.

DESIGN

Laboratory bench study.

SETTING

Not applicable.

PARTICIPANTS

Not applicable.

INTERVENTIONS

Not applicable.

MEASUREMENTS AND MAIN RESULTS

Custom digital ECG waveform templates were programmed for use with a commercially available ECG simulator (M311 ECG simulator; Fogg Systems, Inc, Aurora, CO). For each template, ST-segment morphology (horizontal elevation or depression, downsloping depression), QRS duration (80 v 120 msec) and the presence or absence of a P wave were manipulated, yielding six unique QRS shapes. For each shape, the degree of ST-segment deviation was altered over a wide range. ST-segment values from the simulator (measured at 60 msec after the J point) ranged from +10 to -18 mm. The SEER digital Holter recorder (Marquette Electronics, Milwaukee, WI) was tested. One hundred twenty-six measurements of ST-segment deviation were input to the SEER at each of two testing sessions. The ST-segment value from the recorder in the "noninteractive" analysis mode was obtained, and the two results averaged for comparison with the expected simulator value. Variability of ST-segment measurement over a continuous 1-hour period of simulator input was also assessed. Sixty-seven percent of measurements were within 95% to 100% of expected, whereas 90% were within 90% to 110%. The regression equation for the complete dataset was SEER output (mm) = -0.47 + 1.015 * simulator input, R2 = 0.99. The mean observed-to-expected value ratio was 100% +/- 6% (+/-SD), range 80% to 114%. The mean deviation in millimeters from expected for all measurements was 0.10 +/- 0.20 mm, median 0.05 mm, range -0.25 to +0.60 mm. For the 72 measurements obtained by 5-minute sampling over 1 hour of continuous simulator input for each of the six QRS shapes, the mean percent difference between observed and expected values was 0.5% +/- 4.5%, median 0.0%, with a mean coefficient of variation of 2.7% (median 1.9%).

CONCLUSIONS

Using a digital ECG simulator, it was found that the SEER recorder analyzed ST-segment deviation with a high degree of accuracy. These findings, along with its full disclosure reporting capabilities, suggest it may be useful in perioperative risk stratification. However, accuracy in the clinical setting remains to be validated.

Blood pressure influences the occurrence of complex ventricular arrhythmia in hemodialysis patients

We investigated the relationship between blood pressure and the occurrence of complex ventricular arrhythmias (multiform, couplets, or runs) as assessed by 48-hour Holter monitoring in 74 stable long-term hemodialysis patients (44.5 +/- 12 years old; 54% men; 74% whites; dialysis duration, 51.3 +/- 36.1 months; systolic pressure, 146.6 +/- 19.3 mm Hg; diastolic pressure, 89.2 +/- 12.1 mm Hg; prevalence of arterial hypertension, 33.8%). Systolic and diastolic pressures represented the average of all predialysis determinations during the 3 months preceding the tests. Hemodialysis was performed midway through the Holter monitoring period. M-mode and bidimensional echocardiograms and myocardial perfusion tests were also obtained from all patients. Complex arrhythmias were observed in 37 individuals (50%). Univariate analysis showed that systolic pressure (P < .001), diastolic pressure (P < .05), age (P < .001), left ventricular posterior wall thickness (P < .01), left ventricular mass index (P < .05), and ischemic alterations on myocardial perfusion tests (P < .005) were significantly associated with complex arrhythmias. With the use of a multivariate model (stepwise logistic regression analysis) only systolic pressure (P < .01) and age (P < .05) were independently associated with complex arrhythmias. Sex; angina; dialysis duration; New York Heart Association functional class; use of digitalis; plasma levels of creatinine, sodium, potassium, calcium, and phosphate; hematocrit; left ventricular fractional shortening; left ventricular diastolic diameter; and ST segment deviation were not correlated with complex arrhythmias. The severity and frequency of complex arrhythmias were not influenced by hemodialysis. At follow-up (5 to 80 months) 5 patients had died of sudden death, 4 of whom were hypertensive and older than 45 years.(ABSTRACT TRUNCATED AT 250 WORDS)

Evaluation of a nine-lead Holter monitor for identifying and localizing ischemia and coronary artery disease detected by quantitative thallium-201 tomography

We devised a nine-lead Holter monitor system with a lead-switching technique to record electrocardiograms from multiple sites in the anterior and the posterior or lateral chest. Leads CM1 to CM6, high lateral (HL), low lateral (LL), and low posterior chest (LB) were used. The sensitivity, specificity, and predictive accuracy of this system for identifying specific regions of myocardial ischemia and coronary artery disease were investigated in 130 patients with coronary artery disease. Anterolateral leads (CM4 to CM6, HL, and LL) showed high sensitivity for detecting anterior and lateral ischemia (69% to 100%) but low specificity (4% to 44%) compared with tomographic results. The specificity of these leads for identifying single-vessel disease was low (6% to 47%) although some leads showed high sensitivity (69% to 100%). In contrast, the LB lead exhibited high sensitivity and specificity for detecting inferior ischemia (70% and 95%, respectively) and right coronary artery (RCA) disease (74% and 93%, respectively). Consequently, ST depressions in the LB lead (anode) are specific for identifying inferior ischemia and RCA disease, whereas those in the anterior and lateral chest leads do not identify the ischemic region or the obstructed coronary artery.

Improved detection of transient myocardial ischemia by a new lead combination: value of bipolar lead Nehb D for Holter monitoring

The investigations of ST-segment changes by Holter monitoring demonstrate asymptomatic and symptomatic episodes of myocardial ischemia, which may occur during daily activities. One factor, which is of great importance for the detection of silent myocardial ischemia during ambulatory monitoring, is the combination of the leads. Former studies showed that the analysis of two channels alone may not adequately detect silent myocardial ischemia. We therefore used a three-channel ambulatory ECG monitoring system with a new lead combination. The Holter monitoring results were correlated with the distribution of coronary stenosis detected by coronary angiography. In 54 patients with single coronary vessel disease and ischemic ST-segment depressions during exercise testing, standard Holter lead combination CM2/CM5 was extended by a bipolar Nehb D-like lead. Lead combination CM2/CM5 identified 23 patients (43%) with ST-segment depressions (total number of ischemic episodes = 372). Additional Nehb D-like lead identified 30 patients (55%) with ST-segment depressions (total number of ischemic episodes = 1048). The combination of leads CM2/CM5 and Nehb D raised the number of patients with documented ST-segment depressions to 33 of 54 (61%). Lead Nehb D showed the highest sensitivity for the detection of inferior wall ischemia (stenosis of the right coronary artery); nevertheless, this lead may not be regarded as specific for ST-segment alterations only caused by inferior wall ischemia. The correlation of ischemic ST-segment depressions during exercise testing (classified as anterior, inferior, or anterior and inferior type of ischemia) and documented ST-segment changes in the different Holter leads underline these results.(ABSTRACT TRUNCATED AT 250 WORDS)

Scintigraphic and electrocardiographic evidence of silent coronary artery disease in asymptomatic hypertension: a case-control study

OBJECTIVES

This study was conducted to determine the incidence of physiologically significant coronary artery disease in a group of asymptomatic high risk men with essential hypertension and to assess the validity of noninvasive tests in a subset of these patients undergoing coronary arteriography.

METHODS

Two hundred twenty-six asymptomatic men (mean age 61 +/- 8 years) with essential hypertension and no clinical evidence of coronary artery disease but with at least one additional coronary risk factor were studied prospectively. Fifty age- and risk factor-matched normotensive subjects were evaluated as a control group. After a minimum of 4 days without medication, subjects underwent stress thallium-201 scintigraphy, exercise and 48-h ambulatory electrocardiography, and echocardiography. Coronary angiography was performed in a subset of 34 (40%) of 84 patients with one or more positive test results.

RESULTS

A positive thallium-201 scintigram (18% vs. 6%; odds ratio 3.4, confidence interval 0.95 to 10.8, p = 0.056), exercise electrocardiograms (ECGs) (37% vs. 13%; odds ratio 4.1, confidence interval 1.5 to 11.2, p < 0.003) and ambulatory ECG (15% vs. 0%, p < 0.05) were more common in the hypertensive group than in the control group. In the cohort undergoing coronary angiography, thallium-201 scintigraphy was both sensitive and specific for epicardial atherosclerotic coronary disease (90% and 79%, respectively), but positive exercise and ambulatory ECGs occurred frequently in the absence of significant coronary stenoses. In the 39% of hypertensive patients who had mild to moderate left ventricular hypertrophy, positive exercise and ambulatory ECGs occurred at a higher rate.

CONCLUSIONS

These findings suggest that physiologically significant coronary artery disease occurs more frequently in asymptomatic hypertensive men than in comparable normotensive control subjects. In the subgroup undergoing coronary arteriography, reversible scintigraphic defects were both sensitive and specific for diagnosing epicardial coronary artery disease, but exercise and ambulatory ECGs appeared to yield frequent false positive results, especially when left ventricular hypertrophy was present. These results indicate that patients with "silent" coronary artery disease can be identified among high risk hypertensive patients, but the appropriate application of such screening in clinical practice remains to be determined.

Prognostic significance of silent myocardial ischemia after a first uncomplicated myocardial infarction

Forty asymptomatic patients were studied after a first uncomplicated myocardial infarction. They were 36 men and 4 women, with a mean age of 52.6 yr; the location of myocardial infarction was in the anterior wall in 18 (45%) patients and in the inferior wall in 22 (55%). The patients were submitted to: (1) 48-h Holter monitoring, during the 2nd and 8th weeks after the acute event; (2) exercise testing during the same periods; (3) cardiac catheterization and coronary arteriography. Patients with clinical conditions associated with cardiac rhythm disturbances or repolarization abnormalities were excluded. The electrocardiographic methods identified 11 (27.5%) patients with silent myocardial ischemia. Patients with and without silent ischemia were similar in relation to sex, age, coronary risk factors, arrhythmias, left ventricular function and follow-up. Patients with silent ischemia had more inferior wall myocardial infarctions, but the difference was not statistically significant. Patients with silent ischemia had significantly more extensive coronary artery disease (45.5% multivessel disease) when compared to those without ischemia (14.8% multivessel disease) (p < 0.05). After a 2-yr follow-up, 4 (36.4%) patients with and 1 (3.4%) without silent ischemia had a coronary event (p < 0.05). Kaplan-Meier analysis demonstrated a significantly higher cumulative probability of not experiencing a new coronary event for the patients without silent ischemia (96.5%) as compared to those with silent ischemia (62.3%) (p < 0.01). Our results suggest that silent myocardial ischemia after a first uncomplicated myocardial infarction carries an adverse prognosis and should be routinely investigated.

Ambulatory (Holter) electrocardiography signal-averaging: a current perspective

Signal-averaging is an emerging new application of the ambulatory ECG. Whereas real-time signal-averaging of the high-resolution ECG has led to the measurement of abnormal QRS complex parameters and to the detection of ventricular late potentials in patients with a history of ventricular tachycardia or fibrillation at increased risk of an arrhythmic event, similar measurements can also be derived from ambulatory ECG tape recordings. This review describes the technical differences between real-time and ambulatory high-resolution ECG signal-averaging, and the early clinical studies that correlated measured QRS complex parameters and defined the agreement of late potential detection with the two technologies. Although there appears to be a promising cost-effective benefit from ambulatory ECG signal-averaging, limitations imposed by the technical differences must be recognized, and additional investigation is needed to define the appropriate clinical use and criteria for best diagnostic and prognostic value.

Comparison of ST depression recorded by Holter monitors and 12-lead ECGs during coronary angiography and exercise testing

Data from previous studies are debatable regarding whether Holter monitors are a reliable electrocardiographic indicator of ischemia, for which the 12-lead electrocardiogram (ECG) is the standard. Simultaneous 12-lead and Holter ECGs were performed on 30 patients with typical angina pectoris during coronary angiography or exercise testing. ST depression recorded by both methods was directly compared, using the 12-lead ECG as the reference. The Holter tapes were also scanned by two automated ST analysis programs and the results were compared to 12-lead ECGs. Only 66 of the 178 12-lead ECG ST depression events were also present on the Holter recordings (37.1% Holter sensitivity). ST depression was underestimated by the Holter recordings compared to the 12-lead ECGs (p < 0.0001). The majority (67.0%) of ST depression events identified by one computer program were false positive events. The degree of ST depression was overestimated compared to 12-lead ECGs by the second program (p = 0.0033). Holter-detected ST depression may not be a reliable ECG indicator of myocardial ischemia.

Transient ST segment depression during Holter monitoring: how to avoid false positive findings

To increase the specificity of 24-hour Holter monitoring in detecting transient myocardial ischemia, we separated genuine ST deviations from those dependent on artifacts by adding a detailed shape analysis of real-time printouts to the usual criteria of significant ST segment depression. We screened 116 apparently healthy subjects; 31 had to be excluded, because of pathologic findings in preliminary examinations. The remaining 85 (49 women and 36 men; mean age, 43.1 years) underwent Holter monitoring for assessment of the extent, frequency, and duration of episodes of horizontal and descending ST segment depression of at least 0.1 mV that persisted for at least 60 msec after the J point and that were at least 1 minute apart. On the basis of these criteria, six subjects (7.1%) showed 24 episodes of horizontal or descending ST segment depression with a mean of 0.2 mV (range, 0.15 to 0.25 mV), a frequency of four episodes per 24 hours (one to nine), and a duration of 12.2 minutes (range 3-range 41 minutes). Supplementary criteria--e.g., sudden onset of ST segment depression, identical orientation of PQ and ST segments, or simultaneous increase in R and P wave amplitude--made it possible to identify ST changes caused by artifacts in four volunteers. In only two subjects (2.4%) could true silent ischemia not be differentiated from false positive results. Thus consideration of only the extent, frequency, and duration of episodes does not permit a differentiation between true silent ischemia and false positive results. A supplementary shape analysis increases the specificity of ST segment analysis in detecting transient myocardial ischemia during 24-hour Holter monitoring.

Efficacy of three-channel ambulatory electrocardiographic monitoring for the detection of myocardial ischemia

The recognition of silent myocardial ischemia (SMI) has been demonstrated to have important clinical relevance. Two-channel ambulatory (Holter) electrocardiographic recording is a commonly utilized method for detecting transient electrocardiographic ST segment changes representative of SMI. It has been suggested that the analysis of two channels alone may not adequately detect SMI. We therefore evaluated the diagnostic yield of three channels using a three-channel electrocardiographic monitoring device in 46 consecutive patients (age 61 +/- 9 years) undergoing percutaneous transluminal coronary angioplasty of an isolated single-vessel stenosis. Modified bipolar chest leads V2, V5, and AVF (CM-V2, CM-V5, and CS-AVF) were utilized for analysis. The percent detection of ST segment changes from various combinations of two-lead recordings were compared to the total three leads, and an absolute transient ST segment shift (STSS) of greater than or equal to 1 mm during balloon inflation was considered as evidence of myocardial ischemia. One patient was excluded because of the need for ventricular pacing during balloon inflation. A total of 33 of 45 patients had STSS in all three leads (percent detection = 73%), while 32 (71%) had STSS in the two-lead grouping with the highest diagnostic yield (CM-V2/CM-V5; p = ns). Of the various two-lead combinations studied, leads CM-V2 and CM-V5 provided the best lead set overall for the detection of ischemic STSS. Three-channel ambulatory electrocardiographic recording only marginally improves upon the detection of ischemia when compared with standard (CM-V2/CM-V5 or CM-V5/CS-AVF) two-channel ambulatory electrocardiographic recordings.

Early postoperative myocardial morbidity in patients with coronary artery disease undergoing major non-cardiac surgery: correlation with perioperative ischaemia

As a part of a study assessing early postoperative myocardial morbidity in 50 patients with active coronary artery disease undergoing major non-cardiac surgery, the ECG was monitored continuously for 24 hr after the onset of anaesthesia, using a frequency modulated (FM) Holter monitor. Concurrent automated blood pressure and pulse were measured non-invasively at three-minute intervals during anaesthesia and subsequently at five-minute intervals. Thirty patients were monitored with two-site ECG recordings, from modified V1 and V5 (Group A). Twenty patients had seventeen-site ECG monitoring, multiplexing a four by four array of precordial electrodes onto one channel of the frequency modulated recorder (Group B). Tapes were analyzed for noise, supraventricular and ventricular dysrythmias, runs of tachy- and bradycardia, and ST segment changes. These data were correlated with serial standard 12-lead ECGs and CK-MB assay in the 72 hr after surgery. Seven tapes from Group A could not be analyzed. Change (greater than 1 mm) on ST monitoring from both Groups A (14/23), B (14/20), correlated with serial 12-lead ECG and/or CK-MB changes. The majority of first ST change 19/28 (70%) occurred after anaesthesia. In 14/28 (50%) ST change occurred during episodes of tachycardia and elevated blood pressure (greater than 20% above baseline). Nine patients (9/23) in Group A had no ST change; however, six had serial 12-lead ECG and/or CK-MB changes. Six patients (6/20) in Group B had no ST changes, and none of these patients had any change of serial 12-lead ECGs or CK-MB assay. No patient complained of chest pain during the Holter monitoring period. Continual monitoring of heart rate and blood pressure and accurate ST monitoring are essential to detect and treat perioperative myocardial ischemia. A multiple-lead precordial system is substantially more sensitive than traditional two-lead ECG holter monitoring in detecting myocardial ischaemia.

How to detect silent myocardial ischemia

Anginal pain alone is not a sensitive marker of ischemia. In one study of 2,014 completely asymptomatic men, 2.5% were found to have silent ischemia when they underwent treadmill exercise testing. Another method of detection, ambulatory electrocardiographic monitoring, can be used in patients who cannot exercise or may be used to clarify results of exercise testing. Many investigators believe that the two tests provide complementary information on the patient's response to high demand and to daily-living activities. Other methods for determining necessary treatment and prognosis include dipyridamole with thallium perfusion scanning, nuclear exercise testing, coronary angiography, and catheterization. The cost, required frequency of retesting, and incidence of false results should be considered before screening is started.