Ambulatory electrocardiographic ST segment changes in healthy volunteers

Long-term prognostic significance of the ST level and ST slope in the 12‑lead ECG in the general population

BACKGROUND

Even minor ST depression in the electrocardiogram (ECG) is associated with cardiovascular disease and increased mortality. There is limited data on the prognostic significance of ST-level changes in the general population.

SUBJECTS AND METHODS

A random sample of Finnish subjects (n = 6354) aged over 30 years (56.1% women) underwent a health examination including a 12‑lead ECG in the Health 2000 survey. The effects of relative ST level as a continuous variable and ST slope (upsloping, horizontal, downsloping) in three different lead groups were analyzed using a multi-adjusted Cox proportional hazard model separately for men and women with total mortality as endpoint.

RESULTS

The follow-up lasted for 13.7 (SD 3.3) years for men and 13.9 (SD 3.1) years for women. Lower lateral ST levels were associated with all-cause mortality in multi-adjusted models in both genders (at J + 80 ms hazard ratio [HR] 0.64 for a change of 1.0 mm [95% confidence interval 0.49-0.84, p = 0.002] for men and HR 0.61 [0.48-0.78, p < 0.001] for women). Associated coronary heart disease had no major influence on the results. Exclusion of subjects with ECG signs of left ventricular hypertrophy from the analyses increased the mortality risk of lower lateral ST levels in men but decreased it in women. For the anterior and inferior lead groups, no statistically significant difference was seen after multivariate adjustment. ST slope was not an independent predictor of mortality after multivariate adjustment.

CONCLUSION

Lower ST level in the lateral ECG leads is an independent prognostic factor to predict all-cause mortality in the general population.

ST-segment changes in high-resolution body surface potential maps measured during exercise to assess myocardial ischemia: a pilot study

INTRODUCTION

The aim of the study was to assess myocardial ischemia by analysis of ST-segment changes in high-resolution body surface potential maps (HR-BSPM) measured at rest and during an exercise stress test.

MATERIAL AND METHODS

The study was carried out on a group of 28 patients with stable coronary artery disease and 15 healthy volunteers. The HR-BSPM were measured at rest and during the exercise stress test on a supine ergometer. The workload was increased in stages by 25 W every 2 min, beginning at 50 W. The maps of ST-segment depression (ST60) were calculated from time averaged recordings at rest and at maximal workload.

RESULTS

The efficiency in detection of myocardial ischemia was higher for HR-BSPM than for standard 12-lead electrocardiography (ECG) when both methods were evaluated by outcomes of coronarography. The sensitivity of HR-BSPM was 82.4% while for the standard 12-lead ECG exercise stress test it was 58.8%. For some patients significant changes in the ST segment were observed at stress HR-BSPM but were not visible in standard 12-lead ECG recorded under the same conditions.

CONCLUSIONS

Obtained high values of sensitivity and specificity in myocardial ischemia detection suggest that maps of ST60 calculated from HR-BSPM can improve detection of patients with ischemic heart disease in comparison to the standard electrocardiographic exercise stress test examinations.

Surgery in patients with coronary artery disease--silent ischaemia during transurethral resection of tumors of prostate or bladder

BACKGROUND

Asymptomatic episodes of myocardial ischemia in clinically stable patients seem to occur frequently and may hint at a worse prognosis.

HYPOTHESIS

This study was undertaken to determine whether surgical patients with coronary artery disease (CAD) have a higher risk of cardiac ischemia during the perioperative period compared with the late postoperative period and compared with patients without CAD.

METHODS

In all, 14 patients with and 14 patients without CAD were examined by Holter monitoring during the perioperative and three days later during the postoperative periods for the presence of ST-segment depression as a marker of silent myocardial ischemia.

RESULTS

While patients without CAD did not show ST-segment depression, patients with CAD were found to have had 143 episodes of ST-segment depression, 49% in the perioperative and 51% in postoperative recordings.

CONCLUSION

Though patients were asymptomatic with antianginal therapy, there were episodes of ST-segment depression indicating silent myocardial ischemia in patients with CAD. Surgical interventions such as transurethral resection of tumors of prostate or bladder did not produce an increase of ischemic burden registered by Holter monitoring.

[Long term electrocardiography (Holter monitoring)]

During the past almost 50 years Holter monitoring has become an established non-invasive diagnostic tool in clinical electrophysiology. It allows ECG recording independent of stationary monitoring facilities during daily life and, therefore, contains much information. In the beginning the main interest was directed towards quantitative and qualitative assessment of arrhythmias, their circadian behaviour, and the circadian behaviour of the heart rate. With advances in technology the analysis spectrum of Holter monitoring expanded, and it was used also for detection of silent myocardial ischaemia. New digital recorders and computers with large capacities made it possible to measure every single heart beat very accurately, which was a prerequisite for heart rate variability and QT-interval analysis, which provided new knowledge about the autonomic modulation of the heart rate and the circadian dynamicity of the QT interval, respectively. Beyond arrhythmia analysis Holter monitoring was increasingly used to assess prognosis in different cardiac conditions. It can also be valuable in assessing transient symptoms possibly related to arrhythmias or device dysfunction, which will not necessarily be revealed by simple device control.

ST segment analysis by Holter Monitoring: methodological considerations

BACKGROUND

There has been a renewed interest in ST segment analysis by Holter Monitoring, especially in multicenter clinical trials, but consensus on how to define an ischemic event is missing. We conducted a survey of European and U.S. publications involving ST segment analysis by Holter monitoring from 1975 to 2002 and found no notation of any correction for baseline ST segment depression in 52% of them. In 45% J-point depression was required in addition to ST segment depression measured either 60 ms (24%) or 80 ms (76%) after the J point. In 28% ST segment elevations were included.

METHOD

Four different criteria for an ischemic event found in our survey were applied to Holter recordings from 66 patients with acute ischemic syndrome enrolled in the Esmolol Myocardial Ischemia Trial (EMIT). Only lead CM5 was used and the analyzer was a Reynolds Medical Pathfinder 600.

RESULTS

By the most sensitive method (J + 80), there were 16 (24%) patients who had ischemic events in their Holter recording compared to only 10 (15%) patients if J-point depression was also required. If corrections were made for baseline ST segment depression, only 3 (4.5%) recordings were positive for ischemia.

CONCLUSION

The outcome of Holter analysis for ischemic events is greatly dependent upon how an ischemic event is defined. Consensus on how to define an ischemic event is urgently needed.

Silent ischaemia and hypertension

For many years now, silent ischaemia has been recognized as a distinct clinical entity, and its relevance in different patient groups has been established. However, a number of basic questions have not been answered. In explaining the pathophysiology of silent ischaemia, factors affecting both the demand and the supply side are now being recognized. With the exception of certain well-defined groups, it is not clear why some patients are mostly symptomatic, while other patients are predominantly asymptomatic. There appear to be many factors influencing the ischaemic pain threshold. Studies investigating the prevalence of silent ischaemia show a remarkably high prevalence of silent ischaemia in different patient groups. Patients with hypertension but without coronary artery disease form a specific and vulnerable high-risk population that is particularly prone to silent ischaemia. Since changes at the macrovascular level are not responsible, various factors negatively influencing either cardiac supply or demand have been investigated. A reduced coronary reserve is central in explaining the increased prevalence of silent ischaemia in hypertensives. Left ventricular hypertrophy renders meaningful detection of ST segment changes difficult, but a possible solution dealing with this problem is offered by applying more stringent criteria in terms of minimal ST depression in the definition of ischaemia. The treatment of silent ischaemia is largely the same as for angina pectoris, but whether therapy should be directed at elimination of all ischaemic episodes or only of symptomatic episodes depends on further prospective work addressing this question.

ST-segment deviation during 24-hour ambulatory electrocardiographic monitoring and exercise stress test in healthy male subjects 51 to 75 years of age: the Copenhagen City Heart Study

BACKGROUND

Although ST-segment deviation has been evaluated and used during many years both on continuous electrocardiographic Holter monitoring and during exercise stress testing, considerable controversy still remains concerning the prevalence and diagnostic significance of fortuitously discovered ST-segment deviation in asymptomatic healthy persons.

METHODS AND RESULTS

The occurrence of ST-segment deviation was studied in a population of 63 clinically healthy male subjects 51 to 75 years of age, with the use of 24-hour Holter monitoring and exercise stress testing. The subjects were recruited from the Copenhagen City Heart Study and were without cardiovascular risk factors, chronic diseases, or medication and without cardiovascular events during 5 to 12 years before and 3 to 5 years after admission. The specificity, that is, the probability of displaying a negative test result in healthy subjects without disease, was 1.0 when using as criterion for significant ST-segment deviation a horizontal or descending ST-segment depression of >0.20 mV or ST-segment elevation >/=0.15 mV during Holter monitoring, and acceptable, for example, 0.95, when using as criterion a horizontal or descending ST-segment depression of >/=0.15 mV during Holter monitoring or at the exercise test, respectively. Furthermore, the specificity was 0.95 when a horizontal or downsloping ST-segment depression of 0.1 mV was displayed in both the Holter and exercise electrocardiographic recording system.

CONCLUSIONS

Thus in asymptomatic persons, the usual criterion for significant ST-segment depression of 0.1 mV can be applied when occurring in both electrocardiographic recording systems. However, if one test alone is used, the criterion of significant ST-segment depression should be 0.15 mV. Absence of ST-segment deviation during Holter monitoring and exercise stress testing, indicated with a specificity of 1.0 or 0.95 according to choice of criterion, implies that the person is in a healthy state.

Neurogenic ST depression in stroke

BACKGROUND

Stroke is occasionally associated with ECG repolarization changes including ST depression. Recent evidence suggests a neurogenic contribution to these abnormalities in stroke patients. Animal studies implicate the insular cortex in cardiovascular control. We describe a patient with a left insular infarct and without cardiac or coronary artery disease, who developed ST depression indicating a neurogenic etiology.

CASE DESCRIPTION

A 48 year-old female, with no risk factors for stroke, developed sudden expressive aphasia. MRI brain showed an infarct in the left insular cortex. Twenty-four hour Holter monitoring on the third day revealed transient ST depression more than 1.5 mm, which was not reproducible on subsequent monitoring. Transesophageal echo-cardiography (TEE) was normal. She had no cardiac symptoms and serial ECGs, cardiac enzymes (CKMB) and adenosine thallium scan were normal. To-date, there had been no cardiac events like congestive heart failure or myocardial ischemia.

CONCLUSION

These findings suggest neurogenic ST depression is related to the left insular infarct in view of the normal adenosine thallium scan, non-reproducibility and evanescence of the ST segment changes and lack of associated cardiac symptoms. When neurogenic ST depression is combined with underlying coronary artery disease, it may adversely influence cardiac outcome after stroke.

Peri-operative silent myocardial ischaemia in patients undergoing lower limb joint replacement surgery: an indicator of postoperative morbidity or mortality?

One hundred and twenty-seven patients undergoing major lower limb joint replacement surgery were studied to determine the incidence of silent myocardial ischemia and to ascertain any link between pre-operative cardiac risk factors, silent myocardial ischaemia and postoperative morbidity. Patients underwent ambulatory ECG monitoring for 4 days (on the pre-operative night and for 3 days postoperatively). Postoperative cardiorespiratory symptomatology and morbidity was assessed by questionnaire at 3 months. Eighty-seven patients had risk factors for silent myocardial ischaemia; 42 patients (30 with risk factors) had peri-operative silent myocardial ischaemia. The median ischaemic loads (range) were 1.04 (0.32-13.31) min.h-1 pre-operatively and 5.53 (0.26-56.39), 6.69 (0.04-42.71) and 1.23 (0.1-53.74) min.h-1 on postoperative days 1-3, respectively. Risk factors did not predict the occurrence of silent myocardial ischaemia or an increased ischaemic load pre-operatively or overall postoperatively. New symptoms (chest pain, palpitations, breathlessness or fatigue) were associated with both silent myocardial ischaemia and ischaemic load (p < 0.05). Thus cardiac risk factors do not predict the occurrence of silent myocardial ischaemia or adverse outcome. Peri-operative silent myocardial ischaemia was associated with increased postoperative fatigue.

Cardiac risks in total hip replacement

During total hip replacement, identifiable myocardial ischemia occurs intraoperatively, indicating myocardial strain. Coronary heart disease (CHD) patients are at risk during this type of surgery. Perioperatively, CHD patients had significantly longer ST depressions than patients not suffering from CHD (3348 min vs 454 min). The number of depression episodes was also significantly higher for CHD patients (160 vs 36). Comparing the perioperative with the postoperative stage demonstrated that CHD patients experienced a highly significant shift towards shorter periods of ST-segment depression postoperatively.

Spontaneous changes of heart rate, blood pressure, and ischemia-type ST-segment depressions in patients with hypertension without significant coronary artery disease: beneficial effects of beta-blockade

In hypertensives, a reduced coronary flow reserve is observed and may contribute to angina pectoris and silent (painless) myocardial ischemia, which frequently occur in these patients even in the absence of coronary artery disease (CAD). To assess the frequency of ischemia-type ST-segment depressions in these patients and the influence of heart rate (HR) and blood pressure (BP) as major determinants of myocardial oxygen demand and to test the effects of beta-blocker therapy (10-20 mg betaxolol/day for 4 weeks) on these variables, simultaneous 24-h Holter and 24-h ambulatory BP monitoring was performed in 19 patients with hypertension (age, 43-71 years; nine women, 10 men) without CAD (stenosis < 50% in angiography). Before treatment, 25 periods of significant ST-segment depressions with a total duration of 470 min were observed in nine patients. ST-segment depressions were significantly correlated with preceding increases in HR and the rate-pressure product. The majority (79%) of episodes with ST-segment depression were clinically painless. In this open study, beta-blockade significantly decreased the number of episodes with ST-segment depressions to six in four of 15 patients and the total duration to 38 min (p < 0.05). The data demonstrate that HR seems to be associated with the development of ischemic ST-segment deviations in patients with hypertension without CAD. Antihypertensive therapy in these patients should target not only sufficient BP control, but also reduction of ischemic events.

Ischemia monitoring with on-line vectorcardiography compared with results from a predischarge exercise test in patients with acute ischemic heart disease

Information from 24-hour monitoring with on-line vectorcardiography, starting immediately after admission, was compared with results from a predischarge exercise test 3-13 days after admission. A total of 169 patients with acute myocardial infarction and 73 patients with unstable angina pectoris were investigated. Patients were followed for 487 +/- 135 days. During the follow-up period, 19 patients (8%) died from cardiac causes and 34 (14%) were hospitalized for a myocardial infarction. The QRS vector difference (QRS-VD), ST change vector magnitude (STC-VM), ST vector magnitude (ST-VM), and ST vector leads X, Y, Z were monitored. Patients with ST depression on the exercise test showed higher occurrence of transient, supposedly ischemic, episodes of QRS-VD, STC-VM, and ST-VM than patients without ST depression. The sensitivity and specificity of identifying patients with ST depression at the exercise test were respectively, 71 and 47% for QRS-VD episodes, 58 and 56% for ST-VM episodes, and 55 and 65% for STC-VM episodes. The maximum ST depression at the exercise test was related to the maximum ST depression in vector lead X (r = .44, P < .001) and the number of STC-VM (r = .40, P < .001), ST-VM (r = .37, P < .001), and QRS-VD (r = .33, P < .001) episodes on the VCG. In multivariate analysis, maximum ST depression in vector lead X and STC-VM episodes were the best determinants for ST depression at the exercise test. In a Cox regression model, the optimal combination of exercise test data in patients who died from cardiac causes exhibited a global chi-square value of 20.0. The combination of these data and the number of STC-VM episodes increased the global chi-square value to 30.6. This study indicates that in patients with acute ischemic heart disease, early continuous vectorcardiographic monitoring may predict the results from a predischarge exercise test and also contributes independent prognostic information beyond that of exercise test data.

ST-segment depression on ambulatory electrocardiography in the early in-hospital period after acute myocardial infarction predicts early and late mortality: a short-term and a 3-year follow-up study

A surveillance study was conducted to determine the in-hospital and long-term prognostic value of ST-segment depression assessed by ambulatory electrocardiographic monitoring (AEM) during the early in-hospital period after acute myocardial infarction (AMI). ST-segment depression (STD) was determined by computer analysis of 24-h ECG tapes as a horizontal or downsloping change in ST level by > 0.1 mV from the reference base line. The ST level was measured 80 ms after the J point of all normally conducted complexes for > or = 1 min. All computer-detected ST events were verified by one trained reader. Tapes corresponding to 74 patients were analyzed. In addition, 23 tapes corresponding to age- and gender-matched controls were also analyzed. Patients were divided into two groups: 22 patients (30%) showed STD (Group A), and 52 patients (70%) had no episode of STD (Group B). Among controls, 1 person (4%) showed STD. During the early follow-up period (14 +/- 11 days after hospital admission), cardiac events occurred in 11 patients [7 (32%) in Group A and 4(8%) in Group B, p < 0.01], including 6 cardiac death [5 (23%) in Group A and 1 (2%) in Group B, p < 0.01], 3 acute coronary artery bypass surgeries [2 (9%) in Group A and 1 (2%) in Group B, p = NS], and 2 nonfatal myocardial infractions (both in Group A, p = NS). During a mean follow-up period of 3 years (36 +/- 15 months), 18 patients died [10 (45%) in Group A and 8 (15%) in Group B, p = 0.01]. Eleven deaths were sudden [7 (32%) in Group A and 4 (8%) in Group B, p < 0.01]. Eighteen AMI occurred [11 (50%) in Group A and 7 (13%) in Group B, p < 0.005]. Twenty patients underwent revascularization procedures [7 (32%) in Group A and 13 (25%) in Group B, p = NS].(ABSTRACT TRUNCATED AT 250 WORDS)

ST segment and T wave characteristics as indicators of coronary heart disease risk: the Zutphen Study

OBJECTIVES

This study evaluated the predictive value of T wave amplitude and ST segment level on lead I for angina pectoris, a first myocardial infarction, sudden death and coronary heart disease death in middle-aged and elderly men.

BACKGROUND

Certain ST-T wave characteristics may reflect favorable autonomic cardiac control. Slight ST segment elevation has been reported to indicate a low risk of coronary heart disease mortality.

METHODS

A total of 876 men, born between 1900 and 1920, participated in periodic medical examinations and were followed up with respect to morbidity and mortality from 1960 to 1985. In 1985, the remaining cohort was extended to 836 elderly men from the same birth cohort who were followed up until 1990. Relative risks in categories of T wave amplitude and ST segment level were estimated by survival analysis.

RESULTS

Both middle-aged and elderly men with T wave amplitudes > or = 0.15 mV had a lower risk of myocardial infarction, coronary heart disease death and sudden death than men with T wave amplitudes 0.05 to 0.15 mV. The adjusted relative risk of coronary heart disease death was 0.5 (95% confidence interval [CI] 0.2 to 1.0); in men with T wave amplitude < or = 0.05 mV, relative risk was 2.0 (95% CI 1.3 to 3.1). Slight ST segment elevation was also associated with decreased risk: relative risk 0.5 (95% CI 0.3 to 1.0) compared with the isoelectric ST segment level. In men with ST segment depression, relative risk was 2.2 (95% CI 1.4 to 3.4). The association of T wave amplitude and ST segment level were independent of each other.

CONCLUSIONS

In addition to the elevated risk of coronary heart disease that is associated with ST-T wave abnormalities, we observed that normal variations in repolarization characteristics are predictive of future heart disease.

ST segment depression detected by continuous electrocardiography in patients with acute ischemic stroke or transient ischemic attack

BACKGROUND AND PURPOSE

Forty percent of patients with a history of ischemic stroke or transient ischemic attack (TIA) have concomitant coronary artery disease. ST segment depression, detected by continuous electrocardiography, is associated with increased cardiac morbidity and mortality in patients with known coronary artery disease. While electrocardiographic changes have been associated with acute stroke, the etiology and significance of these changes remain unclear. In this pilot study we report the prevalence of ST segment depression and ventricular arrhythmias in patients with acute ischemic stroke or TIA monitored by continuous electrocardiography. Clinical predictors of ST segment depression and ventricular arrhythmia are also identified.

METHODS

Consecutive patients presenting with acute ischemic stroke or TIA were enrolled within 72 hours of hospital admission and monitored by continuous electrocardiography for 48 hours. The electrocardiographic results were analyzed for periods of ST segment depression and ventricular arrhythmias.

RESULTS

Of 51 patients with ischemic stroke or TIA, 15 (29%) had episodes of ST segment depression (95% confidence interval, 15% to 43%), and 18 (35%) had ventricular arrhythmias (95% confidence interval, 21% to 49%). In logistic regression analysis, increasing age (P < .02) and a left-sided neurological event (P < .01) were significant predictors of ST segment depression. Increasing numbers of atherosclerotic risk factors, a history of cardiac disease, and increasing or decreasing mean arterial pressure were not predictive of ST segment depression.

CONCLUSIONS

Patients with acute ischemic stroke or TIA have a 29% prevalence of ST segment depression within the first 5 days after their event. In comparison, the prevalence of ST depression is 2.5% to 8% in asymptomatic adults and 43% to 60% in patients with symptomatic coronary artery disease. The association of ST segment depression with left-sided neurological events suggests that the electrocardiographic changes are in part neurologically mediated. Further study is necessary to better define the brain-heart interaction and to determine whether ST segment depression in patients with ischemic stroke or TIA reflects underlying coronary artery disease.

12-lead and continuous ECG recordings of subjects during inpatient administration of smoked cocaine

Cocaine can cause myocardial ischemia or infarction. The incidence of these events, and the influence of specific dosing routes or regimens on their occurrence is not established. In the current study, we obtained frequent 12-lead electrocardiograms (ECGs) and continuous 2 or 3 channel ECGs from 20 subjects participating in a behavioral study of smoked cocaine. Subjects received 10 or 11 doses of cocaine 0.4 mg/kg per dose, or 10 doses of 35 mg per dose at 30 min intervals (range 233-408 mg total dose per session). ECGs were also recorded on control days on which subjects received no cocaine. The mean peak plasma cocaine concentration on cocaine days was 640 +/- 262 ng/ml. There were no changes in digitized ST segment amplitude on 12-lead ECGs obtained during cocaine administration (P = 0.098). Of 17 subjects who had technically satisfactory continuous ECGs, four had significant ST segment depression (> 1 mm below the PR segment); two on cocaine days and two on control days (P > 0.5). One subject had frequent premature beats on both cocaine and control days. One subject had an asymptomatic run of 4 ventricular beats 30 s after cocaine administration that could have been due to cocaine. All episodes of ST depression or premature beats were asymptomatic. No evidence of either symptomatic or subclinical cardiac ischemia related to cocaine administration was found. Thus no clinically important adverse events were found as a result of smoked cocaine administered by this dosing regimen to healthy males with a history of heavy cocaine use. Additional study with larger numbers of subjects will be helpful in further assessing the safety of administering smoked cocaine to research subjects.

Mechanism of angina pectoris in patients with systemic hypertension and normal epicardial coronary arteries by arteriogram

Patients with arterial hypertension frequently have angina pectoris despite a normal coronary angiogram. This angina pectoris syndrome often goes along with an impaired coronary vasodilator reserve. The aim of the study was to find out whether an impaired coronary flow reserve is associated with electrographic signs of transient myocardial ischemia. Forty-three hypertensive patients not taking cardiovascular medication were studied with 24-hour Holter monitoring. Coronary blood flow and resistance were measured before and after intravenous administration of dipyridamole (0.5 mg/kg body weight). Coronary reserve was determined as the relation of coronary resistance before and after dipyridamole. For control purposes 9 normotensive subjects were studied with the same protocol. Hypertensive patients with ST-segment depressions (n = 31) had a significantly impaired coronary reserve (2.3 +/- 0.5) compared with normotensive subjects (4.9 +/- 1.0, p < 0.01). Coronary reserve in hypertensive patients without ST-segment depressions was only slightly impaired (4.0 +/- 1.8). Arterial pressure and left ventricular mass did not differ between hypertensive patients with and without ST-segment depressions. Left ventricular mass had no effect on coronary reserve. It is concluded that neither left ventricular hypertrophy nor arterial pressure were determinants for ST-segment depressions. Consequently primary functional and structural alterations on the level of the microcirculation appear to be responsible for the occurrence of transient ischemic episodes in the Holter electrocardiogram.

Ambulatory ST-recording has no additional value to exercise test for identification of severe coronary lesions after an episode of unstable coronary artery disease in men

One month after an episode of unstable coronary artery disease, 95 male patients performed coronary angiography, 48 hours ambulatory ST-recording and also an exercise test. ST-depression occurred in 29.5% during the ST-recording and in 44.2% during the exercise test (p < 0.05). In patients with ST-depression at ambulatory monitoring, 79% demonstrated the same finding at the exercise test. A high risk response at the exercise test--defined as either ST-depression in > or = 3 leads, ST-depression in 1-2 leads with a maximal work load below the 60th percentile or a maximal work load below the 30th percentile regardless of the ECG reaction--occurred in 56.8%. Severe coronary lesions--defined as three vessel disease, left main stenosis or proximal left anterior descending artery stenosis as part of two vessel disease--was observed in 46.3%. Patients with a high risk exercise test response and patients with ST-depression during ST-recording had severe coronary lesions in 67% and 64% respectively. However, a high risk exercise test response occurred in 82%, while ST-depression at ambulatory monitoring was observed only in 41% of the patients with severe coronary lesions (p < 0.001). Thus, ambulatory ST-recording one month after an episode of unstable coronary artery disease in men adds no further information to a symptom limited exercise test in order to identify patients with severe coronary lesions.

Significance of ST-segment elevation during ambulatory monitoring after acute myocardial infarction

The significance of ST segment elevation during ambulatory monitoring after acute myocardial infarction was examined in 203 patients. Ambulatory monitoring was performed both early (mean 6.4 days [range 3 to 15]; N = 201) and late (38 days [range 22 to 93]; N = 177), and 174 patients underwent exercise treadmill testing (38 days [range 22 to 93]). Cardiac events (death, reinfarction, and coronary revascularization) were documented during a 1-year follow-up period. ST elevation (all silent) occurred in 25 of 201 patients (12%) on early monitoring but in only 4 of 177 (2%) on late monitoring (p < 0.001). Compared with patients (N = 148) without any ST deviation, those with early ST elevation had more pericarditis (8/25 [32%] vs 23/148 [16%]; p = 0.089) but no more angina or exercise ischemia. The mortality rate tended to be higher in patients with early ST elevation (4/25 [16%] vs 10/148 [7%]; p = 0.24), but ST elevation was too infrequent to be a valuable prognostic indicator. ST elevation is not uncommon during ambulatory monitoring early after myocardial infarction but is rare during later monitoring. Such ST elevation is almost always silent, does not usually reflect myocardial ischemia, and is not a useful prognostic indicator.

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.

Well shaped ST segment and risk of cardiovascular mortality

OBJECTIVE

To investigate the prognostic value of frequently occurring slight variations in the ST segment for cardiovascular mortality in healthy subjects.

DESIGN

Follow up study of mortality in relation to variations in ST segment level in a cohort over the 28 years from 1953 to 1981. A case-cohort sampling design was applied to limit the number of electrocardiograms that had to be coded by hand.

SETTING

General health examination carried out in 1953 of civil servants in Amsterdam and assessment of subsequent mortality.

SUBJECTS

Apparently healthy civil servants aged 40 to 65 years: 1583 men and 1508 women.

MAIN OUTCOME MEASURES

Relative risk of variations in ST segment level for mortality from all causes, cardiovascular disease, and coronary heart disease.

RESULTS

In men the multivariate relative risks of 15 year mortality from cardiovascular disease and coronary heart disease of slight ST elevation at 80 ms past the J point (compared with isoelectric ST segment) were 0.5 (95% confidence interval 0.3 to 0.9) and 0.4 (0.2 to 0.8), respectively. As expected, ST segment depression (greater than 0.25 mm) was associated with increased risk: 1.9 (1.1 to 3.0) and 2.2 (1.2 to 3.9), respectively. In women associations were weaker. The full 28 year period showed a similar pattern of somewhat weaker associations for men; among women, however, no predictive value was apparent.

CONCLUSION

These results are empirical evidence for the intuitive opinion among doctors that a curved, upward sloping ST segment, resulting in slight ST elevation at 80 ms, indicates low risk compared with the isoelectric flat, stretched ST segment.

Circadian variation of heart rate is affected by environment: a study of continuous electrocardiographic monitoring in members of a symphony orchestra

Twenty four hour ambulatory ST segment monitoring was performed on 48 members (43 players and five members of the management/technical team) of the British Broadcasting Corporation (BBC) symphony orchestra without a history of cardiac disease. This period included final rehearsals and live performances (for audience and radio) of music by Richard Strauss and Mozart at the Royal Festival Hall (n = 36) and Rachmaninov and Tchaikovsky at the Barbican Arts Centre (n = 21). During the period of monitoring one person (2%) had transient ST segment changes. Mean heart rates were significantly higher during the live performances than during the rehearsals. Mean heart rates during the live performance of Rachmaninov and Tchaikovsky were significantly higher than during Strauss and Mozart in those (n = 6) who were monitored on both occasions. Mean heart rates in the management and technical team were higher than those of the players. The recognised circadian pattern of heart rate, with a peak in the morning waking hours, was altered similarly during both concert days, with a primary peak occurring in the evening hours and a lesser peak in the morning for both musicians and management/technical staff. This study showed that environmental factors are of primary importance in defining the circadian pattern of heart rate. This has important implications when identifying peak periods of cardiovascular stress and tailoring drug treatment for patients with angina pectoris.

Total ischemic burden in patients with coronary artery disease

In patients with coronary artery disease, angina pectoris provides an unreliable underestimation of disease activity and risk. Unheralded myocardial infarction and sudden death are common clinical presentations. Furthermore, objective testing, in hospital and more recently during the patient's normal daily activities, has demonstrated frequent and asymptomatic episodes of ischemia, as indicated by transient ST-segment depression. Since the underlying pathophysiologic disturbances of myocardial perfusion appear to be similar in painful and painless episodes, it seems appropriate to consider them together as the "total ischemic burden" on the myocardium. Research into this functional expression of coronary disease has indicated that active ischemia is associated with an increased risk of morbid events in all clinical subgroups of patients, including those with stable angina, unstable angina, peripheral vascular disease and following myocardial infarction. If this is confirmed in prospective trials, the assessment of total ischemic burden is likely to become part of the clinical investigation of patients with coronary disease. Clinical trials testing the efficacy of interventions will need to examine the effect on ischemic activity during normal daily life, in addition to symptoms and exercise tolerance. Evidence is still required to demonstrate whether therapy aimed at reducing the total ischemic burden will prolong life. The total ischemic burden provides a marker to follow the dynamic changes of the atherosclerotic lesion. Future research may have to concentrate on treatment aimed at altering the natural history of obstructive coronary atherosclerosis in order to affect the long-term outlook for patients with coronary artery disease.

Transient myocardial ischemia in hypertensive heart disease

This study determined whether episodes of myocardial ischemia occur in hypertensive patients with normal coronary angiograms. ST-segment analysis during 24-hour Holter electrocardiography was determined in 48 patients (24 men and 24 women, mean age 54.6 +/- 10.4 years) with essential arterial hypertension (systolic/diastolic blood pressure 189.7 +/- 29/99.5 +/- 15 mm Hg). The thickness of left ventricular posterior wall and septum were measured with echocardiography. Stenosis of coronary vessels were excluded on angiography in all patients. In 24 of 48 patients, 12.8 +/- 13.8 episodes of transient myocardial ischemia (ST-segment depression greater than or equal to 1 mm, duration of the episode greater than or equal to 1 minute) were observed. The duration of the episodes was 48.1 +/- 69.93 minutes and the maximal ST-segment depression was 1.91 +/- 0.82 mm. In 95% of the episodes the patients did not experience any angina pectoris. The degree of left ventricular wall thickness did not differ in hypertensive patients with and without transient myocardial ischemia (septum thickness 11 +/- 2 mm). It is concluded that transient myocardial ischemia often occurs in hypertensive patients. Thus, left ventricular hypertrophy does not appear to play any important role. The underlying cause appears to be the impaired coronary dilation capacity, i.e., vascular alterations.

Identification of a high risk subgroup of patients with silent ischaemia after myocardial infarction: a group for early therapeutic revascularisation?

Asymptomatic ("silent") ischaemia has been shown to be of prognostic significance in patients with stable and unstable angina and more recently in patients recovering after myocardial infarction. No therapeutic regimen has yet been shown to improve the prognosis of patients with silent ischaemia after infarction, which can be found in as many as a third of these patients. Attempts to achieve therapeutic revascularisation in all these patients may be undesirable, but early revascularisation could be especially beneficial in some selected high risk patients. Two hundred and fifty consecutive clinically stable survivors of myocardial infarction who had predischarge submaximal exercise tests were followed up for a year. Silent ischaemia was found in 27% of these patients; 15% had symptomatic ischaemia. Patients with a positive exercise test were prescribed a beta blocker before discharge. Mortality in patients with silent (9.4%) and symptomatic (5.4%) ischaemia in the first year after infarction was not significantly different. Patients with symptomatic ischaemia were more likely to have undergone coronary artery bypass grafting in the first year. Patients with silent ischaemia were, however, significantly more likely to die than patients with a negative exercise test (relative odds 12:1). Patients with silent ischaemia and an abnormal blood pressure response or who could not complete a submaximal exercise protocol were at particularly high risk, being 32 times more likely to die than those with a negative test (95% confidence interval from 3.3 to 307 times more likely). First year mortality in this group was 22%. The benefits of therapeutic revascularisation in this high risk group need to be studied.

Computerised evaluation of the electrocardiogram during and for a short period after gall bladder surgery

Long-term ECG recording on tape (LTER) was performed in 32 consecutive patients undergoing cholecystectomy. Twenty-two of the patients recorded showed ST-segment changes during the per- and early post-operative period. ST-segment depression was the most common change seen in 17 patients; however, 12 patients showed ST-segment elevation. In only nine patients were the ST-segment changes seen to be associated with major changes in pulse or blood pressure. ST-segment changes were seen as frequently in patients with, as without, known cardiovascular disease. All patients had an uncomplicated postoperative course and no case of myocardial infarction was seen. ST-segment changes during elective surgery seem to be a common phenomenon. The etiology of the observed changes is not clear and its value in the detection of per- or postoperative myocardial ischemia needs to be further evaluated.

Ambulatory (Holter) electrocardiography and myocardial ischemia

Ambulatory (Holter) electrocardiography has evolved over the past two decades to allow accurate assessment of the cardiac rhythm, and more recently, accurate detection and measurement of ST segment changes. These ambulatory ECG ST segment changes that occur with and without symptoms, although thought to be of questionable clinical value for many years, have recently been clearly documented in coronary artery disease patients to represent true myocardial ischemia. Concurrent with these technologic developments has been an evolution of the pathophysiologic understanding of myocardial ischemia, and the relative role and sequential nature that ECG ST segment changes have in its development. This review examines from a clinical perspective the current understanding of the pathophysiologic sequence of development of myocardial ischemia, emphasizes the ECG diagnostic methods that detect this sequential change, examines the criteria that define ambulatory ECG myocardial ischemia, and discusses those nonischemic factors that affect the ECG ST segment and its interpretation. Moreover, an ever increasing number of ambulatory ECG studies of coronary artery disease and normal patients have defined unique characteristics of the ambulatory ECG ST segment changes observed with regard to its diagnostic, prognostic, and therapeutic assessment value in the study of myocardial ischemia.

Silent myocardial ischemia in asymptomatic survivors of unrecognized myocardial infarction and matched controls

Although silent myocardial ischemia (SI) occurs frequently in patients with angina and is of prognostic significance, little is known of its occurrence in other subgroups. We assessed the incidence of SI in offspring of Framingham Heart Study (FHS) patients following unrecognized myocardial infarction (UMI) and in controls without MI but who were matched for age, sex, hypertension, diabetes, smoking, and total cholesterol at entry into the FHS. Of the 20 UMI patients, six had died and one with left bundle branch block was excluded. The remaining 13 UMI patients and 26 control patients underwent 24-hour ambulatory electrocardiographic monitoring (AECG) for SI. Two patients (one from each group) with angina were excluded from the AECG analysis. Only two (15.4%) of the UMI patients and two (7.7%) of the control patients had any AECG evidence of SI. These preliminary results suggest that routine monitoring for SI is not indicated in asymptomatic long-term survivors of UMI or in asymptomatic patients without prior MI but with otherwise similar risk profiles.

Silent myocardial ischemia: an update

Silent myocardial ischemia is diagnosed by several different techniques and has been documented in all the anginal syndromes. In addition to other factors, its presence may be related to increased pain threshold and increased pain tolerance. Although some patients with painless ischemia may have less extensive coronary artery disease, cumulative evidence indicates that silent myocardial ischemia does not necessarily signify a lesser degree of cardiac ischemia or a less severe coronary abnormality. As judged by ambulatory monitoring studies, it shows circadian variation; occurs more frequently than symptomatic ischemia; and appears to depend, in large part, on activation of the sympathetic nervous system. Frequent silent ischemic events during ambulatory monitoring are worrisome because they reflect the disease "activity" of single or multiple coronary atherosclerotic lesions. Thus, there may be a direct association between the severity of ischemia seen during Holter monitoring, the extent of underlying coronary artery disease or disease activity, and prognosis. When diagnosed by exercise testing, silent myocardial ischemia may be associated with significant coronary involvement. In this regard, patients with three vessel coronary disease, impaired left ventricular function, and silent ischemia during stress testing should benefit from coronary revascularization. Compared with symptomatic patients, other evidence suggests that patients with exercise-induced asymptomatic ischemia have at least the same or perhaps even a worse outlook; this may be related to the lack of symptoms that would prompt evaluation and therapy. Awareness of the possibility of silent myocardial ischemia and use of commonly available tests, both to establish its presence and severity and to guide treatment, are emerging as new clinical goals. Further data, however, are necessary to determine how vigorously this should be pursued in different patient subgroups. In association with unstable angina or post-myocardial infarction, the added risk of silent myocardial ischemia warrants a more aggressive approach.

The ST segment of the ambulatory electrocardiogram in a normal population

The behaviour of the ST segment in everyday life was studied by ambulatory electrocardiography in 111 normal volunteers. Fifteen were excluded because of abnormal exercise responses (10 subjects) and significant postural ST segment shifts (five subjects). This left 62 men and 34 women, mean (SD) age 40.5 (12.6) years (range 20-67 years). Ambulatory monitoring of leads CM5 and CC5 for 24 hours was followed by a maximal treadmill exercise test. The tapes of the ambulatory monitoring were analysed by a computer aided system. The computer printed trend plots of the ST segment (measured both at the J point and at J + 60 ms) to detect episodes of ST segment elevation and depression, which were confirmed by visual analysis of real time printouts. Twelve subjects showed "ischaemic" ST segment depression and nine subjects showed ST segment elevation. Eight people with ambulatory ST segment changes were studied during exercise by radionuclide ventriculography and thallium-201 imaging scans. Although seven of the eight thallium studies were normal, radionuclide ventriculography showed functional impairment in five cases. Seven of the 10 subjects with abnormal exercise tests were similarly investigated and their results followed the same pattern, with normal thallium images in six and functional impairment in four. Ambulatory electrocardiography was repeated in 20 people after a median of 20 days. The ST segment changes were reproducible. ST segment changes of an apparently ischaemic nature occur even in a carefully defined normal population but they do not necessarily represent latent clinically significant coronary artery disease. This indicates that ST segment changes seen in patients with known obstructive coronary artery disease should be interpreted with caution.

Calcium channel antagonists. Part II: Use and comparative properties of the three prototypical calcium antagonists in ischemic heart disease, including recommendations based on an analysis of 41 trials

An analysis of 41 trials of angina of all varieties confirms that calcium antagonists are an important advance and are now established therapy for these syndromes. In effort angina, verapamil in a dose of 360-480 mg daily is better than propranolol in standard doses. Although nifedipine is highly effective against vasospastic angina, its use in threatened myocardial infarction or severe unstable angina is not supported by recent studies, unless combined with a beta-blocker. Diltiazem has recently been tested with apparent benefit in non-Q-wave myocardial infarction. Otherwise, these calcium antagonist agents all seem to have approximate equipotency in clinical ischemic syndromes including effort and vasospastic angina. Subjective side effects seem most troublesome in the case of nifedipine. All three calcium antagonists, especially nifedipine, have been successfully combined with beta-blocker therapy, yet occasional additive negative inotropic or chronotropic or dromotropic interactions may occur when verapamil or diltiazem is added to beta-blockade, and occasionally the direct negative inotropic potential of nifedipine may become evident. The choice between the calcium antagonists is determined not only by the clinical picture but also by the anticipated side effects in a given patient and by the overall cardiovascular status. In patients with supraventricular tachycardias or sinus tachycardia, verapamil or diltiazem is preferred, whereas in patients with a resting bradycardia or borderline heart failure nifedipine is likely to be chosen.

Continuous recording of coronary sinus oxygen saturation during atrial pacing in patients with coronary artery disease or with syndrome X

Coronary sinus oxygen saturation was measured continuously during incremental atrial pacing in 34 patients undergoing cardiac catheterisation. In eleven patients with normal coronary arteriograms, negative exercise tests, and no ST segment depression on the electrocardiogram, an increase in the rate of atrial pacing transiently decreased coronary sinus oxygen saturation but within 20 s oxygen saturation returned to the control value. In six patients with coronary artery disease ST segment depression developed during atrial pacing. The coronary sinus oxygen saturation fell and remained reduced until pacing was discontinued. The size of the fall of coronary sinus oxygen saturation increased with increasing heart rate. In seven patients with coronary artery disease the ST segments were unaltered during atrial pacing and coronary sinus oxygen saturation did not fall. Ten patients with syndrome X were studied. In six ST segment depression developed on atrial pacing. In five, three of whom developed ST segment depression, the changes in coronary sinus oxygen saturation during atrial pacing were similar to those observed in patients without any evidence of coronary artery disease. In three, all of whom developed ST segment depression, coronary sinus oxygen saturation gradually increased throughout the period of atrial pacing. In two patients coronary sinus oxygen saturation fell in a manner similar to that observed in patients with obstructive coronary artery disease who developed ST segment depression on pacing. Thus regulation of coronary blood flow in normal persons in response to an increase of heart rate is rapid. Oxygen extraction across the coronary bed can increase by up to 30% and a persistent increase in oxygen extraction is an indicator of myocardial ischaemia. The term "syndrome X" does not describe a homogeneous group of patients but in the majority coronary sinus oxygen saturation does not fall despite symptoms and changes on the electrocardiogram, indicating that inadequate coronary blood flow is not the dominant mechanism.

Ambulatory heart rate and ST-segment depression during painful and silent myocardial ischemia in chronic stable angina pectoris

The relation between heart rate and ischemic ST-segment depression was studied in 70 patients with documented obstructive coronary artery disease (CAD) and reproducible effort angina. Symptom-limited treadmill exercise testing was performed before and after a 2-week placebo period and 24-hour FM ambulatory electrocardiographic monitoring at the end of the placebo period. The means (+/- standard deviation) of the basal and placebo values for exercise time, heart rate and maximal ST-segment depression were: 6.4 +/- 2.6 minutes vs 6.9 +/- 2.8 minutes (difference not significant [NS]), 125 +/- 17 beats/min vs 125 +/- 19 beats/min (NS) and 2.3 +/- 0.8 mm vs 2.1 +/- 0.8 (NS), respectively. Ambulatory monitoring revealed 205 episodes of significant ST-segment depression (J + 80 ms; 49 episodes with more than 1 mm, 83 with more than 2 mm, 39 with more than 3 mm and 34 with more than 4 mm). Of all episodes of ST-segment depression, 130 (64%) were asymptomatic. The episodes lasted for 3 to 110 minutes. The maximal 24-hour ambulatory heart rate and ST-segment depression during ischemic episodes were expressed as a percentage of those seen during exercise-induced ischemia. When all ambulatory ischemic episodes (both symptomatic and asymptomatic) were compared with exercise-induced ischemic changes in the individual patient, there was little difference in heart rate (91 +/- 15% vs 90 +/- 18%, NS) but there was a greater magnitude of ST-segment depression (122 +/- 57% vs 104 +/- 52%, p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Holter monitoring in assessment of angina pectoris

Holter monitoring of ST-segment changes is a unique method of studying the character of transient myocardial ischemia that occurs during ordinary daily life. The electrocardiographic signal is a reliable marker of ischemia in defined populations of patients with angina and coronary disease, but should be interpreted with caution outside of these groups. Detailed studies in patients with chronic stable angina have shown that transient ischemia is frequently silent and prolonged, and may occur without evidence of physical exertion. Analysis of underlying changes in regional myocardial perfusion using rubidium-82 and positron tomography has shown that a decrease in myocardial perfusion (supply) is involved in the genesis of many episodes of ischemia during daily life. Clinical trials have shown that drugs that affect demand and supply are efficacious against both painful and painless ischemia and that combinations of agents can provide useful benefits. There is, however, marked natural variability in disease activity despite "stable" symptoms, which must be taken into account in individual patient assessment and the rational design of clinical trials. Ambulatory monitoring permits quantitation of previously unrecognized myocardial ischemia, and treatment can thus be assessed in terms of ischemic activity during everyday life rather than on data obtained during brief hospital visits. An active approach to the detection and monitoring of transient ischemia with and without pain will be necessary if prospective clinical research shows that treatment of silent myocardial ischemia can prevent myocardial damage and improve prognosis.

The haemodynamic significance of asymptomatic ST segment depression assessed by ambulatory pulmonary artery pressure monitoring

A transducer-tipped catheter with simultaneous frequency modulated electrocardiograms and a miniaturised tape recorder was used to record ambulatory pulmonary artery pressure for 24-48 hours in 19 men (mean age 57.7) with clinical and angiographic evidence of coronary artery disease. Sixty seven episodes of ST segment depression (greater than 1 mm) were recorded. Thirty five were accompanied by pain of which six occurred at night; in 34 pulmonary artery diastolic pressure rose significantly. In all but two of the 32 episodes of painless ST segment depression (four of which were at night) there was a significant rise in pulmonary artery diastolic pressure. No such rise was found in six normal subjects during exertion. ST segment changes tended to occur before (24 episodes) or at the same time (27 episodes) as changes in pulmonary artery diastolic pressure. ST segment depression followed an increase in pulmonary artery diastolic pressure in only 13 episodes. The times to maximum ST depression and maximum pulmonary artery diastolic pressure rise were similar. Painful and painless ST segment depression could not be distinguished on the basis of the configuration of the ST segment or in terms of the changes in the pulmonary artery diastolic pressure.

Ambulatory monitoring of the ST segment in diabetic men with and without peripheral neuropathy

To assess whether myocardial ischaemia is more common in diabetic patients with neuropathy, 24-hour ambulatory monitoring of the ST segment was performed on 27 diabetic men without peripheral neuropathy and in 28 with neuropathy. The patients were matched for age 54 +/- 7 years (mean +/- SD) versus 54 +/- 7 years and for duration of diabetes (16 +/- 9 years versus 16 +/- 12 years). None had clinical evidence of heart disease. Episodes of ST segment depression were seen during ambulatory monitoring in 12 diabetics (22%) but were not more common in patients with peripheral neuropathy. Four of the 13 diabetics with autonomic neuropathy had ST depression during ambulatory monitoring. During a median follow-up period of 50 months, four patients developed clinical heart disease. Three of these patients had shown ST depression during ambulatory monitoring. ST depression during ambulatory monitoring is common in diabetic men without cardiac symptoms but is not related to the presence of peripheral neuropathy. Diabetics with ST depression during ambulatory monitoring are at increased risk of developing heart disease in subsequent years.

Silent myocardial ischemia: clinical characteristics, underlying mechanisms, and implications for treatment

A great deal of interest is being generated by the possibility that patients with coronary artery disease and typical angina pectoris may also experience periods of ischemia during activities of daily living that are not necessarily associated with angina or increased myocardial oxygen demand. It might be that the majority of ischemic episodes during daily life are not preceded by increases in myocardial oxygen demand, and are probably related to dynamic changes in coronary blood flow. Questions still remain, however, regarding the prevalence of asymptomatic ischemia in patients who present with effort angina and positive results on exercise tolerance tests. Therefore, in susceptible patients with coronary artery disease, calcium channel blockers, especially nifedipine, may be of particular benefit since they decrease myocardial oxygen demand during effort and may increase coronary blood flow, thereby aborting asymptomatic ischemia, which tends to occur at low levels of cardiac oxygen demand. It appears that a greater awareness of the total ischemic burden, i.e., the sum total of symptomatic and asymptomatic and exertional and nonexertional ischemia, may facilitate individualization of therapy for patients with coronary artery disease. Agents that both reduce myocardial oxygen demand and improve coronary blood flow, such as nifedipine, may particularly benefit individuals whose ischemia may be both asymptomatic and symptomatic, and who seem to constitute the majority of patients with coronary artery disease.

Character of transient ischemia in angina pectoris

There is growing interest in the possible therapeutic and prognostic significance of silent myocardial ischemia in coronary artery disease (CAD) and its detection by ambulatory electrocardiographic (ECG) monitoring. In 100 apparently healthy normal subjects (20 with angiographically normal coronary arteries), Holter monitoring revealed significant ST-segment depression in only 2 (both over 40 years, one with positive treadmill test, the other with risk factor for CAD). No significant ECG changes were found in those with normal coronary vessels. In 30 patients with documented CAD, significant ST-segment depression during 1,934 episodes over 446 days of monitoring over 18 months was found. Only 24% of the episodes were associated with angina. Asymptomatic and symptomatic episodes were associated with comparable changes in perfusion detected by positron emission tomography. Heart rate increases greater than 10 beats/min preceding the onset of the ST-segment changes occurred in only 23% of the episodes. There was considerable variability in the ST-segment changes in the same patient monitored serially over long periods of time. The data indicate that it is extremely uncommon for patients without CAD to exhibit silent myocardial ischemia, whereas patients with stable angina exhibit frequent, variable and often asymptomatic ECG evidence of myocardial ischemia rarely triggered by increases in heart rate. These findings are likely to be of therapeutic and prognostic significance.

Features of the exercise test that reflect the activity of ischemic heart disease out of hospital

To better understand the relationship between the transient myocardial ischemia seen during an exercise test and ischemic activity out of hospital, 39 patients with well-documented coronary artery disease underwent standard treadmill exercise testing (Bruce protocol) and 24 to 48 hr of continuous ambulatory electrocardiographic monitoring during normal daily activities. A total of 245 episodes of transient ischemia were recorded in 21 of 32 patients with positive exercise electrocardiograms (group I), whereas seven patients with negative test results (group II) had no episodes of transient ischemia, during monitoring out of hospital (p less than .01). Certain measures in the exercise test were related to the severity of ischemia out of hospital: there were more episodes and a greater total duration of transient ischemia per 24 hr of ambulatory monitoring in patients who developed ischemic electrocardiographic changes before 6 min of exercise (p less than or equal to .021) or at a heart rate of less than 150 beats/min (p = .005) and in those in whom these ST segment changes persisted for more than 5 min after exercise (p less than or equal to .016). In contrast, there was no relationship between transient ischemia out of hospital and the commonly quoted exercise variables: chest pain, total exercise duration, and the maximum levels of heart rate, systolic blood pressure, and double product. Thus, patients with coronary artery disease and negative exercise electrocardiograms are most unlikely to experience active ischemia during normal daily life.(ABSTRACT TRUNCATED AT 250 WORDS)