Prognostic significance of transient myocardial ischaemia after first acute myocardial infarction: five year follow up study.

OBJECTIVE--To assess the five year prognostic significance of transient myocardial ischaemia on ambulatory monitoring after a first acute myocardial infarction, and to compare the diagnostic and long term prognostic value of ambulatory ST segment monitoring, maximal exercise testing, and echocardiography in patients with documented ischaemic heart disease. DESIGN--Prospective study. SETTING--Cardiology department of a teaching hospital. PATIENTS--123 consecutive men aged under 70 who were able to perform predischarge maximal exercise testing. INTERVENTIONS--Echocardiography two days before discharge (left ventricular ejection fraction), maximal bicycle ergometric testing one day before discharge (ST segment depression, angina, blood pressure, heart rate), and ambulatory ST segment monitoring (transient myocardial ischaemia) started at hospital discharge a mean of 11 (SD 5) days after infarction. MAIN OUTCOME MEASURES--Relation of ambulatory ST segment depression, exercise test variables, and left ventricular ejection fraction to subsequent objective (cardiac death or myocardial infarction) or subjective (need for coronary revascularisation) events. RESULTS--23 of the 123 patients had episodes of transient ST segment depression, of which 98% were silent. Over a mean of 5 (range 4 to 6) years of follow up, patients with ambulatory ischaemia were no more likely to have objective end points than patients without ischaemic episodes. If, however, subjective events were included an association between transient ST segment depression and an adverse long term outcome was found (Kaplan-Meier analysis; P = 0.004). The presence of exercise induced angina identified a similar proportion of patients with a poor prognosis (Kaplan-Meier analysis; P < 0.004). Both exertional angina and ambulatory ST segment depression had high specificity but poor sensitivity. The presence of exercise induced ST segment depression was of no value in predicting combined cardiac events. Indeed, patients without exertional ST segment depression were at increased risk of future objective end points (Kaplan-Meier analysis; P < 0.0045). These findings may be explained in part by a higher prevalence of left ventricular dysfunction in patients without ischaemic changes in the exercise electrocardiogram (P < 0.05). CONCLUSION--There seem to be limited reasons to perform ambulatory ST segment monitoring in survivors of a first myocardial infarction who can perform exercise tests before discharge. Patients at high risk of future myocardial infarction or death from cardiac causes are not identified. Ambulatory monitoring and exertional angina distinguish a small subset of patients who will develop severe angina pectoris demanding coronary revascularisation during follow up. Patients without exercise induced ST segment depression comprise a high risk subgroup in terms of subsequent objective end points. The role of ambulatory ST segment monitoring performed in unselected patients immediately after infarction when risk is maximal remains to be clarified.     

Transient ischaemia after acute myocardial infarction: relationship to exercise ischaemia

To study the implications of transient myocardial ischaemia following acute myocardial infarction we compared ambulatory ST segment monitoring with exercise treadmill testing in 170 patients (mean age 58 years) at 4-8 weeks after admission. Ambulatory monitoring detected transient ischaemia (265 episodes; 249 (94%) silent) in 53/170 patients (31%) which was less frequent than ischaemia during exercise testing (90 patients; 53%) (P less than 0.0001). However, patients displaying transient ambulatory ischaemia (i) achieved less total exercise (248.7 +/- 17.2 vs 318.7 +/- 14.1 s; means +/- SEM) (P less than 0.006), (ii) developed exercise ST deviation earlier (172.4 +/- 14.3 vs 244.8 +/- 16.2 s) (P less than 0.0004) and (iii) had more widespread exercise ischaemia (3.8 +/- 0.3 vs 2.5 +/- 0.2 ECG leads) (P less than 0.005). Positive ambulatory ST segment monitoring was infrequently found (12/80 patients; 15%) in the presence of a negative exercise test but did identify the majority of patients (9/11 patients; 82%) with easily provoked exercise ischaemia and hence strongly positive exercise tests. These data suggest a limited role for routine 24 h ambulatory monitoring after myocardial infarction for the diagnosis of ongoing ischaemia but raise the possibility of an important place for this test in prognosis and risk stratification.     

Transient myocardial ischaemia after acute myocardial infarction

The prevalence and characteristics of transient myocardial ischaemia were studied in 203 patients with recent acute myocardial infarction by both early (6.4 days) and late (38 days) ambulatory monitoring of the ST segment. Transient ST segment depression was much commoner during late (32% patients) than early (14%) monitoring. Most transient ischaemia (greater than 85% episodes) was silent and 80% of patients had only silent episodes. During late monitoring painful ST depression was accompanied by greater ST depression and tended to occur at a higher heart rate. Late transient ischaemia showed a diurnal distribution, occurred at a higher initial heart rate, and was more often accompanied by a further increase in heart rate than early ischaemia. Thus in the first 2 months after myocardial infarction transient ischaemia became increasingly common and more closely associated with increased myocardial oxygen demand. Because transient ischaemic episodes during early and late ambulatory monitoring have dissimilar characteristics they may also have different pathophysiologies and prognostic implications.     

Transient myocardial ischaemia after acute myocardial infarction.

The prevalence and characteristics of transient myocardial ischaemia were studied in 203 patients with recent acute myocardial infarction by both early (6.4 days) and late (38 days) ambulatory monitoring of the ST segment. Transient ST segment depression was much commoner during late (32% patients) than early (14%) monitoring. Most transient ischaemia (greater than 85% episodes) was silent and 80% of patients had only silent episodes. During late monitoring painful ST depression was accompanied by greater ST depression and tended to occur at a higher heart rate. Late transient ischaemia showed a diurnal distribution, occurred at a higher initial heart rate, and was more often accompanied by a further increase in heart rate than early ischaemia. Thus in the first 2 months after myocardial infarction transient ischaemia became increasingly common and more closely associated with increased myocardial oxygen demand. Because transient ischaemic episodes during early and late ambulatory monitoring have dissimilar characteristics they may also have different pathophysiologies and prognostic implications.     

Determinants of left ventricular systolic function after acute myocardial infarction: the role of residual myocardial ischaemia

BACKGROUND: Left ventricular systolic function (LVSF) is one of the major determinants of survival after acute myocardial infarction (AMI). Some factors such as the infarct size and localization, and the patency of the infarct-related artery are known determinants of LVSF. However, the long-term effect of myocardial ischaemia on LVSF has been poorly studied in clinical settings. OBJECTIVES: To assess the acute and long-term effects of myocardial ischaemia on LVSF in patients recovering from an AMI. METHODS: A cohort of 74 patients recovering from AMI was studied. Myocardial ischaemia was detected by means of ambulatory electrocardiogram (ECG) monitoring at recruitment (4+/-2 days after AMI), exercise ECG test and stress echocardiography at discharge (7+/-4 days after AMI). LVSF was studied by means of two-dimensional echocardiography at recruitment, at discharge, and at 1, 3, 6 and 12 months after AMI. RESULTS: Patients with myocardial ischaemia on ambulatory ECG monitoring and stress echocardiography had worse LVSF at recruitment than those without ischaemia. The presence of myocardial ischaemia on ambulatory ECG monitoring was an independent determinant of LVSF at recruitment together with infarct localization and size (assessed by creatine kinase MB isoenzyme (CK-MB) levels). Patients with signs of myocardial ischaemia on ambulatory ECG monitoring and stress echocardiography had a progressive left ventricular dysfunction compared with those without ischaemia. CONCLUSIONS: Residual ischaemia is an independent determinant of LVSF after AMI and its presence implied a progressive worsening of the LVSF. Because left ventricular systolic dysfunction is a major determinant of survival after AMI, its precursors, among them residual myocardial ischaemia, should be identified. Treatment of ischaemia is known to be associated with improved prognosis and improved LVSF.     

Silent ischemia after myocardial infarct

The Framingham study demonstrated that 25% of all episodes of acute myocardial infarction (AMI) do not present clinical symptoms, and are later recognized in a routine ECG. Silent ischaemia is frequently found after acute myocardial infarction, and has been identified in 25-60% of the patients according to the results of different studies and the different criteria employed for diagnosis. Silent ischaemia after AMI, as well as angina, is related with the presence and extent of severe coronary lesions located in the infarct related coronary artery or in other vessel not responsible for the acute episode of necrosis. The prognostic significance of silent ischaemia after AMI has not been well established. In some studies the painless ST segment depression during an exercise test soon after AMI presented the same prognostic value that the ST segment depression accompanied by angina, but in others the symptomatic episodes were a better predictor of major events and long term survival after the infarct. Several studies employing ambulatory ECG monitoring (Holter) also seem to indicate that the painless and transient episodes of ST segment depression identify a group of patients with worse prognosis, but in these studies the patients were selected, introducing a clear bias in the results of these investigations. Finally, asymptomatic transient perfusion defects in thallium studies clearly identify a group of high risk patients with a higher incidence of complications and higher mortality rate than the patients with negative thallium studies. The efficacy of anti-ischaemic drugs or myocardium revascularization procedures, including surgery, has not been studied in patients with silent ischaemia after acute myocardial infarction.(ABSTRACT TRUNCATED AT 250 WORDS)     

Different mechanisms for the relief of angina after coronary bypass surgery. Physiological versus anatomical assessment.

To determine the physiological effect of coronary artery bypass surgery and the mechanisms for pain relief, 15 patients with exertional angina were studied before and after operation. Before the operation conventional tests included exercise tests (all positive) and coronary angiography (all patients had greater than or equal to 70% stenosis of major vessels). In addition, ambulatory electrocardiographic monitoring during 48 hours detected 92 episodes (greater than or equal to 1 mm) of ST depression. Regional myocardial perfusion was assessed with positron tomography using rubidium-82 (t1/2 78 s) and this showed reversible inhomogeneity with absolute regional reduction of cation uptake after exercise in all 15 patients. After coronary surgery 10 of the 15 patients had (a) no angina, (b) patent grafts (three or more), (c) no evidence of ischaemia during ambulatory monitoring out of hospital, and (d) homogeneous perfusion with reversal of the disturbances in regional myocardial perfusion after exercise. After operation one of the 15 patients had no angina and showed silent infarction in the segment that was previously ischaemic but supplied by a patent graft. All but one of the remaining patients had no angina, patent grafts, but disturbances of regional myocardial perfusion with silent ischaemia on exercise. Two of these patients continued to have asymptomatic and ischaemic episodes of ST depression during ambulatory monitoring out of hospital. This physiological study of regional myocardial perfusion in patients in hospital and in those with ischaemia out of hospital showed that three different mechanisms may account for the relief of pain--improved perfusion, infarction, and silent ischaemia. Silent ischaemia in particular raises puzzling pathophysiological and therapeutic questions that may affect prognosis and the interpretation of clinical trials.     

Transient myocardial ischaemia: a multivariate analysis on clinical, angiographic and ergometric variables

The availability of ambulatory ECG monitoring allows identification of transient myocardial ischaemia, the clinical relevance of which is currently being investigated. Ninety-four consecutive patients with ischaemic heart disease and a positive exercise test (greater than or equal to 1 mm ST-segment depression) were studied to evaluate the prevalence of transient myocardial ischaemia (either painless or painful) during 24-h dynamic electrocardiogram (ECG) and the clinical, angiographic and ergometric variables predicting its appearance. Two-hundred-and-eighty-one episodes of transient electocardiographic myocardial ischaemia were recorded in 69 patients (73.4% of all patients). Transient myocardial ischaemia was more frequent, although not significantly so, in patients with diabetes, with previous myocardial infarction, or with multivessel disease. When tested by multivariate analysis, neither the clinical variables nor the severity of coronary artery disease allowed prediction of the occurrence of transient myocardial ischaemia during dynamic ECG. The duration of exercise testing up to the ischaemic threshold (ST-segment depression = 1 mm) and the peak heart rate during exercise were more accurate predictors of transient myocardial ischaemia (P = 0.019 and 0.012 respectively). Patients with transient myocardial ischaemia had a lower ischaemic threshold (355 +/- 175 vs 498 +/- 150 s, mean +/- SD, P = 0.001) despite a lower peak heart rate (129 +/- 18 vs 137 +/- 12 beats min-1, P = 0.047) than patients without transient myocardial ischaemia. In conclusion, exercise testing may help select patients for examination by dynamic ECG.(ABSTRACT TRUNCATED AT 250 WORDS)     

Thrombolysis significantly reduces transient myocardial ischaemia following first acute myocardial infarction.

In order to investigate whether thrombolysis affects residual myocardial ischaemia, we prospectively performed a predischarge maximal exercise test and early out-of-hospital ambulatory ST segment monitoring in 123 consecutive men surviving a first acute myocardial infarction (AMI). Seventy-four patients fulfilled our criteria for thrombolysis, but only the last 35 patients included received thrombolytic therapy. As thrombolysis was not available in our Department at the start of the study, the first 39 patients included were conservatively treated (controls). No significant differences in baseline clinical characteristics were found between the two groups. In-hospital atrial fibrillation and digoxin therapy was more prevalent in controls (P less than 0.05). During exercise, thrombolysed patients reached a higher maximal work capacity compared with controls: 160 +/- 41 vs 139 +/- 34 W (P less than 0.02). Thrombolysis resulted in a non-significant reduction in exercise-induced ST segment depression: prevalence 43% vs 62% in controls. However, during ambulatory monitoring the duration of transient myocardial ischaemia was significantly reduced in thrombolysed patients: 322 min vs 1144 min in controls (P less than 0.05). Thrombolysed patients reached a higher heart rate during transient ischaemic episodes: 114 +/- 17 vs 93 +/- 11 b.min-1 in controls (P less than 0.001). In conclusion, thrombolytic therapy administered for a first AMI significantly reduces the burden of transient myocardial ischaemia. This may explain the improvement in myocardial function during physical activities, which was also observed in this study.     

Transient myocardial ischaemia after acute myocardial infarction does not induce ventricular arrhythmias.

OBJECTIVE--To see whether transient myocardial ischaemia on ambulatory monitoring after myocardial infarction is associated with ventricular arrhythmias. DESIGN--A prospective study. SETTING--The coronary care unit, general medical wards, and cardiorespiratory department of a major teaching hospital. PATIENTS--203 consecutive patients without specific exclusion criteria admitted with acute myocardial infarction. INTERVENTIONS--24 hour ambulatory electrocardiographic monitoring for ventricular arrhythmias and ST depression both early (mean 6.3 days after infarction, n = 201) and late (mean 38 days, n = 177). MAIN OUTCOME MEASURES--Episodes of myocardial ischaemia were identified during ambulatory monitoring by transient ST depression of > or = 1.0 mm lasting for > or = 30 s. Ventricular arrhythmias were single extrasystoles, couplets, or ventricular tachycardia. RESULTS--All ventricular arrhythmias were significantly more frequent in late than early monitoring. The arrhythmias included couplets (in 83/174 (48%) v 49/200 (25%) of patients, p = 0.0000028) and ventricular tachycardia (29/174 (17%) v 15/199 (8%), p = 0.0064). Patients with ST depression (29 early; 56 late), compared with those without ischaemia, did not experience a significant increase in single extrasystoles, couplets (31% v 23% early; 47% v 48% late), or ventricular tachycardia (3% v 8% early; 18% v 16% late). Even patients with frequent (> or = 3 episodes), and deep (> or = 1.5 mm) or prolonged (> or = 20 min) ST depression had no increase in arrhythmias. CONCLUSIONS--Ventricular arrhythmias after myocardial infarction are not associated with transient myocardial ischaemia during daily activities. This study does not support the belief that to abolish silent ischaemia would reduce the incidence of sudden death due to uncontrollable ventricular arrhythmias after myocardial infarction.     

Stress testing predischarge and six weeks after myocardial infarction to compare submaximal and maximal exercise predischarge and to assess the reproducibility of induced abnormalities

Submaximal and maximal treadmill exercise tests were performed predischarge in 64 patients after acute myocardial infarction to assess the relative yield of residual ischaemic abnormalities. The reproducibility of individual abnormalities resulting from maximal stress tests performed predischarge and 6 weeks after infarction was also assessed in 55 of these patients. Compared with predischarge submaximal exercise testing, a maximal exercise test identified a significantly greater number of patients with residual myocardial ischaemia (26 vs. 15, P less than 0.05) and this was associated with a significantly longer average maximal exercise duration (P less than 0.001), and a higher rate-pressure product (P less than 0.001). Among the 55 patients who had maximal stress tests both predischarge and 6 weeks after infarction, there was a significant lack of reproducibility in the occurrence of exercise induced angina (P less than 0.01) and an abnormal blood pressure response (P less than 0.02). In contrast, exercise induced ST segment depression and elevation and ventricular arrhythmias were relatively reproducible. More patients had an ischaemic test result (ST depression or angina) at the later test compared to the predischarge test (33 vs. 25 patients) but this increase was not statistically significant. There were, however, significant increases at the later test in mean maximal exercise duration (P less than 0.001). mean maximal heart rate (P less than 0.001) and heart rate-systolic blood pressure double product (P less than 0.001). The majority of patients who had a cardiac event in the period between the two tests had a predischarge test abnormality. We conclude that a significantly greater number of patients with residual reversible myocardial ischaemia after infarction will be identified by symptom limited exercise testing compared with a submaximal predischarge test. Because ST depression and elevation appear reproducible, patients who develop these abnormalities during a predischarge test do not, for prognostic reasons, need retesting 6 weeks after infarction. Exercise induced angina pectoris and an abnormal blood pressure response, however, are highly variable and in these patients a repeat test may be useful.     

Value of ambulatory ST segment monitoring in patients with chronic stable angina: does measurement of the "total ischaemic burden" assist with management?

OBJECTIVE--To assess the prognostic significance of transient ischaemic episodes during daily activities in patients with stable angina. PATIENTS AND METHODS--172 patients with stable angina attending the cardiac outpatients departments of Hillingdon Hospital (n = 155) and the National Heart Hospital (n = 17) were prospectively studied by exercise testing and 48 hours of ambulatory ST segment monitoring, and followed for prognostic purposes for up to 39 months (mean 24.5 months). Patient inclusion depended on a clinical diagnosis of stable coronary artery disease which necessitated outpatient review (and antianginal treatment in 94% of patients). It was not dependent on objective evidence of reversible ischaemia. Events recorded during the follow up period included death, non-fatal myocardial infarction, unstable angina, and the requirement for revascularisation. RESULTS--72 patients (42%) had transient ischaemic episodes during daily activities, and 104 patients (60.5%) had an ischaemic response to exercise. 63 patients (36%) had evidence of ischaemia on both investigations; with 59 (34%) having no documented ischaemia on either investigation. There were 27 patient events (15.7%) recorded over a mean 24.5 month follow up, including five deaths (2.9%) (three cardiac related (1.7%)), six non-fatal myocardial infarctions (3.5%), six admissions with unstable angina (3.5%), and 10 revascularisation procedures (5.8%). Of the nine "hard" or objective end points (cardiac death and non-fatal myocardial infarction), only two had evidence of transient ischaemia on ambulatory ST segment monitoring at initial investigation, with 10 of the 25 patients (38.5%) with any cardiac event having such episodes. CONCLUSIONS--The outcome in patients with chronic stable angina receiving standard medical treatment was good over a mean two year follow up period. For the purpose of assessing prognosis over this time scale, there was no advantage to performing ambulatory ST segment monitoring in such patients.     

Value of ambulatory ST segment monitoring in patients with chronic stable angina: does measurement of the "total ischaemic burden" assist with management?

OBJECTIVE--To assess the prognostic significance of transient ischaemic episodes during daily activities in patients with stable angina. PATIENTS AND METHODS--172 patients with stable angina attending the cardiac outpatients departments of Hillingdon Hospital (n = 155) and the National Heart Hospital (n = 17) were prospectively studied by exercise testing and 48 hours of ambulatory ST segment monitoring, and followed for prognostic purposes for up to 39 months (mean 24.5 months). Patient inclusion depended on a clinical diagnosis of stable coronary artery disease which necessitated outpatient review (and antianginal treatment in 94% of patients). It was not dependent on objective evidence of reversible ischaemia. Events recorded during the follow up period included death, non-fatal myocardial infarction, unstable angina, and the requirement for revascularisation. RESULTS--72 patients (42%) had transient ischaemic episodes during daily activities, and 104 patients (60.5%) had an ischaemic response to exercise. 63 patients (36%) had evidence of ischaemia on both investigations; with 59 (34%) having no documented ischaemia on either investigation. There were 27 patient events (15.7%) recorded over a mean 24.5 month follow up, including five deaths (2.9%) (three cardiac related (1.7%)), six non-fatal myocardial infarctions (3.5%), six admissions with unstable angina (3.5%), and 10 revascularisation procedures (5.8%). Of the nine "hard" or objective end points (cardiac death and non-fatal myocardial infarction), only two had evidence of transient ischaemia on ambulatory ST segment monitoring at initial investigation, with 10 of the 25 patients (38.5%) with any cardiac event having such episodes. CONCLUSIONS--The outcome in patients with chronic stable angina receiving standard medical treatment was good over a mean two year follow up period. For the purpose of assessing prognosis over this time scale, there was no advantage to performing ambulatory ST segment monitoring in such patients.     

Effects of asymptomatic ischemia on long-term prognosis in chronic stable coronary disease

BACKGROUND. Ischemia on ambulatory electrocardiographic monitoring has been shown to adversely affect short-term prognoses in patients with unstable angina, after myocardial infarction, and with chronic stable angina. METHODS AND RESULTS. In this long-term study, we followed 138 patients (mean age, 59 +/- 9 years) with chronic stable angina and positive exercise tests for cardiac events (e.g. death, myocardial infarction, percutaneous transluminal coronary angioplasty, or coronary artery bypass graft surgery). In 105 patients, ambulatory electrocardiographic monitoring was performed after all antianginal medication was withheld for 48 hours. In 26 patients, the diagnostic tests were repeated while on their usual medication. In addition to the 105 patients, 33 patients had their monitoring performed only while on their usual medication. During 37 +/- 17 months of follow-up, there were nine deaths, nine myocardial infarctions, and 35 revascularization procedures. In patients monitored off medication, Cox survival analysis showed that the occurrence of ischemia on electrocardiographic monitoring was the most significant predictor of death and myocardial infarction in the subsequent 2 years (p = 0.02) and all adverse events for 5 years (p = 0.009). Patients who were monitored on medication and did not have ischemia (n = 18) appeared to have more adverse events than patients who had no ischemia while being monitored off medication (n = 43). CONCLUSIONS. Asymptomatic ischemia on ambulatory electrocardiographic monitoring in patients with stable angina predicts death and myocardial infarction for 2 years and all adverse events for 5 years. Monitoring performed while on medication may show no ischemia; however, this may not indicate low risk of future coronary events.     

The Sensitivity of the Symptom Angina Pectoris as a Marker of Transient Myocardial Ischaemia in Chronic Stable Angina Pectoris

ABSTRACT Therapeutic decisions in patients with angina pectoris are traditionally based on the history reported by the patient, since objective evidence of myocardial ischaemia during daily life is often not available. In this study, ambulatory ST segment monitoring was performed in 60 patients with a history of chronic stable angina pectoris, positive exercise test and/or positive coronary angiography, and a correlation was made between the episodes of chest pain and ST segment change. The patients were grouped according to the results of exercise testing and coronary arteriography, and one group was studied with and without antianginal medication. Overall, 195 episodes of angina were noted, only 94 of which (48%) were accompanied by ST segment depression. Pain and ST segment changes were best correlated in patients with a positive exercise test, positive angiography and who were not receiving antianginal medication. In 101 episodes of chest pain, ST segment change could not be identified; in 18 (18%) there was sinus tachycardia, in 12 (12%) ventricular premature beats, and in 71 (70%) sinus rhythm solely. Thus, anginal pain appears not to be the reliable indicator of transient myocardial ischaemia as was previously thought, a finding which supports the use of objective methods in identifying episodes of transient myocardial ischaemia in daily life.     

Late recurrent ischemia in infarct patients with a normal predischarge exercise test after thrombolysis

We investigated the prognostic value of normal predischarge exercise test in 109 patients after myocardial infarction treated with i.v. thrombolysis within 4 h. In 29 of these 109 patients, elective PTCA or bypass surgery was performed for prognostic reasons after coronary angiography; 80 patients were treated conservatively with drug therapy. Recurrent postinfarct angina early after hospital discharge was the reason in 4 of 80 for PTCA or bypass surgery. Twenty-three of the remaining 76 conservatively treated patients developed recurrent ischaemia during long-term follow-up of 12.0 +/- 6.2 months, including one patient with reinfarction. Late recurrent ischaemia during long-term follow-up was observed in one third of the conservatively treated patients with a normal predischarge exercise test, although a high percentage (30%) of patients in this subgroup had been treated with PTCA or bypass surgery mainly for prognostic reasons. Predischarge exercise test is therefore of limited value for detection of still viable myocardium at risk of further ischaemic events after acute myocardial infarction and thrombolysis.     

Transient Myocardial Ischaemia during Ambulatory Monitoring Out of Hospital in Patients with Chronic Stable Angina Pectoris

Abstract. Transient myocardial ischaemia during daily life, detected by ambulatory electrocardiographic monitoring, was investigated in 42 patients with chronic stable angina and documented coronary artery disease. Ambulatory monitoring was initiated for 36 hours after all prophylactic antianginal medication had been withdrawn for 5 days. There were 196 episodes of ST-segment depression, 145 (74%) of which were not accompanied by angina. As well, a tendency to more prolonged and greater ST-segment change with symptomatic ischaemic episodes was noted. A diurnal variation in transient ischaemia both with and without symptoms was observed, the highest frequency being in the morning hours. Transient myocardial ischaemia was more frequent in patients with double or triple vessel disease, compared with single vessel disease, but with a great variation. Heart rate at the onset of ischaemia during ambulatory monitoring was significantly lower than heart rate at the onset of ST-segment change during exercise testing (100.2±14.6 vs. 115.8±19.6 beats/min, p<0.01), which may indicate different pathophysiological mechanisms. Transient impairment in coronary oxygen supply seems to be of importance during ischaemic episodes out of hospital.     

The clinical significance of ventricular arrhythmias after myocardial infarction

Based on a sound foundation of data in thousands of patients who underwent ambulatory ECG recording after myocardial infarction, it is clear tht ventricular arrhythmias are harbingers of sudden cardiac death. Ambulatory electrocardiography, usually performed for 24 hours, continues to be the standard by which clinicians can identify patients at risk for sudden cardiac death after acute myocardial infarction. Ideally, this test should be performed in the late hospitalization phase of acute myocardial infarction, usually 1 to 2 days prior to discharge from the hospital, and the results made known to the clinician prior to the patient's departure from the hospital. Although performed less frequently, low-level exercise testing prior to discharge from the hospital has been shown in some studies to be of prognostic value in defining a group at high risk for sudden cardiac death. This test offers the additional benefit of allowing the clinician to more knowledgeably prescribe an exercise regimen after hospitalization. The specific role of electrophysiologic testing is presently under clinical investigation. At present, only patients with documented spontaneous sustained ventricular tachycardia or sudden cardiac death after myocardial infarction should be candidates for this study. Although it may be possible in the future that electrophysiologic testing will also be used in patients with high-risk arrhythmia detected on ambulatory electrocardiography, at present this is the subject of clinical investigation in academic medical centers and is not recommended as part of standard therapy.     

Prognostic value of exercise testing in a cohort of patients followed for 15 years after acute myocardial infarction.

AIMS: To study the long-term prognostic information obtained from an exercise test following an acute myocardial infarction. METHODS: Between 1979 and 1983, 1773 consecutive patients were admitted to Glostrup County Hospital with an acute myocardial infarction. Of 1430 patients who were alive after 3 weeks, 718 performed an exercise test. Survival data were available after 15 years for all patients. RESULTS: Participation in an exercise test was associated with a risk reduction of death of 56% (95% confidence interval, 49--65%) when adjusting for known differences between the groups. Among patients who performed the test, most indicators of ischaemia were without prognostic information. Exercise tolerance, expressed in metabolic equivalents, was the best predictor of future mortality (relative risk 0.86 for an increase of one metabolic equivalent (0.80--0.92)). Only ST-segment depression of 2 mm or more could identify a population with an increased risk of death (relative risk 1.45 (1.08--1.95)). CONCLUSION: Patients who perform an exercise test after acute myocardial infarction are a low risk population compared to those who do not perform it. The detection of ischaemia during the test is of marginal prognostic value. Exercise capacity is the most powerful predictor of death that can be obtained from the test.     

Silent ischaemia in diabetic men with autonomic neuropathy.

Autonomic neuropathy is associated with an increased incidence of silent myocardial infarction and sudden death. The purpose of this study was to investigate the prevalence of silent myocardial ischaemia in diabetic patients with autonomic neuropathy and without. Five standard autonomic function tests were performed on 41 men with diabetes: postural change in blood pressure, postural change in heart rate, heart rate response to deep breathing, heart rate response to Valsalva's manoeuvre, and blood pressure response to sustained handgrip. There were 17 patients with autonomic neuropathy (group A) and 24 with normal autonomic function (group B). All patients underwent 24 hour ambulatory electrocardiographic monitoring to detect silent ischaemia. There was no significant difference in risk factors for coronary artery disease or history of angina pectoris between these groups. The prevalence of silent ischaemia was 64.7% in group A (95% confidence interval (95% CI) 38.33 to 85.79%) and 4.1% in group B (95% CI 0.11 to 21.12%). This represents a relative risk of 42.2 (95% CI 4.5 to 39.4, p less than 0.001). These results are consistent with the concept that autonomic neuropathy may prevent the development of anginal pain and thus obscure the presence of ischaemic heart disease. Twenty four hour ambulatory electrocardiographic monitoring may identify a subgroup of diabetic patients with autonomic neuropathy who have myocardial ischaemia and to whom treatment may be offered.