Accurate rapid compact analog method for the quantification of frequency and duration of myocardial ischemia by semiautomated analysis of 24-hour Holter ECG recordings

Although the semiautomated analysis of 24-hour Holter recordings is now widely used in the detection and quantitation of disorders of cardiac rhythm and conduction, there are still no comparable methods for routine clinical use for the detection of the frequency and duration of myocardial ischemic episodes in patients with coronary artery disease (CAD). Research methods available to detect ischemic ST-T wave changes depend on sophisticated computer systems, are ill-suited for clinical use, and are not readily validated. However, when Holter tape is replayed at 60 times real time on heat-sensitive paper recorder at slow speeds (3.3 to 10 cm/min), rapid compact analog representation of 24-hour recording can be compressed into 480 to 1440 cm of paper. By this method, the close juxtaposition of QRST complexes produces distinctive patterns; from these the frequency and duration of myocardial ischemic episodes can be identified promptly, accurately, and reproducibly. When combined with conventional Holter scanning assembly, the accuracy of detection can be validated continuously by intermittent printout of the abnormality and ventricular ectopy can be quantitated simultaneously. The analysis of a technically acceptable 24-hour recording can be accomplished in 24 to 40 minutes (at 60 times real time playback) by an experienced operator. The fast compact analog representation of two-channel 24-hour recordings permitted the reliable detection of ST segment elevation and depression, pseudonormalization of ST-T wave abnormality, T wave augmentation, AV block, ventricular tachycardia, and intermittent bundle branch blocks. The technique also allowed the relationship of chest pain to the onset of ischemia to be established. Holter recordings from 22 CAD patients known to have myocardial ischemic episodes were examined; 275 episodes with ST segment deviations were identified, 92 (33.5%) being associated with angina which developed 2 to 18 minutes after the onset of ischemia. The method of compact analog ECG signal recording proved considerably superior to ST segment trend plotting; our data indicate that when combined with intermittent printout of observed abnormalities, the technique is simple, rapid, and extremely accurate in identifying the frequency and duration of myocardial ischemia from two-channel 24-hour Holter recordings. It permits the use of Holter monitoring for the noninvasive detection of myocardial ischemic episodes in a manner analogous to the quantitation and drug-induced suppression of ventricular ectopy from continuous ECG recording.     

Long-term frequency-modulated ECG recordings after PTCA in a patient with unstable angina pectoris. A case report

A patient presenting with unstable angina due to severe stenosis of the left anterior descending coronary artery encountered 6 episodes with ST segment depressions greater than or equal to 0.1 mV during frequency-modulated Holter monitoring. Four episodes were associated with anginal pain, 2 were asymptomatic. Percutaneous transluminal coronary angioplasty (PTCA) was performed. During balloon inflations horizontal ST segment depressions occurred. After successful PTCA, the patient remained asymptomatic and no significant ST segment changes were detected by Holter monitoring. Thus, by frequency-modulated Holter monitoring before, during, and after PTCA, the ischaemic cause of episodes with ST segment depressions greater than or equal to 0.1 mV could be demonstrated.     

Transient ST segment elevation occurring without anginal pain. Correlations with Prinzmetal's angina.

Two cases presenting with episodes of marked ST segment elevation occurring with, but most often without, anginal pain are reported. The changes were recorded through continuous ECG monitoring during Prinzmetal's angina and in the course of myocardial infarction. Such transient asymptomatic ECG abnormalities reveal silent acute myocardial ischemia and are often unrecognized. However, they may lead to severe arrhythmias or myocardial infarction, and sudden deaths occurring in the course of ischemic heart disease are likely to be explained on this basis. Transient episodes of silent ST segment elevation similar to those occurring in Prinztal's angina have been reported in various circumstances. They bring into discussion the delimitations of variant angina pectoris.     

Comparison of the data of 24-hour ECG monitoring and the condition of the coronary bed in patients with the variants of the course of unstable stenocardia]

A total of 232 patients with various clinical types of unstable angina pectoris were examined. All the patients underwent coronary angiographic studies, 24-hour ECG monitoring. In 40.5% of the patients, 24-hour monitoring revealed transient ST segment changes which were not accompanied by pain in 47% of the cases. ST segment changes were equally encountered in patients with one-, two-, and three-vessel disease in the presence or absence of pain. Ischemic ST segment changes generally occurred with an anginal episode in patients with crescendo unstable angina, whereas in those with more prolonged and intensified pain and angina at rest in particular, silent myocardial ischemic episodes were significantly more frequently recorded, which were more common in these patients with multivessel disease.     

Incidence of ventricular arrhythmias during transient myocardial ischemia in patients with stable coronary artery disease

To determine the incidence of ventricular arrhythmias related to episodes of transient myocardial ischemia during ambulatory electrocardiographic (ECG) monitoring, 97 patients with stable angina pectoris, angiographically proved coronary artery disease and an abnormal exercise test were studied. A total of 573 episodes with ST segment depression were documented: in 118 episodes (21%) the patients were symptomatic and in 455 (79%) they remained asymptomatic. Ventricular arrhythmias (greater than 5 premature ventricular beats/min, bigeminy, couplets or salvos of premature ventricular beats) occurred during 27 (5%) ischemic episodes in a subset of 10 patients (10%) (group A). The other 87 patients (90%) (group B) showed exclusively ischemic episodes without ventricular arrhythmias. Comparison of patients in group A and group B showed no differences in hemodynamic, angiographic, exercise testing and ambulatory ECG monitoring data. Ischemic episodes with and without ventricular arrhythmias showed a similar duration and amplitude of ST segment depression and a comparable heart rate at the onset of ischemia. Both types of ischemic episodes, with and without arrhythmias, occurred predominantly during the morning hours between 6:00 AM and noon, and both types remained asymptomatic to within similar percentages. The data demonstrate that ventricular arrhythmias are related to transient myocardial ischemia in only a few patients with stable angina pectoris; these arrhythmias are related neither to the degree of ischemia during ambulatory ECG monitoring nor to the occurrence of anginal symptoms.     

Prognostic value of total ischemic burden in patients with stable ischemic heart disease.

Patients with stable coronary artery disease commonly have transient myocardial ischemia with or without experiencing angina, but the prognostic implications of this "total ischemic burden" is still a matter of debate. We studied 112 consecutive patients with coronary artery disease, normal left ventricular function at rest and exercise-induced myocardial ischemia, a 24-hour ambulatory EKG was performed after drug withdrawal. The mean exercise duration was 572 +/- 192 seconds, with an ischemic threshold (ST depression = 1 mm) of 390 +/- 190 seconds). By Holter monitoring 30 patients had no ischemia and 82 (73%) had a total of 332 episodes of ST segment changes, the majority of which were asymptomatic (242/332, 73%). Among 82 patients with transient myocardial ischemia, 44 (54%) had only asymptomatic episodes. Nine patients (11%) complained of angina coincident to ST changes. Twenty-nine patients (35%) had both painful and painless ST segment alterations. All patients were prospectively followed-up while on conventional medical therapy. During a mean follow up of 25 +/- 10 months cardiac events occurred in 31 patients; there were 5 cardiac deaths, 3 non-fatal myocardial infarctions, 2 hospitalization for unstable angina and 21 revascularization procedures (PTCA or CABG). By multivariate analysis the number of stenotic vessels on coronary angiography was predictive of the events during the follow-up (p = 0.03), while other demographic, clinical, ergometric and angiographic variables were not influential. Event-free survival was similar for all subsets of transient myocardial ischemia (silent, symptomatic, or none).(ABSTRACT TRUNCATED AT 250 WORDS)     

Prognostic significance of "silent" myocardial ischemia in patients with unstable stenocardia

A 24-hour ECG monitoring was performed in 30 patients with unstable angina. Ten patients had episodes of transient ST-segment displacement only in the presence of anginal attacks (Group 1), 10 had ST-segment displacement episodes in the presence of both anginal attacks and silent myocardial ischemia (Group 2), and 10 with the displacements concurrent with only silent ischemia (Group 3). The patients from the groups were not significantly different in terms of major clinical, history, and angiographic data. Following an average of 1 year, death and acute myocardial infarction were observed in 1 (10%) and 2 (22.2%) in Group 1; 1 (10%) and 3 (33.3%) in Group 2; and 2 (20%) and 5 (62.5%) patients, respectively. It was concluded that episodes of silent myocardial ischemia are prognostically more hazardous than those of transient hypoxic ECG changes concomitant with anginal attacks.     

“Variant” angina: One aspect of a continuous spectrum of vasospastic myocardial ischemia: Pathogenetic Mechanisms, Estimated Incidence and Clinical and Coronary Arteriographic Findings in 138 Patients

From January 1970 to December 1977, transient reversible episodes of S-T segment elevation were documented in 138 patients (80 with angina only at rest, 58 with angina both on exertion and at rest). Electrocardiographic monitoring in 33 patients with hemodynamic monitoring revealed that (1) during 6,009 transient episodes of myocardial ischemia, pain was always a late phenomenon and, in some patients, often did not occur; (2) during such transient episodes, ST-T wave behavior was often variable in the same patient with alternation of elevation, depression or only T wave changes with or without pain; (3) independent of the direction of the S-T segment and T wave changes, the episodes were never preceded by an increase of the hemodynamic determinants of myocardial demand but were associated with obvious impairment of left ventricular function. Thallium scintigraphy in 32 patients revealed a regional massive and localized reduction of myocardial perfusion during S-T segment elevation and pseudonormalization of T waves. During S-T segment depression the reduction of thallium uptake was diffuse with fuzzy limits. Coronary angiography revealed no significant stenosis in 8 patients and single, double and triple vessel disease in 38, 34 and 26 patients, respectively. Angiography in all 37 patients studied during angina revealed a severe coronary vasospasm involving vessels with extremely variable extent of atherosclerosis. Severe arrhythmias were recorded in 27 patients, and a myocardial infarction occurred in 28. A total of five patients died within 1 month of hospital admission. Thus, variable intensity and extension of coronary vasospasm and the presence of collateral vessels may result in different degrees of ischemia and various electrocardiographic patterns with or without anginal pain. Vasospastic angina can occur in the presence of extremely variable degrees of coronary atherosclerosis and in any phase of ischemie heart disease. It may evolve into acute myocardial infarction and sudden death: Variant angina appears to be only its most striking electrocardiographic manifestation. When vasospastic angina is appropriately searched for, its incidence rate appears to be high.     

Prognosis for ischemic heart disease patients with episodes of painless myocardial ischemia alternating with rare attacks of stenocardia. The correlation between ischemia and ventricular extrasystole

Repeated annual 24-hour Holter's ECG monitoring sessions were used as a basis for 4-year follow-up of 108 male coronary patients with episodes of painless myocardial ischemia in the course of their everyday routines, and 144 control patients showing no signs of transient asymptomatic ischemia at 24-hour Holter's ECG monitoring. Four years of follow-up demonstrated no differences between the two groups, compared with respect to the incidence of myocardial infarction and associated mortality as well as aggravations of coronary heart disease, in terms of clinical pattern of the disease, the incidence of acute coronary episodes and survival rates. There were no sudden deaths in either of the groups. Transient painless myocardial ischemic episodes are shown to carry no additional risk of myocardial infarction and sudden death in elderly coronary patients with occasional anginal attacks.     

Asymptomatic transient ST changes during ambulatory ECG monitoring in diabetic patients

The reported higher incidence of painless myocardial infarction in diabetic patients suggests that asymptomatic transient myocardial ischemia may also be frequent in diabetes. To explore this possibility 51 subjects with type II diabetes, aged 43 to 71 years (mean +/- SEM 56 +/- 8), 70 nondiabetic patients with coronary artery disease (mean age 55 +/- 5), and 40 nondiabetic patients without overt coronary disease (age 54 +/- 9) were studied. Thirty-eight of the 51 diabetic patients (74%) had evidence of associated coronary disease and 19 (37%) had evidence of previous myocardial infarction. All subjects underwent continuous 24-hour ambulatory ECG monitoring. In 18 of 51 diabetic patients 93 episodes (73% of the total number) of asymptomatic ST segment changes were recorded; the total number of symptomatic episodes was 36, and they were observed in seven patients (27%). Forty-eight (60%) asymptomatic and 32 symptomatic episodes of significant ST changes were found in nondiabetic patients with coronary artery disease. When patients with previous myocardial infarction were examined separately, asymptomatic episodes of significant ST changes were observed in 10 of 19 diabetic patients and in 5 of 25 nondiabetic patients with coronary artery disease (p less than 0.05). In an additional 28 diabetic patients who underwent exercise stress test, 15 exhibited an abnormal ECG response; however, only five of them (33%) were symptomatic. This study suggests that the incidence of transitory myocardial ischemia, as assessed by ambulatory ECG monitoring and exercise stress test, is higher in type II diabetic patients than in nondiabetic control subjects with coronary artery disease.     

Electrocardiographic changes with coronary artery spasm

The presence or absence of important ECG changes (e.g., ST elevation or depression ≥ 1 mm) was evaluated in 79 consecutive patients with coronary artery spasm. In eight of these patients ECG changes usually did not accompany episodes of rest angina. Evaluation before, during, and after cardiac catheterization included multiple ECGs and ambulatory monitoring during angina. Our observations suggest that the ECG may not always be a sensitive indicator of coronary spasm. Thus the diagnosis of transient myocardial ischemia secondary to coronary spasm should not necessarily be excluded because of a lack of ECG changes during rest angina.     

Silent ischemia predicts infarction and death during 2 year follow-up of unstable angina

Silent myocardial ischemia as detected on Holter electrocardiographic (ECG) monitoring is present in greater than 50% of patients with unstable angina despite intensive medical therapy. The presence and the extent of silent ischemia have been correlated with an increased risk of early (1 month) unfavorable outcome including myocardial infarction and need for coronary revascularization for persistent symptoms. Seventy patients with unstable angina who had undergone continuous ECG monitoring for silent ischemia were followed up for 2 years; 37 patients (Group I) had Holter ECG evidence of silent ischemia at bed rest in the coronary care unit during medical treatment with nitrates, beta-receptor blockers and calcium channel antagonists; the other 33 patients (Group II) had no ischemic ST segment changes (symptomatic or silent) on Holter monitoring. Over a 2 year follow-up period, myocardial infarction occurred in 10 patients in Group I (in 2 it was fatal) compared with one nonfatal infarction in Group II (p less than 0.01 by Kaplan-Meier analysis); revascularization with either coronary bypass surgery or angioplasty for symptomatic ischemia was performed in 11 Group I and 5 Group II patients (p less than 0.05). Multivariate Cox's hazard analysis demonstrated that the presence of silent ischemia was the best predictor of 2 year outcome. Therefore, persistent silent myocardial ischemia despite medical therapy in patients with unstable angina carries adverse prognostic implications that persist over a 2 year period.     

Continuous electrocardiographic monitoring in patients with unstable angina pectoris: evaluation of medical treatment

Sixteen patients under treatment for unstable angina (UA) were subjected to 24-hour Holter monitoring after having been asymptomatic for at least 12 hours. 12-lead ECGs were obtained every 4 hours and when anginal pain supervened. Six patients (37.50%) had no evidence of ischemia in the Holter recordings and in the 12.lead ECGs and reported no anginal pain; five (31.25%) reported no pain but had evidence of ischemia in the Holter recordings and five (31.25%) reported anginal pain and had evidence of ischemia both in the Holter recordings and in the 12-lead ECGs. The probability for a 12-lead ECG to record an episode of silent myocardial ischemia (SMI) was only 1.54 x 10(-5). Medical treatment using conventional criteria was successful in 11 patients (68.75%). If the results of Holter monitoring are considered, the success rate was 37.50% (6 out of 16 patients free from ischemia). We conclude that as Holter monitoring reveals the episodes of SMI, it is a better means for assessing the results of medical treatment.     

Transient ischemia in angina pectoris: frequent silent events with everyday activities

To help characterize episodes of transient myocardial ischemia, 80 patients with chronic stable angina and evidence of obstructive coronary disease were studied by ambulatory electrocardiographic (ECG) monitoring outside the hospital to detect both symptomatic and asymptomatic episodes of ST-segment depression. In addition, patients were tested on an outpatient basis by means of positron emission tomography to assess regional coronary blood flow under different conditions. All patients showed ECG evidence of transient ischemia, with or without symptoms, while active outside the hospital. In-hospital testing showed that symptomatic and asymptomatic disturbances in regional coronary blood flow occurred with normal everyday activities and were not caused by physical exertion involving marked increases in heart rate and blood pressure. Most of these provocations were followed by a decrease in coronary blood flow in a poststenotic segment of myocardium and, like the ischemic events monitored out of hospital, the majority were silent. Many of these features characterizing the activity of ischemic heart disease may not be apparent from a patient's anginal history or results of hospital diagnostic testing.     

Clinical evaluation of transient myocardial ischemia

Out of 432 patients with coronary heart disease, 106 (24.5%) were found to have transient myocardial infarction during ECG monitoring of ST segment for 10 hours of daily activity. High-grade ventricular arrhythmias were revealed in 74.6% of mainly male and middle-aged subjects. 63.4% of the patients exhibited congestive heart failure, 48.1% had postinfarct cardiosclerosis, and 25.5% presented with diabetes mellitus. Transient myocardial ischemia was more frequently detected during exercise and more rarely during emotional stress (21.7%), meal (19.8%), and smoking (7.8%). Asymptomatic episodes of ST segment elevation were recorded in 36.8%, while asymptomatic episodes of ST segment depression, in 29.2%. The duration of asymptomatic episodes of ST segment elevation and depression was twice and 1.5 times, respectively, less than that of symptomatic ones. Substantial myocardial perfusion and metabolic impairments were revealed with an asymptomatic ST segment depression frequency of at least one an hour, an amplitude of more than 2 mm, and a duration of no less than 40 min.     

Transient myocardial ischemia during daily life in patients with syndrome X

Nineteen patients with syndrome X (typical exertional angina, positive exercise test response [at least 0.1 mV of ST-segment depression], no evidence of coronary spasm and angiographically normal coronary arteries) underwent continuous 48-hour electrocardiographic (ECG) monitoring during unrestricted daily life. Fifty-eight ischemic episodes of at least 0.1 mV of ST-segment depression were observed in the same ECG leads that showed ST depression during stress testing: 28 (48%) were accompanied by anginal pain and 30 (52%) were asymptomatic. No significant differences were found between painful and silent ST-segment depression with regard to the number of episodes, their temporal distribution, magnitude, duration or heart rate (HR) at onset of ST-segment depression. In the minute preceding ischemic ST shifts, HR did not change in 33% of episodes or increased by less than 10 beats/min in 28%. HR at onset of ST depression was significantly lower during ambulatory ECG monitoring than during exercise testing (98 ± 18 vs 117 ± 18 beats/min, p < 0.01). During ambulatory monitoring, 85 episodes of sinus tachycardia (exceeding by 10 to 80 beats/min the HR that triggered ischemia during exercise testing) occurred in the absence of angina or ST-segment shifts. The results of this study suggest that in patients with syndrome X, (1) myocardial ischemia frequently develops during daily life; (2) silent ischemia is an important component of this syndrome; and (3) increased oxygen demand in the presence of impaired coronary vasodilatory capacity is not the only cause of myocardial ischemia. Active mechanisms that transiently reduce coronary flow may act and explain occurrence of angina at rest and with minimal exertion.     

Holter ECG study of the electrocardiographic phenomena in Prinzmetal angina attacks with emphasis on the study of ventricular arrhythmias

The ECG phenomena in 20 outpatients (121 episodes) suffering from variant angina with transient ST segment elevation greater than 1.5 mm. (Prinzmetal angina) were studied by Holter monitoring. The most important changes in the ECG morphology were: a) increased height of the R wave in all cases, b) the S wave decreased or disappeared, c) the ST segment elevation varied from 1.5 to 38 mm, d) the TQ interval was ascending in 78 episodes, e) there was a double alternance of ST-TQ in 20 episodes and f) the first modification of the ECG was an increase of the T wave height. Arrhythmias were seen in 19 patients (44 episodes). The most frequent were premature ventricular contractions. The prevalence and importance of the ventricular arrhythmias were statistically related to the duration of the episodes (p less than 0.005), the degree of the ST segment elevation (p less than 0.005), the presence of ST-TQ alternance (p less than 0.005) and the presence of increased R wave greater than 25% (p less than 0.025).     

Polymorphic ventricular tachycardia with a short coupling interval in a patient with normal heart--a case report

We describe a case of a 59-year-old female with paroxysmal atrial fibrillation and arterial hypertension who had syncopal attacks due to polymorphic ventricular tachycardia (PMVT) with a short coupling interval of an initiating beat (280 msec). We excluded structural heart disease. In the resting ECG the QTc interval was 420 msec. During Holter monitoring a slight changes of the ST-T segment in V1 were observed (from positive T wave with ST elevation of 1 mm to flat or negative T wave without ST elevation). Additionally, after PMVT a large U-wave (4 mm of amplitude) with the QTU interval of 600 msec and QTUc interval of 662 msec were observed. The U wave disappeared 9 minutes afterwards. The ajmaline test was positive for the Brugada syndrome. The patient received ICD and sotalol, and during 6-month follow-up she remains asymptomatic.     

Relative contributions of a single-admission 12-lead electrocardiogram and early 24-hour continuous electrocardiographic monitoring for early risk stratification in patients with unstable coronary artery disease

Patients with unstable coronary syndromes are a heterogeneous group with varying degrees of ischemia and prognosis. The present study compares the prognostic value of a standard electrocardiogram (ECG) obtained at admission to the hospital with the information from 24-hour continuous electrocardiographic monitoring obtained immediately after admission. The admission ECGs and 24 hours of vectorcardiographic (VCG) monitoring from 308 patients admitted with unstable coronary artery disease were analyzed centrally regarding standard electrocardiographic ST-T changes, ST-vector magnitude (ST-VM), and ST change vector magnitude episodes. End points were death, acute myocardial infarction, and refractory angina pectoris within a 30-day follow-up period. ST-VM episodes (> or = 50 microV for > or = 1 minute) during VCG monitoring was the only independent predictor of death or acute myocardial infarction by multivariate analysis. ST-VM episodes during vectorcardiography was associated with a relative risk of 12.7 for having a cardiac event, hypertension was associated with a relative risk of 1.7, and ST depression on the admission ECG was associated with a relative risk of 5.7. Patients with ST depression at admission had an event rate (death or acute myocardial infarction) of 17% at 30-day follow-up. Patients without ST depression could further be risk stratified by 24 hours of VCG monitoring into a subgroup with ST-VM episodes at similar (8%) risk and a subgroup without ST-VM episodes at low (1%) risk (p = 0.00005). Continuous VCG monitoring provides important information for evaluating patients with unstable coronary artery disease. It is recommended that patients not initially estimated at high risk based on the admission ECG are referred for 24 hours of VCG monitoring for further risk stratification.     

Coronary heart disease and silent myocardial ischemia]

Silent myocardial ischemia was studied in 100 patients with coronary heart disease (CHD), proved by the coronary arteriogram (at least one major coronary artery narrowed by > or = 50%). The study demonstrated that 51 of 100 patients with CHD had episodes of myocardial ischemia by Holter monitoring. In the 51 patients, during daily activities, through 24-hour Holter monitoring, 239 transient episodes of ST depression were detected, 161 of the total were asymptomatic (67.4%). There were no statistically significant differences in the heart rate and the product of heart rate and systolic blood pressure before ST depression between asymptomatic and symptomatic episodes. The heart rate at the time of maximal ST depression during both asymptomatic and symptomatic ischemia increased by 13 and 22 beats/min, respectively, over those before ST depression (P < 0.01); whereas the increase in heart rate during symptomatic ischemia was more significant than during asymptomatic ischemia (P < 0.01). The increase of product of heart rate and systolic blood pressure at the time of maximal ST depression during asymptomatic and symptomatic ischemia were 22.2 and 35.4, respectively, over those before ST depression (P < 0.01). The incidence of silent ischemic episodes in patients with single vessel disease was 81.7% and those with multivessel disease was 61.3% (P < 0.01). The frequency of silent ischemic episodes was maximal (36% of total number of ischemic episodes) between 6 a.m. and 12 a.m. during 24-hour, whereas the incidence of silent ischemic episodes in patients with single vessel disease was similar to that in patients with multivessel disease.(ABSTRACT TRUNCATED AT 250 WORDS)