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.     

Suspected cardiac syncope in elderly patients: use of the 12-lead electrocardiogram to select patients for holter monitoring.

BACKGROUND: Results of 24-hour Holter monitoring in elderly patients are often unhelpful, since the prevalence of asymptomatic arrhythmias increases and their prognostic significance is unclear. We investigated the value of the resting electrocardiogram (ECG) in predicting significant findings on 24-hour Holter recordings in those suspected of having cardiac syncope. OBJECTIVE: To see whether the resting 12-lead ECG can be used as a screening tool to select elderly patients suspected of having cardiac syncope for 24-hour ECG monitoring. METHOD: Comparison of resting 12-lead ECGs and 24-hour Holter tapes in 145 consecutive elderly outpatients suspected of having a cardiac cause for falls, dizziness, or syncope. RESULTS: Four of 30 normal ECGs (13%) showed an abnormality on Holter monitoring as compared with 55 of the 115 abnormal ECGs (47.8%; chi = 11.7143, p < 0.005). In the 'normal' group the 4 abnormal Holter recordings all showed short runs of supraventricular tachycardia, and no intervention resulted. The 115 abnormal resting ECGs showed either ischaemia (n = 27), dysrhythmia (n = 28), sinus bradycardia (n = 22), or conduction defects (n = 38). The 55 of these which showed abnormalities on Holter recordings occurred mostly where the resting ECG showed dysrhythmia (n = 14/28; 50%), bradycardia (n = 19/22; 86.4%), and conduction defect (n = 17/38; 44.7%). Seven patients had complete heart block on Holter, and all had conduction defects on resting ECG (p < 0.0004). Fifteen patients had pauses of longer than 3 s on Holter; all had conduction defect, bradycardia, or dysrhythmias on resting ECG (p < 0.0045). Sixteen patients were paced because of complete heart block or pauses on Holter recordings, and all had either bradycardia or conduction defects on resting ECG, resulting in complete resolution of their symptoms. CONCLUSIONS: Patients with suspected cardiac syncope and normal resting ECGs are unlikely to reveal significant abnormalities on single 24-hour Holter monitoring. Cardiac event recorder or prolonged Holter monitoring may be required in patients with strong clinical history. Those with abnormal ECGs, in particular sinus bradycardia and conduction defects, are highly likely to have significant abnormalities on 24-hour ECG monitoring.     

Holter recording during treadmill testing in assessing myocardial ischemic changes

One hundred forty-four patients underwent a Bruce protocol treadmill exercise test during which an electrocardiogram (ECG) was recorded simultaneously with a 2-channel Holter recorder with bipolar V3- and V5-like leads and by a conventional 12-lead system. Sixty-eight patients had no ST depression on either the Holter or on the 12-lead ECG during the exercise test, whereas in 70 patients ischemic changes were recorded by both methods; thus, in 138 of the 144 patients (96%), the results of the 2 tests were concordant. The severity of ST depression, as judged by the heart rate at which ischemic changes were first noted and the maximal ST depression observed, were similar on both recording systems. The Holter system identified 6 of the 7 patients whose ischemic changes were confined to the inferior wall on the 12-lead ECG. The addition of the V3 lead as a second ischemic lead increased the ischemia detection by 10%. Ninety-five patients also underwent coronary arteriography. In these patients the sensitivity of the Holter system during exercise in detecting significant coronary artery disease was 81% and that of 12-lead ECG was 84%, the specificity was 85% and 85%, respectively, and the positive predictive value 91% and 91%, respectively. Thus, the 2-channel Holter recording system with bipolar V3- and V5-like leads was as accurate as the 12-lead system in detecting ischemic changes during exercise and proved that ambulatory monitoring system can reliably reproduce ST segment.     

Accuracy of the EASI 12-lead electrocardiogram compared to the standard 12-lead electrocardiogram for diagnosing multiple cardiac abnormalities

This study was performed to compare a derived 12-lead electrocardiogram (ECG) using a simple 5-electrode lead configuration (EASI 12-lead) with the standard ECG for multiple cardiac diagnoses. Accurate diagnosis of arrhythmias and ischemia often require analysis of multiple (ideally, 12) ECG leads; however, continuous 12-lead monitoring is impractical in hospital settings. EASI and standard ECGs were compared in 540 patients, 426 of whom also had continuous 12-lead ST segment monitoring with both lead methods. Independent standards relative to a correct diagnosis were used whenever possible, for example, echocardiographic data for chamber enlargement-hypertrophy, and troponin levels for acute infarction. Percent agreement between the 2 methods were: cardiac rhythm, 100%; chamber enlargement-hypertrophy, 84%–99%; right and left bundle branch block, 95% and 97%, respectively; left anterior and posterior fascicular block, 97% and 99%, respectively; prior anterior and inferior infarction, 95% and 92%, respectively. There was very little variation between the 2 lead methods in cardiac interval measurements; however, there was more variation in P, QRS, and T-wave axes. Of the 426 patients with ST monitoring, 138 patients had a total of 238 ST events (26, acute infarction; 62, angioplasty-induced ischemia; 150, spontaneous transient ischemia). There was 100% agreement between the 2 methods for acute infarction, 95% agreement for angioplastyinduced ischemia, and 89% agreement for transient ischemia. EASI and standard 12-lead ECGs are comparable for multiple cardiac diagnoses; however, serial ECG changes (eg, T-wave changes) should be assessed using one consistent 12-lead method.     

Holter ECG in evaluating myocardial ischemia. Validation using the exercise test

OBJECTIVES: Validation of ST-T ischemic changes in the Holter system by those recorded in the 12-lead ECG during the exercise test. DESIGN: The changes induced by the exercise test in the ST segment of the two Holter leads--aVF e V5 like--were compared with the changes simultaneously registered in the 12-lead ECG. SETTING: Exercise Test Laboratory and Holter Laboratory of the UTIC-Arsénio Cordeiro. Hospital de Santa Maria de Lisboa. PATIENTS: 31 patients, 23 male and 8 female, with a mean age of 55 +/- 7 years, 84% with ischemic heart disease. METHODS: The patients underwent a treadmill exercise test. 28 with the Bruce protocol and 3 with the Naugton protocol, during which the electrocardiogram was registered simultaneously with a 2-channel Holter recorder and by a conventional 12-lead system. The changes induced in the ST segment in the two systems were compared. RESULTS: The results of the two tests were concordant in 94% of the patients. In 4 patients (13%) there was not a good correlation between the inferior and anterior leads of the two methods, which diverged mainly between the Holter lead aVF and the inferior leads of the conventional ECG. The morphology of the ST depression was similar in both methods, and the severity of ST depression as judged by its amplitude showed an excellent positive linear correlation (r = 0.8542, p less than 0.001). CONCLUSIONS: The sensitivity and the specificity of the Holter system is similar to the conventional 12-lead ECG in detecting ischemic changes during exercise whenever they have electrocardiographic evidence.     

Clinical significance of silent ischemia in unstable angina pectoris

In a prospective study the significance of silent ischemia was evaluated in 66 patients with a clinical diagnosis of unstable angina (no requirement for reversible ST-T changes during pain on 12-lead electrocardiograms before entry), and the results of continuous 2-channel electrocardiographic (ECG) recordings, begun within 24 hours of admission, were compared with other clinical and ECG predictors of adverse outcome. Ischemic changes were detected in 7 patients (11%) during a mean of 41 hours of recording. There were 37 episodes of transient ST-segment change (16 ST elevation, 21 ST depression) of which 11 (30%) were symptomatic and 26 (70%) were silent. All 7 patients had at least 1 silent episode and 5 also had symptomatic episodes during the recording but only 2 patients had exclusively silent episodes. During a mean follow-up of 13.3 months, 3 patients died, 5 had a nonfatal myocardial infarction and 32 required revascularization. Although transient myocardial ischemia during the continuous ECG recording, whether silent or symptomatic, was a specific predictor of subsequent nonfatal myocardial infarction or death (specificity 92%), its sensitivity for these events was low (25%). In contrast, recurrent rest pain (greater than or equal to 1 episode) occurred in all patients with these serious adverse events (sensitivity 100%, specificity 49%). Transient ischemia occurs infrequently during continuous ECG recordings in patients with unstable angina not selected by reversible ST-T changes on a 12-lead electrocardiogram at entry. Recurrent rest pain after hospital admission is a more sensitive predictor of serious events in this group.     

Absence of ST elevation in ECG leads V7, V8, V9 in ischaemia of non-occlusive aetiologies

BACKGROUND AND OBJECTIVE: Occlusion of the circumflex coronary artery may present with either ST elevation typical of inferior or lateral myocardial infarction, ST depression or a normal 12-lead electrocardiogram (ECG). In patients presenting with ST depression, concomitant ST elevation in the posterior leads V7, V8 and V9 is believed to reflect ST-elevation myocardial infarction of the posterior wall. However, to be confident of this diagnosis, it is necessary to know that posterior ST depression does not occur in acute subendocardial ischaemia. METHODS AND RESULTS: We have prospectively recorded leads V7, V8 and V9 simultaneously with the standard 12-lead ECG in patients who underwent treadmill stress test. Group A consists of 35 patients who showed ischaemic praecordial ST depression in their 12-lead ECGs during treadmill stress test and subsequent angiographic documentation of significant coronary artery disease. Group B consists of 35 subjects who showed normal ECG findings during treadmill stress test. In none of the Group A or B patients was there ST elevation in leads V7, V8 or V9 either at rest or at peak exercise. ST depression was seen in 69% in V7, 31% in V8 and 11% in V9 in the Group A patients at peak exercise. CONCLUSION: ST elevation in leads V7, V8 and V9 is uncommon in patients presenting with subendocardial ischaemia. Therefore, in patients presenting with acute chest pain and ST depression in the 12-lead ECG, concomitant posterior ST elevation may be a reliable indicator of ST elevation posterior MI. This is likely due to circumflex artery occlusion and may require thrombolytic therapy.     

New electrocardiographic criteria for posterior wall acute myocardial ischemia validated by a percutaneous transluminal coronary angioplasty model of acute myocardial infarction

The standard 12-lead electrocardiogram (ECG) fails to detect ST-segment elevation in patients with posterior wall acute myocardial ischemia. However, additional posterior leads V(7-9) provide limited additional diagnostic information to the standard 12-lead ECG when an ischemic criterion of 1-mm ST elevation is used. No study is available to delineate the ischemic criteria in the posterior electrocardiographic leads. Continuous 15-lead ECGs (standard 12 lead + V(7-9)) were recorded in 53 subjects undergoing elective left circumflex coronary angioplasty (posterior ischemia model). ST amplitudes (J + 60 ms) at preangioplasty baseline were subtracted from maximal ST amplitudes during balloon occlusion to create a positive or negative change score (DeltaST) for each of the 15 leads. During 53 left circumflex occlusions, 26 subjects (49%) had DeltaST elevation of > or = 1 mm and 24 subjects (45%) had DeltaST elevation ranging from 0.5 to 0.95 mm in > or = 1 posterior leads. Five subjects (9%) had DeltaST elevation of > or = 1 mm in the posterior leads without DeltaST elevation anywhere in any of the 12 leads. The sensitivity in detecting myocardial ischemia using 15-lead ECGs (58%) was not statistically different from the standard 12-lead ECG (49%) (p = 0.06). Adjusting the ischemic criterion from 1 to 0.5 mm in V(7-9) significantly improved the sensitivity from 49% in the 12-lead ECG to 94% in the 15-lead ECG (p = 0.000). In addition, 12 subjects (23%) had posterior ST-segment elevation without anterior ST-segment depression. Thus, posterior leads V(7-9) contribute significant additional diagnostic information above and beyond the standard 12-lead ECG only when a new ischemic criterion of 0.5 mm instead of 1 mm ST elevation is applied to the posterior leads.     

Holter monitor recording for the detection of myocardial ischemia: validation of a new recorder and chest lead positions.

OBJECTIVE: To validate the Reynolds Tracker II Holter system using newly described lead positions during both upright treadmill exercise and in the recumbent position following exercise. The specific lead positions HL1 and HL2 were chosen to detect anterior and postero-inferior myocardial ischemia, respectively, without interfering with the surgical field in the hypothetical situation of open-heart surgery. Similar lead positions have previously been used to monitor myocardial ischemia during induction of anesthesia, but have never been validated by comparison with 12-lead modified electrocardiogram (ECG) recording. METHODS: To validate the authors' 'chosen' Holter lead positions (HL1 and HL2), both at the fifth intercostal space just lateral to the midclavicular line and on the back, 1.5 cm to the left of the vertebral column, respectively) 49 candidates for routine treadmill exercise testing underwent a simultaneous Holter monitor recording using the described lead positions. DATA ANALYSIS: The Holter ECG recordings were separately analyzed by two physicians unaware of patients' identity. RESULTS: Using the modified 12-lead ECG as the 'gold standard', the sensitivity of Holter for detecting ischemia (defined as 0.1 mV or ST depression lasting at least 60 s) was 77 and 83%, and its specificity was 100 and 92%, respectively, for observers 1 and 2. Most episodes of myocardial ischemia were detected by the modified lead V5 for the 12-lead ECG and by HL1 for the Holter recording. Using the Holter Tracker II system and the chosen lead positions, it was possible to detect successfully most episodes of exercise-induced myocardial ischemia. CONCLUSION: Holter monitoring might be useful in detecting perioperative myocardial ischemia.     

A vector-based, 5-electrode, 12-lead monitoring ECG (EASI) is equivalent to conventional 12-lead ECG for diagnosis of acute coronary syndromes

AIMS: The conventional 12-lead electrocardiogram (cECG) derived from 10 electrodes using a cardiograph is the gold standard for diagnosing myocardial ischemia. This study tested the hypothesis that a new 5-electrode 12-lead vector-based ECG (EASI; Philips Medical Systems, formerly Hewlett Packard Co, Boeblingen, Germany) patient monitoring system is equivalent to cECG in diagnosing acute coronary syndromes (ACSs). METHODS: Electrocardiograms (EASI and cECG) were obtained in 203 patients with chest pain on admission and 4 to 8 hours later. Both types of ECGs were graded as ST-elevation myocardial infarction if at least 1 of the 2 consecutive recordings showed ST elevation more than 0.2 mV, as ACS if one or both showed ST elevation less than 0.2 mV, T-wave inversion, or ST depression. Otherwise, the ECG was graded negative. RESULTS: Final diagnosis was identical in 177 patients (87%; 95% confidence interval [CI], 82%-91%; kappa = 0.81; SE = 0.035). ST-elevation myocardial infarction was correctly identified or excluded by EASI with a specificity of 94% (95% CI, 89%-97%) and a sensitivity of 93% (95% CI, 86%-97%; using cECG as the gold standard). Of 118 patients with enzyme elevations, an almost identical number (72 [61% by EASI] and 73 [62% by cECG]) had ST elevations. Both techniques were equivalent in predicting subsequent enzyme elevation (identical, 108/143; 75% of ACS and ST-elevation myocardial infarction ECGs by EASI and cECG). Thus, both ECG methods had exactly the same specificity of 59% (95% CI, 48%-69%) and sensitivity of 91% (95% CI, 85%-96%) for detecting myocardial injury. CONCLUSION: EASI is equivalent to cECG for the diagnosis of myocardial ischemia.     

Evaluation of a newly devised three-lead Holter recording during treadmill testing in the diagnosis of ischemic ST changes

Sixty-five patients (54 men, 11 women) with angina pectoris were studied using a technique for recording a 3-lead electrocardiogram without increasing the number of channels and electrodes in the commercial 2-channel Holter recorder. In 52 of the 65 patients, simultaneous ECGs with both the 3-lead Holter method and the conventional 12-lead system during treadmill exercise testing were performed. The results of the two systems in detecting significant ST depressions were consistent in 51 of 52 patients (98%). Twenty-seven of the 32 patients with significant coronary stenosis showed ST depressions during exercise both in the 3-lead Holter and the 12-lead ECG systems. There were cases in which ST depressions were confined only to the CM2 lead (n = 1), the CM5 lead (n = 18) or the CMf lead (n = 3). This indicates that at least three leads are needed in the Holter system for the detection of certain ST changes. The sensitivity of the Holter system during exercise in detecting significant coronary artery disease was the same as that of the 12-lead system (84%). Two of the total 65 patients had variant angina at night. No ST changes in the CM5 lead were observed in either case. Thus, the 3-lead Holter monitoring technique is as accurate as the 12-lead system for the detection of ischemic ST depressions associated with coronary stenosis and is unlikely no miss the signs of variant angina. In addition, this technique is expandable since it can continuously switch between leads using the same channel.     

Can myocardial ischemia be recognized by the exercise electrocardiogram in coronary disease patients with abnormal resting Q waves?

This study was performed in order to determine whether exercise-induced myocardial ischemia demonstrated by thallium-201 imaging could be detected by ST segment shifts in patients with abnormal Q waves at rest. Fifty-four patients with coronary artery disease and exercise-induced thallium-201 defects were compared to 22 patients with similar Q wave patterns but without thallium-201 exercise defects and to 14 normal subjects. Exercise data were analyzed visually in the 12-lead ECG and for spatial ST vector shifts. Both ST segment depression observed on the 12-lead ECG and spatial criteria were reasonably sensitive and specific for ischemia when the resting ECG showed no Q waves or inferior Q waves (range 69% to 93%). However, when anterior Q waves were present, ST segment shifts could not distinguish patients with ischemia from those with normal perfusion as determined by thallium imaging.     

ST Segment Analysis by Holter Monitoring:

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.     

Continuous 12-lead electrocardiographic ST monitoring adds prognostic information to the thrombolysis in myocardial infarction risk score in patients with non-ST-elevation acute coronary syndromes

BACKGROUND: Continuous 12-lead electrocardiographic (ECG) ST monitoring and the Thrombolysis In Myocardial Infarction Risk Score (TIMI-RS), both have been shown to be useful for early risk stratification in patients with non-ST elevation acute coronary syndromes (NSTACS). HYPOTHESIS: Transient ST ischemic events, detected by continuous 12-lead ECG ST monitoring, early in the course of NSTACS, may add prognostic information to the TIMI-RS. METHODS: In all, 567 consecutive patients with a NSTACS underwent 24-h continuous 12-lead ECG ST monitoring. An ST ischemic event was defined as a transient ST shift in any lead of > or = 0.10 mV compared with the reference ECG, lasting for > or = 1 min. RESULTS: The incidence of the composite of death, nonfatal myocardial infarction (or reinfarction) and recurrent ischemia by Day 14 was 22.2%. By Day 30, the incidence of the composite of death and nonfatal myocardial infarction (or reinfarction) was 14.7%. There was a significantly increased risk of 14-day (p value for trend < 0.001) or 30-day (p value for trend <0.001) composite endpoint with increasing of TIMI-RS. Moreover, the occurrence of > or = 1 ST shifts during ST monitoring was associated with a significantly increased risk of 14- (p value < 0.001) or 30-day (p value < 0.001) composite endpoint, and this was true throughout the groups of TIMI-RS. CONCLUSIONS: The present study suggests that continuous 12-lead ECG ST monitoring, early in the course of NSTACS, may serve as an affordable tool to add prognostic information to the TIMI-RS.     

New holter monitoring analysis system: a calculation of the lead vectors.

BACKGROUND: A new system of synthesizing a 12-lead electrocardiogram (Syn-ECG) with practically identical waveforms to the standard 12-lead ECG (Stn-ECG) from 3-channel ECGs recorded by Holter monitoring has been developed. METHODS AND RESULTS: The study group comprised 16 healthy individuals and 13 patients with abnormal ECGs. The bipolar eV1, eV5 and eVF leads were recorded using digital Holter monitoring and nine Syn-ECGs, corresponding to each lead of the Stn-ECG, were synthesized. The 9 ECGs consisted of a theoretical Syn-ECG and 8 Syn-ECGs positioned around the theoretical Syn-ECG at 3 cm intervals on the Frank's image surface. Of the 9 ECGs, the Syn-ECG with the maximum product of the cross-correlation coefficient of the QRS wave and that of the T wave, was automatically selected as the optimal Syn-ECG. The amplitude data from the QRS wave, R wave, T wave, and ST level, and also the amplitude ratio of the R wave, T wave to the QRS wave, were significantly well correlated between the Syn-ECG and Stn-ECG. CONCLUSIONS: A practically identical ECG morphology, comparable with a Stn-ECG, was successfully created using this system.     

Electrocardiographic classification of acute coronary syndromes: a review by a committee of the International Society for Holter and Non-Invasive Electrocardiology

The electrocardiogram (ECG) remains the most immediately accessible and widely used diagnostic tool for guiding emergency treatment strategies. The ECG recorded during acute myocardial ischemia is of diagnostic, therapeutic, and prognostic significance. In patients with myocardial ischemia as a result of decreased blood supply, the initial 12-lead ECG typically shows (1) predominant ST-segment elevation (STE) as part of STE acute coronary syndrome (STE-ACS), or (2) no predominant STE, that is, non-STE ACS (NSTE-ACS). Patients with predominant STE are classified as having either aborted myocardial infarction (MI) or ST-elevation MI (STEMI) based on the absence or presence of biomarkers of myocardial necrosis. The MI may be aborted either by spontaneous or therapeutic reperfusion of the ischemic myocardium before development of myocardial cell necrosis. NSTE-ACS patients are classified as having either unstable angina or NSTE-MI, based also on the absence or presence of biomarkers of mycardial necrosis.The information obtained from the 12-lead ECG at presentation should be complemented by repeated ECGs especially during symptoms indicative of ischemia and, if applicable, by comparing the findings with reference ECGs. Also, continuous ECG recording in a coronary care setting, including the comparison of ECGs with and without pain, adds to the information gained at patient presentation.In this article, mechanisms of ischemic ECG changes and the ECG patterns recorded in both STE-ACS and NSTE-ACS are described. ECG patterns of NSTE-ACS, which include ST depression, negative T wave, and even normal ECG, need to be better defined in future studies to correlate them with the severity and extent of ischemia and to explore to what extent they are explained by acute active ischemia or represent consequences of ischemia. One of the aims of this article is to propose a classification of the ECG patterns encountered in different clinical scenarios of ACS. How these patterns will aid in guiding the diagnostic and therapeutic process is discussed.     

Frequency of silent myocardial ischemia with 12-lead ST segment monitoring in the coronary care unit: are there sex-related differences?

BACKGROUND: Ischemia that occurs in the coronary care unit (CCU), whether symptomatic or silent, is associated with significant in-hospital and out-of-hospital complications. Studies have reported that more than 90% of ischemic episodes are silent in patients with unstable angina who are treated in the CCU with maximal medical therapy. Prior reports indicate that women complained more frequently of chest pain than men did. PURPOSE: The aim of this study was to compare the frequency of silent myocardial ischemia in men versus women with use of continuous 12-lead ST segment monitoring in the CCU. A secondary goal was to determine whether silent ischemia was associated with less ST segment deviation as compared with symptomatic ischemia. METHOD: Patients admitted for treatment of acute coronary syndrome in the CCU and who subsequently had 1 or more ischemic events during their monitoring period were selected for this analysis. All patients were continuously monitored (42.5 hours +/- 37.6) in the CCU with the EASI (Zymed Medical Instruments, Camarillo, Calif) 12-lead electrocardiogram (ECG) system that derives 12 leads with use of 3 information channels and 5 electrodes. RESULTS: Of 491 patients, 128 (91 men and 37 women) had at least 1 episode of transient myocardial ischemia. Men and women did not differ in their proportion of chest pain during ischemia (men 27% and women 21%, NS). For both men and women, ST segment deviation was significantly greater during symptomatic ischemia compared with silent ischemia. CONCLUSION: There are no sex-related differences in ischemic events in the CCU in regards to the variables of chest pain and ST magnitude. Therefore, because chest pain is not a reliable indicator of myocardial ischemia in the CCU, regardless of sex, patients should be adequately monitored for ischemic events.     

The diagnostic impact of prehospital 12-lead electrocardiography

STUDY HYPOTHESIS: It is feasible to apply prehospital 12-lead electrocardiography to most stable prehospital chest pain patients. Prehospital diagnostic accuracy is improved compared with single-lead telemetry. POPULATION: One-hundred sixty-six stable adult patients who sought paramedic evaluation for a chief complaint of nontraumatic chest pain. METHODS: One-hundred fifty-one prehospital 12-lead ECGs of diagnostic quality were obtained by paramedics on 166 adult patients presenting with nontraumatic chest pain. Paramedics and base station physicians were blinded to the information on acquired prehospital 12-lead ECGs and treated patients according to current standard of care-clinical diagnosis and single-lead telemetry. Final hospital diagnoses were classified into three groups: acute myocardial infarction (24); suspected angina or ischemia (61); and nonischemic chest pain (66). Paramedics and base station physicians' clinical diagnoses and prehospital and emergency department ECGs were similarly classified and compared. Prehospital and ED 12-lead ECGs were read retrospectively by two cardiologists. RESULTS: Paramedics achieved a high success rate (98.7%) in obtaining diagnostic quality prehospital 12-lead ECGs in 94.6% of eligible prehospital patients. For patients with acute myocardial infarction, prehospital ECG alone had significantly higher specificity than did the paramedic clinical diagnosis (99.2% vs 70.9%; P less than .001), and significantly higher positive predictive value (92.9% vs 32.7%; P less than .001). For patients with angina, combining the paramedic clinical diagnosis and the prehospital ECG significantly improved sensitivity (90.2% vs 62.3%; P less than .001) and increased negative predictive value (88.9% vs 71.3%; P less than .02) compared with paramedic clinical diagnosis alone. There was a high concordance between prehospital and ED ECG diagnosis (99.3% for acute myocardial infarction and 92.8% for angina). Furthermore, ten patients whose prehospital ECGs demonstrated ischemia and who had final hospital diagnoses of angina or acute myocardial infarction were mistriaged by paramedics and/or received no base station physician-directed therapy. CONCLUSION: It is feasible to apply prehospital 12-lead electrocardiography to most stable prehospital chest pain patients. Prehospital 12-lead ECGs have the potential to significantly increase the diagnostic accuracy in chest pain patients, approach congruity with ED 12-lead ECG diagnoses, and may allow for consideration of altering and improving prehospital and hospital-based management in this patient population.     

Comparing the consistency of electrocardiogram interval measurements by resting ECG versus 12-lead Holter

In clinical trials, traditionally only a limited number of 12-lead resting electrocardiograms (ECGs) can be recorded and, thus, long intervals may elapse between assessment timepoints and valuable information may be missed during times when patients' cardiac electrical activity is not being monitored. These limitations have led to the increasing use of Holter recorders which provide continuous data registrations while reducing the burden on patients and freeing up time for clinical trial staff to perform other tasks. However, there is a shortage of data comparing the two approaches. In this study, data from a randomized, double-blind, four-period, crossover thorough QT study in 40 healthy subjects were used to compare continuous 12-lead Holter recordings to standard 12-lead resting ECGs which were recorded in parallel. Heart rate and QT interval data were estimated by averaging three consecutive heartbeats. Values exceeding the sample average by more than 5% were tagged as outliers and excluded from the analysis. Visual comparisons of the ECG waveforms of the Holter signal showed a good correlation with resting ECGs at matching timepoints. Resting ECG data revealed sex differences that Holter data did not show. Specifically, women were found to have a longer QTcF of 20 ms, while men had a lower heart rate. We found that continuous recordings provided a more accurate reflection of changes in cardiac electrical activity over 24 hr. However, manual adjudication is still required to ensure the quality and accuracy of ECG data, and that only artifacts are removed thereby avoiding loss of true signals.     

Frequency, characteristics, and clinical significance of transient ST segment elevation in patients with acute coronary syndromes.

BACKGROUND: Prior investigations of transient myocardial ischaemia have focused on ST depression events. Therefore, the purpose of this analysis was to determine the frequency, characteristics, and clinical significance of transient ST segment elevation in patients with acute coronary syndromes. METHODS: A secondary analysis from two prospective studies utilizing 12-lead ST segment monitoring was used to compare ST elevation vs ST depression events. RESULTS: Of 868 patients, 177 (20%) had 574 events (242, ST elevation; 332, ST depression). Patients with ST elevation were more likely to have single vessel coronary artery disease, whereas patients with ST depression were more likely to have triple vessel coronary artery disease. ST elevation events were of shorter duration, more often associated with chest pain, and had greater ST changes than ST depression events. There was no difference in clinical outcome between patients with ST elevation vs depression; however, those with ST events were more likely to have adverse hospital outcomes (OR, 3.67) or death (OR, 2.03) than patients without ST events. After controlling for clinical prognostic factors, transient ST events observed with continuous ST monitoring predicted hospital death independently from signs of ischaemia on the initial standard 12-lead ECG. CONCLUSIONS: Transient ST elevation is nearly as prevalent as transient ST depression in patients with acute coronary syndromes. Since the vast majority of ST events are brief and otherwise clinically silent, ST segment monitoring is more efficacious in detecting ischaemic events and in predicting adverse clinical outcomes than patients' symptoms or the initial standard 12-lead ECG.