Arrhythmias in patients with acute coronary syndrome in the first 24 hours of hospitalization.

OBJECTIVES: In patients with acute coronary syndrome (ACS), we sought to: 1) describe arrhythmias during hospitalization, 2) explore the association between arrhythmias and patient outcomes, and 3) explore predictors of the occurrence of arrhythmias. METHODS: In a prospective sub-study of the IMMEDIATE AIM study, we analyzed electrocardiographic (ECG) data from 278 patients with ACS. On emergency department admission, a Holter recorder was attached for continuous 12-lead ECG monitoring. RESULTS: Approximately 22% of patients had more than 50 premature ventricular contractions (PVCs) per hour. Non-sustained ventricular tachycardia (VT) occurred in 15% of patients. Very few patients (≤ 1%) had a malignant arrhythmia (sustained VT, asystole, torsade de pointes, or ventricular fibrillation). Only more than 50 PVCs/hour independently predicted an increased length of stay (p < .0001). No arrhythmias predicted mortality. Age greater than 65 years and a final diagnosis of acute myocardial infarction independently predicted more than 50 PVCs per hour (p = .0004). CONCLUSIONS: Patients with ACS seem to have fewer serious arrhythmias today, which may have implications for the appropriate use of continuous ECG monitoring.

A simple strategy improves prehospital electrocardiogram utilization and hospital treatment for patients with acute coronary syndrome (from the ST SMART Study).

Although the American Heart Association recommends a prehospital electrocardiogram (ECG) be recorded for all patients who access the emergency medical system with symptoms of acute coronary syndrome (ACS), widespread use of prehospital ECG has not been achieved in the United States. A 5-year prospective randomized clinical trial was conducted in a predominately rural county in northern California to test a simple strategy for acquiring and transmitting prehospital ECGs that involved minimal paramedic training and decision making. A 12-lead ECG was synthesized from 5 electrodes and continuous ST-segment monitoring was performed with ST-event ECGs automatically transmitted to the destination hospital emergency department. Patients randomized to the experimental group had their ECGs printed out in the emergency department with an audible voice alarm, whereas control patients had an ECG after hospital arrival, as was the standard of care in the county. The result was that nearly 3/4 (74%) of 4,219 patients with symptoms of ACS over the 4-year study enrollment period had a prehospital ECG. Mean time from 911 call to first ECG was 20 minutes in those with a prehospital ECG versus 79 minutes in those without a prehospital ECG (p <0.0001). Mean paramedic scene time in patients with a prehospital ECG was just 2 minutes longer than in those without a prehospital ECG (95% confidence interval 1.2 to 3.6, p <0.001). Patients with non-ST-elevation myocardial infarction or unstable angina pectoris had a faster time to first intravenous drug and there was a suggested trend for a faster door-to-balloon time and lower risk of mortality in patients with ST-elevation myocardial infarction. In conclusion, increased paramedic use of prehospital ECGs and decreased hospital treatment times for ACS are feasible with a simple approach tailored to characteristics of a local geographic region.

Estimated body surface potential maps in emergency department patients with unrecognized transient myocardial ischemia.

BACKGROUND: We report on 5 patients who presented to the emergency department (ED) with chest pain, had negative serum troponin levels, and were discharged with a presumed noncardiac diagnosis. Thereafter, retrospective analysis of Holter monitoring data recorded for a clinical trial revealed ST events indicative of transient myocardial ischemia that was unrecognized clinically. STUDY AIM: The purpose of this analysis was to determine whether initial body surface potential maps estimated from optimal ischemia electrode sites estimated body surface potential map (EBSPM) showed signs of ischemia in the missed ischemia group that could have prevented misdiagnosis. METHODS: This is a secondary analysis of data from a prospective clinical trial in which patients were attached to 2 Holter monitor devices for simultaneous recordings. One Holter device recorded a standard Mason-Likar 12-lead electrocardiogram (ECG) and the other recorded a 10-electrode lead set considered optimal for ischemia detection. A body surface potential map was then estimated from the optimal lead set. RESULTS: At 1 year, 2 of the 5 patients with missed ischemia died and a third had an acute myocardial infarction (MI) (40% mortality, 60% death/nonfatal MI). In comparison, 1-year mortality was 5.7% in 159 similar patients treated for unstable angina at the same institution over the same period (P = .037). The initial standard ECG showed no abnormalities in 3 patients and showed left ventricular hypertrophy in 1. The fifth patient with a history of recent MI had slight ST elevation in leads III and aVF and Q waves that were considered indicative of recent (not acute) MI. EBSPM data recorded at the time of ED presentation matched the standard ECG (normal in 3, left ventricular hypertrophy or inconclusive in 2). During transient ischemia, all 5 EBSPMs showed areas of ischemia overlapping with standard electrode sites. CONCLUSION: Patients evaluated in the ED for chest pain are at high risk for death or nonfatal MI if they have ischemic events with continuous ST-segment monitoring that are unrecognized clinically. In this small cohort with unrecognized ischemia, the initial body surface potential maps estimated from optimal ischemia electrode sites did not improve on 12-lead ST-segment monitoring to identify this high-risk group.

Karhunen-Loève representation distinguishes ST-T wave morphology differences in emergency department chest pain patients with non-ST-elevation myocardial infarction versus nonacute coronary syndrome.

UNLABELLED: Patients presenting to the emergency department with chest pain are triaged to early reperfusion therapies based on their initial 12-lead electrocardiogram (ECG). The standard 12-lead ECG lacks sensitivity to detect acute myocardial infarction (AMI). Electrocardiographic diagnosis of non-ST-elevation myocardial infarction (non-STEMI) is especially difficult and is delayed until cardiac biomarkers turn positive, indicating onset of myocardial necrosis. STUDY AIMS: The purpose of this analysis was to extract global ST-T waveform features from patients with chest pain, compare these features in patients with and without AMI, and then identify features that distinguish diagnostic categories. METHODS: This is a secondary analysis of data from the Ischemia Monitoring and Mapping in the Emergency Department in Appropriate Triage and Evaluation of Acute Ischemic Myocardium study, a prospective clinical trial in which patients were attached to Holter monitor devices to obtain 24 hours of continuous ECG data. Digital recordings from 176 patients were analyzed: 88 with AMI (STEMI and non-STEMI) and 88 without AMI or unstable angina. The non-acute coronary syndrome (ACS) group was further subdivided into those with non-ACS cardiac conditions such as heart failure and those without cardiac disease who had noncardiac chest pain. For each patient, 10 consecutive waveforms were obtained within the first 120 minutes of emergency department presentation. The waveforms were time-aligned to the QRS, signal-averaged, baseline-adjusted. ST-T waveforms were complied according to diagnostic category and pooled for further analysis. Eigenvector-lead feature coefficients (Karhunen-Loève [K-L] coefficients) were obtained for each patient by taking the dot product of the ST-T wave (ST segment or entire waveform) and the first 3 common eigenvectors, producing 24 K-L coefficients. Cumulative probability distribution function curves were plotted for each diagnostic category. Statistical significance of category coefficient distribution differences was determined. Multinomial regression was used to assess accuracy of feature coefficients to predict diagnostic category. RESULTS: Non-STEMI and non-ACS cardiac category K-L coefficient curves were statistically different in 11 of 24 feature curves (P < .001-.047). ST-segment (50 samples) coefficients predicted non-ACS cardiac patients 11.5% more often (P = .02) than those derived from the entire ST-T wave. CONCLUSION: Patients diagnosed with non-STEMI have distinct distribution of K-L coefficients compared with non-ACS cardiac patients. Coefficients from the first 50 samples of the ST-T wave (ST segment) better predict diagnostic category than do coefficients derived from the entire ST-T wave. Karhunen-Loève coefficient feature analysis may provide early diagnostic information to distinguish patients with non-STEMI vs non-ACS cardiac patients.

Dynamic tracking of ischemia in the surface electrocardiogram.

BACKGROUND: Accurate detection of the earliest signs of ischemia on the surface electrocardiogram (ECG) is essential for timely diagnosis and management of potentially life-threatening ischemic events. Yet, accuracy of ischemia analysis in ECG monitors remains suboptimal because of a number of confounding factors, including changes in body position and other artifacts. Hence, the goals of this study were (1) to examine the duration and time course of ischemic events and (2) to compare ECG changes caused by "true" ischemic events with those caused by changes in body position. Continuous, 12-lead Holter ECGs obtained from patients who presented to the emergency department with chest pain and enrolled in the Ischemia Monitoring and Mapping in the Emergency Department in Appropriate Triage and Evaluation of Acute Ischemic Myocardium study were analyzed. Holter recordings were initiated within the first 40 minutes after patients' arrival to the emergency department. Here we present preliminary results. METHODS: Twelve patients (age, 59 +/- 16 years; 5 women, 2 with a final diagnosis of non-ST-segment elevation myocardial infarction, 4 with unstable angina, and 6 with other cardiovascular diseases), in whom ischemic ST deviations were identified on Holter data, underwent 4 consecutive, 2-minute recordings in the following body positions: (1) supine, (2) on the left side, (3) on the right side, and (4) sitting (or standing) upright. After baseline correction, beat-to-beat changes in QRS and ST-T segments were examined in all 8 channels and the root-mean-square curve by using an adaptive algorithm that computes the slope, amplitude, duration, area, and the Karhunen-Loève-derived representation of the corresponding segment. To prevent possible biases toward patients with more frequent ischemic events, a single index event was chosen for analysis in each patient. There were 3 ST-elevation events and 9 ST-depression events; these events reached the maximum ST deviation 11 +/- 8 hours (mean +/- SD) after the beginning of the recording. RESULTS AND CONCLUSIONS: In most patients with transient myocardial ischemia, the microvolt-level, subthreshold deviation of the ST segment developed gradually, over 15 to 20 minutes, until it reached the maximum, superthreshold level. Despite the different ischemia localizations, the root-mean-square curve allowed accurate detection of significant changes in the ST segment in the studied group (Friedman analysis of variance for repeated measurements over a 1-hour interval). Changes in body position could be identified by tracking dynamics of the QRS pattern/axis. Adaptive algorithms for tracking of the ST dynamics with simultaneous tracking of the patterns of QRS complexes to discriminate the true and "false"-positive events are presented and discussed.

Novel electrocardiogram configurations and transmission procedures in the prehospital setting: effect on ischemia and arrhythmia determination.

AIM: The aims of this report are to (1) describe a novel prehospital 12-lead electrocardiogram (ECG) configuration and transmission procedure used in the Synthesized Twelve-lead ST Monitoring and Real-time Tele-electrocardiography Study and to (2) report on the frequency of arrhythmias in field ECGs compared with the first hospital ECG. METHODS: The Synthesized Twelve-lead ST Monitoring and Real-time Tele-electrocardiography Study is a 5-year randomized clinical trial ending in 2008. All emergency vehicles responding to 911 calls in Santa Cruz County, Calif, have been equipped with portable monitor defibrillators with a special study software that (1) synthesizes a 12-lead ECG from 5 electrodes, (2) measures ST amplitudes in all 12 leads every 30 seconds, and (3) automatically transmits an ECG to the target emergency department if there is a change in ST amplitude of 200 microV in 1 lead or more or 100 microV in 2 contiguous leads or more lasting 2.5 minutes. An initial ECG is transmitted by paramedics, which activates the software. Subsequent transmissions of ST event ECGs occur automatically without paramedic decision making. RESULTS: Prehospital ECGs had a greater frequency of arrhythmias than the first hospital ECG in the group as a whole (n = 433; 33.3% vs 28.9%; P < or = .001), as well as the subgroup with acute coronary syndrome (n = 185; 30.3% vs 26.5%; P < or = .001). More tachyarrhythmias occurred in the field and slightly more bradyarrhythmias occurred at the time of the first hospital ECG. CONCLUSIONS: Prehospital continuous 12-lead ST-segment ischemia monitoring with computer-assisted automatic mobile telephone transmission of ST event ECGs to the target hospital is feasible. More arrhythmias occur in the prehospital phase than are evident on the first hospital ECG.