Long-term prognostic value and therapeutic implications of continuous ST-segment monitoring in acute coronary syndrome

Usefulness of Serial 12-Lead Electrocardiograms in Predicting 30-Day Outcomes in Patients With Undifferentiated Chest Pain (the ASAP CATH Study)

An initial electrocardiogram (ECG) and serial troponin measurements are both independently and incrementally predictive of acute coronary syndrome in patients presenting with undifferentiated chest pain in the Emergency Department (ED). However, it is unclear if serial (ECGs) add significant to the contemporary diagnostic evaluation of this patient group. The ASAP CATH study was a single center, prospective study that enrolled patients presenting to an ED with undifferentiated chest pain. In addition to standard clinical evaluation, serial ECGs were performed at 90-minute intervals to evaluate whether serial changes suggestive of ischemia developed (Q waves, ST elevation or depression, or T-wave inversion). Total 365 subjects were enrolled from March 2014 to May 2015. Serial ECG changes developed in 6.6% (n = 24 of 365), the most common being the development of T-wave inversion (66.7%, n = 16 of 24). The sensitivity and positive predictive value of serial ECG changes were poor (<30%), with a less areas under the curve (0.55) compared with serial troponins alone (0.83). The addition of serial ECG changes to Thrombolysis In Myocardial Infarction risk scoring showed a decrease in the net reclassification index for major adverse cardiovascular events (-0.04, p <0.1) and was not significant for the prediction of major adverse cardiovascular events and/or acute coronary syndrome in 30 days (-0.003, p = 0.94). In conclusion, routine serial ECG evaluation for patients presenting with undifferentiated chest pain in the ED may not significantly improved diagnostic prognosis beyond current standard evaluation modalities.

Evaluation of ECG algorithms designed to improve detect of transient myocardial ischemia to minimize false alarms in patients with suspected acute coronary syndrome

BACKGROUND

Patients hospitalized for suspected acute coronary syndrome (ACS) are at risk for transient myocardial ischemia. During the "rule-out" phase, continuous ECG ST-segment monitoring can identify transient myocardial ischemia, even when asymptomatic. However, current ST-segment monitoring software is vastly underutilized due to false positive alarms, with resultant alarm fatigue. Current ST algorithms may contribute to alarm fatigue because; (1) they are not designed with a delay (minutes), rather alarm to brief spikes (i.e., turning, heart rate changes), and (2) alarm to changes in a single ECG lead, rather than contiguous leads.

PURPOSE

This study was designed to determine sensitivity, and specificity, of ST algorithms when accounting for; ST magnitude (100μV vs 200μV), duration, and changes in contiguous ECG leads (i.e., aVL, I, - aVR, II, aVF, III; V1, V2, V3, V4, V5, V6, V6, I).

METHODS

This was a secondary analysis from the COMPARE Study, which assessed occurrence rates for transient myocardial ischemia in hospitalized patients with suspected ACS using 12-lead Holter. Transient myocardial ischemia was identified from Holter using >100μV ST-segment ↑ or ↓, in >1 ECG lead, >1min. Algorithms tested against Holter transient myocardial ischemia were done using the University of California San Francisco (UCSF) ECG algorithm and included: (1)100μV vs 200μV any lead during a 5-min ST average; (2)100μV vs 200μV any lead >5min, (3) 100μV vs 200μV any lead during a 5-min ST average in contiguous leads, and (4) 100μV vs 200μV>5min in contiguous leads (Table below).

RESULTS

In 361 patients; mean age 63+12years, 63% male, 56% prior CAD, 43 (11%) had transient myocardial ischemia. Of the 43 patients with transient myocardial ischemia, 17 (40%) had ST-segment elevation events, and 26 (60%) ST-segment depression events. A higher proportion of patients with ST segment depression has missed ischemic events. Table shows sensitivity and specificity for the four algorithms tested.

CONCLUSIONS

Sensitivity was highly variable, due to the ST threshold selected, with the 100μV measurement point being superior to the 200μV amplitude threshold. Of all the algorithms tested, there was moderate sensitivity and specificity (70% and 68%) using the 100μV ST-segment threshold, integrated ST-segment changes in contiguous leads during a 5-min average.

Role of central obesity in risk stratification after an acute coronary event: does central obesity add prognostic value to the Global Registry of Acute Coronary Events (GRACE) risk score in patients with acute coronary syndrome?

BACKGROUND

Accurate risk stratification is an important step in the initial management of acute coronary syndrome (ACS), and current guidelines recommend the use of risk scores, such as the Global Registry of Acute Coronary Events risk score (GRACE RS). Recent studies have suggested that abdominal obesity is associated with cardiovascular events in patients with ACS. However, little is known about the additional value of abdominal obesity beyond risk scores. The aim of our study was thus to assess whether waist circumference, a surrogate of abdominal adiposity, adds prognostic information to the GRACE RS.

METHODS

This was a retrospective cohort study of ACS patients admitted consecutively to a cardiac care unit between June 2009 and July 2010. The composite of all-cause mortality or myocardial reinfarction within six months of index hospitalization was used as the endpoint for the analysis.

RESULTS

A total of 285 patients were studied, 96.1% admitted for myocardial infarction (with or without ST elevation) and 3.9% for unstable angina. At the end of the follow-up period, 10 patients had died and the composite endpoint had been reached in 27 patients (9.5%). More than 70% of the study population were obese or overweight, and abdominal obesity was present in 44.6%. The GRACE RS showed poor predictive accuracy (area under the curve 0.60), and most of the GRACE variables did not reach statistical significance in multivariate analysis. The addition of waist circumference to the GRACE RS did not improve its discriminatory performance.

CONCLUSION

Abdominal obesity does not add prognostic information to the GRACE RS to predict six-month mortality or myocardial reinfarction.

Detecting myocardial ischemia with continuous ST-segment monitoring: two case studies

Continuous ST-segment ischemia monitoring is recommended for patients at significant risk for myocardial ischemia that, if sustained, may result in acute myocardial infarction or extension of a myocardial infarction. It is especially useful for patients who do not perceive or cannot communicate symptoms of ischemia. We report 2 case studies of young women with acute coronary syndrome who benefited from continuous ST-segment monitoring. One patient was critically ill and unresponsive, and one patient had atypical symptoms and some difficulty communicating clearly.

Does continuous ST-segment monitoring add prognostic information to the TIMI, PURSUIT, and GRACE risk scores?

BACKGROUND

Recurrent ischemia is frequent in patients with non-ST-elevation acute coronary syndromes (NST-ACS), and portends a worse prognosis. Continuous ST-segment monitoring (CSTM) reflects the dynamic nature of ischemia and allows the detection of silent episodes. The aim of this study is to investigate whether CSTM adds prognostic information to the risk scores (RS) currently used.

METHODS

We studied 234 patients with NST-ACS in whom CSTM was performed in the first 24 hours after admission. An ST episode was defined as a transient ST-segment deviation in ≥1 lead of ≥ 0.1 mV, and persisting ≥1 minute. Three RS were calculated: Thrombolysis in Myocardial Infarction (TIMI; for NST-ACS), Platelet glycoprotein IIb/IIIa in Unstable angina: Receptor Supression Using Integrilin (PURSUIT; death/MI model), and Global Registry of Acute Coronary Events (GRACE). The end point was defined as death or nonfatal myocardial infarction (MI), during 1-year follow-up.

RESULTS

ST episodes were detected in 54 patients (23.1%) and associated with worse 1-year outcome: 25.9% end point rate versus 12.2% (Odds Ratio [OR]= 2.51; 95% Confidence Interval [CI], 1.18-5, 35; P = 0.026). All three RS predicted 1-year outcome, but the GRACE (c-statistic = 0.755; 95% CI, 0.695-0.809) was superior to both TIMI (c-statistic = 0.632; 95% CI, 0.567-0.694) and PURSUIT (c-statistic = 0.644; 95% CI: 0.579-0.706). A GRACE RS > 124 showed the highest accuracy for predicting end point. The presence of ST episodes added independent prognostic information the TIMI RS (hazard ratio [HR]= 2.23; 95% CI, 1.13-4.38) and to PURSUIT RS (HR = 2.03; 95% CI, 1.03-3.98), but not to the GRACE RS.

CONCLUSIONS

CSTM provides incremental prognostic information beyond the TIMI and PURSUIT RS, but not the GRACE risk score. Hence, the GRACE risk score should be the preferred stratification model in daily practice.

Relation between hemoglobin level and recurrent myocardial ischemia in acute coronary syndromes detected by continuous electrocardiographic monitoring

Anemia has been associated with adverse outcomes in patients with acute coronary syndromes (ACS). However, the underlying pathophysiologic mechanisms have not been well elucidated. We sought to determine the independent relation between the hemoglobin level and recurrent ischemia in patients with non-ST-segment elevation ACS using continuous electrocardiographic monitoring. In the Integrilin and Enoxaparin Randomized Assessment of Acute Coronary Syndrome Treatment (INTERACT) trial, 746 patients presenting with non-ST-segment elevation ACS underwent continuous ST-segment monitoring for 48 hours. The data were analyzed independently at a core laboratory. We stratified the study population according to their hemoglobin level on presentation. The primary outcome of the study was recurrent ischemia, defined as ST-segment shifts on continuous electrocardiographic monitoring. Of the 705 patients with analyzable data, 64 had a baseline hemoglobin level <120 g/L, 259 had a level of 120 to 139 g/L, 315 had a level of 140 to 159 g/L, and 67 had a level >160 g/L. The corresponding rates of recurrent ischemia were 39.1%, 22.0%, 15.6%, and 11.9% (p for trend <0.001). A lower hemoglobin level was associated with advanced age, co-morbidities, and a higher GRACE risk score. In multivariable analysis adjusting for these confounders, lower hemoglobin levels retained a significant independent association with recurrent ischemia (p for trend = 0.004). In conclusion, a lower hemoglobin level at presentation was independently associated with recurrent ischemia detected by continuous electrocardiographic monitoring in the setting of non-ST-segment elevation ACS. This suggests that anemia might predispose patients to recurrent ischemia, which could be an important underlying mediator of worse outcomes in patients with lower hemoglobin levels.

National survey of cardiologists' standard of practice for continuous ST-segment monitoring

BACKGROUND

Continuous ST-segment monitoring can be used to detect early and transient cardiac ischemia. The American Heart Association and American Association of Critical-Care Nurses recommend its use among specific patients, but such monitoring is routine practice in only about half of US hospitals.

OBJECTIVE

To determine cardiologists' awareness and practice standards regarding continuous ST-segment monitoring and the physicians' perceptions of appropriate patient selection, benefits and barriers, and usefulness of this technology.

METHODS

An electronic survey was sent to a random sample of 915 US cardiologists from a pool of 4985 certified cardiologists.

RESULTS

Of 200 responding cardiologists, 55% were unaware of the consensus guidelines. Of hospitals where respondents admitted patients, 49% had a standard of practice for using continuous ST-segment monitoring for cardiac patients. Most cardiologists agreed or strongly agreed that patients in the cardiovascular laboratory (87.5%) and intensive care unit (80.5%) should have such monitoring. Cardiologists routinely ordered ST monitoring for patients with acute coronary syndrome (67%) and after percutaneous coronary intervention (60%). The primary factor associated with higher perceptions for benefits, clinical usefulness, and past use of continuous ST-segment monitoring was whether or not hospitals in which cardiologists practiced had a standard of practice for using this monitoring. A secondary factor was awareness of published consensus guidelines for such monitoring.

CONCLUSION

Respondents (55%) were unaware of published monitoring guidelines. Hospital leaders could raise awareness by multidisciplinary review of evidence and possibly incorporating continuous ST-segment monitoring into hospitals' standards of practice.

Bleeding and outcome in acute coronary syndrome: insights from continuous electrocardiogram monitoring in the Integrilin and Enoxaparin Randomized Assessment of Acute Coronary Syndrome Treatment (INTERACT) Trial

BACKGROUND

Bleeding is associated with adverse outcome in acute coronary syndromes. However, the precise pathophysiologic mechanisms have not been elucidated. We sought to determine the relationship between bleeding and myocardial ischemia detected by concurrent continuous electrocardiogram (ECG) monitoring and their independent long-term prognostic significance.

METHODS

The INTERACT trial was a randomized controlled trial of enoxaparin versus unfractionated heparin in patients with high-risk non-ST-elevation acute coronary syndromes. Continuous ECG monitoring, performed after enrollment up to 96 hours, was analyzed by an automated algorithm and reviewed by a blinded cardiologist. We centrally adjudicated all bleeding and clinical events in a blinded fashion and calculated the Global Registry of Acute Coronary Events risk score (a validated predictor of mortality) for each patient.

RESULTS

Of the 746 patients enrolled, 34 (4.6%) developed major bleeding within 96 hours. After a median follow-up of 2.4 years, patients with bleeding had a higher risk of death (28.4% vs 7.3%, P < .001) and death/myocardial infarction (38.0% vs 12.9%, P < .001) compared with those without bleeding. Overall, 619 patients survived the first 96 hours with complete data on continuous ECG monitoring. Bleeding was associated with the simultaneous presence of ST-segment shifts on continuous ECG monitoring (P = .03). After adjusting for Global Registry of Acute Coronary Events risk score and myocardial ischemia detected by continuous ECG monitoring, major bleeding remained an independent predictor of death (adjusted hazard ratio = 3.48, 95% confidence interval 1.51-8.03, P = .003) and death/myocardial infarction (adjusted hazard ratio = 2.85, 95% confidence interval 1.40-5.78, P = .004).

CONCLUSIONS

Bleeding is a powerful independent predictor of poor long-term outcome, even after adjusting for other associated prognostic factors such as advanced age and renal dysfunction. Although bleeding is associated with concurrent myocardial ischemia, its adverse prognostic impact may be mediated by complex pathophysiologic mechanisms rather than myocardial ischemia alone. Our findings suggest that future investigations should focus on other biologically plausible mechanisms.