European Heart Journal Advance Access originally published online on December 7, 2005
European Heart Journal 2006 27(3):249-250; doi:10.1093/eurheartj/ehi680
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Do we need continuous ECG monitoring in patients transferred for primary angioplasty?
1Department of Internal Medicine, University of Arkansas for Medical Sciences and the Central Arkansas Veterans Healthcare System, Little Rock, AR, USA
2Department of Physiology and Biophysics, Division of Cardiovascular Medicine, University of Arkansas for Medical Sciences and the Central Arkansas Veterans Healthcare System, 4301 West Markham Street, Mail Slot 532, Little Rock, AR 72205-7199, USA
* Corresponding author. Tel: +1 501 296 1401; fax: +1 501 686 6180. E-mail address: mehtajl{at}uams.edu
This editorial refers to ‘Potential significance of spontaneous and interventional ST-changes in patients transferred for primary percutaneous coronary intervention: observations from the ST-MONitoring in Acute Myocardial Infarction study (The MONAMI study)’
by C.J. Terkelsen et al., on page 267
The primary goal in patients with acute ST-elevation myocardial infarction (STEMI) is prompt restoration of blood flow. The current guidelines for the treatment of patients with STEMI include primary angioplasty with the goal of medical contact-to-balloon or door-to-balloon time of 90 min or less.1 This is based on the findings of a reduction in mortality in inverse relationship with the time to reperfusion.2 However, early revascularization does not guarantee optimal myocardial perfusion in patients undergoing primary angioplasty. In some patients, myocardial perfusion remains impaired despite the restoration of TIMI 3 flow, as demonstrated angiographically by TIMI frame count3 and myocardial perfusion blush.4 These patients have adverse outcome. In contrast, reversal of ST-segment on the ECG reflects the effectiveness of myocardial reperfusion. Following successful primary angioplasty, the ST-segment completely resolves at 1 h in 
50% of the patients. These patients have limited myocardial damage and an excellent prognosis during follow-up. The other 50% of the patients have partial or no resolution of the ST-segment and experience greater myocardial damage and higher mortality.5 As an extension of this observation, we may suspect that patients in whom the ST-segment increases after angioplasty may have a worse prognosis than those in whom the ST-segment improves after angioplasty. However, this group of patients has not been well categorized before Terkelsen et al.6 examine the significance of spontaneous and interventional ST-changes in patients transferred for primary angioplasty, as measured by continuous ECG. For this purpose, the investigators performed continuous ECG monitoring starting 90 min before primary angioplasty until 90 min after the completion of the procedure. On the basis of ST-segment changes on ECG, the patients were divided into three groups: those in whom the ST-segment spontaneously resolved before the angioplasty (group A), those with ST-elevation still present before the angioplasty and without increase in the ST-elevation during the angioplasty (group B), and patients with ST-elevation present before the angioplasty and with increase in the ST-elevation during the angioplasty (group C). A limitation of the study is that pre- and intra-procedure information was not provided; pre-procedure therapy, in particular, may have had an impact on the patients' risk and prognosis. The accumulated experience in acute coronary syndromes indicates that early and appropriate therapy is associated with better outcome. Thus, an ideal classification should have been based on pre-catheterization data. However, the present study provides important data despite this shortcoming.
At baseline, there was no difference in the rate of anterior infarct or any other measured variable between the groups, except that the cumulative ST-elevation was higher in group C (2 mm), compared with group A (1 mm) and group B (1.4 mm). The most important finding of the study is the difference in the extent of myocardial damage, measured by in-hospital chemical biomarkers and echocardiograms performed in-hospital and at 3 months, between the three groups. The extent of myocardial damage was greatest in group C, followed by that in group B and least in group A. Unfortunately, the left ventricular ejection fraction (LVEF) was not measured at baseline, but we have no reason to suspect any differences between the groups, as the incidence of previous myocardial infarction was low and similar in the three groups. Group C, the group with the worst outcome, was also the group that presented with the highest level of cumulative ST-elevation on the ECG pre-angioplasty. This finding could potentially be used as an early marker of risk in a given patient and a reason to institute more aggressive therapy.
Another important finding of the study is the difference between groups B and C in achieving 
70% ST-resolution at 30 min, but not at 60 or 90 min, after the first balloon inflation. This indicates the necessity for the analysis of ST-resolution at 30 min after primary angioplasty. Traditionally, ECGs are analysed for ST-resolution at 90 min when using thrombolytic therapy, because these drugs take 45–60 min to work. In primary angioplasty, 30 min may be equivalent to the 90 min after thrombolytic therapy. Therefore, ECG at 30 min for the determination of ST-resolution should be the standard in future trials of primary angioplasty in patients with acute STEMI.
Of importance, 41% of the patients who experienced ST-segment resolution prior to revascularization had not achieved adequate coronary reperfusion as measured by TIMI flow at the time of first contrast injection of the infarct-related artery. Therefore, unintentionally, this study shows the importance of aggressively treating all patients presenting with chest pain and ST-elevation on ECG whether the ST-elevation resolves prior to revascularization or not. The reason for the discrepancy between ST-resolution in the presence of a sub-optimally or non-reperfused artery is not known, but may be partially due to the presence of collateral circulation, which has been shown to have a protective effect on enzymatic infarct size, myocardial blush, and haemodynamic conditions in these patients.7
A benefit associated with pre-hospital ECG analysis is a potential reduction in time to reperfusion, because the catheterization laboratory could be activated before arrival of the ambulance to the hospital and the patient could be directly transferred to the catheterization laboratory without the delay associated with the admission through the emergency room.8 In addition, paramedics could be assisted remotely by emergency department physicians or cardiologists in the optimization of early medical therapy and the management of complications, such as arrhythmias. Furthermore, high-risk patients could be directly transferred to hospitals with capacity for primary angioplasty, instead of transferring these patients to hospitals without it. This time delay involved in patients being transported to hospitals not equipped for primary angioplasty followed by a transfer to a hospital equipped for primary angioplasty is associated to increased mortality.9 Efforts to implement the pre-hospital ECG interpretation to patient care more widely may be of paramount importance.
The potential advantage of identifying patients with persistent or worsening ST-elevation on ECG early post-angioplasty may be of paramount importance, as demonstrated by Terkelsen et al.,6 because those patients will end up having more extensive myocardial necrosis, with subsequent worse prognosis and a lower LVEF. Therefore, this sub-group of patients is a candidate for more intensive medical therapy, including anti-thrombotic and anti-ischaemic agents. At the very least, these patients should be observed in the coronary care unit for longer periods of time, and given their higher risk, should not be candidates for early discharge.10
The traditional 90 min ST-resolution parameter derived from snapshot ECG has a very limited value in the era of primary angioplasty. On the basis of this study, continuous ECG should be obtained as early as possible, and ECG monitoring continued throughout the procedure. Further, an assessment of ST-resolution should be done at 30 min after the first balloon inflation.
Conflict of interest: none declared.
Footnotes
The opinions expressed in this article are not necessarily those of the Editors of the European Heart Journal or of the European Society of Cardiology.
doi:10.1093/eurheartj/ehi606 
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Related articles in EHJ:
- Potential significance of spontaneous and interventional ST-changes in patients transferred for primary percutaneous coronary intervention: observations from the ST-MONitoring in Acute Myocardial Infarction study (The MONAMI study)
- Christian Juhl Terkelsen, Bjarne Linde Nørgaard, Jens Flensted Lassen, Steen Hvitfeldt Poulsen, Jens Christian Gerdes, Erik Sloth, Liv Bjørn-Hansen Gøtzsche, Frode Kirketerp Rømer, Leif Thuesen, Torsten Toftegaard Nielsen, and Henning Rud Andersen
EHJ 2006 27: 267-275.[Abstract] [FREE Full Text]
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