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【medical-news】在ST段抬高型心肌梗死中的心电图解
Heart 2009;95:267-268
In the setting of ST-elevation myocardial infarction (MI), the electrocardiogram (ECG) is essential in the diagnosis and evaluation of patients. The ECG is used to quickly risk stratify and subsequently implement the best treatment strategy for the individual patient. During this acute phase, the cardiologist or emergency department physician interprets the electrocardiogram focusing not only on the presence of ST elevation but also on the characteristics that provide important prognostic data on survival after MI. Heart rate, atrioventricular conduction, fascicular block, bundle branch block and the degree of ST-segment deviation have all been shown to influence survival after MI.1 For the more experienced physician, this process is facilitated by pattern recognition. However, it has now become clear that much more prognostic information, such as the likelihood of 30-day mortality, can be better explored with quantitative techniques. This was first realised by Schroder and colleagues, who performed very elegant studies in the 1990s, which demonstrated that the sum of the degree of ST elevation was prognostic of outcomes.2 More importantly, they also found that the proportion of ST segment resolution was also associated with of the degree of reperfusion and therefore prognosis as early as 90 min after receiving fibrinolytic therapy. These findings were later confirmed in larger clinical trials.3 This approach of measuring the sum and degree and resolution of ST segments is now common practice, and thus has opened the door for more careful measurements of the ECG.
More recently, cardiologists have raised the question of whether QRS duration is a robust risk stratifier in diverse cardiovascular disease populations, including patients with heart failure, with dyssynchrony and at increased risk of sudden cardiac death.4 5 The majority of this information has been derived from exploration of QRS duration in setting of more chronic forms of heart disease, and relatively little attention has been paid to acute changes in the QRS duration in ST-elevation MI, with the exception of those that we can detect easily by "pattern recognition," such as left and right bundle branck block (LBBB, RBB or those with fascicular block (left anterior or posterior hemiblock; LAFB, LPF.
In this issue of Heart, Wong et al6 describe the relationship between QRS duration and 30-day mortality after MI in a careful and thoughtful study (see page 276). In a prespecified post hoc analysis of the Hirulog and Early Reperfusion or Occlusion (HERO)-2 trial, the investigators examined QRS duration at baseline and 60 min after fibrinolysis in over 12 000 patients. Only patients with normal conduction (QRS duration <125 ms) or RBBB at both time points were included in the analysis. Patients who developed abnormal QRS delay or those with LBBB were excluded. Finally, the study attempted to determine if the relationship between QRS delay and prognosis differed according to the location of the MI (anterior or inferior).
The authors’ most significant finding was that baseline QRS duration (as measured by calipers) was independently associated with increased 30-day mortality in those patients with anterior MI (even when unaccompanied by RBB, but not in those patients with inferior MI. Among patients with anterior MI, for every 20 ms increment in the QRS duration, there was a 30–40% increase in the risk of death at 30 days, even after adjustment for clinical factors, ST elevation and the presence of Q-waves.
Despite conflicting evidence in the past, it is now becoming clear that QRS prolongation is associated with worse outcomes and increased mortality in multiple cardiovascular disease states. In the Multicenter Automatic Defibrillator Implantation Trial II (MADIT II), patients with ischaemic cardiomyopathy (LVEF 30%) and a QRS duration 140 ms were found to have a twofold increased risk of sudden cardiac death.7 Additionally, in the Efficacy of Vasopressin Antagonism in Heart Failure Outcome Study with Tolvaptan (EVEREST) trial, which enrolled patients with acute decompensated heart failure and an LVEF of 40% or less, patients with a QRS duration 120 ms were found to have a 25% increased risk of all-cause death.5
Among patients with acute MI, prior studies have shown that QRS prolongation is associated with an increased risk of death. In the Valsartan in Acute Myocardial Infarction (VALIANT) trial, patients with QRS prolongation were found to have increased ventricular volumes, decreased systolic function, and a higher incidence of heart failure, cardiovascular death and sudden death.8 As observed in HERO-2, this increased risk was present even in patients with QRS prolongation in the normal range. In the large 30 000 patient (all with ST elevation) Global Utilization of Streptokinase and t-PA for Occluded Coronary Arteries (GUSTO-1) population, QRS duration (100 vs 80 msec) was associated with increased 30-day mortality. Similar to Wong et al in GUSTO-1 the risk associated with QRS prolongation was greatest in those patients with anterior MI (OR 1.55; 95% CI 1.43 to 1.68). The association between QRS prolongation and increased mortality was very strong, providing greater prognostic information than the sum ST segment deviation (as reflected by a much higher statistical association).9
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作者:admin@医学,生命科学 2011-02-24 05:11
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