Division of Cardiology, Department of Internal Medicine, Virginia Commonwealth University, Richmond, USA.
Am Heart J. 2011 Apr;161(4):698-704. doi: 10.1016/j.ahj.2011.01.008.
Guidelines derived from patients in clinical trials indicate that emergency department patients with likely myocardial infarction (MI) who have new left bundle-branch block (LBBB) should undergo rapid reperfusion therapy. Whether this pertains to lower risk emergency department patients with LBBB is unclear.
A total of 401 consecutive patients with LBBB undergoing an MI rule-out protocol were included. Left bundle-branch blocks were classified as chronic; new; or, if no prior electrocardiogram (ECG) was available, as presumably new. Left bundle-branch blocks were considered concordant if there was ≥1 mm concordant ST elevation or depression. Rates of MI, peak MB values in MI patients, and 30-day mortality were compared across groups.
A majority of patients (64%) had new (37%) or presumably new LBBB (27%). A total of 116 patients (29%) had MI, with no significant difference in prevalence or size of MI among the 3 ECG groups. Myocardial infarction was diagnosed in 86% of patients with concordant ECG changes versus 27% of patients without concordant ECG changes (P < .01). Peak MB was >5× normal in 50% who had concordant ST changes compared to none of those who did not. Concordant ST changes were the most important predictor of MI (odds ratio 17, 95% CI 3.4-81, P < .001) and an independent predictor of mortality (odds ratio 4.3, 95% CI 1.3-15, P < .001); new or presumably new LBBB was neither.
Most patients with possible MI with new or presumably new LBBB do not have MI. Concordant ECG changes were an important predictor of MI and death. Current guidelines regarding early reperfusion therapy for patients with LBBB should be reconsidered.
临床试验中的患者指南表明，新发左束支传导阻滞（LBBB）的疑似心肌梗死（MI）急诊科患者应接受快速再灌注治疗。但对于新发 LBBB 的低风险急诊科患者是否适用还不清楚。
共纳入 401 例接受 MI 排除方案的连续 LBBB 患者。左束支传导阻滞分为慢性；新发；或如果没有之前的心电图（ECG），则假定为新发。如果有≥1mm 的 ST 段抬高或压低，则认为左束支传导阻滞为一致性改变。比较各组的 MI 发生率、MI 患者的峰值 MB 值和 30 天死亡率。
大多数患者（64%）为新发（37%）或推测新发 LBBB（27%）。共有 116 例患者（29%）患有 MI，3 组 ECG 中 MI 的发生率和大小无显著差异。有一致性 ECG 改变的患者中，有 86%诊断为 MI，而没有一致性 ECG 改变的患者中，有 27%诊断为 MI（P <.01）。与无一致性 ST 改变的患者相比，有一致性 ST 改变的患者中，MB 峰值超过正常 5 倍的比例为 50%（无一致性 ST 改变的患者中为 0%）（P <.01）。一致性 ST 改变是 MI 的最重要预测因素（比值比 17，95%置信区间 3.4-81，P <.001），也是死亡率的独立预测因素（比值比 4.3，95%置信区间 1.3-15，P <.001）；新发或推测新发 LBBB 均不是。
大多数新发或推测新发 LBBB 的疑似 MI 患者并无 MI。一致性 ECG 改变是 MI 和死亡的重要预测因素。应重新考虑当前针对 LBBB 患者早期再灌注治疗的指南。
