Key result
Presumed-new LBBB without ST changes is linked to ~48% lower 30-day mortality post-fibrinolysis versus normal conduction.
Why the study?
Patients with presumed-new LBBB receiving fibrinolytic therapy are often considered high-risk, but their clinical outcomes are not well-defined.
Does the presence of ST-segment changes predict 30-day mortality and AMI in patients with presumed-new LBBB receiving fibrinolytic therapy?
Observational (n=15,640)
Yes
Does the presence of ST-segment changes predict 30-day mortality and AMI in patients with presumed-new LBBB receiving fibrinolytic therapy?
Odds Ratio: 0.52 (95% CI 0.33–0.8)
Absolute Event Rate: 13.5% vs 21.6%
p-value: p=0.022
In patients with presumed-new LBBB receiving fibrinolytic therapy, the absence of ST-segment changes identifies a lower-risk subgroup with reduced 30-day mortality compared to those with normal conduction.
ST changes may refine risk stratification in LBBB; leaves open whether ECG criteria should guide reperfusion decisions.
OBJECTIVES: The purpose of this research was to examine the prognostic value of ST-segment changes (concordant ST-segment elevation and/or precordial V1 to V3 ST-segment depression) during presumed-new left bundle branch block (LBBB) in patients receiving fibrinolytic therapy. BACKGROUND: These patients are often considered high-risk, but their outcome is not well-defined. METHODS: The Hirulog and Early Reperfusion or Occlusion (HERO)-2 trial compared bivalirudin with heparin in patients receiving streptokinase for ST-segment elevation or presumed-new LBBB. Each patient with LBBB was matched with a control (with normal intraventricular conduction) for age, gender, pulse rate, systolic blood pressure, Killip class, and region. RESULTS: A total of 300 patients had LBBB (92 with and 208 without ST-segment changes) and 15,340 had normal conduction. Acute myocardial infarction (AMI) occurred in 80.7% of LBBB patients and 88.7% of controls (p = 0.006). ST-segment changes were specific (96.6%) but not sensitive (37.8%) for enzymatic diagnosis of AMI. Mortality at 30 days was similar in LBBB patients with ST-segment changes (21.7%) and controls (25.0%, p = 0.563), but lower in LBBB patients without ST-segment changes than in controls (13.5% vs. 21.6%, p = 0.022). In the whole HERO-2 cohort, the LBBB patients with ST-segment changes had higher mortality than patients with normal conduction (odds ratio [OR] 1.37, 95% confidence interval [CI] 0.78 to 2.42). The LBBB patients without ST-segment changes had lower mortality than patients with normal conduction (OR 0.52, 95% CI 0.33 to 0.80). CONCLUSIONS: ST-segment changes during LBBB are specific for the diagnosis of AMI and predict 30-day mortality; LBBB patients without ST-segment changes have lower adjusted 30-day mortality than those with normal conduction. Trials are required to determine the best treatment for high-risk and low-risk patients with LBBB.
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Wong et al. (2005) conducted an observational in Prolonged ischemic chest pain and presumed-new left bundle branch block (n=15,640). Presumed-new left bundle branch block without ST-segment changes vs. Normal intraventricular conduction was evaluated on 30-day mortality (OR 0.52, 95% CI 0.33-0.80, p=0.022). In patients receiving fibrinolytic therapy, presumed-new LBBB without ST-segment changes was associated with lower 30-day mortality compared to normal conduction (OR 0.52; 95% CI 0.33-0.80).
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