Clinical Investigation
Acute Ischemic Heart Disease
Unraveling the spectrum of left bundle branch block in acute myocardial infarction: Insights from the Assessment of the Safety and Efficacy of a New Thrombolytic (ASSENT 2 and 3) trials

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Background

Left bundle branch block (LBBB) complicates the diagnosis of acute myocardial infarction (AMI). The Sgarbossa criteria were developed from GUSTO I to surmount this diagnostic challenge but have not been prospectively validated in a large population with presumed AMI. We evaluated their utility in the diagnosis and risk stratification of AMI patients in ASSENT 2 & 3.

Methods

Baseline electrocardiograms (ECG) of LBBB patients were scored using Sgarbossa's criteria (0-10) by 2 readers blinded to the CK/CK-MB data and clinical outcomes; 267 (1.2%) patients had LBBB on their baseline ECG.

Results

Among 253 LBBB patients with available peak CK/CK-MB data, 158 (62.5%) had peak CK/CK-MB levels >2× ULN, thereby qualifying for the diagnosis of AMI. A Sgarbossa score of 3 was shown in 48.7% of LBBB patients with elevated CK/CK-MB versus in 12.6% of those without a CK/CK-MB rise (P < .001). Patients with higher Sgarbossa scores, ie, 3, had a higher mortality compared with those with a score <3, (23.5% vs 7.7% at 30 days P < .001; and 33.7% vs 20.2% at 1 year, P < .001, respectively).

Conclusions

Our findings validate the utility of Sgarbossa criteria for diagnosing AMI in the setting of LBBB. These criteria provide a simple and practical diagnostic approach to risk stratify this diagnostically challenging high-risk group and optimize risk-benefit of acute therapy.

Section snippets

Study population

This study consisted of patients with LBBB derived from the ASSENT 2 and 3 trials. The patient population enrolled in both trials is described elsewhere.8, 9 Briefly, the ASSENT 2 study enrolled 16 949 patients with symptoms of AMI of less than 6 hours' duration associated with ST segment elevation of ≥1 mm in 2 or more limb leads, or ≥2 mm in 2 or more contiguous precordial leads, or presumed new LBBB. Patients received either a rapid infusion of alteplase or a single-bolus injection of

Results

Of the overall sample of 22 839 patients, 267 (1.2%) had LBBB on their baseline ECG: 176 (1.0%) in ASSENT 2 and 91 (1.5%) in ASSENT 3. The baseline characteristics and outcomes for patients with and without LBBB are presented in Table II. Patients with LBBB were 10 years older, more likely to be female, hypertensive, diabetic, and have prior myocardial infarction and coronary artery bypass surgery. In contrast, patients without LBBB were more likely to be current smokers and have a less advanced

Discussion

This study of 267 patients with LBBB and suspected AMI is the largest and most comprehensive cohort validating the criteria for the identification of AMI proposed by Sgarbossa et al.4 We found in these 2 large fibrinolytic trials, comprising more than 22 000 patients, that a Sgarbossa score of 3 or higher (presence of either concordant ST elevation or depression) was highly specific in diagnosing AMI in the presence of LBBB. Not only did a higher Sgarbossa score (ie, ≥3) correlate with a more

Conclusions

Our findings validate the utility of Sgarbossa criteria for diagnosing AMI in the setting of LBBB. Sgarbossa criteria provide a simple and practical diagnostic approach to identify AMI and contribute usefully to risk stratification and optimize the risk-benefit of acute therapy in this diagnostically challenging group and high-risk population.

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