Left Bundle-Branch Block in MI Without Chest Pain
Abstract & Commentary
Source: Shlipak MG, et al. Treatment and outcomes of left bundle-branch block patients with myocardial infarction who present without chest pain. J Am Coll Cardiol 2000;36:706-712.
The recognition and treatment of acute myocardial infarction (AMI) in the setting of left bundle-branch block (LBBB) on ECG remains problematic for emergency physicians. Complicating this picture is the fact that LBBB is associated with older age, comorbidity, and underlying cardiac disease—conditions in which patients are at greatest risk for morbidity and mortality from AMI, and stand the greatest chance for maximal benefit from acute therapy.
In this retrospective, observational study, the authors reviewed nearly 30,000 AMI cases presenting with LBBB from the National Registry of Myocardial Infarction-2 database of more than 750,000 AMI cases. Nearly one-half of these patients (47%) presented without chest pain. The investigators compared LBBB/AMI patients with and without chest pain for history, clinical presentation, treatment, and in-hospital mortality.
Overall, AMI/LBBB patients without chest pain were slightly older and more likely to present in heart failure. More than one-half of these patients (59%) initially were admitted with a diagnosis other than an acute coronary syndrome (AMI, rule-out myocardial infarction, or unstable angina) vs. 19% of those with chest pain. In fact, nearly one of every 10 AMI/LBBB patients without chest pain was admitted to a non-monitored floor bed. Correspondingly, AMI/LBBB patients without chest pain were less likely (compared to those with chest pain) to receive acute reperfusion therapy (fibrinolysis or percutaneous coronary intervention, 13.6% vs 2.6%), aspirin (73.1% vs 54.6%), beta-blocking agents (32.5% vs 18.6%), heparin (69.3% vs 48.4%), or intravenous nitroglycerin (58.7% vs 30.7%).
Most importantly, in-hospital mortality was markedly higher for AMI/LBBB patients without chest pain (27% vs 18%). This difference was attributable to both initial presentation severity and the undertreatment of these patients, particularly with respect to aspirin administration. The authors conclude that patients presenting with any acute cardiopulmonary symptoms, with or without chest pain, and LBBB on ECG are at risk for AMI and increased mortality. Greater emphasis on early recognition and aggressive treatment of these patients by physicians is warranted.
Comment by Theodore C. Chan, MD, FACEP
Prior studies have shown that AMI patients who present with atypical symptoms (such as no chest pain) or with ECGs in which ischemia is difficult to detect (such as LBBB), often suffer a delay in diagnosis and treatment.1,2 Thus, it is not surprising that this study of AMI patients with LBBB and no chest pain featured such low rates of correct diagnosis and appropriate treatment.
On a larger scale, this study reflects the very difficult issue of recognizing and treating AMI in the elderly population. With advancing age, AMI patients are more likely to present atypically and with abnormal ECGs—making the diagnosis problematic. As a result, important therapies, such as aspirin, often are withheld, leading to significant morbidity and mortality for these patients, as reported by the authors. This large observational study reflecting contemporary, nationwide practice certainly draws attention to this problem.
It is interesting to note that despite mounting evidence on the importance of early reperfusion, the overall rate of acute reperfusion therapy was only 8.4% for all LBBB patients in this study. This low rate likely reflects the lack of early recognition of AMI in these patients, as well as the ongoing controversy regarding the use of therapies, particularly fibrinolysis, in the elderly.3
A few study limitations should be noted. As a retrospective study, some information is not available. For example, no data are provided regarding which symptoms those without chest pain did feature on presentation. Moreover, no information on the important distinction between new and old LBBB is reported. Nonetheless, given the large numbers of AMI patients reviewed, this study strongly suggests that physicians should be aware of the need for early recognition and aggressive treatment of AMI in these patients.
References
1. Canto JG, et al. Prevalence, clinical characteristics, and mortality among patients with myocardial infarction presenting without chest pain. JAMA 2000;283:3223-3229.
2. Shlipak MG, et al. Should the electrocardiogram be used to guide therapy for patients with left bundle-branch block and suspected myocardial infarction? JAMA 1999;281:714-719.
3. Thiemann DR, et al. Lack of benefit of intravenous thrombolysis in patients with myocardial infarction who are older than 75 years. Circulation 2000;101:2239-2246.
You have reached your article limit for the month. Subscribe now to access this article plus other member-only content.
- Award-winning Medical Content
- Latest Advances & Development in Medicine
- Unbiased Content