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Right bundle branch block as a cause of false-negative ECG classification of inferior myocardial infarction
I Gussak1, S H Zhou, P Rautaharju
1Division of Cardiology, Saint Louis University Health Science Center, Missouri 63117, USA.
Insights
Right bundle branch block (RBBB) can alter electrocardiogram (ECG) Q wave duration, potentially leading to false-negative myocardial infarction (MI) diagnoses. This finding is crucial for accurate MI classification in clinical trials.
Area of Science:
- Cardiology
- Electrocardiography
- Medical Diagnostics
Background:
- Right bundle branch block (RBBB) is generally not considered to interfere with electrocardiogram (ECG) diagnosis of myocardial infarction (MI).
- The assumption is that RBBB does not significantly alter initial excitation wavefronts detected by ECG.
- Myocardial revascularization procedures carry a risk of developing RBBB post-operatively.
Purpose of the Study:
- To investigate the effect of newly developed RBBB on serial ECG Q wave duration in patients post-myocardial revascularization.
- To determine if RBBB influences the ECG diagnosis of inferior myocardial infarction (MI).
Main Methods:
- Compared serial ECG Q wave duration changes in inferior leads (II, III, aVF).
- Studied 9 patients who developed RBBB post-revascularization (RBBB group) versus 41 controls without RBBB.
- Analyzed ECGs obtained before and after revascularization procedures.
Main Results:
- Q wave durations were similar between groups pre-procedure.
- Significant Q wave duration shortening observed in the RBBB group compared to the control group.
- Most pronounced shortening in lead aVF (-18.2 ms vs -3.8 ms, P < .0001), indicating altered spatial orientation of excitation wavefronts.
Conclusions:
- Incident RBBB following revascularization can significantly alter ECG findings.
- This alteration poses a risk for false-negative ECG diagnosis of inferior MI.
- Serial ECG analysis in clinical trials needs to account for RBBB-induced changes for accurate MI classification.
Abstract:
It is generally accepted in clinical electrocardiography that a right bundle branch block (RBBB) does not interfere with the electrocardiographic (ECG) diagnosis of myocardial infarction (MI). The basic assumption is that the initial excitation wavefronts are relatively unchanged in RBBB. This study compared serial changes in Q wave duration in inferior leads II, III, and aVF in 9 patients who developed RBBB within 3 weeks after myocardial revascularization procedure (RBBB group) and in 41 revascularized patients without RBBB in the same observation period (control group). Q wave durations in the electrocardiograms obtained before the patients' procedures were not significantly different between the study and control groups. However, Q wave durations shortened significantly more in the RBBB group than in the control group. The most pronounced Q wave duration shortening took place in lead aVF, -18.2 ms in the RBBB group versus -3.8 ms in the control group (P = .0001). The shortening was less pronounced, although significant, in leads II and III: II, -7.6 +/- -10.9 ms in the RBBB group vs -2.3 +/- -3.5 ms in the control group (P = .01); III, -11.3 +/- -10.5 ms vs -2.6 +/- -6.5 ms (P = .002); aVF, -18.2 +/- -13.5 ms vs -3.8 +/- -5.3 ms (P < .0001). It is concluded that incident RBBB complicating revascularization procedures may cause significant alterations in spatial orientation of the initial excitation wavefronts. This may be a potential source of false-negative ECG diagnosis of inferior MI, particularly in clinical trials where serial ECG analysis is an important part in MI classification.