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Cardiology

Is It Really Alternating Bundle-Branch Block?

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JAMA Internal Medicine

Published Online: September 6, 2022

Challenges in Clinical Electrocardiography

Article Information and Disclosures

Caiyun Duan, BS¹;

Author Affiliations

¹Second Affiliated Hospital of Anhui Medical University, Hefei, Anhui, People’s Republic of China

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A patient in their 60s was hospitalized with upper right quadrant discomfort for more than 10 days. The patient had a history of gastric cancer. Ultrasonography at a local hospital revealed multiple low-density foci in the liver. The patient had a history of coronary heart disease and had undergone a percutaneous coronary intervention at another hospital 1 year prior; the details were unknown. Laboratory examination showed a carcinoembryonic antigen level of 8.34 ng/mL (to convert to μg/L, multiply by 1.0) and an α-fetoprotein level of 9.97 ng/mL (to convert to μg/L, multiply by 1.0). Myocardial enzyme examination showed no abnormalities. During the course of the disease, the patient had no symptoms, such as chest tightness, chest pain, or syncope. After admission, two 12-lead electrocardiogram (ECG) examinations were performed (Figure). The Figure, A shows complete right bundle-branch block (CRBBB) with left anterior fascicular block (LAFB), though the second ECG (Figure, B) suggests CRBBB with left posterior fascicular block (LPFB).

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The reversal of the LA/LL leads is uncommon and difficult to identify without a comparison ECG, given that aVR will be unchanged and, like in the case of left arm and right arm reversal, not very unusual appearing.¹ Abdollah et al² analyzed the mechanism of the changes in the QRS complex caused by LA/LL lead reversal. These authors pointed out that the positive and negative polarities of the leads changed when the LA/LL leads were reversed. The main changes were that leads I and II were exchanged, leads aVL and aVF were exchanged, and the positive and negative poles of lead III were reversed. In the present case, the key clues that could identify LA/LL lead reversal were the reversed polarity of the P wave in lead III and the stable PR (distinguishing from alternating bundle-branch block), which were found by comparison. Therefore, the diagnosis is hard to make without a comparison ECG. Lead reversals of any combination merit a repeat ECG, because they can mimic or mask major findings.

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Article Information

Corresponding Author: Lan Ma, MS, Second Affiliated Hospital of Anhui Medical University, No. 678 Furong Rd, Hefei, Anhui 230601, People’s Republic of China (mlws4533@sina.com).

Published Online: September 6, 2022. doi:10.1001/jamainternmed.2022.3703

Conflict of Interest Disclosures: None reported.

Additional Information: Li Wang and Caiyun Duan contributed equally as co–first authors.

References

Harrigan RA , Chan TC , Brady WJ . Electrocardiographic electrode misplacement, misconnection, and artifact. J Emerg Med. 2012;43(6):1038-1044. doi:10.1016/j.jemermed.2012.02.024 PubMed Google Scholar Crossref

Abdollah H , Milliken JA . Recognition of electrocardiographic left arm/left leg lead reversal. Am J Cardiol. 1997;80(9):1247-1249. doi:10.1016/S0002-9149(97)00656-5 PubMed Google Scholar Crossref

Glikson M , Nielsen JC , Kronborg MB , et al. 2021 ESC Guidelines on cardiac pacing and cardiac resynchronization therapy. Europace. 2022;24(1):71-164. doi:10.1093/europace/euab232 PubMed Google Scholar Crossref

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Credit Designation Statement: The American Medical Association designates this Journal-based CME activity activity for a maximum of 1.00  AMA PRA Category 1 Credit(s)™. Physicians should claim only the credit commensurate with the extent of their participation in the activity.

Successful completion of this CME activity, which includes participation in the evaluation component, enables the participant to earn up to:

1.00 Medical Knowledge MOC points in the American Board of Internal Medicine's (ABIM) Maintenance of Certification (MOC) program;;
1.00 Self-Assessment points in the American Board of Otolaryngology – Head and Neck Surgery’s (ABOHNS) Continuing Certification program;
1.00 MOC points in the American Board of Pediatrics’ (ABP) Maintenance of Certification (MOC) program;
1.00 Lifelong Learning points in the American Board of Pathology’s (ABPath) Continuing Certification program; and
1.00 CME points in the American Board of Surgery’s (ABS) Continuing Certification program

It is the CME activity provider's responsibility to submit participant completion information to ACCME for the purpose of granting MOC credit.