Chapter 12: Surface Electrocardiography
Which of the following technical errors may result in an electrocardiogram with farfield signals in lead II?
A. Interchanging of the right arm and right leg leads
B. Interchanging of the right arm and left arm leads
C. Interchanging of the left arm and left leg leads
D. Interchanging of the right arm and left leg leads
E. Interchanging of the right leg and left leg leads
The answer is A. (Hurst’s The Heart, 14th Edition, Chap. 12) Interchanging of the right arm and right leg leads would result in farfield signals (diminished signals) in lead II. Interchanging of the right arm and left arm leads would result in a pattern of negative P, negative QRS, and negative T waves in lead I (and positive in aVR) (option B). A normal pattern of R wave progression from V1 to V6 would argue against dextrocardia in this instance if the leads were placed correctly. Interchanging left arm and left leg leads would result in reversal of leads aVL and aVF, reversal of leads I and II, and inversion of lead III (option C). Interchanging right arm and left leg leads would result in inversion of leads I, II, and III, and reversal of leads aVR and aVF (option D). Interchanging of the right and left leg leads will not result in a different ECG recording compared to one obtained with standard electrode placement (option E).
Which of the following is strongly suggestive of an atypical right bundle branch block (RBBB) on electrocardiogram?
A. QRS of at least 0.12 seconds with midfinal slurring
C. qRS in V6 with S wave slurring and a positive T wave
D. T wave with an opposite polarity to the QRS slurring
E. QR in aVR with R wave slurring and a negative T wave
The answer is B. (Hurst’s The Heart, 14th Edition, Chap. 12) The first upward deflection (R) of the QRS should always be shorter than the second upward deflection (rʹ) in a typical RBBB. Options A, C, D, and E represent diagnostic criteria for a typical RBBB.
A 42-year-old woman presents to the emergency department with a 12-hour history of worsening dyspnea and weakness. She describes a recent business trip to India. Which of the following represent the least likely electrocardiographic sign to ...