ECG ECG Troubleshooting 4

Question 1

An ECG technician observes a 60-cycle (60 Hz) interference pattern on the tracing. Which corrective measure is most appropriate?

Accepted Answer

Check electrode contact and ensure leads are not crossing electrical equipment

Answer

60 Hz AC interference is caused by poor electrode contact or proximity to electrical equipment; improving electrode contact and repositioning cables eliminates this artifact.

Question 2

A patient's ECG shows PR interval of 320 ms that is constant across all beats. How is this classified?

Accepted Answer

First-degree AV block

Answer

First-degree AV block is defined as a PR interval greater than 200 ms that remains constant with every beat conducted through the AV node.

Question 3

On an ECG, the QT interval measures 480 ms at a heart rate of 60 bpm. What is the corrected QT (QTc) and its significance?

Accepted Answer

QTc = 480 ms; prolonged, risk of Torsades de Pointes

Answer

At 60 bpm (RR = 1.0 sec), QTc by Bazett's formula equals QT/√RR = 480/1.0 = 480 ms, which is prolonged and associated with risk of Torsades de Pointes.

Question 4

A patient with known COPD has an ECG showing right axis deviation, P pulmonale, and dominant R wave in V1. What is the most likely interpretation?

Accepted Answer

Right ventricular hypertrophy secondary to cor pulmonale

Answer

Chronic COPD causes pulmonary hypertension leading to right ventricular hypertrophy, which produces right axis deviation, tall P waves (P pulmonale), and a dominant R in V1.

Question 5

Which ECG feature distinguishes Mobitz II second-degree AV block from Mobitz I (Wenckebach)?

Accepted Answer

Mobitz II has a fixed PR interval before the dropped beat; Mobitz I has a progressively lengthening PR

Answer

Mobitz II features a constant PR interval with sudden non-conducted P waves, whereas Mobitz I shows progressive PR prolongation before a dropped beat.

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ECG ECG Troubleshooting 4