ECG Troubleshooting Flashcards

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

Answer: Check electrode contact and ensure leads are not crossing electrical equipment

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

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

Answer: First-degree AV block

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.

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?

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

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.

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?

Answer: Right ventricular hypertrophy secondary to cor pulmonale

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.

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

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

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

During ECG acquisition, the technician notices the calibration pulse measures 5 mm instead of the standard 10 mm. What does this indicate?

Answer: The gain is set to half standard (5 mm/mV)

Standard ECG calibration is 10 mm/mV; a 5 mm calibration pulse means the gain is halved (5 mm/mV), which will make all waveforms appear half their true amplitude.

A patient's ECG shows ST elevation in leads II, III, and aVF with reciprocal ST depression in I and aVL. Which coronary artery is most likely occluded?

Answer: Right coronary artery

The inferior leads (II, III, aVF) are supplied primarily by the right coronary artery (RCA) in most patients, so inferior STEMI usually reflects RCA occlusion.