PCT EKG Lead Placement & Rhythm Recognition 2 — Questions and Answers
Question 1: In a standard 12-lead EKG, where is the V1 electrode placed?
- Left side, 4th intercostal space at the sternal border
- Right side, 4th intercostal space at the sternal border (Correct answer)
- Left side, 5th intercostal space at the midclavicular line
- Right side, 2nd intercostal space
Correct answer: Right side, 4th intercostal space at the sternal border
V1 is placed at the 4th intercostal space at the right sternal border, serving as the first precordial lead.
The six precordial (chest) leads V1-V6 wrap around the left chest. V1 begins at the right sternal border, 4th intercostal space. V2 mirrors it on the left sternal border. V3 is between V2 and V4. V4 is at the 5th intercostal space, midclavicular line. V5 and V6 continue laterally at the same horizontal level as V4.
Question 2: What does a prolonged PR interval on an EKG tracing indicate?
- Ventricular hypertrophy
- A first-degree AV block (Correct answer)
- Atrial fibrillation
- Bundle branch block
Correct answer: A first-degree AV block
A PR interval longer than 0.20 seconds indicates delayed conduction through the AV node, which defines a first-degree AV block.
The normal PR interval is 0.12-0.20 seconds. When it exceeds 0.20 seconds consistently, conduction through the AV node is delayed but all impulses still reach the ventricles. This is first-degree AV block—usually benign but should be documented and monitored for progression to higher-degree blocks.
Question 3: Which EKG rhythm shows irregularly irregular R-R intervals with no identifiable P waves?
- Sinus arrhythmia
- Atrial flutter
- Atrial fibrillation (Correct answer)
- Second-degree AV block
Correct answer: Atrial fibrillation
Atrial fibrillation is characterized by chaotic atrial activity producing no distinct P waves and completely irregular ventricular response.
In atrial fibrillation, multiple atrial foci fire chaotically at 350-600 times per minute, producing a wavy, irregular baseline instead of P waves. The AV node conducts impulses irregularly, resulting in an irregularly irregular ventricular rate. This is the most common sustained cardiac arrhythmia.
Question 4: What is the correct color code for the right arm (RA) limb lead electrode?
- Green
- Black
- Red
- White (Correct answer)
Correct answer: White
In the standard American color code, white is placed on the right arm (remember: 'white is right').
The American EKG limb lead color code: White = Right Arm, Black = Left Arm, Green = Right Leg, Red = Left Leg. A common mnemonic is 'White to Right, Smoke (black) over Fire (red)' with green on the remaining leg. Correct placement is essential for accurate tracings.
Question 5: A patient's EKG shows a heart rate of 42 bpm with a regular rhythm and wide QRS complexes. This is MOST consistent with:
- Normal sinus rhythm
- Junctional rhythm
- Ventricular escape rhythm (Correct answer)
- Sinus tachycardia
Correct answer: Ventricular escape rhythm
A rate of 20-40 bpm with wide QRS complexes indicates the ventricular pacemaker cells have taken over, producing a ventricular escape rhythm.
When the SA and AV nodes fail to generate or conduct impulses, ventricular pacemaker cells fire at their intrinsic rate of 20-40 bpm. The QRS is wide (>0.12 sec) because conduction spreads slowly through ventricular muscle rather than the fast His-Purkinje system. This is a life-threatening rhythm requiring immediate notification.
Question 6: Artifact on an EKG tracing can be caused by all of the following EXCEPT:
- Patient movement
- Dried electrode gel
- Proper skin preparation (Correct answer)
- Electrical interference from nearby equipment
Correct answer: Proper skin preparation
Proper skin preparation (cleaning and light abrasion) reduces artifact by improving electrode contact, while all other options introduce artifact.
EKG artifact sources include patient movement (muscle tremor), dried or insufficient electrode gel (poor conductivity), electrical interference from other devices, loose lead connections, and inadequate skin preparation. Proper skin prep—cleaning with alcohol, removing excess hair, and lightly abrading the skin—ensures good electrode contact and clear tracings.
PCT EKG Lead Placement & Rhythm Recognition 2
In a standard 12-lead EKG, where is the V1 electrode placed?