Study guide · concept · EKG & cardiovascular testing
12-lead EKG placement for the CCMA
V1 and V2 sit in the 4th intercostal space on either side of the sternum, and V4 sits in the 5th space at the left midclavicular line. V3 goes halfway between V2 and V4, and V5 and V6 go level with V4.
- anchor electrodes
- 3
- limb colors
- 4
- EKG items of 150 scored
- 6
§01
The chest map
Count down from the sternal angle. Don't place V1 by eye.
EKG and cardiovascular testing is a small area, 6 of the 150 scored items, and placement accounts for a large share of it. You only need to memorize three chest positions. V3, V5 and V6 are all placed relative to V2 and V4.
§02
Every electrode, one landmark
The third column is the method. Use it on every patient.
| Electrode | Where it goes | How to find it |
|---|---|---|
| V1 | 4th ICS, right sternal border | Count down from the sternal angle |
| V2 | 4th ICS, left sternal border | Directly across the sternum from V1 |
| V3 | Midway between V2 and V4 | Place it after V4 |
| V4 | 5th ICS, left midclavicular line | One space below V2, then out to the midclavicular line |
| V5 | Left anterior axillary line, level with V4 | Slide straight across from V4 |
| V6 | Left midaxillary line, level with V4 | Keep sliding on the same horizontal line |
| RA | Right arm, white | Limb, away from the torso |
| LA | Left arm, black | Limb, away from the torso |
| RL | Right leg, green (ground) | Limb, away from the torso |
| LL | Left leg, red | Limb, away from the torso |
§03
Placement order that prevents errors
Anchors first, then the fill-ins.
Find the sternal angle
The ridge where the manubrium meets the body of the sternum sits at the 2nd rib. The 2nd intercostal space is just below it. Count down from there to the 4th.
Place V1 and V2
In the 4th intercostal space, one on each side of the sternum.
Place V4
Drop one more space to the 5th, then move out to the left midclavicular line.
Place V3
Halfway along a straight line between V2 and V4.
Place V5 and V6
At the anterior and midaxillary lines, on the same horizontal level as V4. The ribs curve upward toward the side, but the electrodes stay level.
Attach the limb leads
One on each arm and each leg, by color.
§04
Before you press record
Standard settings keep tracings comparable.
- Patient supine and relaxed. If they can't lie flat, note the position on the tracing.
- Machine at the standard 25 mm/s paper speed and 10 mm/mV gain.
- V1, V2 and V4 counted from the sternal angle.
- V5 and V6 checked against V4's level before the first strip prints.
§05
Two placement details
Do the chest electrodes go on top of breast tissue?
No. Place them at the same rib and line landmarks underneath the breast tissue, so each electrode sits on its landmark.
Why count from the sternal angle instead of the collarbone?
The first rib is tucked under the clavicle and hard to feel. The sternal angle is easy to find and always marks the 2nd rib, so counting from it is reliable.
§06
Lead placement questions
Anchor electrodes first, then the rest.
Before you look at the options, say the landmark out loud: the intercostal space and the line.
Where is the V2 electrode placed for a 12-lead EKG?
Answer & explanation
Answer: D. 4th intercostal space, left sternal border
V2 is placed at the 4th intercostal space on the left sternal border, directly across from V1 on the right sternal border. The 5th-space midclavicular position belongs to V4.
- The 5th space at the left midclavicular line is V4, one space lower and further out.
- The 4th space at the right sternal border is V1, V2's mirror across the sternum.
- The 2nd space is too high, and high V1 and V2 placement can mimic an anteroseptal MI.
- Correct: V2 sits in the 4th intercostal space at the left sternal border, directly across from V1.
A healthy patient's 12-lead EKG shows inverted P waves and QRS complexes in lead I. What should the MA check first?
Answer & explanation
Answer: C. Reversal of the RA and LA electrodes
Swapping the right-arm (white) and left-arm (black) electrodes inverts the P wave and QRS in lead I, mimicking dextrocardia, so limb leads are checked and the tracing is repeated. V1 and V2 placed too high change the precordial leads, not lead I. A 50 mm/s paper speed widens complexes, and muscle tremor adds irregular artifact rather than flipping the waves.
- Muscle tremor adds irregular jagged artifact; it does not flip the P wave and QRS.
- High V1–V2 placement changes the chest leads, not lead I, which is a limb lead.
- Correct: swapped white (RA) and black (LA) electrodes invert lead I and mimic dextrocardia.
- 50 mm/s paper widens complexes horizontally but never inverts them.
Where is the V1 electrode placed for a 12-lead EKG?
Answer & explanation
Answer: B. 4th ICS, right sternal border
V1 goes in the 4th intercostal space just right of the sternum. The 4th ICS at the left sternal border is V2, the mirror image that candidates often confuse with V1, and the 5th ICS at the left midclavicular line is V4. Placing V1 in the 2nd ICS is a common too-high error that can mimic an anteroseptal MI.
- The 2nd ICS is the classic too-high error and can mimic an anteroseptal MI.
- Correct: V1 goes in the 4th ICS just right of the sternum.
- The 5th ICS at the left midclavicular line is V4.
- The 4th ICS left sternal border is V2, the mirror-image position often confused with V1.
In the US (AHA) color code for limb electrodes, which color electrode is placed on the left arm?
Answer & explanation
Answer: B. Black
Under the AHA scheme the left arm electrode is black; white is right arm, red is left leg, and green is right leg. A memory aid is that smoke (black) sits over fire (red) on the left side.
- White goes on the right arm under the AHA scheme.
- Correct: left arm is black — 'smoke over fire' puts black above red on the left side.
- Red goes on the left leg, below the black left-arm electrode.
- Green goes on the right leg and acts as the ground.
Where is the V4 precordial electrode placed on a 12-lead EKG?
Answer & explanation
Answer: A. 5th intercostal space, left midclavicular line
V4 sits at the 5th intercostal space on the left midclavicular line, and V5 and V6 are placed level with it. The 4th intercostal space positions belong to V1 (right sternal border) and V2 (left sternal border).
- Correct: V4 sits in the 5th ICS on the left midclavicular line; V5 and V6 line up with it.
- The 4th ICS at the right sternal border is V1.
- The 4th ICS at the left sternal border is V2.
- The anterior axillary line is V5, which sits level with V4, not above it.
The V1 and V2 electrodes are mistakenly placed in the 2nd intercostal space instead of the 4th. What effect can this have on the tracing?
Answer & explanation
Answer: D. It can mimic an anteroseptal myocardial infarction
Placing V1 and V2 too high (2nd or 3rd intercostal space) can produce patterns that falsely suggest an anteroseptal MI. Correct placement in the 4th intercostal space avoids this misleading appearance.
- Chest leads record from fixed positions, so moving them two spaces does change the waveforms.
- Limb-lead polarity changes with arm-electrode reversal, not chest-lead height.
- P waves remain; misplacement alters QRS shape in V1–V2 rather than deleting atrial activity.
- Correct: high V1–V2 placement can produce patterns that falsely suggest an anteroseptal MI.
The V6 electrode is correctly positioned at which location?
Answer & explanation
Answer: A. Midaxillary line, level with V4
V6 is placed on the left midaxillary line at the same horizontal level as V4, not riding up along the ribs. The midclavicular and right sternal positions belong to V4 and V1 respectively.
- Correct: V6 sits on the left midaxillary line at the same horizontal level as V4.
- The midclavicular line at the 5th ICS is V4's position.
- The 4th ICS at the right sternal border is V1.
- The anterior axillary line is V5, and it sits level with V4, not above it.
Using the AHA color code, which color electrode goes on the patient's left leg?
Answer & explanation
Answer: C. Red
In the AHA scheme, the right arm is white, the left arm black, the left leg red, and the right leg green; a common memory aid is 'white on right, smoke (black) over fire (red).' Green is the tempting choice because it is also a leg electrode, but it belongs on the right leg as the ground. Black belongs on the left arm and white on the right arm.
- Green is also a leg electrode, but it goes on the right leg as the ground.
- White goes on the right arm, as in the memory aid 'white on the right.'
- Correct: in the AHA code the left leg is red, as in 'smoke over fire': black above red.
- Black goes on the left arm, sitting above the red left-leg electrode.
How many electrodes are placed on the patient for a standard 12-lead EKG?
Answer & explanation
Answer: D. Ten electrodes
A 12-lead EKG uses 10 electrodes: four on the limbs and six on the chest, and the machine combines them into 12 views, or leads. Twelve is the tempting answer because it matches the name of the test. Six is the number of chest electrodes alone, and five is a common monitoring setup.
- Six is the chest electrodes alone; the four limb electrodes are still needed.
- Twelve is the number of leads, or views, not the number of electrodes on the skin.
- Five electrodes is a common monitoring setup, not a standard 12-lead EKG.
- Correct: four limb and six chest electrodes make ten, and the machine combines them into twelve views.
That is the whole set. Open any card to re-read its explanation, or start over.