CCMA practice test/EKG lead placement
Stop 5 · EKG room · printable chart
EKG lead placement chart
A 12-lead EKG uses ten electrodes: V1 and V2 in the 4th intercostal space on either side of the sternum, V4, V5 and V6 in the 5th, V3 between V2 and V4, and one electrode on each limb.
10 electrodes · 6 chest, 4 limb · sources checked 2026-11-10
The chart
12-lead EKG electrode placement
The patient faces you, so their right side is on your left. Pick an electrode to see where it goes.
a midclavicular line · b anterior axillary line · c mid-axillary line
Chest electrode1 of 10
V1
4th intercostal space, to the right of the sternum
The patient's right, which is your left as you face them.
| Electrode | Where it goes | How to find it |
|---|---|---|
| V1 | 4th intercostal space, to the right of the sternum | The patient's right, which is your left as you face them. |
| V2 | 4th intercostal space, to the left of the sternum | Level with V1, on the other side of the sternum. |
| V3 | Midway between V2 and V4 | It is defined by its two neighbors, so place V4 first and then V3. |
| V4 | 5th intercostal space at the midclavicular line, left side | One space lower than V1 and V2, on the line dropped from the middle of the collarbone. |
| V5 | 5th intercostal space, anterior axillary line | The same space as V4, at the front fold of the armpit. |
| V6 | 5th intercostal space, mid-axillary line | The same space as V4 and V5, on the line dropped from the middle of the armpit. |
| RA (right arm) | Right wrist, or above the elbow | Right means the patient's right. |
| LA (left arm) | Left wrist, or above the elbow | Left means the patient's left, which is your right as you face them. |
| RL (right leg) | Right leg, between the knee and the ankle | It is not the positive or negative end of any of the 12 leads listed below. |
| LL (left leg) | Left leg, between the knee and the ankle | Leads II, III and aVF all use this electrode. |
Electrode positions per University of Rochester Medical Center, ECG Lead Placement. Free chart from quizcram.com/tools/ekg-lead-placement
Count the spaces from the top: the 4th intercostal space is the gap under the 4th rib. V1 and V2 share it; V4, V5 and V6 share the 5th. For study and general information; your clinic’s procedure and the machine’s instructions come first.
Positions: University of Rochester Medical Center, ECG Lead Placement. Ten electrodes, six chest and four limb: OpenStax, Anatomy and Physiology 2e, section 19.2.
| Lead | Electrodes | Direction it shows |
|---|---|---|
| IBipolar limb leads · frontal plane | RA (−) to LA (+) | Right to left (lateral) |
| IIBipolar limb leads · frontal plane | RA (−) to LL (+) | Superior to inferior |
| IIIBipolar limb leads · frontal plane | LA (−) to LL (+) | Superior to inferior |
| aVRAugmented limb leads · frontal plane | RA (+) against LA and LL | Rightward |
| aVLAugmented limb leads · frontal plane | LA (+) against RA and LL | Leftward |
| aVFAugmented limb leads · frontal plane | LL (+) against RA and LA | Inferior |
| V1, V2, V3Chest leads · horizontal plane | Each chest electrode is positive | Posterior to anterior |
| V4, V5, V6Chest leads · horizontal plane | Each chest electrode is positive | Right to left (lateral) |
Ten electrodes, twelve leads
The 12 EKG leads and what each one shows
A lead is not a wire. It is the voltage difference between electrodes, which is how ten electrodes give twelve views of the heart.
The three bipolar limb leads (I, II, III) each compare two limb electrodes. The three augmented limb leads (aVR, aVL, aVF) each take one limb electrode as positive against the other two. Those six look at the heart in the frontal plane.
The six chest leads, V1 to V6, look in the horizontal plane: V1 to V3 from back to front, V4 to V6 from right to left.
The right leg electrode is not the positive or negative end of any lead in this list, but the recording still needs all ten electrodes in place.
Leads and directions: University of Utah, ECG Learning Center, The Standard 12 Lead ECG. Definition of a lead: OpenStax, Anatomy and Physiology 2e, section 19.2.
Before you record
How to prepare a patient for an EKG
Movement and loose electrodes spoil a tracing. These steps come before and during the recording.
Have the patient lie down, relaxed and warm
Any movement, including shivering, can change the tracing.
Clean the skin and make sure it is dry
Electrodes stick to dry skin; an alcohol swab helps.
Clip or shave hair where a patch will not stick
The patches have to stay flat on the skin.
Keep the electrode stickers from touching each other
On a small chest they may need trimming.
Check the cable and lead connections
Do this before any electrode goes on.
Let the patient settle for more than 2 minutes
A settled patient gives less artifact.
Ask the patient to stay still, and to hold their breath if asked
Stillness for a few seconds gives a clean recording.
The patient should not exercise or drink cold water just before the test, because either can cause false results. One placement tip from the same hospital page: putting the arm stickers below the collarbone rather than on the shoulder helps prevent muscle twitch artifact.
Sources: MedlinePlus, Electrocardiogram · University of Rochester Medical Center, ECG Lead Placement.
Reading the tracing
EKG waves and intervals: what each one means
A medical assistant records the EKG; the provider reads it. Exam questions still expect you to name the parts of a normal tracing and what the heart is doing during each.
EKG and cardiovascular testing is 6 of the 150 scored questions on the NHA CCMA exam. That section of the test plan lists patient preparation, lead types and placement, artifacts, waveforms and abnormal rhythms.
Waves and intervals: University of Utah, ECG Learning Center, The Standard 12 Lead ECG.
- P wave
- The right and left atria depolarize, one after the other
- QRS complex
- The right and left ventricles depolarize
- ST-T wave
- The ventricles repolarize
- PR interval
- From the start of atrial depolarization to the start of ventricular depolarization
- QRS duration
- How long ventricular depolarization takes
- QT interval
- Ventricular depolarization and repolarization together
- RR interval
- One ventricular cycle, which shows the ventricular rate
EKG lead placement FAQ
Short answers, each from the source named.
4th intercostal space, to the right of the sternum. The right is the patient's right. V2 sits level with it on the other side of the sternum. Source: University of Rochester Medical Center, ECG Lead Placement.
Ten: six on the chest and four on the limbs. A lead is the voltage difference between electrodes, not a wire, which is how ten electrodes give twelve leads. Source: OpenStax, Anatomy and Physiology 2e, section 19.2.
The arm electrodes go on the wrist or above the elbow, and the leg electrodes between the knee and the ankle. Source: University of Rochester Medical Center, ECG Lead Placement.
V4: 5th intercostal space at the midclavicular line, left side. V3 is defined as midway between V2 and V4, so it can only be placed once those two are on.
Movement, including shivering, changes the tracing, so the patient should be relaxed, warm and still. Dry skin helps the electrodes hold, and letting the patient settle for more than 2 minutes reduces artifact. Sources: MedlinePlus, Electrocardiogram; University of Rochester Medical Center, ECG Lead Placement.
Both mean electrocardiogram. MedlinePlus lists ECG and EKG as alternative names for the same test.