EKG Mnemonics: 11 Memory Tricks for the NHA CET Exam

Limb lead colors (AHA)

“White on the right; smoke over fire; snow over grass”

White goes on the right arm (RA). Smoke over fire: black (LA) on the left arm sits above red (LL) on the left leg. Snow over grass: white on the right arm sits above green (RL) on the right leg. On a 5-lead monitor, brown is the chest electrode.

Use it when: When an item asks which colored lead goes where on a 12-lead, 5-lead or telemetry setup.

Careful: These are AHA (US) colors. The IEC scheme used outside the US is different (red RA, yellow LA, green LL, black RL), so an imported monitor can trap you. For a standard resting 12-lead, limb electrodes go on the limbs; moving them onto the torso, as in stress testing, changes the tracing and should be noted.

Chest lead placement

“Four, four, five; split the gap; stay level”

1. V14th intercostal space, right sternal border
2. V24th intercostal space, left sternal border
3. V45th intercostal space, left midclavicular line (place before V3)
4. V3Midway between V2 and V4
5. V5Left anterior axillary line, level with V4
6. V6Left midaxillary line, level with V4

Use it when: When an item names a chest lead and asks for its landmark, or describes a misplaced electrode.

Careful: Place V4 before V3, because V3 is defined as the midpoint. V5 and V6 follow V4's horizontal level, not the next rib space. The most common error is V1-V2 placed too high: find the sternal angle (level with the 2nd rib) and count down to the 4th space.

Artifact types and fixes

“Wander, Shiver, Buzz, Break”

1. WanderWandering baseline: slow drift from breathing, lotion, sweat, loose electrodes or pulled cables. Prep the skin and secure the cables.
2. ShiverSomatic tremor: irregular, jagged fuzz from muscle tension, cold, talking or tremor. Warm, relax and support the patient.
3. Buzz60-cycle AC interference: a regular, evenly thick line from nearby electrical devices or poor grounding. Unplug nonessential equipment and straighten cables.
4. BreakInterrupted baseline: gaps or sharp breaks from a broken lead wire or detached electrode. Reattach or replace.

Use it when: When a stem describes or shows a tracing problem and asks for the artifact name or the fix.

Careful: AC interference is regular and evenly spaced; somatic tremor is irregular. Both can mimic atrial flutter or fibrillation, so fix the artifact before anyone reads the rhythm. The machine's filter cleans the line but can hide detail, so remove the source first.

Limb lead reversal

“Lead I upside down? Look at the arms.”

If lead I is entirely negative (inverted P, QRS and T) and aVR is upright, the right and left arm electrodes are almost always reversed. Check the labels, correct them and repeat the tracing before it is submitted.

Use it when: When a tracing has an unexpected inverted limb lead or a near-flat limb lead.

Careful: Dextrocardia gives the same lead I picture but also loses R-wave progression across V1-V6; arm reversal leaves the chest leads normal. A nearly flat lead II points to the right arm and right leg (ground) electrodes being swapped.

Heart rate from the big boxes

“300, 150, 100, 75, 60, 50”

Find an R wave on a heavy line, then count heavy lines to the next R wave: 300, 150, 100, 75, 60, 50. The same math as formulas: 300 divided by the number of large boxes between R waves, or 1,500 divided by the number of small boxes.

Use it when: When an item gives a regular strip and asks for the heart rate.

Careful: This only works for regular rhythms at the standard 25 mm/sec. For an irregular rhythm such as atrial fibrillation, count the QRS complexes in a 6-second strip (30 large boxes) and multiply by 10.

Heart blocks

“If R is far from P, then you have a first degree. Longer, longer, longer, drop: then you have a Wenckebach. If some P's don't get through, then you have a Mobitz II. If P's and Q's don't agree, then you have a third degree.”

1. 1stPR interval over 0.20 s and constant; every P wave is followed by a QRS
2. M-ISecond-degree Mobitz I (Wenckebach): PR lengthens until a QRS drops, then resets
3. M-IISecond-degree Mobitz II: PR constant, then a P wave suddenly is not followed by a QRS
4. 3rdComplete block: P waves and QRS complexes beat independently of each other

Use it when: When a strip shows P waves without QRS complexes, or a long PR interval, and asks you to name the block.

Careful: A 2:1 block cannot be called Mobitz I or II from the strip, because there are never two conducted beats in a row to compare PR intervals. Mobitz II and third-degree block can deteriorate quickly; report them to the provider at once.

Lead groups and heart walls

“SAIL”

1. SSeptal: V1, V2
2. AAnterior: V3, V4
3. IInferior: II, III, aVF
4. LLateral: I, aVL, V5, V6

Use it when: When an item gives ST elevation in a group of leads and asks which wall is involved.

Careful: Anteroseptal means V1-V4 together. Expect reciprocal ST depression in the opposite group, such as I and aVL during an inferior STEMI. Right ventricular infarction needs right-sided leads (V4R), and posterior infarction shows as ST depression in V1-V3, confirmed with posterior leads V7-V9.

Shockable rhythms

“Shock the V's, not the flat line”

Ventricular fibrillation and pulseless ventricular tachycardia are shockable: a defibrillator or AED can reset them. Asystole and pulseless electrical activity are not shockable; they are treated with CPR and medications.

Use it when: When a strip shows a life-threatening rhythm and the item asks for the immediate action.

Careful: Check the patient, not just the monitor: a detached lead looks like asystole, and patient movement can look like VF. Ventricular tachycardia with a pulse is a different situation, and its treatment is the provider's decision. The technician's first actions are to check responsiveness and call for help.

Holter monitor instructions

“Diary, Dry, Daily routine”

1. DDiary: record activities, symptoms and the time they happen
2. DDry: no showering, bathing or swimming while connected
3. DDaily routine: keep doing normal activities, including the ones that bring on symptoms

Use it when: When an item asks what to tell a patient going home with a Holter monitor, or which instruction is wrong.

Careful: Normal activity is the point of the test; telling the patient to avoid the activity that triggers symptoms defeats it. Keep the recorder away from magnets, metal detectors and electric blankets. An event monitor is different: the patient presses a button to record when symptoms occur.

Adult CPR (BLS)

“C-A-B: push hard, push fast, 30:2”

1. CCompressions: 100-120 per minute, 2-2.4 inches deep, full chest recoil
2. AAirway: head tilt-chin lift (jaw thrust if a spinal injury is suspected)
3. BBreathing: 2 breaths, each over 1 second with visible chest rise, after every 30 compressions

Use it when: When a patient becomes unresponsive during testing and the item asks for the sequence, rate, depth or ratio.

Careful: The old A-B-C order is outdated. For adults, 30:2 applies with one or two rescuers until an advanced airway is placed. The 2025 AHA guidelines also changed choking care for responsive adults to cycles of 5 back blows and 5 abdominal thrusts.

Stress test target heart rate

“220 minus age, then 85%”

Age-predicted maximum heart rate is 220 minus the patient's age. An exercise stress test usually aims for at least 85% of that maximum. Example: a 60-year-old has a predicted maximum of 160 bpm, so the target is about 136 bpm.

Use it when: When an item gives a patient's age and asks for the maximum or target heart rate during a stress test.

Careful: The formula is only an estimate, and beta blockers blunt the heart rate response. Reaching the target is not the only reason a test ends: chest pain, dizziness, a falling blood pressure, a dangerous arrhythmia or the patient's request to stop all end it, and the technician reports these to the provider immediately.