Getting certified as a Certified EKG Technician (CET) is about more than reading squiggly lines. The exam tests whether you can produce accurate tracings, recognize clinically significant patterns, and keep patients safe while you do it. Most CET exams (such as NHA) have about 100 questions in roughly two hours, so mistakes usually come from rushing, guessing based on memory, or missing small details that change the entire question. Below are the five errors I see most often—and the practical ways to avoid every one of them.
Mistake 1: Eyeballing the rhythm instead of using a system
Students fail rhythm questions when they “go with their gut.” The heart rewards method, not intuition. A systematic approach catches small details—like a subtle P wave or a prolonged PR—that completely change the answer.
Use a seven-step rhythm checklist on every strip:
- Confirm settings: Paper speed 25 mm/s, gain 10 mm/mV. If the gain is doubled, everything looks tall; if the speed is 50 mm/s, intervals look long. The exam expects you to recognize that.
- Rate: For regular rhythms, use large boxes between R waves: 1=300, 2=150, 3=100, 4=75, 5=60, 6=50. For irregular rhythms, count R waves in 6 seconds (30 large boxes) and multiply by 10.
- Regularity: Are R–R intervals consistent? Irregularly irregular with no P waves usually means atrial fibrillation.
- P waves: Present? Upright in lead II? One P before every QRS? If P waves march through regardless of QRS, think AV dissociation.
- PR interval: Normal is 0.12–0.20 s (3–5 small boxes). Progressively lengthening PR that drops a beat suggests Mobitz I (Wenckebach). Constant PR with dropped QRS suggests Mobitz II.
- QRS width: Narrow (<0.12 s) usually supraventricular; wide (≥0.12 s) may be ventricular or bundle branch block.
- ST–T changes: ST elevation or depression and T-wave inversions carry clinical weight. The exam may ask what to do next, not just “what is it?”
Example: A strip shows grouped beating, PR intervals that get longer, then a dropped QRS. The systematic approach identifies this as Mobitz I. Without the steps, many pick “complete heart block” because of the dropped beat.
Why this works: A checklist keeps you from missing the one criterion that distinguishes similar rhythms. It also speeds you up—ironically, method is faster than guessing.
How to practice:
- Drill 10–20 random strips daily. Speak the seven steps out loud. Time yourself to 60–75 seconds per question.
- Write down expected values: PR 0.12–0.20 s; QRS <0.12 s; QT roughly less than half the R–R interval (rate-adjusted in practice, but the exam wants the concept).
- Use the 6-second method for irregular rhythms to avoid calculation traps.
Mistake 2: Confusing artifact and lead problems with arrhythmias
Many exam questions hide the answer in the patient or environment description. You’re expected to recognize that the tracing is the problem—not the heart. Treating artifact as VTach is a classic error.
Artifact patterns and fixes you must recognize:
- Wandering baseline: Slow, undulating baseline from breathing, poor skin contact, or oily skin. Fix: Clean and dry the skin, lightly abrade with gauze, reposition to bony/fleshy stable areas.
- Somatic tremor: Jagged, erratic spikes, often in anxious, cold, or Parkinsonian patients. Fix: Warm blanket, support the limbs, ask patient to relax jaw/shoulders.
- 60-cycle interference: Uniform, high-frequency “buzz.” Fix: Unplug unnecessary equipment, use a grounded outlet, keep lead wires untangled and away from power cords.
- Loose electrode/lead: Intermittent wandering or flatlining in one lead. Fix: Re-prep skin, replace electrode, check cable connections.
- Limb lead reversal: Right–left arm switch makes lead I negative and aVR positive; global inversion can mimic pathology. Fix: Re-verify limb placement before interpreting.
Exam cue: If the stem says the “patient is shivering” or “diaphoretic with oily skin,” the best answer is almost always about improving skin prep or comfort—not diagnosing an arrhythmia.
Why this matters: Poor-quality tracings cause real-world misdiagnosis and extra testing. The exam rewards the tech who fixes the signal before labeling a rhythm.
Mistake 3: Weak electrode and lead placement—especially in special situations
Incorrect landmarks create false ST changes, abnormal R-wave progression, and wrong axis—problems that can look like ischemia, BBB, or chamber enlargement. The exam often hides the entire question behind a single words: “landmark.”
12-lead chest (precordial) placement:
- V1: 4th intercostal space (ICS), right sternal border.
- V2: 4th ICS, left sternal border.
- V4: 5th ICS, left midclavicular line.
- V3: Midway between V2 and V4.
- V5: Left anterior axillary line, level with V4.
- V6: Left midaxillary line, level with V4/V5.
Limb leads: Place on fleshy, distal parts of limbs (upper arms, lower legs). If needed, you may move them to the torso for tremor or amputation, but document the change.
Landmarking tips that save points:
- Find the sternal angle (Angle of Louis), slide to the 2nd rib, then count down to the 4th ICS for V1/V2. Don’t “eyeball” around breast tissue.
- For patients with large breasts, lift the breast and place V3–V6 on the chest wall at the correct intercostal spaces—not on the breast itself.
- In obesity, take your time palpating. Correct beats fast.
Special lead sets the exam loves:
- Right-sided ECG (V1R–V6R): Mirror V1–V6 to the right chest when a right ventricular infarct is suspected (e.g., inferior MI signs, hypotension). V4R is most sensitive.
- Posterior leads (V7–V9): Place horizontally from the posterior axillary to paraspinal line at the level of V6 to detect posterior MI.
- Pediatrics: Landmarks are the same; use smaller electrodes and gentle prep. Right-sided leads are common in some congenital conditions.
Quick self-checks before you hit “print”:
- In a normal tracing, lead I should be mostly positive, aVR mostly negative. If not, re-check limb leads.
- R-wave amplitude should generally increase from V1 to V4–V5. Sudden odd patterns often indicate misplacement.
Why this matters: Lead errors aren’t just “technical.” They change the medical story the heart is telling. The exam expects you to protect that story by placing leads correctly and documenting any deviations.
Mistake 4: Poor time management and weak question strategy
With about two hours for roughly 100 questions, you get around 70 seconds per item. Many students burn three minutes on one puzzle and then rush through five easy points later. Strategy is part of clinical safety: it helps you make good decisions under time pressure.
Use a three-pass method:
- Pass 1: Answer the easy ones instantly; flag anything that isn’t obvious. Keep moving.
- Pass 2: Return to flagged questions. Eliminate distractors and choose the best remaining option.
- Pass 3: Resolve the hardest items. Don’t leave blanks; unanswered items can’t score.
Read the question’s last line first. Command words matter:
- “Initial,” “first,” “priority” = safety before completeness (stop the test, verify patient, assess responsiveness before notifying).
- “Best,” “most appropriate” = choose the action that is safe, within scope, and solves the stated problem.
Scope-of-practice filter: A CET acquires and triages. You do not diagnose MIs, interpret axis for treatment, or administer meds. You recognize danger and escalate: stop the test, stay with the patient, notify the RN/provider, and follow facility protocol.
Fast math you must nail:
- Large box method (regular): 300–150–100–75–60–50 for 1–6 boxes.
- 6-second method (irregular): Count R waves in a 6-second span and multiply by 10.
- Intervals: Each small box = 0.04 s; each large box = 0.20 s. PR 3–5 small boxes; QRS 1–3 small boxes.
When to change an answer: Only if you find new information you missed (e.g., you now see P waves marching through). Otherwise, first instincts after a careful read are usually better than second-guessing.
Why this works: Time you save on straightforward items buys focus for the few that truly require analysis. The exam rewards consistent, safe decisions—not heroics on one item.
Mistake 5: Treating safety, legal, and communication items as “common sense”
These questions are not fluff. Safety and professionalism are a major portion of the blueprint because they prevent harm. Many students know the clinical content but miss easy points by skipping the basics.
Safety-first algorithm for any scenario:
- Stop the test if the patient is unstable. If a patient develops chest pain, severe shortness of breath, or syncope, don’t “finish the lead.” Stop, assess, and call for help.
- Assess and stay with the patient. Check responsiveness, airway, breathing, circulation. Position for comfort unless contraindicated.
- Activate help rapidly. Notify the RN/provider or call emergency response per protocol. You don’t diagnose; you escalate.
- Document events. Note time, symptoms, actions taken, and any deviations (e.g., right-sided ECG).
Infection control you’ll be tested on:
- Hand hygiene before and after patient contact or glove use. Gloves for non-intact skin or contact with body fluids.
- Equipment cleaning between patients. Single-patient electrodes when possible; otherwise, disinfect per manufacturer guidelines.
- Isolation precautions: Use appropriate PPE for contact or droplet isolation and wipe leads after use.
Identification and consent:
- Always use two identifiers (full name and DOB or medical record number). A wristband alone is not enough if the patient is confused or mislabeled.
- Explain the procedure in plain language and check understanding. Anxiety increases artifact and poor cooperation.
HIPAA and professionalism:
- Do not discuss results in hallways or with unauthorized family members. Secure printouts immediately; never leave tracings on machines.
- When asked for interpretation beyond scope, use professional language: “I’ll make sure the provider reviews your tracing right away.”
Electrical and environmental safety:
- Use grounded outlets. Remove frayed cables from service. Keep the machine away from water and heated blankets to avoid interference.
- If you see uniform high-frequency noise, suspect electrical interference before “VTach.”
Why this matters: The safest correct answer usually wins on the exam. If two answers look clinically sound, pick the one that protects the patient and stays within your role.
Putting it together: How to prepare so you don’t make these mistakes
Master the blueprint: Most CET exams cover patient prep and safety, EKG acquisition, quality control and troubleshooting, basic rhythm interpretation, and professionalism. Weight your study time accordingly; don’t overtrain rhythm at the expense of safety and lead placement.
Daily 30-minute practice loop:
- 10 minutes: Flash-drill normal values and the seven-step rhythm checklist.
- 10 minutes: Interpret 6–8 strips under time (60–75 seconds each). Write the final diagnosis and one sentence on why.
- 10 minutes: Scenario questions focused on artifact, lead placement, and safety. Say out loud which command word (initial, best, priority) controlled your answer.
Before the exam:
- Sleep, hydrate, and eat. Cognitive lapses look like “knowledge gaps” but are really fatigue.
- Plan your pacing: Question number ÷ 2 ≈ minutes elapsed is a rough check (e.g., by question 40, about 80 minutes left in a 120-minute window).
- Decide your “default” for borderline choices: when unsure, pick the answer that improves tracing quality or patient safety without exceeding scope.
Final thought: CET success is not about memorizing every arrhythmia. It’s about reliable process, clean signal, correct landmarks, disciplined pacing, and safety-first judgment. If you practice those five skills, you’ll avoid the most common pitfalls and walk into the exam with the same calm approach you’ll use at the bedside—methodical, accurate, and patient-centered.
I am a Registered Pharmacist under the Pharmacy Act, 1948, and the founder of PharmacyFreak.com. I hold a Bachelor of Pharmacy degree from Rungta College of Pharmaceutical Science and Research. With a strong academic foundation and practical knowledge, I am committed to providing accurate, easy-to-understand content to support pharmacy students and professionals. My aim is to make complex pharmaceutical concepts accessible and useful for real-world application.
Mail- Sachin@pharmacyfreak.com