Welcome to telemetry. As an EKG tech your job is to capture the heart's electrical story cleanly and hand it off fast — you acquire and report, the licensed team interprets and diagnoses. Get these fundamentals down and the machine becomes easy.
What an EKG is
The heart's electrical activity, drawn on paper
Every heartbeat starts as an electrical signal. Electrodes on the skin sense that signal and the EKG machine plots it as a waveform. A standard 12-lead EKG looks at the heart from 12 electrical "angles" using 10 electrodes.
Your scope as an EKG tech: acquire a technically clean tracing, label it correctly, and get it to the nurse/provider promptly. You do not diagnose and you do not tell the patient what the rhythm means. Recognizing a dangerous pattern so you can escalate is part of the job; interpreting it is not.
Reading the waveform
P – QRS – T
LEAD II · NORMAL SINUSP-QRS-T
P wave — the atria depolarize (top chambers squeeze).
QRS complex — the ventricles depolarize (the big pump beat).
T wave — the ventricles reset (repolarize).
Paper speed & scale (memorize): standard EKG runs at 25 mm/sec with a calibration of 10 mm/mV. One small box = 0.04 sec; one large box = 0.20 sec. That's how the team measures rate and intervals from your strip.
Where the signal comes from
The heart's electrical conduction system
Every waveform you capture starts as an electrical impulse traveling a fixed path through the heart. Knowing the path makes the tracing make sense:
SA node→AV node→Bundle of His→Bundle branches→Purkinje fibers
SA node — the heart's natural pacemaker (right atrium); fires the beat. Triggers the atria → the P wave.
AV node — the gatekeeper; briefly delays the signal so the atria finish filling the ventricles.
Bundle of His → right & left bundle branches → Purkinje fibers — carry the impulse fast through the ventricles → the QRS complex, the big pump beat.
Tie it back: P wave = atria (SA/AV), QRS = ventricles (His–Purkinje), T wave = the ventricles resetting. A rhythm problem is really a problem somewhere on this path.
🫀 360° Human Explorer — see the conduction system live in 3D
Rotate, zoom, and follow the impulse from the SA node through the AV node and His–Purkinje fibers — then switch to AFib with EKG to see a rhythm problem on the same heart. Open full screen ↗
The 10 electrodes
Limb leads + precordial (chest) leads
4 limb electrodes — the classic memory hooks
🤍 White on the right — RA (right arm)
💨 Smoke over fire — black (LA, left arm) sits above red (LL, left leg)
🌱 Clouds over grass — white (RA) above green (RL, right leg)
Green = RL is the ground/reference.
6 chest electrodes — V1 through V6 (get these exact)
V1 — 4th intercostal space, right sternal border
V2 — 4th intercostal space, left sternal border
V4 — 5th intercostal space, midclavicular line place V4 before V3
V3 — midway between V2 and V4
V5 — same level as V4, anterior axillary line
V6 — same level as V4, midaxillary line
Pro move: land V1, V2, then jump to V4 so you have the anchor, then drop V3 in between. V5 and V6 stay on the same horizontal level as V4 — not angled up toward the armpit.
A clean tracing
Artifact is your enemy
A messy strip can hide — or fake — a problem. Before you hit acquire:
Patient still & warm: shivering and muscle tension create fuzzy somatic tremor artifact. Talking/moving does too.
Wandering baseline: usually loose electrodes or breathing/movement — re-seat the electrode.
60-cycle interference: tidy, uncrossed lead wires; move away from unplugged-but-present electrical sources.
ARTIFACT — DO NOT SENDmuscle tremor
Rule of thumb: if you couldn't confidently point to P-QRS-T, the strip isn't clean enough to send. Re-prep and re-acquire.
Rhythms you'll see
Know normal — and know the "get help now" three
You're not diagnosing, but recognizing patterns tells you how urgently to hand the strip off.
Common & usually stable
Normal Sinus Rhythm (NSR) — P before every QRS, regular, ~60–100 bpm.
Sinus bradycardia — same pattern, <60 bpm. Report if new or symptomatic.
Sinus tachycardia — same pattern, >100 bpm. Report; often has a cause (pain, fever, fluid loss).
Atrial fibrillation (AFib) — irregularly irregular, no clear P waves. Report.
Recognize & escalate immediately — the trio
Ventricular tachycardia (VT) — wide, fast, regular; patient may be crashing.
Ventricular fibrillation (VF) — chaotic, no organized QRS; a code rhythm.
Asystole — flat line (confirm leads are on first!); a code rhythm.
LEAD IIV-Tach — escalate
If a monitor alarms for VT / VF / asystole: check the patient first (are they responsive? is a lead just off?), then call for help / activate your facility's rapid-response or code process per protocol. A flat line with a patient who's talking to you is almost always a lead problem — but you verify, you don't silence-and-ignore.
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Coach Katie
Tap the chest electrodes in the correct order — V1, V2, V4, V3, V5, V6. The highlighted button shows what's next. Land all six for the coins.
Interactive
Precordial (V1–V6) placement drill
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Coach Katie
Real shift. Read the strip, read the patient, and make the tech's call — what do you do next? Interpreting isn't your job; acquiring cleanly and escalating correctly is.
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Coach Katie
Six questions. 75% to pass and earn the EKG Basics stamp toward your PCT ladder.
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Coach Katie
Your patients — and their families — are showing up with EKGs from their watches and phones. You'll be asked "what does this mean?" all the time. Here's familiarity with the three most common consumer and home devices so you can speak to them and keep everyone inside a safe lane.
The one rule that covers all three: a consumer/home device gives a screening result, not a diagnosis. "Normal" doesn't rule out heart disease, and no reading replaces a clinician. For real symptoms — chest pain, fainting, severe shortness of breath — the answer is always call 911, not check a watch.
What it isA smartwatch (Series 4 and later) that records a single-lead, ~30-second ECG on demand — finger on the crown completes the circuit — roughly a Lead I view.
What it doesClassifies the strip as sinus rhythm, atrial fibrillation, or inconclusive. Separately, background optical (PPG) sensing can send an irregular-rhythm notification even when you're not taking an ECG.
StatusFDA-cleared (De Novo) for rhythm monitoring, not diagnosis. Not intended for users under 22 or those with a known AFib diagnosis.
LimitsShort, intermittent snapshots can miss an arrhythmia that isn't happening at that moment; single-lead can't localize a heart attack.
📱KardiaMobile / KardiaMobile 6L HANDHELD PAD · 1-LEAD or 6-LEAD
What it isA small handheld electrode pad (AliveCor). Rest a finger from each hand on it for a 30-second ECG that streams to a phone app. The 6L adds a knee electrode to capture all six limb leads.
What it doesFlags atrial fibrillation, bradycardia, tachycardia, and normal. The 6L gives a richer, multi-lead tracing closer to what a clinician reads.
StatusFDA-cleared personal ECG. A patient can email the PDF strip to their provider — handy, but still a screening tool.
LimitsEven 6 leads is not a 12-lead; good tracings depend on still hands and clean contact — the same artifact rules you just learned.
🩹Zio Patch (extended-wear monitor) PRESCRIBED · CONTINUOUS · UP TO 14 DAYS
What it isA single-use adhesive patch (iRhythm) a clinician prescribes. It sits on the chest and records continuously for up to ~14 days — no wires, worn through showers and sleep.
What it doesCaptures far more than a snapshot, so it catches infrequent rhythm events a watch would miss. The patient presses a button and logs symptoms as they happen.
StatusA medical-grade extended-wear Holter alternative. Most versions are not real-time — the patch is mailed back, analyzed by trained technicians, and a report goes to the physician.
Your roleCoach correct placement and skin prep, reinforce keeping a symptom diary, and reassure that "no instant readout" is normal — the value is the long recording.
Quick familiarity check
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Coach Katie
Last step — and the one that makes it stick. Learn It, Live It, Share It. You've learned the tracing and lived the tech's call; now turn it outward. Pick the pledges you'll actually keep. When you teach one calm, correct thing to someone at home, the ripple reaches the whole community.
Share It — the closing act
Carry it home: one clear message about EKGs
The most useful thing you can pass on isn't a diagnosis — it's a safe frame: a watch or home device is a screening snapshot, not a diagnosis, and real symptoms mean call 911, don't check a watch. Tick at least two pledges you'll follow through on.
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