NHA EKG Technician cheat sheet

Standard precautions apply to every patient regardless of diagnosis: blood and all body fluids are treated as potentially infectious, and gloves are worn whenever contact with them is possible.

Hand hygiene decision rule: alcohol-based rub when hands are not visibly soiled; soap and water when visibly soiled and after care of patients with C. difficile or norovirus, because alcohol does not reliably kill spores.

Identify the patient with two independent identifiers (full name plus date of birth or medical record number) before applying electrodes or acquiring any tracing.

Skin preparation sequence: clean with alcohol, allow to dry fully, abrade lightly if impedance is high; oily, moist, or hairy skin raises impedance and increases artifact.

Excess chest hair is clipped with clippers or scissors per policy rather than shaved; shaving creates micro-abrasions that increase infection risk and degrade electrode contact.

Electrical safety rule: equipment must be grounded through a three-prong plug, extension cords are not daisy-chained, and cables are kept away from wet surfaces and heat sources.

Artifact control: keep the patient warm to prevent shivering, support the limbs, and instruct quiet normal breathing; somatic tremor produces high-frequency spiky baseline interference.

For a resting 12-lead EKG the patient lies supine with arms at the sides and legs uncrossed; exercise, smoking, and caffeine are avoided for roughly 30 minutes before the test per facility policy.

Normal conduction sequence: SA node → atrial and internodal pathways → AV node (delay about 0.1 s) → bundle of His → right and left bundle branches → Purkinje fibers.

Intrinsic pacemaker rates: SA node 60-100 bpm, AV junction 40-60 bpm, ventricular Purkinje system 20-40 bpm; the fastest pacemaker normally dominates.

Normal intervals at 25 mm/s: PR 0.12-0.20 s (3-5 small boxes); QRS less than 0.12 s (under 3 small boxes); QT varies with rate and is corrected as QTc = QT ÷ √RR (Bazett).

Waveform meanings: P wave = atrial depolarization, QRS = ventricular depolarization, T wave = ventricular repolarization; atrial repolarization is hidden within the QRS.

A depolarization wave traveling toward a positive electrode produces an upward (positive) deflection; traveling away produces a downward deflection.

Normal frontal plane electrical axis is -30° to +90°; more negative indicates left axis deviation, more positive indicates right axis deviation.

Cardiac output = heart rate × stroke volume; normal adult resting output is about 4-8 L/min.

Ischemia territory by lead: right coronary artery → II, III, aVF; left anterior descending → V1-V4; circumflex → I, aVL, V5, V6.

Precordial placement: V1 = 4th intercostal space right sternal border; V2 = 4th ICS left sternal border; V3 = midway between V2 and V4; V4 = 5th ICS midclavicular line; V5 = anterior axillary line at V4 level; V6 = midaxillary line at V4 level.

US limb lead colors: right arm white, left arm black, left leg red, right leg green (ground); European coding differs and must be confirmed before use.

Paper speed 25 mm/s: 1 small box (1 mm) = 0.04 s; 1 large box (5 mm) = 0.20 s; 30 large boxes = 6 seconds.

Standard calibration is 10 mm/mV, so a 1 mV signal produces 10 mm (two large boxes) of deflection; any gain change (for example 20 mm/mV) must be documented on the tracing.

Right arm/left arm reversal produces a negative P wave and negative QRS in lead I with an upright aVR; arm/leg reversals produce other characteristic patterns that must be caught before reporting.

Artifact patterns: 60 Hz electrical interference = thick fuzzy baseline; baseline wander = slow sway from respiration or movement; somatic tremor = spiky irregular baseline.

A continuous artifact confined to one lead most often indicates a loose or dried electrode for that specific lead rather than a patient-wide problem.

Additional leads: right-sided V4R for suspected right ventricular infarction and posterior leads V7-V9 for suspected posterior myocardial infarction.

Each tracing is labeled with patient identifiers, date and time of acquisition, lead configuration or gain changes, and any symptoms present during recording.

Rate rules: 300 ÷ number of large boxes between R waves for regular rhythms; count QRS complexes in a 6-second strip × 10 for irregular rhythms.

Sinus rhythm criteria: rate 60-100, upright P in lead II before every QRS, PR 0.12-0.20 s, constant PP and RR intervals. Sinus bradycardia is under 60; sinus tachycardia is over 100.

Atrial fibrillation: irregularly irregular ventricular response, absent P waves, fibrillatory baseline. Atrial flutter: sawtooth waves at about 250-350/min, often 2:1 conduction giving a ventricular rate near 150.

AV block rule: first degree = PR over 0.20 s and constant; second degree type I = progressive PR lengthening until a QRS drops; type II = constant PR with sudden dropped QRS; third degree = complete AV dissociation.

PVC: wide QRS over 0.12 s, bizarre shape, no preceding P wave, usually a full compensatory pause; three or more consecutive PVCs at over 100 bpm define ventricular tachycardia.

Lethal rhythm responses: ventricular fibrillation (chaotic, no QRS) and pulseless ventricular tachycardia are shockable; asystole (flat line confirmed in two leads) is not shockable and is treated with CPR and epinephrine.

Acute injury markers: new ST elevation of at least 1 mm in two contiguous limb leads, or at least 2 mm in V2-V3 in men (1.5 mm in women), suggests STEMI; reciprocal depression supports the finding.

Torsades de pointes is polymorphic ventricular tachycardia with a twisting axis around the baseline and is associated with a prolonged QT interval.

Any critical finding is reported to the responsible provider immediately and the notification, time, and person contacted are documented.