RRB ECG Technician flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

Einthoven's law

Lead II voltage equals lead I plus lead III at any instant, because the three bipolar limb leads form a closed triangle. A broken lead cable can be detected by this relationship failing.

Wilson central terminal

The average of the potentials at the right arm, left arm and left leg, used as the reference electrode for the unipolar chest leads V1 to V6 and the augmented limb leads.

Standard calibration

A 1 mV signal is recorded as a 10 mm deflection at a paper speed of 25 mm/s. This standardisation pulse must appear at the start and end of every ECG tracing.

Paper speed 25 mm/s

At 25 mm/s, one small square (1 mm) represents 0.04 seconds and one large square (5 mm) represents 0.20 seconds. All interval measurements depend on this calibration.

PR interval normal range

The interval from the start of the P wave to the start of the QRS complex, normally 0.12 to 0.20 seconds (three to five small squares). Prolongation beyond 0.20 seconds indicates first degree AV block.

QTc by Bazett

Corrected QT equals the measured QT divided by the square root of the RR interval in seconds. Normal QTc is about 0.35 to 0.44 seconds; prolongation raises torsades risk.

QRS duration significance

A QRS complex under 0.12 seconds indicates normal ventricular conduction. A width of 0.12 seconds or more suggests bundle branch block, ventricular ectopy, or a paced rhythm.

Rate from large squares

For regular rhythms, divide 300 by the number of large squares between two consecutive R waves. For example, four large squares give a rate of 75 beats per minute.

Atrial fibrillation criteria

Irregularly irregular RR intervals with no identifiable P waves and a fibrillatory baseline. The ventricular rate may be fast, normal or slow and must be documented on the tracing.

Atrial flutter pattern

Regular sawtooth flutter waves at about 300 per minute, best seen in leads II, III and aVF. With 2:1 conduction the ventricular rate is close to 150 per minute.

Wenckebach phenomenon

Second degree AV block Mobitz I, in which the PR interval progressively lengthens until a QRS complex is dropped. The pause is less than twice the preceding RR interval.

Complete heart block

Third degree AV block with complete dissociation between atria and ventricles. P waves and QRS complexes are independent, and the ventricular escape rhythm is slow and often broad.

Ventricular fibrillation

Chaotic, irregular electrical activity with no identifiable P waves, QRS complexes or T waves. It is a cardiac arrest rhythm requiring immediate CPR and defibrillation.

Inferior STEMI leads

ST elevation in leads II, III and aVF indicates inferior wall infarction, usually from right coronary artery occlusion, often with reciprocal ST depression in leads I and aVL.

Anterior STEMI leads

ST elevation in leads V1 to V4 indicates anterior wall infarction, typically from left anterior descending artery occlusion. Reciprocal depression may appear in inferior leads.

Hyperkalaemia ECG changes

Tall peaked T waves progressing to flattened P waves, widened QRS complexes and eventually a sine wave pattern. These changes are a medical emergency requiring urgent potassium correction.

Pericarditis ECG pattern

Widespread concave ST elevation and PR depression across many leads without reciprocal ST depression. The pattern differs from the territorial distribution seen in myocardial infarction.

Left ventricular hypertrophy

Deep S wave in V1 plus tall R wave in V5 or V6 exceeding 35 mm, or R in aVL above 11 mm. Associated ST depression and T inversion are called strain pattern.

Baseline wander artefact

Slow, undulating shift of the isoelectric line caused by respiration, patient movement or loose electrodes. Correct it by stabilising the patient and reapplying electrodes rather than heavy filtering.

AC interference artefact

Uniform high-frequency thickening of the baseline at exactly 50 Hz from mains supply in India. It results from poor electrode contact, dry skin or a faulty ground connection.

Muscle tremor artefact

Irregular high-frequency spikes from voluntary muscle activity, shivering or Parkinsonism. It differs from AC interference by being irregular in amplitude and not exactly 50 Hz.

Silver chloride electrode

A silver electrode coated with silver chloride, giving a stable low half-cell potential and low polarisation. It reduces baseline drift and motion artefact during ECG recording.

Lead I reversal sign

If the right and left arm electrodes are swapped, lead I becomes inverted with a negative P wave and QRS, and leads aVR and aVL exchange their appearances.

Cardiac output formula

Cardiac output equals heart rate multiplied by stroke volume. At rest this is about 70 beats per minute times 70 millilitres, giving roughly 5 litres per minute.

SA node intrinsic rate

The sinoatrial node depolarises spontaneously at 60 to 100 per minute and normally sets the heart rate. The AV node fires at 40 to 60 and Purkinje fibres at 20 to 40 per minute.

Coronary artery supply

The left main coronary artery divides into the left anterior descending and circumflex arteries. The right coronary artery supplies the right ventricle and usually the AV node.

Bipolar limb leads

Leads I, II and III measure potential differences between two limbs: right arm to left arm, right arm to left leg, and left arm to left leg respectively.

Standard precautions

Hand hygiene, gloves, gowns, masks and eye protection applied to all patients regardless of diagnosis. Hand hygiene before and after patient contact is the single most effective measure.

Biomedical waste colour coding

Yellow bag for anatomical and soiled waste, red bag for contaminated recyclable plastics, and puncture-proof white translucent container for sharps. Never recap needles before disposal.

Informed consent elements

The patient must be told the purpose, procedure, risks and alternatives in a language they understand, and must agree voluntarily. Consent may be withdrawn at any time.

DICOM waveform format

A medical imaging and waveform standard that stores the ECG signal together with patient and machine metadata. Anonymising requires removing identifiers from the file header.

DPDP Act 2023

India's Digital Personal Data Protection Act governs processing of digital personal data, including health records. It requires consent and imposes duties on data fiduciaries handling patient information.