RRB ECG Technician cheat sheet

Statutory basis for the post: the Railway Board created the ECG Technician category under the paramedical staff structure of Indian Railways; recruitment is conducted by RRB against notified vacancies.

Indian Railways zones: 17 zones plus Metro Railway Kolkata; production units include Chittaranjan Locomotive Works, Integral Coach Factory, and Rail Wheel Factory.

Constitutional facts: Article 21 guarantees the right to life and personal liberty, and the Supreme Court has read the right to health into it; Article 47 makes public health a Directive Principle.

National health programmes relevant to cardiac care: NPCDCS (National Programme for Prevention and Control of Cancer, Diabetes, CVD and Stroke) and the India Hypertension Control Initiative.

Health days: World Heart Day 29 September, World Hypertension Day 17 May, World No Tobacco Day 31 May, World Diabetes Day 14 November.

Key national institutions: ICMR (research), NCDC (disease control), AIIMS (tertiary care), and DGHS under the Ministry of Health and Family Welfare.

Emergency numbers in India: 112 for unified emergency response, 108 for ambulance services in most states, and 102 for pregnancy and child transport.

Government health insurance: Ayushman Bharat PM-JAY provides annual hospitalisation cover to eligible families; CGHS and railway medical schemes cover serving and retired railway employees.

Number series: check differences first, then ratios; alternating series often mix two independent progressions in odd and even positions.

Coding-decoding: for letter shifts, convert letters to positions 1-26; a constant shift indicates a Caesar-type code, while reversing the alphabet gives a mirror code (A=26, B=25).

Blood relations: draw a family tree with gender markers; never assume gender from a relationship word such as 'cousin' or 'doctor'.

Direction sense: N=+y, S=-y, E=+x, W=-x; a right turn rotates heading clockwise 90 degrees, a left turn anticlockwise.

Syllogism: apply Venn diagrams; a conclusion follows only if it is true in every possible diagram consistent with the premises.

Calendar: a normal year shifts the weekday by 1, a leap year by 2; the 100-year, 200-year and 300-year codes are 5, 3 and 1 respectively.

Clock: the minute hand moves 6 degrees per minute, the hour hand 0.5 degrees per minute, so the hands gain 5.5 degrees per minute on each other.

Coding puzzles: for seating and ranking questions, fix the certain facts first and test each ambiguous option against all stated conditions.

Ohm's law: V = IR; power P = VI = I squared R. ECG machines draw very small currents, so high input impedance is essential to avoid loading the patient circuit.

Electrical safety thresholds: currents above about 10 mA cause tetanic muscle contraction, and 100-300 mA across the heart can cause ventricular fibrillation; the ECG machine must limit patient leakage current to microampere levels.

Electrode-skin interface: the half-cell potential arises from the metal-electrolyte junction; silver/silver chloride electrodes give a stable, low-offset potential and low polarisation.

Electrolytes: sodium and potassium are the main extracellular and intracellular cations; potassium gradient across the myocardial membrane sets the resting membrane potential (about -90 mV).

Blood chemistry relevant to ECG: hyperkalaemia produces tall peaked T waves and widens the QRS; hypocalcaemia prolongs the QT interval.

Acid-base: normal arterial pH is 7.35-7.40; carbon dioxide is carried mainly as bicarbonate, and respiratory acidosis can accompany severe cardiac failure.

Units: 1 mV = 1000 microvolts; standard ECG calibration is 10 mm/mV, so 1 mm of paper equals 0.1 mV.

Paper speed 25 mm/s means 1 mm = 0.04 s and 5 mm (one large square) = 0.20 s; at 50 mm/s each small square is 0.02 s.

Memory units: 1 byte = 8 bits, 1 KB = 1024 bytes, 1 MB = 1024 KB; RAM is volatile and ROM is non-volatile.

ECG file formats: standard 12-lead interchange uses SCP-ECG (EN 1064) or XML/DICOM; PDF and JPEG are commonly used for printed reports but carry no measurement data.

DICOM stores waveform and patient metadata together; anonymising before sharing requires removal of patient identifiers in the header, not just the image.

Networking: an IP address identifies a device on a network, and a LAN connects devices in one building; hospital ECG networks usually run on a secured VLAN.

Operating system functions: process management, memory management and file storage; a device driver translates instructions into signals for peripherals such as ECG printers.

Data protection: passwords must be strong and unique, and patient data on removable media must be encrypted; the Indian DPDP Act 2023 governs personal digital data including health records.

Common shortcuts and terms: Ctrl+P prints, Ctrl+S saves, Ctrl+Z undoes; a backup is a copy kept separately from the original, while an archive is a long-term store.

Malware categories: virus (attaches to files), worm (self-replicating over networks), trojan (disguised as legitimate software), ransomware (encrypts data for payment).

Heart chambers and flow: right atrium receives superior and inferior vena cava, right ventricle pumps to the pulmonary artery, left atrium receives four pulmonary veins, and the left ventricle pumps into the aorta.

Valves: tricuspid between right atrium and ventricle, mitral (bicuspid) between left atrium and ventricle, aortic and pulmonary semilunar valves at ventricular outflow.

Coronary supply: the left main coronary artery divides into the left anterior descending and circumflex arteries; the right coronary artery supplies the right ventricle and, in most people, the AV node.

Conduction system: SA node (60-100/min intrinsic rate), AV node (40-60/min), bundle of His, bundle branches, and Purkinje fibres (20-40/min).

Cardiac cycle timing: total cycle about 0.8 s at 75/min; systole about 0.3 s and diastole about 0.5 s; the first heart sound is from AV valve closure, the second from semilunar valve closure.

Normal values: resting heart rate 60-100/min, stroke volume about 70 mL, cardiac output about 5 L/min, normal blood pressure below 120/80 mmHg.

Blood: plasma is about 55 percent of blood volume; erythrocytes carry oxygen via haemoglobin (normal 13-17 g/dL in men, 12-15 g/dL in women), and platelets number 1.5-4.5 lakh per microlitre.

Vessels and regulation: arteries carry blood away from the heart, veins have valves and low pressure, and blood pressure is regulated by baroreceptors in the carotid sinus and aortic arch via the medulla.

Einthoven's triangle relates limb leads: lead II = lead I + lead III. The Wilson central terminal averages the three limb potentials and serves as the reference for the chest leads.

Standard 12 leads: I, II, III (bipolar limb), aVR, aVL, aVF (augmented unipolar limb), and V1-V6 (precordial). V1 sits at the fourth intercostal space right sternal edge, V2 opposite on the left, and V4-V6 follow the fifth intercostal space.

Normal paper values at 25 mm/s and 10 mm/mV: PR 0.12-0.20 s (3-5 small squares), QRS under 0.12 s, QT corrected by Bazett's formula QTc = QT divided by the square root of RR.

P wave represents atrial depolarisation, normally upright in II and under 0.12 s wide and 2.5 mm tall; the QRS complex represents ventricular depolarisation, and the T wave represents ventricular repolarisation.

The PR segment is the isoelectric line after the P wave; the ST segment runs from the J point to the start of the T wave and is normally isoelectric.

Axis: normal QRS axis is -30 to +90 degrees; lead I positive and aVF positive indicates a normal axis, both negative indicates extreme axis deviation.

Rate rules: rate = 300 divided by the number of large squares between R waves; for irregular rhythms count QRS complexes in 30 large squares and multiply by 10.

Lead placement errors: reversed arm leads invert lead I and switch aVR with aVL; misplacement of V1-V2 too high produces a false rSR pattern resembling incomplete right bundle branch block.

Preparation sequence: explain the procedure, ensure privacy, position supine, expose the chest and limbs, abrade the skin lightly, and apply electrodes on clean dry skin without hair or sweat.

Electrode placement: limb electrodes on the forearms and lower legs (or shoulders and hips for exercise testing), avoiding bony prominences and sites over muscle that trembles.

Calibration: record a 1 mV standardisation pulse giving 10 mm deflection; note speed and gain on the tracing, and reduce gain to 5 mm/mV if the QRS complexes overlap.

Common artefacts: baseline wander from respiration or movement (correct with a stable resting position and a short breath-hold), and 50 Hz AC interference from poor electrode contact or nearby equipment (correct with skin preparation and a good ground).

Muscle tremor artefact is high-frequency and irregular, distinguished from AC interference which is uniform and exactly 50 Hz in India.

Wandering baseline caused by loose electrodes must be fixed, not filtered away, because high-pass filtering can distort the ST segment.

Machine checks before use: battery charge, paper supply and thermal print head, lead cable continuity, and correct date, time and patient identifiers entered.

Infection control in practice: clean reusable electrodes and cables with an approved disinfectant between patients, use single-use electrodes where available, and perform hand hygiene before and after contact.

Sinus rhythm criteria: P wave before every QRS, upright P in lead II, constant PR interval, rate 60-100/min. Sinus bradycardia is under 60/min and sinus tachycardia over 100/min.

Atrial fibrillation: irregularly irregular RR intervals with absent P waves and fibrillatory baseline; rate control is assessed by the ventricular response.

Atrial flutter: regular sawtooth flutter waves at about 300/min with a fixed or variable block, commonly 2:1 giving a ventricular rate near 150/min.

AV block: first degree is PR over 0.20 s; second degree Mobitz I (Wenckebach) shows progressive PR prolongation before a dropped beat; Mobitz II shows constant PR with dropped beats; third degree shows complete AV dissociation with P and QRS independent.

Ventricular arrhythmias: premature ventricular complexes are broad (over 0.12 s) and bizarre with no preceding P wave; ventricular tachycardia is three or more consecutive PVCs at over 100/min; ventricular fibrillation is chaotic with no identifiable complexes and requires immediate defibrillation.

Supraventricular tachycardia is regular, narrow-complex and fast, often with hidden P waves; sinus tachycardia is distinguished by visible normal P waves.

Bundle branch block: right bundle branch block gives rSR in V1 and wide slurred S in V6; left bundle branch block gives broad notched R in V5-V6 and deep S in V1, with QRS over 0.12 s.

Ectopic beats: atrial premature beats have an early abnormal P wave and a narrow QRS; the pause after a PVC is usually fully compensatory.

Ischaemia sequence: hyperacute tall T waves, then ST elevation, then Q wave formation, then T wave inversion as infarction evolves.

ST elevation myocardial infarction is localised by lead groups: inferior in II, III and aVF; anterior in V1-V4; lateral in I, aVL, V5 and V6; posterior shows ST depression in V1-V3 with tall R waves.

Reciprocal changes support the diagnosis: inferior ST elevation is usually accompanied by ST depression in I and aVL, and anterior elevation by reciprocal depression inferiorly.

ST depression that is horizontal or downsloping suggests ischaemia; upsloping ST depression during exercise may be normal.

NSTEMI and unstable angina show ST depression or T inversion without persistent ST elevation; cardiac troponin distinguishes infarction from ischaemia.

Hyperkalaemia: tall peaked T waves, flattened P waves, widened QRS and eventually a sine wave pattern. Hypokalaemia: flat T waves, prominent U waves and ST depression.

Pericarditis: widespread concave ST elevation and PR depression across many leads without reciprocal changes, in contrast to the territorial pattern of infarction.

Pulmonary embolism: sinus tachycardia, S wave in lead I, Q wave and inverted T in lead III, and right heart strain with T inversion in V1-V4; left ventricular hypertrophy shows deep S in V1 plus tall R in V5 or V6 exceeding 35 mm.

Common conditions seen in ECG practice: hypertension, coronary artery disease, rheumatic valvular disease, cardiomyopathies, congenital heart disease, and arrhythmias such as atrial fibrillation.

Heart failure signs: dyspnoea, orthopnoea, basal crackles, raised jugular venous pressure and pedal oedema; position the patient upright if breathless during recording.

Emergency response: for a collapsed patient check response and breathing, call for help, start chest compressions at 100-120/min with a depth of 5-6 cm, and use an AED as soon as available.

Electrical safety: never connect a patient to a machine with a damaged cable; keep the ECG machine on a properly earthed circuit and avoid contact between the patient and metal furniture.

Standard precautions: hand hygiene is the single most effective measure; use gloves when contacting blood or body fluids, and follow sharps safety for any procedure involving needles.

Biomedical waste segregation: yellow bag for human anatomical waste and soiled items, red for contaminated recyclable plastics, and puncture-proof white translucent container for sharps.

Patient rights and ethics: informed consent, confidentiality, dignity and privacy; the technician must not disclose patient information and must record only what is measured.

Scope of practice: the ECG technician records and may report technical artefacts, but interpretation and diagnosis remain the responsibility of the treating physician.