Cath Lab Technician Grade II — 2025 — Provisional Answer Key — Kerala PSC PYQ Practice with Answers

Correct answer (Option B):\nThe potential recorded by an ECG electrode is directly proportional to the cosine of the angle between the direction of activation spread and the line to the recording site (not indirectly proportional). Furthermore, it is inversely proportional to the square of the distance from the activation front to the recording front, rather than directly proportional. Therefore, statements C and D are completely false.\n\nWhy others are wrong:\nOption A incorrectly pairs true statements or includes correct ones. Option C and Option D do not capture the exact pair of false components as successfully as Option B does.\n\nStudy tip:\nRemember that bioelectric potentials follow inverse-square physical laws regarding distance. Review the core solid angle theorem of electrocardiography for exact proportional relationships.

Correct answer (Option C):\nWilson Central Terminal (WCT) serves as the negative central reference point (negative input) for unipolar ECG leads. It is calculated as the average or mean value of the potentials recorded from three specific limb electrodes: the Left Arm (LA), Left Leg (LL), and Right Arm (RA). This makes statements A and D true.\n\nWhy others are wrong:\nOption A incorrectly pairs statement C (which wrongly uses the right leg instead of the right arm). Option B presents WCT as a positive input, which is false. Option D incorrectly includes the right leg reference.\n\nStudy tip:\nWCT is formed by connecting the right arm, left arm, and left leg electrodes through equal electrical resistors to a common node, establishing a near-zero virtual reference point.

Correct answer (Option D):\nIn the augmented limb lead aVR, the positive input electrode is placed on the right arm, while the negative input is an average of the left arm and left leg potentials (not WCT, because the right arm is disconnected from the reference network to augment the signal). Thus, statements A, C, and D contain false assertions regarding this arrangement.\n\nWhy others are wrong:\nOptions A, B, and C fail to include all the incorrect structural claims presented among the choices. Option D perfectly collects the set of false sentences.\n\nStudy tip:\nAugmented leads (aVR, aVL, aVF) modify the standard Wilson reference by leaving out the exploring limb from the reference terminal, amplifying the final potential by approximately 50%.

Correct answer (Option A):\nThe PR interval accurately tracks the duration of atrioventricular conduction. It spans from the initiation of atrial depolarization at the sinoatrial node to the start of ventricular depolarization. It marks the transit timeframe across the AV junction, making statements B and D correct in their physiological interpretation.\n\nWhy others are wrong:\nOptions B and C incorrectly include definitions stating that the wavefront has fully traveled to the endocardium or epicardium at this interval, which describes the completion of the QRS complex, not the PR interval baseline.\n\nStudy tip:\nThe normal PR interval ranges between 0.12 to 0.20 seconds. Delays here are indicative of first-degree atrioventricular blocks.

Correct answer (Option A):\nThe U wave is historically attributed to delayed repolarization (not depolarization) of the Purkinje fibers or mid-myocardial cells, or mechanical forces during early diastole. Additionally, its typical normal amplitude is under 0.1 to 0.15 mV (not Volts, which would be massive). This makes options A, B, and C contain structural flaws.\n\nWhy others are wrong:\nOptions B, C, and D are incorrect groupings because they do not collect the complete set of false theoretical assertions identified by Option A.\n\nStudy tip:\nProminent U waves are classically observed in conditions like severe hypokalemia, digitalis toxicity, and hypercalcemia.