Unit 1: Cardiac Anatomy and Physiology

• Topic 01

  Heart Anatomy — Chambers, Walls, and Valves

  15 questions
• Topic 02

  The Pericardium, Myocardium, and Endocardium

  15 questions
• Topic 03

  Coronary Arteries — LAD, RCA, and Circumflex

  15 questions
• Topic 04

  Cardiac Conduction System — SA Node, AV Node, Bundle of His, Purkinje Fibres

  15 questions
• Topic 05

  Cardiac Cycle — Systole, Diastole, and Stroke Volume

  15 questions
• Topic 06

  Cardiac Output, Heart Rate, and Blood Pressure Relationships

  15 questions
• Topic 07

  Common Cardiac Conditions — Angina, MI, Heart Failure, Hypertension

  15 questions

A few questions from this unit, with the answer and a full explanation. The complete bank is available when you start practising.

1. An EKG technician is about to acquire an ECG on a resting patient whose blood pressure reads 78/48 mmHg and heart rate is 128 bpm. The patient reports light-headedness and the skin is diaphoretic. What action should the technician take, and why do these vital signs indicate haemodynamic compromise?

   • A
     The technician should administer supplemental oxygen and reposition the patient before alerting staff, as these measures may normalise the vital signs
   • B
     The technician should note the abnormal vital signs in the tracing annotation and leave the clinical decision to the reviewing physician
   • C
     The technician should immediately alert the supervising clinician before proceeding; MAP is approximately 58 mmHg (below the 65 mmHg threshold), and combined tachycardia with hypotension suggests shock requiring urgent clinical evaluation
     Correct answer
   • D
     The technician should proceed with the ECG as quickly as possible, as obtaining the tracing is the immediate clinical priority and nothing else should delay it
   Explanation

   MAP = 48 + 1/3(30) = 48 + 10 = 58 mmHg, which is below the critical threshold of 65 mmHg used in clinical guidelines to define haemodynamically significant hypotension. Combined with tachycardia (compensatory heart rate increase) and diaphoresis (sympathetic activation), this presentation is consistent with shock. The EKG technician's professional responsibility includes recognising signs of haemodynamic compromise and escalating to clinical staff before or immediately after acquiring a tracing. The Joint Commission's standards and the NHA CET scope of practice both require technicians to alert clinical staff under these circumstances. Key takeaway: EKG technicians must recognise haemodynamic compromise (MAP <65, tachycardia, diaphoresis) and escalate immediately — not diagnose, but alert.

2. What is the cardiac cycle?

   • A
     The period from the P wave to the end of the T wave on an ECG
   • B
     One complete sequence of contraction (systole) and relaxation (diastole) of the heart
     Correct answer
   • C
     The volume of blood pumped by the heart each minute
   • D
     The time taken for a single ventricular contraction only
   Explanation

   The cardiac cycle encompasses all electrical and mechanical events from the beginning of one heartbeat to the beginning of the next. It consists of systole (ventricular contraction and ejection) and diastole (ventricular relaxation and filling). At a resting heart rate of 75 bpm, one complete cycle lasts approximately 0.8 seconds. Key takeaway: the cardiac cycle = one complete contraction + relaxation sequence, lasting ~0.8 s at rest.

3. A technician places electrodes and sees negative P waves in leads II and aVF but positive P waves in aVR. The QRS complexes are narrow. What does this P-wave morphology suggest about the origin of the pacemaker?

   • A
     The patient has dextrocardia, causing reversal of all waveform polarities
   • B
     The impulse originates in the SA node but is conducted via an accessory pathway
   • C
     The impulse originates in the right ventricle and conducts retrogradely through the AV node
   • D
     The impulse originates low in the atria or AV junction, producing retrograde (bottom-to-top) atrial activation
     Correct answer
   Explanation

   Normal SA node activation spreads from right atrium (superior) to left atrium (inferior), producing upright P waves in the inferior leads (II, III, aVF). When an ectopic focus fires from the lower atria or AV junction, the activation wavefront travels in the opposite direction (retrograde, inferior to superior), generating inverted P waves in leads II and aVF and an upright P in aVR. Narrow QRS confirms that ventricular conduction is via the normal His-Purkinje system. Key takeaway: inverted P waves in inferior leads indicate a non-sinus (low atrial or junctional) pacemaker origin.