Questions and Answers 2025/2026
Graded A+.
Cardiac Conduction Pathway System
SA node> AV node> Bundle of His> Left and Right package branches> Purkinjie fibers Pacemakers of the
heart
Interatrial/Internodal Tracts
Transmits impulses from the SA node to the AV node via the RA & LA
AV node
• Slows conduction (40-60 beats/min)
• Physiologic delay permits atrial kick on ground of RA near tricuspid valve
Bundle of His
Bundle of cardiac muscle fibers that conducts the electrical impulses from the AV node inside the right
atrium to the septum between the ventricles and then to the left and right ventricles.
Depolarization vs Repolarization
Depolarization – electrical excitation of the mobile membrane, typically followed by way of mechanical
contraction
♥ Natural: SA Node = 60-one hundred beats/minute
♥ Backup: AV Node = 40-60 beats/minute
♥ Backup: Purkinje Fibers (ventricles) = 20-forty beats/minute
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SA Node
• Intrinsic Pacemaker of the coronary heart
• Rate 60-one hundred beats/min
• RA (Right Atrium), near SVC (Superior Vena Cava)
• Blood supply from RCA (Right Coronary Artery) & LCA (Left Coronary Artery)
• Package branches
• Right and Left (Left anterior & Left posterior fascicles)
• Purkinjie Fibers
• Fibers from Bundle Branches imbedded into the ventricle walls.
•
Repolarization – return of cell membrane to its resting nation, usually accompanied by mechanical
relaxation
Electrical and mechanical pastime of the coronary heart
♥ The coronary heart has sports which can be completed rhythmically: electrical pastime observed by means
of mechanical pastime
♥ Electrical hobby constantly precedes mechanical interest
♥ It is feasible to have electrical activity with out mechanical response ♥
Always test the patient - Do Not Depend at the Machine!!!
♥ Voltage is measured alongside the vertical axis and is expressed in millivolts (mV). The general
calibration is that a 1 mV signal produces a ten-mm deflection (zero.1 mV=1mm). Simply positioned 10
small squares vertically is equal to 1 millivolt
EKG waveforms and durations
♥ P wave – rounded with upright deflection in lead II, atrial depolarization
, ♥ PR c language- delay @ AV junction
• degree from beginning of P wave to beginning of QRS
• Normal length zero.12 – 0.20 seconds •
S wave – Negative deflection following the R-wave
♥ QRS complex – a couple of additives, Ventricular depolarization, - zero.06 –0.11
• Q wave – first bad deflection after P wave R wave
• Positive deflection after the Q
• Measurement of the containers within the ekg
• ♥ A preferred ECG is outlined at 25mm in keeping with 2d or 25 small squares according to 2d.
Since one 2d divided by means of 25 small containers, then every 1 mm container = zero.04 seconds. The
large containers indicated through the heavier traces are equal to zero.20 seconds.
•
♥ J factor - marks in which the QRS complex ends and the ST segment begins
♥ ST section – typically isoelectric line between QRS and the start of the T wave
♥ QT c program languageperiod – beginning of the QRS complex to the stop of the T wave; changes with
heart price, typically 1/2 of the R to R c program languageperiod. Starting of vent activation via Ventricular
depolarization. Zero.44 –zero.48 (Rate dependent)
♥ T wave - follows the QRS; normally, large than the P wave and barely asymmetric; Ventricular
repolarization
♥ U wave – now not typically visible, can be due to hypokalemia or digitalis toxicity Isoelectric Line
–No perceived electric modern-day
indication of a flat line at any time within the duration of a series of waves indicates no
electric activity at that precise moment
♥ Get a 12 lead ECG for any rhythm modifications.
♥ Get a set of essential signs and symptoms for any rhythm changes.