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EKG Kaiser Study Guide Exam With Questions And 100% Correct Answers
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EKG Kaiser Study Guide Exam With Questions And100% Correct Answers
Cardiac Conduction Pathway System
SA node> AV node> Bundle of His> Left and Right bundle branches> Purkinjie fibers
Pacemakers of the heart
♥ Natural: SA Node = 60-100 beats/minute
♥ Backup: AV Node = 40-60 beats/minute
♥ Backup: Purkinje Fibers (ventricles) = 20-40 beats/minute
SA Node
• Intrinsic Pacemaker of the heart
• Rate 60-100 beats/min
• RA (Right Atrium), close to SVC (Superior Vena Cava)
• Blood supply from RCA (Right Coronary Artery) & LCA (Left Coronary Artery)
Interatrial/Internodal Tracts
Transmits impulse from the SA node to the AV node through the RA & LA
AV node
• Slows conduction (40-60 beats/min)
• Physiologic delay allows atrial kick on floor of RA near tricuspid valve
Bundle of His
Bundle of cardiac muscle fibers that conducts the electrical impulses from the AV node
in the right atrium to the septum between the ventricles and then to the left and right
,ventricles.
bundle branches
Right and Left (Left anterior & Left posterior fascicles)
Purkinjie Fibers
Fibers from Bundle Branches imbedded into the ventricle walls.
Depolarization vs Repolarization
Depolarization – electrical excitation of the cell membrane, normally followed by
mechanical contraction
Repolarization – return of cell membrane to its resting state, normally followed by
mechanical relaxation
Electrical and mechanical activity of the heart
♥ The heart has two activities that are performed rhythmically: electrical activity
followed by mechanical activity
♥ Electrical activity always precedes mechanical activity
♥ It is possible to have electrical activity without mechanical response
♥ Always check the patient - Do Not Depend on the Machine!!!
Measurement of the boxes in the ekg
♥ A normal ECG is printed at a rate of 25mm per second or 25 small squares per second.
Since one second divided by 25 small boxes, then each 1 mm box = 0.04 seconds. The
larger boxes indicated by the heavier lines are equal to 0.20 seconds.
Voltage is measured along the vertical axis and is expressed in millivolts (mV). The
standard calibration is that a 1 mV signal produces a 10-mm deflection (0.1 mV=1mm).
Simply stated, putting 10 small squares vertically equals 1 millivolt EKG waveforms and
intervals P wave - rounded with upright deflection in lead II, atrial depolarization PR
interval- delay @ AV junction
,• Measure from beginning of P wave to beginning of QRS
• Normal duration 0.12 – 0.20 seconds •
S wave – Negative deflection following the R-wave
♥ QRS complex – multiple components, Ventricular depolarization, - 0.06 –0.11
• Q wave – first negative deflection after P wave R wave
• Positive deflection after the Q
♥ J point - marks where the QRS complex ends and the ST segment begins
♥ ST segment -normally isoelectric line between QRS and the beginning of the T wave
♥ QT interval -beginning of the QRS complex to the end of the T wave; changes with
heart rate, usually half of the R to R interval. beginning of vent activation through
Ventricular depolarization. 0.44 –0.48 (Rate dependent)
♥ T wave - after the QRS; usually, larger than the P wave and slightly asymmetrical;
Ventricular repolarization
♥ U wave – not typically seen, may be associated with hypokalemia or digitalis toxicity
Isoelectric Line –No visible electrical activity
, indentation of a base line at any time in the duration of a series of waves
implies no electrical activity during that particular point in time
Nursing Responsibilities when there's alteration in ECG rhythm
♥ Print, measure, interpret and post rhythm strips per unit standard.
♥ Obtain a 12 lead ECG for any rhythm changes
♥ Obtain a set of vital signs for any rhythm changes
♥ Know your unit standards and when to notify the MD.
Why is normal conduction and heart rate important?
critical for adequate filling & optimum cardiac output (CO)
Mechanism of dysrhythmias: Altered Automaticity
change in rate of pacer cells; sympathetic vs. parasympathetic
Dysrhythmias Mechanism: Abnormal Automaticity
non-pacer cells fire spontaneously due to:
• injury/ ischemia, hypoxia,
• stretch w/ volume overload
• hypokalemia hypomagnesaemia
Mechanisms of Dysrhythmias: Altered Conductivity
blocks in normal conduction
• fibrotic changes, valvular disease, acute ischemia
Mechanisms of Dysrhythmias: Re-entry
a single impulse can depolarize the same tissue more than once
Dysrhythmias Consequences
♥ Decrease HR →decreased CO
♥ Increased HR →decreased CO
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