Dysrhythmias week 2
,Week 2: Dysrhythmias
• Dysrhythmias and arrythmias mean the same thing
• Abnormal cardiac rhythms are termed dysrhythmias.
• Prompt assessment of dysrhythmias and the client’s response to the rhythm is critical.
Properties of Cardiac Cells
• AUTOMATICITY-ability to initiate electrical impulses spontaneously and continuously (without
thinking about it- SA node working (primary pacemaker)
• EXCITABILITY- ability of cardiac cells to respond to electrical activity “electrically stimulated” (SA and
AV node)
• CONDUCTIVITY-ability of cardiac cells to transmit impulses to other areas
• CONTRACTILITY- ability to respond mechanically to electrical impulses with pump action
• REFACTORINESS- heart needs a break
Conduction System
• Automaticity: SA NODE 60-100 bpm: “primary pacemaker” (automatic firing rate exceeds heart’s
other pacemakers)
• AV NODE (junction) 40-70 bpm
• Purkinje fibers (ventricular conduction system) 20-40 bpm
Nervous System Control of the Heart
Autonomic nervous system controls:
• Rate of impulse formation
• Speed of conduction
• Strength of contraction
Parasympathetic nervous system:
• Vagus nerve: Job of the Vagus nerve is to SLOW down
• Decreases rate
• Slows impulse conduction
• Decreases force of contraction
Sympathetic nervous system:
• Increases rate
• Increases force of contraction
Electrocardiogram Monitoring
• Graphic tracing of electrical impulses produced by the heart
, • Waveforms of ECG represent activity of charged ions across membranes of myocardial cells
• Rhythm strip provides documentation of patient’s rhythm
• Allows for measurement of complexes and
intervals Phases of Cardiac Action Potential
Fig. 38-5. Time and voltage on the electrocardiogram; 6-second strip.
Assessment of Cardiac Rhythm (Above R)
• ECG paper consists of large (heavy lines) and small (light lines) squares.
• Each large square incorporates 25 smaller squares (five horizontal and five vertical).
• Each small square represents 0.04 second horizontally and 0.1 millivolt (mV) vertically.
• This means that the large square equals 0.20 second and that 300 large squares equal 1
minute. Vertically, one large square is equal to 0.5 mV.
Depolarization vs. Repolarization
• Repolarization/polarized = resting state = 60-100bpm
• When stimulated = depolarized
• Depolarization results in contraction
• Prepares for another impulse by recharging or repolarizing
• QRS=complex=several waves
• Isoelectric line=baseline
• Segments=straight line between wave and complex
• Interval=wave and segment
,Week 2: Dysrhythmias
• Dysrhythmias and arrythmias mean the same thing
• Abnormal cardiac rhythms are termed dysrhythmias.
• Prompt assessment of dysrhythmias and the client’s response to the rhythm is critical.
Properties of Cardiac Cells
• AUTOMATICITY-ability to initiate electrical impulses spontaneously and continuously (without
thinking about it- SA node working (primary pacemaker)
• EXCITABILITY- ability of cardiac cells to respond to electrical activity “electrically stimulated” (SA and
AV node)
• CONDUCTIVITY-ability of cardiac cells to transmit impulses to other areas
• CONTRACTILITY- ability to respond mechanically to electrical impulses with pump action
• REFACTORINESS- heart needs a break
Conduction System
• Automaticity: SA NODE 60-100 bpm: “primary pacemaker” (automatic firing rate exceeds heart’s
other pacemakers)
• AV NODE (junction) 40-70 bpm
• Purkinje fibers (ventricular conduction system) 20-40 bpm
Nervous System Control of the Heart
Autonomic nervous system controls:
• Rate of impulse formation
• Speed of conduction
• Strength of contraction
Parasympathetic nervous system:
• Vagus nerve: Job of the Vagus nerve is to SLOW down
• Decreases rate
• Slows impulse conduction
• Decreases force of contraction
Sympathetic nervous system:
• Increases rate
• Increases force of contraction
Electrocardiogram Monitoring
• Graphic tracing of electrical impulses produced by the heart
, • Waveforms of ECG represent activity of charged ions across membranes of myocardial cells
• Rhythm strip provides documentation of patient’s rhythm
• Allows for measurement of complexes and
intervals Phases of Cardiac Action Potential
Fig. 38-5. Time and voltage on the electrocardiogram; 6-second strip.
Assessment of Cardiac Rhythm (Above R)
• ECG paper consists of large (heavy lines) and small (light lines) squares.
• Each large square incorporates 25 smaller squares (five horizontal and five vertical).
• Each small square represents 0.04 second horizontally and 0.1 millivolt (mV) vertically.
• This means that the large square equals 0.20 second and that 300 large squares equal 1
minute. Vertically, one large square is equal to 0.5 mV.
Depolarization vs. Repolarization
• Repolarization/polarized = resting state = 60-100bpm
• When stimulated = depolarized
• Depolarization results in contraction
• Prepares for another impulse by recharging or repolarizing
• QRS=complex=several waves
• Isoelectric line=baseline
• Segments=straight line between wave and complex
• Interval=wave and segment
