Coronary Artery Disease Coronary Artery Disease Complications Complications Cardiac Cardiac Arrhythmias/Dysrhythmias Arrhythmias/Dysrhythmias Conduction System Conduction System Four Properties of Cardiac Tissue Four Properties of Cardiac Tissue Automaticity Automaticity – ability to initiate an – ability to initiate an impulse impulse Contractility Contractility – ability to respond – ability to respond mechanically to an impulse mechanically to an impulse Conductivit Conductivit y – ability to transmit an y – ability to transmit an impulse along a membrane in an orderly impulse along a membrane in an orderly manner manner Excitability Excitability – ability to be – ability to be electrically stimulated electrically stimulated
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Coronary Artery Disease Complications Cardiac Arrhythmias/Dysrhythmias Conduction System Four Properties of Cardiac Tissue Automaticity – ability.
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Four Properties of Cardiac TissueFour Properties of Cardiac Tissue AutomaticityAutomaticity – ability to initiate an impulse – ability to initiate an impulse ContractilityContractility – ability to respond – ability to respond
mechanically to an impulsemechanically to an impulse ConductivitConductivity – ability to transmit an y – ability to transmit an
impulse along a membrane in an orderly impulse along a membrane in an orderly mannermanner
ExcitabilityExcitability – ability to be electrically – ability to be electrically stimulatedstimulated
Calculating Heart RateCalculating Heart Rate EKG paper is a grid where time is measured along the horizontal axis. EKG paper is a grid where time is measured along the horizontal axis. Each small square is 1 mm in length and represents 0.04 seconds. Each small square is 1 mm in length and represents 0.04 seconds. Each larger square is 5 mm in length and represents 0.2 seconds. Each larger square is 5 mm in length and represents 0.2 seconds. Voltage is measured along the vertical axis - 10 mm is equal to 1mV in voltage. Voltage is measured along the vertical axis - 10 mm is equal to 1mV in voltage. Heart rate can be easily calculated from the EKG strip:Heart rate can be easily calculated from the EKG strip: Heart rate can be easily calculated from the EKG strip:Heart rate can be easily calculated from the EKG strip:
• When the rhythm is regular:When the rhythm is regular:
• the heart rate is 300 divided by the number of large squares between the QRS complexes.the heart rate is 300 divided by the number of large squares between the QRS complexes. • e.g., if there are 4 large squares between regular QRS complexes, the heart rate is 75 (300/4=75).e.g., if there are 4 large squares between regular QRS complexes, the heart rate is 75 (300/4=75).
• The second method can be used with an irregular rhythm to estimate the rate:The second method can be used with an irregular rhythm to estimate the rate:
• Count the number of R waves in a 6 second strip and multiply by 10. Count the number of R waves in a 6 second strip and multiply by 10.
• e.g., if there are 7 R waves in a 6 second strip, the heart rate is 70 (7x10=70).e.g., if there are 7 R waves in a 6 second strip, the heart rate is 70 (7x10=70).
AnalysisAnalysis Analyze the P waves – rate/rhythmAnalyze the P waves – rate/rhythm Analyze the QRS complexes – Analyze the QRS complexes –
rate/rhythmrate/rhythm Determine the heart rateDetermine the heart rate Measure the PR IntervalMeasure the PR Interval Measure the QRS durationMeasure the QRS duration Interpret the rhythm Interpret the rhythm Clinical significance? Hemodynamic Clinical significance? Hemodynamic
status?status? Appropriate TxAppropriate Tx
Cardiac Monitoring Cardiac Monitoring Normal Sinus RhythmNormal Sinus Rhythm
TxTx: If patient is symptomatic – raise legs : If patient is symptomatic – raise legs up, move patient, Atropine – ACLS up, move patient, Atropine – ACLS BradycardiaBradycardia
Most Common dysrhythmia in the USMost Common dysrhythmia in the US Multiple rapid impulses from many Multiple rapid impulses from many
atrial foci, rate of 350-600/min—atrial foci, rate of 350-600/min—depolarize the atrial in a disorganized depolarize the atrial in a disorganized and chaotic manner – atrial quiverand chaotic manner – atrial quiver
ResultsResults: : No P wavesNo P wavesNo atrial contractsNo atrial contractsNo atrial kick No atrial kick Irregular ventricular responseIrregular ventricular response
Early ventricular complexesEarly ventricular complexesFollowed by compensatory pauseFollowed by compensatory pauseFit between two NSR beats - interpolated Fit between two NSR beats - interpolated
Antiarrhythmics: amiodarone/lidocaineAntiarrhythmics: amiodarone/lidocaine Magnesium – torsades de pointesMagnesium – torsades de pointes
Advanced Cardiac Life SupportAdvanced Cardiac Life Support Defibrillation – V Fib / pulseless & polymorphic V tach Defibrillation – V Fib / pulseless & polymorphic V tach
Cardiac Monitoring Cardiac Monitoring Second Degree AV Block Second Degree AV Block
Mobitz Type I - Mobitz Type I - WenckebachWenckebach
Each impulse takes progressively longerEach impulse takes progressively longer Progressive lengthening of PR IntervalProgressive lengthening of PR Interval Followed by a dropped beat (missing QRS complex) & a Followed by a dropped beat (missing QRS complex) & a
pausepause May need temporary transvenous pacerMay need temporary transvenous pacer
Etiology: Etiology: Often transient following anterior / Often transient following anterior / inferior wall MI – may revert to 1inferior wall MI – may revert to 1stst Degree AV Block Degree AV Block
Cardiac Monitoring Cardiac Monitoring Second Degree AV Block Second Degree AV Block
Mobitz Type IIMobitz Type II
EtiologyEtiology: Infranodal block in one of the : Infranodal block in one of the bundle branchesbundle branches Dropped QRS complex without progressive Dropped QRS complex without progressive
lengthening of PR intervallengthening of PR interval P wave with no QRS complex followingP wave with no QRS complex following Random blockRandom block May progress to 3May progress to 3rdrd Degree AV Block – need for Degree AV Block – need for
Cardiac Monitoring Cardiac Monitoring Third Degree AV BlockThird Degree AV Block
No sinus impulses conduct to the ventriclesNo sinus impulses conduct to the ventricles AV dissociation – rate: 40/minAV dissociation – rate: 40/min PR interval not constant – no relationship with P PR interval not constant – no relationship with P
and QRS complexand QRS complex Ventricular pacemaker – may abruptly fail Ventricular pacemaker – may abruptly fail
Shockable Rhythm? No – BLS/CPRShockable Rhythm? No – BLS/CPR Epinephrine 1 mg IV (may repeat q3-5 Epinephrine 1 mg IV (may repeat q3-5
mins)mins)
(or one dose of Vasopressin)(or one dose of Vasopressin) AtropineAtropine 5 cycles of CPR5 cycles of CPR Shockable rhythm? NO - CPRShockable rhythm? NO - CPR Yes – Pulseless V FibYes – Pulseless V Fib
Cardiac DysrhythmiasCardiac Dysrhythmias
ASSESS THE PATIENTASSESS THE PATIENT Treat the underlying causeTreat the underlying cause Support hemodynamicallySupport hemodynamically