Basic Dysrhythmia InterpretationNURS 108Spring 2008

Majuvy L. Sulse RN, MSN,CCRN

Cardiac CycleSystole-simultaneous contraction of ventricles, lasts 0.28 secDiastole- ventricular relaxation, lasts 0.52 secOne cardiac cycle occurs every 0.8 sec

Cardiac CycleStroke volume-volume of blood (70cc) pumped out of one ventricle of the heart in a single contractionHeart rate- number of contractions per minute(60-100bpmCardiac output-amount of blood pumped by the left ventricle in 1 minute (4-8L/min)CO= SV XHR

Cardiac CyclePreload-degree of myocardial fiber stretch at the end of diastoleAfterload-resistance against which the heart must pump to eject blood through the semilunar valves and into peripheral vesselsSTARLINGS Law-the more the muscle fibers are stretched up to a certain point, the more forceful the subsequent contraction will be.Systemic vascular resistance (impedance)- amount of opposition to blood flow offered by the arterioles, pressure the heart must overcome to open the aortic valve

Autonomic Nervous SystemSympathetic-prepares for physical activity-fight or flight response-norepinephrine (Adrenergic nerve endings)Alpha-vasoconstrictionBetaBeta 1-increase HR & contractilityBeta 2-bronchial dilation & vasodilationParasympathetic-rest & digest functionAcetylcholine (cholinergic nerve endings)

Electrophysiologic PropertiesAutomaticity-ability to generate an electrical impulse spontaneously & repetitivelyExcitability-ability to be electrically stimulated or respond to an electrical stimulusConductivity-ability to receive an electrical stimulus and transmit to other cardiac cellsContractility-also rhythmicity is the ability to shorten and cause contraction in response to an electrical stimulus-coordination of contraction to produce a regular heartbeat

Major electrolytes that affect Cardiac Function3 major cationsK-performs a major function in cardiac depolarization and repolarizationSodium plays a vital part in myocardial depolarizationCalcium is important in myocardial depolarization and contraction.Magnesium-acts as transporter for Na & K across cellular membranes. Also plays an important function in muscular contraction

Movement of IonsResting cardiac cells (Polarization) inside the cell is negatively charged. K is greater in the cell; Na greater outside the cell (positively charged)-Resting membrane potentialDepolarization (action Potential)-sodium-potassium exchanged pump resulting in positive polarity inside the cell membrane. Myocardial contraction occurs.Repolarization-recovery or resting phase; positive charges are again on the outside and negative charges in the inside

Refractory PeriodsEnsures that the muscle is totally relaxed before another action potential occursAtrial muscle-0.15 secVentricular muscle-.25-.30 sec

Refractory PeriodsAbsolute refractory period-cardiac muscle cannot be depolarized. Corresponds to beginning of QRS to peak of T waveRelative refractory period-cardiac muscles stimulated to contract prematurely if stimulus is stronger than normal. Corresponds with down slope of T wave

Cardiac Conduction System

Electrical Conduction PathwaySA node (60-100bpm) Internodal pathways AV node ( 40-60bpm) Bundle of His Bundle Branches Purkenje networks (20-40bpm)

EKG ECG/EKG-a graphic representation of cardiac activity12 lead-shows electrical activity from 12 different planes of the heart-used as a diagnostic tool rather than a monitoring deviceElectrode-adhesive pad that contains conductive gel and designed to be attached to skinLeads-wires generally color coded. For the EKG to receive a clear picture of electrical impulses, there must be a positive, a negative and a ground. The exact portion of the heart being visualized depends on lead placement

EKG LeadsBaseline-isoelectric line-no current flow in the heart; consists of positive, negative deflections or biphasic complex3 or 5 lead- used for monitoring the current cardiac activity of patients at risk for cardiac abnormalitiesLead ll or MCL1-modified chest leads mostly used because of ability to visualize P waves. MCL provides a R sided view of the heart. MCL6-L sided view of the heart

EKG LeadsLimb leadsBipolar leads-measures activity between 2 points (I, II, III)Unipolar leads-positive electrodes only-aVR, aVL, aVFChest leads-6 precordial leads

LIMB LEADS & AUGMENTED LEADS

EKG Graph Paper

Segments and Intervals

Segments and IntervalsP wave-deflection representing atrial depolarizationPR segment-isoelectric line from end of P wave to beginning of QRS-impulse is traveling through the AV node. PR interval-0.12-0.20(time for atrial depolarization-AV node-Purkenje fibers) QRS complex-ventricular depolarization. QRS duration of 0.04-.10 sec from QRS to J-pointST segment-early ventricular repolarization from J-point to beginning of T wave. Elevations not more than 1 mm or deflections o.5 mm from isoelectric lineT wave- ventricular repolarization, usually rounded, positive deflection U wave-smaller polarity as T wave-slow repolarization- not normally seen except in hypokalemiaQT interval-total time for ventricular depolarization and repolarization

HR Determination6 second method count QRS complexes in a 6 sec strip x 10 (30 large boxes in 6 sec strip) P-P or R-R interval methodcount number of small blocks in a P- P or R-R interval and divide into 1500 (no. of small blocks in 1 min)Count the number of large blocks in an interval and divide into 300 (number of large blocks in 1 minute)Memory method

ECG Rhythm AnalysisAnalyze P waves- P wave is present. shape is consistent, must be before each QRSAnalyze QRS complex- QRS complex is present & consistentDetermine atrial rhythm or regularity- check regularity by assessing P-P or R-RDetermine ventricular rhythm or regularity-check regularity by assessing R-RDetermine heart rate-use one of the methodsMeasure the PR interval-measurement should be constant and should be between 0.12-0.20Measure the QRS duration-measurement should be constant and should be between 0.04-0.10 secInterpret the rhythm

General RulesFirst & most important, LOOK at your PATIENT!Read every strip from left to rightApply the systematic approach Avoid shortcuts and assumptions.Ask and answer each question in the ECG analysis approach

ArtifactsWaveforms outside the heart-interference caused by:Patient movement wandering baselineLoose or defective electrodes-lost contact with patients skinImproper grounding-in touch with an outside source of electricityFaulty EKG apparatus

Normal Sinus RhythmSA node generated an impulse that followed a normal pathway, the heart rate falls within the range, atrial & ventricular rhythms are regular, P waves preceded every QRS and QRS is within 0.12sec

Sinus BradycardiaSA node fires slower than normal heart rate-less than 60bpmRhythm is regularP wave upright and same shapePR is constant .12-.20secQRS-normal

Sinus BradycardiaCauses:Vagal stimulation, MI, hypoxiaDigitalis toxicityMedication side effectsNormal to athletesAdverse effects:Dizziness, weakness, syncope, diaphoresis, pallor, hypotensionTreatmentAccording to symptoms, atropine to speed up heart rate, pacemaker

Sinus TachycardiaSA node fires at a rate faster than normal but conduction pathway is normal. All criteria for interpretation are the same except that the heart rate is faster.

Sinus TachycardiaCausesEmotionally upset, pain, fever, thyrotoxicosis, hypoxia, hypovolemia, inhibition of vagus nerve,Caffeine, norepinephrine, theophyllineAdverse effectsAngina, dizziness, hypotension, increased in cardiac workloadTreatmentTreat the causeMedications may be given- betablockers

Sinus ArrhythmiaThe only irregular rhythm from the sinus node and has a cyclic pattern that usually corresponds with breathingRate- varies with respiratory patternRegularity-irregular in a repetitive patternP waves-Upright in most leads, same shape and one to each QRS P-P interval is irregularQRS-

Atrial DysrhythmiasSA node fails to generate an impulseAtrial nodes or internodal pathways may initiate an impulse and follows the conduction pathwayDysrhythmias of this type are not lethal Accessory pathway-irregular muscle connection between atria and ventricles that bypasses the AV node

Premature Atrial ContractionsCauses- atria becomes hyper and fire early caused by medications, caffeine, tobacco, hypoxia or heart diseaseAdverse effects-if frequent can be a sign of impending heart failure or atrial tachycardia or fibrillationTreatment-O2, omit caffeine, tobacco or other stimulants. Give digitalis or quinidine, treat heart failure.

Premature Atrial ContractionsRatenormalRhythmusually regular except for a PACP wavesshaped differently from a normal P wave or hidden in preceding T wavePR interval.12 to .20secQRS.12sec similar to underlying rhythm

Supraventricular Tachycardia (SVT)Tachycardia (>150 bpm) originating above the ventricles-SA node, atria, AV nodesP waves not discernible-hidden in T wavesParoxysmal-starts & ends abruptlyCauses-same as PAcsAdverse effects- palpitations, light-headedness, dizziness, shortness of breath, chest pain, fainting =decreased cardiac output Treatment-vagal maneuvers (cough, bear down), carotid massage, or medications digitalis, calcium channel blockers, beta blockers, Adenosine

Supraventricular Tachycardia (SVT)Rate150-250bpmRhythmregularP wavesnot discerniblePR not discernibleQRSusually less than .10sec

Atrial FlutterResults when one irritable atrial foci fires out regular impulses at a rapid rate that P waves are in a sawtooth patternAv node (gatekeepers) cannot depolarize fast enough to keep up, many impulses never get through to ventricles. Conduction ratio is variable-2:1block, 3:1 block or 4:1 block. Slow ventricular response-VR of 100-150bpm)Causes-acute MI, CHF, digitalis toxicity, pulmonary embolism, SA node disease, septal defectsAdverse effects-decreased cardiac outputTreatment-digitalis, cardioversion, calcium channel blockers, ablation

Atrial FlutterRateatrial 250-300bpm, ventricles-variableRhythmregular if conduction ratio is constant, irregular if conduction rate variesP wavesreplaced by fluttery wavesPRnot measurableQRS

Atrial FibrillationMost common atrial dysrhythmia in elderly patientsMultiple atrial impulses from different locations all at the same time (350-600bpm)Ventricular response maybe rapid (100-150bpm) or slow (< 60bpm)Causes-maybe chronic MI CHF, valvular heart disease, hyperthyroidismAdverse effects-decreased cardiac output, blood clots which can cause MI, stroke or clot in the lungTreatment- Digitalis, quinidine, cardizem, anticoagulant as coumadin, cardioversion

Atrial Fibrillation

Junctional RhythmsArrhythmia originating in AV nodeHR= 40-60bpm; accelerated =60-100bpm; junctional= 100-140bpmP wave-absent, inverted before or after a QRSPR interval-

Junctional Rhythms

Ventricular DysrhythmiasVentricles serves as pacemakerHeart rate significantly reduced (20-40 beats per minNormal conduction system bypassedQRS bizarre in appearance & >0.12 secP waves absent (buried or hidden in QRS)Rhythms considered life threatening

Premature Ventricular Complexes (PVCs)A single ectopic (out of place) complex from an irritable siteIndicates increased myocardial irritabilityPrecursors of more serious lethal rhythmsCardiac output compromisedCausesMyocardial ischemia, Emotional stress, increased physical exertion, CHF, electrolyte imbalance, digitalis toxicity or acid base imbalancesTreatment- based on symptoms and causative factorsO2 and antidysrhythmics

PVCsUnifocal-arise from one single siteMultifocal- originate from different sitesVentricular bigeminy- every other beat is a PVCVentricular trigeminy-every third beat is a PVCVentricular quadrigeminy- every 4th beat is a PVCInterpolated- a PVC between two sinus beatsCouplet or repititive PVCs- two PVCs occurring together without a normal complex in between Salvos-3 or more PVCs in a row (Vtach)

Premature Ventricular Contraction (PVC)Multifocal PVCsUnifocal PVCs

Premature Ventricular Contraction (PVCNSR with CoupletsBigeminy

Ventricular Tachycardia3 or more PVCs in a row overriding pacemakerSustained-lasts more than 30 secUnsustained- less than 30 secCan be tolerated for short bursts but can cause profound shock if unconscious or untreatedCauses- as with PVCsTreatmentPulseless Vtach-treated like VfibStable-drug interventionLidocaine, procainamide, amiodaroneUnstable- defibrillation

Ventricular TachycardiaRate 100-25bpmRegularity usually regularP waves none PR will vary if presentQRS wide & bizarre >0.12

Ventricular Fibrillation (VFib)Fatal, most common initial rhythm in cardiac arrestMyocardial cells quiver rather than depolarizedUsually coarse (amplitude > 3mm) then becomes fine (amplitude less than 3mm)No cardiac output- cardiovascular collapseCauses- MI, drug toxicity or overdose, hypoxia, CADTreatment- immediate defibrillation must be done, CPR, epinephrine (medications make defibrillations more successful and prevent recurrence

Ventricular Fibrillation (VFib)Ratecannot be countedRegularityrapid, not detectableP wavesnoneQRSnone detectable

AsystoleCardiac standstillAbsence of all ventricular activity-no waveformsCheck on 2 leads-? Very fine VfibClinical death-absence of pulse and respirationsCauses- MI, cardiac trauma, ventricular aneurysm, CHBTreatment-atropine to reverse vagal influences, epinephrine, CPR, pacemaker, dopamine, O2

Ventricular AsystoleRatezeroRegularitynoneP wavesnoneQRSnone

Atrioventricular BlocksImpulses in the SA node are blocked or delayed-heart blocks- (PR >.20, some Ps not followed by QRS; some P-P with regular interval Underlying rhythm is sinusRate normal or slow-symptomatic or asymptomaticSite of block is either AV node or bundle branchesFirst dgreeSecond degreeType l-Mobitz lType ll- Mobitz 2Third degree

First degree AV blockProlonged PR interval that results from a delay in the AV nodes conduction of sinus impulse to ventriclesAll parameters are normal except for prolonged PR interval (hallmark of 1st degree)Usually asymptomaticCauses-AV node ischemia, digitalis toxicity, use of betablockers or calcium blockersTreatment- treat cause

First Degree AV BlockRatebased on underlying rhythmRegularityusually regularP wavesupright, one to each QRSPR interval> .20 secQRS

Second Degree Block (Mobitz l (WenckebachProgressive prolongation of the impulseCyclic pattern is produced: PR interval continues to increase in length until an impulse is not conducted (QRS dropped)Atrial rhythm is regular but ventricles ar irregularCause-MI, digitalis toxicity, n\medication effectsTreatment-atropine if heart rate is slow & asymptomatic, pacemaker.

Second Degree Block (Mobitz l (Wenckebach)Rate-Atrial rate normal: ventricular rate less than atriaRegularity-maybe regular or irregularP waves-normal P; PR interval progressive prolongationQRS= if block is at bundle branch

Second Degree Block-Mobitz llIncreased risk of progression to 3rd degreeRatio of P waves to QRS complexes (2:1 block, 3:1 block or 4:1 block)PR interval is constant or regular for every conducted beat Intermittent absence of QRSCauses-same as type lTreatment-02, atropine if patient is symptomatic, epinephrine, dopamine, pacemaker if block continues and symptoms are present

Second Degree Block-Mobitz llRate =atrial 60-100: ventricular half of atrial rateRegularity=regularP waves= NormalPR interval= constantQRS= .12 sec if BBB present

Third Degree or Complete Heart Block (CHB)SA node sends out impulses as usual but not one is conducted to the ventriclesAtria & ventricles beat independently of each other-AV dissociationRate- atria-60-100, Ventricles-20-60 Regularity-RegularP waves- no relationship with QRSPR interval- no pattern, variesQRS-based on site of pacemakerCause-MI, lesion on conduction system, hypoxia, medication side effectsTreatment-pacemaker insertion

Third Degree or Complete Heart Block (CHB)

PACEMAKERS

PACEMAKERSDevice that substitutes for the normal pacemaker of the hearts electrical conduction systemGenerator-controls rate & strength of each electrical impulseLead wires-electrode at the tip relay the electrical impulse from the generator to the myocardiumTypesTemporary-used to sustain HR in an emergency situationTranscutaneous (TCP)-external cardiac pacing Transvenous-lead wire threaded through the skin into a large veinPermanent- implanted in patients chest

Indications for insertion of PacemakersTemporarySuppression of ectopic atrial or ventricular rhythmAcute MI with symptomatic bradycardia, 2nd & 3rd degree AV block or bundle branch blockMaintenance of adequate HR during special procedures or as prophylaxis after an open heart surgeryTermination of AV nodal reentryPermanent-Chronic atrial fibrillation with slow ventricular responseFibrotic or sclerotic changes in the cardiac conduction systemSick sinus syndrome or Sinus node dysfunctionTachyarrhythmiasSymptomatic bradycardia and Third degree AV block not responding to pharmacologic interventions

Permanent PacemakersAtrial- lead wire inserted into the Right atrium-stimulates the atrium then travels down the electrical conduction through the ventricles

Permanent PacemakersVentricular- lead wire inserted into the Right ventricle. The electrical impulse from the pacemaker generator produces ventricular depolarization

Permanent PacemakersAV sequential- two electrodes on the lead wire one placed on the R atrium & one on the R ventricle. Artificial impulses stimulate or pace first the atria, then the ventricles

Rules for interpretation of Pacemaker RhythmsSame as for dysrhythmiasRemember: Properly functioning pacemakers will produce rhythms with pacemaker spikes. Spikes indicates only that the pacemaker is firing. They do not reveal information relative to ventricular contraction. Assess your patient for presence of symptoms

Code System1st letter-chamber being pacedA-atrium V-ventricleD-dual (both)2nd letter- chamber sensedA-atrium V-ventricleD-dual (bothO-off3rd letter- type of response by pacemaker to sensoryI-Inhibited (pacemaker will not function when the persons heart beatsO-noneT-triggeredD-dual

Code System4th letter- ability of generator to be programmedO-noneP-Simple programmabilityM-Multi programmabilityC-Telemetry abilityP-ability of rate to change with activity5th letter-ability of generator to defibrillateP-AntitachycardiaS-ShockD-antitachycardia processing & shockO-none

Common Problems associated with PacemakersBattery failureDecreased amplitude of pacemaker spike and a slowing pacemaker rateImmediate transport to the hospital depending on the patients symptoms or underlying rhythmRunaway PacemakersRapid rate of electrical impulse discharge resultsImmediate transport to a hospital

Failure to SenseFailure to sense -pacemaker fails to sense the patient's own intrinsic rhythm and generates a pacer spike in the intrinsic rhythm's own QRS, absolute or relative refractory period of the T wave. The ventricular capture following the pacer spike may or may not occur. This can cause lethal arrhythmia. Failure to sense can be caused when the sensitivity setting is too low.

Failure to SenseEKG Characteristics: Rate: It may be regular or irregular. Rhythm: It can be any intrinsic rhythm in which the pacemaker spike is in the QRS, absolute, or relative refractory period of the T wave. QRS complex: It is within the normal limits of the intrinsic rhythm.Nursing Intervention: Obtain the blood pressure, pulse, respiratory rate, O2 saturation and notify the MD. Closely observe for ventricular tachycardia caused by failure to sense.

Failure to Capture Failure to capture of a pacemaker happens when the output is too low, resulting in a failure to depolarize the ventricle, which causes an absence of a mechanical contraction of the ventricle, or no QRS. It can occasionally happen or be constantly happening which results in ventricular standstill and a pulse-less patient.EKG Characteristics: Rate: It will be irregular due to the failure to produce QRS. Rhythm: The pacemaker spike or spikes will not have a QRS following them. P Wave: It may be absent or present. QRS Complex: A loss of a QRS behind a pacer spike.

Failure to CaptureNursing Intervention: Should the loss to capture be occasional, one should get a blood pressure, pulse rate, respiration rate, and O2 saturation. This is to determine if the patient is tolerating the failure to capture. If the failure to capture is continuous, the patient will be pulse-less or have a symptomatic bradycardia. This can range from a situation in which medication may be needed, or a code situation in which one would follow hospital protocol. External pacing may be an option for this patient

Pre-procedure & Post procedure careConsentVSSkin prepPre-op checklist-NPO, dentures, pinsPosition post op is importantMaintain hemodynamic stabilityPrevent complications

Patient & family Teaching GuidesFollow the instructions for pacemaker site skin care. Report any fever or redness, swelling, or drainage from incision site. Keep your pacemaker identification card in your wallet and wear a medical alert braceletTake your pulse for 1 full minute at the same time each day and record the rate in your pacemaker diary. Take your pulse anytime you feel symptoms of a possible pacemaker failure and report them to your physician.

Patient & family Teaching GuidesKnow the rate at which your pacemaker is set and the basic functioning of your pacemaker, battery failure. Know what changes to report to your physician.Report any of the following symptoms to your physician: dizziness, difficulty of breathing, fainting, chest pain, weight gain, and prolong hiccupping. If you have any of these symptoms, check your pulse and call your physician.Take all medications, follow prescribed diet, activity restrictionsDo not apply pressure over the generator. Avoid tight clothing or belts.

Patient & family Teaching GuidesDo not operate electrical appliances over pacemaker as they may cause malfunction.Be sure electrical appliances or motors are properly grounded.Avoid all transmitter towers for radio, TV and radar. Radios, TV, & other home appliance and antennas do not pose a hazard. Inform airport personnel and show ID card before passing through the metal detector.

Automatic Implantable Cardioverter-DefibrillatorLead placed via the subclavian into the endocardiumGenerator is implanted subcutaneously over the pectoralis muscleMonitors HR/rhythm and identifies ventricular tachycardia & ventricular fibrillationDelivers a shock (25 joules) to the heart muscle upon sensing a lethal arrhythmiaSome newer ICDs are equipped with antitachycardia and antibradycardia pacers- initiates ovrdrivepacing to prevent painful shocks

Patient & Family teaching guide for AICDMaintain close follow up with physician for testing ICD function & inspection of siteMedic alert should be worn & information about the ICD should be availableWatch for signs of infectionAvoid lifting operative side arm above shoulder for about a weekAvoid direct blows to ICD site

Patient & Family teaching guide for AICDWhen traveling, inform airport official about presence of AICDWhen ICD firesRoutine checks with programmer device needed-2-3 monthsFamily members should learn CPRAvoid electromagnetic forces that may turn off deviceParticipate in ICD support groups

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