Basic Dysrhythmia Interpretation NURS 108 Spring 2008 Majuvy

Basic Dysrhythmia Interpretation NURS 108 Spring 2008 Majuvy L. Sulse RN, MSN, CCRN

Cardiac Cycle n n n Systole-simultaneous contraction of ventricles, lasts 0. 28 sec Diastole- ventricular relaxation, lasts 0. 52 sec One cardiac cycle occurs every 0. 8 sec

Cardiac Cycle n n n Stroke volume-volume of blood (70 cc) pumped out of one ventricle of the heart in a single contraction Heart rate- number of contractions per minute(60 -100 bpm Cardiac output-amount of blood pumped by the left ventricle in 1 minute (4 -8 L/min) q CO= SV XHR

Cardiac Cycle n n Preload-degree of myocardial fiber stretch at the end of diastole Afterload-resistance against which the heart must pump to eject blood through the semilunar valves and into peripheral vessels STARLING’S 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 System n Sympathetic-prepares for physical activity-fight or flight response-norepinephrine (Adrenergic nerve endings) q q Alpha-vasoconstriction Beta n n n Beta 1 -increase HR & contractility Beta 2 -bronchial dilation & vasodilation Parasympathetic-rest & digest function q Acetylcholine (cholinergic nerve endings)

Electrophysiologic Properties n n Automaticity-ability to generate an electrical impulse spontaneously & repetitively Excitability-ability to be electrically stimulated or respond to an electrical stimulus Conductivity-ability to receive an electrical stimulus and transmit to other cardiac cells Contractility-also rhythmicity is the ability to shorten and cause contraction in response to an electrical stimuluscoordination of contraction to produce a regular heartbeat

Major electrolytes that affect Cardiac Function n 3 major cations q q q n K-performs a major function in cardiac depolarization and repolarization Sodium plays a vital part in myocardial depolarization Calcium 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 Ions n n n Resting cardiac cells (Polarization) –inside the cell is negatively charged. K is greater in the cell; Na greater outside the cell (positively charged)-Resting membrane potential Depolarization (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 Periods n n n Ensures that the muscle is totally relaxed before another action potential occurs Atrial muscle-0. 15 sec Ventricular muscle-. 25 -. 30 sec

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

Cardiac Conduction System

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

EKG n n ECG/EKG-a graphic representation of cardiac activity 12 lead-shows electrical activity from 12 different planes of the heart-used as a diagnostic tool rather than a monitoring device Electrode-adhesive pad that contains conductive gel and designed to be attached to skin Leads-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 Leads n n n Baseline-isoelectric line-no current flow in the heart; consists of positive, negative deflections or biphasic complex 3 or 5 lead- used for monitoring the current cardiac activity of patients at risk for cardiac abnormalities Lead ll or MCL 1 -modified chest leads mostly used because of ability to visualize P waves. MCL provides a R sided view of the heart. MCL 6 -L sided view of the heart

EKG Leads n Limb leads q q n Bipolar leads-measures activity between 2 points (I, III) Unipolar leads-positive electrodes onlya. VR, a. VL, a. VF Chest leads-6 precordial leads

LIMB LEADS & AUGMENTED LEADS

EKG Graph Paper

Segments and Intervals

Segments and Intervals n n n n P wave-deflection representing atrial depolarization PR 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-point ST 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 line T wave- ventricular repolarization, usually rounded, positive deflection U wave-smaller polarity as T wave-slow repolarization- not normally seen except in hypokalemia QT interval-total time for ventricular depolarization and repolarization

HR Determination q 6 second method n q P-P or R-R interval method n n q count QRS complexes in a 6 sec strip x 10 (30 large boxes in 6 sec strip) count 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 Analysis n n n n Analyze P waves- P wave is present. shape is consistent, must be before each QRS Analyze QRS complex- QRS complex is present & consistent Determine atrial rhythm or regularity- check regularity by assessing P-P or R-R Determine ventricular rhythm or regularity-check regularity by assessing R-R Determine heart rate-use one of the methods Measure the PR interval-measurement should be constant and should be between 0. 12 -0. 20 Measure the QRS duration-measurement should be constant and should be between 0. 04 -0. 10 sec Interpret the rhythm

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

Artifacts n Waveforms outside the heart-interference caused by: q Patient movement wandering baseline q Loose or defective electrodes-lost contact with patient’s skin q Improper grounding-in touch with an outside source of electricity q Faulty EKG apparatus

Normal Sinus Rhythm SA 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. 12 sec

Sinus Bradycardia SA node fires slower than normal heart rate-less than 60 bpm Rhythm is regular P wave upright and same shape PR is constant. 12 -. 20 sec QRS-normal <. 12 sec

Sinus Bradycardia n Causes: q q n Adverse effects: q n Vagal stimulation, MI, hypoxia Digitalis toxicity Medication side effects Normal to athletes Dizziness, weakness, syncope, diaphoresis, pallor, hypotension Treatment q According to symptoms, atropine to speed up heart rate, pacemaker

Sinus Tachycardia SA 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 Tachycardia n n n Causes n Emotionally upset, pain, fever, thyrotoxicosis, hypoxia, hypovolemia, inhibition of vagus nerve, n Caffeine, norepinephrine, theophylline Adverse effects q Angina, dizziness, hypotension, increased in cardiac workload Treatment q Treat the cause q Medications may be given- betablockers

Sinus Arrhythmia n n n n The only irregular rhythm from the sinus node and has a cyclic pattern that usually corresponds with breathing Rate- varies with respiratory pattern Regularity-irregular in a repetitive pattern P waves-Upright in most leads, same shape and one to each QRS P -P interval is irregular QRS-<. 12 sec Cause-usually caused by breathing pattern but can also heart disease Treatment- usually non required

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

Premature Atrial Contractions n n n Causes- atria becomes hyper and fire early caused by medications, caffeine, tobacco, hypoxia or heart disease Adverse effects-if frequent can be a sign of impending heart failure or atrial tachycardia or fibrillation Treatment-O 2, omit caffeine, tobacco or other stimulants. Give digitalis or quinidine, treat heart failure.

Premature Atrial Contractions Rate normal Rhythm usually regular except for a PAC P waves shaped differently from a normal P wave or hidden in preceding T wave PR interval . 12 to. 20 sec QRS . 12 sec similar to underlying rhythm

Supraventricular Tachycardia (SVT) n n n Tachycardia (>150 bpm) originating above the ventricles-SA node, atria, AV nodes P waves not discernible-hidden in T waves Paroxysmal-starts & ends abruptly Causes-same as PAcs Adverse 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) Rate 150 -250 bpm Rhythm regular P waves not discernible PR not discernible QRS usually less than. 10 sec

Atrial Flutter n n n Results when one irritable atrial foci fires out regular impulses at a rapid rate that P waves are in a sawtooth pattern Av node (gatekeepers) cannot depolarize fast enough to keep up, many impulses never get through to ventricles. Conduction ratio is variable-2: 1 block, 3: 1 block or 4: 1 block. Slow ventricular response. VR of <60 pm; rapid VR >100 -150 bpm) Causes-acute MI, CHF, digitalis toxicity, pulmonary embolism, SA node disease, septal defects Adverse effects-decreased cardiac output Treatment-digitalis, cardioversion, calcium channel blockers, ablation

Atrial Flutter Rate atrial 250 -300 bpm, ventricles-variable Rhythm regular if conduction ratio is constant, irregular if conduction rate varies P waves replaced by fluttery waves PRnot measurable QRS <. 12 sec

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

Atrial Fibrillation

Junctional Rhythms n n n n Arrhythmia originating in AV node HR= 40 -60 bpm; accelerated =60 -100 bpm; junctional= 100 -140 bpm P wave-absent, inverted before or after a QRS PR interval-<. 12 if P precedes a QRS <. 12 sec Cause-vagal stimulation, hypoxia, ischemia of SA node, MI, digitalis toxicity Treatment-varies according to type of arrhythmia. Atropine to increase HR, withhold or decrease medication that can slow heart rate

Junctional Rhythms

Ventricular Dysrhythmias n n n Ventricles serves as pacemaker Heart rate significantly reduced (20 -40 beats per min Normal conduction system bypassed QRS bizarre in appearance & >0. 12 sec P waves absent (buried or hidden in QRS) Rhythms considered life threatening

Premature Ventricular Complexes (PVCs) n n n A single ectopic (out of place) complex from an irritable site Indicates increased myocardial irritability Precursors of more serious lethal rhythms Cardiac output compromised Causes n n Myocardial ischemia, Emotional stress, increased physical exertion, CHF, electrolyte imbalance, digitalis toxicity or acid base imbalances Treatment- based on symptoms and causative factors n O 2 and antidysrhythmics

PVCs q q q q Unifocal-arise from one single site Multifocal- originate from different sites Ventricular bigeminy- every other beat is a PVC Ventricular trigeminy-every third beat is a PVC Ventricular quadrigeminy- every 4 th beat is a PVC Interpolated- a PVC between two sinus beats Couplet 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) Unifocal PVCs Multifocal PVCs

Premature Ventricular Contraction (PVC Bigeminy NSR with Couplets

Ventricular Tachycardia n n n 3 or more PVCs in a row overriding pacemaker Sustained-lasts more than 30 sec Unsustained- less than 30 sec Can be tolerated for short bursts but can cause profound shock if unconscious or untreated Causes- as with PVCs Treatment q Pulseless Vtach-treated like Vfib q Stable-drug intervention n Lidocaine, procainamide, amiodarone q Unstable- defibrillation

Ventricular Tachycardia Rate 100 -25 bpm Regularity usually regular P waves none PR will vary if present QRS wide & bizarre >0. 12

Ventricular Fibrillation (VFib) n n n Fatal, most common initial rhythm in cardiac arrest Myocardial cells quiver rather than depolarized Usually coarse (amplitude > 3 mm) then becomes fine (amplitude less than 3 mm) No cardiac output- cardiovascular collapse Causes- MI, drug toxicity or overdose, hypoxia, CAD Treatment- immediate defibrillation must be done, CPR, epinephrine (medications make defibrillations more successful and prevent recurrence

Ventricular Fibrillation (VFib) Rate cannot be counted Regularity rapid, not detectable P waves none QRS none detectable

Asystole n n n Cardiac standstill Absence of all ventricular activity-no waveforms Check on 2 leads-? Very fine Vfib Clinical death-absence of pulse and respirations Causes- MI, cardiac trauma, ventricular aneurysm, CHB Treatment-atropine to reverse vagal influences, epinephrine, CPR, pacemaker, dopamine, O 2

Ventricular Asystole Rate zero Regularity none P waves none QRS none

Atrioventricular Blocks n n Impulses 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 sinus Rate normal or slow-symptomatic or asymptomatic Site of block is either AV node or bundle branches q First dgree q Second degree n Type l-Mobitz l n Type ll- Mobitz 2 q Third degree

First degree AV block n n n Prolonged PR interval that results from a delay in the AV node’s conduction of sinus impulse to ventricles All parameters are normal except for prolonged PR interval (hallmark of 1 st degree) Usually asymptomatic Causes-AV node ischemia, digitalis toxicity, use of betablockers or calcium blockers Treatment- treat cause

First Degree AV Block Rate based on underlying rhythm Regularity usually regular P waves upright, one to each QRS PR interval >. 20 sec QRS <. 0. 12 sec looks alike

Second Degree Block (Mobitz l (Wenckebach n n n Progressive prolongation of the impulse Cyclic 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 irregular Cause-MI, digitalis toxicity, nmedication effects Treatment-atropine if heart rate is slow & asymptomatic, pacemaker.

Second Degree Block (Mobitz l (Wenckebach) Rate-Atrial rate normal: ventricular rate less than atria Regularity-maybe regular or irregular P waves-normal P; PR interval progressive prolongation QRS=<0. 12 if at AV node > if block is at bundle branch

Second Degree Block-Mobitz ll n n n Increased risk of progression to 3 rd degree Ratio 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 QRS Causes-same as type l Treatment-02, atropine if patient is symptomatic, epinephrine, dopamine, pacemaker if block continues and symptoms are present

Second Degree Block-Mobitz ll Rate =atrial 60100: ventricular half of atrial rate Regularity=regular P waves= Normal PR interval= constant QRS= <. 12 sec or >. 12 sec if BBB present

Third Degree or Complete Heart Block (CHB) n n n n n SA node sends out impulses as usual but not one is conducted to the ventricles Atria & ventricles beat independently of each other-AV dissociation Rate- atria-60 -100, Ventricles-20 -60 Regularity-Regular P waves- no relationship with QRS PR interval- no pattern, varies QRS-based on site of pacemaker Cause-MI, lesion on conduction system, hypoxia, medication side effects Treatment-pacemaker insertion

Third Degree or Complete Heart Block (CHB)

PACEMAKERS

PACEMAKERS n Device that substitutes for the normal pacemaker of the heart’s electrical conduction system q q n Generator-controls rate & strength of each electrical impulse Lead wires-electrode at the tip relay the electrical impulse from the generator to the myocardium Types q Temporary-used to sustain HR in an emergency situation n n q Transcutaneous (TCP)-external cardiac pacing Transvenous-lead wire threaded through the skin into a large vein Permanent- implanted in patient’s chest

Indications for insertion of Pacemakers n Temporary q q n Suppression of ectopic atrial or ventricular rhythm Acute MI with symptomatic bradycardia, 2 nd & 3 rd degree AV block or bundle branch block Maintenance of adequate HR during special procedures or as prophylaxis after an open heart surgery Termination of AV nodal reentry Permanent- q Chronic atrial fibrillation with slow ventricular response Fibrotic or sclerotic changes in the cardiac conduction system Sick sinus syndrome or Sinus node dysfunction Tachyarrhythmias q Symptomatic bradycardia and Third degree AV block not q q q responding to pharmacologic interventions

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

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

Permanent Pacemakers n AV 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 Rhythms n n Same as for dysrhythmias Remember: 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 System n n n 1 st letter-chamber being paced q A-atrium q V-ventricle q D-dual (both) 2 nd letter- chamber sensed q A-atrium q V-ventricle q D-dual (both q O-off 3 rd letter- type of response by pacemaker to sensory q I-Inhibited (pacemaker will not function when the person’s heart beats q O-none q T-triggered q D-dual

Code System n 4 th letter- ability of generator to be programmed q q q n O-none P-Simple programmability M-Multi programmability C-Telemetry ability P-ability of rate to change with activity 5 th letter-ability of generator to defibrillate q q P-Antitachycardia S-Shock D-antitachycardia processing & shock O-none

Common Problems associated with Pacemakers n Battery failure q q n Decreased amplitude of pacemaker spike and a slowing pacemaker rate Immediate transport to the hospital depending on the patient’s symptoms or underlying rhythm Runaway Pacemakers q q Rapid rate of electrical impulse discharge results Immediate transport to a hospital

Failure to Sense n Failure 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 Sense n n EKG 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, O 2 saturation and notify the MD. Closely observe for ventricular tachycardia caused by failure to sense.

Failure to Capture n n 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 Capture n Nursing Intervention: Should the loss to capture be occasional, one should get a blood pressure, pulse rate, respiration rate, and O 2 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 care n n n n Consent VS Skin prep Pre-op checklist-NPO, dentures, pins Position post op is important Maintain hemodynamic stability Prevent complications

Patient & family Teaching Guides n n n Follow 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 bracelet Take 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 Guides n n Know 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 restrictions Do not apply pressure over the generator. Avoid tight clothing or belts.

Patient & family Teaching Guides n n Do 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. Defibrillator n n n Lead placed via the subclavian into the endocardium Generator is implanted subcutaneously over the pectoralis muscle Monitors HR/rhythm and identifies ventricular tachycardia & ventricular fibrillation Delivers a shock (25 joules) to the heart muscle upon sensing a lethal arrhythmia Some newer ICDs are equipped with antitachycardia and antibradycardia pacers- initiates ovrdrivepacing to prevent painful shocks

Patient & Family teaching guide for AICD n n n Maintain close follow up with physician for testing ICD function & inspection of site Medic alert should be worn & information about the ICD should be available Watch for signs of infection Avoid lifting operative side arm above shoulder for about a week Avoid direct blows to ICD site

Patient & Family teaching guide for AICD n n n When traveling, inform airport official about presence of AICD When ICD fires Routine checks with programmer device needed-2 -3 months Family members should learn CPR Avoid electromagnetic forces that may turn off device Participate in ICD support groups