Exam I
The first upward wave of the QRS complex is the ___?
R wave
Causes of P*V*Cs
Behaviors: Caffeine, alcohol,nicotine Ischemia/infarction Increased work load on the heart - HF, tachycardia Dig Tox Electrolyte imbalances - hypokalemia
During A-Fib no single impulse completely depolarizes both _____, so there are no ____ waves, just rapid series of tiny, erratic spikes on EKG.
Atria - P waves
Cell-to-cell conduction of depolarization through the myocardium is carried by sodium ions, however, AV Node conduction is due to the slow movement of which ions?
Calcium Ca++
Repolarization
Myocardial cells return to negative resting state
Premature Junctional Complex
P Wave: *Inverted or absent* PR Interval: Absent or short - less than 0.12 seconds Rhythm: Regular with premature beats QRS: Normal *Rate: Underlying rate* *Def* Irritable automaticity focus in the AV junction fires a premature stimulus that is conducted to and depolarizes the ventricles.(The AV node is how the ventricles are normally activated) *Causes* Dig Tox, HF, CAD
Slight decrease in pacing rate due to expiration-activated inhibition of the SA node is controlled by what?
Parasympathetic stimulation - Sinus pacing is regulated by both divisions of the ANS
Depolarization of the ventricular myocytes produces a ______ on the EKG and initiates contraction of the ventricles?
QRS complex In other words - the QRS complex is an electrocardiographic recording of ventricular depolarization.
Sinus "Arrhythmia"
SA Node pacing rate normally varies with respiration - not a true arrhythmia. Typical minimal increases and decreases.
Which ion movement produces cell-to-cell depolarization of the heart?
Sodium Na+
Ventricular depolarization initiates ventricular contraction persists through both phases of re-polarization to the end of the _____ wave?
T wave
ST segment represents
The *initial* phase of ventricular repolarization- but ventrical repolarization is rather *minimal* during the ST segment. Re-polarization of the ventricular myocytes begins immediately after the QRS and persists until the end of the T wave.
The QRS complex represents:
The QRS complex on the ECG strip represents ventricular depolarization. Atrial repolarization usually occurs at the same time as ventricular depolarization and is impossible to distinguish on the ECG. The T wave represents ventricular repolarization. The P wave represents atrial depolarization.
Normal order of conduction through the heart is ____?
The correct sequence of conduction through the normal heart is the SA node, AV node, bundle of His, right and left bundle branches, and Purkinje fibers.
Ventricular Fibrillation
V-Fib is caused by rapid-rate discharges from many irritable, parasystolic ventricular automaticity foci, producing an erratic, rapid twitching of the ventricles. Totally erratic appearance and lack of any identifiable waves on the EKG. Ventricular Rate: >300 bpm
Synchronization of cardioversion prevents the discharge from occurring during the vulnerable period of which of the following?
Ventricular re-polarization (T wave), which could result in ventricular tachycardia (VT) or ventricular fibrillation.
T wave represents:
Ventricular re-polarization (heart cell interiors return to resting negative state)
Medication for VT - Stable acute MI
procainamide
Electrophysiology (EP) studies
During EP studies, the patient is awake and may experience symptoms related to the arrhythmia - during the procedure, the arrhoxythmia will be reproduced under controlled conditions. (pg 751)
Depolarization
Electrical stimulation (cells interiors become positive) - causing mechanical contraction of ventricles - systole
Slight increase in pacing heart rate due to inspiration activated stimulation of the SA node is controlled by what?
Sympathetic stimulation - Sinus pacing is regulated by both divisions of the ANS
Torsades de Pointes
*Def:* Polymorphic VT preceded by a prolonged QT interval *Causes* - CNS disease; low levels of potassium, calcium, magnesium; congenital; certain medications Rhythm requires medical treatment - patient becomes pulse-less and deteriorates quickly. *Tx* - Correct the electrolyte imbalance, admin of isoproternol (Isuprel) IV, initiation of ventricular pacing. Possible tx: magnesium. *Appearance:* Outline looks like a twisted ribbon Rate - 250-350 bpm - brief episodes
Junctional Rhythm
*Def* AV Node becomes the pacemaker of the heart Ventricular Rate: 40-60 bpm Rhythm: Regular QRS: Normal (typically) P Waves: Absent, Hidden in the QRS, inverted (if before the QRS) PR interval: If the P wave is in front of the QRS - less than 0.12 seconds - Short P:QRS ratio: 1:0, 1:1 *S/S:* of reduced cardiac output - Emergency pacing may be needed for bradycardia *Causes:* Increased vagal tone, Complete heart block
Nonparoxysmal Junctional Tachycardia
*Def* Enhanced automaticity in the junctional area - resulting in a rate of 70-120 bpm. Ventricular Rate: *70-120 bpm* Rhythm: Regular QRS: Normal (typically) P Waves: Absent, Hidden in the QRS, inverted (if before the QRS) PR interval: If the P wave is in front of the QRS - less than 0.12 seconds - Short P:QRS ratio: 1:0, 1:1 Indicative of serious conditions --> Dig tox, myocardial ischemia, hypokalemia, COPD
What does the P-R interval represent?
PR interval represents the time needed for *sinus node stimulation*, *atrial depolarization*, and *conduction through the AV node before ventricular depolarization* --- Reflects the conduction of an electrical impulse through the SA node through the AV node. The PR interval is measured from the beginning of the P wave to the *beginning* of the QRS complex.
Because depolarization slows within the AV Node, there is a brief delay or ____ before depolarization is conducted to the ventricles? Why does depolarization slow when the wave enters the AV Node?
Pause To allow time for the blood in the atria to enter the ventricles - producing a brief pause after the P wave.
Premature Atrial Complex - PAC
*Def:* An electrical impulse starts in the atrium before the next normal impulse of the SA node. Resulting in a depolarization stimulus -- seen as an earlier than normal P wave on the EKG. Caused by an irritable atrial automaticity focus -- caffeine, alcohol, nicotine, stretched atrial myocardium, anxiety, hypokalemia, preganacy, infarction/ischemia. *Rate:* Underlying Rhythm (Normally: Sinus Tachycardia) *Rhythm*: Irregular - From irregular early P waves. *QRS*: The QRS complex which follows the early/weird p wave is typically normal (because pacing activity resets) May be abnormally wide- aberrant conducted PAC Hidden - Blocked PAC
Premature Ventricular Complex (PVC)
*Def:* Premature ventricular beat - producing a giant ventricular complex on EKG (Great width, enormous amplitude [height and depth], opposite in polarity of the normal QRS complexes) *Causes:* Hypoxia (Most likely). Other: Caffeine, nicotine, alcohol, HF, tachycardia, dig tox, acidosis, hypokalemia *Rate:* Underlying rate *Rhythm*: Irregular *P Wave*: Hidden (in the QRS or T wave), in front of the QRS, or following the QRS complex with a different shape *PR Interval:* If the P is in front of the QRS - then the PR interval would be less than 0.12 seconds *QRS:* Wide (> 0.10 sec), bizarre appearance *P: QRS Ratio*: 0:1, 1:1 Typically there is a "compensatory" pause after a PVC S/S - The effect of PVCs depend on the timing in the cardiac cycle Prognosis - Not serious Tx - PVCs that are frequent/persistent - treated with amiodarone, sotalol - Long term medication therapy is not indicated.
Atrial Flutter
*Def:* Rapid succession of identical, back-to-back, atrial depolarization waves (flutter waves) at a rate of 200-400 bpm. There is a therapeutic block from at the AV node preventing impulses from being conducted into the ventricular (This prevents the ventricle rate from also being 200-400). *Ventricular Rate:* Typically 75-150 *QRS:* Normal, abnormal, absent *P waves:* Saw tooth shape - Called "F" waves *P:QRS* ratio: 2:1, 3:1, 4:1 *S/S:* SOB, CP, Hypotension *Tx:* Electrocardioversion, medications used to slow ventricular response rate (Beta-blockers, digitalis), catheter ablation Who? Patients with COPD, valvular disease, and thyrotoxicosis, following open heart and repair of cardiac defects.
T wave represents
Final *rapid* phase of ventricular repolarization - during which the ventricular repolarization occurs quickly and effectively
SA Node Rate Normal
60-100/min The SA Node generates pacing impulses at a constant unvarying rate, producing cycles of equal length, so the rhythm of the heart is said to be regular.
Atrial Fibrillation
AF (Atrial Fibrillation) is caused by many irritable parasystolic atrial foci firing at rapid rates. No single impulse depolarizes the atria completely (*no P waves*), and only an occasional, random atrial depolarization reaches the AV Node to be conducted to the ventricles; this produces *irregular ventricular (QRS) rhythm.* Irregular ventricular and atrium rhythm Rate: Atrial rate is 300-600, ventricular rate is normally 120-200 in untreated AF QRS Shape: Normal No P waves P:QRS ratio: Many: 1 Nursing Implication: You must determine and document the general ventricular rate in A-fib (QRS per six second strip times ten)
Atroventricular Nodal Reentry Tachycardia AVNRT
AVNRT occurs when -- an impulse is conducted to an area in the AV node that causes the impulse to be rerouted into the same area over and over again at a very fast ventricular rate. Benign dysrhthmia. *Onset/Cessation* -- Abrupt *Rate* --- 150- 250 Atrial Rate, 120-200 ventricular rate *QRS Complex* --- Usually narrow (< 120 ms) unless pre-existing bundle branch block, accessory pathway, or rate related aberrant conduction *S/S* --- Palpitations,Restlessness, CP, SOB, Pallor, Hypotension, LOC *Causes* ----Caffeine, nicotine, hypoxemia, stress. Underlying causes --- CAD, cardiomyopathy, occurs more often in females due to underlying structural heart disease *Tx* --- Catheter ablation, vagal maneuvers, bolus of adenosine followed with larger doses or with a calcium channel blocker, cardioversion (If heart does not respond to medication)
Ventricular Asystole
Absent QRS complexes confirmed in *two* different leads, although P waves may be apparent for a short duration. No heartbeat, no palpable pulse, no respiration Prognosis: Fatal Tx: High quality CPR (focus on chest compression), intubation, establishment of IV access, After 2 minutes (5 cycles of CPR) a bolus of IV Epi is administered and repeated at 3-5 minute intervals -Admin of atropine bolus IV administered soon after rhythm check -Possible admin of vasopressin for the first or second dose of epi Possible causes: Hypoxia, acidosis, severe electrolyte imbalance, drug overdose, hypovolemia, cardiac tamponade, tension pnemothorax, hypothermia
The Q wave, when present always occurs at the _______ of the QRS complex and is the first downward deflection of the complex.
Beginning
The release of free calcium ions into the interiors of the myocytes produces - myocardial ______?
Contractions Ca++ ions cause myocyte contraction
QT interval represents
Duration of ventricular systole (contraction) - reflects the time from ventricular depolarization (positive state) through re-polarization (negative resting state) Clinical significance: Good indicator of repolarization. Patients with long QT intervals (more than half of the R-to-R interval; more than 0.32-0.4 in a normal HR) are at risk for dangerous ventricular rythms
Ventricular Tachycardia
Defined as three or more PVCs in a row occurring at a rate exceeding 100 bpm. *Emergency* - Patient is typically unresponsive and pulse-less Ventricular Rate - 100-200 bpm Atrial Rate - Depends on underlying rhythm Rhythm - Usually regular QRS Shape/Duration - 0.12 seconds or more -- Bizarre, Abnormal Shape P wave - Hidden - Atrial rate and rhythm may be difficult to detect PR interval - Very irregular if P waves are seen P:QRS ratio - Difficult to determine - if P waves are present, there are more QRS complexes than P waves Tx: Antiarrhythmic medications, anti-achycardia pacing, direct cardioversion. For pulseless VT - Dfibrillation.
In general, when you see an upward wave on an EKG you know that it represents a _______ wave moving toward the positive electrode?
Depolarization waves are represented as upwards waves on an EKG
P wave represents:
Electrical activity (depolarization) of both atria - also thus, represents the simultaneous contraction of the atria [This simultaneous contraction of the atria forces blood to pass through the AV valves between the atria and the ventricles]
Idioventricular Rhythm
Idioventricular Rhythm - AKA - Ventricular Escape Rhythm Purkinje fibers become the pacemaker of the heart. How? The SA node has failed to create an impulse (exl - from increased vagal tone) and the AV node also cannot be conducted through (exl - from complete AV block). *Ventricular Rate*: *20-40 bpm* If exceeds 40 bpm then rhythm is accelerated idioventricular rhythm (AIVR) *Rhythm:* Regular *QRS Shape/Duration:* Bizarre, abnormal shape, duration of 0.12 seconds or more *S/S* of reduced cardiac output, LOC *Tx:* ID the underlying cause, admin of epi, atropine, vassopressor medications, initiating emergency transcutaneous pacing. If no S/S, bedrest.
Premature ventricular contractions (PVCs) are considered precursors of ventricular tachycardia (VT) when they _______?
Occur at a rate of more than six per minute, they indicate increasing ventricular irritability and are considered forerunners of VT. PVCs are dangerous when they occur on the T wave. PVCs are dangerous when they are multifocal (have different shapes).
Following depolarization, repolarization is due to the controlled outflow of ___ ions from the myocytes?
Potassium (K+) ions Potassium ions cause repolarization of myocytes
How is repolarization accomplished?
Potassium (K+) ions leaving the myocytes
U wave
Repolarization of the Purkinje fibers (takes longer than ventricular repolarization) - The end of the T wave marks the end of the ventricular repolarization; however, repolarization of the Purkinje fibers terminates a little later -- after the T wave. This final repolarization of the Purkinje fibers may produce a small hump - the U wave, following the T wave.
Which of the following nursing interventions must a nurse perform when administering prescribed *vasopressors* to a patient with a cardiac dysrhythmia?
The nurse should *monitor the patient's vital signs and cardiac rhythm* for effectiveness of the medication and for side effects and should always have emergency life support equipment available when caring for an acutely ill patient. The side effects of vasopressor drugs are hypertension, dysrhythmias, pallor, and oliguria.
"Holiday heart" syndrome
This is the association of heart dysrhythmias, especially atrial fibrillation, with binge drinking
Where does ventricular systole begin and how long does it persist for - as seen on an EKG?
Ventricular systole (contraction) begins with the QRS and persists until the end of the T wave. So, ventricular contraction (systole) spans depolarization and repolarization of the ventricles
Medication for VT - Unstable or impaired cardiac function
amiodarone
