Ch. 35 (cont.): Dysrrhytmias Flashcards
What is a premature atrial contraction (PAC)?
-contraction starting from an ectopic focus in the atrium (location other than SA node) SOONER than expected
-travels by abnormal pthwy
-@ AV node can be stopped, delayed, or conducted normally
What can a PAC result from in a normal heart?
-emptional stress
-physical fatigue
-caffeine
-tabacco
-alcohol
What are other causes of PACs?
-hypoxia
-electrolyte imbalance
-hyperthyroidism
-COPD
-heart disease: CAD, valvular disease
What are manifestations of PACs?
-palpitations
-heart “skips a beat”
What is the treatment of PACs?
-monitor for more serious dysrhythmias
-withhold sources of stimulation (caffeine, epi, dopamine)
-BB
What is the clinical significance of PAC in healthy hearts?
not significant
What is the clinical significance of PACs in pts w/ heart disease?
may warn or start more serious dysrhythmias
What is supraventricular tachycardia (SVT)?
a rapid regular heartbeat that originates anywhere above the ventricles (supravetricular), caused by rapid firing of ectopic beats
What is reentrant phenomenon?
-SVT occurs bc of this
-reexcitation of the atria when there is a 1-way block
-PAC triggers a run of repeated premature beats
What does paroxysmal mean?
an abrupt onset and ending
What is SVT associated with in a normal heart?
-overexertion
-emotional stress
-deep inspiration
-stimulants (caffeine, tobacco)
What is SVT also associated with?
-rheumatic heart disease
-digitalis toxicity
-CAD
-cor pulmonale
What are the EKG characteristics of SVT?
-HR 151-220
-regular or slightly irregular rhythm
-p wave may be abnormally shaped or hidden
-PR interval shortened or normal
-QRS complex normal
What is the clinical significance of SVT?
depends on the associated symptoms
-prolonged episode of HR > 180 will ↓ CO (hypotension, palpitations, dyspnea, angina)
What is the treatment for SVT?
-vagal stimulation (valsalva, carotid massage, coughing)
-drugs (IV adenosine, IV BB, IV CCB)
-synchronized cardioversion
What is the drug of choice to treat SVT?
IV ADENOSINE
-has a short half-life (10 sec) and well tolerated
What is important to remember when administering IV adenosine?
-tell pt they may feel chest pressure after med is given
-inject as close to heart as possible
-give IV rapidly (1-2 sec) and follow with 20 mL NS flush
-monitor ECG, brief asystole common
-assess pt for flushing, dizziness, chest pain, palpitations
What is an atrial flutter?
atrial tachydysrhythmia id by recurring, regular, SAWTOOTH shaped flutter waves that originate from a single ectopic focus on r atrium (or less often l atrium)
Does atrial flutter occur in a healthy heart?
rarely
What is atrial flutter associated with?
-CAD
-hypertension
-mitral valve disorder
-pulmonary embolus
-chronic lung disease
-car pulmonale
-cardiomyopathy
-hyperthyroidism
-drugs: digoxin, quinidine, epi
What are the EKG characteristics of atrial flutter?
-atrial rate 200 to 350
-ventricular rate varies based on conduction ratio
-2:1, vent rate is 150
-usually regular
-PR interval not measurable
-QRS complex normal
What is the clinical significance of atrial flutter?
-high ventricular rate and loss of atrial “kick” = ↓ CO
-this can cause HF
-pts have an ↑ risk for STROKE
Why are pts with an atrial flutter at higher risk for STROKE?
-thrombi can form in atria from stasis of blood
-warfarin or other anticoagulants are given for prevention
What are s/s of HF?
-palpitations
-tachy
-fatigue
-malaise
-SOB onexertion
-dyspnea
-chest pain
-syncope
What is the treatment of choice for atrial flutter?
radiofrequency catheter ablation in an EPS laboratory
What are treatment options for atrial flutter?
-BB, CCB
-antidysrhythmic drugs (ibutilide [Corvert])
What is atrial fibrillation (Afib)?
-characterized by a total disorganization of atrial electrical activity
-paroxysmal or persistent
-MOST COMMON clinically sig dysrhythmia
In what pts does Afib usually occur in?
in pts w/ underlying heart disease
-CAD
-valvular heart disease
-cardiomyopathy
-hypertensive heart disease
-HF
-pericarditis
When can Afib develop acutely?
-thyrotoxicosis
-alcohol intoxication
-caffeine
-electrolyte problems
-stress
-heart surgery
What is Afib commonly seen together with?
HF bc of similar risks and common physiological changes
What are the EKG characteristics of Afib?
-atrial rate as hi as 350-600
-chaotic fibrillatory waves replace the P wave (no ID P wave)
-irregular ventricular rate
What is the clinical significance of Afib?
-results in ↓ CO bc of loss of atrial kick &/or a rapid ventricular response
-HIGH RISK for pulmonary or systemic emboli (Afib accounts for 20% of strokes)
What are the goals of Afib treatment?
1) ↓ ventricular response ( to <100 bpm)
2) prevent stroke
3) convert to sinus rhythm
What can electrical cardioversion do to Afib?
-may convert to a normal sinus rhythm
What is required if a pt is in Afib for > 48 hrs PRIOR to cardioversion?
warfarin therapy is NEEDED for 3-4 weeks PRIOR to cardioversion
What procedure can be done to RULE OUT clots before the cardioversion?
-transesophageal echocardiogram
-if no clots found, anticoagulat therapy may not be needed
What if drugs or cardioversion don’t convert the Afib to normal sinus rhythm?
-pts need long term anticoagulant therapy
-WARFARIN often used and monitor therapeutic levels
What drugs are commonly used to control rate in pts with Afib?
-non-dihydropyridine CCB (diltiazem or verapamil)
- BB (carvedilol or metoprolol)
-digoxin
What is the desired rate when treating Afib?
< 80 at rest and < than 110 w/ moderate exerion
What drugs are commonly used for rhythm control in pts w/ Afib?
-amiodarone (MOST EFFECTIVE)
-dronedarone
-propafenone
-sotalol (BB and antiarrhythmic)
What is preferred when treating Afib: rate control or rhythm control?
RATE CONTROL shows better outcome in decreasing CV hospitalization
What are commonly used oral anticoagulants for stroke prevention in pts with Afib?
1) Warfarin (GOLD STANDARD)
-frequent monitoring, increase risk for major bleeding, narrow therapeutic range
2) Dabigatran (direct thrombin inhibitor)
3)Aprixaban, Edoxaban, Rivaroxaban (factor Xa inhibitors)
What procedure is strongly recommended to pts with symptomatic paroxysmal Afib?
cardiac ablation
-also for pts unable to tolerate antiarrhythmic or refractory to drug treatment
What is the Maze procedure?
-stops Afib by interrupting ectopic foci
-incisions made in both atria and cryoablation is used to stop formation and conduction of ectopic signals and restore normal sinus rhythm
What is an atrioventricular heart block (AV block)?
-block of conduction from atria to ventricles
-CAD, MI, infections, enhanced vagal tone, drug effects (digoxin toxicity)
What do you always assess for in pts w/ AV blocks?
assess for CO and treat cause
What are the 4 types of AV blocks?
1) first-degree block
2) second-degree block, Morbitz type I Wenckebach
3) second-degree block, Morbitz type II
4) third degree block (COMPLETE)
What is a first-degree AV block?
every impulse is conducted to ventricles, but the time of AV conduction is prolonged
-prolonged PR interval (>0.2)
-same PR interval for each beat
What is first-degree AV block associated w/?
-increasing age
-MI
-CAD
-rheumatic fever
-hyperthyroidism
-electrolyte imbalance
-vagal stimulation
-drugs (digoxin, BB, CCB, flecainide)
What are the ECG characteristics of first-degree AV blocks?
-HR normal
-rhythm regular
-normal P
-normal QRS
!! PR INTERVAL PROLONGED !!
What is the clinical significance of first-degree AV block?
-typically NOT serious
-pts asymptomatic
-no treatment
-monitor for heart rhythm changes
What is a second-degree type I AV block (Morbitz I, Wenckebach)?
-gradual lengthening of PR interval until an atrial impulse is non conducted and a QRS complex is blocked
What may result in a second-degree type I AV block?
-drugs (digoxin, BB)
-CAD, ischemia, MI
What are the EKG characteristics of second-degree type I AV blocks?
-regular atrial rate
-ventricular rate may be slower
-ventricular rhythm irregular
“longer,longer, longer, drop, now you have a Wenckebach”
-normal P and QRS
What is the clinical significance of second-degree type I AV blocks?
-usually result from myocardial ischemia or inferior MI
-usually transient and well tolerated
-may be warning sign (acute MI) of more serious AV conduction prblms (complete heart block)
-may decrease CO
When may second-degree type I AV blocks be symptomatic?
if fewer conducted beats (2:1 or 3:2 block) lead to ventricular brady
-hypoperfusion (fatigue, lightheadedness, syncope, presyncope, angina), HF
What is the treatment for symptomatic pts with a second-degree type I AV block?
-atropine or temp pacemaker to increase HR (especially if pt has hx of MI)
Where is the block most commonly in a second-degree type I AV block?
block is most commonly within AV node
What is a type 2 second-degree AV block (Mobitz II)?
-P wave non conducted without progressive PR lengthening
-usually occurs when a block in 1 of the bundle branches is present
-more serious
-certain # of impulses from SA node are not conducted to ventricles (occurs in ratios 2:1, 3:1. etc.)
What are type 2 second-degree AV blocks associated with?
rheumatic heart disease, CAD, anterior Mi, drug toxicity
What are the ECG characteristics of a type 2 second-degree AV block?
-normal atrial rate and rhythm
-vent rate depends on degree of block, rhythm may be irregular
-normal P
-PR interval normal or prolonged
-QRS COMPLEX > 0.12 SEC BC OF BUNDLE BRANCH BLOCK
What is the clinical significance of a type 2 second-degree AV block?
!!! DANGEROUS: can progress to 3rd degree block !!!
-↓ Hr often results in ↓ CO w/ subsequent hypotension and myocardial ischemia and angina
What is the treatment for a type 2 second-degree AV block?
PERMANENT PACEMAKER
What is a 3rd degree AV block?
!!! COMPLETE HEART BLOCK !!!
-a form of AV dissociation where NO impulse from atria are conducted to ventricles
-atria and ventricles beat independently
What is 3rd degree AV block associated w/?
-severe heart disease (CAD, MI, myocarditis, cardiomyopathy)
-some systemic diseases (scleroderma)
-drugs (digoxin, BB, CCB)
What drugs can cause 3rd degree AV block?
digoxin, BB, CCB
What are the EKG characteristics of 3rd degree AV block?
-atrial rate 60-100
-ventricular rate depnds on site of block
*AV node: 40-60
* His-Purkinje: 20-40
-atrial and vent rhythms regular but unrelated
-normal P
-NO RELATIONSHIP btwn P wave and QRS complex
What does the QRS complex look like if the escape rhythm starts at the bundle of His or above (3rd degree AV block)?
normal
What does the QRS complex look like if the escape rhythm starts BELOW the bundle of His (3rd degree AV block)?
widened
What is the clinical significance of 3rd degree AV block?
-usually results in ↓ CO w/ subsequent ischemia, HF, shock
-syncope may result from severe bradycardia or even periods of asystole
What is the treatment for 3rd degree AV block?
symptomatic pts need a transcutaneous pacemaker until a temp transvenous one can be inserted
-PT NEEDD PERMANENT PACEMAKER ASAP
What drugs can be given to treat 3rd degree AV block?
-dopamine and epi is an interim measure to ↑ HR and support BP until temp pacing starts
-atropine not effective
Is atropine an effective treatment for 3rd degree AV block?
NO
What is a premature ventricular contraction (PVC)?
-early QRS complex
-QRS is WIDE and DISTORTED
When does ventricular tachycardia occur?
when theres 3 or > consecutive PVCs
What are PVCs associated with?
-stimulants (caffeine, alcohol, nicotine, aminophylline, epi, isoproterenol)
-electrolyte imbalances
-hypoxia
-fever
-exercise
-emotional stress
What diseases are associated with PVCs?
-MI, mitral valve prolapse, HF, cardiomyopathy, CAD
What is the clinical significance of PVCs in a normal heart?
usually NOT harmful
What do PVCs indicate in CAD or acute MI?
ventricular irritability
What is the clinical significance of ventricular tachycardia (VT)?
-ominous sign
-LIFE-THREATENING bc of decreased CO and possible development of VFIB (LETHAL)
What is the first line of treatment for a pt who is symptomatic bc of a junctional escape rhythm?
ATROPINE
What are some possible pacemaker issues?
1) Failure to pace
2) Failre to capture
3) Failure to sense
What is failure to pace?
(fire)
-pacemaker does not fire when it should
-cause: battery or pulse generator fail, wire issues, loose connection
What is failure to capture?
electrical impulse (spike) generated but no depolarization
-cause: output set too low or displacement of wire, battery fail, fracture of pacemaker wire, increased pacing threshold
What is failure to sense?
-doesnt sense pts cardiac rhythm and initiates pulse (earlier than programmed)
-cause: displaced pacemaker wire
