7: Dysrhythmias Flashcards Preview

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Flashcards in 7: Dysrhythmias Deck (47):

Normal Sinus rhythm

-there must always be a P wave
-the P wave should be a rounded shape
-each P wave should be the same shape
-each P wave should be followed by a QRS of normal morphology
-the P-R interval should be 3-5 small squares and constant
-the rhythm should be regular


Arrhythmias- SA node

1: sunus bradycardia
2: sinus tachycardia
3: sinus dysrhythmia
4: sinus arrest


Arrhythmias- Atria

1: wandering pacemaker
2: premature atrial contractions (PAC)
3: atrial tachycardia (AT)
4: Paroxysmal supraventricular tachycardia (PSVT)
5: atrial flutter
6: atrial fibrillation


Arrhythmias- AV junction

1: junctional rhythm
2: premature junctional contractions
3: junctional ectopic tachycardia


Arrhythmias- Ventricles

1: ventricular escape complexes and rhythm
2: premature ventricular complexes
3: ventricular tachycardia
4: ventricular fibrillation


Arrhythmias- Conduction

1: AV blocks
- 1-4th degree blocks
2: Bundle branch blocks


dysrhythmia- dx

Holter monitor
-portable ECG recorder for 24hr recording- for arrhythmia that occur less than daily
Treadmill testing
-dysrhythmias exacerbated by stress
Electrophysiologic studies (EP)
-electrodes are placed inside the right atrium and ventricle using catheter
-dx of abnormal foci or tract, SA, AV node disorder, placement of permanent pacemaker


Sinus arrhythmia

Phasic variation of R-R interval with respiration
Heart rate increases during inspiration and decreases during expiration


Sinus arrest

Failure of sinus node to initiate impulse- normal rhythm followed by an absent P wave and an absent ORS
-sick sinus syndrome
-digitalis toxicity
-excess vagal tone


Sick sinus syndrome

causes: degenerative process damaging the sinus node
-Chaga's disease
sx: sinus bradycardia, sinus arrest or SA block, alternating episodes of tachyarrhythmia and bradycardia
Tx: no tx for asymptomatic, permanent pacing for symptomatic pts


Wandering atrial pacemaker (WAP)

Transient shifts in location of dominant pacemaker
-continual changes in the P-wave morphology. P waves vary in size, shape, and directions
-at least 3 different P waves must be present
-varying P-R intervals
Tx: not needed


Multifocal atrial tachycardia (MAT)

WAP associated with tachycardia (>100bpm)
Narrow QRS complexes
-cor pulmonale, digitalis toxicity, CAD, elderly


Atrial tachycardia (AT)

heart rate: 120-250bpm
AV block (by adenosine) does not terminate tachycardia


Premature atrial complexes

Common and benign
Premature P wave (buried in the preceding T wave)


Paroxysmal supraventricular tachycardia (PSVT)

sudden onset, usually initiated by a premature beat and the arrhythmia stops abruptly
Could result in decreased CO, angina, hypotention, CHF
1: AV node reentry (AVNRT)- 90%
2: AV reentrant tachycardia (AVRT)


AVNRT- info

Slow AV nodal pathway for anterograde conduction and Fast AV nodal pathway for retrograde conduction
P-wave buried in QRS and not seen
-if P wave is seen: pseudo 'r' wave at the end of QRS complex in V1, V2**; or pseudo 'S' waves maybe seen in LEAD II, III, aVF**
-Tachycardia associated with prolongation of PR interval


AVNRT- management

Initial maneuvers
-carotid sinus massage
-valsalva maneuver
If fails
-Adenosine (DOC)**
If hemodynamic compromise (hypotension)
-DC cardioversion**
-Beta blocker
-Ca channel blockers
-Class IC antiarrhythmics
-Radiofrequency catheter ablation of slow tract


AVRT- info

AV node and 1 or more bypass tracts
Orthodromic tachycardia (narrow qrs complex tachycardia)
-anterograde via AV node and retrograde via accessory pathway
Antidromic tachycardia (wide qrs complex tachycardia)
-anterograde via accessory pathway and retrograde via bundle of His and AV node


Antidromic AVRT

Wolff-Parkinson-White syndrome (WPW)
associated with Ebstein's anomaly
The bundle of Kent* (accessory pathway)
- results in delta waves**
-Short P-R interval (0.12sec)
-Slurring of upstroke (delta waves) of QRS complex
-Secondary ST-T wave change


AVRT- tx

Catheter ablation (choice)
DC cardioversion
Orthodromic: Adenosine or verapamil*
Antidromic: Procainamide or cardioversion
-contraindicated: AV node blockers** (digitalis, adenosine, diltiazem, verapamil, Ca channel blocker, beta-blocker)


Atrial flutter- info

Rhythm disturbance of the atria
Sawtooth flutter waves (P waves) in LEAD II, III, aVF**
-reentrant atrial tachycardia
-rate of ventricular response increases above 140/m-> CO drops and cardiac sx appear*
Complication- CHF, embolization


Atrial flutter- causes

-long standing HTN
-Valvular heart disease (rheumatic)
-Coronary artery disease
-Acute pulmonary embolism*


Atrial flutter- tx

-when spontaneous reversion doesnt occur
-when there is hemodynamic instability
-acute myocardial ischemia
Rate control
-verapamil, beta-blockers
-catheter ablation (if no response to drugs)


Atrial fibrillation

dysrhythmia due to multiple areas of reentry within the atria
complete disorganization of atrial electrical activity
Atrial rate: 350-600/m-> P waves are replaced by fine, undulating fibrillatory waves ("F" waves)**
R-R interval is irregular
Peripheral emboli**- 15% risk of stroke


Atrial fibrillation- physical exam

Variation in intensity of first heart sound (S1)**
Heart rate is irregular
Absence of 'a' wave in Jugular venous pulsation** (no atrial contraction)


Atrial fibrillation- tx

Rate control- beta blocker, Ca channel blocker, digoxin
Anticoagulant therapy
-Heparin and Warfarin if A-fib > 2days old**
Restoration of rhythm- cardioversion
-hemodynamically instable: IV heparin-> immediate cardioversion**
-hemodynamically stable:
--48hrs of A-fib: continue cate control and anticoagulation for 3 weeks before attempting cardioversion**
Rhythm control
-Type IA, IC, III
-Amiodarone (Class III): DOC following cardioversion**


Junctional escape rhythm

SA node fails to discharge-> AV node becomes the dominant pacemaker
-Inferior MI, cardiac surgery, digoxin toxicity
-inverted or absent P-wave before QRS complex or P after QRS
-narrow QRS


Premature ventricular complexes (PVC)

MC ventricular rhythm disturbance
Two successive PVCs are called "couplet"
-Monomorphic VT: 3 or more PVC >100bp with similar morphology
-Multifocal or polymorphic VT: morphology varies*
-Bigeminy VT: PVCs successively alternate with a sinus beat
Discordant ST segment and T wave changes (T wave is opposite the major deflection of the QRS)
Full compensatory pause- double the preceding R-R interval following PVC


PVC- causes, tx

-excess caffeine, alcohol, tobacco
-emotional stress
-hypoxia, hyperkalemia, hypokalemia

no tx w/o significant sx
Beta blocker can be used in MI


Ventral tachycardia- sx

Sustained VT:
-lasts >30 sec
-associated with hemodynamic instability
-syncope, dizziness, palpitations
Nonsustained VT:
-lasts <30 sec
-not associated with hymodynamic compromise
-Asx or transient palpitations


VT- dx

Intermittent canon 'a' waves in Jugular veins and Variable first heart sound (S1)**


VT- tx

Hemodynamic instability: DC cardioversion**
Stable pts
-Lidocaine (DOC)**
Recurrent sustained or sx non-sustained VT:
-Implanted cardioverter/defibrillator (ICD)


Torsades de Pointes- info

VT characterized by polymorphic QRS* associated with prolonged QT* (often >0.6sec)
Risk of sudden death**


Torsades de Pointes- causes

Congenital anomaly: familial long QT syndrome
Drugs: Quinidine, Disopyramide, Phenothiazine, Tricyclic antidepressants**
Electrolyte imbalance: hypokalemia, hypomagnesemia**


Torsades de Pointes- tx

-IV magnesium** (slows down the heart-> watch out for cardiac arrest)
-Beta blocker, Mexiltine, Phenytoin
-Beta blocker
-if recurs
--Left-sided cervicothoracic sympathetic ganglionectomy
--Dual chamber permanent pacing
--Cardioverter/Defibrillator (ICD) for congenital forms


Ventricular escape beats- Idioventricular rhythm

there is a lack of impulses from SA or AV nodes


Ventricular fibrillation- info

chaotic ventricular rhythm-> no ventricular contraction
no P wave no QRS complex
LETHAL!! in 3-5 mins


V fib- tx

Immediate cardioversion and CPR


First degree AV block

delay in conduction from sinus node to the ventricle
all impulses are conducted
P-R interval >0.2sec


Second degree AV block

intermittent failure of AV conduction
Type I (Mobitz type I or Wenkebach): MC: AV node (qrs narrow)
-Progressive lengthening of the P-R interval-> failure of a P wave to conduct and an absent QRS
Type II (Mobitz type II)
-Abrupt failure of AV conduction
-no preceding gradual P-R prolongation


Second degree AV block type I- tx

Most case dont require tx
Electrophysiologic mapping if
-no identifiable acute cause
-elderly pt
-Severe coronary artery disease
-calcified aortic disease
Permanent pacing if
-Block within the bundle of His (qrs wide)*
-History of dizziness or syncope


Third degree heart block-info

Complete heart block
-total dissociation btw P wave and QRS complex
-Giant cannon wave in jugular vein may be seen when atria contracts against closed AV valve**


Third degree heart block- AV node

Narrow QRS complex
Heart rate >50bmp
Tx: pacemaker, Atropine


Third degree heart block- Bundle of His

Wide QRS complex
Ventricular rate 30-40bpm
Unresponsive to ANS influence*
Tx: permanent pacing**


Right bundle branch block

S2 is widely split due to delayed closure of pulmonic valve
Secondary R wave (R') in right precordial LEADs: V1, V2
Wide S wave: V5, V6


Left bundle branch block

Paradoxical splitting of S2 due to delayed closure of aortic valve** (during inspiration, splitting gets smaller)
Broad R wave: V5, V6
Deep S wave: V1, V2


What to focus on..

Ddx- sinus tachycardia (p-qrst), paroxysmal supraventral tachycardia (pseudo R wave, sudden onset)
Sinus arrest (no p and qrs)
WAP (at least 3 p wave morphology, with tachycardia-> MAT)
PAC (narrow qrs) PVC (wide qrs)- both with premature p wave
PSVT- know tx: AVNRT (adenosine)
Antidromic AVRT: delta waves. contraindication
Atrial flutter/ fibrillation- dx, complication, PE, tx schedule.
premature ventricular complexes- dx
V-tach: management, sx
Torsades de pointes: ekg
V-fib: ekg, tx
AV block: just know all blocks