Cardiac Part II- Arrhythmias and Ischemia Flashcards
What HR is the AV node beating at?
40-60 bpm
What HR are the Purkinje fibers beating at?
20-40 bpm
What length of time is a little box in an EKG?
0.04 secs
What length of time is a big box in an EKG?
0.2 secs
What does a p-wave represent?
Atrial depolarization
What does a QRS segment represent?
Ventricular depolarization
What does a T-wave represent?
Ventricular repolarization
Sinus tachycardia
Upright P wave in lead II preceding every QRS with a ventricular rate >100/min
Causes of sinus tach
Exercise Anemia Dehydration or shock Fever Sepsis Infection Hypoxia Chronic pulmonary disease Hyperthyroidism Pheochromocytoma Medications/stimulants Heart failure Pulmonary embolus
What is the rate when you count the boxes for the next QRS segment?
1st box: 300 2nd box: 150 3rd box: 100 4th box: 75 5th box: 60 6th box: 50 7th box: 43
Sinus bradycardia
Upright P wave in lead II preceding every QRS with a ventricular rate <60/min
Causes of sinus bradycardia
AV blocking meds Heightened vagal tone Sick sinus syndrome Hypothyroidism Hypothermia Obstructive sleep apnea Hypoglycemia
Sinus arrhythmia
Changing sinus node rate with resp cycle
Common in young healthy individuals
HR increases with inspiration and decreases with expiration
Premature atrial contractions (PAC)
Occurs when a focus in the atrium (not the SA node), generates an action potential before the next scheduled SA node action potential
Characteristics of premature atrial contractions (PAC)
Premature Ectopic P-wave looks morphologically different Narrow QRS Compensatory pause
Atrial fibrillation
Occurs when action potentials fire very rapidly within the pulmonary veins or atrium in a chaotic manner resulting in a VERY fast atrial rate (300-600 bpm)
Ventricular rate is usually 100-200 due to the AV node that becomes intermittently refractory
No P-waves
Risk factors for A fib
HTN Valvular heart disease CAD Cardiomyopathy COPD Obesity Sleep apnea Excessive EtOH DM Thyrotoxicosis
S/Sx of A fib
Asymptomatic Palpitations Fainting SOB CP CVA
Classifications of A fib
First detected -Only one diagnosed episode Paroxysmal -Recurrent episodes that stop on their own in <7 days Persistent -Recurrent episodes that last >7 days Permanent -An ongoing long-term episode
Management of A fib
Rate control- beta blockers, calcium channel blockers, digoxin
Rhythm control
Anticoagulation
-Warfarin, heparin, dabigatran, rivaroxaban, apixaban
-ASA
Cardioversion
-Electrical or chemical (amiodarone, etc.)
Ablation/MAZE procedure
Atrial flutter
Occurs when a “reentrant circuit” is present causing a repeated loop of electrical activity to depolarize the atria at a fast rate of ~250-350 bpm
Produces a “sawtooth” pattern of the P waves with lack of P waves
A narrow complex tachycardia at a ventricular rate of exactly 150 bpm is very commonly atrial flutter
Supraventricular tachycardia (SVT)
Any tachycardia that begins above the ventricles (at or above the AV node)
-Paroxysmal (comes and goes) supraventricular tachycardia (PSVT)
Mechanisms of supraventricular tachycardia (SVT)
Re-entry: often quick acceleration to 200 bpm
Automaticity: atrial tachycardia, junctional ectopic tachycardia
Antidromic
Going in a clockwise direction
Orthodromic
Going in a counterclockwise direction
S/sx of supraventricular tachycardia (SVT)
Palpitations SOB CP Tachypnea Dizziness Loss of consciousness
EKG findings in supraventricular tachycardia (SVT)
Narrow QRS complex
Tachycardia
Tx for supraventricular tachycardia (SVT)
Physical maneuvers -Valsava, coughing, carotid massage, drinking ice water, plunging the face into cold water Medications -Adenosine Cardioversion -Synchronized
Junctional rhythm
Occurs when the electrical activation of the heart originates near or within the AV node instead of from the SA node
Characteristics of junctional rhythm
Narrow QRS complex
P wave frequently is not seen (may be buried)
P waves sometimes seen after QRS
May be slow or fast
What does accelerated indicate if it precedes the words junctional bradycardia?
> 60 bpm HR
Premature ventricular contraction (PVC)
Occurs when a focus in the ventricle generates an action potential before the next schedule SA nodal action potential
Characteristics of premature ventricular contractions (PVC)
Premature
Ectopic
Wide complexes
Compensatory pause
V tach
Wide QRS complex (>120 ms) originating in the ventricles at a rate >100 bpm
Considered to be hemodynamically unstable life-threatening
-May or may not have a pulse
Tx for v tach
ACLS (defibrillation, epi, antiarrhythmics)
Classifications of v tach
Sustained- lasts more than 30 secs or symptomatic
Non-sustained VT: lasts less than 30 secs and is asymptomatic
Monomorphic- same pattern
Polymorphic- changing pattern
What electrolyte finding occurs with Torsades de Pointes?
Hypomagnesemia
Steps of pulseless V-tach
- No pulse
- IV, O2, monitor
- Start CPR (2 min), hook up AED
- Evaluate rhythm and pulse
- Defibrillation
- Continue CPR (2 mins)
- Evaluate rhythm and pulse
- Defibrillation
- Continue CPR (2 mins) and epinephrine q3-5 mins
- Evaluate rhythm and pulse
- Continue CPR (2 mins) and Amiodarine 300 mg bolus
V-tach tx
Treat with IV Mg
Clinical pearl about V-tach
Pts with a prolonged QT interval have a higher risk of developing polymorphic VT
Idioventricular rhythm
It is very similar to ventricular tachycardia (VT) except the ventricular rate is <60
Often called “slow VT”
When ventricular rate is between 60-100, it is referred to as an accelerated idioventricular rhythm or AIVR (common with MI)
V fib
Quivering of the ventricles with virtually NO forward CO
Main cause of sudden death in pts with MI
Tx of V fib
- No pulse
- IV, O2, monitor
- Start CPR (2 min), hook up AED
- Evaluate rhythm and pulse
- Defibrillation
- Continue CPR (2 min)
- Evaluate rhythm and pulse
- Defibrillation
- Continue CPR (2 min) and epi q3-5 min
- Evaluate rhythm and pulse
- Continue CPR (2 min) and amiodarone 300 mg bolus
Tx of asystole
High-quality CPR, epi
First-degree AV block
Fixed prolonged PR interval (>0.20 sec)
Causes of 1st degree AV block
Medications
Ischemia
Lyme disease
2nd degree AV block
Mobitz Type I (Wenckebach)
Progressive PR interval prolongation with each beat until a QRS wave is not conducted
Longer, longer, longer…drop QRS
Mobitz type II
Extra P waves with dropped QRS
Usually associated with bradycardia
PR interval may be nl or prolonged
Tx for Mobitz type II
Pacemaker
3rd degree heart block
No communication between atria and ventricle
P waves: equal distance between all
QRS: WIDE, slow, and equal distance between all
Usually symptomatic
Tx for third degree heart block
Pacemaker
What is an EKG finding in hypokalemia?
U wave
What are EKG findings in hyperkalemia?
Peaked T waves
Widening of the QRS
Increase in PR interval
Bradycardia
What is an EKG finding in hypocalcemia?
Prolonged QT interval
What is an EKG finding in hypercalcemia?
Shortened QT interval