Johnson Cardiac Rhythm Disturbances Flashcards
4 principles of tx CRDs
- tx patient not EKG 2. ABCD: airways, breathing, circulation, disability 3. assess hemodynamic stability 4. anti-arrhythmic/electrical tx
Arrhythmia symptoms
syncope, lightheadedness, dyspnea, pain in the chest, palpitations
What is, what causes it?
Sinus Tachycardia
Physiologic/pathologic process
- Look for the cause
- Emotion, anxiety, fear, drugs, hyperthyroid
- Fever, pregnancy, anemia, CHF
- Hypovolemia
- RX – underlying cause
medical conditions/dxs associated with bradycardia
Medical Conditions/Situations Associated with Bradycardia
– Normal people
– Healthy athlete - well trained, good physical
endurance
– Physiologic component to sleep, fright, carotid sinus massage, carotid hypersensitivity, avoid tight collars, shave neck lightly, massage or ocular pressure (glaucoma), mental control - yoga training
– Obstructive jaundice - effect of bile salts on SAN
– Sliding hiatal hernia
– Valsalva maneuver - lifting heavy objects, straining bowels
med conditions/dx associated with bradycardia (said know this from the slide)
- Acute inferior MI
- Ischemia
- ↓pO2
- ↑pCO2
- ↓PH
- ↑BP
- SSS
- Convalescence from dig toxicity
Sinus arrhythmia: causes
SAN forms impulses irregularly
- – waxes/wanes with phases of respiration
- – HR increases with inspiration
- – HR decreases with expiration
- – sinus arrhythmia is a normal finding
p wave in sinus brady
P wave represents formation of sinus impulses, Each
atrial impulse is followed by a ventricular beat.
• Rate < 60/min
• P wave of sinus origin (normal axis)
• constant and normal P-R interval (.12 - .20 sec)
- constant P wave configuration in each lead
- regular or slightly irregular P-P cycle or R-R cycle
sinus brady with sinus arrhythmia
PAB- nonconducted
PAB- abberrant conduction
PAB- nonconducted: a premature atrial focus reaches the AV node too early, during its repolarization phase. P’ does not produce a QRS: long base line period generated resembling a block before normal pacing begins again.
PAB- abberrantly conducted: a premature atrial focus causes depolarization of only part of the undle branch conducting system. P’ generates a widened QRS.
Atrial Bigeminy
PAB coupled to the end of a normal cycle “a couplet”: repeating couplet is an a. bigeminy
tx PACs
if symptomatic
– Reverse causes
– Beta adrenergic antagonist (BB) – Metoprolol 25-50 mg BID-TID
PJB
premature junctional beat: when an irritable automaticity focus in the AV junction fires a prematrue stimulus that is conucted and causes contraction of the ventricles, sometimes the atria too
an irritatble junctional focus fireing a prematrure stimulus coupled to the end of each normal cycle
junctional bigeminy
an irritable focus that fires a stimulus after two consecutive, normal sinus generat cycles in a repeating series
junctional trigeminy
retrograde p waves
produced when a junctional focus depolarizes the atria: inverted p wave.
What can irritate the ventricles?
Anything that reduces oxygen supply to the heart muscle: hypoxia, low perfusion, pulmonary embolus/dx, hypokalemia, mitral valve prolapse, stretch, myocarditis
Paroxysmal Atrial Tachycardia (PAT)
“Sudden” heart rate greater than 100 – Rate 150-250/min
– Identify “irritable focus”; P’ wave
PAT with Block (AV Block)
PAT with Block (AV Block)
• Greater than one P’ wave/QRS complex; 2 P’ waves for each QRS
• Suspect digitalis toxicity
Paroxsymal Atrial Tachycardia: 150-250 b/min
Paroxysmal Atrial Tachycardia
PAT with Block (AV Block)
• Greater than one P’ wave/QRS complex; 2 P’ waves for each QRS
• Suspect digitalis toxicity
Atrial tachycardia with 2:1 AV block
Multifocal Atrial Tachycardia
• 3 or more different P waves
• P-R interval varies
• Irregular ventricular rhythm
• Atrial rate > 100
• Associated with lung disease (COPD, pneumonia, ventilator theophylline), beta agonists, electrolyte abnormalities (↓K, ↓Mg) digitalis toxicity, sepsis
multifocal atrial tachycardia
3 or more different P waves
• P-R interval varies
• Irregular ventricular rhythm
• Atrial rate > 100
• Associated with lung disease (COPD, pneumonia, ventilator theophylline), beta agonists, electrolyte abnormalities (↓K, ↓Mg) digitalis toxicity, sepsis
MAT
3+ different P’ waves
rate > 100 bpm
PR intervals of varying lengths
MAT
3 or more different P waves
• P-R interval varies
• Irregular ventricular rhythm
• Atrial rate > 100
• Associated with lung disease (COPD, pneumonia, ventilator theophylline), beta agonists, electrolyte abnormalities (↓K, ↓Mg) digitalis toxicity, sepsis
tx MAT
Treatment MAT –Focus on underlying cause
- Calcium channel blocker (CCB) – nondihydropyridine – to control vent rate and dec. ectopic atrial impulses
- Diltiazem IV
- Verapamil IV (avoid if EF<40%)
- Mg SO4 IV
- Amiodarone/Adenosine
- Caution with beta blocker (pulmonary problems)
- Digitalis isn’t helpful and DC cardioversion isn’t effective
Atrial Fibrillation
Atrial Fibrillation: multiple irritable foci
• ECG
– Atrial rate >350-600/min
- undulating baseline
- no discernible P waves
- irregular RR interval (QRS complex) “irregularly irregular” ventricular rhythm
PVC
Premature Ventricular Contraction’s arise in the context of hypoxia: they do not depolarize the SA node, so sinus rhythm is present in addition to sudden large spikes. 6 or more PCVs are pathological and indicate irritated ventricles deprived of O2.
atrial flutter: 250-350 bmp
atrial flutter vs afib
Atrial flutter occurs when a “reentrant” circuit is present, causing a repeated loop of electrical activity to depolarize the atrium at a rate of about 250 to 350 beats per minute; remember the atrial rate in atrial fibrillation is 400 to 600 bpm. This produces a characteristic “sawtooth” pattern of the P waves — different from atrial fibrillation, in which the atrial rate is so fast that the P waves are not identifiable, or only coarse fibrillatory waves are seen.
CLINICAL PEARL: A narrow complex tachycardia at a ventricular rate of exactly 150 bpm is very commonly atrial flutter.
- Afib
- Aflutter
- MAT
AVNRT
Atrioventricular nodal reentrant tachycardia is the most common form of paroxysmal supraventricular tachycardia, or PSVT, in adults. AVNRT occurs when a reentrant circuit is present within the AV node itself. In this situation, there are two separate conduction pathways within the AV node instead of just one (present in about 5% of the general population).
Atrioventricular nodal reentrant tachycardia: a premature atrial impulse enters the AV node: from there it triggers ventricular contraction but is simultaneously “looped” around and ends up depolarizing the atria in a retrograde manner
the most common form of paroxysmal supraventricular tachycardia, or PSVT, in adults. AVNRT occurs when a reentrant circuit is present within the AV node itself. In this situation, there are two separate conduction pathways within the AV node instead of just one (present in about 5% of the general population).
AVNRT: the N mnemonic
mnemonic: av-NO P-rt
AVNRT
AV Reentrant Tachycardia (AVRT)
- occurs when a reentrant circuit is present outside of the AV node through an abnormal conduction pathway that connects the atrium to the ventricles. This pathway is termed an “accessory pathway” or a “bypass tract.” The presence of this congenitally abnormal accessory pathway is seen in Wolff-Parkinson-White (WPW) syndrome.
- If an action potential is able to traverse the accessory pathway and then return retrograde through the AV node ― or vice versa ― a reentrant circuit can be created, resulting in AVRT.
- Findings on ECG include the following:
- A narrow complex tachycardia
- Variable findings, depending on the direction of the circuit and location of the accessory conduction pathway
–Premature, bizarre, wide QRS
– No preceding P wave; may produce a retrograde P wave in ST segment
– ST-T wave moves in opposite direction of QRS
– Usually full compensatory pause
PVC
PVC
wolf parkinson white WPW syndrome: typical ECG finding of WPW is a short PR interval and a “delta wave.“
Wolff-Parkinson-White is characterized by the presence of an “accessory pathway” or a “bypass tract.”: connects the electrical system of the atria directly to the ventricles, allowing conduction to avoid passing through the atrioventricular node.
When an accessory pathway is present, the sinus node action potential can pass through the bypass tract before the AV node, resulting in the ventricles becoming rapidly depolarized. This is termed “pre-excitation” and results in a shortened PR interval on the ECG.
The typical ECG finding of WPW is a short PR interval and a “delta wave.“ A delta wave is slurring of the upstroke of the QRS complex. This occurs because the action potential from the sinoatrial node is able to conduct to the ventricles very quickly through the accessory pathway, and thus the QRS occurs immediately after the P wave, making the delta wave.
PVC
PVC: the “compensatory pause” that occurs shortly after it distinguishes it from other sorts of arryhthmias
3 consecutive PVCs = VTAC
PVC. note the compensatory pause.
AV Nodal Reentry Tachycardia (AVNRT)
This is a narrow-complex QRS rhythm which is quite fast. Looking closely at the last part of the QRS complex in leads V1 and V2, P waves can be seen.
This is considered a “short RP tachycardia” and is from AVNRT. Adenosine, carotid massage or vagal maneuvers can terminate this rhythm.
