Flashcards in Treatment of Arrhythmias Deck (37)
Where in the conduction pathway can bradyarrhythmias occur?
• This is the same for any conduction pathway
• Sinus Node
• AV Node
• Below the AV node
○ Right bundle?
○ Left bundle (splits into anterior and posterior)
What is meant by SINUS BRADYCARDIA
• Sinus rhythm, thus P wave before QRS
• Regular spacing
• Rate is 55bpm or slower
• PR interval 0.18 seconds (within range, so it's not a conduction issue, it's just an issue of slow firing)
What is meant by SINUS ARREST?
• Failure of sinus node discharge resulting in the absence of atrial depolarization and periods of ventricular systole
• Rate can be normal (75bpm in example)
• PR interval is normal (no conduction issue so 0.18 seconds)
• Random 2.8 second pause in example between wave forms before it resumes
What is meant by "Tachy-Brady"?
• Tachycardia-bradycardia syndrome, intermittent episodes of slow and fast rates from SA node or atria
○ Commonly associated with periods of atrial fibrillation
• Wave form -
○ Intermittent slow and fast rates
○ 43bpm during brady
○ 130bpm during tachy
○ No conduction problems and there is a presence of sinus rhythm
What is meant by CHRONOTROPIC INCOMPETENCE?
• Sinus node problem
• Inability of the heart to regulate its rate appropriately in response to physiologic stress (exertion)
• Normal heart rate quickly reaches "max" during exercise or stress then gradually goes back down
• In the disease state "max" HR is never reached and the heart rate is unstable, followed by an unusually fast drop to "resting state"
What is characteristic of a 1st degree AV block?
• AV conduction delayed, and PR interval is prolonged because of it
• The depolarization does progress through the block and there is sinus rhythm with P waves before QRS complexes
• 0.12 - 0.2 seconds is normal PR interval
○ Cutoff for prolonged is above 0.2 seconds
• 0.34 seconds is indicative of 1st Degree AV block
What type of conduction problem is alternatively named "Mobitz 1" or "Wenckebach"?
• AV block, 2nd degree type 1
• When ventricular rate is irregular (grouped beating)
• PR interval progressively elongates until P wave fails to conduct and a ventricular beat is dropped
1st Degree AV block and 2nd Degree Type 1 AV block are both examples of what kind of conduction problem?
• AV node itself, as opposed to below the AV node or in the purkinje system
What is characteristic of a Mobitz II arrhythmia?
• Type of bradyarrhythmia
• 2nd Degree AV block type 2
• Normal PR intervals
• Intermittently dropped ventricular beats
• Sometimes the P wave doesn't get through
• "skipped a beat"
What is characteristic of a 3rd degree AV block?
• P waves have little bearing of when QRS happens
• No impulse conduction from atria to ventricles
• Ventricular rate = 37bpm (ventricular escape rhythm)
• Atrial rate = 110 bpm
• PR interval is variable
What is the first step in the treatment paradigm for bradyarrhythmias?
• (before step one) Determine severity (symptoms)
• Locate and treat the underlying problem
○ Neurologic causes
○ Lyme disease
• Stop offending medications
○ Beta blockers, calcium channel blockers
○ Antiarrhythmic drugs
○ Clonidine, lithium, others
What is the long term treatment for unstable bradyarrhythmias?
• Permanent pacemaker implantation
What is the acute treatment for unstable patients with bradyarrhythmias?
• Beta agonists
○ IV dopamine or IV isoproterenol
• Transcutaneous pacing
• Temporary transvenous pacing
What are the bradyarrhythmia take home points?
• Determine level of block responsible
○ SA node
○ AV node
• Let symptoms and infranodal disease dictate treatment
• Treat potential reversible causes
• Acutely stabilize patients
• Long term = pacemaker
What are the two places that tachyarrhythmias can develop?
• Above the ventricle or in the ventricle
• Above - supraventricular tachycardias (SVT)
○ Usually a narrow QRS
• Below - Ventricular Tachycardia, Ventricular fibrillation
○ Usually a wide QRS
What is characteristic of atrial fibrillation?
• AF or Afib
• Irregularly irregular
• No discernable p waves
• Super jagged and bumpy lines before QRS complex
What is meant by MAT?
• Multifocal atrial tachycardia
• 3 or more p-wave morphologies
• Associated with lung disease, hypoxemia
What is characteristic of MAT?
• The P wave is separated into little jagged bumps
• 3 or more of these bumps is indicative of the multiple areas of action potential generation
What is the acute treatment paradigm for supraventricular tachycardias?
• If the pt is unstable, shock them back into sinus rhythm
• For stable pts, treat with rate control, antiarrhythmics or cardioversion
What does cardioversion mean?
• Cardioversion is a medical procedure by which an abnormally fast heart rate (tachycardia) or cardiac arrhythmia is converted to a normal rhythm using electricity or drugs. Synchronized electrical cardioversion uses a therapeutic dose of electric current to the heart at a specific moment in the cardiac cycle
What is meant by AVNRT?
• Atrioventricular Nodal Reentry Tachycardia
• Re-entrant circuit is within the AV node
What is characteristic of AVNRT?
• Atria and ventricles depolarize simultaneously
• The P wave is then buried within or on the tail end of the qrs complex
What is the treatment for AVNRT?
• Atrioventricular nodal re-entry tachycardia
• Acute termination with adenosine or vagal maneuvers
• Chronic treatment with catheter ablation
• Meds are not the optimal chronic treatment choice
* ablation is radio-frequency and slows the pathway
What are the three accessory pathway mediated tachycardias?
If you have a tachycardia that has 1:1 p-waves to QRS complexes, what 6 things could it be that we discussed?
• ST (is this SVT?)
• AVNRT - AV nodal reentry tach
• AVRT - atrioventricular reentry tach (not nodal)
• AFL - atrial flutter
• AT -
What is the treatment for the three SVTs we discussed?
• SVT = supraventricular tachycardia
○ Individualized treatment
○ Pill in pocket (only for symptoms), these are antiarrhythmic drugs
○ Long term = beta blockers, calcium channel blockers (slow AV node), class 1 drugs to suppress hotspots or premature beats
○ Catheter ablation is the "cure"
What are the 5 "c"s of atrial fibrillation management?
• Cause - reverse it!
• Control Rate - calcium channel blocker, beta blocker
• (anti)Coagulation - ALWAYS
• Control rhythm (consider) - chronic?
• Cathetar ablation (consider) - if it returns
What are the COMMON cuases of atrial fibrillation?
• Mitral valve disease
• Alcohol (holiday heart)
• Lone AF
What are the "other" more concerning causes of atrial fibrillation?
• Congenital heart disease
• Pulmonary embolism
• Cardiac surgery
• Atrial myoxoma
What are the 5 drugs you can use for rate control?
• Beta-blockers (class II)
• Digoxin (ATPase blocker, leads to increased intracellular calcium, increased parasympathetic tone, increased inotropy)
• Verapamil (class IV)
• Diltiazem (class IV)
○ Especially in decompensated heart failure
What is the treatment paradigm concerning rhythm control?
• Acute = cardioversion
○ Less successful
○ Doesn't require sedation
○ Class III - ibutilide, amiodarone, dofetilide, sotalol
○ Class 1C - flecainide, propafenone
○ DC shock has up to 90% success rate
○ Day procedue in hospital
○ Does need sedation
As for rhythm control, what is contraindicated for use in CAD?
• Class 1c agents
• Also can't use these in structural heart disease
What is the treatment paradigm for atrial flutter?
• Super similar to Atrial fibrillation
• If anything, cathetar ablation is even better (95% success)
If a patient has had a previous MI, or has CAD, what is WCT ALWAYS considered untill proven otherwise?
• WCT = wide, complex tachycardia (wide QRS)
• In CAD, 90% of the time it's ventricular tachycardia
What is the treatment paradigm for Ventricular tachyarrhythmias?
○ Amiodarone, lidocaine, procainamide
○ Class III drugs (remember, 1c contraindicated in CAD)
○ Treat underlying cuases
When is a defibrillator needed in ventricular tachycardias?
• Secondary prevention
○ Pt has already had cardiac arrest not caused by some reversible underlying cause
• Primary prevention
○ Pt is at risk for cardiac arrest but hasn't had it yet
○ Ischemic heart disease
○ Structural diseases - HCM, cardiac sarcoid, congenital heart disease, ARVC