arrhythmias
ARRHYTHMIAS
Arrhythmia is a disorder in which the heart beats irregularly. It may be too slow or too fast.
Bradycardia is having a heart rate of <50 beats/minute that may not affect the hemodynamic status of some patients.
Clinically significant bradycardia is having a heart rate that is inadequate for the patient's current condition and may not be able to support life.
Tachycardia is having serious signs and symptoms that are often demonstrated at ventricular rates of >150 beats/minute.
Signs and symptoms related to rapid heart rate are altered sensorium, angina, shortness of breath, myocardial infarction, hypotension and other signs of shock (eg cold clammy skin, low urine output), heart failure or pulmonary congestion.

Pharmacotherapy (AV Block)

1st-Line Agent

Atropine

  • Temporizing measure for pending transcutaneous pacing
  • Reverses cholinergic-mediated decrease in HR
  • Use cautiously in patients w/ acute myocardial infarction (AMI) or acute coronary ischemia
  • May not be effective in patients who have undergone cardiac transplantation
  • Prepare for transcutaneous pacing if symptomatic bradycardia does not improve after Atropine administration

2nd-Line Agents

  • Consider in patients w/ unsatisfactory response to Atropine & as temporizing measure while awaiting pacemaker insertion

Epinephrine

  • Epinephrine infusion may be used in patients w/ symptomatic bradycardia, esp associated w/ hypotension, in whom Atropine may be inappropriate or after Atropine fails

Dopamine

  • May be used in patients w/ symptomatic bradycardia, esp associated w/ hypotension, in whom Atropine may be inappropriate or after Atropine fails
  • Dopamine infusion may be given in addition to Epinephrine or may be administered alone
  • Has both alpha & beta adrenergic agonist

Glucagon

  • Consider if the potential cause for bradycardia is overdose of a beta-blocker or Ca antagonist

Other Agents:

  • Isoprenaline, Aminophylline, Theophylline, Glycopyrrolate, Terbutaline

Pharmacotherapy (Tachycardia)

  • Pharmacotherapy is not recommended for maintenance of sinus rhythm in patients w/ advanced AV node dysfunction or sinus node disease unless they have a functioning cardiac pacemaker
  • Before starting therapy w/ antiarrhythmic agents, it is recommended to focus treatment on precipitating or reversible causes of A-fib
  • Therapy w/ a particular antiarrhythmic drug is not recommended in patients w/ A-fib who have risk factors for proarrhythmia w/ that drug
  • Patients w/ A-fib can benefit from pharmacotherapy to maintain sinus rhythm & to prevent tachycardia-induced cardiomyopathy

Adenosine

  • An endogenous purine nucleotide
  • More rapid action w/ fewer side effects than Verapamil in converting SVT
  • May be used in paroxysmal SVT w/ re-entrant circuits (including AVNRT & AVRT)
    • Used both as therapeutic & diagnostic drug
    • Favorable response to Adenosine favors likelihood of re-entry SVT
  • Also used in stable, wide-complex tachycardias w/ recurrence of a known re-entry pathway
  • Acts to delay transmission across the AV & sinus node
    • May reveal underlying atrial rhythms by slowing the ventricular response in narrow-complex AV nodal or sinus nodal re-entry tachycardia

Antiarrhythmic Agents - Class Ia

Disopyramide

  • Recommended for sinus rhythm control in patients w/ A-fib

Procainamide HCl

  • May be used for treatment of stable monomorphic VT in patients w/ preserved function
  • May be used for control of cardiac rhythm in A-fib or atrial flutter in patients w/ known pre-excitation (WPW) syndrome & preserved ventricular function
  • For AV reentrant, narrow-complex tachycardias w/ preserved ventricular function (eg re-entry SVT, junctional tachycardia) if Adenosine & vagal maneuvers fail
  • Action: Delays conduction in myocardial tissue

Antiarrhythmic Agents - Class Ib

Lidocaine

  • May be considered for, but not the drug of choice for:
    • Stable monomorphic VT in patients w/ preserved ventricular function
    • Polymorphic VT w/ normal baseline QT interval
    • Polymorphic VT w/ a prolonged baseline QT interval that suggests torsades de pointes

Quinidine

  • Recommended for sinus rhythm control in patients w/ A-fib

Antiarrhythmic Agents - Class Ic

Flecainide, Propafenone

  • Recommended for patients w/ A-fib for cardiac rate & rhythm control
  • Used for pharmacological cardioversion of patients w/ atrial flutter or A-fib
  • May be used for patients w/ symptomatic SVT or symptomatic recurrent atrial flutter w/o structural or ischemic heart disease who are not undergoing catheter ablation

Antiarrhythmic Agents - Class III

Amiodarone

  • Decreases AV conduction & sinus node function
  • Preferred over other antiarrhythmics for atrial & ventricular arrhythmias in patients who have severely impaired cardiac function
  • IV doses are recommended for heart rate control in critically-ill patients w/o pre-excitation & in hemodynam- ically stable patients w/ focal atrial tachycardia & atrial flutter
  • May be used for treatment of stable monomorphic VT & polymorphic VT w/ normal QT interval
  • Used in patients w/ stable narrow-complex regular & irregular tachycardias
  • May be effective in the treatment of shock-resistant VT or drug refractory VT
  • Oral doses are used for pharmacological cardioversion of patients w/ atrial flutter or A-fib
  • Adrenergic antagonist (alpha & beta)
    • Affects Na, K & Ca channels prolonging action potential & refractory period in myocardial tissue

Dofetilide

  • Recommended for patients w/ A-fib for cardiac rate & rhythm control
  • Used for pharmacological cardioversion of patients w/ A-fib or atrial flutter to control rhythm
  • May also be used for patients w/ symptomatic SVT w/o structural or ischemic heart disease who are not undergoing catheter ablation & unresponsive/intolerant to beta-blockers, Diltiazem, Flecainide, Propafenone, or Verapamil
  • Not recommended as an outpatient medication; may increase risk of torsades de pointes

Dronedarone

  • A non-iodinated derivative of Amiodarone, modified to reduce toxicities associated w/ Amiodarone use
  • Recently approved medication for clinically stable patients w/ history of, or current non-permanent A-fib, to prevent recurrence of A-fib & to lower ventricular rate
    • Patients w/ permanent A-fib who are on Dronedarone have increased risk of serious cardiovascular events (eg death, stroke, heart failure)
  • Based on a placebo-controlled, double-blind trial on patients in sinus rhythm w/ a history of persistent/ non-permanent or paroxysmal A-fib/atrial flutter, it showed that Dronedarone reduced the hospitalizations related to A-fib
  • Patients receiving Dronedarone should receive appropriate antithrombotic treatment
  • Based on 2 randomized trials, Dronedarone has been shown to prolong the time to recurrence of A-fib
  • Dronedarone failed to improve the acute success of electrical cardioversion in patients w/ persistent A-fib
    • In the same study, Dronedarone slows the ventricular rate in A-fib by an average of 11-13 bpm
  • Inhibits potassium currents, thus prolonging cardiac action potential & refractory periods (Class III); inhibits sodium currents (Class Ib) & calcium currents (Class IV); also inhibits adrenergic activities non-competitively (Class II)

Ibutilide

  • Class III, short-acting antiarrhythmic
  • May be used for acute rhythm conversion of A-fib or flutter of ≤48 hr duration in patients w/ normal cardiac function, w/ WPW syndrome & preserved ventricular function
  • Used for rate control in A-fib or atrial flutter in patients w/ preserved ventricular function unresponsive to Ca antagonists or beta-blockers
  • Treatment option used to restore sinus rhythm in hemodynamically stable patients w/ focal atrial tachycardia
  • Increases the duration of action potential & prolongs the refractory period of cardiac tissue

Beta-Blockers

  • Atenolol, Bisaprolol, Carvedilol, Esmolol, Labetalol, Metoprolol, Nadolol, Propranolol
  • Used in patients w/ preserved ventricular function & narrow-complex regular tachycardias that originate from a re-entry mechanism (re-entry SVT, AVNRT) or an automatic focus (junctional, ectopic or multifocal tachycardia) not controlled by vagal maneuvers & Adenosine
  • IV doses are recommended for acute A-fib; oral doses may be used for rate control in patients w/ chronic A-fib
    • IV Metoprolol may be used for rate control in patients w/ multifocal atrial tachycardia (MAT)
  • Lowers HR & BP; decreases the effects of circulating catecholamines
  • May be used as maintenance therapy in patients w/ symptomatic inappropriate sinus tachycardia (IST)

Sotalol

  • Has nonselective beta-blocking actions
  • May be used to control rhythm in A-fib or atrial flutter ≤48 hr in patients w/ pre-excitation (WPW) syndrome & preserved ventricular function
  • May be used in stable monomorphic VT, focal atrial tachycardia, & in patients w/ symptomatic SVT who are not undergoing catheter ablation
  • Action: Prolongs the duration of action potential & increases cardiac tissue refractoriness

Digoxin

  • Alternative agent for rate control
  • May be useful in patients w/ systolic CHF or hypotension in whom beta-blockers & Ca channel blockers are contraindicated & in patients w/ symptomatic SVT w/o pre-excitation who prefer not undergo or are not qualified for catheter ablation
  • Combination w/ other agents is often necessary to achieve adequate rate control
  • Exerts positive inotropic effect w/o lowering BP

Ivabradine

  • May be used in patients w/ IST to help control sinus rate & IST symptoms

Magnesium

  • Recommended for the treatment of torsades de pointes VT w/ or w/o cardiac arrest

Nondihydropyridine Ca Antagonists

  • Eg Verapamil, Diltiazem
  • Terminate reentrant arrhythmias & control ventricular response in atrial (focal & multifocal) tachycardias
    • Control ventricular rate in patient w/ preserved ventricular function & AF or atrial flutter when the duration of the arrhythmia is <48 hr
  • Used in stable regular narrow-complex tachycardias that failed to convert or uncontrolled by Adenosine or vagal maneuvers
  • Verapamil must be given only to hemodynamically stable patients w/ narrow-complex reentry/paroxysmal SVT, or arrhythmias of supraventricular origin
  • Delay conduction & increase refractoriness in the AV node
  • Avoid use in patients w/ LV systolic dysfunction, pre-excited atrial fibrillation, & decompensated heart failure

Non pharmacological therapy (Tachycardia)

  • Vagal maneuvers alone will terminate up to 25% of re-entry SVT
  • Record an ECG during each vagal maneuver
  • If cardiac rhythm is atrial flutter, slowing of the ventricular response will occur w/ vagal maneuver & display flutter waves
  • Vagal maneuvers (or Adenosine) often will suppress (AVNRT & AVRT) w/in sec

Valsalva Maneuver

  • Forced expiration against a closed glottis
    • When done in the supine position may be most efficacious

Carotid Sinus Massage

  • 5-sec pressure w/ circular motion applied on the carotid artery (1 side) at the level of the cricoid cartilage
  • Contraindicated in patients w/ carotid artery disease or carotid bruit on examination
  • Use w/ caution in the elderly & in patients w/ prior stroke
  • Stimulates the baroreceptors resulting in a reflex increase in vagus nerve activity
  • Slows AV node conduction

Others

  • Apply an ice pack on the face
  • Elicit oculocardiac reflex by applying non-rotating pressure on the eyeball over closed eyelid for 10-20 sec

Pacing

  • May be required if there is a risk of asystole, patient is unstable & unresponsive to Atropine

Transcutaneous Pacing

  • Prepare for immediate transcutaneous pacing in patients who fail to respond to Atropine or are hemodynamically unstable
  • Recommended for severely symptomatic patients, esp in Type II 2nd degree or 3rd degree AV block

Transvenous Pacing

  • Performed if transcutaneous pacing fail

Electrical Cardioversion

Synchronized Electrical Cardioversion

  • Delivered in time (synchronized) w/ the QRS complex
  • Recommended in unstable conditions of SVT due to pre-excitation, re-entry, A-fib, atrial flutter & regular VT
  • Do not attempt electric or pharmacologic cardioversion in patients w/ AF at risk for cardioemboli, unless the patient is unstable or there is documented absence of left atrial thrombus by transesophageal echocardiogram (TEE)
  • Shock dose used is lower than dose used for unsynchronized shocks (ie energy used for attempted defibrillation)
  • Conscious patients should be anesthetized or sedated prior to cardioversion
  • Cardioversion will not prevent subsequent arrhythmias & can trigger thromboembolism
  • Serial shocks are inappropriate for self-terminating A-fib that recur w/in hr or days (recurrent paroxysmal A-fib)
  • Recurrent episodes must be treated w/ drugs

Recommended Initial Dose for Cardioversion:

  • A-fib: 120-200 J w/ biphasic waveform; 200 J monophasic waveform
  • Atrial flutter & other SVTs: 50-100J monophasic damped sine (MDS) waveform
  • Monophasic VT: 100 J monophasic waveform
    • Increase subsequent shock doses as needed
  • Polymorphic VT: treat as ventricular fibrillation w/ high energy unsynchronized shocks

Unsynchronized Electrical Cardioversion

  • If cardiac rhythm is irregular & it is not possible to synchronize a shock, use high-energy unsynchronized shocks (dose for defibrillation)
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