ACLS Prep 4

Tachyarrhythmias

• Sinus tachycardia

• Supraventricular tachycardias:

  • SVT

  • Afib

  • Aflutter.

• Ventricular tachycardia:

  • Monomorphic

  • Polymorphic

Medications for tachyarrhythmias

• Adenosine:

  • 1st dose: 6 mg IV push.

  • 2nd dose: 12 mg IV push.

• Procainamide:

  • 20-50 mg/min until suppressed.

  • 1-4 mg/min maintenance infusion.

• Amiodarone:

  • 1st dose: 150 mg over 10 mins.

  • 1 mg/min x 6 hrs maintenance infusion.

• Sotalol:

  • 100 mg (1.5 mg/kg) over 5 mins.

SInus tachycardia

Looks like NSR but faster. Increases the heart’s need for O2, decreases ventricular filling time and decreases coronary artery perfusion time.

SInus tachycardia regular or irregular

Regular.

SInus tachycardia rate

>100 bpm.

SInus tachycardia P waves

Present before every QRS, consistent in shape, may be hidden in preceding T wave if rate is rapid.

SInus tachycardia PR interval

Normal, difficult to measure if P waves are buried in T waves.

SInus tachycardia QRS complexes

Usually normal.

SInus tachycardia conduction

Normal

SInus tachycardia causes

• Can be normal response to exercise and emotions in adults.

• If persistent at rest, identify underlying cause:

  • Fever

  • Blood loss

  • Anxiety/pain

  • Heart failure

  • Dehydration

  • Anemia

  • Toxins

  • Caffeine

Supraventricular tachycardia

Tachyarrhythmias that originate above the ventricles at a rate >140 bpm.

Supraventricular tachycardia regular or irregular

Regular

Supraventricular tachycardia rate

140-300 bpm.

Supraventricular tachycardia P waves

Usually not visible, may be hidden in QRS complex or T wave but not easily seen on ECG.

Supraventricular tachycardia PR interval

Not measurable

Supraventricular tachycardia QRS complex

Usually normal unless BBB is present.

Supraventricular tachycardia conduction

Normal through ventricles.

Atrial flutter

Usually caused by reentry circuit in the right atrium. Impulse chases itself in a rapid rate.

Atrial flutter regular or irregular

Atrial rhythm is regular, ventricular rhythm can be regular or irregular due to varying AV block.

Atrial flutter rate

• Atrial: 250-350 bpm.

• Ventricular rate dependent on amount of block at AV node.

Atrial flutter P waves

F (flutter) waves. Saw-toothed. 1 F wave often buried in T wave, especially in 2:1 conduction.

Atrial flutter PR interval

FR interfal. May be consistent or varying dependent on AV block.

Atrial flutter QRS complex

Usually normal, wide if conducted with aberrancy.

Atrial flutter conduction

AV node blocks at least every other F wave and often blocks 2 or more to protect ventricles from extremely rapid atrial rate.

Atrial flutter causes

• Myocardial ischemia/infarction.

• Mitral valve disease.

• Hyperthyroidism.

• Heart failure.

• Cardiac surgery.

• Antiarrhythmic therapy for Afib.

• Obesity.

• Diabetes.

• Pulmonary disease.

• Alcohol abuse.

Atrial fibrillation

Chaotic ectopic or reentrant activity in atria causing them to quiver rather than contract.

Atrial fibrillation regular or irregular

Irregular

Atrial fibrillation rate

Atrial rate is too fast to count. Ventricular rates dependent on amount of block at AV node.

Atrial fibrillation P waves

Not present.

Atrial fibrillation PR interval

None

Atrial fibrillation QRS complex

usually normal, wide if conducted with aberrancy.

Atrial fibrillation conduction

Intra-atrial conduction is disorganized and irregular.

Atrial fibrillation causes

• Myocardial ischemia/infarction.

• Rheumatic heart disease.

• Heart failure.

• Pulmonary disease.

• Open heart surgery.

• Heart valve disease.

• Hyperthyroidism.

• Alcohol abuse.

• Hypertension.

• Stress response from illness.

Ventricular tachycardia

Ventricular rhythm faster than 100 bpm. Can be monomorphic or polymorphic. Ectopic focus or reentry circuit in ventricle. Assumes pacing responsibility of heart.

Ventricular tachycardia regular or irregular

Regular

Ventricular tachycardia rate

>100 bpm.

Ventricular tachycardia P waves

Not related to QRS.

Ventricular tachycardia PR interval

Not measurable.

Ventricular tachycardia QRS complex

Wide, bizzare. >0.12 seconds.

Ventricular tachycardia conduction

Slow through ventricles since cell-to-cell conduction.

Ventricular tachycardia causes

• Myocardial ischemia/infarction.

• Toxins:

  • Digitalis.

• Structural heart disease.

• Myocarditis.

• Recreational drugs:

  • Methamphetamines.

  • Cocaine.

• Heart failure.

Polymorphic ventricular tachycardia regular or irregular

Irregular

Polymorphic ventricular tachycardia QRS complex

Wide, bizarre. >0.12 seconds, multiple morphologies.

Polymorphic ventricular tachycardia causes

• Myocardial ischemia/infarction.

• Toxins:

  • Digitalis.

• Structural heart disease.

• Myocarditis.

• Recreational drugs:

  • Methamphetamines.

  • Cocaine.

Torsades de Pointes causes

• Congenital.

• Toxins:

  • Multiple drugs can prolong QT interval.

  • Electrolyte imbalances:

    • Magnesium.

    • Potassium.

• Subarachnoid hemorrhage.

• Right radical neck dissection.

• Hypothyroidism.

S/S of unstable tachyarrhythmias

• Heart rate >150 bpm (can only tolerate for a short time).

• Hypotension.

• Altered mental status.

• Signs of shock.

• Ischemic chest pain.

• Acute heart failure.

• Difficulty breathing.

• Dizziness.

• Lightheadedness.

Adenosine

Has vasodilatory effects and antiarrhythmic properties. Works through purinergic receptors found through the body.

• Rapid IV push over 1 second, immediately flush and elevate arm.

  • 1st dose: 6 mg IV push.

  • 2nd dose: 12 mg IV push.

• Does not terminate A-flutter or A-fib, but slows conduction through AV node allowing for rhythm identification.

• Can cause bronchospasm, do not give with asthma or COPD especially if patient is bronchospastic.

• If rhythm converts, probably reentry SVT.

  • Watch for recurrence of rhythm.

  • Consider CCB or BB.

• If rhythm doesn’t convert, probably Afluter, ectopic atrial tachycardia, sinus tachycardia, or junctional tachycardia.

• Significant blood levels of theophylline, caffeine, and theobromine may require larger doses.

• Decrease initial dose to 3 mg IV for patients taking dipyridamole or carbamazepine.

• Decrease dose to 3 mg IV with patients with transplanted hearts or after central venous administration.

  • Increased doses can prolong asystole.

• Always seen expert consultation.

Adenosine critical concepts

• Caution when using AV nodal blocking drugs for pre-excited atrial fibrillation or flutter because these drugs are unlikely to slow the ventricular rate and may even accelerate the ventricular response.

• Be careful when combining AV nodal blocking agents of varying duration, such as CCB or BB, because their action may overlap if given serially and provoke profound bradycardia.

Procainamide

• Class IA antiarrhythmic.

• Blocks fast sodium channel.

  • Interferes with rapid depolarization and decreased conduction velocity.

  • Increases duration of cardiac action potential of the Purkinje fibers.

• Suppresses reentrant tachycardias.

• Also acts as a negative inotrope and may cause:

  • Peripheral vasodilation.

  • Hypotension.

• 20-50 mg/min IV until suppressed or hypotension ensues, QRS increases >50% or maximum dose of 17 mg/kg is given.

• Maintenance infusion 1-4 mg/min.

• Avoid prolonged QT or heart failure.

Amiodarone

• Class III antiarrhythmic.

• Inhibits potassium ion fluxes during phase II and III of action potential.

• Directly acts on myocardium to delay repolarization.

  • Prolongs QT interval.

• Approved for life threatening refractory ventricular arrhythmias.

  • Use in atrial fibrillation is off label.

• Relaxes smooth and cardiac muscle, reduces afterload and preload.

• Pro Arrhythmias less frequent.

• Avoid with sinus or AV node dysfunction, lung/liver disease, prolonged QT interval, infranodal conduction disease.

• Bolus dose 150 mg over 10 mins.

• Maintenance infusion 1 mg/min for first 6 hours.

Sotalol

• Class III antiarrhythmic.

• Nonselective beta blocking agent with class III properties.

• Significant class III effects are only seen at doses >160 mg.

• Used in atrial arrhythmias and life-threatening ventricular arrhythmias.

  • Decreased defibrillation threshold.

• Indicated for stable. monomorphic VT or polymorphic VT with normal QT interval.

• Proarrhythmic potential (prolonged QT).

  • Must stay in hospital >3 days.

• 100 mg (1.5 mg/kg) IV over 5 minutes.

• Avoid in setting of systolic heart failure.

  • Increases mortality.

Synchronized cardioversion

• Treatment of choice for symptomatic (unstable) reentry SVT or VT with pulses.

• Treatment for unstable atrial fibrillation and flutter.

• Unlikely to be effective for junctional tachycardia or ectopic or multifocal atrial tachycardia.

  • Automatic focus arising from cells that are spontaneously depolarizing at rapid rates.

• Provide sedation if possible.

• Start joules at:

  • Atrial fibrillation: 200 joules.

  • Atrial flutter: 200 joules.

  • Narrow complex tachycardia: 100 joules.

  • Monomorphic V-tach: 100 joules.

  • Polymorphic V-tach: unsynchronized defibrillation.

• Recommended for:

  • Unstable narrow complex tachycardias.

  • Unstable monomorphic VT with pulses.