STEPUP Cardiovascular System: Tachyarrhythmias - Ventricular Fibrillation

Question 1

What is ventricular fibrillation?

Answer 1

1) Multiple foci in the ventricles fire rapidly, leading to a chaotic quivering of the ventricles and no cardiac output

Question 2

How do most episodes of VFib begin?

Answer 2

They begin with VT (except in the setting of acute ischemia/infarction)

Question 3

Is the recurrence of VFib high if it is not associated with acute MI? What do these patients require?

Answer 3

1) If VFib is not associated with acute MI, recurrence rate is high (up to 30% within the first year)
2) These patients require chronic therapy: Either prophylactic antiarrhythmic therapy (amiodarone) or implantation of an automatic defibrillator

Question 4

If VFib develops within 48 hours of an acute MI, what is the long-term prognosis and the recurrence rate? Do these patients require chronic therapy?

Answer 4

1) Long-term prognosis is favorable and the recurrence rate is low (2% at 1 year)
2) Chronic therapy is not required in these patients

Question 5

Is ventricular fibrillation fatal if untreated?

Answer 5

Yes

Question 6

What is the most common cause of VFib? What are two other causes?

Answer 6

1) Ischemic heart disease if the most common cause
2) Antiarrhythmic drugs, especially those that cause torsades de pointes (prolonged QT intervals)
3) AFib with a very rapid ventricular rate in patients with Wolff-Parkinson-White syndrome

Question 7

What are some clinical features of VFib regarding BP, heart sounds, pulse, and mentation? What will it lead to if untreated?

Answer 7

1) Cannot measure BP; absent heart sounds and pulse
2) Patient is unconscious
3) If untreated, leads to eventual sudden cardiac death

Question 8

How is VFib diagnosed? What will be see in this test?

Answer 8

1) ECG: No atrial P waves can be identified
2) No QRS complexes can be identified
3) In sum, no waves can be identified; there is a very irregular rhythm

Question 9

What is the treatment for VFib?

Answer 9

1) This is a medical emergency! Immediate defibrillation and CPR are indicated
a) Initiate unsynchronized DC cardioversion immediately. If the equipment is not ready, start CPR until it is
b) Give up to three sequential shocks to establish another rhythm; assess the rhythm between each

Question 10

If VFib persists after defibrillation, what should you do? What may be indicated next? What medication can you then give and how does it work? What can you do after this medication is given?

Answer 10

1) Continue CPR
2) Intubation may be indicated
3) Epinephrine (1mg IV bolus initially, and then every 3 to 5 minutes) - this increases myocardial and cerebral blood flow and decreases the defibrillation threshold
4) Attempt to defibrillate again 30 to 60 seconds after first epinephrine dose

Question 11

What are other options if defibrillation, CPR, and epinephrine fail (refractory VFib)? What are second line treatments to this medication?

Answer 11

1) IV amiodarone followed by shock - new ACLS guidelines recommend the use of amiodarone over other antiarrhythmic agents in refractory VFib
2) Lidocaine, magnesium, and procainamide are alternative second-line treatments

Question 12

If cardioversion is successful, what should you maintain continuous IV fusion of? What has become the mainstay of chronic therapy in patients at continued risk of VFib? What is an alternative to this?

Answer 12

1) Maintain continuous IV infusion of the effective antiarrhythmic agent. IV amiodarone has been shown to be the most effective
2) Implantable defibrillators have become the mainstay of chronic therapy in patients at continued risk for VF
3) Long-term amiodarone therapy is an alternative

Question 13

When should you always suspect VT in a patient?

Answer 13

A patient with a wide (>0.12 second) QRS tachycardia

Question 14

What two types of tachycardia are important to distinguish? Wide complex tachycardia in adults with a history of structural heart disease is much more likely to be what?

Answer 14

1) It is important to distinguish monomorphic VT from SVT with aberrant conduction
2) Much more likely to be VT than SVT with aberrancy

Question 15

If a patient with underlying heart disease is found to have nonsustained VT, what has shown to be the most effective treatment?

Answer 15

Implantable defibrillator

Question 16

Are cardiac arrest and sudden cardiac death synonymous? What is cardiac arrest? What is sudden cardiac death?

Answer 16

1) No
2) Sudden loss of cardiac output; potentially reversible if circulation and oxygen delivery are promptly restored
2) Unexpected death within 1 hour of symptom onset secondary to a cardiac cause

Question 17

Where do narrow complex tachycardias originate from? Where do wide complex tachycardias originate from? Which is worse and why?

Answer 17

1) Above the ventricles
2) Within the ventricles
3) Wide complex tachycardias are more ominous because they are more likely to progress to VFib

Question 18

Can drugs convert VFib by themselves? What else must be done? Does defibrillation generally work for asystole? What else must be done?

Answer 18

1) No
2) Defibrillation is key, along with CPR and epinephrine
3) No
4) Perform CPR and administer epinephrine

Question 19

What is pulseless electrical activity (PEA)? What are possible causes of PEA and how do you treat them?

Answer 19

1) Occurs when electrical activity is on the monitor but there are no pulses (even with a Doppler), and carries a grim prognosis
2) Treat possible causes (hypoxia, hypovolemia, hypotension, hyperkalemia, tamponade, tension pneumothorax, massive PE, and so on) and medicate according to ACLS guidlines