Source: Sanoski CA, Bauman JL.
The Arrhythmias. In: DiPiro JT, Talbert RL, Yee GC, Matzke GR, Wells
BG, Posey LM, eds. Pharmacotherapy: A Pathophysiologic
Approach. 8th ed. http://accesspharmacy.com/content.aspx?aid=7972803.
Accessed June 30, 2012.
- Ventricular tachycardia (VT) is rapid heart rhythm (more
than 100 beats/min) originating in one of the ventricles
of the heart.
- Acute myocardial infarction (MI)
- Heart failure
- Electrolyte abnormalities (hypokalemia, hypomagnesemia)
- Drug toxicity (e.g., digoxin)
- Defined by ≥3 repetitive premature ventricular contractions
(PVCs) occurring at rate of >100 beats/min.
- Nonsustained VT self-terminates after brief duration (usually
- Sustained VT lasts >30 sec.
- Monomorphic VT has consistent QRS configuration, whereas polymorphic
VT has varying QRS complexes.
- Torsades de pointes (TdP) is polymorphic VT in which QRS complexes
appear to undulate around central axis.
- Incidence not known precisely because clinical findings
overlap with ventricular fibrillation (VF).
- Approximately 300,000 deaths per year in United States are
caused by VT or VF.
- Incidence of sudden cardiac death is 53 per 100,000 population.
- Prior MI
- Structural heart disease
- Family history of premature sudden death
- Shortness of breath
- Chest pain
- Signs: Weak or absent pulse.
Means of Confirmation
- Electrocardiogram (ECG) shows runs of ⩾3 PVCs with rate
- TdP characterized by long QT intervals or prominent U waves
- Performed if underlying causes suspected, for example:
- Electrolyte imbalances
- Digoxin toxicity
- Electrophysiologic testing may help identify patients
at increased risk for sudden death or candidates for radiofrequency
ablation of tachycardia focus.
- Identify and correct underlying causes.
- Resolve symptoms.
- Prevent recurrences.
- Avoid complications from treatment.
- If severe symptoms present, perform synchronized direct
current cardioversion (DCC) immediately to restore sinus rhythm.
- Correct precipitating factors if possible.
- If VT isolated event with transient initiating factor (e.g.,
acute MI, digitalis toxicity), long-term antiarrhythmic therapy
not needed after correction of precipitating factors.
- Most patients with acute TdP require and respond to DCC, but
TdP tends to be paroxysmal and often recurs rapidly after DCC.
- Automatic implantable cardioverter-defibrillator (ICD) highly
effective for preventing sudden death due to recurrent VT or VF.
- Acute VT
- Treat patients with mild or no
symptoms initially with antiarrhythmic drugs:
procainamide, amiodarone, or sotalol
- Lidocaine is alternative agent.
- Deliver synchronized DCC if:
- VT degenerates to VF
- Drug therapy fails
- Acute TdP
- IV magnesium sulfate drug of choice
for preventing recurrences of TdP.
- If magnesium ineffective, initiate strategies to increase
heart rate and shorten ventricular repolarization (i.e., temporary
transvenous pacing at 105–120 beats/min or pharmacologic
pacing with isoproterenol or epinephrine infusion).
- Discontinue agents that prolong QT interval.
- Correct ...