Ventricular Tachycardia Flashcards
What is an arrhythmia?
Abnormal timing or pattern of the heartbeat
What are two types of ventricular arrhythmias?
Ventricular tachycardia
Ventricular fibrillation
What is the difference between ventricular tachycardia and fibrillation?
Ventricular tachycardia
- ≥3 consecutive ventricular complexes at a rate >100 bpm on an ECG
- rapid but coordinated
- can be clinically unimportant or life-threatening
Ventricular fibrillation
- rapid, disorganized rhythm without recognizable QRS complexes on the ECG
- almost always fatal
What are the two types of ventricular tachycardia? Why is this important?
Sustained VT
Non-sustained VT
Management depends on whether VT is sustained or non-sustained.
Whether there is structural difference will also determine management.
What is the difference between asymptomatic and symptomatic VT?
Asymptomatic VT
- No symptoms
- Usually non-sustained
- Often discovered during routine screening
Symptomatic VT
- palpitations, dyspnea, chest discomfort, presyncope, loss of consciousness, cardiac arrest
Does symptom severity affect impact the risk of cardiac events?
No, it more so depends on the presence of structural heart disease and whether it is sustained or non-sustained.
If patient is asymptomatic, has non-sustained VT, and no structural heart disease, what is the prognosis?
Very low risk of significant cardiac events or subsequent sustained VT
If patient is asymptomatic, has non-sustained VT, but has structural heart disease, what is the prognosis?
May indicate a risk of future serious, symptomatic, sustained VT or VF
If patient has severe symptoms, non- sustained VT, and no structural heart disease, what’s the prognosis?
Typically benign. Patients require reassurance but not necessarily antiarrhythmic therapy
Are cardiac arrests usually caused by VT or VF?
VF
VF almost always leads to cardiac arrest
Can VT lead to cardiac arrest?
Sustained VT may lead to collapse or cardiac arrest after a variable duration (1 to several minutes)
What’s the difference between sustained and non-sustained VT? How are they often managed?
Sustained VT:
- lasts ≥30 sec (>15sec for treatment purposes
- Requires immediate medical intervention
- Often associated with structural heart disease
- If there is structural heart disease, we would need antiarrhythmic drugs, implanted cardioverter defibrillator, or radiofrequency ablation
- If no structural changes, treat if there are symptoms
- If no structural changes and no symptoms, therapy is individualized
Non-sustained VT:
- lasts <30 sec
- No treatment unless symptomatic or if high likelihood of having subsequent sustained VR or cardiac arrest (Ex: ejection fraction <35% or marked QT prolongation)
What’s the difference between VT associated with structural heart disease and normal heart?
Structural heart disease:
- Usually symptomatic and high risk of sudden death or recurrence
- If asymptomatic, moderate risk of sudden death
- Magnitude of left ventricular dysfunction is the most important prognostic factor
Structurally normal heart:
- Rarely life-threatening even if symptomatic or sustained
- No therapy needed if asymptomatic and non-sustained
How should ventricular fibrillation be managed?
High risk of recurrence
Should be investigated in similar fashion as those with sustained VT
What is the difference between monomorphic VT and polymorphic VT?
Monomorphic VT:
- stable form of ventricular tachycardia (VT) with a single QRS complex shape
Polymorphic VT:
- more unstable form with a varying QRS complex shape
How can drug-induced QT prolongation increase arrhythmia risk?
When the QT interval is prolonged, the electrical repolarization of the heart takes longer, creating a vulnerable window where abnormal heart rhythms can occur, leading to ventricular arrhythmias
Where is the QT interval on an ECG? What does it represent in the heart?
The interval between the start of the QRS complex and end of the T wave.
Correlates to the time the ventricular muscle contraction starts and its relaxation.
Essentially measure cardiac muscle repolarization time
What’s the one variable that has the most influence on QT interval?
Heart rate
As heart decreases, interval lengthens
As heart rate increases, interval shortens
How do we account for these rate-related changes?
Bazett formula to help correct for these changes
The corrected QT is known as QTc
What the Bazett Formula?
QTc= QT/√RR
What is a normal QTc?
Men <470 msec
Women <480 msec
What is the risk with prolonged repolarization time?
Increases the risk of initiation of torsades de pointes (TdP)
What is torsades de pointes (TdP)?
A specific kind of ventricular arrhythmia, a form of polymorphic VT
Is TdP dangerous? More concerning than ventricular fibrillation?
TdP is usually self limiting, but it can last long enough to cause hemodynamic instability or degenerate into VF and cause sudden cardiac death
Atrial fibrillation is more concerning than TdP
What QTc increases our concern for TdP?
QTc> 500 msec or QTc increase of >60 msec from baseline
Can QT prolongation be congenital?
Yes
If patient has congenital long QT, how should they be managed?
Avoid QT- prolonging drugs
What medication that is not classified as QT-prolonging should be avoided by those with congenital long QT (type 2)?
Na-channel blocking antiseizure medications
- Carbamazepine
- Lamotrigine
- Phenytoin
What conditions can also lengthen QT interval?
- Bradycardia (especially complete heart block)
- Electrolyte abnormalities (low K, Ca, Mg)
- Hypothermia
- Hypothyroidism
Medications are the most common cause of QT prolongation.
Which antiarrhythmics are associated with QT prolongation?
Amiodarone
Disopyramide
Flecainide
Ibutilide
Procainamide
Quinidine
Sotalol
Medications are the most common cause of QT prolongation.
Which antibiotics are associated with QT prolongation?
Macrolide and quinolone
- Azithromycin
- Ciprofloxacin
- Clarithromycin
- Erythromycin
Medications are the most common cause of QT prolongation.
Which antidepressants are associated with QT prolongation?
- Citalopram
- Tricyclic antidepressants
Medications are the most common cause of QT prolongation.
Which antiemetics are associated with QT prolongation?
- Domperidone
- Ondansetron
Medications are the most common cause of QT prolongation.
Which antifungals are associated with QT prolongation?
- Fluconazole
- Itraconazole
Medications are the most common cause of QT prolongation.
Which antihistamines are associated with QT prolongation?
- Diphenhydramine
- Hydroxyzine
Medications are the most common cause of QT prolongation.
Which antipsychotics are associated with QT prolongation?
Typical
- Haloperidol
- Thioridazine
Atypical
- Olanzapine
- Quetiapine
- Risperidone
Medications are the most common cause of QT prolongation.
Which chemotherapy agent is associated with QT prolongation?
- Oxaliplatin
Medications are the most common cause of QT prolongation.
Which general anesthetics are associated with QT prolongation?
- Propofol
- Sevoflurane
Medications are the most common cause of QT prolongation.
Which opioid analgesic is associated with QT prolongation?
Methadone
Most medications that prolong the QT interval and with a proven risk of TdP rarely lead to arrhythmias. True or False?
True
Where does this risk association partially come from, if not the drug?
May be a reflection of the underlying illness. The probability of QT prolongation can also depend on risk factors
What are common risk factors for QT prolongation?
Female
Older age (>67)
Bradycardia (HR< 45)
Hypokalemia
Hypomagnesemia
Higher drug dosage
Concomitant use of other Qt prolonging medications
What is a non-pharm immediate treatment options?
Cardioversion
When would we choose cardioversion over antiarrhythmic drug therapy?
When immediate conversion to sinus rhythm is considered necessary
Ex: if sustained VT is unstable (hypotension, angina, heart failure)
For what type of ventricular tachyarrhythmia would cardioversion be considered for?
Sustained VT or VF
How do we manage the following with cardioversion:
Sustained monomorphic VT
Polymorphic VT or VF
Sustained monomorphic VT
- synchronized biphasic shock
Polymorphic VT or VF
- non-synchronized shock, repeat every 2 min PRN
What are chronic non-pharm choices? When does it come into play?
Implanted cardioverter defibrillator (ICD)
Catheter ablation
Prevention of VT/VF recurrence
When is ICD recommended?
Preferred for those with history of cardiac arrest, VF, LV dysfunction, or sustained VT due to an irreversible cause
What is a drawback with ICD?
Requires complex evaluation and follow-up
When is catheter ablation indicated?
Effective for VT arising from right or left ventricle with apparently normal hearts
If LV dysfunction, reserve for those with frequent VT recurrences despite antiarrhythmic therapy
What are pharmacological choices for immediate therapy?
Amiodarone
Procainamide
Magnesium
Lidocaine
Where does amiodarone come into play for sustained VT or VF?
VF
- shock-resistant VF
Sustained VT
- IV amiodarone terminates VT and prevents recurrence
- Most effective for electrical storm (frequent recurrence of VT/VF)
What is the typical dosing for IV amiodarone?
300mg IV bolus followed by 150 mg IV bolus PRN
or
3-5 mg/kg IV over 5-10 min followed by 0.5-1 mg/minute infusion. Can be continued for 24-48 hours if needed
What is a side effect to watch out for with amiodarone IV?
Hypotension if administered rapidly
Phlebitis (can be avoided if administered through central line)
Where does procainamide come into play for sustained VT or VF?
Slow VT and terminate tachycardia
Indicated for monomorphic VT, not polymorphic
What is the dosing for procainamide?
10-15mg/kg IV over 30-
45 min
What is a side effect with procainamide?
Hypotension if infused rapidly
Where does magnesium come into play for sustained VT or VF?
Treatment of choice for Torsades de Pointes VT
No benefit to monomorphic VT
What do we have to watch out for with magnesium?
Generally safe. Rarely causes hypotension
Where does lidocaine come into play for sustained VT or VF?
May increase the rate of return of spontaneous circulation in shock resistant VF.
What is the dosing of lidocaine?
1-1.5mg/kg IV followed by a 1-3 mg/minute infusion. If ineffective within 10-15 min. likely not effective.
What adverse effect do we have to watch out for with lidocaine?
Rarely causes hypotension.
Watch for CNS adverse events at high doses.
What are chronic therapies for prevention of VT/VF recurrence?
Beta blockers (metoprolol, atenolol, bisoprolol)
Amiodarone + sotalol
When does beta blockers come into play for chronic prevention?
Recommended for all patients in whom drug therapy is to be used (in particular those with heart failure or following an MI)
Also good for exercise, stress or ischemia induced VT
When does amiodarone and sotalol come into play?
In prevention of VT or VF.
Good to add on for high risk patients who already have an ICD implant.
Prevent ICD shocks which can be painful
If patient has multiple frequent recurrences of VT or VF (electrical storm) and resistant to beta blocker+ amiodarone, what is a last resort agent?
Mexiletine
Quinidine
Add cautiously and should only be used as a last resort
When managing patient’s QT prolonging medications, when should we exercise more caution?
QTc interval >500
or
QTc prolonged by >60 sec from baseline
It’s important to not that using 2 or more QT prolonging medications, even in high risk patients does not necessarily prolong QT. Therefore, if indicated, we should not withhold necessary medications based entirely on fear of QT prolongation.
Self-Note
When beta blockers are used with amiodarone, how do we adjust the dose of the beta blocker?
Reduce by 25-50%
Which of the beta blockers are more convenient for dosing?
Bisoprolol and atenolol are both once daily dosing
How do we manage VT if it’s exercise induced?
Beta blockers
What are the top 3 suspected drugs for QT prolongation?
- Sotalol
- Digoxin
- Citalopram
For patients on multiple QTc prolonging medications, what electrolyte parameters should they be monitoring?
Potassium
Magnesium
Summary:
If patient has non-sustained VT (<15 sec) and is asymptomatic, what is the treatment options?
No treatment, correct underlying cause (electrolyte or drug induced.
If LV dysfunction , consider beta blocker
Summary:
If patient has non-sustained VT (<15 sec) and is symptomatic with palpitations, what is the treatment options?
If exercise induced, beta blocker
If structural heart disease, amiodarone
Summary:
If patient has non-sustained VT (<15 sec) and is symptomatic with syncope, what is the treatment options?
Refer for study or prolonged ECG
Summary:
If patient has sustained VT (>15 sec) or VF and has reversible cause, what is the treatment option?
Note: no differentiation between symptomatic or not because they usually are symptomatic
Treat the underlying cause (electrolyte, drug induced or MI)
Summary:
If patient has sustained VT (>15 sec) or VF and has:
-Irreversible cause
- Structural heart disease (LV dysfunction)
- Syncope or cardiac arrest
ICD
Cardiac catheterization
Summary:
If patient has sustained VT (>15 sec) or VF and has:
-Irreversible cause
- Structural heart disease (LV dysfunction)
- No syncope
- LVEF ≤40%
ICD
Consider amiodarone or sotalol
Summary:
If patient has sustained VT (>15 sec) or VF and has:
- Irreversible cause
- Structural heart disease (LV dysfunction)
- No syncope
- LVEF >40%
Consider ICD and amiodarone
or try inducing VT
If inducible, consider ischemia if polymorphic and CAD present)
- Revascularize if necessary and give beta blocker and amiodarone
