Ventricular Tachycardia Flashcards by Jbun L

What is an arrhythmia?

Abnormal timing or pattern of the heartbeat

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What are two types of ventricular arrhythmias?

Ventricular tachycardia
Ventricular fibrillation

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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

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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.

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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

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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.

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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

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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

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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

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Are cardiac arrests usually caused by VT or VF?

VF almost always leads to cardiac arrest

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Can VT lead to cardiac arrest?

Sustained VT may lead to collapse or cardiac arrest after a variable duration (1 to several minutes)

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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)

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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

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How should ventricular fibrillation be managed?

High risk of recurrence
Should be investigated in similar fashion as those with sustained VT

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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

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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

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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

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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

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How do we account for these rate-related changes?

Bazett formula to help correct for these changes

The corrected QT is known as QTc

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What the Bazett Formula?

QTc= QT/√RR

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What is a normal QTc?

Men <470 msec
Women <480 msec

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What is the risk with prolonged repolarization time?

Increases the risk of initiation of torsades de pointes (TdP)

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What is torsades de pointes (TdP)?

A specific kind of ventricular arrhythmia, a form of polymorphic VT

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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

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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?

1. Sotalol 2. Digoxin 3. 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