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USMLE STEP 2 and 3 > SVT > Flashcards

SVT Flashcards

1
Q

What is the most common type of paroxysmal supraventricular tachycardia (SVT)?

A

AV nodal reentrant tachycardia (AVNRT).

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2
Q

What is the primary mechanism of AVNRT?

A

A reentrant circuit within the AV node due to dual conduction pathways.

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3
Q

What is the most common risk factor for AVNRT?

A

Idiopathic, with onset typically in young adulthood.

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4
Q

What are the common clinical symptoms of AVNRT?

A

Palpitations, dizziness, dyspnea, and sometimes syncope.

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5
Q

What does the ECG show in AVNRT?

A

Narrow-complex tachycardia without visible P waves or with retrograde P waves.

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6
Q

What is the first step in evaluating a patient with tachyarrhythmia?

A

Assess airway, breathing, circulation (ABCs), secure the airway if necessary, and check hemodynamic stability.

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7
Q

What is the stepwise approach for treating narrow QRS tachycardias?

A

If stable, use vagal maneuvers, then adenosine, then beta-blockers or calcium channel blockers. If unstable, perform synchronized cardioversion.

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8
Q

What is the first-line treatment for hemodynamically unstable SVT?

A

Synchronized cardioversion, also called direct countershock (DC cardioversion).

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9
Q

What are the indications for synchronized cardioversion in SVT?

A

Severe hypotension, ischemic chest pain, altered mental status, or signs of shock (<90 mmHg SBP).

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10
Q

What is the initial management for hemodynamically stable SVT?

A

Vagal maneuvers such as Valsalva, carotid massage, or ice pack application (in children).

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11
Q

What is the next step if vagal maneuvers fail in stable SVT?

A

Intravenous adenosine.

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12
Q

What is the dosing protocol for adenosine in SVT?

A

Initial dose of 6 mg IV push, followed by 12 mg if the first dose is ineffective.

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13
Q

What is the effect of adenosine on the AV node?

A

Temporarily blocks conduction, terminating AVNRT and unmasking atrial activity.

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14
Q

What are contraindications to adenosine use?

A

Asthma due to risk of bronchospasm, and severe hypotension.

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15
Q

What are common side effects of adenosine?

A

Facial flushing, hypotension, shortness of breath, and transient bradycardia.

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16
Q

What is the next step if adenosine fails to terminate SVT?

A

Beta-blockers such as metoprolol or calcium channel blockers like diltiazem or verapamil.

17
Q

What is an alternative medication for SVT in patients with asthma?

A

Calcium channel blockers such as verapamil or diltiazem, or digoxin in select cases.

18
Q

What is the difference between AVNRT and AVRT?

A

AVNRT is due to a reentrant circuit within the AV node, while AVRT involves an accessory pathway outside the AV node.

19
Q

What are the two types of AVRT?

A
  • Orthodromic AVRT (narrow QRS).
  • Antidromic AVRT (wide QRS).
20
Q

How does atrial fibrillation appear on ECG compared to AVNRT?

A

Irregularly irregular rhythm with no distinct P waves in AFib, whereas AVNRT is regular.

21
Q

What is the hallmark ECG finding in atrial flutter?

A

Sawtooth flutter waves in leads II, III, and aVF.

22
Q

Which SVT has an irregularly irregular rhythm?

A

Atrial fibrillation.

23
Q

What are the key differences in management between AVNRT and atrial fibrillation?

A

AVNRT is managed with vagal maneuvers and adenosine, while atrial fibrillation requires rate control and anticoagulation if indicated.

24
Q

Why are P waves often absent in AVNRT?

A

They are buried within the QRS complex due to simultaneous atrial and ventricular activation.

25
Q

What ECG findings suggest orthodromic AVRT?

A

Narrow-complex tachycardia with retrograde P waves after the QRS complex.

26
Q

What ECG findings suggest antidromic AVRT?

A

Wide-complex tachycardia due to conduction through an accessory pathway.

27
Q

How do you manage sinus tachycardia?

A

Identify and treat the underlying cause rather than suppressing the rhythm.

28
Q

How does metoprolol work in SVT?

A

Beta-blockade decreases AV nodal conduction, slowing ventricular response.

29
Q

How do calcium channel blockers like diltiazem work in SVT?

A

They inhibit slow calcium channels, reducing AV nodal conduction.

30
Q

Which antiarrhythmic drug can be used in pharmacologic cardioversion of atrial fibrillation?

A

Ibutilide, a Class III antiarrhythmic.

31
Q

Which antiarrhythmic drug is used for monomorphic ventricular tachycardia?

A

Lidocaine, a Class Ib antiarrhythmic.

32
Q

What is the definitive treatment for recurrent AVNRT?

A

Catheter ablation of the slow pathway in the AV node.

33
Q

What lifestyle modifications can help prevent SVT episodes?

A

Avoiding stimulants like caffeine and alcohol, managing stress, and staying hydrated.

USMLE STEP 2 and 3 (187 decks)

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