EKG Findings and Arrhythmias – USMLE Step 2 CK exam

by / Tuesday, 08 June 2010 / Published in Internal Medicine

EKG findings and Arrhythmias

Heart Blocks:

 First-degree AV block – normal sinus rhythm with PR interval ³ 0.2ms

Second-degree, type 1 (Weckenbach) block – PR interval elongates from beat to beat until a PR is dropped

Second-degree, type 2 (Mobitz) block – PR interval fixed but there are regular non-conducted P-waves leading to dropped beats

Third-degree block – no relationship between P waves and QRS complexes.  Presents with junctional escape rhythms or ventricular escape rhythm


Atrial Fibrillation

  • The most common chronic arrhythmia
  • From ischemia, atrial dilatation, surgical history, pulmonary diseases, toxic syndromes
  • Classically, the pulse is irregularly irregular


Signs and Symptoms:

  • Chest discomfort
  • Palpitations
  • Tachycardia,
  • Hypotension + syncope


  • Control rate with b-blockers, CCB’s, and digoxin (not acutely)
  • If fibrillations last >24hr then should anticoagulate with warfarin for at least 3 weeks before cardioversion (prevents embolisms)
  • If you cannot convert to normal sinus rhythm, the patient will require long-term anticoagulation.  1st line is warfarin, 2nd line is aspirin

Cardioversion to convert to normal rhythm:

1st line – IV procainamide, sotalol, amiodarone

Electrical à shock of 100-200J followed by 360J

Atrial Flutter

  • Less stable than Afib 
  • The rate is slower than that of atrial fibrillation (approximately 250-350bpm) 
  • Ventricular rate in atrial flutter is at risk of going too fast, thus atrial flutter is considered to be more dangerous (medically slowing this rate can cause a paradoxical increase in ventricular rates) 
  • Classic rhythm is an atrial flutter rate of 300bpm with a 2:1 block resulting in a ventricular rate of 150bpm 
  • Signs and symptoms similar to those of atrial fibrillation 
  • Complications include syncope, embolization, ischemia, heart failure 

Classic EKG finding is a “sawtooth” pattern:



  • If patient is stable, slow the ventricular rate with CCB’s or b-blockers (avoid procainamide because it can result in increased ventricular rate as the atrial rate slows down)
  • If cardioversion is going to take place be sure to anticoagulate for 3 weeks
  • If patient is unstable must cardiovert à start at only 50J because is easier to convert to normal sinus rhythm than atrial fibrillation


Multifocal Atrial Tachycardia (MFAT)

  • An irregularly irregular rhythm where there are multiple concurrent pacemakers in the atria.
  • Commonly found in pts with COPD

EKG shows tachycardia with ³ 3 distinct P waves



  • Verapamil
  • Treat any underlying condition


Supraventricular Tachycardia

  • Many tachyarrhythmias originating above the ventricle
  • Pacemaker may be in atrium or AV junction, having multiple pacemakers active at any one time
  • Differentiating from ventricular arrhythmia may be difficult if there is also the presence of a bundle branch block


  • Very dependent on etiology
  • May need to correct electrolyte imbalance
  • May need to correct ventricular rate [digoxin, CCB, b-blockers, adenosine (breaks 90% of SVT)]
  • If unstable requires cardioversion
  • Carotid massage if patient has paroxysmal SVT


Ventricular Tachycardia

  • VTach is defined as ³ 3 consecutive premature ventricular contractions
  • If sustained, the tachycardic periods last a minimum of 30s.
  • Sustained tachycardia requires immediate cardioversion due to risk of going into ventricular fibrillation




  • If hypotensive or no pulse existent do emergency defibrillation (200, then 300, then 360J)
  • If patient is asymptomatic and not hypotensive, the first line treatment is amiodarone or lidocaine because it can convert rhythm back to normal


Ventricular Fibrillation

  • Erratic ventricular rhythm is a fatal condition.
  • Has no rhyme or rhythm



Signs and Symptoms:

  • Syncope
  • Severe hypotension
  • Sudden death



  • 1st line – Emergent cardioversion is the primary therapy (200-300-360J), which converts to normal rhythm almost 95% of the time
  • Chest compressions rarely work
  • 2nd line – Amiodarone or lidocaine

If treatment isn’t given in a timely matter, patient experiences failure of cardiac output and this progresses to death.

4 Responses to “EKG Findings and Arrhythmias – USMLE Step 2 CK exam”

  1. Nice post. Just found it on Yahoo. tks 4 the useful info. Keep up the excellent work :)

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  3. Angela Duque says : Reply

    This was great! Thanks for posting!! I used this to study for the Step 2CK. Also added to my own notes:
    Atrial fibrillation: if unstable patient: immediate cardioversion; if stable:(with a.fib 48 hrs)= 3-4 weeks of rate control and anticoagulation before cardioversion.

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