Flashcards in Diagnosing Arrhythmias Deck (29):
What is a normal P-R interval?
• 0.12 - 0.2 seconds
• This defines SINUS RHYTHM
What might cause sinus bradycardia?
• A well trained athlete
• Vagotonic states
○ Sick sinus syndrome
○ Inferior infarct
• You see a regular ECG, just slow rate
• P waves precede QRS
What is the treatment for Sinus Tachycardia?
• Usually there is no treatment, but Beta blockers can be used
• Beta blockers are used in cases of thyrotoxicosis (graves disease)
What is seen on an ECG of Sinus Tachycardia?
• Looks normal, just fast heart rate
• Normal P waves, normal QRS waves
What causes Sinus Tachycardia?
• Sympathetic activation
○ Response to acute lung or abdominal pathology
What do you look at on the ECG to determine sinus rhythm presence?
• The P-R interval. If there is a P wave for every R wave, you are in sinus rhythm.
• If P-R interval is in normal range (0.12 - 0.2 seconds) you don't likely have block in conduction
What is the super specific finding in a first degree heart block (A-V block)?
• PR interval prolonged
• P-R interval is more than 1/2 of the R-R interval
What might cause a prolonged PR interval?
• Drug induced (beta-blockers, some calcium blockers, digitalis)
What are the findings on the ECG that suggest 3rd degree AV block?
• This is a severe conduction disease
• The P waves have no bearing on when the QRS waves happen.
• QRSs show regular rhythm but different than whatever P rhythm there is
What is the sign of a 2nd degree AV block on the ECG?
• Some P waves conduct but some do not
• May reflect conduction disease, high vagal tone or excessive effects of drugs
• If rate is too slow to allow CO to meet the body's demands can produce syncope or confusion
○ This would require pacemaker treatment
What does digoxin do?
• Digoxin inhibits sodium-potassium ATPase, which increases intracellular sodium concentration leading to increased intracellular calcium concentration.
• Autonomic effects of this include vagomimetic action and baroreceptor sensitization which lead to
• positive inotropic action,
• reduced sympathetic response and
• decreased renin-angiotensin system output (neurohormonal deactivation)
What are the specific ECG findings in ATRIAL FLUTTER?
• P waves are elongated and not symmetric
• P waves (flutter waves) at a rate of 240-320 beats/min
• Pulse can be regular or irregular
• This condition has some risk of embolic stroke due to clot formation in left atrium
• May result in rapid ventricular rates (poorly tolerated)
How do you treat atrial fibrillation?
• Anticoagulation (protect against atrial thrombi)
○ Nearly all patients are treated with anticoagulation, usually warfarin
• Rate control with drugs
○ Usually possible with Beta-blockers, calcium channel blockers (diltiazem or verapamil), or digoxin
• Cardioversion (electrical or with drugs)
What are the clinical problems associated with atrial fibrillation?
• Rapid heart rate
○ Heart failure
• Loss of atrial kick
○ Heart failure
• Atrial thrombi
○ Embolic stroke
What are the specific findings on the ECG of atrial fibrillation?
• Irregularly, irregular ventricular rhythm
• NO P WAVES
• Can be caused by:
○ Heart disease
○ Post-op stress
What are the treatments for Atrial flutter?
• Rate control with drugs
• Ablation (there's obviously somewhere that's causing an ectopic depol. Source)
Arrhythmias can come from single ectopic pacemakers. But is this common/likely?
• Nope, it's far more common to have arrhythmias triggered by re-entry mechanisms
• In a normal heart arrhythmias are self-terminating because depolarization at a junction usually meets tissue which has already been depolarized and is in a refractory period
• However, if chamber dilation and islands of fibrosis create a long and circuitous path, the depolarization can continue to find non-refractory myocardium and be sustained
In a case of junctional rhythm, what are the ECG findings?
• Narrow QRS complexes of regular spacing
• Absent or inverted P waves
○ Absent because they are buried inside the QRS
○ When seen they are inverted because atria are depolarized from an "upward" current
Atrial tachycardia is a specific example of what general mechanism that causes arrhythmias?
• Atrial tachycardia is a re-entry problem
• Results in a rapid heart rate because there is a re-entry circuit causing a depolarization before the SA node says so
• The ECG shows present, but abnormal P waves
What ECG findings are indicative of a premature ventricular contraction?
• Wide, abnormal QRS
• Very closely following T wave of the cycle before it
• No P wave
• Caused by ectopic ventricular focus
○ Conducted by slow myocardium (not purkinje fibers)
• One of the two common single palpitations in a normal heart
What are the two single palpatations in a normal heart?
• Premature atrial contraction
• Premature ventricular contraction
○ Normally noticed at rest when you aren't distracted and the low heart rate allows for re-entry
What are the ECG findings that are indicative of Ventricular Tachycardia?
• The QRS complexes are regular in spacing, not preceded by a P wave
• They are very broad and abnormally shaped with a large Q wave
• Large T wave as well
• Abnormal QRS complexes are closely bunched (tachycardia)
• LIFE THREATENING
What are the 7 steps of finding an arrhythmia?
• One - look for P wave
• Two - does P wave precede QRS
• Three - is AV heart block present?
• Four - are occasional early QRS complexes present?
• Five - are very fast, abnormal P waves present
• Six - no P waves but QRS complexes present
• Seven - no P wave and no QRS complexes present
What happens if you use the "awesome algorithm" and find that step SEVEN is true alone?
• No P wave and no QRS
• This patient will die soon
• Ventricular fibrillaiton
What happens if you use the "awesome algorithm" and find that step SIX is true alone?
• No P waves but QRS complex present
○ Atrial fibrillation
§ Irregularly irregular QRS beats often with an undulating baseline
§ QRS narrow or wide
○ Juncitonal rhythm
§ Regular rhythm with flat baseline
○ Ventricular tachycardia
§ Wide, regular, fast QRS
What happens if you use the "awesome algorithm" and find that step FIVE is true alone?
• Atrial flutter
○ P waves super fast (like 300s/min)
○ P:QRS ratio is 2,3,4:1
• Atrial tachycardia
○ Abnormal P waves in the 200s/min range with abnormal P waves before every QRS
What happens if you use the "awesome algorithm" and find that step FOUR is true alone?
• Atrial premature beats
○ QRS narrow preceded by an abnormal P wave and then only every once in a while
• Ventricular premature beats
○ Wide QRS no preceding P wave
What happens if you use the "awesome algorithm" and find that step THREE is true alone?
• 1st degree block
○ Just added time btw P wave and QRS but it's in sinus rhythm
• 2nd degree block
○ Some P waves conduct, some don't
• 3rd degree block
○ None of the P waves conduct
○ Sinus rhythm but QRS is slower than P rate
What happens if you use the "awesome algorithm" and find that step TWO is true alone?
• Normal sinus rhythm
• Sinus bradycardia (below 60bpm)
• Sinus tachycardia (above 100bpm)