Arrhythmias and EKGs

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Arrhythmias and EKGs

• Part 2

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Outline

• Sinus Arrhythmia and Sick Sinus Syndrome
• Multifocal Atrial Tachycardia
• Bigeminal Rhythms
• Preexcitation and AVRT

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Mechanisms of Arrhythmogenesis
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Sinus Arrhythmia
Braunwald's Heart Disease A Textbook of
Cardiovascular Medicine, 7th ed., 2005.
EKG Characteristics Presence of sinus P
waves Variation of the PP interval which
cannot be q attributed to either SA nodal
block or PACs When the variations in PP interval
occur in phase with respiration, this is
considered to be a normal variant. When they are
unrelated to respiration, they may be caused by
the same etiologies leading to sinus bradycardia.
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Sick Sinus Syndrome

• Characterized by a collection of symptoms and ECG
  findings due to chronic dysfunction of the
  sinoatrial (SA) node
• Chronic and severe sinus bradycardia
• Sinus pauses
• Sinus arrhythmia
• Complete sinus arrest
• Progressive development of atrial arrhythmias
  (a-flutter, a-fib, atrial tachycardia)
• Patients are usually elderly and present with
  lightheadedness and/or syncope, but it can also
  manifest as angina, dyspnea, and palpitations.
• About 50 of people with SSS also display some
  degree of dysfunction of the AV node

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Sick Sinus Syndrome
Sinus bradycardia (rate of 43 bpm) with a sinus
pause
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Etiologies of Sick Sinus Syndrome
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Tachycardia-Bradycardia Syndrome

• Common variant of sick sinus syndrome severe
  bradycardia alternates with paroxysmal
  tachycardias, most often atrial fibrillation.
• There is usually a prolonged pause in the cardiac
  rhythm following cessation of the
  tachyarrhythmia.

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Tachycardia-Bradycardia Syndrome
Braunwald's Heart Disease A Textbook of
Cardiovascular Medicine, 7th ed., 2005.
Abrupt termination of atrial flutter with
variable AV block, followed by sinus arrest with
a junctional escape beat.
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Multifocal Atrial Tachycardia
EKG Characteristics Discrete P waves with at
least 3 different morphologies.
Atrial rate gt 100 bpm. The PP, PR,
and RR intervals all vary.
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Bigeminal Rhythms

• Arrhythmias in which each normal sinus beat is
  followed by a premature contraction (PAC, PJC, or
  PVC).
• Results in a couplet rhythm which can be detected
  by pulse or auscultation.
• Generally benign

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Atrial Bigeminy
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Ventricular Bigeminy
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Preexcitation
Preexcitation is a condition characterized by an
accessory pathway of conduction, which allows the
heart to depolarize in an atypical sequence.
The most common form of preexcitation is called
Wolfe-Parkinson-White (WPW) syndrome, in which a
direct atrioventricular connection allows the
ventricles to begin depolarization while the
standard action potential is still traveling
through the AV node.
ECG Characteristics of WPW 1. Short PR
interval 2. QRS prolongation 3. Delta wave
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AV Reentrant Tachycardia (AVRT)

• In patients with WPW, a reentrant rhythm can be
  generated where the AV node serves as one arm of
  the reentrant circuit, and the accessory pathway
  as the other.

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Types of AVRT

• Orthodromic AVRT (More common) Narrow complex
  tachycardia in which the wave of depolarization
  travels down the AV node and retrograde up the
  accessory pathway.
• Antidromic AVRT (Less common) Wide complex
  tachycardia in which the wave of depolarization
  travels down the accessory pathway and retrograde
  up the AV node.

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Mechanism of orthodromic AVRT
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Mechanism of antidromic AVRT
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What is this arrhythmia?
Antidromic AVRT
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Classification Scheme for Arrhythmias
Additional important arrhythmias Multifocal
atrial tachycardia, torsade de pointes