cardio day 2

Conduction Pathways of the Heart

• The electrical impulse travels through the bundle of His and into the ventricles.
• It can produce an early contraction, leading us to analyze P waves and QRS shapes to infer the presence of a premature atrial contraction (PAC).

Identifying PACs

• PACs can be diagnosed based on:
  • Shape: Broad and irregularly shaped.
  • Timing: Occurs earlier than expected in the rhythm cycle.
• After a PAC, ventricular capture occurs, leading to a contraction.
• A compensatory pause follows, allowing the SA node to reset and regain control of the heart rhythm.

Compensatory Pause

• A period of electrical delay after a PAC.
• It is essential for the atrial system to reset and for the SA node to take over the pacing again.

Sinus Block vs. PAC

• During analysis, observe whether a sinus block is possible if pacing does not follow the norm.
• Key indicators of PAC include:
  • Modified QRS complexes and distinct morphology of P waves that differ from other T waves observed.

Atrial Rhythms

Ectopic Atrial Rhythm

• Characterized by:
  • Atrial and ventricular rates both being less than 100 bpm.
  • Abnormal morphology in the P wave, signaling origin is outside the sinus node.
• Potential causes include:
  • Ischemia, digoxin toxicity, and atrial scarring.

Focal Atrial Tachycardia

• Similar to ectopic atrial rhythm, but the rate is greater than 100 bpm, reflecting tachycardia with the same abnormal P wave morphology.
• Channels all impulses from the same ectopic zone in the atrium, thus P waves appear similar but different from normal.

Wandering Atrial Pacemaker

• Irregularly irregular rhythm with a rate of less than 100 bpm.
• Distinguishing feature:
  • Three or more different morphologies (shapes) of P waves pointing to multiple ectopic pacemaker foci within the atria.
• Conducts QRS complexes but with irregular P wave appearances.

Multifocal Atrial Tachycardia

• The fast counterpart to wandering atrial pacemaker; occurs when the heart rate exceeds 100 bpm.
• Exhibits the same characteristics but at an increased rate.

P Wave Morphology

• In all rhythms discussed:
  • P waves should reflect the origin but may vary in morphology.
  • Acknowledge the one-to-one relation of P waves to QRS complexes for consistent analysis.

Summary Points on Rhythm Analysis

• PACs are single premature beats that lead to unique P wave morphology and QRS patterns.
• Compensatory pauses are necessary for the heart's rhythm normalization.
• Ectopic atrial rhythms signify disturbances in sinus node activities brought upon by various pathophysiological factors.