Cardiac Pacing and Arrhythmias

Paced Rhythms

  • Pacer Spikes:

    • Usually present in paced rhythms.
    • On LifePak: May appear as a small arrow at the bottom of the strip.
    • Can also appear as straight lines on the lead.

  • Atrial Paced Rhythm:

    • Pacer spike appears close to where a P wave would normally be.
    • A P wave should follow the pacer spike.

  • Ventricular Paced Rhythm:

    • Pacer spike (arrow) appears before a wide, unusual QRS complex.
    • QRS is wide because the impulse originates in the ventricles.

  • Atrioventricular (AV) Sequential Pacing:

    • Both atria and ventricles are paced.
    • A pacer spike occurs before the P wave (atrial pacing).
    • Another pacer spike occurs before the wide QRS complex (ventricular pacing).

  • Atrial Pacing Only:

    • Normal-looking (narrow) QRS complex.
    • P waves may be present or absent.

  • First-Degree AV Block with Pacing:

    • Prolonged PR interval.

Ventricular Tachycardia (VTAC)

  • Definition:

    • Heart rate greater than 100 bpm.

  • Types:

    • Monomorphic: QRS complexes have a consistent shape.
    • Polymorphic: QRS complexes vary in shape.

  • Torsades de Pointes:

    • A specific type of polymorphic VTAC with a recognizable twisting pattern.
    • Associated with hypomagnesemia.
    • Can be caused by low magnesium (hypo mag).

  • VTAC Characteristics:

    • Typically regular rhythm (unless polymorphic).

Differentiating Wide-Complex SVT from VTAC

  • Concordance:

    • Positive Concordance: All QRS complexes in the V leads are upright.
    • Negative Concordance: All QRS complexes in the V leads are downward.
    • Concordance (positive or negative) suggests VTAC.

  • Axis Deviation:

    • VTAC often presents with an extreme right axis deviation.
    • Lead AVR will be positive (electrical activity moving toward AVR).
    • Lead I will be negative (electrical activity moving away from Lead I).
    • Lead V1 tends to be positive in VTAC (impulse coming up towards it from the ventricles).

  • Mnemonic: Remember these four leads and how they should be oriented in VTAC: AVR is potive; Lead one is negative. V1 is positive; V6 is negative

  • Simplified Approach (using four leads):

    • If AVR is positive, Lead I is negative, V1 is positive, and V6 is negative during a wide, fast rhythm, suspect VTAC.

  • SVT with Aberrancy:

    • SVT (Supraventricular Tachycardia) can present with a wide QRS complex if there is a bundle branch block.
    • In SVT, the electrical impulse typically travels through the AV node and back down.
    • SVT typically has a regular axis (not extreme right axis deviation).

  • Key Difference:

    • If it’s wide and fast, VTech until proven otherwise.

  • VTAC Criteria Summary:

    • Extreme right axis deviation (positive AVR, negative Lead I).
    • Positive V1, negative V6.

  • Josephson's Sign:

    • A notch near the nadir (bottom) of the QRS complex.
    • Suggestive of VTAC.

  • VTAC Treatment:

    • Vagal maneuvers or adenosine are ineffective in VTAC.

Monomorphic VTAC

  • Characteristics:

    • Regular rhythm.
    • Wide QRS complexes.
    • Uniform QRS complexes within each lead.

  • Baseline Identification:

    • Use calibration boxes to determine baseline (isoelectric line).

Polymorphic VTAC

  • Additional VTAC Criteria:
    • Extreme right axis deviation

V-Fib and Agonal Rhythm

  • Complete chaos on ECG. No discernable pattern.
    • Treatment: Shock, CPR, ACLS protocol, Amiodarone.
  • Agonal: Very slow rhythm just before death
    • CPR, Administer Epinephrine

Cardiac Axis

  • Axis refers to the general direction of electrical activity in the heart.

  • Leads I, II, and III are used to determine axis deviation.

  • Left Axis Deviation: Electrical activity is directed more towards the left side of the heart.

  • Right Axis Deviation: Electrical activity is directed more towards the right side of the heart.

  • Interpretation of Leads I, II, and III:

    • If all QRS complexes in leads I, II, and III are negative (downward), it indicates a right axis deviation.
    • To determine axis look at lead one, two and three to check the point of the r is going up or down. A line that points down is negative and one that points up is positive.

  • Relationship of Leads to the Heart:

    • Lead II provides the most elevated view and is generally positive in normal axis.
    • The axis means where electricity goes.

Determining Heart Rate

  • Using 12-lead EKG, which is a 10-second strip, count the complexes across the bottom and multiply by 6.

  • Consider testing the sample for irregular heartbeats. Use the triplicate method to test if the rhythm is irregular.

Second-degree AV Block Type 1

  • To diagnose and distinguish between an ECG follow this sequence:

    • Is the rhythm regularly regular?
    • Are there P waves? What is the morphology of each?
    • What is the P to QRS ratio?
    • Is there a variance in a PR interval?

  • Second-degree AV Block Type 1 can be identified when this ECG is present:

    • Sinus pause and positive results from questions above.

Second-degree AV Block Type 2

  • To diagnose an ECG of a patient with Second-degree AV Block Type 2 do not see variants in what you are reviewing during the questions for second-degree AV Block Type 1 diagnosis.

Differentiating Rhythms

  • There are subtle differences amongst ECG charts. In order to accurately read a patients vitals, determine a system to rely on like a flow chart to provide guidance.