Chapter 10+11 notes

Ventricular Arrhythmias

Overview

  • Definition: Ventricular arrhythmias refer to abnormal electrical activity originating from either ventricle.   - Characteristics:
        - Early firing of ectopic pacemaker cell.
        - Depolarization of ventricles is unorganized/chaotic.

  • Types of Ventricular Arrhythmias:
      - Premature ventricular contraction (PVC)
      - Ventricular tachycardia
      - Accelerated idioventricular rhythm
      - Ventricular flutter
      - Ventricular fibrillation

Premature Ventricular Contractions (PVCs)

  • Definition: PVCs are ectopic stimuli originating below the AV junction, often characterized by:   - Described as "skipped beats" or "palpitations".   - Ventricles depolarize before the SA node can initiate an impulse.   - Typically, there is no atrial depolarization occurring.   - Usually results from enhanced automaticity of the ventricles.

  • Appearance on ECG:
      - Exhibits a wide obtuse QRS complex, demonstrating early ventricular depolarization prior to the next normal sinus rhythm.
      - The T wave is in the opposite direction of the R wave.
      - P wave is not visible.
      - No double R wave is seen as in bundle branch block (BBB).

Figure 10-1 Premature Ventricular Contraction

  • Key features:
      - The QRS complex is noticeably different from sinus beat QRSs.
      - Absence of visible P wave.
      - T wave is in the opposite direction of the main QRS deflection.

Compensatory Pause

  • Description:
      - Following a PVC, there is a short duration without electrical activity known as a compensatory pause.
      - This pause allows ventricles to repolarize before the next sinus beat.   - Key Relationship:
        - The distance from the pre-PVC sinus beat to the PVC, plus the distance from the PVC to the post-PVC sinus beat, should equal the distance of two normal R-R cycles.

Clinical Considerations for PVCs

  • PVCs vs. Bundle Branch Blocks (BBB):
      - Confusion may arise between PVCs and BBB.     - Key distinctions:
          - Rhythm: BBB is consistent, each QRS complex is the same, unlike PVCs.       - P wave Presence: Every QRS in BBB will have a corresponding P wave, while PVCs will not.       - Complexity: BBB rhythms can include PVCs.

PVC Patterns

  • Couplets:
      - Two identical PVCs occurring in succession from the same ectopic foci (unifocal) before the SA node can initiate a sinus impulse.

  • Nonsustained Ventricular Tachycardia:
      - Involves three or more unifocal PVCs in sequence lasting less than 30 seconds.   - Also referred to as a "salvo" or "burst" of PVCs.

  • Multifocal PVCs:
      - Different PVCs appearing within the same lead, indicating activation from various ectopic foci within the ventricles.

  • Ventricular Bigeminy:
      - Alternating PVCs with sinus beats.
      - Originates from an irritable ectopic foci firing repeatedly, with all PVCs being identical.

  • Ventricular Trigeminy:
      - Presence of one PVC every third beat, with all PVCs being identical.

  • Ventricular Quadgeminy:
      - One PVC every fourth beat; all PVCs are identical.

  • R on T Phenomenon:
      - Occurs when the R wave of a PVC coincides with the T wave of the preceding sinus beat, posing a potential risk of leading to ventricular tachycardia or fibrillation.

Causes of PVCs

  • In Absence of Organic Heart Disease:
      - Factors leading to sympathomimetic changes in the central nervous system, such as:     - Idiopathic PVCs in healthy individuals (no identifiable cause).
        - Caffeine.
        - Stress.
        - Exhaustion.
        - Smoking.

  • In Presence of Organic Heart Disease:
      - Myocardial ischemia.   - Myocardial infarction.

Treatment of PVCs

  • General Approach:
      - Benign isolated PVCs in healthy individuals typically require no intervention.
      - Focus on lifestyle management strategies, targeting stress and caffeine.

  • Pharmacologic Management:
      - Initiated if PVCs are symptomatic/significant.     

    • - Medication Classes:

      •  - Class I: Sodium-channel blockers - decrease Na$^+$ entering cells, increasing time for depolarization.       

      • - Class II: Beta-blockers - block the effects of epinephrine.       

      • - Class III: Potassium-channel blockers - decrease K$^+$ efflux, increasing repolarization and refractory period.       

      • - Class IV: Calcium-channel blockers - inhibit Ca$^{2+}$ entry, slowing the SA node action potential and contractility.       

      • - Class V: Adenosine - inhibits calcium entry into cells, thereby slowing action potential.

  • Advanced Interventions:   - Catheter ablation - either burning or freezing the problematic cell.   - Electrolyte replacement therapy to correct imbalances.

Monomorphic Sustained Ventricular Tachycardia

  • Description:
      - Characterized by a series of monomorphic PVCs lasting longer than 30 seconds.     - Variations:
          - Slow sustained VT: Often asymptomatic.
          - Rapid sustained VT: Can be life-threatening; may progress to ventricular fibrillation and cardiac arrest.     - Note: Most instances of VT are associated with serious cardiovascular disease.

  • Appearance on ECG:
      - Every beat presents a wide QRS complex with a T wave inversely related to the QRS.
      - All beats are identical and demonstrate a regular rhythm.   - P waves are generally not visible, while the ventricular rate usually exceeds 100 bpm, potentially reaching up to 250 bpm.

  • Clinical Significance:
      - Symptoms arise from compromised cardiac output, resulting in hypotension, dyspnea, syncope, and angina, or potential acute myocardial infarction.

  • Treatment Options:
      - Administering oxygen therapy.
      - Utilization of antiarrhythmic medications.
      - Cardioversion or defibrillation may be indicated, depending on the situation.

Ventricular Fibrillation (VF)

  • Definition:
      - A very rapid, disordered arrhythmia that originates in the ventricles.   - This is the most common arrhythmia pattern observed in cases of cardiac arrest.

  • Characteristics:   - Exhibits no identifiable waveforms (absence of P waves or QRS complexes).
      - There is no cardiac output, resulting in immediate unconsciousness and a pulseless state.

  • Treatment:
      - Immediate unsynchronized defibrillation is required to restore normal cardiac rhythm.

Ventricular Tachycardia and Flutter Rates

  • Ventricular Tachycardia: > 100 beats per minute

  • Ventricular Flutter: 250 - 350 beats per minute

  • Ventricular Fibrillation: > 350 beats per minute

Catheter Ablation

  • Approach:
      - Involves the use of a catheter to target abnormal electrical signals through electrical ablation techniques.   - A catheter tip delivers a burst of electrical energy to disrupt abnormal conduction pathways in either the left or right atrium.

Cardioversion vs. Defibrillation

  • Cardioversion:   - Context: Elective procedure, typically performed on a conscious patient after sedation.
      - Procedure Details:
        - Synchronized with the QRS complex.
        - Energy delivery between 50 - 200 Joules.
        - Informed consent is required.

  • Defibrillation:   - Context: Emergency intervention for V-Fib/V-Tach with absent cardiac output.
      - Procedure Details:
        - Initiates with 200 Joules, scalable up to 360 Joules.
        - Typically performed on an unconscious patient.
        - Continuous EKG monitoring during the process is essential.

  • Atrial Fibrillation and NFL Players

    Study Overview

    • Key Findings: Former NFL players demonstrate a higher risk of atrial fibrillation (AFib) compared to non-players.   - Risk of AFib: Nearly six times higher in ex-players compared to men of similar age with no NFL experience.   - Despite lower overall cardiovascular risk factors, ex-players showed significant AFib prevalence.

    Research Context

    • First study linking AFib with high-strength sports, indicating a need for ongoing vigilance and screening for AFib among former NFL players.

    • Authors’ Insights: Dr. Dermot Phelan emphasized many athletes were symptom-free yet should undergo preventive treatments like blood thinners.

    Mechanism of AFib

    • Definition: AFib occurs when electrical impulses in the atria fire erratically leading to quivering, blood pooling, and risk of clot formation, which can cause strokes.

    • Potential changes include increased heart chamber size and wall thickness due to prolonged strength training.

    Study Demographics

    • Participant Comparison:   - Ex-NFL Players: 460 studied, with 5% diagnosed with AFib.   - Control Group: 925 non-players, only 0.5% had AFib.   - Demographics included both groups being mainly middle-aged with half being African American

    Structural Heart Changes in Football Players

    Long-Term Effects of Football

    • Research Presentation: Findings presented at the American College of Cardiology's 67th Annual Scientific Session.

    • Evidence points to structural heart changes and an increased risk of heart rhythm disorders, particularly AFib among former professional players.

    Risk Statistics

    • Former NFL players: Over five times greater risk for heart rhythm disorders than the general population.

    Sudden Cardiac Arrest (SCA)

    Overview of SCA

    • Sudden Cardiac Arrest: The heart stops unexpectedly due to electrical malfunction.   - Incidence: 1 in 50,000 athletes; 150 cases per year across 8 million athletes.   - NCAA statistics show 1 in 60,000 athletes, translating to 8 cases per year, with NCAA basketball incidents at 1 in 20,000.

    Athlete's Heart vs. Normal Heart

    Differences in Cardiac Structure

    • Athlete's Heart demonstrates:   - Thickened Heart Muscle   - Enlarged Left Ventricle

    Hypertrophic Cardiomyopathy (HCM)

    Definition and Genetic Implications

    • HCM is a genetic condition leading to thickening of the heart muscle, affecting 1 in 200-500 people.   - Causes abnormal heart function and may lead to arrhythmias.

    Exercise Recommendations

    • Mild to moderate exercise is encouraged.   - High-intensity activities may be suitable after expert cardiologist evaluation.   - Personalized exercise programs recommended along with hydration strategies and emergency action plans.

    Treatment and Emergency Preparedness

    • AEDs should be accessible within 3-5 minutes in athletic settings.

    • Training in CPR and AED use is vital for coaches and athletic staff.

    Supraventricular Arrhythmias: Overview

    Definition and Types

    • Supraventricular Arrhythmia: Abnormal electrical activity in atria or AV nodal regions, excluding the SA node, with heart rates exceeding 100 bpm (can be up to 300).   - Types include:     - Premature Atrial Contractions (PACs)     - Premature Junctional Contractions (PJCs)     - Atrial Flutter     - Atrial Fibrillation

    Premature Atrial Contractions (PACs)

    Description

    • Commonly benign, arising from any atrial site, resulting in early beats in both healthy and ill hearts.

    ECG Characteristics

    • Appearance: PACs present with a P wave differing in shape or size from the sinus P wave and an accompanying QRS complex.

    • Patterns: Include couplets, bigeminy, trigeminy, quadrigeminy, and atrial tachycardia.

    Causes and Treatment

    • Triggers: Include stress, caffeine, fatigue, nicotine, and electrolyte imbalances.

    • Management: Smoking cessation, limiting caffeine, potassium replacement, pharmacologic treatments, or catheter ablation.

    Premature Junctional Contractions (PJCs)

    Origin and ECG Appearance

    • PJCs stem from the AV node, possibly occurring when the SA node is not functioning correctly.

    • ECG Appearance: May lack P waves or exhibit inverted/retrograde P waves.

    Treatment Overview

    • Generally benign and do not require specific treatment. Junctional rhythms can manifest with varying heart rates:   - Junctional rhythm: HR 40-59 bpm   - Accelerated junctional rhythm: HR 60-100 bpm   - Junctional tachycardia: HR > 100 bpm, may necessitate pharmacological intervention.

    Atrial Flutter

    Characteristics

    • ECG Appearance: Recognized by a “saw tooth” pattern in the waves, with variable R-R intervals depending on AV block consistency.

    • Management: Treated with antiarrhythmic agents, adenosine for heart rate control, or synchronized cardioversion in emergencies.

    Atrial Fibrillation

    Overview

    • Most common arrhythmia, arising in both healthy and diseased hearts.   - Can lead to serious complications including embolic stroke and tachycardia-induced cardiomyopathy.

    Pathophysiology

    • Mechanism: Chaotic firing in the atria at rates of 300-500 bpm with ineffective atrial pumping, resulting in clotting risk and symptoms like activity intolerance, dyspnea, and palpitations.

    • ECG Appearance: Wavy baseline with no clear P waves, alongside irregular R-R intervals.

    • Atrial fibrillation can present as paroxysmal or permanent.

    Risk Factors

    • Advanced age, enlarged atria, stress, fatigue, dehydration, and excessive intake of alcohol, caffeine, or stimulants.

    Pharmacologic Treatment

    • Anticoagulants (e.g., Heparin, Warfarin(Coumadin)), specific lab tests (INR) to monitor efficacy.

    • Antiarrhythmic options and potential for permanent pacemaker implantation if indicated.

    Anticoagulant Side Effects

    • Common side effects include bruising, hematuria, excessive menstrual bleeding.   - Blood thinning methods explored, including dietary adjustments (Vitamin K considerations).

    Conclusion and Next Steps

    Additional Topics

    • Further exploration of sleep apnea’s effects on cardiovascular health, signs, risk indicators, and CPAP use.