B.26 Ventricular Arrhythmia Flashcards
B.26 Ventricular Arrhythmia
define
A group of tachyarrhythmias that originate below the atrioventricular node.
B.26 Ventricular Arrhythmia
Types:
- ventricular ectopics (premature ventricular contractions)
- ventricular tachycardia (monomorphic or polymorphic)
- ventricular flutter
- ventricular fibrillation
B.26 Ventricular Arrhythmia
Premature ventricular beats
Premature ventricular beats are ectopic beats that originate from a ventricular source. They may occur due to conditions such as hypoxia, hyperthyroidism, or electrolyte imbalances.
Ectopic beat that originates from a ventricular focus
Due to hypoxia, hyperthyroidism, electrolyte abnormalitie
Premature, wide QRS complex that is not preceded by a P wave
Compensatory pause after the premature beat
B.26 Ventricular Arrhythmia
Premature ventricular beats ECG
These beats are characterized by a wide QRS complex that is not preceded by a P wave and are often followed by a compensatory pause after the ectopic beat.
B.26 Ventricular Arrhythmia
Premature ventricular beats
Etiology
Etiology
- Idiopathic causes
- Cardiovascular diseases (e.g., coronary artery disease, myocarditis)
- Electrolyte imbalances (e.g., hypokalemia, hypomagnesemia)
- Side effects of certain medications (e.g., digoxin, psychiatric drugs)
- Caffeine and alcohol consumption
B.26 Ventricular Arrhythmia
Premature ventricular beats Classification
Classification
- Monomorphic PVCs: Each PVC has the same configuration, indicating an identical origin.
- Polymorphic PVCs: PVCs exhibit different configurations, signifying multiple foci.
B.26 Ventricular Arrhythmia
Premature ventricular beats Clinical
Clinical Features
- Most patients are asymptomatic.
- May experience a skipped beat.
- If PVCs are frequent, they can lead to lightheadedness, dizziness, palpitations, or an irregular heartbeat.
B.26 Ventricular Arrhythmia
Premature ventricular beats DX
ECG Characteristics
- QRS duration ≥ 120 ms with a block-like morphology.
- PVCs often followed by a compensatory pause.
- Patterns of Arrhythmia
- Single PVC / Couplets: Two PVCs in a row.
- Bigeminy: One normal beat followed by one PVC.
- Trigeminy: One normal beat, one PVC, and then another normal beat.
PVCs are frequently identified during routine ECGs. Further evaluation is not typically necessary for asymptomatic patients.
Additional Procedures
- Only recommended for frequent, symptomatic PVCs.
- 24-hour Holter monitor.
- Exercise stress test.
- Echocardiography.
B.26 Ventricular Arrhythmia
Premature ventricular beats TX
Treatment
- Most patients do not need treatment.
- Address any underlying conditions (e.g., CAD, myocarditis).
- Only intervene for frequent and significantly symptomatic PVCs:
- Antiarrhythmic therapy (e.g., IV amiodarone).
- Catheter ablation if antiarrhythmic therapy is ineffective.
B.26 Ventricular Arrhythmia
Ventricular tachycardia
Causes:
Coronary artery disease
Myocardial infarction
Structural heart diseas
ECG findings:
- Regular, rapid rhythm
- Wide QRS complexes (≥ 3 consecutive premature ventricular beats)
Monomorphic VT (most common): single QRS morphology
Polymorphic VT: multiple QRS morphologies
- AV dissociation (P waves may or may not be discernible
B.26 Ventricular Arrhythmia
Ventricular tachycardia Etiology
- Cardiac Scars (often due to infarction; can also be iatrogenic or postoperative)
- Conduction Disorders
- Medications (e.g., digitalis, antiarrhythmics)
- Drugs Associated with Long-QT Syndrome
- Congenital Long-QT Syndrome
- Acquired Long-QT Syndrome
Antiarrhythmics
- Class Ia (e.g., quinidine, disopyramide)
- Class III (e.g., sotalol, amiodarone)
- Antibiotics (e.g., macrolides, fluroquinolones)
- Antidepressants (most tricyclics and tetracyclics, lithium)
- Antipsychotics (e.g., haloperidol)
- Electrolyte Imbalances (hypokalemia, hypomagnesemia, hypocalcemia)
- Ischemic Stroke or Intracranial Hemorrhage
- Endocrine Disorders (e.g., hypothyroidism)
- Eating Disorders (e.g., anorexia nervosa)
- In rare cases, VT may occur in individuals with healthy hearts.
B.26 Ventricular Arrhythmia
Ventricular tachycardia Pathophys
Monomorphic VT (all QRS complexes appear similar)
- Increased automaticity
- Re-entry circuit
Polymorphic VT (varied QRS complexes)
- Caused by abnormal ventricular repolarization (e.g., long QT syndrome, drug toxicity, electrolyte abnormalities)
- Decreased Cardiac Output
- Asynchronous atrial and ventricular beats combined with rapid ventricular rhythm
- Leads to reduced blood flow into the ventricle during diastole, resulting in hemodynamic compromise and symptoms such as syncope, myocardial infarction, and angina.
B.26 Ventricular Arrhythmia
Ventricular tachycardia Clinical
Clinical Features
- Often asymptomatic, particularly in nonsustained cases.
- Common symptoms of sustained VT may include:
- Palpitations
- Hypotension
- Syncope
In more severe instances:
- Chest pain/pressure (often in conjunction with myocardial infarction)
- Cardiogenic shock
- Loss of consciousness
- Progression to ventricular fibrillation
- Sudden cardiac death
B.26 Ventricular Arrhythmia
Ventricular tachycardia : Torsade de pointes tachycardia
Torsades de Pointes
- Polymorphic VT characterized by QRS complexes that seem to twist around the isoelectric line.
- The most severe complication is the progression to life-threatening ventricular arrhythmia.
- Cause: Prolonged QT interval due to congenital conditions, electrolyte imbalances, or medications.
B.26 Ventricular Arrhythmia
Ventricular tachycardia : Torsade de pointes tachycardia Acute TX
- If hemodynamically unstable: Administer defibrillation.
- If hemodynamically stable: Administer IV magnesium sulfate, beta-blockers, and consider a pacemaker.
B.26 Ventricular Arrhythmia
Ventricular tachycardia : Torsade de pointes tachycardia ECG
ECG Criteria
- Three or more consecutive premature ventricular beats (i.e., widened QRS).
- Heart rate: > 120 bpm.
- Duration:
- Nonsustained: < 30 seconds
- Sustained: > 30 seconds.
Morphology
- Monomorphic: All QRS complexes appear similar (identical origin).
- Polymorphic: QRS complexes differ (multiple origins).
B.26 Ventricular Arrhythmia
Ventricular tachycardia Torsade de pointes tachycardia DX
- Holter Monitor: Useful for identifying intermittent VT that may not appear on a single ECG.
- Patient-Activated Event Recorder: A wearable monitor that requires activation by the patient at the onset of symptoms.
- Echocardiography: Provides insights into potential causes of VT (e.g., structural heart disease, prior MI) and serves as a valuable tool for evaluating VT.
B.26 Ventricular Arrhythmia
Ventricular tachycardia Torsade de pointes tachycardia DDX
Supraventricular Tachycardia with Aberrancy (RBBB, LBBB, Wolf-Parkinson-White)
- It’s crucial to differentiate between SVT with aberrancy and VT, as treatment for both conditions differs and may influence the choice of hemodynamic agents (e.g., using AV-node blocking drugs in patients with SVT).
Signs Indicating SVT Rather Than VT:
- Age > 35 (high prevalence of prior heart disease)
- A history of prior heart disease or myocardial infarction
- AV dissociation, fusion beats, and capture beats
Signs Suggesting Bundle Branch Block in Prior ECG:
- Documentation of aberrant conduction
If there is any uncertainty regarding the diagnosis, assess the VT rhythm accordingly.
B.26 Ventricular Arrhythmia
Ventricular tachycardia Torsade de pointes tachycardia intial TX
If the patient is hemodynamically unstable (hypotension, loss of consciousness):
VT → cardioversion
If VT is nonsustained → defibrillation
If the patient is hemodynamically stable:
Antiarhythmics: typically lidocaine, procainamide, or amiodarone
Cardioversion: if medical therapy fails
In all patients, investigate and address potential causes of VT, such as:
Electrolyte imbalances (e.g., hypokalemia) → correct any identified abnormalities
Consideration of QT prolongation and any offending medications, along with digoxin in cases of digoxin toxicity
B.26 Ventricular Arrhythmia
Ventricular tachycardia Torsade de pointes tachycardia long Term TX
Implantable Cardioverter Defibrillator (ICD): the most effective therapy to reduce mortality; indicated in cases of VT that does not respond to other treatments.
Catheter Ablation
Antiarhythmics: typically Class I or III medications.
B.26 Ventricular Arrhythmia
Ventricular fibrillation define
Ventricular Fibrillation (Ventricular Fibrillation and Ventricular Flutter)
Ventricular Fibrillation (VF or “V-fit”) is a life-threatening cardiac arrhythmia marked by chaotic, high-frequency contractions of the ventricles, leading to reduced cardiac output and hemodynamic collapse.
B.26 Ventricular Arrhythmia
Ventricular fibrillation etiology
- Underlying Cardiovascular Diseases
- Most common: Coronary Artery Disease (CAD)
- Other factors: Previous Myocardial Infarction (MI), myocarditis, cardiomyopathy, severe congestive heart failure (CHF), heart valve disease
- Congenital Heart Defects
- Example: Pulmonary Atresia
- Electrophysiologic Disorders
- Wolff-Parkinson-White Syndrome
- Long-QT Syndrome, leading to Torsades de Pointes
B.26 Ventricular Arrhythmia
Ventricular fibrillation pathophys
Normal electrical conduction can be disrupted by:
- Re-entry: Chaotic, circulating excitation of the myocardium (ventricular fibrillation) resulting in multiple foci of activation, leading to insufficient cardiac output, hemodynamic collapse, loss of consciousness, and potentially sudden death.
Causes of Re-entry:
- Changes in the conduction pathway (e.g., unexcitable scar tissue from a previous myocardial infarction (MI))
- Abnormal patterns of activation:
- If the activation and recovery period of myocardial tissue exceeds the duration of an action potential (e.g., in long-QT syndrome)
- If activation occurs outside the normal sequence of myocardial activation (e.g., premature ventricular complex, PVC)
B.26 Ventricular Arrhythmia
Ventricular fibrillation clinical
Possible Early Signs:
- Chest pain
- Palpitations
- Fatigue
- Shortness of breath
- Dizziness
Ultimately: Loss of consciousness, death
B.26 Ventricular Arrhythmia
Ventricular fibrillation ECG
- Often preceded by ventricular tachycardia
- General Appearance:
- Arrhythmic, fibrillatory baseline, typically exceeding 300 bpm
- Irregular undulations with indistinguishable QRS complexes
- Absence of atrial P waves
B.26 Ventricular Arrhythmia
Ventricular fibrillation DX
Laboratory Tests:
- Cardiac enzymes
- Electrolytes
- Thyroid-stimulating hormone (TSH)
- Drug levels and toxicology screening
- Arterial blood gases
Imaging:
- Coronary angiography
- Echocardiography
- Nuclear imaging
B.26 Ventricular Arrhythmia
Ventricular fibrillation TX
Resuscitation for V-Fib:
- Advanced Cardiac Life Support (ACLS)
- If V-Fib is refractory to standard ACLS protocol, consider administering lidocaine, procainamide, or magnesium.
Post-Resuscitation Care:
- Intensive Cardiac Monitoring:
- Monitor vital signs closely and address acute metabolic imbalances (e.g., electrolyte disturbances).
- Be vigilant for therapeutic hypothermia.
- Continue antiarrhythmics as indicated, typically amiodarone or IV lidocaine.
- Assess the need for beta blockers based on patient condition.
- Consider implantation of an ICD in patients with recurrent or high-risk hemodynamically significant V-Fib.
