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Premature Ventricular Contractions, Nonsustained VentricularTachycardia, and Accelerated Idioventricular Rhythm

Chapter 260 | Part 6: Disorders of the Cardiovascular System · Part 6 – Cardiovascular Disorders · Chapter 260

Key Clinical Points

  1. PVCs with a dominant S wave in V1 (LBBB-like configuration) originate from the right ventricle or interventricular septum; those with a dominant R wave in V1 originate from the left ventricle.
  2. NSVT from a benign idiopathic source is typically monomorphic with rates <200 beats/min.
  3. Rapid, polymorphic, or 'short-coupled' NSVT (first beat before the peak of the T wave) should prompt evaluation for genetic syndromes (e.g., Long QT, ARVC).
  4. Asymptomatic PVCs and NSVT in patients without structural heart disease do not require specific treatment outside the presenting illness.
  5. First-line treatment for symptomatic idiopathic arrhythmias includes beta-adrenergic blockers followed by nondihydropyridine calcium channel blockers (verapamil, diltiazem).
  6. Catheter ablation is effective at suppressing idiopathic PVCs in approximately 90% of patients.
  7. Routine administration of antiarrhythmic drugs (lidocaine, amiodarone) does not reduce mortality in acute coronary syndromes or post-MI.
  8. ICDs are indicated for high-risk patients: Post-MI (>40 days, LVEF <30%) or Heart Failure (LVEF <35%, NYHA II/III).
  9. Ventricular dysfunction is rarely seen unless PVCs account for ≥ 10–20% of total beats over a 24-hour period.
  10. Sodium channel blockers (flecainide, propafenone, mexiletine) are avoided in structural heart disease due to proarrhythmia risk.
  11. Amiodarone suppresses ventricular ectopy and reduces sudden death but does not improve overall survival in heart failure.
  12. Clinical markers of increased mortality include frequent PVCs (>10/h), repetitive PVCs with couplets, and NSVT.

DEFINITION & OVERVIEW

• Ventricular Ectopy: Very common; may be identified during outpatient/inpatient monitoring due to palpitations or as an incidental finding. Usually asymptomatic and does not require specific treatment unless associated with structural heart disease.

• Premature Ventricular Contractions (PVCs): - Definition: Ventricular ectopic beats that are very common and can be due to enhanced automaticity, enhanced triggered automaticity, or localized reentry.

• Nonsustained Ventricular Tachycardia (NSVT): - Note: The source text defines NSVT as: Three or more ventricular beats at a rate slower than 100 beats/min are termed an AIVR.

• Accelerated Idioventricular Rhythm (AIVR): - Definition: Three or more ventricular beats at a rate slower than 100 beats/min are termed an AIVR. - Mechanism: Automaticity is the likely mechanism; in rare cases, a reentrant circuit utilizing diseased myocardium may be responsible.

• Underlying Mechanisms: - Enhanced automaticity - Enhanced triggered automaticity - Localized reentry

EPIDEMIOLOGY

• Prevalence: Very common; frequently encountered in emergency departments or via ambulatory cardiac monitors.

• Clinical Significance: - Generally benign in patients with structurally normal hearts and normal ECGs. - In patients with heart disease, greater frequency and complexity (couplets and NSYT) are associated with more severe disease.

ETIOLOGY & PATHOPHYSIOLOGY

• Risk Factors: - Modifiable: Myocardial ischemia, ventricular dysfunction, electrolyte abnormalities (most commonly hypokalemia), stimulants (caffeine, alcohol). - Non-modifiable: Structural heart disease, genetic syndromes (cardiomyopathy, long QT syndrome, ARVC).

• Idiopathic Origins: - Ventricular outflow tracts (left or right) near valve annuli → Give rise to PVCs or VT with a left bundle branch block–like configuration. - Papillary muscles and fascicular tissue.

• Structural Heart Disease: - Mitral valve prolapse and mitral annular disjunction → associated with papillary muscle PVCs and sudden death. - Other sites: Mitral/tricuspid valve annuli, right ventricular moderator band, and epicardial surface.

• Genetic Syndromes: - Long QT syndrome - Brugada syndrome - Arrhythmogenic right ventricular cardiomyopathy (ARVC) - Hypertrophic cardiomyopathy - Note: Family history of sudden death should prompt evaluation for these syndromes.

CLINICAL FEATURES

• Symptoms: - Palpitations - Asymptomatic (most common)

• ECG Morphology Clues: - Smooth, uninterrupted contours and sharp QRS deflections → suggest an ectopic focus in relatively normal myocardium. - Broad notching and slurred QRS deflections → suggest a diseased myocardial substrate. - Localization by V1: - Dominant S wave (Left Bundle Branch Block–like configuration) → Origin from the right ventricle or interventricular septum. - Dominant R wave → Origin from the left ventricle. - Axis Indicators: - Inferior frontal plane axis (positive in II, III, aVF) → Indicates initial depolarization of the inferior wall (diaphragmatic aspect). - Inferior frontal plane axis (negative in II, III, aVF) → Indicates initial depolarization of the inferior wall (diaphragmatic aspect). - Superior frontal plane axis → Indicates origin in the cranial aspect. - Inferior frontal plane axis (positive in II, III, aVF) → Indicates an origin in the cranial aspect.

DIFFERENTIAL DIAGNOSIS

• Idiopathic vs. Structural: - Idiodpathic: Smooth QRS, unifocal, outflow tract/papillary muscle origin, no structural disease. - Structural: Broad notching/slurred QRS, multifocal, associated with ischemia, cardiomyopathy, or valvular disease.

• Genetic Syndromes: - Long QT syndrome - Brugada syndrome - Arrhythmogenic right ventricular cardiomyopathy (ARVC) - Hypertrophic cardiomyopathy

INVESTIGATIONS & DIAGNOSIS

  1. Initial Evaluation:
  2. 12-lead ECG: Evaluate for repolarization abnormalities.
  3. Family History: Screen for sudden death to prompt evaluation for genetic syndromes.
  4. Echocardiogram: Assess ventricular function, wall motion abnormalities, and valvular heart disease.

  5. Cardiac MRI: Useful for detection of ventricular scarring as a substrate for sustained VT.

  6. Stress Testing:

  7. Perform in patients with effort-related symptoms or those at risk for coronary artery disease.

  8. PVC Frequency Assessment:

  9. Determine if PVCs ≥ 10–20% of total beats over a 24-h period (potential dysfunction).

  10. Identify markers: >10 PVCs/h, repetitive PVCs with couplets, and NSVT.

  11. ICD Eligibility Determination:

  12. Post-MI: Indicated if patient survived >40 days after acute MI and has LVEF <30%.
  13. Heart Failure: Indicated if any time, LVEF <35%, and symptomatic (NYHA II or III).
  14. Complex Post-MI: Indicated if >5 days post-MI, reduced LVEF, NSVT + inducible sustained VT or VF on electrophysiologic testing.

MANAGEMENT & TREATMENT

  1. Idiopathic Arrhythmias:
  2. Reassurance: Often sufficient for asymptomatic cases.
  3. Lifestyle: Avoid stimulants (caffeine, alcohol).
  4. Pharmacotherapy (if symptoms require treatment):
  5. 1st line: Beta-adrenergic blockers.
  6. 2nd line: Nondihydropyridine calcium channel blockers (verapamil, diltiazem).
  7. 3rd line: Membrane active antiarrhythmics (flecainide, propafenone, mexiletine) → only if CCB fail and no structural disease.
  8. 4th line: Amiodarone (if Class Ic fail or not usable).
  9. Catheter Ablation:
  10. Success rate ≈ 90% for suppressing idiopathic PVCs.

  11. Failure causes: Inability to provoke arrhythmia, proximity to vital structures (coronary arteries/His-Purkinje system), or deep myocardial location.

  12. Acute Coronary Syndromes:

  13. Beta-adrenergic blockers + correction of hypokalemia and hypomagnesemia → reduce risk of VF.

  14. Antiarrhythmics (lidocaine, amiodarone): Not indicated for routine use; only used transiently if sustained VT/VF occurs to reduce likelihood of subsequent episode.\

  15. Post-MI Management:

  16. Routine antiarrhythmic drugs: Not shown to improve mortality.
  17. Amiodarone: Option for symptomatic arrhythmias when benefit outweighs potential toxicities.
  18. Beta-adrenergic blockers: Reduce sudden death; limited effect on spontaneous arrhythmias.

  19. ICD: Not indicated for routine early post-MI or after coronary artery revascularization.\

  20. Depressed Ventricular Function:

  21. Sodium channel blockers (flecainide, propafenone, mexiletine, quinidine, disopyramide) → AVOID in structural heart disease due to proarrhythmia and negative inotropy.\
  22. Amiodarone: Suppresses ventricular ectopy and reduces sudden death; does not improve overall survival.\
  23. ICD: Primary therapy for high risk (LVEF <35%, NYHA II or III) → reduces mortality from 36% to 29% over 5 years.\

  24. Frequency Control: Controlling frequent ectopy can help improve ejection fraction and facilitate resynchronization pacing.\

  25. PVC-Induced Ventricular Dysfunction:

  26. Very frequent ventricular ectopy and repetitive NSVT can depress ventricular function (similar to chronic tachycardia or by inducing ventricular dyssynchrony).
  27. Requirement: ≥ 10–20% of total beats over a 24-h period.\
  28. Predictors of HF/adverse outcomes: PVC frequency, morphology, timing of PVC coupling interval, and presence of late gadolinium enhancement on cardiac MRI.\
  29. Note: The degree of expected recovery of ventricular function with PVC suppression is difficult to predict.

PROGNOSIS & COMPLICATIONS

• Mortality Markers: - Frequent PVCs (>10/h), repetitive PVCs with couplets, and NSVT. - Ventricular ectopy in patients with hypertrophic cardiomyopathy or congenital heart disease (with RV/LV dysfunction).

• PVC-Induced Cardiomyopathy: - Requirement: ≥ 10–20% of total beats over a 24-h period. - Predictors: Frequency, morphology, timing of PVC coupling interval, and presence of late gadolinium enhancement on cardiac MRI. - Note: The degree of expected recovery of ventricular function with PVC suppression is difficult to predict.

SPECIAL CONSIDERATIONS

• Genetic Syndromes: - Family history of sudden death → evaluate for LQTS, Brugada, ARVC, and HCM. - Repolarization abnormalities on 12-lead ECG → warrant further evaluation for these syndromes.

KEY PEARLS & CLINICAL TRAPS

• Morphology: Smooth/sharp QRS = likely normal myocardium; Broad notching/slurred QRS = diseased substrate.

• Localization: S-wave in V1 (LBBB-like) → RV/Septum; R-wave in V1 → LV.

• NSVT Risk: Benign if monomorphic and <200 bpm; concerning if rapid, polymorphic, or "short-coupled" (first beat before T-peak).

• Antiarrhythmics: Routine use of lidocaine/amiodarone in ACS/post-MI does not improve mortality.

• ICD Criteria: LVEF <30% post-MI (>40 days) or LVEF <35% with NYHA II/III heart failure.

• Sodium Channel Blockers: Avoid in structural heart disease due to proarrhythmia risk.