What are Supraventricular Extrasystoles (SVE) beats?

Supraventricular Extrasystoles (SVE)

Supraventricular extrasystoles (SVEs) are premature heartbeats that originate from the atria or AV junction above the ventricles, appearing as premature P waves on ECG that may be conducted normally, with aberration, or not conducted at all to the ventricles. 1

Definition and Characteristics

SVEs, also called premature atrial complexes (PACs) or premature atrial beats, have several key features:

• Originate from ectopic foci in the atria or AV junction
• Appear as premature P waves with morphology different from sinus P waves
• Occur before the next expected sinus P wave in normal rhythm
• May be conducted to ventricles normally, with aberration (abnormal conduction), or blocked 1
• Often described by patients as "skipped beats" or irregularities in heart rhythm 1

ECG Findings

• Premature P wave with different morphology from sinus P waves
• P-P interval shorter than the basic sinus rhythm
• QRS complex may be:
  • Normal (normal conduction)
  • Wide (aberrant conduction)
  • Absent (blocked PAC) 1
• Blocked atrial bigeminy (every other beat is a non-conducted PAC) can mimic sinus bradycardia 1

Clinical Significance

SVEs have varying clinical significance depending on frequency and underlying conditions:

• Isolated SVEs: Generally benign in patients without structural heart disease
• Frequent SVEs: May predict development of atrial fibrillation, particularly in patients with risk factors 2
• SVEs in upper quartile (>14.1/hour): Show a relative risk of 4.0 for future atrial fibrillation in patients with cryptogenic stroke 2
• Short supraventricular runs (>0.2/hour): Demonstrate a relative risk of 6.9 for future atrial fibrillation 2

Diagnostic Evaluation

1. 12-lead ECG: Essential first-line test to document SVEs and assess for underlying abnormalities 3
2. 24-hour Holter monitoring: Recommended to quantify SVE burden and detect patterns 3
3. Extended monitoring: Consider in symptomatic patients when standard monitoring is non-diagnostic 3
4. Laboratory tests: Thyroid function tests to rule out hyperthyroidism 3
5. Echocardiography: To exclude structural heart disease in patients with frequent SVEs 3

Management Approach

Management depends on symptoms and frequency:

For Asymptomatic Patients:

• Reassurance if infrequent and no structural heart disease
• Follow-up monitoring in 3 months to assess SVE burden if frequent 3
• Consider monitoring in patients with cardiovascular risk factors due to increased risk of atrial fibrillation 4

For Symptomatic Patients:

1. Lifestyle modifications:

   • Reduce or eliminate caffeine, alcohol, and nicotine 3
   • Smoking cessation 3

2. Pharmacological therapy (for symptomatic relief):

   • First-line: Beta-blockers (e.g., metoprolol) 3
   • Alternative: Non-dihydropyridine calcium channel blockers (diltiazem, verapamil) if beta-blockers are contraindicated 3

3. Referral criteria for cardiology:

   • Symptoms despite beta-blocker therapy
   • Intolerance to beta-blockers
   • Associated with structural heart disease
   • High-risk features (syncope, family history of sudden cardiac death) 3

Special Considerations

• Blocked atrial bigeminy: Can mimic sinus bradycardia; careful examination of T waves for hidden P waves is important 1
• Sleep apnea: Common trigger for SVEs; screening and treatment with CPAP is recommended 3
• Monitoring after stroke: Frequent SVEs may warrant extended monitoring for atrial fibrillation in cryptogenic stroke patients 2

Follow-up

• Follow-up in 2 weeks to assess response to treatment 3
• Consider repeat extended monitoring in 3 months to assess reduction in SVE burden 3
• Early detection and monitoring of individuals with frequent SVEs and cardiovascular risk factors may help reduce risk of atrial fibrillation and stroke 4