Approach to Supraventricular Arrhythmias¶

Chapter 253 | Part 6: Disorders of the Cardiovascular System · Part 6 – Cardiovascular Disorders · Chapter 253

Key Clinical Points¶

Supraventricular tachycardia (SVT) is defined by a narrow QRS complex (<120 ms), indicating ventricular activation via the Purkinje system.
Physiologic sinus tachycardia is triggered by external factors (exertion, stress, stimulants, illness); pathologic SVT occurs without identifiable triggers.
AVNRT is the most common paroxysmal sustained tachycardia in healthy young adults and is more common in women.
Atrial fibrillation is the most common sustained cardiac arrhythmia in older adults.
Adenosine (6 or 12 mg) is the first-line pharmacologic agent for terminating AV nodal-dependent SVT and serves as a diagnostic tool.
Vagal maneuvers and carotid sinus massage (CSM) are initial non-pharmacologic interventions to achieve AV block; CSM requires caution in patients with suspected carotid atherosclerosis.
Ventricular preexcitation on ECG suggests an accessory pathway (e.g., Wolff-Parkinson-White syndrome).
Multifocal atrial tachycardia (MAT) is typically associated with pulmonary disease during acute exacerbations.
AV node blockade provides a critical diagnostic differentiation: if the atrial rate continues despite AV block, the arrhythmia is non-AV nodal dependent (e.g., atrial flutter or atrial tachycardia).
Asymptomatic supraventricular arrhythmias often do not require treatment or further evaluation.

1. DEFINITION & OVERVIEW¶

• Definition: Supraventricular arrhythmias are abnormal heart rhythms originating above the level of the ventricle (atria or atrioventricular junction). • SVT Criteria: ◦ Defined as narrow-complex tachycardia (QRS duration <120 ms). ◦ Indicates ventricular activation over the Purkinje system. ◦ QRS morphology is typically identical to sinus rhythm. ◦ Must be distinguished from Ventricular Tachycardia (VT) if a wide QRS is present due to bundle branch block or accessory pathway activation.

1.1 Classification of SVT¶

• Physiologic Sinus Tachycardia: ◦ Normal sinus mechanism precipitated by exertion, stress, exogenous/endogenous stimulants, or concurrent illness. • Pathologic Supraventricular Tachycardia (SVT): ◦ May continue despite beats failing to conduct to the ventricles (indicating AV node is not in the circuit). ◦ Atrial Origin: ◦ Inappropriate sinus tachycardia: From normal sinus node area without identifiable precipitating factors due to dysfunctional autonomic regulation. ◦ Focal atrial tachycardia (AT): Regular atrial tachycardia with defined P wave; can be sustained, nonsustained, paroxysmal, or incessant. ◦ Atrial flutter and macroreentrant atrial tachycardia: Organized atrial activity; often seen as sawtooth waves at rates >200 bpm. ◦ Atrial fibrillation: Chaotic rapid atrial electrical activity with variable ventricular rate; most common sustained cardiac arrhythmia in older adults. ◦ Multifocal atrial tachycardia (MAT): Multiple discrete P waves, typically in patients with pulmonary disease during acute exacerbations. ◦ AV Nodal Reentry Tachycardia (AVNRT): ◦ Paroxysmal regular tachycardia; P waves visible at end of QRS or not visible; most common paroxysmal sustained tachycardia in healthy young adults; more common in women. ◦ Tachycardias with Accessory Pathways: ◦ Orthodromic AV reciprocating tachycardia (AVRT): Similar to AVNRT; may show preexcitation (WPW) or be a concealed pathway. ◦ Preexcited tachycardia: Wide QRS tachycardia with morphology similar to VT. ◦ Antidromic AV reciprocating tachycardia ◦ Atrial fibrillation with preexcitation (can have rates >250/min) ◦ Atrial tachycardia or flutter with preexcitation ◦ Other Supraventricular Arrhythmias: ◦ Premature atrial contractions (PACs): Early atrial complex distinct from sinus P wave. ◦ Sinus arrhythmia: Irregular rhythm with P-P intervals varying with respiration. ◦ Accelerated junctional rhythm: Paroxysmal regular rhythm; P waves at end of QRS or not visible. ◦ Ectopic atrial rhythm: Regular rhythm, rate <100 bpm but >sinus rate, distinct P wave.

2. EPIDEMIOLOGY¶

• Atrial fibrillation: Most common sustained cardiac arrhythmia in older adults. • AVNRT: Most common paroxysmal sustained tachycardia in healthy young adults; more common in women.

3. ETIOLOGY & PATHOPHYSIOLOGY¶

• Physiologic vs Pathologic Tachycardia: ◦ Physiologic: Normal sinus mechanism triggered by external factors (exertion, stress, stimulants, illness). ◦ Pathologic: Result of dysfunctional autonomic regulation or abnormal reentry circuits. • Accessory Pathway Mechanisms: ◦ Orthodromic AV reciprocating tachycardia (AVRT): ◦ May show preexcitation during sinus rhythm (WPW syndrome) or be a concealed accessory pathway. ◦ Preexcited tachycardia: ◦ Presents as wide QRS tachycardia with morphology similar to VT.

4. CLINICAL FEATURES¶

• Common Symptoms: Palpitations, chest pain, dyspnea, diminished exertional capacity, and occasionally syncope. • Severe Presentations: ◦ Rare cases of cardiac arrest in patients with Wolff-Parkinson-White (WPW) syndrome or severe heart disease (e.g., hypertrophic cardiomyopathy). • Asymptomatic Arrhythmias: ◦ Often captured on routine ECG; most do not require treatment or further evaluation.

5. DIFFERENTIAL DIAGNOSIS¶

• Diagnostic Requirement: Obtain ECG at the time of symptoms. • Clinical Context: Diagnosis often pursued for arrhythmia-related symptoms or when ventricular preexcitation is seen on outpatient ECG.

5.1 Diagnostic Algorithm (Narrow-Complex Tachycardia)¶

Based on 12-lead ECG appearance (Figure 253-1): • Group 1: AVNRT, ORT, AT, Rarely atrial flutter. • Group 2: Atrial flutter, Atrial tachycardia, Rarely AVNRT with 2:1 block below the His bundle. • Group 3: Junctional tachycardia.

5.2 Diagnostic Effect of AV Node Blockade¶

Utilize vagal maneuvers, carotid sinus massage (CSM), adenosine, verapamil, or beta blockers to assess response. • No effect: → Suggests Fascicular VT or Inadequate dose/effect. • SVT slows: → Suggests Sinus tachycardia or Junctional tachycardia. • SVT terminated: → Suggests AVNRT, AVRT, Adenosine-sensitive AT, or Focal AT. • Atrial rate continues with AV block: → Suggests Atrial flutter or Atrial tachycardia. • Clinical Logic: ◦ If atrial rate continues with no effect → SVT is likely non-AV nodal dependent (e.g., focal AT). ◦ If SVT slows or terminates with AV block → SVT is AV nodal dependent (e.g., AVNRT, AVRT).

6. INVESTIGATIONS & DIAGNOSIS¶

• Initial Evaluation: ◦ Obtain ECG at time of symptoms. ◦ Utilize wearable devices (watch/smartphone) for pre-visit diagnosis. ◦ Ambulatory ECG recording for transient arrhythmias. ◦ Exercise testing to assess exercise-related symptoms or provoke arrhythmia. • Advanced Evaluation: ◦ Assess underlying cardiac disease and exclude dangerous arrhythmias. ◦ Invasive electrophysiology study (EPS): → Used to provoke arrhythmia with pacing, confirm mechanism, and risk stratify. → Typically performed at the time of intended catheter ablation. • Vagal Maneuvers & Pharmacologic Challenge: ◦ Vagal maneuvers or carotid sinus massage (CSM) to achieve AV block. ◦ CSM Caution: Use cautiously if carotid atherosclerosis is suspected due to risk of embolism. ◦ Adenosine (6 or 12 mg): → Used to cause transient AV block. → Success in terminating AV nodal-dependent SVT. → Useful for diagnosing non-AV nodal-dependent SVT (e.g., atrial tachycardia or atrial flutter).

6.3 Vagal Maneuvers (Table 253-2)¶

Specific maneuvers to achieve AV block include: 1. Holding breath while bearing down (Larynx) → Vagus nerve stimulation. 2. Breathing hard into a syringe against pressure (Chest muscles) → Vagus nerve stimulation. 3. Raise legs abruptly (Lungs) → Vagus nerve stimulation. 4. Submerge face into cold water (Diaphragm) → Vagus nerve stimulation. 5. Carotid sinus massage (Abdominal muscles/Rectus muscles) → Vagus nerve stimulation. 6. Adenosine → Transient AV block.

7. MANAGEMENT & TREATMENT¶

Non-Pharmacologic Management: ◦ Vagal maneuvers or carotid sinus massage (CSM) to achieve AV block. ◦ CSM Caution: Use cautiously if carotid atherosclerosis is suspected due to risk of embolism.
Pharmacologic Management: ◦ Adenosine: First-line pharmacologic agent for terminating AV nodal-dependent SVT. ◦ Note: Some atrial tachycardias are adenosine sensitive; termination does not rule out AT.
Interventional Management: ◦ Invasive electrophysiology study (EPS) to provoke arrhythmia, confirm mechanism, and risk stratify. ◦ Catheter ablation for treatment of the identified arrhythmia.

8. PROGNOSIS & COMPLICATIONS¶

• Complications: ◦ Rare cardiac arrest in patients with WPW syndrome or severe heart disease (e.g., hypertrophic cardiomyopathy). • Prognostic Factors: ◦ Prognosis and treatment vary considerably depending on the mechanism and underlying heart disease. • Asymptomatic Cases: ◦ Do not require treatment or further evaluation.

9. SPECIAL CONSIDERATIONS¶

• Underlying Heart Disease: ◦ Atrial fibrillation is often associated with various heart diseases; initial evaluation must assess possible underlying cardiac conditions.

10. KEY PEARLS & CLINICAL TRAPS¶

• Diagnostic Clues: ◦ Ventricular preexcitation on resting ECG → suggests AV reciprocating tachycardia using an accessory pathway. ◦ Ongoing arrhythmia on recording usually establishes/suggests diagnosis. • Clinical Traps: ◦ Adenosine sensitivity does not exclude atrial tachycardia (AT). ◦ Carotid sinus massage (CSM) must be used cautiously in patients with potential carotid atherosclerosis.

Reference Tables¶

TABLE 253-1 Mechanisms of Supraventricular Arrhythmias Physiologic Sinus Tachycardia Defining feature : normal sinus…¶

Harrison's 22e, p.1932

Physiologic Sinus Tachycardia
Defining feature: normal sinus mechanism precipitated by exertion, stress, exogenous or endogenous stimulants, concurrent illness
Pathologic Supraventricular Tachycardia (SVT)
A. Tachycardias originating from the atrium Defining feature: tachycardia may continue despite beats that fail to conduct to the ventricles, indicating that the atrioventricular (AV) node is not participating in the tachycardia circuit 1. Inappropriate sinus tachycardia Defining feature: tachycardia from the normal sinus node area that occurs without an identifiable precipitating factor as a result of dysfunctional autonomic regulation 2. Focal atrial tachycardia (AT) Defining feature: regular atrial tachycardia with defined P wave; may be sustained, nonsustained, paroxysmal, or incessant; frequent sites of origin occur along the valve annuli of left or right atrium, pulmonary veins, coronary sinus musculature, superior vena cava 3. Atrial flutter and macroreentrant atrial tachycardia Defining feature: macroreentry reflected as organized atrial activity on an electrocardiogram (ECG), commonly seen as sawtooth flutter waves at rates typically faster than 200 beats/min 4. Atrial fibrillation Defining feature: chaotic rapid atrial electrical activity with variable ventricular rate; the most common sustained cardiac arrhythmia in older adults 5. Multifocal atrial tachycardia Defining feature: multiple discrete P waves often seen in patients with pulmonary disease during acute exacerbations of pulmonary insufficiency B. AV nodal reentry tachycardia (AVNRT) Defining feature: paroxysmal regular tachycardia with P waves visible at the end of the QRS complex or not visible at all; the most common paroxysmal sustained tachycardia in healthy young adults; more common in women C. Tachycardias associated with accessory atrioventricular pathways 1. Orthodromic AV reciprocating tachycardia (AVRT) Defining feature: paroxysmal sustained tachycardia similar to AV nodal reentry; during sinus rhythm, evidence of ventricular preexcitation may be present (Wolff-Parkinson-White syndrome) or absent (concealed accessory pathway) 2. Preexcited tachycardia Defining feature: wide QRS tachycardia with QRS morphology similar to ventricular tachycardia a. Antidromic AV reciprocating tachycardia—regular paroxysmal tachycardia b. Atrial fibrillation with preexcitation—irregular wide-complex or intermittently wide-complex tachycardia, some with dangerously rapid rates faster than 250/min c. Atrial tachycardia or flutter with preexcitation
Other Supraventricular Arrhythmias
A. Premature atrial contractions (PACs) Defining feature: sinus rhythm with an early atrial complex distinct from the sinus P wave resulting in an irregular rhythm. A pattern of ectopy (i.e., trigeminy, bigeminy) is sometimes seen with PACs B. Sinus arrhythmia Defining feature: irregular rhythm with a sinus P wave and with P-P intervals varying with respiration C. Accelerated junctional rhythm Defining feature: paroxysmal regular rhythm with P waves visible at the end of the QRS complex or not visible at all D. Ectopic atrial rhythm Defining feature: regular rhythm with a rate <100 beats/min but usually faster than sinus rhythm and with a P wave distinct from sinus that may or may not sustain
253	Approach to Supraventricular Arrhythmias William H. Sauer, Paul C. Zei