What is the recommended approach for assessing and managing a patient with known intermittent supraventricular tachycardia (SVT) during a clinic visit?

Assessment of a Patient with Known Intermittent SVT for a Clinic Visit

The clinic assessment should focus on obtaining a detailed clinical history of episode characteristics, performing a 12-lead ECG to identify pre-excitation or other diagnostic features, and arranging rhythm documentation if not already obtained, with prompt referral to an arrhythmia specialist for patients with severe symptoms, pre-excitation, or those desiring definitive therapy. 1

Clinical History - Key Elements to Document

The most crucial aspect of your assessment is obtaining a detailed pattern description 1:

• Number and frequency of episodes (daily, weekly, monthly) 1
• Duration of each episode (seconds, minutes, hours) 1
• Mode of onset (abrupt vs gradual) - abrupt onset suggests paroxysmal SVT rather than sinus tachycardia 1
• Specific triggers (exercise, caffeine, alcohol, stress, positional changes) 1
• Associated symptoms during episodes:
  • Palpitations (present in 86% of patients) 2
  • Chest discomfort or pressure (47% of patients) 2
  • Dyspnea (38% of patients) 2
  • "Neck pounding" or "shirt flapping" sensation (suggests AVNRT with cannon A waves) 1
  • Syncope or near-syncope (14% experience syncope, 50% near-syncope) 1
  • Fatigue (77% of patients) 1

Critical red flags requiring urgent specialist referral: 1

• Syncope or severe dyspnea during palpitations
• Pre-excitation on baseline ECG (risk of sudden death with atrial fibrillation)
• Wide complex tachycardia of unknown origin

Physical Examination During Sinus Rhythm

While physical examination during tachycardia is standard, it rarely leads to definitive diagnosis 1. During your clinic visit in sinus rhythm:

• Assess for structural heart disease that may not be apparent (murmurs, signs of heart failure) 1
• Document baseline vital signs including resting heart rate and blood pressure 1
• Screen for precipitating conditions: thyroid examination, signs of anemia, evidence of substance use 1

Essential Diagnostic Testing

12-Lead ECG (Mandatory)

A resting 12-lead ECG must be obtained at every visit 1:

• Look specifically for pre-excitation (delta waves) - if present with history of paroxysmal palpitations, this is sufficient for presumptive diagnosis of AVRT and requires immediate referral to electrophysiology without need for documented episodes 1
• Pre-excitation with irregular palpitations suggests atrial fibrillation - requires immediate electrophysiological evaluation due to risk of sudden death 1
• Baseline conduction abnormalities (bundle branch blocks)
• Evidence of prior myocardial infarction
• QT interval assessment

Do not rely on automated ECG interpretation - these systems are unreliable and commonly suggest incorrect arrhythmia diagnoses 1

Rhythm Documentation Strategy

If SVT has never been documented on 12-lead ECG, obtaining this is essential 1:

• Patients should always be encouraged to obtain at least one 12-lead ECG during arrhythmia 1
• For frequent episodes (several per week): 24-hour Holter monitor 1
• For less frequent episodes: Event recorder or wearable loop recorder (more useful than Holter) 1
• For rare symptoms (<2 episodes per month) with severe hemodynamic instability: Consider implantable loop recorder 1
• For exercise-triggered arrhythmias: Exercise stress testing 1

Echocardiography

Echocardiography should be considered in all patients with documented sustained SVT to exclude structural heart disease that cannot be detected by physical examination or ECG 1. This is particularly important because:

• Sustained SVT with fast ventricular response can lead to tachycardia-mediated cardiomyopathy (occurs in approximately 1% of patients) 1, 2
• Structural heart disease influences treatment decisions

Laboratory Evaluation

Screen for reversible causes 1:

• Thyroid function tests (hyperthyroidism)
• Complete blood count (anemia)
• Electrolytes (hypokalemia, hypomagnesemia)
• Toxicology screen if indicated (cocaine, amphetamines)

Immediate Referral Indications

Refer promptly to cardiac arrhythmia specialist for: 1

1. Any patient with Wolff-Parkinson-White syndrome (pre-excitation + arrhythmias) - potential for lethal arrhythmias 1
2. Wide complex tachycardia of unknown origin 1
3. Severe symptoms: syncope or dyspnea during palpitations 1
4. Drug resistance or intolerance in narrow complex tachycardias 1
5. Patient preference to be free of drug therapy 1

Management Discussion During Clinic Visit

Patient Education (Class I Recommendation)

All patients should be taught vagal maneuvers 1:

• Modified Valsalva maneuver (43% effective acutely) 2
• Carotid sinus massage (if no carotid bruits)
• These should be demonstrated and practiced in the office

Ongoing Pharmacotherapy Options

For symptomatic patients without pre-excitation (Class I recommendation): 1

• First-line: Oral beta blockers, diltiazem, or verapamil 1
• Ensure baseline heart rate >50 bpm before initiating beta blockers 1

For patients without structural/ischemic heart disease (Class IIa recommendation): 1

• Flecainide or propafenone are reasonable alternatives for those not candidates for or preferring not to undergo catheter ablation 1
• Starting dose for flecainide: 50 mg every 12 hours for PSVT, can increase by 50 mg bid every 4 days (maximum 300 mg/day for PSVT) 3

Important caveat: Class I or III antiarrhythmic drugs should NOT be initiated without documented arrhythmia due to proarrhythmia risk 1

Definitive Treatment Discussion

Catheter ablation is Class I recommendation as useful for diagnosis and potential treatment of SVT 1. Key points to discuss:

• Success rates: 94.3% to 98.5% for single procedure 2
• Recommended as first-line therapy for recurrent, symptomatic paroxysmal SVT 4, 2
• Curative in majority of patients 5
• Should be considered for all patients with recurrent symptoms 4, 5

Eliminate Precipitating Factors

Review and counsel on elimination of: 1

• Excessive caffeine intake
• Alcohol consumption
• Nicotine use
• Recreational drugs

Follow-Up Plan

• If no ECG documentation exists: Arrange appropriate monitoring strategy based on episode frequency 1
• If pre-excitation identified: Urgent electrophysiology referral 1
• If symptomatic despite medical therapy: Refer for ablation consideration 1
• If asymptomatic on current therapy: Continue current management with periodic reassessment

The threshold for cardiology/electrophysiology referral should be low - all patients treated for SVT should be referred for heart rhythm specialist opinion 5, and invasive electrophysiological study with catheter ablation may be used for both diagnosis and therapy in cases with clear history of paroxysmal regular palpitations 1.