Immediate Assessment and Stabilization
This patient requires immediate evaluation to determine if the tachycardia is causing hemodynamic instability or is a compensatory response to an underlying condition—the distinction is critical because treating the wrong target can be life-threatening. 1
Initial Evaluation Steps
Check oxygen saturation immediately and provide supplemental oxygen if hypoxemic, as hypoxemia is a common reversible cause of both tachycardia and shortness of breath 1
Attach cardiac monitor, obtain vital signs including blood pressure, and establish IV access 1
Obtain a 12-lead ECG to define the rhythm, but this should not delay immediate cardioversion if the patient is unstable 1, 2
Assess for signs of hemodynamic instability: acute altered mental status, ischemic chest discomfort, acute heart failure, hypotension, or other signs of shock 1
Critical Decision Point: Is This Sinus Tachycardia or Primary Arrhythmia?
The most common tachycardia in young adults is sinus tachycardia from physiologic causes—fever, infection, dehydration, anemia, pain, anxiety, or hyperthyroidism—and treating the underlying cause is paramount, not the heart rate itself. 1, 2, 3
If heart rate <150 bpm without ventricular dysfunction, the tachycardia is likely secondary to an underlying condition rather than the primary cause of symptoms 1
Common causes to evaluate: fever, infection, dehydration, anemia, pain, anxiety/panic disorder, hyperthyroidism 1, 2, 3
Hyperthyroidism must be excluded with TSH testing, as it commonly presents with persistent tachycardia and heat intolerance 2
If Patient is Unstable (Rate-Related Cardiovascular Compromise)
If the patient demonstrates signs of shock, acute heart failure, chest pain, or altered mental status directly caused by the tachyarrhythmia, proceed to immediate synchronized cardioversion. 1
Establish IV access and administer sedation if the patient is conscious before cardioversion 1
Do not delay cardioversion if the patient is extremely unstable 1
For narrow-complex SVT in unstable but not hypotensive patients, adenosine may be considered while preparing for cardioversion 1
If Patient is Stable: Identify and Treat Underlying Cause
For physiologic sinus tachycardia, no specific antiarrhythmic therapy is indicated—therapy is directed toward identification and treatment of the underlying cause. 1, 2
Specific Causes to Address:
Fever/infection: Treat with appropriate antibiotics and antipyretics 2, 3
Anxiety/panic disorder: This is a critical diagnostic pitfall—anxiety frequently mimics SVT, but conversely, true SVT is often misdiagnosed as panic disorder 2, 5
Hyperthyroidism: Check TSH; if elevated, initiate beta-blocker therapy and endocrine referral 2
Critical Pitfall: Do NOT Treat Compensatory Tachycardia
Avoid rate-controlling medications (beta-blockers, calcium channel blockers, adenosine) if the tachycardia is compensatory for hypotension, hypovolemia, or other underlying conditions—slowing the heart rate without correcting the underlying problem can precipitate cardiovascular collapse. 4, 2
When cardiac function is poor, cardiac output can be dependent on a rapid heart rate—"normalizing" the heart rate can be detrimental 1
The sinus tachycardia is maintaining cardiac output in the setting of limited stroke volume 4
When to Refer to Cardiology Urgently
Immediate cardiology referral is required for: 2
- Pre-excitation (WPW syndrome) on ECG
- Wide-complex tachycardia of unknown origin
- Syncope during tachycardia or with exercise
- Documented sustained SVT
Specific Management for Primary Arrhythmias (If Identified)
Narrow-Complex SVT (Stable):
Attempt vagal maneuvers first (Valsalva maneuver, carotid massage) 1
Adenosine is the first-choice drug if vagal maneuvers fail 1, 2
If adverse signs develop, attempt electrical cardioversion supplemented with amiodarone if necessary 1