Treatment of Tachycardia in a 32-Year-Old Female
The treatment of tachycardia in a 32-year-old female depends entirely on whether the patient is hemodynamically stable or unstable, and you must first identify and treat the underlying cause rather than reflexively treating the heart rate itself.
Immediate Assessment and Stabilization
Assess hemodynamic stability first by checking for signs of shock, altered mental status, ischemic chest pain, acute heart failure, or hypotension directly attributable to the tachycardia 1. If any of these adverse signs are present with a heart rate >150 bpm, proceed immediately to synchronized cardioversion 2, 1.
- Attach cardiac monitor, establish IV access, obtain vital signs, and get a 12-lead ECG to define the rhythm—but do not delay cardioversion if the patient is unstable 1
- Provide supplemental oxygen if there are signs of increased work of breathing or inadequate oxygenation, as hypoxemia is a common reversible cause of tachycardia 1
Critical First Step: Identify the Underlying Cause
Do not treat the heart rate directly if this is sinus tachycardia—you must identify and treat the underlying cause instead 1, 3. This is the most common pitfall in managing tachycardia in young adults.
Common physiologic causes in a 32-year-old female include:
- Fever, infection, dehydration, anemia, pain 1, 3
- Hyperthyroidism (obtain TSH testing) 4, 3
- Anxiety or panic disorder (frequently misdiagnosed as SVT, and vice versa) 3, 5
The upper limit of normal sinus tachycardia is approximately 220 minus the patient's age (approximately 188 bpm for a 32-year-old) 1. Rates below 150 bpm in the absence of ventricular dysfunction are more likely secondary to underlying conditions rather than the cause of instability 4.
Management Based on Rhythm Type
For Narrow-Complex Regular SVT (Hemodynamically Stable)
Vagal maneuvers should be attempted first if the patient is clinically stable 2. The Valsalva maneuver (forceful exhalation against a closed glottis) is most common, or unilateral carotid artery pressure can be applied if no carotid bruit is present 2.
Adenosine is the drug of choice for terminating AV nodal re-entrant tachyarrhythmias 2, 1:
- Initial dose: 6 mg rapid IV push followed by saline flush 1
- Second dose: 12 mg if no effect after 1-2 minutes 2, 1
- Adenosine terminates approximately 95% of AVNRT cases 1
- Must be given in a monitored environment as it can cause transient complete heart block 2
Common side effects of adenosine include flushing and chest pain (usually lasting <60 seconds), and it should not be used in asthmatic patients due to risk of bronchospasm 2.
If adenosine fails, IV beta-blockers (metoprolol 2.5-5 mg every 2-5 minutes) or IV diltiazem (20 mg over 2 minutes) are reasonable alternatives 2, 1.
For Atrial Fibrillation/Flutter with Rapid Ventricular Response
Beta-blockers or non-dihydropyridine calcium channel blockers (diltiazem, verapamil) are first-line for rate control 1:
- Target resting heart rate <100 bpm 1
- Verapamil: 5-10 mg IV over 60 seconds 2
- Diltiazem: 20 mg (0.25 mg/kg) over 2 minutes 1
If hemodynamically unstable, proceed to synchronized cardioversion with 200 J for atrial fibrillation or 50 J for flutter 1.
For Wide-Complex Tachycardia (Presumed Ventricular Tachycardia)
Treat all wide-complex tachycardia as ventricular tachycardia unless proven otherwise 1.
For stable monomorphic VT, amiodarone is first-line 2, 1:
- 150 mg IV over 10 minutes 1
- Followed by maintenance infusion of 1 mg/min for first 6 hours, then 0.5 mg/min 1
- Antiarrhythmic effect may take up to 30 minutes 2
Lidocaine is an alternative for VT 2:
- 1-3 mg/kg IV bolus (or 100 mg bolus for cardiac arrest) 2
- May be repeated after 5-10 minutes 2
- Followed by infusion of 2-4 mg/min if successful 2
For unstable VT, proceed immediately to synchronized cardioversion (100 J, then 200 J, then 360 J) 2, 1.
Critical Pitfalls to Avoid
Never use AV nodal blocking agents (beta-blockers, calcium channel blockers, digoxin, adenosine) in patients with Wolff-Parkinson-White syndrome and wide-complex tachycardia, as they can accelerate ventricular rate and precipitate ventricular fibrillation 1. Look for delta waves on the ECG suggesting pre-excitation, which requires immediate cardiology referral 4, 3.
Do not aggressively treat compensatory tachycardia in patients with poor cardiac function or shock, as stroke volume is limited and cardiac output depends on the elevated heart rate 1. "Normalizing" the rate can be detrimental in these patients 1.
Verapamil is contraindicated if beta-blockers have been taken due to risk of profound bradycardia and hypotension 2.
When to Refer to Cardiology
Immediate cardiology referral is required for 4, 3:
- Pre-excitation (WPW syndrome) on ECG
- Wide-complex tachycardia of unknown origin
- Syncope during tachycardia or with exercise
- Documented sustained supraventricular tachycardia