Tachyarrhythmias in Hospitalized Adults: Stabilize, Classify, and Treat

Bottom line

Initial workup

• Confirm the rhythm on a 12-lead EKG: narrow and irregularly irregular without discrete P waves = atrial fibrillation; narrow and regular = SVT or atrial flutter (flutter often runs ~150 with 2:1 block — look for sawtooth waves in II, III, aVF, or use vagal maneuvers/adenosine to unmask); wide and regular = VT until proven otherwise; wide and irregular = AF with aberrancy or pre-excited AF.
• Hunt the precipitant: CBC, BMP with magnesium and calcium, troponin, TSH, and a targeted evaluation for sepsis, hypovolemia, pain, anemia, hypoxemia, pulmonary embolism, alcohol withdrawal, the postoperative state, and new medications (steroids, beta-agonists, vasopressors). Continuous telemetry and a chest radiograph.
• Risk stratify: calculate CHA2DS2-VASc, assess bleeding risk and any upcoming procedures, and establish AF duration (< 48 h vs ≥ 48 h or unknown) because it drives the cardioversion and anticoagulation strategy. Obtain a transthoracic echocardiogram for LV function, valve disease, and atrial size — LVEF determines which rate-control drug is safe.

Acute management

• Unstable at any point (hypotension or shock, ischemic chest pain, acute pulmonary edema, altered mentation): immediate synchronized cardioversion with sedation — AF 120–200 J biphasic, atrial flutter or SVT 50–100 J, monomorphic VT with a pulse 100 J. Pulseless or polymorphic VT is defibrillated per ACLS.
• Stable AF with RVR: start IV rate control. Preferred is IV diltiazem 0.25 mg/kg over 2 minutes (≈ 15–20 mg), repeat 0.35 mg/kg after 15 minutes if needed, then an infusion of 5–15 mg/h; or IV metoprolol tartrate 2.5–5 mg over 2 minutes every 5 minutes up to 3 doses, favored with ischemia or a high adrenergic state. Avoid non-dihydropyridine calcium channel blockers when the EF is reduced or decompensated heart failure is suspected — use cautious IV metoprolol, amiodarone, or digoxin instead.
• Soft blood pressure without shock, or EF unknown or low: IV digoxin (0.25 mg IV every 6 hours to a total load of ~0.75–1.5 mg over 24 hours, reduced in renal impairment) or IV amiodarone are reasonable rate-control choices. Amiodarone may convert the rhythm, so apply the same pre-cardioversion anticoagulation logic before giving it.
• Treat the precipitant aggressively and concurrently — repleting potassium to > 4.0 and magnesium to > 2.0, and treating sepsis, pain, hypoxemia, and volume depletion often does more for the rate than escalating AV nodal blockade.
• Other rhythms: narrow-regular SVT → vagal maneuvers, then adenosine 6 mg rapid IV push, then 12 mg; stable monomorphic VT → IV amiodarone 150 mg over 10 minutes (or procainamide), with cardioversion if it fails; irregular wide-complex pre-excited AF → no AV nodal blockers at all (no diltiazem, beta-blocker, digoxin, or adenosine) — use procainamide or cardioversion.

Inpatient and longitudinal management

• Decide rate vs rhythm control: rate control is the appropriate initial strategy for most hospitalized patients with a reversible precipitant; early rhythm control is favored in younger, highly symptomatic, first-detected AF, or when rate control fails or heart failure worsens. In new-onset AF after cardiac surgery, rhythm control has not shown outcome superiority over rate control, and aggressive rhythm strategies carry more hypotension, bradycardia, and syncope.
• Cardioversion timing and anticoagulation: if AF duration is clearly < 48 hours with low thromboembolic risk, cardioversion may proceed with anticoagulation started at the time of the procedure; if ≥ 48 hours or unknown, either 3 weeks of therapeutic anticoagulation or a TEE to exclude left atrial thrombus first, followed by at least 4 weeks of anticoagulation after cardioversion regardless of CHA2DS2-VASc.
• Long-term anticoagulation is driven by stroke risk, not by rhythm strategy or symptom resolution: a DOAC is preferred over warfarin unless there is a mechanical valve or moderate-to-severe mitral stenosis. Treat at CHA2DS2-VASc ≥ 2 in men and ≥ 3 in women.
• Transition IV to oral rate control (oral diltiazem, metoprolol tartrate or succinate) 12–24 hours before discharge and confirm control with ambulation. Address risk-factor modification — hypertension, sleep apnea, alcohol, obesity, thyroid disease — as part of the AF care plan.

Monitoring and disposition

• Continuous telemetry with blood pressure checks every 15 minutes during IV boluses and titration, then hourly until the rate is stable; repeat a 12-lead EKG after conversion or any rhythm change.
• Check potassium and magnesium at least daily while actively rate controlling; follow renal function on digoxin or a DOAC, and obtain baseline LFTs and TSH when starting amiodarone.
• A telemetry floor is appropriate for a stable patient; ICU or step-down for hypotension requiring vasopressors, repeated cardioversion, or ongoing ischemia.
• Discharge when the rate is controlled at rest and with ambulation (resting HR generally < 110 if asymptomatic, lower if symptomatic), the precipitant is treated, the oral regimen has been tolerated ≥ 24 hours, and the anticoagulation decision is made and started with education on adherence and bleeding.
• Follow-up with cardiology or electrophysiology in 2–4 weeks and primary care within 1 week to review rate, symptoms, and anticoagulation; teach pulse self-monitoring and return precautions for syncope, chest pain, dyspnea, or bleeding.

Escalate care if

• Blood pressure drops, ischemic chest pain develops, pulmonary edema appears, or mentation declines — immediate synchronized cardioversion; do not keep titrating AV nodal agents.
• The complex becomes wide and regular — treat as VT (amiodarone, cardioversion), not as SVT with aberrancy.
• Wide and irregular with varying morphology (pre-excited AF) — stop all AV nodal blockers, give procainamide or cardiovert, and obtain an urgent electrophysiology consult.
• Rate remains > 110–120 despite adequate diltiazem or metoprolol titration — look for an untreated precipitant, replete magnesium and potassium, add a second agent (digoxin) or switch to amiodarone, and consult cardiology.
• Marked bradycardia or pauses after rate-control drugs, or sinus node dysfunction unmasked on conversion — hold AV nodal agents, continue telemetry, and obtain cardiology or EP evaluation for pacing.
• AF persists with heart failure decompensation refractory to rate control — pursue rhythm control (amiodarone or cardioversion after appropriate anticoagulation or TEE).

Duration

IV rate control typically runs 12–48 hours until the precipitant is treated, then convert to oral therapy. Anticoagulation continues at least 4 weeks after any cardioversion and long term when CHA2DS2-VASc warrants.

Caveats

• Non-dihydropyridine calcium channel blockers (diltiazem, verapamil) are contraindicated in decompensated HFrEF and in pre-excited AF; do not give IV diltiazem and an IV beta-blocker close together because of bradycardia and hypotension risk.
• All AV nodal blocking agents (diltiazem, verapamil, beta-blockers, digoxin, adenosine) are contraindicated in pre-excited (WPW) AF — risk of ventricular fibrillation.
• Avoid adenosine in irregular wide-complex rhythms and use it cautiously in severe reactive airway disease.
• Digoxin needs renal dose adjustment and caution with hypokalemia and interacting drugs (amiodarone, verapamil).
• Anticoagulation decisions must account for active bleeding, recent surgery or planned procedures, severe thrombocytopenia, and renal function for DOAC selection.
• This overview assumes no accessory pathway, no acute coronary syndrome, and no known severe LV dysfunction — reassess drug choice once echocardiogram results are available.

References

1. 2023 ACC/AHA/ACCP/HRS Guideline for the Diagnosis and Management of Atrial Fibrillation. Circulation. (2023) · Primary guideline
2. Rhythm vs. rate control for treatment of postoperative atrial fibrillation after cardiac surgery: a systematic review and meta-analysis of randomized controlled trials. (2026) · Systematic review“Among postcardiac surgery patients with new-onset atrial fibrillation, there was no evidence that a rhythm control treatment strategy resulted in better outcomes than a rate control strategy.”