Fast AF / AF with RVR

Fast atrial fibrillation is one of the most common medical on-call bleeps in NHS hospitals.
You will see it everywhere — ED admissions, septic patients, post-operative wards, and frail elderly patients overnight.

Your priority is not immediately restoring sinus rhythm.

Your priority is:

👉 assess stability
👉 control rate safely
👉 identify the trigger
👉 escalate when needed

What is AF with RVR?

Atrial fibrillation with rapid ventricular response (RVR) means:

  • Irregularly irregular rhythm
  • No clear P waves
  • Ventricular rate usually >100–110 bpm

Many ward calls happen when HR is 130–160 bpm.

Why does AF suddenly become fast?

AF is often a marker of another problem.

Always ask: “Why now?”

Common NHS triggers:

  • Sepsis
  • Hypoxia
  • Pain
  • Dehydration
  • Electrolyte imbalance (↓K+, ↓Mg2+)
  • Acute heart failure
  • PE
  • MI
  • Alcohol withdrawal
  • Post-surgery stress

Treating the trigger often fixes the AF.

First step = A–E assessment

Before prescribing anything:

Check:

  • BP
  • Conscious level
  • Oxygen saturation
  • Chest signs
  • Perfusion
  • Urine output

🚨 Unstable = emergency

Signs of instability:

  • SBP <90
  • Chest pain / ACS
  • Pulmonary oedema
  • Shock
  • Reduced consciousness

👉 Call senior + urgent cardioversion pathway

Do NOT delay.

Stable fast AF — ward management

This is the most common scenario.

Goal:

Rate control, not rhythm control.

Target HR:
👉 <110 bpm (initially acceptable)

Immediate investigations

  • ECG (confirm AF)
  • Bloods:
    • FBC
    • U&E
    • CRP
    • Magnesium
    • Troponin (if indicated)
    • TFTs (not urgent overnight)
  • CXR if respiratory issue suspected

Rate control — practical NHS approach

Choice depends on patient physiology.

1️⃣ Beta-blocker (often first line)

Bisoprolol (oral)
or
Metoprolol (IV in monitored setting)

Good if:

  • haemodynamically stable
  • no severe asthma
  • not in acute heart failure

Avoid if hypotensive.

2️⃣ Calcium channel blocker

Diltiazem / Verapamil

Useful alternative if beta-blockers unsuitable.

Avoid in:

  • heart failure with reduced EF
  • hypotension

3️⃣ Digoxin

Best for:

  • frail patients
  • hypotension
  • heart failure
  • sedentary patients

Slower onset — not ideal alone in very fast AF.

Often combined later.

Important principle

Do NOT give multiple rate-control drugs quickly without senior input.

Stacking drugs → hypotension + collapse.

Rhythm control — when?

Usually NOT done acutely on ward.

Consider only if:

  • haemodynamic instability
  • new AF <48 hours + specialist decision
  • cardiology-led plan

Most ward AF = rate control first.

Anticoagulation (always think early)

Ask yourself:

👉 Does this patient need anticoagulation?

Use CHA₂DS₂-VASc (not overnight emergency but must be considered).

Common practice:

  • start DOAC after senior review
  • ensure bleeding risk assessed

Document clearly.

Correct reversible causes

Often the real treatment:

  • Give fluids if dehydrated
  • Treat sepsis
  • Correct potassium (>4.0 ideal)
  • Replace magnesium
  • Treat hypoxia
  • Control pain

AF improves once physiology improves.

When to escalate

Escalate if:

  • HR persistently >150
  • Hypotension develops
  • Chest pain
  • Heart failure signs
  • Uncertain diagnosis
  • New AF in young patient
  • Failed initial rate control

Common on-call mistakes

  • Treating numbers instead of patient
  • Giving beta-blocker to shocked patient
  • Ignoring underlying sepsis
  • Over-aggressive IV drugs
  • Forgetting anticoagulation plan
  • Not correcting electrolytes

AF is often a symptom, not the disease.

Practical ward mindset

When bleeped:

“Patient in fast AF HR 150”

Think:

  1. Are they stable?
  2. Why did AF happen?
  3. Slow rate safely
  4. Fix trigger
  5. Document & escalate appropriately

Take-home concept

Fast AF is rarely a cardiology emergency —
it is usually a physiology problem presenting as a rhythm problem.

Control the rate.
Treat the cause.
Escalate early if unstable.