Fast heart rate on the ward
Narrow or broad, regular or irregular, any adverse features? And is it just sinus tachycardia from bleeding, sepsis, pain or dehydration?
"Bed 11's pulse is 150." She is 55, admitted with pneumonia. She feels her heart racing. BP 118/72, no chest pain, not breathless at rest. The ECG shows a regular narrow-complex tachycardia at 150 with no clear P waves.
A second patient, 3 days after a bowel resection, has a pulse of 132 in sinus rhythm, temperature 38.8 °C, BP 98/60.
Is the first one sinus, flutter or SVT, and should the second one get a beta-blocker?
- Adverse features?Shock, syncope, chest pain (ischaemia), heart failure: synchronised cardioversion by a senior.
- 12-lead ECGNarrow or broad? Regular or irregular? P waves?
- Sinus tachycardiaTreat the cause: fever, pain, sepsis, bleeding, dehydration, PE, anxiety, withdrawal.
- Regular narrow, not sinusVagal manoeuvres, then adenosine.
- Irregular narrowAtrial fibrillation: see the AF guide.
- Broad complexTreat as VT if unsure. Senior now.
- Check potassium and magnesiumCorrect them. Review drugs.
- Any adverse feature
- Broad-complex tachycardia
- Rate above 150 not responding
- Pre-excitation (WPW) on ECG
- New AF after bowel surgery (think leak)
- Sinus tachycardia from sepsis, bleeding or PE
- Atrial flutter
- VT
- Thyrotoxicosis
- Hypovolaemia
- Anastomotic leak (new AF after bowel surgery)
- Alcohol withdrawal
| Adverse features | Shock, syncope, myocardial ischaemia, heart failure: synchronised DC cardioversion |
| Adenosine | 6 mg rapid IV push with flush, then 12 mg, then 18 mg |
| Atrial flutter | Often regular at about 150 (2:1 block) |
| Sinus tachycardia | Treat the cause, don't slow it with drugs |
| Potassium target | 4.0–5.0 mmol/L |
| Magnesium target | Above 1.0 mmol/L in arrhythmias |
| Amiodarone | 300 mg IV over 20–60 minutes, then 900 mg over 24 hours |
Check every dose against a current drug reference and your hospital protocol.
On this page
On the phone
- What is the rate and BP? Any chest pain, breathlessness, dizziness, collapse?
- Ask the nurse to do a 12-lead ECG and connect a cardiac monitor.
- Why was the patient admitted? Fever, bleeding, surgery?
Assessment
- A–E and adverse featuresShock, syncope, chest pain, heart failure.
- 12-lead ECGRate, rhythm, QRS width, P waves, flutter waves.
- Look for the causeFever, sepsis, bleeding, dehydration, pain, PE, thyroid, drugs (salbutamol, withdrawal).
- BloodsPotassium, magnesium, calcium, CBC, thyroid, troponin if chest pain.
- TreatPer rhythm and cause.
Read the ECG
- Sinus tachycardia
- Treat the cause
- SVT or atrial flutter
- Vagal manoeuvres, adenosine
- AF (or multifocal atrial tachycardia)
- Rate control, anticoagulation decision
- VT until proven otherwise
- Amiodarone if stable, DC shock if not
- AF with bundle branch block, or pre-excited AF (WPW)
- Senior
- avoid AV-node blockers
Sinus tachycardia
Sinus tachycardia is a response, not a disease. Never slow it with a beta-blocker without finding the cause.
| Cause | Look for |
|---|---|
| Sepsis | Fever, low BP, source |
| Bleeding | Post-op, melaena, falling Hb |
| Dehydration | Negative balance, dry |
| Pain or anxiety | Settles with treatment |
| PE | Hypoxia, post-op, immobile |
| Anaemia | Low Hb |
| Thyrotoxicosis | Tremor, weight loss, goitre |
| Drugs and withdrawal | Salbutamol, caffeine, alcohol or benzodiazepine withdrawal |
Supraventricular tachycardia
- Modified ValsalvaBlow into a 10 mL syringe for 15 seconds while semi-recumbent, then lie flat with legs raised 45° for 15 seconds.
- Adenosine 6 mgRapid IV push into a large vein (antecubital), with a fast 20 mL saline flush. Warn about chest discomfort and a feeling of doom.
- Then 12 mg, then 18 mgIf no response.
- Still not workingSenior: verapamil, beta-blocker, or cardioversion.
Adenosine can unmask atrial flutter (sawtooth waves) by briefly slowing the ventricular rate. Avoid adenosine in severe asthma. Patients on dipyridamole need a smaller dose; heart transplant patients are very sensitive to it.
Broad-complex tachycardia
- Assume VT, especially with heart disease or previous MI.
- Unstable: synchronised cardioversion under sedation, then amiodarone.
- Stable: amiodarone 300 mg IV over 20–60 minutes, senior and cardiology.
- Polymorphic VT with long QT (torsades): magnesium sulfate 2 g IV, correct potassium, stop QT-prolonging drugs.
- Irregular broad-complex at very fast rates: pre-excited AF. Avoid AV-node blockers (adenosine, verapamil, diltiazem, digoxin, beta-blockers).
Treatment
See tachyarrhythmias and atrial fibrillation.
Common mistakes
- Giving a beta-blocker for sinus tachycardia from sepsis or bleeding.
- Giving adenosine slowly or into a hand vein.
- Calling a broad-complex tachycardia "SVT with aberrancy" without a senior.
- Giving verapamil to a patient with VT.
- Missing atrial flutter at 150.
- Treating new AF after bowel surgery without looking for a leak.
Frequently asked questions
What is the first treatment for SVT?
Vagal manoeuvres (modified Valsalva), then adenosine 6 mg, 12 mg and 18 mg rapid IV boluses if needed.
Should sinus tachycardia be treated with a beta-blocker?
No. It is a response to something else (fever, sepsis, pain, bleeding, PE, dehydration). Treat the cause.
What are adverse features in a tachycardia?
Shock, syncope, myocardial ischaemia (chest pain) and heart failure. Any of these means electrical cardioversion.
Why is a regular rate of 150 suspicious?
It is typical of atrial flutter with 2:1 block. Look for sawtooth flutter waves, or give adenosine to reveal them.
Test yourself
Exam-style questions on this guide, from our two question banks. Choose an answer to see why each option is right or wrong.
1. A stable patient has a regular narrow-complex tachycardia at 180. Vagal manoeuvres fail. What is next?
Answer: Adenosine 6 mg rapid IV. Adenosine 6 mg, then 12 mg, then 18 mg rapid boluses with a flush.
- DC cardioversion: Stable patient.
- Amiodarone first: Not first.
- Digoxin: Slow.
- Metoprolol IV first: Adenosine is first.
2. A febrile septic patient has sinus tachycardia at 130. What is the right management?
Answer: Treat the sepsis. Sinus tachycardia is a response; treat the cause.
- Adenosine: Not for sinus tachycardia.
- Digoxin: No.
- IV metoprolol: Masks compensation.
- DC cardioversion: No.
3. Adenosine briefly slows a regular tachycardia at 150, revealing sawtooth waves. What is the rhythm?
Answer: Atrial flutter. Atrial flutter often runs at 150 with 2:1 block.
- SVT: Would terminate.
- Sinus tachycardia: No sawtooth.
- AF: Irregular.
- VT: Broad complexes.
4. An ECG shows a regular narrow-complex tachycardia at 150/min with saw-tooth flutter waves in II, III and aVF. Which definitive treatment has the highest cure rate?
Answer: Isthmus catheter ablation. Typical atrial flutter: macro-reentrant circuit around the tricuspid annulus through the cavotricuspid isthmus; atrial rate ~300/min with 2:1 block → ventricular rate ~150; saw-tooth waves in inferior leads. Adenosine transiently increases block (reveals flutter waves). Acute: rate control, DC cardioversion (low energy) — anticoagulate as for AF (same stroke risk, CHA₂DS₂-VASc). Definitive: catheter ablation of the cavotricuspid isthmus (> 90% success).
- Long-term oral digoxin: Digoxin gives weak rate control only.
- Continuous adenosine infusion: Adenosine is transient and diagnostic.
- Amiodarone indefinitely: Amiodarone has side effects and is not curative.
5. A 24-year-old woman has palpitations. HR 190/min, BP 118/76 mmHg. ECG shows a regular narrow-complex tachycardia. A modified Valsalva manoeuvre fails. What is the next step?
Answer: IV adenosine 6 mg rapid bolus. Stable regular narrow-complex tachycardia is usually AV re-entrant SVT. After vagal manoeuvres, give adenosine 6 mg as a rapid IV bolus into a large vein followed by a flush; if needed, give 12 mg, then 18 mg. Warn the patient about a brief feeling of doom or chest tightness. Avoid adenosine in severe asthma — verapamil is an alternative.
- Synchronised DC cardioversion: Cardioversion is for unstable tachycardia (shock, syncope, ischaemia, heart failure); she is stable, so adenosine comes first.
- IV amiodarone 300 mg infusion: Amiodarone is used for stable broad-complex (ventricular) tachycardia, not as the next step in narrow-complex SVT.
- IV digoxin loading dose: Slow and not first-line for SVT.
6. Which current is mainly responsible for the spontaneous phase 4 depolarisation of SA node cells?
Answer: Funny current (If). Pacemaker cells have no stable resting potential. In phase 4, the funny current (If, slow Na⁺ influx through HCN channels) gradually depolarises the cell; T-type then L-type Ca²⁺ channels produce the upstroke (phase 0). Sympathetic stimulation increases If (faster rate); vagal stimulation slows it. Ivabradine blocks If.
- Fast Na⁺ current: Absent in nodal upstroke.
- L-type Ca²⁺ current only: Produces the nodal upstroke.
- K⁺ efflux: Repolarises.
- Chloride influx: Not involved.
7. Which enzyme is the rate-limiting step in catecholamine synthesis?
Answer: Tyrosine hydroxylase. Catecholamine pathway: tyrosine → (tyrosine hydroxylase, needs BH4; rate-limiting) → L-DOPA → (DOPA decarboxylase, B6) → dopamine → (dopamine β-hydroxylase, vitamin C, copper) → noradrenaline → (PNMT, induced by cortisol, SAM) → adrenaline. Breakdown by MAO and COMT gives VMA and HVA.
- DOPA decarboxylase: Next step; uses B6.
- Dopamine β-hydroxylase: Needs vitamin C and copper.
- Phenylethanolamine N-methyltransferase: Final step in the adrenal medulla; cortisol induces it.
- Monoamine oxidase: Breakdown enzyme.
References and dose sources
- Adenosine dosing: Drugs.com: Adenosine dosage (see also our adenosine dose page)
- Amiodarone dosing: Drugs.com: Amiodarone dosage (see also our amiodarone dose page)
- Magnesium sulfate dosing: Drugs.com: Magnesium sulfate dosage (see also our magnesium sulfate dose page)
- Bisoprolol dosing: Drugs.com: Bisoprolol dosage (see also our bisoprolol dose page)
International guidance is linked where it reflects good practice. Where your hospital’s protocol differs, follow your hospital.