Irregular pulse

An irregular pulse is a pulse whose beat to beat interval varies, found on palpation, auscultation, pulse oximetry, a wearable device or an ECG. It may be occasional (isolated early beats) or continuous (atrial fibrillation).

Clinical relevance. Atrial fibrillation is the commonest sustained arrhythmia (about 1% to 2% of adults, over 10% over age 80) and raises stroke risk about five times. Many cases are asymptomatic and first found by pulse palpation or opportunistic screening. Most isolated early beats are benign, but frequent ectopy, ectopy with symptoms or heart disease needs evaluation.

Classification by rhythm.

• Occasional irregularity: premature atrial contractions, premature ventricular contractions, sinus arrhythmia (physiological variation with breathing, common in the young), ectopic couplets.
• Regularly irregular: bigeminy and trigeminy, second degree atrioventricular block (Mobitz I and fixed ratio Mobitz II), atrial flutter with variable conduction, sinoatrial exit block.
• Irregularly irregular: atrial fibrillation, multifocal atrial tachycardia, atrial flutter with variable block, frequent multifocal ectopy, atrial tachycardia with variable block.

Classification of atrial fibrillation by duration. First diagnosed, paroxysmal (self terminates within 7 days, usually under 48 hours), persistent (over 7 days), long standing persistent (over 12 months), permanent (accepted, no further rhythm control).

History.

• Symptoms: palpitations, skipped beats, dizziness, breathlessness, chest pain, fatigue, reduced exercise tolerance, syncope; or none.
• Onset and duration, triggers (alcohol, caffeine, exertion, sleep, stress, illness).
• Cardiac history: hypertension, coronary disease, valve disease (especially rheumatic mitral stenosis), cardiomyopathy, heart failure, congenital heart disease, cardiac surgery, pacemaker.
• Other disease: thyroid disease, diabetes, chronic obstructive pulmonary disease, sleep apnoea, chronic kidney disease, infection, anaemia, cancer.
• Alcohol quantity, binge drinking; drug history: caffeine, stimulants, cocaine, beta agonists, theophylline, digoxin, thyroid hormone, antiarrhythmics, QT prolonging drugs, diuretics.
• Stroke or transient ischaemic attack, bleeding history, family history of atrial fibrillation or sudden death.
• Athletic training (sinus arrhythmia and ectopy common).

Examination.

• Pulse for a full minute at the radial artery; compare apical and radial rates (pulse deficit in atrial fibrillation); blood pressure; oxygen saturation; temperature; weight.
• Rhythm by auscultation: irregularly irregular with variable first heart sound suggests atrial fibrillation; irregularity with a pattern suggests ectopy or block.
• Jugular venous pressure: absent A waves in atrial fibrillation; cannon A waves in atrioventricular dissociation.
• Murmurs (mitral stenosis, mitral regurgitation, aortic valve disease), signs of heart failure, thyroid, tremor, eye signs.
• Features of lung disease, anaemia, alcohol excess.

Red flags.

• Haemodynamic compromise: hypotension, syncope, chest pain, acute heart failure.
• Heart rate over 150 or under 40.
• Irregular broad complex tachycardia (pre-excited atrial fibrillation or polymorphic ventricular tachycardia).
• Acute neurological deficit (embolic stroke).
• Mitral stenosis or mechanical valve with atrial fibrillation.
• Syncope with ectopy or non sustained ventricular tachycardia.
• New atrial fibrillation with sepsis, pulmonary embolism, thyrotoxicosis, myocardial infarction or cardiac surgery.

Supraventricular. Atrial fibrillation, atrial flutter with variable block, atrial tachycardia with variable block, multifocal atrial tachycardia, premature atrial contractions, wandering atrial pacemaker, sinus arrhythmia.

Ventricular. Premature ventricular contractions (isolated, couplets, bigeminy, trigeminy), non sustained ventricular tachycardia, idioventricular rhythm.

Conduction disorders. Mobitz I and II second degree block, sinoatrial exit block, sinus pauses (sick sinus syndrome).

Causes and precipitants of atrial fibrillation.

• Cardiac: hypertension, heart failure, valve disease, coronary disease, cardiomyopathy, pericarditis, myocarditis, congenital heart disease, post cardiac surgery.
• Non cardiac: thyrotoxicosis, alcohol (acute or chronic), sleep apnoea, obesity, diabetes, chronic obstructive pulmonary disease, pulmonary embolism, infection and sepsis, electrolyte disturbance (potassium, magnesium), anaemia, phaeochromocytoma, pregnancy, drugs (stimulants, theophylline, beta agonists), excessive exercise, and genetic predisposition.

Mimics. Artefact from tremor or movement, a loose ECG lead, pulsus alternans, pulsus paradoxus (varies with respiration), pulse oximeter error.

1. Palpate and record the pulse in all adults over 65 and with symptoms; follow any irregular pulse with a 12 lead ECG (or single lead device trace confirmed by a clinician). Confirm absent P waves and irregular RR intervals for 30 seconds or more for atrial fibrillation.
2. Blood tests: full blood count, urea, creatinine and estimated glomerular filtration rate, electrolytes including potassium and magnesium, calcium, glucose or HbA1c, liver function tests, thyroid stimulating hormone and free thyroxine, troponin if chest pain, natriuretic peptide if heart failure suspected, and iron studies.
3. Transthoracic echocardiography for all new atrial fibrillation: atrial size, ventricular function, valve disease (mitral stenosis), left ventricular hypertrophy, pericardial disease, pulmonary pressure.
4. Ambulatory monitoring: 24 to 48 hour Holter for frequent symptoms; event recorder or patch for 7 to 30 days; implantable loop recorder after cryptogenic stroke (detects atrial fibrillation in about 10% to 30%). Quantify ectopic burden (over 10% to 15% of beats raises concern for cardiomyopathy).
5. Exercise testing to assess rate control, ischaemia and exercise induced ectopy.
6. Transoesophageal echocardiography to exclude left atrial appendage thrombus before cardioversion if anticoagulation has been incomplete or duration is over 48 hours or unknown.
7. Sleep study for suspected sleep apnoea; chest radiograph; cardiac MRI for frequent ventricular ectopy or suspected cardiomyopathy.
8. Calculate stroke risk with CHA2DS2-VASc (heart failure 1, hypertension 1, age 75 or older 2, diabetes 1, stroke or thromboembolism 2, vascular disease 1, age 65 to 74 1, female sex 1) and bleeding risk with HAS-BLED (hypertension 1, abnormal renal or liver function 1 each, stroke 1, bleeding 1, labile INR 1, age over 65 1, drugs or alcohol 1 each).
9. Genetic testing and family screening when early onset or familial atrial fibrillation, or channelopathy suspected.

Limits. Pulse palpation has sensitivity about 90% and specificity about 80% for atrial fibrillation; consumer devices vary; paroxysmal episodes are missed by short recordings; premature beats can mimic atrial fibrillation on a pulse oximeter. A normal echocardiogram does not exclude future atrial fibrillation.

Unstable irregular tachycardia (hypotension, chest pain, heart failure, altered consciousness). Synchronised direct current cardioversion 120 to 200 J biphasic under sedation; start heparin; treat cause.

Occasional ectopy and sinus arrhythmia in a patient with a normal heart. Reassure; reduce caffeine, alcohol, nicotine and stimulants; correct electrolytes; treat anxiety and sleep problems. For distressing symptoms: bisoprolol 1.25 to 5 mg daily or metoprolol 25 to 50 mg twice daily, or verapamil 40 mg three times daily. Ectopic burden over 10% to 15% with falling ejection fraction: antiarrhythmic drugs (flecainide 50 to 100 mg twice daily in a structurally normal heart) or catheter ablation.

Atrial fibrillation.

• Rate control (resting target under 110 beats/minute, under 80 if symptoms or heart failure): bisoprolol 2.5 to 10 mg daily; metoprolol succinate 50 to 200 mg daily; diltiazem 60 to 120 mg three times daily or modified release 120 to 360 mg daily (avoid in heart failure with reduced ejection fraction); verapamil 40 to 120 mg three times daily; digoxin 0.125 to 0.25 mg daily (loading 0.5 mg then 0.25 mg every 6 hours for two doses; adjust for renal function, level 0.5 to 0.9 ng/mL) for sedentary patients or with heart failure; amiodarone 300 mg intravenously over 1 hour in acute heart failure.
• Rhythm control (symptomatic, younger, first episode, heart failure related to rapid rate): electrical cardioversion; flecainide (300 mg once orally, or 2 mg/kg intravenously over 10 to 30 minutes) in structurally normal hearts; amiodarone 300 mg intravenously over 1 hour then 900 mg over 24 hours, then 200 mg three times daily for 1 week, twice daily for 1 week, then 200 mg daily, with thyroid, liver, pulmonary and ophthalmic monitoring; dronedarone 400 mg twice daily (not in heart failure); sotalol 80 mg twice daily increasing to 160 mg twice daily (monitor QTc); catheter ablation (pulmonary vein isolation) for symptomatic recurrence and for heart failure.
• Cardioversion safety: for duration under 48 hours, anticoagulate immediately; for 48 hours or more or unknown duration, anticoagulate for 3 weeks first or perform transoesophageal echocardiography; continue anticoagulation for at least 4 weeks after cardioversion and indefinitely if stroke risk warrants.
• Stroke prevention: anticoagulate men with CHA2DS2-VASc 2 or more and women 3 or more, and consider at 1 for men and 2 for women. Direct oral anticoagulants are preferred over warfarin: apixaban 5 mg twice daily (2.5 mg twice daily if two of age 80 or more, weight 60 kg or less, creatinine 133 micromol/L or more); rivaroxaban 20 mg daily with food (15 mg if creatinine clearance 15 to 49 mL/min); edoxaban 60 mg daily (30 mg if creatinine clearance 15 to 50 mL/min, weight 60 kg or less, or interacting drugs); dabigatran 150 mg twice daily (110 mg if age 80 or more or high bleeding risk). Warfarin (target INR 2.0 to 3.0, start 5 mg daily and adjust) is required in moderate to severe mitral stenosis and mechanical valves. Aspirin is not an adequate alternative. Left atrial appendage occlusion for those with contraindication.
• Modifiable factors: control blood pressure (under 130/80 mmHg), alcohol abstinence or minimum, weight loss, treatment of sleep apnoea, exercise, diabetes control, treatment of thyroid disease and heart failure.
• Acute atrial fibrillation with a clear transient trigger (sepsis, surgery, thyrotoxicosis): treat the trigger; consider anticoagulation and follow up because recurrence is high.
• Heart failure with rapid atrial fibrillation: digoxin or amiodarone; avoid diltiazem and verapamil; urgent cardioversion if unstable.
• Pre-excitation with atrial fibrillation: avoid atrioventricular nodal blocking drugs; cardioversion or procainamide 10 to 17 mg/kg at 20 to 50 mg/minute; ablation.

Atrial flutter. Anticoagulate by CHA2DS2-VASc (men 2 or more, women 3 or more) with a direct oral anticoagulant; rate control with bisoprolol or diltiazem; cardioversion; catheter ablation of the cavotricuspid isthmus (success over 90%).

Multifocal atrial tachycardia. Treat the lung disease and hypoxia, correct magnesium and potassium, verapamil or metoprolol with caution in obstructive lung disease; avoid theophylline.

Block with irregular pulse. Mobitz I in the young and athletes is benign; Mobitz II and third degree block need a permanent pacemaker, as does symptomatic sinus node disease.

Monitoring. Review 1 to 2 weeks after starting treatment, then every 6 to 12 months. Check renal function and haemoglobin at least yearly on anticoagulants (every 6 months over 75 or with renal impairment), INR weekly then monthly on warfarin, ECG and QTc on antiarrhythmics, thyroid, liver and lung function on amiodarone (6 monthly), and digoxin level when toxicity is suspected.

Referral and escalation. Cardiology or electrophysiology for symptomatic or refractory atrial fibrillation, heart failure, pre-excitation, valve disease, ventricular ectopy with structural disease, or consideration of ablation. Neurology for stroke. Endocrinology for thyroid disease. Sleep medicine for apnoea.

Admission. Haemodynamic compromise, rate over 150 not controlled, acute heart failure, ischaemia, stroke, new atrial fibrillation with severe illness, drug toxicity, and syncope.

Safety netting. Return for fainting, chest pain, breathlessness, rapid palpitations, facial droop, limb weakness, speech disturbance (call emergency services at once), bleeding, black stools, or head injury on anticoagulants.

Special groups. Young people: lone atrial fibrillation needs thyroid, alcohol, drug, genetic and pre-excitation evaluation. Athletes: ectopy and sinus arrhythmia are common; atrial fibrillation is associated with endurance training. Pregnancy: avoid warfarin (use enoxaparin 1 mg/kg twice daily) and certain antiarrhythmics; cardioversion is safe.

Older adults: highest stroke risk and bleeding risk; frailty and falls are not by themselves reasons to withhold anticoagulation. Endemic regions: rheumatic mitral stenosis atrial fibrillation needs warfarin; thyrotoxicosis, anaemia, cardiomyopathy and Chagas disease are frequent.