Tachycardia Induced Cardiomyopathy

Tachycardia induced cardiomyopathy (TIC) is left ventricular systolic dysfunction caused by persistent or very frequent tachyarrhythmia, which recovers in whole or in part when the rhythm is controlled.

It occurs in two forms: a pure form in a previously normal ventricle, and an impure form in which tachycardia worsens an existing cardiomyopathy.

Causes are atrial fibrillation (commonest), atrial flutter, incessant focal atrial tachycardia, permanent junctional reciprocating tachycardia and other incessant supraventricular tachycardias, ventricular tachycardia, and frequent premature ventricular beats (burden usually over 10%, and more often over 20% to 25%).

It affects any age, and is an important reversible cause of unexplained dilated cardiomyopathy in children and adults. The diagnosis is confirmed in retrospect when ejection fraction recovers after rhythm control.

Recovery begins within weeks and ejection fraction normalises in most patients within 3 to 6 months, though ventricular dilatation may take longer.

Pathophysiology. Loss of atrial contribution, short diastolic filling, high energy use and reduced coronary flow reserve produce myocardial energy depletion, calcium handling abnormalities, extracellular matrix remodelling and neurohumoral activation. Ventricular dilatation follows.

Histological and molecular abnormalities can persist after recovery of ejection fraction, so tachycardia relapse causes rapid recurrence of dysfunction, and sudden death is reported even after recovery.

• Palpitations, exertional dyspnoea, fatigue, orthopnoea, oedema. Incessant tachycardia can be asymptomatic.
• Infants and children with incessant tachycardia: poor feeding, irritability, tachypnoea, failure to thrive.
• Rapid or irregular pulse, a third heart sound, functional mitral regurgitation and signs of congestion.
• Ambulatory ECG shows the tachyarrhythmia for much of the day, or a ventricular ectopy burden over 10%.

Red flags.

• Heart failure with ejection fraction under 40% and persistent tachycardia
• Syncope or sustained ventricular tachycardia
• Heart rate over 150/min at rest for hours
• Cardiogenic shock
• Embolic event
• Recurrence of dysfunction after previous recovery

• ECG and ambulatory ECG. Rhythm, ventricular rate, premature ventricular beat burden and morphology (outflow tract origin is common), non-sustained ventricular tachycardia. Event monitors or an implantable loop recorder for paroxysmal arrhythmia.
• Echocardiography. Ejection fraction, left ventricular dilatation, mitral regurgitation, thrombus. Repeat after rhythm control.
• Cardiac MRI. Absence of late gadolinium enhancement supports a reversible cause, and its presence suggests underlying cardiomyopathy.
• Exclude other causes. Coronary evaluation by CT or angiography, thyroid function, electrolytes, alcohol intake, HIV, iron studies, natriuretic peptide, and a family history for genetic cardiomyopathy.
• Electrophysiology study to define and treat the arrhythmia substrate.
• Diagnostic confirmation by improvement in ejection fraction by at least 10 points, or to 50% or more, after rhythm or rate control.

Differential diagnosis.

• Primary dilated cardiomyopathy with secondary arrhythmia
• Ischaemic cardiomyopathy
• Alcohol, thyroid and other toxic or metabolic cardiomyopathy
• Myocarditis
• Pacing induced cardiomyopathy
• Arrhythmogenic cardiomyopathy
• Cardiac sarcoidosis
• Peripartum cardiomyopathy
• Sinus tachycardia as a response to heart failure

Restore sinus rhythm or control the rate early. Rhythm control is the priority.

• Atrial fibrillation or flutter.
  • Catheter ablation is the preferred rhythm control strategy in heart failure with reduced ejection fraction. Success in atrial flutter (cavotricuspid isthmus) is over 95%.
  • Electrical cardioversion after 3 weeks of anticoagulation or exclusion of thrombus by transoesophageal echocardiography, with anticoagulation for at least 4 weeks afterwards.
  • Amiodarone for rhythm control: 300 mg intravenously over 1 hour (central line when possible), then 900 mg over 23 hours, maximum 1.2 g in 24 hours. Oral: 200 mg three times daily for 1 week, 200 mg twice daily for 1 week, then 200 mg once daily (maintenance 100 to 200 mg once daily), maximum 600 mg daily during loading. Thyroid and liver function every 6 months, baseline chest X-ray and lung function. Halve digoxin and reduce warfarin by 30 to 50%. Contraindicated in severe sinus node disease and high grade AV block without pacing.
  • Avoid flecainide, propafenone, dronedarone and sotalol when ejection fraction is reduced.
  • Rate control meanwhile: bisoprolol 1.25 mg orally once daily, increased every 1 to 4 weeks to 10 mg once daily, maximum 10 mg daily in heart failure. Contraindicated in cardiogenic shock, second degree or third degree AV block without a pacemaker, sick sinus syndrome and severe asthma. Add digoxin 62.5 to 125 micrograms orally once daily, maximum 250 micrograms daily, aiming for a level of 0.5 to 0.9 ng/mL taken at least 6 hours after the dose. Use 62.5 micrograms at eGFR under 30 mL/min/1.73 m2, in older adults and with low body weight. Contraindicated in pre-excited atrial fibrillation, ventricular tachycardia and high grade AV block.
  • Anticoagulation by stroke risk: apixaban 5 mg orally twice daily, reduced to 2.5 mg twice daily when at least two of age 80 years or over, weight 60 kg or under and serum creatinine 133 micromol/L or over are present. Also 2.5 mg twice daily at creatinine clearance 15 to 29 mL/min, and avoided under 15 mL/min. Maximum 10 mg daily. Long term.
  • Atrioventricular node ablation with pacing (conduction system or biventricular) for refractory rapid atrial fibrillation.
• Focal atrial tachycardia, junctional reciprocating tachycardia and AVRT. Catheter ablation is first line. Acute success is 80 to 95% for atrial tachycardia and over 90% for accessory connections. Use amiodarone orally 200 mg three times daily for 1 week, 200 mg twice daily for 1 week, then 200 mg once daily as a bridge.
• Frequent premature ventricular beats or ventricular tachycardia. Catheter ablation when burden is over 10% with reduced ejection fraction (success 70 to 90% for outflow tract foci, lower for papillary muscle and epicardial foci). Use amiodarone (200 mg orally three times daily for 1 week, 200 mg twice daily for 1 week, then 200 mg once daily) or bisoprolol 1.25 mg orally once daily, increased every 1 to 4 weeks to 10 mg, as a bridge, and defibrillate unstable ventricular tachycardia.
• Heart failure therapy. Start full tolerated therapy at once:
  • Sacubitril/valsartan 49/51 mg orally twice daily, doubled at 2 to 4 weeks to the target 97/103 mg twice daily (maximum 194/206 mg daily). Start 24/26 mg twice daily if not on an ACE inhibitor or angiotensin receptor blocker, on low doses, with eGFR under 30 mL/min/1.73 m2, or with moderate liver impairment. Stop any ACE inhibitor 36 hours before. Contraindicated with previous angio oedema, severe liver impairment and pregnancy. Check potassium and creatinine 1 to 2 weeks after each change.
  • Spironolactone 25 mg orally once daily (12.5 mg at eGFR 30 to 49 mL/min/1.73 m2), up to 50 mg daily. Check potassium and creatinine at 1 week and 4 weeks, then every 3 months. Withhold at potassium over 5.5 mmol/L and avoid at eGFR under 30 mL/min/1.73 m2.
  • Dapagliflozin 10 mg orally once daily, long term. Start at eGFR 25 mL/min/1.73 m2 or more. Withhold during acute illness with poor oral intake. Contraindicated in type 1 diabetes.
  • Furosemide 40 mg orally once daily in the morning, increased to 80 to 120 mg daily as needed (higher doses in renal impairment under specialist care). Monitor sodium, potassium and creatinine.
• After recovery. Continue heart failure therapy for at least 12 months and probably long term, because withdrawal can cause relapse. Continue arrhythmia surveillance.
• Devices. Do not implant a primary prevention defibrillator until ejection fraction has been reassessed after 3 months of effective rate or rhythm control. Use a wearable defibrillator as a bridge. Implant for survivors of cardiac arrest or sustained ventricular tachycardia not due to a reversible cause.

Special groups.

• Children: incessant tachycardia in infants usually needs paediatric electrophysiology, with ablation in selected cases and amiodarone as a bridge.
• Pregnancy: amiodarone is avoided. Use beta blockers (metoprolol tartrate 25 to 100 mg orally twice daily, maximum 200 mg daily in this setting), cardioversion when needed, and stop sacubitril/valsartan, spironolactone and dapagliflozin.

Monitoring. Echocardiography at 1, 3 and 6 months, then yearly. Ambulatory ECG at 1 and 3 months, then every 6 to 12 months to confirm control (ectopy burden under 5%). Natriuretic peptide with symptoms. Digoxin level (0.5 to 0.9 ng/mL), thyroid and liver function every 6 months on amiodarone, and potassium and creatinine after each titration.

Referral and escalation. Refer to electrophysiology for ablation. Urgent for heart failure with ongoing tachycardia, ventricular arrhythmia or syncope, and for any relapse after recovery.