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Cardiac Resynchronization Therapy (CRT)

By

L. Brent Mitchell

, MD, Libin Cardiovascular Institute of Alberta, University of Calgary

Last full review/revision Jan 2021
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The need for treatment of arrhythmias Overview of Arrhythmias The normal heart beats in a regular, coordinated way because electrical impulses generated and spread by myocytes with unique electrical properties trigger a sequence of organized myocardial... read more Overview of Arrhythmias depends on the symptoms and the seriousness of the arrhythmia. Treatment is directed at causes. If necessary, direct antiarrhythmic therapy, including antiarrhythmic drugs Drugs for Arrhythmias The need for treatment of arrhythmias depends on the symptoms and the seriousness of the arrhythmia. Treatment is directed at causes. If necessary, direct antiarrhythmic therapy, including antiarrhythmic... read more , cardioversion-defibrillation Direct-Current (DC) Cardioversion-Defibrillation The need for treatment of arrhythmias depends on the symptoms and the seriousness of the arrhythmia. Treatment is directed at causes. If necessary, direct antiarrhythmic therapy, including antiarrhythmic... read more , implantable cardioverter-defibrillators Implantable Cardioverter-Defibrillators (ICD) The need for treatment of arrhythmias depends on the symptoms and the seriousness of the arrhythmia. Treatment is directed at causes. If necessary, direct antiarrhythmic therapy, including antiarrhythmic... read more Implantable Cardioverter-Defibrillators (ICD) (ICDs), pacemakers Cardiac Pacemakers The need for treatment of arrhythmias depends on the symptoms and the seriousness of the arrhythmia. Treatment is directed at causes. If necessary, direct antiarrhythmic therapy, including antiarrhythmic... read more Cardiac Pacemakers (and a special form of pacing, cardiac resynchronization therapy), catheter ablation Ablation for Cardiac Arrhythmia The need for treatment of arrhythmias depends on the symptoms and the seriousness of the arrhythmia. Treatment is directed at causes. If necessary, direct antiarrhythmic therapy, including antiarrhythmic... read more , surgery Surgery for cardiac arrhythmias The normal heart beats in a regular, coordinated way because electrical impulses generated and spread by myocytes with unique electrical properties trigger a sequence of organized myocardial... read more Surgery for cardiac arrhythmias , or a combination, is used.

In some patients, the normal, orderly, sequential relationship between contraction of the cardiac chambers is disrupted (becomes dyssynchronous). Dyssynchrony may be

  • Atrioventricular: Between atrial and ventricular contraction

  • Interventricular: Between left and right ventricular contraction

  • Intraventricular: Between different segments of left ventricular contraction

Patients at risk for dyssynchrony include those with the following:

Cardiac dyssynchrony can be suspected based on electrocardiogram (ECG) parameters (eg, left bundle branch block) and advanced echocardiography techniques (eg, tissue Doppler index, strain rate).

Cardiac resynchronization therapy (CRT) involves use of a pacing system to resynchronize cardiac contraction. Such systems usually include a right atrial lead, right ventricular lead, and left ventricular lead. Leads may be placed transvenously or surgically via thoracotomy.

In patients with heart failure Heart Failure (HF) Heart failure (HF) is a syndrome of ventricular dysfunction. Left ventricular failure causes shortness of breath and fatigue, and right ventricular failure causes peripheral and abdominal fluid... read more Heart Failure (HF) who have New York Heart Association (see table NYHA classification New York Heart Association (NYHA) Classification of Heart Failure New York Heart Association (NYHA) Classification of Heart Failure ) class II, III, or IV symptoms, CRT can reduce hospitalization for heart failure and reduce all-cause mortality. However, there is little to no benefit in patients with permanent atrial fibrillation Atrial Fibrillation Atrial fibrillation is a rapid, irregularly irregular atrial rhythm. Symptoms include palpitations and sometimes weakness, effort intolerance, dyspnea, and presyncope. Atrial thrombi may form... read more , right bundle branch block, nonspecific intraventricular conduction delay, or only mild prolongation of QRS duration (< 150 millisecond).

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NOTE: This is the Professional Version. CONSUMERS: Click here for the Consumer Version
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