Refers to biventricular pacing with multisite pacing incorporating an atrial lead, a right ventricular and left ventricular lead.
Designed to eliminate the delay in activation of the LV free wall found in many patients with LV systolic dysfunction to improve mechanical synchrony, increase LV filling time, reduce mitral regurgitation and reduce septal dyskinesis.
Cardiac resynchronization seeks to restore synchrony in the left ventricle that has been impaired by prolonged conduction in heart failure with reduced ejection fraction.
Indicated for patients on stable medical therapy with moderate to severe heart failure, left ventricular ejection fraction of 35% or less, and the QRS duration of 120 ms or more as assessed electrocardiographically.
Cardiac re-synchronization therapy reduces mortality and heart failure outcomes in patients with symptomatic heart failure, reduces the ejection fraction, and a wide QRS complex.
The implantation of a cardiac resynchronization device is a lifelong intervention.
The left ventricular lead is usually placed through a coronary vein, or via surgical placement, and preferably in the lateral wall of the left ventricle.
Use in patients with heart failure and cardiac dyssynchrony results in improved symptomatology, and reduces complications and risks of death.
The MultiCenter InSync Randomized Clinical Evaluation (MIRACLE) study revealed synchronized biventricular pacing results in improved atrioventricular conduction and interventricular mechanical function in CHF.
Reduces atrioventricular delay and improves left ventricular filling time, shortens intraventricular mechanical delay, decreases isovolumic contraction time in CHF.
In patients with NYHA class III or IV heart failure cardiac resynchronization improves symptoms and enhances functional class.
The use of cardiac resynchronization improves heart function in patients with mild heart failure (NYHA class I or II) and reduces hospitalizations for heart failure (Linde C et al, Moss AJ et al).
2008 guidelines suggest that implantation of cardiac devices, CRT with or without ICD is a class one indication for patients with left ventricular ejection fraction of less than 35%, a QRS duration of 120msec, with sinus rhythm and have a New York Hospital Association functional class III or ambulatory class IV heart failure symptoms, while receiving optimal medical therapy.
Increases exercise capacity in most patients with CHF.
Trials show improvement in morbidity and mortality when used alone or with implantable cardioverter defibrillator in CHF.
Promotes left ventricular remodeling and cardiac function in CHF.
Useful for patients with NYHA class 3 or 4 heart failure despite medical management, with LVEF of 35% or less, in the presence of sinus rhythm, and with prolonged QRS duration (ventricular dyssynchrony).
With implantable cardioverter-defibrillator decreases the risk of heart failure events in relatively asymptomatic patients with low ejection fraction and wide QRS complex.
Reduces clinical events including death in patients with prolonged QRS duration on electrocardiogram.
Recommended in patients with systolic heart failure, NYHA class 3 or 4 symptoms, and a QRS duration of 120 milliseconds or greater.
About one third of patients with systolic heart failure patients have a QRS duration above 120 milliseconds.
An effective adjunct to therapy to medication management and reducing the rate of hospitalization in symptomatic patients with advanced heart symptoms, New York Heart Association class III or four, and ejection fraction of less than 35% or less, and then atrioventricular conduction delay of 120 ms or more.
The Multicenter Automatic Defibrillator Implantation Trial with Cardiac Resynchronization Therapy ( MADIT-CRT) study 1820 patients with an ejection fraction of less than 30%, a QRS duration of the 130 msec or more, and New York Heart Association class I or II symptoms combining CRT, and ICD decreased the risk of heart failure in such patients.
The Multicenter Automatic Defibrillator Implantation Trial with Cardiac Resynchronization Therapy ( MADIT-CRT) study there was a 41% reduction in the risk of heart failure events and the finding was most evident among patients with the QRS duration of 150 ms or more.
In the above study the relative reduction of 41% in the risk of nonfatal heart failure events and was restricted to patients with LBBB ECG pattern.
A meta-analysis of 5 studies indicated CRT was effective in reducing adverse clinical events in patients with heart failure and a baseline QRS interval of 150 millisecond or greater, but does not reduce events in patients with a QRS of less than 150 milliseconds.
The Multicenter Automatic Defibrillator Implantation Trial with Cardiac Resynchronization Therapy ( MADIT-CRT) study was associated with a 34% reduction in the risk of death or heart failure events compared to the use of ICD alone.
The Multicenter Automatic Defibrillator Implantation Trial with Cardiac Resynchronization Therapy ( MADIT-CRT) study the superiority of CRT was evident in patients with ischemic cardiomyopathy and in patients with non-ischemic cardiomyopathy.
The Multicenter Automatic Defibrillator Implantation Trial with Cardiac Resynchronization Therapy ( MADIT-CRT) study showed reductions in left ventricular end diastolic and end systolic volumes and improvement in ejection fraction, one year after initiation of combined therapy.
At 7 years of follow-up in the MADIT-CRT study in patients with mild heart failure, left ventricular dysfunction, and left bundle branch block, early intervention with CRT-D was associated with a significant long term survival benefit (Goldenberg I et al).
In a randomized controlled trial, Resynchronization-Defibrillation for Amulatory Heart Failure Trial (RAFT) to determine whether the addition of CRT to an ICD and optimal medical treatment program in patients with NYHA class II or III symptoms, LV systolic dysfunction and a wide QRS complex would reduce mortality and rate of rehospitalization for heart failure: the addition of CRT reduced death rates and hospitalizations for mild to moderate heart failure (Tang A et al).
In patients with systolic heart failure and QRS duration of less than 130 ms, CRT does not reduce the rate of death or hospitalization for heart failure and may increase mortality (Echo CRT study group).
Among patience with reduced ejection fraction, a widened QRS, complex, and NYHA class II or III heart failure, the survival benefit associated with the receipt of a cardiac reesynchronization device as compared with implantable cardioverter defibrillator appears to be sustained during the median of nearly 14 years of follow up (RAFT long-term study team).