Resynchronization for the HemodYnamic Treatment for Heart Failure Management II implantable cardioverter defibrillator - RHYTHM II ICD


The goal of the trial was to evaluate optimized vs simultaneous pacing among patients with chronic congestive heart failure (CHF) undergoing cardioverter/defibrillator implantation for cardiac resynchronization therapy (CRT).

Study Design

Study Design:

Patients Enrolled: 121
Mean Follow Up: 6 months
Mean Patient Age: Mean age 67 years
Female: 17
Mean Ejection Fraction: Mean 24.2% at baseline

Patient Populations:

Age ≥18 years, indication for implantable cardioverter defibrillator (ICD) implantation in presence of NYHA CHF class III or IV lasting for ≥6 months, an LV ejection fraction ≤35%, a QRS duration ≥150 milliseconds on the surface electrocardiogram, and capability of completing a 6-MHW test and an MLWHF questionnaire.


Ability to walk >450 m during the 6-MHW, sustained an acute coronary event or stroke within the prior 3 months, or were expected to undergo cardiac transplantation or die within the next 6 months.

Primary Endpoints:

Change from baseline to 6 months 1) distance covered during a 6-minute hall walk (6-MHW) test, 2) scores of the Minnesota Living With Heart Failure (MLWHF) quality of life (QOL) questionnaire, and 3) New York Heart Association (NYHA) CHF functional class; Freedome from CRT-D system related complications

Drug/Procedures Used:

Patients were randomized in a 3:1 ratio to either optimized (n=91) or simultaneous (n=30) biventricular pacing. Echocardiography prior to hospital discharge was used to optimize the V-V delay. Patients were followed for 6 months.

Principal Findings:

The V-V delay was 0 millisec in 28% of the optimized group. At baseline, NYHA class III was present in 92.6% of patients. At 6 months, only 29.6% of patients were in class III overall, with no difference by treatment group (26.7% for simultaneous vs 30.4% for optimized, p=NS). The majority of patients had class II at 6 months (58.6% for simultaneous vs 59.5% for optimized). Likewise, 6 minute walk test improved from baseline to 6 months overall (from 298 m at baseline to 413 m at 6 months), with no difference between groups (6 months: 429 m for simultaneous vs 407 m for optimized, p=NS). QOL measures improved from baseline (from 45 at baseline to 26 at 6 months), with no difference between groups (6 months: 23 for simultaneous vs 28 for optimized, p=NS). Survival free of adverse events at 6 months did not differ by group (p=NS).


Among patients with CHF undergoing cardioverter / defibrillator implantation for CRT, improvements were observed from baseline to 6 months in walk distance, NYHA class, and QOL, with no difference between simultaneous biventricular stimulation or optimized V-V delay.


Boriani G, et al. Randomized comparison of simultaneous biventricular stimulation versus optimized interventricular delay in cardiac resynchronization therapy. Am Heart J 2006;151:1050-8.

Clinical Topics: Arrhythmias and Clinical EP, Heart Failure and Cardiomyopathies, Noninvasive Imaging, Implantable Devices, SCD/Ventricular Arrhythmias, Acute Heart Failure, Echocardiography/Ultrasound

Keywords: Heart Failure, Defibrillators, Implantable, Cardiac Resynchronization Therapy, Echocardiography

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