Mode Selection Trial (MOST) in sinus node dysfunction - MOST

Description:

The Mode Selection Trial (MOST) is a single-blind study supported by the National Heart, Lung, and Blood Institute designed to enroll 2000 patients with Sick Sinus Syndrome. All patients will receive a DDDR pacemaker programmed to VVIR or DDDR before implantation. The average time of follow-up will be 3 years. MOST has a >90% power to detect a 25% reduction in the primary end point—nonfatal stroke or total (all cause) mortality—in the DDDR-treated group. Secondary end points will include health-related quality of life and cost effectiveness, atrial fibrillation, and development of pacemaker syndrome. Prespecified subgroups for analysis will include women and the elderly. Enrollment was completed in October 1999, with a total of 2010 patients

Hypothesis:

Pacemaker technology permits the selection of ventricular (single-chamber) or dual-chamber devices for the treatment of sinus node dysfunction. However, clinical and outcomes data are inadequate to support a clear recommendation that one or the other type of device be used.

Study Design

Study Design:

Patients Enrolled: 2010
Mean Follow Up: 3 years
Female: 50

Patient Populations:

Inclusion criteria include: (1) clinical diagnosis of SSS requiring permanent pacemaker implantation; indications for pacing acceptable for study inclusion include one or more of the following: symptomatic SSS with a documented sinus pause >3 seconds or an asymptomatic sinus pause >5 seconds; chronic sinus bradycardia with rates <50 beats/min, an inability to increase rate >80 beats/min with exercise, and symptoms of fatigue and dyspnea on exertion referable to chronotropic incompetence; and sinus bradycardia, rate <50 beats/min, which restricts the use of long-term medical therapy for angina, hypertension, or supraventricular tachyarrhythmias; (2) Sinus mechanism or atrial standstill at the time of implant; (3) age >21 years without an upper age limit; (4) dual-chamber pacemaker being implanted by an endocardial transvenous approach; and (5) informed consent

Exclusions:

Exclusion criteria include (1) inadequate acute atrial endocardial capture or sensing thresholds: P-wave amplitude <1.5 mV or atrial capture threshold >2.5V at 0.5 ms pulse amplitude; (2) chronic atrial fibrillation without any documented sinus mechanism for >6 months; (3) clinically overt congestive heart failure (after successful treatment, the patient may be re-evaluated for participation in MOST); (4) malignancy expected to limit the patient’s life span during the course of the trial; and (5) severe psychiatric illness likely to limit study participation

Primary Endpoints:

First occurrence of nonfatal stroke or all cause mortality. Based on the studies already quoted and on pilot study data, 21 the 1-year primary end point rate is projected to be 11.9% in the VVIR-paced group. MOST is designed to have a >90% power to detect a 25% reduction in the primary end point in the DDDR-treated group.

Secondary Endpoints:

Secondary end points will include health-related quality of life and cost effectiveness, atrial fibrillation, and development of pacemaker syndrome

Drug/Procedures Used:

All patients will receive a DDDR pacemaker noninvasively programmed to VVIR or DDDR before implantation

References:

American Heart Journal 2000;140:541-51.

Clinical Topics: Arrhythmias and Clinical EP, Heart Failure and Cardiomyopathies, Prevention, Implantable Devices, EP Basic Science, SCD/Ventricular Arrhythmias, Atrial Fibrillation/Supraventricular Arrhythmias, Hypertension

Keywords: Stroke, Cost-Benefit Analysis, Follow-Up Studies, Dichlorodiphenyldichloroethane, Sick Sinus Syndrome, Single-Blind Method, Dyspnea, Tachycardia, Quality of Life, Cardiomyopathies, Heart Block, Bradycardia, Hypertension


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