Combined, average percentage improvement in 6-minute walk test distance and Minnessota Living With Heart Failure Quality of Life score from baseline to 6-month follow-up for the Protos DR/CLS (Group 1) and Stratos LV (Group 2) compared with the active control (Group 3). The 6-minute walk test is a test that measure how far a patient can walk in 6 minutes in a standardized walking course. Percent Change (0% (worst)-100% (best))

Patients included in this analysis are those patients with complete six minute walk test and Quality of Life data at both baseline and the six-month follow-up.

Complication-free rate was evaluated in an equivalence (non-inferiority) format compared to a target of 85% minus delta (10%), where delta is the clinically significant difference for establishing equivalence. This endpoint evaluated system-related complications.

Complication-free rate was evaluated in an equivalence (non-inferiority) format compared to a target of 85% minus delta (10%), where delta is the clinically significant difference for establishing equivalence. This endpoint evaluated system-related complications. All Stratos systems (in both the biV and RV pacing arms) were evaluated together as pre-specified in the protocol.

Subjects with paired baseline and 6-month six-minute walk test data.

Quality of Life was evaluated using the Minnesota Living with Heart Failure (MLHF) Quality of Life (QOL) Questionnaire.The questionnaire consists of 21 questions to measure the subjects' perception of how their HF and its treatment affected their ability to live as they wanted during the last month. The questions describe different ways in which some people are affected (i.e. physical, socioeconomic, and psychological impairments). If a question does not apply to a subject or is not related to their HF, then they can answer with a 0. If it does apply to them, then they can rate (from 1 to 5) how much it has affected them. From the 21 questions, the lowest possible total score is 0, and the highest possible total score is 105. A lower score is desirable. This outcome was calculated as QOL score at baseline minus QOL score at 6 months. Therefore, a positive change in QOL score represents an improvement in quality of life, while a negative change in QOL score represents a worsening.

Subjects with paired baseline and 6-month QOL data. A positive score represents improvement from baseline to 6-months.

Subjects with paired baseline and 6-month echocardiography data.

The purpose is to evaluate the change in the participant's NYHA classification.

There are four NYHA classes:

Class I: Patients with cardiac disease, but without resulting limitation of physical activity. Ordinary physical activity does not cause undue fatigue, palpitation, dyspnea, or anginal pain.

Class II: Patients with cardiac disease resulting in slight limitation of physical activity. They are comfortable at rest. Ordinary physical activity results in fatigue, palpitation, dyspnea, or anginal pain.

Class III: Patients with cardiac disease resulting in marked limitation of physical activity. They are comfortable at rest. Less than ordinary activity causes fatigue, palpitation, dyspnea, or anginal pain.

Class IV: Patients with cardiac disease resulting in inability to carry on any physical activity without discomfort. Symptoms of cardiac insufficiency or of anginal syndrome may be present even at rest. If any physical activity is undertaken, discomfort is increased.

Subjects with paired baseline and 6-month NYHA classification data. The outcome of "Improved at least 1 Class" represents a numerically higher NYHA class at baseline than at 6 months (e.g. NYHA class III at baseline changed to NYHA class II at 6 months).

Subjects successfully implanted with investigational system.

Subjects enrolled

Subjects with paired baseline and 6-month echocardiography data.

Subjects with paired baseline and 6-month echocardiography data.

Subjects with paired baseline and 6-month echocardiography data.

Subjects with paired baseline and 6-month echocardiography data.