Exercise therapy has proven to be an effective additive therapy in patients with cardiovascular diseases. The prognostic value of physical activity is well established in patients with congestive heart failure. Therefore the investigators assumed that the population of patients with implantable cardioverter-defibrillators (ICD) with impaired left ventricular function may also benefit from a cardiovascular training in terms of improved quality of life and reduction of ventricular arrhythmia. The data on feasibility, risk and therapeutic effects of exercise training are very limited or not available.

This prospective randomized study examines the feasibility and benefits of exercise therapy in patients with ICD and congestive heart failure.

Detailed anamnesis and a clinical examination will be performed in order to determine the patient's eligibility for the study. The randomisation either to the exercise- or to the control-arm will be performed at baseline. Follow-up visits are planned after four weeks and after three months same for both arms. The close-up visit is planned after 6 months.

The exercise-arm starts off with an introduction into physical training at the Department of Sports Medicine at the University in Tübingen. Ergospirometry and 6-min walk test will be performed to determine the patients' performance. Then the patients will be encouraged to exercise at home. The scales and intensities of physical training will vary interpersonally depending on patients individual performance. Pedometers and the ICD-integrated "Cardiac Compass" function will be used to verify work load, intensity and duration of the physical strain. The patients will be consulted by telephone regularly to affirm the study compliance. The physical activity in the control-arm will be monitored using the ICD-integrated "Cardiac Compass" function.

ICD-programming

• VT/SVT discrimination "on",
• "Cardiac Compass" feature "on"
• VT/VF detection and pacing-programming remain adjusted to clinical situation of the patient

Baseline- and follow-up visits

• Anamnesis, NYHA-stadium, patients' demographic data: sex, age, weight, hight, concomitant diseases and current medication
• Clinical examination: weight, inflow-congestion, edema, pulmonary signs of cardiac decompensation
• Chest- x-ray (baseline, 6 moths FU)
• 6-min walk test (baseline, 6 moths FU)
• Blood take (baseline, 6 moths FU) standard examinations including blood morphology, troponin, renal retention parameters, transaminases)
• Determination of the BNP plasma level
• Echocardiography (baseline, 6 moths FU): left-ventricular function (EF) and diameter, valvular function, estimating of systolic pulmonary arterial pressure (PAP sys.).
• Ergospirometry (baseline, 6 moths FU):peak-oxygen-uptake-volume, starting at 10 Watt with increase of the work load 12 Watts per minute until the work load capacity has been reached. The achieved VO2 value is defined as the 100 % oxygen-uptake. At home the patients are supposed to exercise at about 70 % of their VO2 peak.
• Measurement/Recording of the peripheral oxygen-uptake of the muscle with near-infrared-spectroscopy simultaneously with the bicycle-ergometric exposure.
• Complete interrogation of the ICD-memory, acquisition of the "Cardiac-Compass"-data, sensing- and threshold-test, recording of electrical impedance and checking of the battery-status, impedance and checking of the battery-status
• Acquisition of the standardized questionnaires concerning quality-of-life, personality, depression and anxiety: PHQ-D, DS14, FSGV 1.0 and GAD-7.

Definition of adverse event

• Adverse event (AE): Any decrease of existential orientation, unwanted incidence, subjective or objective symptom of any kind of disease, impairment or any accident, that may or may not be connected to the study is defined as an (AE).
• Severe adverse event (SAE): A SAE is an event which is life-threatening or deadly, causes significant or chronic damage, requires hospitalization or threatens the patient's physical inviolability in any other way.

Inclusion Criteria:

• both gender at a minimum age of 18 years
• ICD-systems with "Cardiac-Compass" (Medtronic)-diagnostic feature
• ICD system implanted for at least three months
• congestive heart failure, NYHA II and III
• LVEF ≤ 40 %
• compensated state, optimized and stable pharmacological therapy at least for the last three months
• load capacity of at least 50 watt at baseline.

Exclusion Criteria:

• unable or unwilling to give informed consent
• acute coronary syndrome during the past thirty days
• hemodynamically relevant valvular defect
• instable arterial hypertension
• severe COPD
• reduced work load capacity caused by instable angina pectoris, peripheral vascular, neurological or orthopaedic concomitant disease
• hypertrophic obstructive cardiomyopathy (HOCM)
• pulmonary-arterial hypertension (PAP systolic ≥ 60 mmHg).