Monitoring Pulmonary Artery Pressure by Implantable Device Responding to Ultrasonic Signal

Inclusion Criteria: * Patients who exhibit signs and symptoms of NYHA Class III or IV heart failure. * Patients who are able to visit the clinic frequently during the 6 months following implantation. * Patients who are willing and able to perform all follow-up procedures. Exclusion Criteria: 1. Patients under the age of 18 2. Pregnant women or women that plan to get pregnant during the study. 3. Patients with, tricuspid or pulmonic stenosis, pulmonary stents, right sided mechanical heart valves 4. Contraindication to antiplatelet therapy (aspirin and clopidogrel) 5. Patients suffering from active infection (on antibiotic therapy) 6. Known intracardiac mass (right atrial or right ventricular) 7. Patients who have been implanted with a VAD 8. Patients who are candidates for listing for heart transplantation if it is deemed that they have a possibility of receiving a heart within the next 6 months 9. Patients that have lead implanted at the heart right side of the heart within the last 6 months 10. Patients with any terminal illness, or with a life expectancy of less than 6 months 11. Patients that are unable to lie flat for the duration of the procedure 12. Patients that are unable to operate the home unit (due to physical or mental constrain) 13. Patients after pneumonectomy 14. Patients treated with oral anticoagulants INR \> 1.5 prior to catheterization 15. Patients with severe chronic renal failure (creatinine \> 2.5 mg/dl) 16. Patients suffered from acute myocardial infarction within the three months prior the study 17. Patients that underwent open heart surgery within 4 weeks prior the study.