The purpose of this study is to understand how the pressure in the pulmonary artery changes under different conditions of posture, respiration and exertion.

This is a prospective, multi-center, observational study with enrollment up to 30 subjects at 2 U.S. sites. All study data can be collected on a single day as a one-time visit (lasting approximately 90-120 minutes).

This study is a Non-Significant Risk (NSR) Investigational Device Exemption (IDE) study as LINQ™ HF investigational RAMware is required to activate additional sensors in the Reveal LINQ ICM.

The patient will come to the clinic for a single in-office visit. PA pressure will be measured while the patient is in a variety of positions and during different respiratory exercises and after brief exertion. Data will be collected on eCRFs.

The effects of the different postures, respiration and exertion will be quantified using descriptive statistics (mean, standard deviation).

Inclusion Criteria:

• Investigator believes the patient's condition is sufficiently stable to safely participate in the study procedures
• Subject is currently implanted with a commercially available pulmonary artery pressure sensor and device communication has been reliable (recent history of successful communications with patient communication system)

Exclusion Criteria:

• Subject has a history of primary PAH

All-Cause Mortality, Serious, and Other (Not Including Serious) Adverse Events were not monitored/assessed

All-Cause Mortality, Serious, and Other (Not Including Serious) Adverse Events were not monitored/assessed.