Inclusion Criteria:  Aged 18 years and older Patient or healthcare proxy willing to give written informed consent to participate Presence of an implanted CardioMEMS device or imminent implantation of a CardioMEMS device Expressed willingness to take DUO recordings immediately before or after taking their CardioMEMS measurements, on the same schedule prescribed by their physician Functioning iOS or Android smartphone or tablet that can download and run the companion Eko application Access to WiFi or cellular data connection at home  Exclusion Criteria:  Patient or healthcare proxy is unwilling or unable to give written informed consent Patient is enrolled in another study that may interfere with the observations from this study Acute pericarditis Healing chest wall wounds (e.g., sternotomy or thoracotomy)