About half of all elderly patients with a diagnosis of congestive heart failure have apparently normal systolic function, so called "heart failure with a preserved ejection fraction" or HFpEF. To date, no effective therapy for HFpEF has been found, in part because of failure to discern key pathophysiologic pathways.
An extensive amount of pre-clinical work has identified that altered sarcoplasmic reticulum (SR) Ca2+ uptake, storage, and release play a major role in the changes in cardiac relaxation associated with aging, especially regarding sequestration of Ca++ by the sarcoplasmic reticular Ca++-ATPase (SERCA2a), which causes cardiac muscle relaxation by reducing cytosolic Ca++. Istaroxime is a relatively new drug that augments lusitropic function by upregulating SERCA2a activity in the heart.
Because of the clear importance of slowed relaxation in HFpEF, and the evidence that depressed SERCA2a activity contributes to the slowed relaxation with aging, the proposed study may be establish the "impairment of SERCA2a" hypothesis as a mechanism of impaired relaxation in HFpEF subjects.
