Shah and Cleland both suspect that many study patients may have had diastolic "dysfunction" in their hearts -- but were not sick enough to really have diastolic heart failure.
"I think that may underlie the findings (on symptoms)," Shah said.
For now, Pieske said doctors could still consider spironolactone for diastolic heart failure patients who need better blood pressure control.
The usual treatments for the condition include lowering blood pressure with drugs such as diuretics and ACE inhibitors, and slowing patients' heart rate with beta-blockers or other medications.
"Most people with diastolic heart failure are hypertensive, and getting blood pressure under good control is very important," Cleland said.
All agreed that better treatments are needed. "There is a real need to find therapies that improve outcomes for people with this form of heart failure," Shah said.
For spironolactone, Shah said more study is needed on whether the drug affects patients' potassium levels too much, which can cause an abnormal heart rhythm. In this study, patients on the drug had a "mild" increase in potassium, on average -- but they didn't have a higher risk of serious increases, and there were no hospitalizations for it.
The study was funded by government grants, but some researchers on the work have financial ties to Aldactone maker Pfizer, Inc.
Learn more about heart failure from the Heart Failure Society of America.
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