New Heart Therapy Ain't All That

Aldosterone antagonist therapy may not be as effective as trials showed

(RxWiki News) New drugs are always tested for safety and effectiveness in trials before the FDA approves them. But this doesn't mean they are effective for everyone for a particular condition.

Sometimes, the patients in the trials are very different from other patients with the same condition. Doctors may see medications not working as well in real life as they did in trials.

This has been the case with aldosterone antagonist therapy for older heart failure patients.

"Ask a cardiologist questions about your treatment."

A recent study showed that older patients receiving this therapy did have lower rates of heart failure after leaving the hospital, but they had a higher rate of a dangerous condition called hyperkalemia.  

The rates of death or other heart-related hospital admissions were no different for those who received the therapy compared to those who didn't.

The study, led by Adrian F. Hernandez, MD, MHS, of the Duke Clinical Research Institute at Duke University School of Medicine, looked at how effective aldosterone antagonist therapy is for older heart failure patients. Dr. Hernandez and colleagues reviewed Medicare claims from 2005 through 2010 for 5,887 patients with an average age of 77.

All the patients had been hospitalized with heart failure and reduced ejection fraction. Reduced ejection fraction means that less blood is being pumped out of one or both of the heart ventricles to the rest of the body. Of all the patients studied, 1,070 (18 percent) began aldosterone antagonist therapy after they were discharged.

When the researchers compared the outcomes of those who were receiving aldosterone antagonist therapy and those who were not, they found the rate of death was very similar.

While 49.9 percent of those receiving the treatment died, 51.2 percent of those who were not treated with the therapy died.

Similarly, 63.8 percent of the treated patients were readmitted to the hospital for cardiovascular issues, and 63.9 percent of the untreated patients were readmitted. When the researchers looked at which patients were readmitted for heart failure within three years of their discharge, 38.7 of the treated patients were readmitted, compared to 44.9 percent of untreated patents.

Within the first month after discharge, 2.9 percent of patients receiving aldosterone antagonist therapy were readmitted for hyperkalemia, a condition where higher blood levels of potassium can lead to irregular and possibly fatal heart rhythms. Only 1.2 percent of the untreated patients were readmitted for hyperkalemia within a month of discharge.

When the researchers looked at readmission for hyperkalemia within a year after discharge, 8.9 percent of patients receiving aldosterone antagonist therapy were readmitted, compared to 6.3 percent of untreated patents.

So even though there was a lower rate of readmission for heart failure among the aldosterone antagonist therapy patients, there was no real difference between the groups in terms of death rates and readmission for other cardiovascular readmissions. And there was a higher rate of hyperkalemia in those getting the aldosterone antagonist therapy.

According to Sarah Samaan, MD, a cardiologist with Legacy Heart Center in the Dallas/Fort Worth area, the difference between the results of past trials and the results of this study has to do with how populations are selected for drug trials.

"When randomized controlled research studies are performed, the patients enrolled are very carefully selected, and often more complex patients are excluded," Dr. Samaan said. "This study was observational, so all patients meeting the criteria were included, and thus they are representative of the more typical and complicated patients that cardiologists working in the community care for every day."

She said that patients taking these drugs and patients with below-normal kidney function (not uncommon among older adults) are at a higher risk for increased potassium levels.

"Doctors are sometimes reluctant to prescribe this class of drugs since they can raise potassium levels, especially when combined with ACE inhibitors or ARBs, which are generally considered standard of care treatment for patients with heart failure," Dr. Samaan said. 

"For this reason, routine measurement of blood levels is necessary, especially in the first few months after the drugs are started," she said. "This means that our patients must be reliable enough to come in and get the blood work done."

If a patient does have hyperkalemia, coming in regularly for blood work will help the doctor catch the condition sooner.

The study was published November 27 in JAMA. The research was funded by the Agency for Healthcare Research and Quality and the US Department of Health and Human Services. Several authors declared they have received funding or compensation from multiple pharmaceutical companies.

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Review Date: 
November 26, 2012