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(BETHESDA, MD) – Heart failure patients who could walk farther and faster a couple of weeks after physicians adjusted their medical therapy were more likely to still be alive two years later, according to a new study in the July 4, 2006, issue of the Journal of the American College of Cardiology.
“We found that patients that increased the distance walked in six minutes after a comprehensive program during which medical therapy was optimized and an individualized training program was performed, had a better prognosis and lived a longer time compared to patients who did not increase their six-minute walking test performance. It seems that the test can explore a sort of “functional reserve” that can be elicited by our medical intervention. Patients without this functional reserve have a worse prognosis,” said Andrea Passantino, M.D., from the IRCCS Fondazione Salvatore Maugeri, Institute of Cassano Murge, in Bari, Italy.
The researchers studied 476 patients (488 were enrolled, but 12 were lost to follow-up) with chronic heart failure who had been referred to a residential rehabilitation program because of persistent or worsening symptoms, for clinical evaluation, or for evaluation for a potential heart transplant. During stays that averaged about two weeks, doctors adjusted the medical therapy of the patients.
At the beginning of the stay and again before discharge, the researchers measured how far each patient could walk in six minutes. On average, the distance walked by patients increased from 326 meters ± 107 meters (1,070 feet ± 351 feet) to 408 meters ± 109 meters (1,339 feet ± 358 feet).
The patients who increased their walking distance by more than 70 meters (230 feet) had significantly better survival rates. After one year, 96 percent of those who showed more improvement were alive compared with 90 percent of those who did not improve their walking distance by at least 70 meters. After two years, 88 percent of the more-improved walkers were still alive, compared with just 76 percent of the less-improved walkers. Each 50-meter (164-foot) between-test improvement in distance walked resulted in a 23 percent increased likelihood of survival.
When the researchers looked more closely at their results, they saw that the walking test results were best at predicting the survival of the patients who were weaker at the beginning of the rehabilitation stay. The difference in survival was statistically significant only in the sub-group of patients that walked less than 340 meters (1,115 feet) during their initial tests. In other words, an improvement in walking test results was not as good a predictor of survival for those patients who could already walk at least 340 meters when they arrive at the rehabilitation facility.
Although the six-minute walking test is often used to assess the health and functional ability of heart failure patients, this is the first study to show that this simple test has the power to predict the survival of chronic heart failure patients.
“I’d suggest clinicians evaluate the six-minute walking test before and after optimizing medical therapy and after a short physical training program to get the best prognostic performance from the test,” Dr. Passantino said.
Some of the patients also underwent cardiopulmonary exercise testing on a treadmill. Although this test is also used routinely to assess heart failure patients and their treatment, the researchers were surprised to find that the cardiopulmonary exercise test results did not predict which patients were more likely to survive. Dr. Passantino noted that most of the studies of cardiopulmonary exercise testing were done years ago, before the widespread use of beta-blocking drug therapy. The researchers also noted that the two types of tests should be seen as complementing each other.
Dr. Passantino pointed out that this study involved only heart failure patients who were enrolled in a residential rehabilitation program and that, based on just this study, they do not know if six-minute walking test results could also predict survival among heart failure patients who are treated as outpatients.
Ronnie Willenheimer, M.D., Ph.D. from Lund University in Malmö, Sweden, who was not connected with this study, said the results provide an important advance in knowledge in this field and may be of substantial clinical importance.
“This is the first time the prognostic value of change in sub-maximal exercise capacity in patients with heart failure has been assessed,” Dr. Willenheimer said. “Since the test is simple to perform at any hospital, and the result is immediately available, it could easily be incorporated into clinical practice.”
“The next step would be to investigate if patients who do not respond favorably, in terms of change in walk distance, to change in medication, may benefit from more vigorous efforts to optimize medication and/or other treatment options. However, for now, we know that failure to respond to pharmacological treatment optimization by a clear improvement in six-minute walk distance is likely to be an ominous prognostic sign. Conversely, a clear improvement is an indication of successful treatment optimization,” he added.###
Sources quoted in this news release do not report any potential conflicts of interest regarding this topic.
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