Veterans Affairs Trial Fails to Establish Lower Haemoglobin as Protective Against Cardiovascular Events: Presented at ADA

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Title: Veterans Affairs Trial Fails to Establish Lower Haemoglobin as Protective Against Cardiovascular Events: Presented at ADA
URL: http://www.pslgroup.com/dg/223432.htm
Doctor's Guide
June 9, 2008

By Ed Susman

SAN FRANCISCO -- June 9, 2008 -- There was no statistical difference in cardiovascular outcomes between aggressive and standard strategies used to lower glucose, according to results of a long-term study conducted in 20 United States' Veterans Affairs (VA) facilities, researchers said here at the American Diabetes Association (ADA) 68th Scientific Sessions.

The results of the Veterans Affairs Diabetes Trial (VADT) mirrored those of 2 other studies reported here; all of which failed to show that intensive lowering of glycated haemoglobin (Hb A1C) levels offered protective benefits against events such as heart attack, stroke, or other major vascular disorders.

"This was a complicated study, in which all outpatients had multiple health problems, including 40% with prior cardiovascular events," said Carlos Abraira, MD, Miami VA Medical Center and University of Miami Miller School of Medicine, Miami, Florida, speaking at a presentation here on June 8.

Dr. Abraira and colleagues aggressively treated cardiovascular risk factors such as high cholesterol and high blood pressure in the 1,791 type 2 diabetes patients in the study. He noted that such a good job was done that far fewer cardiovascular events than expected occurred in the 7.5-year study. The mean time under treatment was 6 years.

That control of risk factors may have sabotaged the possibility of finding out if lowering Hb A1C to less than 6.9% was more effective than the less aggressive approach, which lowered Hb A1C to 8.5%. The mean Hb A1C at baseline in these subjects was 9.5%.

Investigator William Duckworth, MD, Carl T. Hayden VA Medical Center, Phoenix, Arizona, noted that, "While we found that treatment of patients with type 2 diabetes suggested some [cardiovascular] benefits from glucose control, it did not reach significance for a reduction in the primary endpoint -- a combination of specified cardiovascular disease events -- in this population."

Investigators expected that there would be about 650 to 700 cardiovascular events in the study, said Dr. Duckworth, but during the 7.5 years, 231 events occurred in the intensive-therapy group and 263 in the standard-therapy group. That rate may have been due to excellent blood-pressure control (mean of 127/70 mm Hg) and cholesterol levels that approached American Diabetes Association goals, he added.

While there was a 1.5% difference between the treatment groups in Hb A1C control, Dr. Duckworth noted, there was no difference in deaths. Episodes of severe hypoglycaemia that caused near or complete loss of consciousness were related to cardiovascular events.

In a separate analysis, Thomas Moritz, MS, Hines VA Hospital, Hines, Illinois, said the researchers specifically examined whether there were signals of cardiac risk with the drug rosiglitazone, but found no indication of any hard evidence. (Recent meta-analyses have suggested there was a possible signal of cardiovascular risk among patients on rosiglitazone, the most extensively used drug in the VADT trial.)

A comparison of events in the trial appeared to show no harm among patients on rosiglitazone, Moritz said, and there was possibly an indication of benefit among those more aggressively treated with the drug.

Frank Zangeneh, MD, George Washington University, Washington, DC, who did not participate in the trial, suggested during the presentation that the trial design -- modelled on statin trials -- may not work in diabetes, and resulted in the nonsignificant results.

Dr. Zangeneh commented, "While the VADT did not meet its primary endpoint, it is critical that these results do not detract from what we already know about the benefits of long-term blood-sugar control on other serious and potentially life-threatening complications of diabetes -- such as kidney failure, blindness, and amputation."

Dr. Zangeneh added that the data on rosiglitazone in the trial also should be reassuring to doctors and patients that the drug is safe. He noted that, over the course of all the trials, Data Safety and Monitoring Boards did not find any signal of alarm over use of the drug.

[Presentation title: Glycemic Control and Cardiovascular Outcomes - The VA Diabetes Trial.]

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