(Reuters Health) - A study designed to look for differing outcomes when black and white U.S. veterans undergo a common procedure to clear blocked heart arteries instead found no differences once so-called confounding factors were taken into account.
Although an unadjusted analysis found that blacks treated in the Veterans Affairs health system had a higher one-year mortality rate - along with higher rates of blood transfusion within 30 days or heart attack within a year of the procedure - those disparities dissolved once things like coexisting illnesses, characteristics of the procedure and severity of the blockage were factored in.
The exception: The odds of acute kidney injury were 22 percent higher among blacks at the 30-day mark, even with the adjustments.
Previous research has shown that race can have a major influence on the likelihood of being referred for artery imaging or for the artery-clearing procedure - known as percutaneous coronary intervention, or PCI. Black Medicare recipients also tend to have higher mortality rates after PCI, even after socioeconomic factors have been taken into account.
"This study represents the largest modern analysis to date of the influence of race on cardiovascular outcomes among U.S. veterans," the team, led by Dr. Taisei Kobayashi of the Cpl. Michael Crescenz Veterans Affairs Medical Center in Philadelphia, writes in JAMA Cardiology.
All but one of the 17 authors list an affiliation with the VA health system.
More than 42,000 patients treated at 63 VA hospitals were included in the analysis and the patients received their PCI anytime between October 2007 and September 2013. Patients who identified themselves as something other than black or white were not included in the calculations. Blacks made up 13.3 percent of the group and nearly all of the study subjects were men.
Without adjustments for confounders, the one-year mortality rates were 7.1 percent for blacks and 5.9 percent for whites. Heart attack rates at one year were 3.3 percent for blacks and 2.7 percent for whites, and 30-day blood transfusion rates were 3.4 percent for blacks versus 2.7 percent for whites.
After adjustment, these differences were reduced to the point where they were no longer statistically significant, meaning they could have been due to chance.
The most common complication studied was the 30-day rate for acute kidney injury. Unadjusted, it happened in 20.8 percent of blacks and 13.8 percent of whites. Although the rate of chronic kidney disease was much higher among black patients to begin with at 28.9 percent versus 17.4 percent among whites, the disparity in kidney injury rates persisted after adjustment for kidney disease and other factors.
A patient was judged to have an acute kidney injury if at least one creatinine level in the first 30 days was at least 0.3mg/dL above baseline.
Thirty-day all-cause readmission rates were comparable between the groups at 13.6 percent for blacks and 12.9 percent for whites.
"Black patients had a higher burden of several medical comorbidities, including heart failure, chronic kidney disease, hemodialysis, diabetes, peripheral artery disease, posttraumatic stress disorder and tobacco use," the Kobayashi team writes.
Black patients, for example, were more likely to be initially seen in the cardiac catheterization laboratory with acute coronary syndrome (chest pain) and were more likely to be undergoing PCI under emergency conditions, they note.
The researchers did uncover some differences in care that were statistically significant even after adjustment.
Blacks were 23 percent more likely to receive bare metal stents and 12 percent less likely to receive a blood pressure drug known as a beta-blocker following their procedures. The researchers characterized those treatment patterns as "modestly different" and, based on current research, not a major factor in outcomes.
Past studies on veterans have found beta-blockers to be less effective at lowering blood pressure in black patients, the authors point out, and results of those studies might be influencing prescribing patterns after PCI. “Most important,” they add, while beta-blockade is important for patients having a heart attack, it doesn’t clearly improve survival in patients with stable coronary artery disease.