By Annette M. Boyle
WASHINGTON — Veterans discharged with a diagnosis of acute kidney injury (AKI) have twice the mortality rate of those diagnosed with myocardial infarction (AMI), yet a lack of awareness and treatment options limit physicians’ ability to manage the condition.
Acute kidney injury, which most often occurs following major surgery, trauma or severe infection, frequently has no symptoms, but it often has long-lasting repercussions, according to the recent study published in the Clinical Journal of the American Society of Nephrology (CJASN). 1
“If you had to be in a hospital with acute kidney injury or a myocardial infarction, you’re better off with the AMI,” said lead author Lakhmir “Mink” Chawla, MD, a nephrologist with the Washington, DC, VAMC and associate professor of medicine at George Washington University Medical Center. “An AKI tends to set off a more lethal series of events.”
Chawla and colleagues analyzed 36,980 records of patients discharged from VA facilities between October 1999 and December 2005 with diagnoses of AKI or AMI. The VA Beneficiary Identification Records Locator Subsystem Death File provided the date of death.
The researchers divided the patients into three categories: those who had a diagnosis of only AKI, those with only AMI and those with both conditions and compared the rates of major adverse cardiac events (MACE), major adverse kidney events (MAKE), major adverse renocardiovascular events (MARCE) and death among the three groups.
AKI Far More Deadly
“Unadjusted clinical epidemiology data shows that patients with AKIs had mortality rates of 15% to 35%, while those with MIs had mortality rates of 5% to 15%. We’ve always thought that AKI was the end result of multiple organ failure in older and sicker patients, but when we adjusted for those factors, there is still a startling difference in mortality rates,” Chawla told U.S. Medicine.
Patients with AKI fared much worse even compared to patients with the most dangerous type of heart attacks, ST-elevation myocardial infarctions (STEMIs). “Patients with AKI alone were more than twice as likely to die than patients with a STEMI alone,” wrote the authors.
The seriousness of AKI is not generally well-known, Chawla noted. “MI gets enormous press. People know about it. They see defibrillators in elevators and in major buildings. They talk to their doctors about statins. But even as awareness has increased, we’ve gotten better at treating it, so mortality from AMI now is well under 5% — and we have 30 drugs to treat acute coronary syndrome.”
AKI remains in the shadows still. “We have zero drugs to treat acute kidney injury, and people don’t know about it. But as they live longer, they are more likely to have major surgery and increased risk of AKI. It’s not that myocardial infarction isn’t serious, but as a public health hazard, acute kidney injury is far more deadly,” Chawla said.
In fact, Chawla’s study might understate the seriousness of AKI, he noted. The study followed patients for a maximum of six years and a mean of 1.4 years. “If we had been able to follow-up all the patients for a full six years, all the numbers would have been worse, because there would have been more time for bad things to happen,” he pointed out.
Even so, the data clearly shows that AKI by itself has a devastating impact on patient health and that AKI substantially increases the mortality rates for patients with AMI. During the study period, death occurred most often in patients who had both AKI and AMI (57.5%) and least often in those who had AMI alone (32.3%).
Patients with AMI and AKI also had a higher risk of subsequent major adverse coronary events and were twice as likely to have a subsequent admission for congestive heart failure as patients with AMI alone. The reverse effect also occurred: Patients with AKI and AMI were more likely to have subsequent major adverse kidney events than those that had only AKI.
“The data indicate a bidirectional effect between the heart injuring the kidney and the kidney injuring the heart,” Chawla observed. “If you have AKI with MI, everything is worse.”
In some instances, AKI may indicate a generalized increased severity of illness in a patient. “However, many of the observed MARCE events occur months to years after the index hospitalization, suggesting that acute cardiorenal injury may induce a vicious cycle that persists long after the acute event,” the authors noted. Some studies indicate that AKI can cause cardiac cell apoptosis and cardiac leukocyte infiltration.
“We need concerted effort in this research space, like we’ve had in myocardial infarction. They have had progress because of focus, where we have not,” Chawla said. The most striking result of the study, that an “exposure” of AKI creates a greater risk of severe renal and cardiovascular outcomes than an “exposure” of MI, may attract increased attention to its prevention and the ongoing monitoring of patients.
“The findings from this study will be critical for planning future interventional trials in patients with AKI,” said Chawla. “Because AKI remains an ongoing and increasing public health hazard, more research into the treatment and management of this syndrome is critically required.”
1 Chawla LS, Amdur RL, Shaw AD, Faselis C, Palant CE, Kimmel PL. “Association Between Acute Kidney Injury and Long-Term Renal and Cardiovascular Outcomes in US Veterans.” CJASN. Published online Dec 5, 2013.