Late-breaking results of clinical trial on therapeutic endovascular cooling reported at TCT 2008

Late-breaking results from the COOL RCN (COOLing to Prevent Radio Contrast Nephropathy in Patients Undergoing Diagnostic or Interventional Catheterization) Trial were presented during the 20th annual Transcatheter Cardiovascular Therapeutics (TCT) scientific symposium, sponsored by the Cardiovascular Research Foundation (CRF). The prospective, randomized, multicenter clinical study was designed to evaluate the safety and effectiveness of catheter-based endovascular cooling for preventing acute kidney failure in high risk patients – often a serious side effect of radiographic contrast agents which are administered to all patients undergoing diagnostic or interventional catheterization procedures. Acute kidney failure following exposure to intravascular contrast agents is known as radiocontrast nephropathy (RCN).

Principal Investigator Gregg W. Stone, M.D., CRF Chairman, Professor of Medicine and the Director of Research and Education at the Center for Interventional Vascular Therapy at NewYork-Presbyterian Hospital/Columbia University Medical Center, presented the findings of the study.

Patients with pre-existing renal insufficiency, heart disease, or diabetes are at particularly high risk of developing RCN after cardiac catheterization. Mild hypothermia to protect the kidneys of high risk patients while they are undergoing cardiac catheterization is one potential therapy.

According to Dr. Stone, "This is a novel approach to preventing a common but serious side effect of radiographic contrast agents. The body is cooled from the inside out by approximately 7 degrees Fahrenheit."

The COOL RCN system enables the rapid induction of hypothermia in a conscious or unconscious patient by use of a venous heat exchange catheter. It provides very rapid, precise cooling, maintenance, and re-warming of the patient's core body temperature. A catheter is threaded into the femoral vein and positioned in the inferior vena cava. As cool sterile saline is circulated within the catheter, blood flowing past the catheter is cooled and, in turn, reduces body temperature. To re-warm the patient, the sterile saline within the catheter is simply warmed.

In the COOL RCN trial, 136 patients were recruited between March 2006 and August 2007, and researchers were able to evaluate 128 patients. In the pilot study, 32 patients (median age 71, 50% diabetes) were hydrated and cooled to 33-34○C less than 90 minutes prior to and for 3 hours after contrast was administered. Cooling had to be achieved before the first administration of contrast agent. The target core temperature in patients was 33○C; no contrast was administered before 34○C.

The observed rate of RCN in the control arm - 18.6% - was lower than had been anticipated - 35%. This fact, coupled with the enrollment of only 136 of 400 planned patients (34%) resulted in a wide point estimate for the treatment effect of systemic hypothermia.

Dr. Stone noted the trial was abbreviated due to a lack of funding. However, he concluded that based on the limited number of participants, "in patients at high risk for RCN undergoing invasive cardiology procedures, cooling may be safely achieved and is well-tolerated, but these results do not point to a significant reduction in RCN."

Source: Cardiovascular Research Foundation