Rapid Hypothermia After Heart Attack Shows Positive Effects
April 21, 2008 - Rapid cooling prior to reperfusion significantly reduced overall myocardial infarct size and protected the heart from other injury, according to a study by Cardium Therapeutics and its operating unit InnerCool Therapies, reported a study published online by BioMed Central (BMC) Cardiovascular Disorders (2008, 8:7, April 10, 2008).
The study, conducted by a team of interventional cardiologists at the Lund University Hospital, Sweden, evaluated the effect of early and rapid cooling induced by a combination of cold saline infusion along with InnerCool's endovascular Celsius Control System, before or immediately after reperfusion when coronary blood flow was restored in the heart in a porcine heart attack model. Results from this study demonstrated that rapid cooling (to <35 degrees Celsius) prior to reperfusion significantly reduced overall myocardial infarct size and protected the heart from other injury.
The study was designed to further investigate the therapeutic potential of early and rapid hypothermia to preserve heart tissue following a heart attack. Using a closed-chest porcine heart attack model in which the coronary artery supplying the heart muscle was initially blocked and later reopened, as occurs in patients after a heart attack or acute myocardial infarction (MI), the investigators evaluated the effects of rapid cooling to a target temperature of 33 degrees Celsius to 35 degrees Celsius on myocardial infarct size as assessed by cardiac magnetic resonance imaging (MRI). Rapid hypothermia, induced by the infusion of one liter of cold saline in combination with InnerCool's endovascular catheter-based temperature modulation system, initiated either prior to or after restoration of blood flow, was compared to a normal core body temperature of 38 degrees Celsius throughout the procedure.
The data showed that early rapid cooling substantially reduced the damage to heart muscle that typically follows a heart attack and reperfusion. In particular, cooling prior to reperfusion reduced overall myocardial infarct size by 43 percent compared to hypothermia after reperfusion (p<0.05), and by 39 percent compared to normothermia (p<0.05). In addition, hypothermia initiated either before or after reperfusion also significantly reduced impairment of blood flow in the coronary microvasculature (microvascular obstruction) that may be associated with reperfusion injury.
The results from this study are consistent with clinical findings from the Intravascular Cooling Adjunctive to Percutaneous Coronary Intervention (ICE-IT) study, a 228 patient study sponsored by InnerCool, in which infarct size was reduced (43 percent in anterior MIs and 39 percent in inferior MIs) in patients who were cooled rapidly to <35 degrees Celsius prior to reperfusion with an endovascular temperature modulation system as an adjunct to angioplasty and stent procedures. The current study further confirms this correlation between rapid cooling to a body core temperature of less than 35 degrees Celsius prior to reperfusion and reduction in infarct size.
"Preclinical and preliminary clinical data suggest that rapid patient cooling using intravenous cold saline in combination with endovascular hypothermia can be initiated without causing delay of reperfusion therapy and may have the potential to enable interventional cardiologists to dramatically reduce heart tissue damage following a heart attack," stated David Erlinge, M.D., Ph.D. of the Lund University cardiology Center.
Based on these findings, InnerCool is sponsoring a study on the use of early and rapid cooling of patients with myocardial infarction (MI or heart attack), which is being co-sponsored and conducted by the interventional cardiology center at Lund University Hospital, Sweden. The ongoing clinical study, called RAPID MI-ICE (Rapid Intravascular Cooling in Myocardial Infarction as Adjunctive to Percutaneous Coronary Intervention), is expected to enroll approximately 20 patients who present within six hours of their heart attack and require angioplasty and stent procedures in order to restore blood flow to the heart. Eligible patients will be randomized to one of two treatment protocols, and the effects on heart tissue damage will be compared.
Patients randomized to the cooling arm (hypothermia) will be infused with 1 liter of iced saline in addition to endovascular cooling with the InnerCool Accutrolcatheter, which contains an integrated temperature sensor that measures the patient's core body temperature. Patients assigned to the normothermia arm will receive routine standard of care without induced hypothermia. The trial will employ cardiac MRI to provide an assessment of the damage to the heart, as measured by infarct size, within days of the heart attack.
For more information: www.cardiumthx.com, www.innercool.com and www.t-r-co.com