MI-Shock Proposal Is Cold Comfort: Hypothermia Might Boost Survival

February 06, 2012

February 6, 2012 (Boston, Massachusetts) — Therapeutic hypothermia can help preserve the brain during cardiac arrest, so maybe it could protect organs throughout the body in other conditions that threaten their blood supply--such as cardiogenic shock.

That's the premise of a viewpoint published online today in the Journal of the American College of Cardiology, one that surveys the available, mostly preclinical evidence for just such a systemic protective effect from induced hypothermia [1]. The strategy "merits further study as a potential novel treatment for post-MI cardiogenic shock and could represent the next measurable advance in survival after MI."

Cooling the whole body should have effects on multiple pathways and multiple organs that might be affected by the shock state.

Cardiogenic shock in the MI setting was usually fatal until the advent of acute reperfusion therapy with balloon angioplasty, but even today with modern PCI and intra-aortic balloon pumping, mortality is about 50%, note the viewpoint's authors, led by Dr Brian M Stegman (Duke University Medical Center, Durham, NC). They describe a range of pathophysiologic processes involved in cardiogenic shock that could potentially be lessened or blocked by therapeutic hypothermia, possibly improving outcomes. They include ischemia and reperfusion injury, systemic inflammation, and vascular dysfunction.

The most relevant goal, they write, would be to "improve cardiac function and hemodynamics and reduce end-organ damage from prolonged hypoperfusion."

Shock is a systemwide condition, and induced hypothermia is typically a systemic treatment, observed coauthor Dr L Kristin Newby (Duke University Medical Center) for heartwire . "Cooling the whole body should have effects on multiple pathways and multiple organs that might be affected by the shock state and help temporize things until you can stabilize the patient, warm them back up, and avoid that period of injury."

The published clinical experience with therapeutic hypothermia in post-MI or post–cardiac-surgery shock is mostly limited to case reports and small series, Newby explained. There is also a small clinical-trial experience of the intervention in patients getting PCI for acute MI, which suggests it may help reduce infarct size in those with anterior infarctions.

Before there could be a more substantive randomized trial of whether hypothermia improves survival in cardiogenic shock, Newby said, some questions need answering, and her center has put together protocols for the necessary early studies.

"We already know a lot about the safety issues from [experience with] cooling in cardiac arrest," she said. "What we can't say we know for sure is [whether] the same temperature range and duration of cooling used in cardiac arrest will be either beneficial or necessary in cardiogenic shock. So there is some preliminary work that would need to be done before we could undertake the mortality trial."

Stegman et al report that they have no relevant disclosures.


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