Correspondence

“Hibernating Myocardium”: A Confusing Term?

N Engl J Med 1999; 341:213-214July 15, 1999

Article

To the Editor:

The process of hibernation, the “winter sleep of warm-blooded animals,” is a physiologic mechanism of self-protection that remains little understood. Webster's New World Dictionary defines hibernate as “to pass the winter in a torpid state.”1 The Oxford English Dictionary describes hibernation as “the action of wintering, or passing the winter” or “the dormant condition into which many animals and plants pass when the temperature falls below certain limits.”2 It also describes the figurative use of the word as “any condition or period of dormancy or suspended activity.” These definitions refer to normal states.

The initiation of hibernation relates to the ambient temperature and the availability of a food supply and is associated with substantial decreases in oxygen consumption and body metabolism. The heart and respiratory rates decrease. Although the body temperatures of hibernating animals sometimes drop to levels close to freezing, the animals rewarm without evidence of organ damage due to cold. Thus, the physiologic process of hibernation is markedly different from that of hypothermia, in which organ damage is sustained, serious arrhythmias occur, and death may be a consequence of excessive lowering of body temperature. So although hibernation remains a mysterious physiologic process, it is physiologic and is in no sense pathologic.3,4

“Myocardial hibernation” is a misnomer because it refers to a state of myocardial metabolic dormancy that is initiated by a pathologic process — namely, ischemia. Indeed, it is an inapplicable term because there is evidence that the so-called hibernating myocardium is undergoing slow, though perhaps patchy, death. In hibernating animals there is no evidence of muscle death. The use of a term like “hibernating myocardium” also suggests that when the hibernation ends, organ function will return to normal. Clearly, on the basis of clinical experience, this is of questionable validity.

What can we do about a term like “hibernating myocardium,” which has caught on in the medical and scientific vocabulary? Our use of correct language is important in the way we formulate our thinking. Medicine has lived through such problems in the past, and scientists, research workers, and physicians should begin to use terminology that is accurate and leads to better insight into disease processes. For example, we learned to abandon “IHSS” (idiopathic hypertrophic subaortic stenosis) as a catchall phrase in studies of hypertrophic cardiomyopathy when we realized that this popular term was often inaccurate and even misleading about the myocardial pathologic features of this disease.

A much better term than “myocardial hibernation,” and one that does not violate correct pathological understanding, would be “myocardial stunning with prolonged dormancy.” Such a term would be physiologically and pathologically correct and would describe a pathologic process that produces a myocardial dormant state. There would be no inaccurate suggestion that with time or with revascularization the organ would return to a normal state.

When looking up “myocardial hibernation” in the Index Medicus, readers are directed to “see `myocardial stunning.'”5 The editors have it right, and their advice is eminently appropriate.

Albert J. Miller, M.D.
Northwestern University Medical School, Chicago, IL 60611

5 References

1. 1

   Webster's New World Dictionary. New York: Simon and Schuster, 1979.
   

2. 2

   Oxford English dictionary. 2nd ed. Oxford, England: Oxford University Press, 1989.
   

3. 3

   Lyman CP, Willis JS, Malan A, Wang LCH. Hibernation and torpor in mammals and birds. New York: Academic Press, 1982.
   

4. 4

   Kayser C. The physiology of natural hibernation. Oxford, England: Pergamon Press, 1961.
   

5. 5

   Index medicus. Washington, D.C.: Government Printing Office, 1997.