CMAJ/JAMC Letters
Correspondance

 

Which Korotkoff sound?

CMAJ 1998;158:297
Re: "Report of the Canadian Hypertension Society Consensus Conference: 1. Definitions, evaluation and classification of hypertensive disorders in pregnancy" (CMAJ 1997;157[6]:715-25 [full text / résumé])

In response to: J.G. Ray

Dr. Ray has touched on one of the more controversial issues in our report: Which of the 2 Korotkoff sounds, phase IV or phase V, should be used to define diastole in pregnancy?

During our consensus deliberations, we looked for publications that correlated the Korotkoff sounds to a gold standard of arterial intravascular diastolic pressure measurements. Unfortunately, our search yielded conflicting results,1-4 some data showing that the Korotkoff phase IV sound was a more reliable reflection of the true intravascular diastolic pressure as determined by invasive techniques, and other data favouring the phase V sound.

There is little doubt that the Korotkoff phase IV sound is subject to greater interobserver and intraobserver variability than the phase V sound,5 but the latter may occasionally be falsely low.6 Although diastolic pressure measurements as determined by the phase IV sound may be 5 to 8 mm higher than those determined by the phase V sound,5 the difference is reduced in hypertensive states of pregnancy.7

Faced with a lack of reliable data to support adopting either the phase IV or the phase V sound, the members of the consensus group felt that the phase IV sound, by virtue of its being slightly higher than the phase V sound, might offer a wider margin of safety in initiating surveillance for the possible complications of hypertensive disorders of pregnancy. Most societies and interest groups, as well as many leading authorities in the study of hypertension, have recommended using the phase IV sound to determine diastole in pregnancy.

Recommending that clinicians record both sounds is not an original idea. The American National High Blood Pressure Education Program Working Group on High Blood Pressure in Pregnancy8 recommended that both sounds be recorded.

Canadian research in this area is urgently needed. Our recommendations will be revisited in the future, especially when more evidence becomes available.

Michael E. Helewa, MD
Head of Clinical Obstetrics
Associate Professor
University of Manitoba
Winnipeg, Man.

References

  1. Wichman K, Ryden G, Wichman M. The influence of different positions and Korotkoff sounds on the blood pressure measurements in pregnancy. Acta Obstet Gynecol Scand Suppl 1984;118:25-8.
  2. Villar J, Repke J, Markush L, Calvert W, Rhoads G. The measuring of blood pressure during pregnancy. Am J Obstet Gynecol 1989;161:1019-24.
  3. Johenning AR, Barron WM. Indirect blood pressure measurements in pregnancy: Korotkoff phase 4 versus phase 5. Am J Obstet Gynecol 1992;167:577-80.
  4. Brown MA, Reiter L, Smith B, Buddle ML, Morris R, Whitworth JA. Measuring blood pressure in pregnant women: a comparison of direct and indirect methods. Am J Obstet Gynecol 1994;171:661-7.
  5. ;Shennan A, Gupta M, Halligan A, Taylor D, DeSwiet M. Lack of reproducibility in pregnancy of Korotkoff phase IV as measured by mercury sphygmomanometry. Lancet 1996;347:139-42.
  6. MacGillivray I, Rose GA, Rowe D. Blood pressure survey in pregnancy. Clin Sci 1969;37:395-407.
  7. Gallery EDM, Brown MA, Ross MR, et al. Accuracy of indirect sphygmomanometry in determination of arterial pressure during pregnancy. In: Proceedings of the International Society for the Study of Hypertension in Pregnancy IXth Congress, Sydney, Australia, Mar 15-18, 1994. Monticello (NY): Dekker; 1994. p. 74.
  8. National High Blood Pressure Education Program Working Group Report on high blood pressure in pregnancy. Am J Obstet Gynecol 1990;163:1689-712.
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| CMAJ February 10, 1998 (vol 158, no 3) / JAMC le 10 février 1998 (vol 158, no 3) |