Correspondence

The Brockenbrough-Braunwald-Morrow Sign

N Engl J Med 1994; 331:1589-1590December 8, 1994

Article

To the Editor:

With regard to the clinical image depicting the “Brockenbrough-Braunwald sign” (July 28 issue),1 the authors of the 1961 article that initially described the diminished pulse pressure in the post-extrasystolic beat were Brockenbrough, Braunwald, and Morrow.2 The late Andrew G. Morrow was a prolific investigator of hypertrophic cardiomyopathy and deserves equal recognition. The criterion for a positive post-extrasystolic response was later modified by the authors to include instances in which the pulse pressure fails to increase.3 It was also later found that this sign is not unique to hypertrophic cardiomyopathy but has frequently been observed in discrete forms of aortic stenosis.4 Figure 1Figure 1Brockenbrough-Braunwald-Morrow Sign in Aortic Stenosis. depicts this response in patients with valvular and discrete subvalvular aortic stenosis.

It has also been found that the ventricle in hypertrophic cardiomyopathy actually empties more rapidly and completely in situations in which the gradient is augmented,5,6 including post-extrasystolic and inotropic stimulation. These observations belie the explanation offered for the diminished pulse pressure -- namely, a “reduced stroke volume caused by increased dynamic obstruction.”

Since it is unlikely that the severity of obstruction in aortic stenosis increases during the post-extrasystolic beat, other mechanisms should be considered to explain this fall in pulse pressure. The prolonged diastolic aortic runoff time decreases the aortic impedance, and an increase in mitral regurgitation driven by the higher left ventricular pressure may lower the forward stroke volume. Either or both of these explanations may also apply to hypertrophic cardiomyopathy.

John Michael Criley, M.D.
Steven L. Goldberg, M.D.
William J. French, M.D.
Harbor-UCLA Medical Center, Torrance, CA 90502

6 References

1. 1

   Pollock SG. Pressure tracings in obstructive cardiomyopathy. N Engl J Med 1994;331:238-238
   Full Text | Web of Science | Medline

2. 2

   Brockenbrough EC, Braunwald E, Morrow AG. A hemodynamic technic for the detection of hypertrophic subaortic stenosis. Circulation 1961;23:189-194
   Web of Science

3. 3

   Braunwald E, Lambrew CT, Morrow AG, Pierce GE, Rockoff SD, Ross J Jr. Idiopathic hypertrophic subaortic stenosis. Circulation 1964;30:Suppl IV:IV-1
   

4. 4

   Kramer DS, French WJ, Criley JM. The postextrasystolic murmur response to gradient in hypertrophic cardiomyopathy. Ann Intern Med 1986;104:772-776
   Web of Science | Medline

5. 5

   Wilson WS, Criley JM, Ross RS. Dynamics of left ventricular emptying in hypertrophic subaortic stenosis: a cineangiographic and hemodynamic study. Am Heart J 1967;73:4-16
   CrossRef | Web of Science | Medline

6. 6

   Siegel RJ, Criley JM. Comparison of ventricular emptying with and without a pressure gradient in patients with hypertrophic cardiomyopathy. Br Heart J 1985;53:283-291
   CrossRef | Web of Science | Medline

Author/Editor Response

Dr. Pollock replies:

To the Editor: Criley et al. correctly point out that Dr. Morrow contributed to the first description of the post-extrasystolic fall in pulse pressure seen in idiopathic hypertrophic subaortic stenosis (as the disorder was then called). They also question my explanation of the mechanism of this hemodynamic finding.

I used the term “Brockenbrough-Braunwald sign,” excluding Dr. Morrow's name, because it is the name commonly used for this sign.1 Although it is technically incorrect to omit one of the investigators' names, such terms are often abbreviated for convenience. For instance, the preoperative assessment is guided by the “Goldman class,” a term that would be cumbersome if it included the names of all 13 authors.2

I explained the post-extrasystolic fall in blood pressure as a reduction in stroke volume due to an increase in dynamic obstruction, which is the usual explanation for this finding but may, like the sign's name, be incorrect.1,3 Criley et al. argue this point by presenting a pressure tracing from a patient with fixed valvular stenosis. The tracing purports to show the Brockenbrough-Braunwald-Morrow sign. The pulse pressure, however, is reduced not just for one beat after the premature ventricular contraction but for four beats. Furthermore, the pulse pressure is reduced even before the premature ventricular contraction. This is not an example of the Brockenbrough-Braunwald-Morrow sign. Although the tracing does not rule out a role for dynamic obstruction in causing the Brockenbrough-Braunwald-Morrow sign, the suggestion that enhanced mitral regurgitation or arterial compliance contributes to the physiologic process is intriguing. The second tracing, from a patient with discrete subvalvular aortic stenosis, supports this idea.

Stewart G. Pollock, M.D.
Harrisonburg Medical Associates, Harrisonburg, VA 22801-7500

3 References

1. 1

   Grossman W. Profiles in dilated (congestive) and hypertrophic cardiomyopathies. In: Grossman W, ed. Cardiac catheterization and angiography. Philadelphia: Lea & Febiger, 1986:420-1.
   

2. 2

   Goldman L, Caldera DL, Nussbaum SR, et al. Multifactorial index of cardiac risk in noncardiac surgical procedures. N Engl J Med 1977;297:845-850
   Full Text | Web of Science | Medline

3. 3

   Wynne J, Braunwald E. The cardiomyopathies and myocarditides. In: Braunwald E, ed. Heart disease: a textbook of cardiovascular medicine. 3rd ed. Vol. 2. Philadelphia: W.B. Saunders, 1988:1428.