- Email: [email protected]
Reply to Drs. Dooley and Hobart
Correspondence
Volume 131
917
~umber~
0BSTET. GYNECOL. 130: 165, 1978) Dr. Richard H. Paul and colleagues described fetal bradycardia occurring after the onset of a maternal eclamptic seizure. They observed fetal bradycardia of 30 seconds to nine minutes in duration associated with increased uterine activity. Tachycardia and bradycardia are described as baseline fet.1l heart rate (FHR) changes. As originally defined bv Hon, baseline FHR is "the FHR pattern present (a) when the patient is not in labor or (b) in the interval between periodic FHR change." 1 Furthermore. "a shift in baseline FHR is recorded if the new level persists for at least ten minutes." 1 Therefore, by definition the FHR change described by Dr. Paul and associates in their paper is not bradycardia. One is tempted to call it "prolonged deceleration," but it is not a periodic change by strict definition: the initial fall in heart rate is associated with a uterine contraction, but there is no subsequent periodicity. The importance of distinguishing a periodic change from a baseline change relates to the mechanism of fetal stress. A periodic change is a short-term FHR response. implying a specific physiologic stress, whereas a baseline change probably relates best to more longterm influences. The mechanism of the FHR change during a maternal eclamptic seizure is not clear, but uterine tachysystole and apparent hypertonus with an associated decrease in intervillous perfusion imply a specific physiologic stress. This FHR pattern fits no given definition, but we suggest that "prolonged deceleration'' is a more appropriate term than "bradycardia.·· In this era of embryonic understanding of FHR con-
trol, it is of utmost importance that \H' JdiH'n· to ;·stablished definitions in order to promote dicctive cotnmunication between investigators and clinicians. It h:ts become increasingly clear that not all FHR observations fit established definitions. As student~ in 1he field. we suggest a re-evaluation of terminologv in mdn to keep pace with advances in understanding. Sha11.•11 L /looli'l ..\1./J. John,\[. Jfohflrt. ,\/.lJ.
Departmmt of Maternal-Fetal /Hedu·i 111· Northwestern Uni·eersity Schoof nf Al1·dtrntr 303 E. Chicago Avenue Chicago, Illinois 60611
REFERENCE l. Hon, E. H.: An Introduction to Fetal Ht·art Rate Monilor· ing, New Haven. Connecticut, 197.1. pp. :li :md 40.
Reply to Drs. Dooley and Hobart To the Editors: I appreciate Drs. Dooley and Hobart's concern over FHR terminology. I agree with the comment, "This FHR pattern fits no given definition.. ."and also find the term "prolonged deceleration'' totallv acceptable. As they say. both are subject to question. Perhaps I used this term since we often have labeled similar FHR findings associated with paracervical block as "bradycardia . " Richrml H l'11ul..'H.D. Women's Hospital. 5K-22 1240 North Mission Road Los Angeles, California 90033
Volume 131
917
~umber~
0BSTET. GYNECOL. 130: 165, 1978) Dr. Richard H. Paul and colleagues described fetal bradycardia occurring after the onset of a maternal eclamptic seizure. They observed fetal bradycardia of 30 seconds to nine minutes in duration associated with increased uterine activity. Tachycardia and bradycardia are described as baseline fet.1l heart rate (FHR) changes. As originally defined bv Hon, baseline FHR is "the FHR pattern present (a) when the patient is not in labor or (b) in the interval between periodic FHR change." 1 Furthermore. "a shift in baseline FHR is recorded if the new level persists for at least ten minutes." 1 Therefore, by definition the FHR change described by Dr. Paul and associates in their paper is not bradycardia. One is tempted to call it "prolonged deceleration," but it is not a periodic change by strict definition: the initial fall in heart rate is associated with a uterine contraction, but there is no subsequent periodicity. The importance of distinguishing a periodic change from a baseline change relates to the mechanism of fetal stress. A periodic change is a short-term FHR response. implying a specific physiologic stress, whereas a baseline change probably relates best to more longterm influences. The mechanism of the FHR change during a maternal eclamptic seizure is not clear, but uterine tachysystole and apparent hypertonus with an associated decrease in intervillous perfusion imply a specific physiologic stress. This FHR pattern fits no given definition, but we suggest that "prolonged deceleration'' is a more appropriate term than "bradycardia.·· In this era of embryonic understanding of FHR con-
trol, it is of utmost importance that \H' JdiH'n· to ;·stablished definitions in order to promote dicctive cotnmunication between investigators and clinicians. It h:ts become increasingly clear that not all FHR observations fit established definitions. As student~ in 1he field. we suggest a re-evaluation of terminologv in mdn to keep pace with advances in understanding. Sha11.•11 L /looli'l ..\1./J. John,\[. Jfohflrt. ,\/.lJ.
Departmmt of Maternal-Fetal /Hedu·i 111· Northwestern Uni·eersity Schoof nf Al1·dtrntr 303 E. Chicago Avenue Chicago, Illinois 60611
REFERENCE l. Hon, E. H.: An Introduction to Fetal Ht·art Rate Monilor· ing, New Haven. Connecticut, 197.1. pp. :li :md 40.
Reply to Drs. Dooley and Hobart To the Editors: I appreciate Drs. Dooley and Hobart's concern over FHR terminology. I agree with the comment, "This FHR pattern fits no given definition.. ."and also find the term "prolonged deceleration'' totallv acceptable. As they say. both are subject to question. Perhaps I used this term since we often have labeled similar FHR findings associated with paracervical block as "bradycardia . " Richrml H l'11ul..'H.D. Women's Hospital. 5K-22 1240 North Mission Road Los Angeles, California 90033