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Changes in rate-pressure product associated with pregnancy
Claudio V Schenone1, M Ashley Cain1, Aldo L Schenone2
1Department of Obstetrics and Gynecology, University of South Florida Morsani College of Medicine, Tampa, FL (Drs C Schenone, Cain, Louis, and Crousillat).
American Journal of Obstetrics & Gynecology MFM
|March 7, 2024
Summary
Pregnancy significantly increases myocardial oxygen demand, as measured by the rate-pressure product (heart rate x systolic blood pressure), peaking in the third trimester and during labor. Lower prepregnancy body mass index is linked to a sharper increase in this cardiovascular marker.
Area of Science:
- Cardiovascular Physiology
- Reproductive Medicine
- Obstetrics
Background:
- The rate-pressure product (RPP), calculated as heart rate multiplied by systolic blood pressure, serves as a noninvasive indicator of myocardial oxygen consumption in nonpregnant individuals.
- Pregnancy is a physiological stress on the cardiovascular system, yet its precise impact on myocardial oxygen demand, assessed via RPP, remains incompletely understood.
- Existing evidence on how pregnancy influences myocardial oxygen demand, using RPP as a surrogate, is limited.
Purpose of the Study:
- To characterize the temporal changes in the rate-pressure product throughout pregnancy trimesters, labor and delivery, and the postpartum period in low-risk pregnancies.
- To quantify the magnitude of these changes relative to preconception levels.
- To explore the influence of prepregnancy body mass index, age, and neuraxial anesthesia on RPP variations during pregnancy and delivery.
Main Methods:
- A retrospective cohort study involving 316 uncomplicated pregnancies delivered vaginally at term.
- Rate-pressure product (RPP) values were collected preconception, during each trimester of pregnancy, at multiple stages of labor and delivery, and during a postpartum visit.
- Statistical analysis, including mixed-linear modeling, was used to assess changes in RPP over time and the impact of demographic and anesthetic factors.
Main Results:
- A significant increase in mean RPP was observed from preconception levels, beginning in the third trimester and continuing through labor and delivery.
- The mean RPP showed peak increases of 12% in the third trimester and 38% during labor and delivery compared to preconception values.
- Lower prepregnancy body mass index was significantly correlated with greater increases in RPP (estimate = -0.308, P=.008), while prepregnancy age and neuraxial anesthesia status did not significantly influence RPP changes.
Conclusions:
- This study confirms a transient but significant elevation in the rate-pressure product, reflecting increased myocardial oxygen demand, during uncomplicated term pregnancies.
- Pregnant individuals with a lower prepregnancy body mass index exhibit a more pronounced rise in RPP.
- Neuraxial anesthesia during labor and delivery does not appear to significantly alter the pattern of RPP changes compared to those without.
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