We read with interest the study by Kyle et al. (October 1993) that found both an increased blood pressure and heart rate in women with later pre-eclampsia already at 18 weeks gestation. We have investigated prospectively the association of heart rate and pregnancy outcome by monitoring with an ambulatory electrocardiogram for 24 h on a two-channel Holter recorder (series 8500, Marquette Electronics Inc, Wisconsin, USA) in 70 healthy women with singleton pregnancies at 24 weeks of gestation (range 21 to 29). Forty-six women (66%) were nulliparous. All had normal blood pressures during the first pregnancy trimester.

Four patients developed pregnancy-induced hypertension (PIH) with a blood pressure exceeding 140/90 mmHg on two separate occasions after the 20th week of gestation and new-onset proteinuria (0.3 g/l or more, measured semiquantitatively). In addition, one nullipara evolved nonproteinuric PIH. None of the women met the criteria of PIH at the time of the Holler recording.

In contrast with the resulls by Kyle et al., our data did not show an increased heart rate in women with later PIH. Logistic regression analysis showed that both the average heart rate (85 bpm (SD 5) vs 86 bpm (SD 6), P= 0.76) and the minimum heart rate (56 bpm (SD 4) vs 55 bpm (SD 8), P= 0.75) were similar in both groups. The maximum heart rate was significantly lower in the women with incipient PIH (145 bpm (SD 11) compared with the normotensive controls (154 bpm (SD 9), P= 0.04, OR 1.11, 95% CL 0.99–1.24). However, the maximum heart rate is hardly useful in screening for PIH, as it varies greatly depending on daily activities. In contrast with the study by Kyle et al., we found that the incidence of PIH was highest in the lowest heart rate quartile (< 82 bpm) (two women compared to one in the remaining quartiles).

The discrepancy of our results with the findings by Kyle et al. may depend on different methodology. Kyle et al. used an ambulatory blood pressure monitor that measured the heart rate intermittently and synchronously with the blood pressure. An enhanced haemodynamic reactivity to blood pressure measurement in women with incipient PIH could account for the different results.


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