The fourth sound of Korotkoff in pregnancy: a myth

To determine the detection rate and the reproducibility of the first (K1), the fourth (K4) and the fifth (K5) phases of the Korotkoff sounds in pregnant women. In 77 pregnant women receiving antenatal care in a tertiary referral centre, two observers took 231 simultaneous blood pressure measurements with a shared mercury sphygmomanometer and a multi-aural stethoscope. Detection rates, percentages of observer agreement within 5 mmHg and kappa values were calculated for K1, K4 and K5. Both observers were able to detect K1, K4 and K5 in 98, 24 and 98% of all 231 measurements, respectively. In 46% of measurements, and in 23% of women, neither observer was able to detect K4. The observers agreed within 5 mmHg in 98 (kappa = 0.99), 69 (kappa = 0.42), and 96% (kappa = 0.99) of measurements for K1, K4 and K5, respectively. K4 cannot be detected and reproduced accurately in a significant proportion of pregnant women, and therefore should be abandoned as diastolic endpoint in pregnancy