24 HOUR VARIATION IN PLASMA ATRIAL-NATRIURETIC-FACTOR DURING VVI AND DDD PACING

Objective-To investigate whether plasma atrial natriuretic factor (ANF ) follows a pattern of circadian variation similar to that of other ho rmones in patients paced under VVI and DDD pacing modes and to determi ne if the known effect of pacing mode on ANF secretion is maintained t hroughout the 24 hour period. Patients and Design-20 patients were stu died. They had complete atrioventricular block and had been paced for 17 (SD 3.5) months with a dual chamber multiprogrammable pacemaker. Th ey were divided into two groups according to the duration of pacing in either VVI or DDD mode before the measurements: group A, n = 11 (8 me n, 3 women, aged 65 (7) years), each paced far 24 h under each of VVI and DDD modes in random order; group B, n = 9 (7 men, 2 women, aged 63 (8) years), each paced for 60 d under each pacing mode before the mea surements. Blood samples were taken and ANF concentrations measured ev ery 4 h over a 24 h period,starting at 09.00. Measurements were also m ade of plasma cortisol, which has a known circadian pattern, so that t he 24 h curve could be compared with that of ANF. Results-In contrast to cortisol, ANF values indicated a pulsatile pattern of secretion thr oughout the 24 h period, with no clear circadian variation. In group B , ANF concentrations were significantly higher during VVI than during DDD pacing throughout the 24 h period, whereas in group A this differe nce was statistically significant only at certain times of day. Conclu sions-ANF does not show the circadian pattern of variation shown by co rtisol and other hormones. Dual chamber pacing contributes to an impro vement not only in cardiac haemodynamics but also in the neuroendocrin e system, especially in the long term.