ABNORMAL DIURNAL-VARIATION OF BLOOD-PRESSURE, CARDIAC-OUTPUT, AND VASCULAR-RESISTANCE IN CARDIAC TRANSPLANT RECIPIENTS

Background An attenuated or absent nocturnal decline in blood pressure has repeatedly been documented in cardiac transplant recipients. The present study was aimed at investigating the hemodynamic mechanism und erlying this abnormality. Methods and Results In 23 cardiac transplant recipients (11 to 36 months after transplantation) and in 23 control subjects matched for age and 24-hour mean arterial pressure, invasive 24-hour ambulatory blood pressure was measured by means of the Oxford technique. Beat-to-beat relative values of stroke volume were determin ed by means of a pulse-contour method, and relative changes of cardiac output (stroke volumeXheart rate) and total peripheral vascular resis tance (blood pressure/cardiac output) over the 24-hour period were cal culated. The nocturnal decline in blood pressure was 20+/-8% (mean+/-S D) in control subjects but only 5+/-9% (P<.001) in cardiac transplant recipients. In control subjects, the nocturnal decline in blood pressu re was associated with a nocturnal fall in cardiac output of 24+/-13%, whereas vascular resistance compared with daytime value did not chang e. The small nocturnal decline in blood pressure in cardiac transplant recipients was associated with an attenuated nocturnal fall in cardia c output of 14+/-12% (P<.05 versus control subjects). In addition, vas cular resistance compared with daytime value was increased by 9+/-9% ( P<.05) during the night. Both in cardiac transplant recipients and in control subjects, the nocturnal changes in blood pressure were correla ted with the nocturnal changes in cardiac output but not with the noct urnal changes in total peripheral vascular resistance. Conclusions Thi s study confirms the attenuated nocturnal fall in blood pressure in ca rdiac transplant recipients. Hemodynamically, this attenuated blood pr essure decline is characterized by a reduced nocturnal fall in cardiac output, and it is associated with a nocturnal increase in vascular re sistance.