Circadian rhythms of heart rate and blood pressure after heart transplantation.

Blood pressure and heart rate were recorded over 24-hour periods on 39 occasions in 20 subjects 5 to 72 weeks after heart transplantation. All patients were receiving cyclosporine, azathioprine, and prednisolone. In 38 of the 39 records the mean nighttime heart rate was lower than the mean daytime rate, with a peak difference of 20.1 +/- 1.8 beats/min. Blood pressure responses were, however, of two patterns. In 15 of the 39 recordings (approximately 50% of patients) the mean nighttime systolic pressure was higher than the mean daytime systolic pressure; in the remainder the converse was observed. The pattern was generally consistent on repeated recordings from the same patient and was not related to time since transplantation, renal function, or other therapy. Echocardiographic/Doppler studies were available at the time of 31 of these recordings. No differences in left ventricular diameters, systolic function, or transmitral filling patterns were present between patients whose blood pressure was higher or lower at night. Left ventricular posterior wall thickness and the ratio between wall thickness and ventricular diameter at end diastole were greater in the group showing nighttime pressure falls. Blood pressure responses after heart transplantation show the presence of nighttime "dippers" and "nondippers." At least early after transplantation, however, nondipper status is not preferentially associated with the development of left ventricular hypertrophy. The mechanisms accounting for the different circadian blood pressure responses in heart transplant recipients are not known.