The Effect of Chronic Nifedipine Therapy on Ambulatory Intra-Arterial Blood Pressure and the Baroreflex Response

Abstract

Medical Research Societyi S o l a t e d i n a q u i e t rooin; a d o c t o r [ O J K I then e n t e r e d t h e room and me83sured blood p r e s s u r e c o n v e n t i o n a l l y and a t t h e same time i n t h e o t h e r arm.T h i s r a i s e d Bosoinat blood p r e s s u r e i n a l l h y p e r t e n s i v e p a t i e n t s , ~y an average of 18/16 [ s y s t o l i c / d i a s t o l i c ) , 5/6 and 1/3 mHg on t h e 1 s t . 3rd and 5 t h days of admission r e s p e c t i v e l y .S i g n i f i c a n t and s i m i l a r d e c r e a s e s occured i n mean ward blood p r e s s u r e [17/13 from 1 s t t o 5th day) and i n t h e alarm r e a c t i o n ( 1 7 / 1 2 from 1 s t t o 5th d a y ] .There was i n a d d i t i o n i n i n d i v i d u a l s u b j e c t s a s i g n i f i c a n t c o r r e l a t i o n between t h e d e c l i n e i n ward blood p r e s s u r e and t h e r e d u c t i o n i n t h e alarm r e a c t i o n [ r = 0.927, p <0.01 f o r s y s t o l i c ) .I n c o n t r o l s u b j e c t s t h e alarm r e a c t i o n , t h e d e c r e a s e i n t h e alarm r e a c t i o n and t h e f a l l i n ward blood p r e s s u r e were s i g n i f i c a n t l y less than i n h y p e r t e n s i v e s .These r e s u l t s suggest t h a t a t t e n u a t i o n of t h e alarm r e a c t i o n i s l a r g e l y r e s p o n s i b l e f o r t h e f a l l i n blood p r e s s u r e which o c c u r s when p a t i e n t s w i t h u n t r e a t e d hypertension a r e a d m i t t e d t o h o s p i t a l . D e p a r t m e n t of C a r d i o v a s c u l a r Medicine, East Birmingham Hospital, BirminghamNifedipine, a calcium a n t a g o n i s t a n d p o t e n t vasod i l a t o r , h a s s h o w n g r e a t potential as a n antih y p e r t e n s i v e a g e n t alone (Olivari MT e t l . , C i r culation 1979; 2: ( 5 ) ) or i n combination with 6-blockade ( C o r e a L e s Acta T h e r a p e u t i c a 1980; 6: 177-189). W e report t h e results of t r e a t m e n t with nifedipine f o r a mean p e r i o d of 15 w e e k s ( r a n g e 12 w e e k s to 18 w e e k s ) assessed by continu o u s ambulatory i n t r a -a r t e r i a l p r e s s u r e r e c o r d i n g under s t a n d a r d i z e d conditions as d e s c r i b e d previously by this D e p a r t m e n t (Watson RDS M.H y p e r t e n s i o n 1980; 5: ( 2 ) ) .9 patients with untreated e s s e n t i a l h y p e r t e n s i o n , mean c a s u a l B P 1 7 3 / 1 0 9 g 4 / 7 mmHg ( S D ) w e r e s t u d i e d in the c o n t r o l state a n d t h e n following t r e a t m e n t with nifedipine 1 0 mg p.0. t d s . A t e a c h s t u d y t h e sensitivity a n d s e t t i n g of the baroreflex r e s p o n s e t o i n t r a v e n o u s p h e n y l e p h r i n e w a s m e a s u r e d u s i n g the method of S m y t h HS e t . ( C i r c . R e s . 1969; 24: 1 0 9 ) . R e p e a t monitoring s h o w e d s i g n i f i c a n t r e d u c t i o n s in 24 h o u r B P (153/98Y9/11 ( S D ) mmHg t o 1 3 3 / 8 5 4 3 / 8 (SD)mmHg, p<O.OOl for 5 B P and D B P ) .Variability of blood p r e s s u r e m e a s ...