Epidemiology of the Hypoplastic Left Heart Syndrome in Ontario, 1971–73

Abstract

P e d l a t r t c Cardlology. Chlcaso. (Spon: R o b e r t A. M i l l e r )When the heart stops, a r t e r i a l pressure decays asymptotlcally t o a value d l f f e r e n t from the venous pressure.0ur study was performed t o t e s t the hypothesls t h a t t h l s decay Is influenced by vasomotor tone and contalns Information t h a t could lead t o the development of an Index of vasomotor tone.Twelve anesthetlted dogs were subJected t o brlef periods of cardlac a r r e s t by stlmul a t l n g the d l s t a l ends of the cut vagl.Th1s was done approxlm t e l y 9 times In each dog a t varylng levels of vasomotor tone produced by I V nltroprusslde and methoxamlne and decay of c e n t r a l a o r t l c pressure was rec0rded.A fncthematlcal motel of the lumped a r t e r i a l bed was evolved In whlch each term had recognizable physlologlc meanlng.Uslng multlple nonlinear regression analysis, the pressure-time data were f l t t e d t o t h l s model and, In most cases, f i t ed and observed decays were hardly dlstlngulshable t o 4 the eye ( r values were g r e a t e r than . ? ) . l t was predlcttd t h a t asymptotic pressure. calculated ualng the m d e l . would r l s e o r f a l l a s vasomotor tone rose o r fell.The average asymptotlc pressures under the lnfluence of methoxamlne were s l g n l f l c a n t l y g r e a t e r (F<.05) than control values and average asymptotlc press u r e s under the Influence. of nltroprusslde were s l g n l f l c a n t l y l e s s (P<.05) than average control values. l t Is suggested t h a t these asymptotes may form the basls f o r developing an Index of vasomotor tone Independent of flow measurement. HEMODYNAMIC EFFECTS OF E. COLI ENWTOXIN I N PUPPIES.YL Pipie. Chiemmongkoltip, Masakatsu Goto. Bruce Bernheim, Zenshiro Onouchi. John B. Paton. P r i t z k e r School of Medicine. University of Chicago. Michael Reese Hospital and Medical Center. Department o f -~e d i a t r i c s , Chicago -S e r i a l hemodynamic changes following intravenous E. c o l i OlllB4 endotoxin were evaluated i n 28 puppies. 1-18 days and 270-1800 grams. S e r i a l cardiac outputs were measured by a modified reinfusion dye d i l u t i o n technique. Heart r a t e and systemic arter i a l pressures a l s o were measured. Changes were recorded a t 5 min. 10 rnin and st 10 min i n t e r v a l s t h e r e a f t e r f o r 1 hour following endotoxin. Heart r a t e dropped from 2lO/min t o 14l/mln a t 5 mln and s t a b i l i z e d a t a s l i g h t l y higher l e v e l t h e r e a f t e r (p < 0.01). Mean systemic pressure decreased gradually from 70 mm Hg t o 42 mm Hg a t 1 hour (p < 0.01).Cardiac index decreased from 266 ml/mln/kg t o 131 ml/min/kg a t 5 rnin and continued t o decline t o 115 ml/mtn/kg a t 1 hour (p < 0.01). Systemic vascular resistance rose from 0.467 u n i t t o 0.846 u n i t a t 5 rnin and remained elevated a t s l i g h t l y lower l e v e l a t 1 hour (p < 0.01).Minute work decreased a t 5 rnin from 0.301 Kg-m/kg t o 0.134 Kg-m/kg and t o 0.066 Kg-m/kg a t 1 hour (p < 0.01).Mean e j e c t i ...