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lortac und pulmonary valve cusps f r o m mongrel dogs were suspended tit a nutrient medium and exposed for one week at 4' C to an antibiotic solution and were thereafter stored in nutrient medium without antibiotics at 4" C. The cusps were subjected to tissue culture and ncirroscopic exainination at intervals ranging f r o m one day to five weeks after collectzon. Growlh of fibroblasts was noted on tissue culture in 93% of ousps after 24 hours, in 61% rrftcr oiw zc'cek and in 15% after two weeks. There wus no growth beyond two zc$ecks. Elertron iiiicrosropx fxamination showed progressively severe ultrastructural changes recog?ki;ablc cifter the cusps had been in the antibiotic solution for 24 hours. This and other studies on human material make it clear that satisfactory function of antibiotic-sterilized valve allografts is not primarily dependent on viable graft fibroblasts.THE clinical results of cardiac valve replacements with aortic and pulmonary valve allografts have improved a great deal in recent years. This has been contributed to by modifications in the methods of preparing the grafts (Rirratt-&yes and Roche, 1969 ; Gerbode, ivoci: Barratt-noyes et a%, 1972), and some workers have suggested that maintenance of (lonor cell viability is an important consideration (Angell r t a%, I972 ; Angell et alii, 1 9 7 3~) .This paper reports and discusses the effects produced by preserving canine aortic and pulmonary valve cusps by the methods currently in clinical use at Green Lane Hospital. MATERIALS A N D METHODSAortic and pulmonary valve cusps were obtained from 63 mongrel dogs within one hour of death. The cusp\ were removed by a clean, but not a sterile tcchniqiie, and were immediately placed in Hanks's halanced salt solution. The cusps were then taken to the tissue culture lahoratory, where they were transferred to jars containing Medium 199 (Commonwealth Serum Laboratory, Melbourne). Membranefiltcretl fetal calf 5erum (Australian Laboratory Services, Rockdale) was added to make up 10% of the volume of the solution. A stock solution of antibiotics was finally added to give a concentration per milli-Supported hy a grant from The Medical Re-Reprint?. Sir Brian Barratt-Boyes, Green Lane search Council. I I m p i t a l , \iickland 3, New Zealand. litre of 50 units of penicillin, I mg of streptomycin,

We describe a patient who developed the unusual haemodynamic phenomenon of periodic intermittent electromechanical dissociation during regular sinus tachycardia about 20 hours after mitral valve replacement with a tilting disc mechanical prosthesis. Echocardiographic confirmation allowed prompt and life saving corrective surgery for a stuck prosthetic valve disc.