Causes of isolated aortic insufficiency in an urban population in the 1990s a review of 56 surgical pathology cases.

Until recently, the cause of isolated aortic insufficiency (AI) was usually thought to be inflammatory or rheumatic in most cases. However, at our institution we have noted a high prevalence of myxomatous degeneration (MD) in aortic valves removed for AI. In this study we report anatomic observations on valves from 56 consecutive patients with isolated AI undergoing aortic valve replacement surgery. Fifty-six consecutive aortic valves removed at our institution from 1994 to 1996 for isolated AI and/or aortic aneurysm were reviewed. Anatomic features were compared with clinical history and echocardiographic data. The anatomic results were also compared to 22 age-matched control aortic valves obtained at autopsy. In 13/56 cases (23%), a specific valvular cause of AI was determined (infectious endocarditis, seven cases; chronic rheumatic disease, four cases; congenital bicuspid valve, two cases). Of the remaining (idiopathic) 43 cases, 18 (42%) had severe isolated MD defined as >50% expansion of the spongiosa and disruption of the fibrosa by the deposition of acid mucopolysaccharides in the absence of severe calcification, fibrosis, or other pathologic findings. Only 1/22 aortic valves from the autopsy controls had severe MD. Eighteen of the 56 patients also had a clinical history of aortic dilatation/aneurysm of which 12 were confirmed to be dilated by echocardiographic criteria. Of these 12, five (42%) had MD of the aortic valve only, three (25%) had both MD and cystic medial degeneration (CMD) of the aorta, two (17%) had CMD of the aorta only, and two (17%) had no specific diagnosis. Isolated MD of the aortic valve is the most common cause of isolated AI in our patient population. Furthermore, in a subset of non-Marfan's patients with both AI and dilatation of the aortic root/aortic aneurysm the incidence of MD is even higher (67%). These results suggest that there is overlap between MD and CMD in non-Marfan's patients and that both entities may be part of a spectrum of a generalized connective tissue disorder.

Dependence of surfactant function on extracellular pH: mechanisms and modifications.

We investigated alterations in pH on the surface properties of natural lung surfactant and the calf lung surfactant extract (CLSE), suspended in 10 mM N-2-hydroxyethylpiperazine-N'-2-ethanesulfonic acid, using a pulsating bubble surfactometer. Increasing the pH value of the medium to > 7.4 decreased the ability of CLSE, but not of natural lung surfactant mixtures (2 mg phospholipid/ml), to achieve a low minimum surface tension during dynamic compression and enhanced their sensitivity to albumin inactivation. These detrimental effects on surface tension were reversed by addition of surfactant protein A (SP-A; 3% by weight) or by increasing the lipid concentration to 4 mg/ml. SP-A-induced lipid aggregation at pH 10 was not different than at pH 7.4. Alkalinization impaired the ability of CLSE to restore normal lung mechanics in excised surfactant-deficient rats lungs. These results indicate that cooperation between SP-A and the hydrophobic surfactant proteins has an important role in achieving low minimum surface tension at pH > or = 7.6.