Creation of ventricular septal defects on the beating heart in a new pig model

BACKGROUND/AIMS

So far, surgical and interventional therapies for muscular ventricular septal defects (mVSDs) beyond the moderator band have had their limitations. Thus, alternative therapeutic strategies should be developed. We present a new animal model for the evaluation of such strategies.

METHODS

In a pig model (n = 9), anterolateral thoracotomy was performed for exposure of the left ventricle. mVSDs were created under two- and three-dimensional echocardiography with a 7.5-mm sharp punch instrument, which was forwarded via a left ventricular puncture without extracorporeal circulation.

RESULTS

Creation of mVSDs was successful in all animals (n = 9) confirmed by echocardiography, hemodynamic measurements and autopsy. The defects were located in the midmuscular (n = 4), apical (n = 1), inlet (n = 2) and anterior part (n = 2) of the muscular septum. All animals were hemodynamically stable for further procedures. The diameter and shunt volume of the mVSDs were 4.8-7.3 mm (mean: 5.9 mm) and 12.9-41.3% (mean: 22.1%), respectively. Autopsy confirmed in all animals the creation of a substantial defect.

CONCLUSION

The described new technique for creation of an mVSD on the beating heart in a pig model is suitable for the evaluation of new therapeutic strategies for mVSD closure.

Highly selective formation of [4+2] and [4+3] cycloadducts of tetrahydroindenes generated in situ from a (1-alkynyl)carbene tungsten complex by the metalla-1,3,5-hexatriene route

1-Amino-3-ethoxytetrahydro-3aH-indenes 8 can be readily generated together with pentacarbonyl(pyridine)tungsten in a template induced three-component reaction of [(1-cyclohexenyl)ethynyl]carbene tungsten complex 1 with secondary amines 2a-d and pyridine. Even though the compounds 8 are thermally quite unstable and undergo a fast rearrangement to tetrahydro-7aH-indenes 7. they can be trapped by formation of (rather strained) [4+2] cycloadducts 12 with maleimide 11. If 1-amino-3-ethoxytetrahydro-3aH-indenes 8 are generated in the presence of electron-poor alkynes 2a and 2b, they undergo a 1,5-shift to give tetrahydro-7aH-indenes 7, which in turn afford [4+2] cycloadducts 4a-d. Condensation of 1-tungsta-1,3,5-hexatrienes (3E)-5a-d with 1-metalla-1,3-butadienes 14 (M = Cr, W) give [4+3] cycloadducts 15a-e of tetrahydro-7aH-indenes 7 in good yields with high regio- and stereoselectivity.

Enaminone substitutents attached to cyclopentadienes: 3E/3Z stereochemistry of 1-metalla-1,3,5-hexatriene intermediates (M = Cr, W) as a functional criterion for the formation of cyclopentadienes and six-membered heterocycles, respectively

Reactions of NH-enaminones 2 with [2-(1-cycloalkenyl)ethynyl]carbene complexes 7 (M=W, Cr) gave tetrahydropentalenes, tetrahydroindenes, and hexahydroazulenes 8a-i, in which the NH-enaminone moiety is attached to the cyclopentadiene unit. The reaction involved formation of (3E)-1-metalla-1,3,5-hexatriene intermediates, which underwent pi cyclization faster than 3E/3Z isomerization. Tungsten complexes 12 and 13 were characterized as reaction intermediates. Compounds 8 are potentially bidentate ligands with respect to coordination both of the cyclopentadienyl and the enaminone moieties.

"Dimers" and "trimers" of tetrahydroindenes and hexahydroazulenes, respectively generated from [2-(1-cycloalkenyl)ethynyl]carbene complexes (M = W, Cr) by cascade cyclization/cycloaddition reactions

A cascade of cyclization/cycloaddition reactions was triggered by addition of protic oxygen nucleophiles ROH 2 (RO = CH3CO2, PhCO2, PhO) to [2-(1-cyclohexenyl)ethynyl]carbene complexes 1b and 1c (M=W, Cr, respectively), affording highly strained "dimers" 11/11' and "trimers" 12 of the carbene ligand. The first reaction step involved the formation of 1-metalla1,3,5-hexatrienes 7, which readily gave tetrahydroindenes 8 by pi cyclization and extrusion of the metal unit. "Dimers" 11/11' were generated from tetrahydroindenes 8 by a highly exo selective [4+2] cycloaddition of compounds 1b and 1c to afford 1-metalla-1,3,5-hexatriene intermediates 9, and a spontaneous pi cyclization of the latter compounds involving the disengagement of the metal unit. Propenylidene cyclohexenes 13/13' were formed in "ene"-type side reactions to the pi cyclization of 1-metalla-1,3,5-hexatrienes 7, by loss of the metal unit. "Dimers" 11 were transformed into "trimers" 12 by a [4+2] cycloaddition and subsequent pi-cyclization of the resulting 1-metalla-1,3,5-hexatriene system. The course of the reaction was elucidated by means of model reactions with (2-phenylethynyl)carbene complex 14, in which 1-metalla-1,3,5-hexatriene intermediates 16 and 17 were isolated and characterized. Alkynyl benzene derivatives 19 were obtained by an unprecedented ring-expansion of a cyclopentadiene unit of "dimers" 11a and 11c, involving the insertion of a carbene carbon atom of compound 14 into a C=C bond. A reaction cascade leading to "dimers" 24/24' could also be triggered by treatment of compounds 2 with [2-(1-cycloheptenyl)ethynyl]carbene tungsten complex 1d.