CatheterSeptotomy in Type B Aortic

Transcription

1 CatheterSeptotomy in Type B Aortic Dissection Ram on Berguer Juan Parodi University ofmichigan

2 The Hypothesis In a dissected aorta the lum en w ith the higher outflow resistance w ilhave the higherm ean and diastolic pressure. This differentialofpressure triggers the aneurysm aldevelopm entofthe false lum en

3 Italso explains w hy patients w ith chronic dissections, and a partia ly throm bosed false lum en ( hence w ith increased outflow resistance) develop aneurysm s and die 2.4tim es m ore frequently than those w ho do nothave any throm bus in the false lum en orhave no false lum en ata lbecause ithas throm bosed Insertpaper here

4 W e have show n this elevated diastolic pressure in the false lum en w ith restricted outflow in our physicaland m athem aticalm odels ofaortic dissection Tsai, T.T., Schlicht, M., Khanafer, K., Berguer, R., Bu l, J.L., Montgom ery, D.G.,Valassis, D., W iliam s,d.m., Eagle, K., etal. Tear Size and Location Im pactfalse Lum en Pressure in an Ex-Vivo Modelof Chronic Type B Aortic Dissection. J. Vasc Surg. 47: ,

5 Traditionally itis believed thatthe false lum en becom es aneurysm albecause its thinned outer w allcannotw ithstand system ic pressure. W hy is itthatthousands ofendarterectom ies in differentsegm ents of the entire aorta never evolve into aneurysm s? After all, the plane of dissection is the sam e as thatofendarterectom y. Insertpicture here

6 Itm ay be argued thatthese endarterectom ized aortas ( to treataso ) did notdilate because they did nothave the elastin and collagen anom alies found in the dissected ones. Butw hen w e looked at segm ents ofdissected aortas thathad an open fenestration to treat visceralor pelvic ischem ia w e did notsee any long-term dilatation in the fenestrated segm ents

7 Given thatthe presence ofa pressure differential correlates w ith the long-term aneurysm aldilatation of the false lum en, itcan be posited thatthis pressure differential ratherthan the thin w allofthe false lum enis the cause ofthe developm entofaneurysm s follow ing an acute dissection Berguer R, ParodiJ, SchlichtM, Khanafer K.. Experim entaland Clinical Evidence Supporting Septectom y in the Prim ary Treatm entofacute Type B Thoracic Aortic Dissection. Ann Vasc Surg :1-7

8 Using num ericaland physicalm odels ofaortic dissection w e have calculated how large a fenestration- a septotom y - needs to be in order to equalize the pressure in both lum ena Sm allproxim al/large Distal Bench top m odel

9 Correlationbetw eent otala reaofthet ears izesand thep ressure Differencebetw eenfalseand T ruel um ena

10 A distaltear of>40 0 m m 2 elim inated any pressure difference.

11 In acute aortic dissection, septotom y ofthe infrarenalaorta equalizes the blood pressure in both lum ena and ifapplicable- itcan also correctany existing m alperfusion Itm akes sense to elim inate ( w ith a septotom y) w hatappears to be the m ost predictable m echanism forthe future developm entofa false w allaneurysm

12 In chronic dissection a m ore extensive septotom y w illtransform the double-barreled aorta into a single channelsuitable for endografting

13 O urcatheter glides over2 guide w ires previously placed in the false and true lum ena. The guide w ires diverge as the catheter approaches the septum causing the flexible lips ofthe catheter to open exposing the septum to the cutting elem ent Guide w ires 1 &2 RF cutting electrode

14 Explored three possibilities for the cutting elem ent: ( a) ultrasonic blade ( large energy dispersion w hen operating subm erged) ( b) excim er l aser ( expensive generator) ( c) radio frequency ( O ur choice: RF generators are ubiquitous and inexpensive)

15 Aorta w ith both channels ( septum notyetinstalled) Flow direction Therm ocouple port

16 Aortic lum en Spiraling ( 30 ) plane of dissection septum of chicken skin

17 Cutting the septum in the perfusion m odelofaortic dissection

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