Mavroudis - Single Ventricle

-1989 multivariate analysis of Fontan pts

-McGoon ratio ((RPA+LPA diam just before each branches)/(desc Ao diam at diaph)) --> #1 risk factors for death or Fontan take-down

-Fontan failure risk is higher if McGoon is <1.8

-1993 study:

-Nakata index ((LPA+RPA...)/BSA)

-lower Nakata found to be a r/f for failing Fontan by some (Craig, 1993) but not others (Reddy 1996)

-both indecies are questioned bc they don't acct for pulm vasc bed or for PA distortions bc of prior shunts

Surgical preparation for Fontan Circulation-

Neonatal & Early Infancy

-Systemic to PA shunts

-If need more Qp, but PVR still high...

-in past- directly connected Ao to PA, but --> unpredictable Qp, and much PA distortion

-reduced w current use of prosthetic interposition shunt, usually bn SCA or Innom and the PA = modified BT shunt

[see Mavroudis Ch 16 for more info about syst to PA shunts]

PA Banding

-if too much Qp, use PA band to protect vasc bed fr pulm vasc dz and ventric dysfx

-hard to make it just right tightness; sometimes it migrates, distorts PA or erodes PA, and may cause/worsen subAo stenosis bc of myocardial hypertrophy fr the incr in AL and reduced vol load of the ventricle

-higher risk if the Ao arises fr a small outlet chamber (Tri atresia, DILV, VA discordance), espec if the VSD is small or there is arch obstruction

-in this pt population- PAB is c/i xx. Instead do a Lamberti modification of DKS operation to ensure unobstructed arterial outflow. - re--establish oulmonary Q via a systemic or venous shunt; or you could do a Norwood approach

[Mavr ch 17 for details on PA banding]

-eventually, the PA band will become too tight

Physiology of R Heart Bypass Operations

Cavopulmonary Anastomosis

-Diffs bn a systemic Vein to PA shunt over a syst Artery to PA shunt

-more desaturated blood shunted to lungs--> more efficient oxygenation

-about 1/3 of systemic venous return is diverted to the lungs--> less vol load on heart

-Classical CP Anastomosis

-SVC to R lung - rarely done bc it --> R to L PA discontinuity, and if you do a Fontan later, major reconstructive surgery is needed to establish continuity bn the 2 PAs, or the IVC has to be diverted to the smaller L lung (w 2/3 of the Q)

-Instead, do a bidirectional CP Anastomisis- SVC end to side to RPA... Q to both lungs

-Hemi Fontan = alternative- connect the RA-SVC jct and the PAs and patch augment the central PA

-was popular w HLHS after Norwood

-Should take down any additional pulm shunts at time of the anastomosis

-studies show no diff in long term survival by keeping them...

-They do a Glenn as an initial or definitive palliation in pts not ready for a Fontan:

-young (<1-2yo)

-Need much PA reconstruction

-SubAo obst w severe systemic ventric hypertrophy

-borderline PVR or syst ventric fx

-If pt has interrupted IVC and azygous continuation (usually L isomerism) --> good Glenn candidate bc SVC gets all syst vn Q except hepatic/coronary = Kawashima, 1984

-often have 2 SVC, so need bilat Glenn

-Late Glenn xx

-preferential Q to lower part of teh lungs

-dvp venous collaterals bn SVC/IVC territories

-dvp PA fistulas (AP collats)

-progressive incr in PVR bc incr Hct

-decr in Glenn efficacy w age - bc less cerebral Q relative to body as pt head relatively smaller...

-Profound cyanosis soon after Kawasima - seen, ? bc of abNl systemic venous connections in isomeric hearts

-1 pt - abNl intrahepatic syst to hepatic vn communications

--> sats incr after a transcatheter occlusion of these connections (Slavik 1995)

-1 pt - early dvp of pulmonary arteriovenous fistulas (Knight/Mee 1995)

-redirecting hepatic Q to the lungs reduces these

-Atrio-Ventricular Connection

-used to be done in hearts w subPA ventric chamber, assuming that it might help contribute to Qp

-e.g small RV in absent R AV connection (tri atresia), or small RV w Pulm Atresia IVS

--> no longer done bc poor late performance

-Atriopulmonary Connection

-1971 Fontan & Baudet describe that a nonhypertrophied RA could be incorporated into the Fontan

-but the RA pump is not as efficient, poor Q energetics...,

-long term RA distension --> arrhythmia, thrombo-embolic xx

-Total Cavopulmonary Connection (TCPC)

-SVC Q directly into PAs (bidirectional CP anast, or hemi-Fontan) AND channel the IVC to the PA via a lateral tunnel, intra-atrial tunnel, or extracardiac conduit

-better flow dynamics, decr risk of thrombosis/arrhythmias

Surgical Techniques

Superior Cavopulmonary Anastomosis

Bidrectional Cavopulmonary Anastomosis

-Prefer to do it via midline sternotomy, on bypass

-remove most of thymus, expose innom vn

-SVC mobilized

-ID phrenic nerve

-ligate azygos vn to prevent run-off fr the higher P SVC to the lower pressure IVC

-if there is interrupted IVC, then must keep azygos patent...

-dissect MPA & RPA

-cannulate, bypass

-no cardioplegia

-occlude any prior AP shunt

-snare around the SVC, around the venous cannula, or occlude SVC w a vascular clamp

-vasc clamp just above the SVC-atrial jct, don't damage SA nd

-divide SVC just above the clamp, and oversew cardiac end

-release RA clamp

-clamp the sup aspect of the RPA, and make long incision in RPA fr origin to branching

-disconnect any PA shunt prev placed, and oversew this area

-extend opening in RPA centrally

-anastomose SVC to PA w running suture

-rewarm and off bypass

-usually leave additional Qp sources patent (e.g. MPA w PS)

-repeat on other side if bilat SVC, unlesss there is a large bridging vein

-Ligate hemi-azygos vn unless there is hemi-azygos continuation of the IVC, and the L cavopulm anast is constructed as described for the R side....

-some surgeons pref to avoid direct cannulation of SVC for bypass, espec if it is very small' instead do it w deep hypothermic circ arrest; or make a temporary shunt bn SVC and RA, avoiding use of bypass

Hemi-Fontan

-see Ch 41 for HLHS

Total Cavopulmonary Connection

Intracardiac Connection

-mobilize the SVC, don't damage phrenic nerve

-dissect azygos vein, MPA, branch PAs

-double ligate the lig arteriosum and then divide it

-remove syst to PA shunts

-cannulate Ao and cavae

-CP bypass, hypothermia

-snare SVC at the cannula or use a vasc clamp

-vasc clamp at SVC RA jct

-create bidirectional cavopulm anast w beating heart (Glenn)

-Cross clamp Ao

-cardioplegia

-Transect MPA

-Close prox stump of MPA, reinforced w 2 small Teflon felt strips, incorp valve leaflets into suture

-prevents prox PA aneurysm

-Patch close the distal MPA

-Open RA, keep ASD open/enlarge as needed

-Then (either:)

1- Conduit insertion - Open RA at appendage, reduce bypass Q, remove IVC clamp/snare, and palce a sump sucker at IVC at cannulation site --> you can see the IVC orifice fr within RA

-measure RA length fr Eustachaian valve to crista terminalis

-Gore-tex prosthetic at least 18mm is sewn in IVC at jct w RA and then dewn on the prominant ridge mae by crista terminalis, in front of the SVC

-close RA atriotomy

2- Lateral Tunnel

-Create a lateral wall- Take a Gore-tex conduit at least 16mm diameter, and size and split longitunidally, then sew the baffle halfway round the IVC-RA jct, along posterior atrial wall, crista terminalis, and halfway round the SVC jct. Ensure you don't get the SA nd. Then close the RA atriotomy

-then for either 1- or 2-, incr the CP bypass perfusion

-enlarge MPA incision twd RPA or make an anast at underside of the RPA only

-anastomose the cardiac end of the SVC to PA; +/- patch plasty to PA

-DON'T anast the MPA to the SVC,bc it distorts the PA, which has to be brought R and ant'ly

Extracardiac Connection on CP Bypass

-same cannulation as above

-dissect PAs, do the bidirectional cavopulm shunt if not already done w beating heart

-transect MPA

-dissect space bn the RLPV andthe IVC, avoid phrenic n

-bring conduit into a gentle curve to undersurface of the RPA, extending onto the MPA or LPA as needed, trim it obliquely so that it is flush w the PAs

-temp occlude SVC shunt

-incise inf surface of PA, and anast the Goretex conduit to the bottom of PA end to side...

-snare IVC cannula, place vasc clamp across the IVC-RA jct, avoiding obstruction to coronary sinus flow into the atrium. Transect IVC-RA jct, and oversew RA end in 2 layers..

-anast the conduit to the transected IVC

Extracrdiac Connection without CP Bypass

-by isolating a segment of the PAs, --> divert Q fr the R lung only...

Additional Procedures

Fenestrated Intra-atrial Baffle

-early post Fontan mortality is related to transient HD xx, e.g. incr in PVR or decr in ventric fx

--> systemic venous hypertension--> capillary leak--> pleural/pericard effusion w hypertension in lymphatic system --> incr PVR more... = vicious cycle

-fenestration allows for R to L pop-off, first used in early 1990s

-Gorlin formula to calculate size: 1/3 of systemic venous return is diverted to LA --> SaO2 will be >85% assuming a mixed vn O2 sat of 60%. For a RAP of 15mmHg and LAP of 10mmHg, and if 1/3 of venous return travels thru the atrial communication, then a defect of 6mm/m2 is needed.

--> in practice a 4-6mm diam defect unloads the systemic venous circulation while keeping systemic SaO2 >85%

-can be closed by cath later PRN

Relief of Subaortic Stenosis

-often xx w DILV or tri astresia w VA discordance

-PA band can worsen it

-it is signif if the VSD is <1/2 diameter of the Ao vlv in end systole by angio or echo, or if there is a >10mmHg gradient at rest by cath or Doppler

Responses:

1- Enlarge the Restrictive VSD

-main risk is heart block

-conduction axis in DILV or tri atresia is on the LV aspect of the apical or R sided border of the defect, so safest area to excise is the roof of the defect (outlet septum) or the segment closest to the obtuse margin of the heart (L border of the defect)

-might perform it thru a RV incision rather than thru the RA, but xx of ventric aneurysm is high, and a transaortic approach is preferred

2- Use a SubPulm Outflow Tract for Relief of the Systemic Outflow Obstruction

-Lamberti modification of the Damus-Kaye-Stansel procedure is #1 used Tx for subAS here

-transect MPA at bifurcation, and anastomose it to the aorta via a circular aortotomy

-combine w a Fontan, Glenn, or systemic to PA shunt

TCPC in Isomeric Hearts

-hepatic veins may return separately (e.g. RA isomerism), so need to direct Q to the lungs via an intra- or combined extracardiac conduit

RESULTS

Death before or Unsuitability for a Fontan

-2004 study for 1970-1990s - 30% pts w tri atresia were ineligble or died before Fontan

-r/f- earlier birthday, lower birth wt, Ao arch xx, severe RV hypoplasia, no palliation done

-heterotaxies do worse- 49% 1 yr survival reported in 1998

Fontan Operation Outcome

Early Mortality & Morbidity

-Over the first 30 yrs after starting it, operative mortality went down fr 20% to 5%

-for both intracardiac and extracardiac

-likely bc better efficiency of lateral tunnel and extracardiac conduits, redcued cross clamp and bypass times

-?if fenestration helps

-must ensure unobstructed venous pathways. a 1-2mmHg gradient at anast sites must be revised bc --> signif energy loss

-Fontan pts are very Sn to loss of sinus rhythm

-atrial thrombosis has been described - thus rec anticoagulation routinel= heparin then coumadin for 6 wks, espec if prosthetic material used in RA, like a Goretex conduit

-pleural and pericardial effusions and ascites are common

-usually serous

-might be chylous - bc of lymphatic system xx at multiple pts, not just at thoracic duct, bc of systemic vns htn

-Tx w low fat diet (medium chain TG diet), c/s octretoride (anectodtal evidence)

-can Tx w surgery if needed- oversew the area of leakage, ligate thoracic duct, or scarification of the pleura, injecting sclerosing agents- tetracycline, or use of fibrin glue

Late Outcome after Fontan Operation

-1990 study

-even under best circumstances, survival was 86%, 81%, 73% at 5, 10, 15 years.

?why late attrition

-more recent studies

-93% and 91% 5 and 10 yr survival (Stamm 2001 study)

-atrial arrhythmias- a common long term xx, decr w lateral tunnel and extracardiac Fontan

-freedom fr SVT- 86% at 5yr, 91% at 10yr

-r/f = heterotaxy and AV vlv abNlies

-collateral vessels

-systemic venous collaterals in up to 1/3 of Glenn pts

-Pulm atriovenous fistulae reported after Glenn and Fontan

-? why, lack of hepatic factor to pulm vasc bed

--> R to L shnting, hypoxia

-systemic to PA collaterals common too --> L to R shunt--> vol ld the ventricle

-Thromboembolic xx

-early and late

-up to 16% venous thrombosis, 19% stroke, often unrecognized

-?if ppx anticoagulation helps

-they use coumadin x6 weeks postop, then ASA ppx

-Protein-Losing Enteropathy

-?why

-protein loss via GI tract - in up to 15% pts

-50% 5 yr mortality

-periph edema, ascites, effusion, imm-defic, coagulopathy

-elecated alpha 1 antitrypsin in stools

-Tx w diuretics and prtn supp

-steroids and heparin have been successful in reducing prtn loss in some pts

-even cardiac transplant doesnt always help

-Problems related to surgical pathways

-baffle leaks, localized stenosis- mgt via cath

-Ventric failure

-intrinsic myocardial abNlies or xx fr pre-Fontan state- ch cyanosis, vol OD, subAS

-acute preload reduction at time of Fontan circulation --> incr in mass:volume ratio and impaired diastolic fx, and at the same time tehre is an incr in the afterload bc the systemic and pulm circs are now in series--> single ventricles need to spend more energy to generate CO, but have less flow reserve bc of limited preload

Mgt of the Failing Fontan

-failing atrio-pulm connection and arrhythmia--> much improvement if convert to TCPC w arrhythmia surgery, and low operative risk

-ventric dysfx is the main reason for Fontan failure --> c/s heart transplantation

-post OHT R heart failure seen bc of high PVR --> high mortality

-30 day post OHT survival 68%, but no further deaths up to 14 yr f/u (2003 study), not uncommon to die waiting for a heart...