-very rare to have isolated congen MS
-usually it is part of a Shone's syndrome - ref18
Anatomy
-xx at paps, cords, leaflets, supravlvr region
-Parachute MV- single pap muscle which takes all the cords- ref 19
-if the cords are fused and thick, then --> block Q into LV
-Supravalvar web- fibrous ring at atrial surface, restricts leaflet motion and may also block Q
-Mitral arcade- fused commissures, thick and immobile leaflets, short and thick cords, and paps insert directly/near directly into leaflet
-very rare to have a pt w MS and an easy commissure fusion that can be opened ipp, unlike AS & PS
-if seen, it is likely rheumatic MS
-MV might have Nl structure but still be stenotic fr underdvpmnt
-i MV area z score is "<2.5-3", then it is not likely that it will serve as a useful valve, even if its otherwise normal appearing
Path & Sx
-incr PAP & RVP, assoc w FTT, may be PGE dependent as a neonate, usually if Shones+ or HLHS.... rare w isolated MS; pulm congestion w incr risk w resp infections...
Dx
-CXR- pulm congestion, big PAs
-ECG- prominent R heart forces
-Echo -make Dx
-define structure xx, vlv, subvalv, supravlv
-measure MV diam in 2 planes to calc the area
-mild MS = mean MV grad <4-5, 6-12 mild, >13m/s sev - but note that gr d/o amt of Q across the valve, so incr if assoc VSD..., decr w ASD...
-check RV P
Rx Tx
-CHF Tx...
-if not working and +FTT/freq resp infections, then c/s balloon dilation of the vlv -ref 21
-but ensure surgeon aware bc it is much higher risk surg if unsuccessful; over long term pt will need surgery usually
-don't attempt if it's a parachute vlv, bc will --> regurg
Surgical Indications
-Balloon dilation is preferred if possible; thus #1 is pt who was considered for a balloon but deemed not a candidate
-surgical valvotomy doesn't usually have good result; you usually can tell by echo if it wil be a good repair
-failed balloon dilation or balloon dilation complicated by dvpmt of sever MR
Surgical Mgt
MV Repair
-resect supravalvar MV ring/web - effective
-usually can peel it away fr atrial surface of MV leaflets--> free them up, not as restricted
-Commissurotomy- usually not possible except over a minimal distance of 1-2mm
-must avoid making a flail leaflet segment, so you must know the cordal anatomy
-Split and thin fused and thickened cords by excising interchordal fibrous tissue
-if pap muscles insert directly onto the leaflet, may be able to split prox pap muscle to open up the orifice
-long term results of splitting cords/paps is "disappointing"- ref 22; so if you need to do it, don't be optimistic
MV Replacement
-median sternotomy
-CP Bypass w bicaval cannulation w R angle venous cannula (unless neonate, in which case c/s using circ arrest)
-expose MV via vertical incision at atrial septum
-excise the MV, including subvlvr apparatus
-DON'T force too big of an MV into the annulus--> incr risk of complete HB
-if annulus is smaller than the smallest prosthetic, then insert the prosthetic above the true annulus
-Supra-annular MV replacement
-place posterior sutures as close as possible to inf R and L pulm ns, bn the vns and the annulus, without xx to vns. Ant sutures are passed thru atrial septum w pledget on RA side of septum. Vlv should lie above the level of the coronary sinus, which decreases risk of heart block.
-ensure the vlv has free movement of the disk, and if needed rotate it till it has the greatest clearance fr surrounding tissue.
-usually need to close the AS w patch
-fill L heart w saline and vent the air thru the cardioplegic infusion site prior to closing the atrial septal defect
-Enlarging the MV Annulus w Preservation of the Aortic Valve
-enlarge the MV annulus w incision thru LVOT to allow larger prosthetic
-usually also do Ao annulus enlargement w a patch
-use a triangle patch to enlarge MV annulus
-the Ao vlv commissure is reconstructed at the apex of the patch, w pericardial leaflet extension of the RCC and NCC to improve Ao competence
-LA to LV Conduits
-Dacron conduit tone in 1980s or so, poor outcome in some, ok in others...
Surgical Results
Balloon Angioplasty of Congenital MS
-ref 27- 1990 study- n=9 - 7 had improved gradient and vlv area; the ones w poor outcome had unbalanced chordal attchmt w restriction to the vlv apparatus - like w an arrcade vlv where the obst isn't purely vlvr - like w a supravlvr ring; no one had stroke, infection, or death --> thus c/s it in younger pts and pts where MV replace would be trouble
Surgery for Congenital MS
-ref 28 - 1987 study of 24 pts w mainly congen MS, and w 22 pts w congen MR
-overall op mortality 19%, and a 44yr freedom from death and re-operation at 8 yrs
-ref 29- 1995 study of 10 ots w congen MS and 10 w congen MR- mean age 7 months at surg
-6 early re-op in 5 pts; "5 of whom needed MV replacement"; 58% freedom fr re-op at 7 yr f/u
-ref 30- 1990 MV replacement in infancy for 25 pts w MS or MR- 52% 1 yr survival (but pts go back to 1973) and many pts needed supra-annular placement
-ref 31- supravlvr placement has poor results
-ref 32- 2000 study of 13 pts w isolated congen MS- 71% freedom fr re-op and 69% freedom from MV replacement at 15 yrs