[Verse 1] Start with the body, surface area, call it BSA, Match it to a z-score chart, that's how we survey The pulmonary valve that nature built in you, Normal curve's the compass, plus one to plus two Is the target window, not too snug, not too loose, Give the chest some growing room, give the graft a purpose. In teens and grown folks size it twenty-two to twenty-six, Or bigger if the cavity's got room to fix. Leave a margin 'cause tomorrow brings a balloon and a stent, Transcatheter valve's gonna flare where the old rim bent, Twenty-four to twenty-nine millimeters she'll grow, Pick the pipe today that still fits down the road. [Chorus] Z plus one, z plus two, that's the number that we chase, Twenty-two to twenty-six, leave the future valve some space, Homograft, bovine, ePTFE, or a stent in a sleeve, Size it, shape it, lay it left — that's the oath we believe. [Verse 2] Pulmonary homograft, first-line in many a hall, Human tissue, quiet neighbor, rarely rejected at all, But the freezer's running thin, cryopreserved and scarce, Some seasons the bank's empty, leaves the surgeon in a farce. Bovine jugular vein, off the shelf, ready quick, Twenty-two's the ceiling though — past that, you're out of luck. Supply chain hiccups, and a whisper of concern, Endocarditis risk's a flame this graft tends to burn. [Verse 3] ePTFE trileaflet, or bicuspid design, Handmade like a tailor's suit, stitched along the line, No donor, no immune response, the body won't object, Synthetic leaflets flutter clean, nothing to reject. Then the stented bioprosthesis, tucked in Dacron or a tube, Or sewn straight to the RVOT, hooded like a shrewd Old campaigner's cloak — this suits the older frame, Frames that fracture, frames that stretch, built to crack again For valve-in-valve down the years, a balloon splits the ring wide, Like a chrysalis reopening, room for new to ride. [Bridge] Now trace the curve with steady hand, the tunnel must behave, Sinistral — meaning leftward — of the aorta's wave, No kinking in the pathway, no pinch against the bone, When the sternum shuts up tight, give the conduit room of its own, A lazy arc, a gentle bend, no cable stretched too tight, Measure the length and measure the curve before you close tonight. [Verse 4] So weigh the body, read the z, pick tissue or the mesh, Think about the decade coming, not just the surgery's flesh, Homograft for the purist, bovine when the shelf is near, ePTFE for the sensitive, stent for the aging frontier, Curve it left, dodge the bone, leave a berth for growing still, That's the architecture of a conduit built with skill. [Chorus] Z plus one, z plus two, that's the number that we chase, Twenty-two to twenty-six, leave the future valve some space, Homograft, bovine, ePTFE, or a stent in a sleeve, Size it, shape it, lay it left — that's the oath we believe.
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