急性升主動脈剝離的治療

急性升主動脈剝離的治療

1. 治療目標：救命，避免不可逆的器官傷害(end-organ damage)。臨床上要高度警覺，快速診斷才有機會。
2. 所有Acute type A aortic dissections都應考慮緊急手術修補(Emergency surgical repair)，以避免aortic rupture或tamponade等致命併發症。
3. Relative contraindications: 有些病人，考量其morbidity/mortality而不開。但也有很多醫龍很敢開成功把病人就回。
• 有 major stroke or coma的病人
• 有嚴重的comorbidity(advanced, debilitating systemic diseases)以致預期餘命不長或不可能復建恢復的病人(preclude meaningful rehabilitation)
• 80歲以上有多種major complications也可能不開。
• 如果病人有新的hemiplegia，開刀也許有機會，不應當作絕對禁忌。Stroke病人在修補ascending aorta後，大多病人仍會有改善(partial or complete neurologic recovery)。
• Paraplegia也是，但spinal cord 若受損恢復的機會較低。
4. 若dissection有影響到其他器官的perfusion (有peripheral arterial complications)，該怎麼辦？
• 以往我們認為surgical repair應優於percutaneous vascular intervention。採用“proximal” or “central” repair 通常可一勞永逸，通常也不須再開刀(<10%)。缺點是要開很久，開刀時狀況不穩
• 但近年來血管介入治療的進步，有另一派認為可以先做導管 (flap fenestration, true lumen bare metal stenting) 先試著維持 end-organ perfusion ，待malperfusion syndrome改善再來開刀。好處在於reperfusion較快(開刀時間短)，可先穩定病人vital signs，準備好再來開刀。但如果在做導管時，end-organ ischemia/infarction已不可逆，病人通常活不了，也沒機會再開刀了。目前約有 15% 的病人會死於aortic rupture
5. Type A IMH：處理同Type A aortic dissection。
• 但在北亞，若Type A IMH沒有併發症，且ascending aorta未擴張，有些人會以藥物來處理。這些人最好密集 follow up image study，因為變化可能會很快。
6. 一旦懷疑 acute type A aortic dissection，就要
1. 監測 神經學狀態，血壓，EKG，UOP，及四肢pulse。
2. 要馬上on A-line, CVC, Foley。
3. 嚴格血壓控制，減少動脈的impulse(↓MAP, ↓ aortic dP/dt)。術前術後都很重要。可減少dissection的進展，降低aortic rupture的風險，還可減輕疼痛。IV antihypertensive & negative inotropics：通常一開始用 beta-blocker 或 CCB ，若有需要，之後可加短效的 arterial vasodilator，如 sodium nitroprusside。
4. 若vital signs不穩，那可能已經發生 aortic rupture, cardiac tamponade, 或severe AR/coronary a. compromise造成的 acute LV failure。
• 若病人有tamponade的證據(低血壓, HR↑, JVE, distant/muffled heart sounds, ...) ：還是要急開。除非不能馬上開才做pericardiocentesis。引流的量不可太多，讓血壓在最低可接受範圍就好。若release tamponade，心臟功能回復會讓血壓急遽竄高而造成aortic rupture。

Surgical Principles

• 在ascending aorta/arch上Primary intimal tear要完全切除
• 遠端的aortic blood flow要確定流到 true lumen
• 若有AR，要重建 sinuses of Valsalva , aortic root並把 valve commissures接回。
• 若aortic root已嚴重毀損If the aortic root is severely damaged by the dissection process, the patient has Marfan syndrome or other connective tissue disorder, severe anuloaortic ectasia is present, or the valve needs to be replaced for other reasons (such as severe aortic stenosis), then complete aortic root replacement with reimplantation of the coronary ostia is indicated by use of either a composite valve graft or a valve-sparing technique, as advocated by Yacoub and David. 
• In most cases, the noncoronary sinus of Valsalva is the most severely traumatized and can be treacherous to reconstruct satisfactorily; replacement of just the noncoronary sinus and the tubular ascending aorta (a “uni-Yacoub” procedure) is a simple approach that works well in these circumstances. Valve-sparing aortic root replacement by the reimplantation method, as described by David and colleagues, might be the ideal technique in the setting of acute aortic dissection in patients with normal valve leaflets, resulting in complete removal of all diseased tissue, improved hemostasis, and low incidence of late reintervention for aortic root or aortic valve problems. 168 The older technique of separate aortic valve replacement and supracoronary aortic graft replacement has been abandoned for the most part in patients with acute type A aortic dissections, except for selected elderly patients when aortic valve competence is not achievable otherwise.

Reference: Sabiston and Spencer's Surgery of the Chest, CHAPTER 70, Type A Aortic Dissection