Case Discussion ＜Case Presentation＞ 病史： 病人為七十八歲男性病人，自青少年時即知道有心雜音。由於自覺一直沒有任何症狀，病人並未尋求任何治療。 據病人陳述，他一向有規則的運動習慣，但是在六十歲左右時，出現運動比較會喘，爬到三層樓時就會出現氣促，需休息一下才能繼續爬。此外，並未出現胸悶不適之現象。病人至本院門診求診時，理學檢查發現有輕微的下肢水腫，肺部無囉音，在左前胸有一grade II-III/VI pansystolic murmur，接受心臟超音波及心導管檢查，證實為一小型心室中膈缺損，並有心臟輕微擴大現象；病人開始接受規則的藥物治療，而當時並未建議任何手術的治療。 然而，病人於六十二歲時有一次發燒，在住家附近的小診所拿藥，長達數週一直未癒，並且在發燒兩週之後，出現突發性的左側嘴角歪斜。住進本院之後，當時的心臟超音波顯示在主動脈瓣及心室中膈缺損上有一贅生物，同時腦部的電腦斷層顯示有一腦部膿瘍。於是病人接受了長達六週的抗生素治療。之後並接受了開心手術，本次術式包括了心室中膈缺損修補及主動脈瓣膜置換（豬瓣膜）。後來均規則在本院的心臟外科門診追蹤，狀況良好。四年前去美國定居，在美國並沒有規則追蹤心臟的病情。 病人在今年出現運動時氣促現象，上樓梯至二樓就會很喘，又回國至本院求診，於是醫師安排病人入院接受心導管的檢查。當時的血行動力學檢查如下：肺動脈揳壓 11 mmHg，肺動脈壓 40/16 (mean : 22) mmHg，左心室壓 162/26 mmHg。而主動脈攝影顯示主動脈瓣退化併重度的主動脈逆流。於是病人接受了第二次主動脈瓣膜置換（Homograft，又稱為allograft）。在術後一週時，病人出現陣發性心房震顫，於是再接受整律治療（cardioversion），並順利恢復成竇性節律。目前病人接受毛地黃、利尿劑及鈣離子阻斷劑等藥物控制，狀況穩定。 討論： 心室中膈缺損為最常見之先天性心臟病（約佔先天性心臟病的20%），其基本分類為（一）supracristal，又稱作infundibular，juxtaarterial（subarterial），或conal，（二）perimenbranous，或paramembranous，（三） inlet 或atrioventricular canal（四）muscular四種形式。部分之心室中膈缺損會自動癒合，根據研究顯示較大的心室中膈缺損自動癒合者多在出生後十二個月內發生，鮮少在四十八個月之後。其大小及位置亦影響其癒合的機率。較大的心室中膈缺損時因過高血流至肺動脈，會引起阻塞性肺血管疾病之後遺症，宜於兩歲以前矯治，才能避免之。 心室中膈缺損引起的併發症，常見的有主動脈瓣閉鎖不全、感染性心內膜炎、阻塞性肺血管疾病、次發性肺動脈狹窄（infundibular type）及心臟衰竭。主動脈瓣閉鎖不全常發生於疾病的較後期，以perimenbranous型最易發生，佔53%，而supracristal型佔31%。原因包括支撐力不足或血流影響。研究顯示受影響之主動脈瓣葉以right coronary cusp最多，佔50%， non-coronary cusp佔28%，二者都受波及者佔 6%。 在心室中膈缺損手術之適應症應考慮是否有意義之分流，而主動脈瓣置換則在主動脈閉鎖不全中度及以上之程度才考慮。主動脈閉鎖不全若因心室中膈缺損引起之次發現象，而無結構性變化，可能因單獨心室中膈缺損手術而改善。 感染性心內膜炎的發生率則為每年約為0.4%，心室中膈缺損得到感染性心內膜炎的危險為中度，在可能引起菌血症的檢查或手術前，必須接受抗生素預防。目前對於感染性心內膜炎的診斷準則大多根據1994年的Duke Criteria。至於胸前心臟超音波的敏感度，仍不夠高，必要時需要利用經食道心臟超音波診斷。超音波診斷贅生物的準則包括會漂動的附著於瓣膜葉片或肌壁（mural myocardium）的echodense mass、periannular 膿瘍、或是置換的瓣膜出現新的脫落現象（dehiscence）等。一旦診斷出來，亦可利用超音波估併發症的機率。危險因子包括為人工瓣膜、左側瓣膜、，S. aureus、黴菌性、過去有感染性心內膜炎病史、症狀較久（大於三個月）、cyanotic heart disease、systemic to pulmonary shunt、或對抗生素反應不佳者。超音波上大於一公分的贅生物較危險，且僧帽瓣（25%）（尤其是前葉）比主動脈瓣（10%）更易出現血管栓塞（embolization）。其可能時間為診斷前，治療中（尤其前二至四週），亦偶發生於治療結束後。出現兩次以上重要血管栓塞事件後應考慮手術。腦部膿瘍（＞90%發生在middle cerebral artery區）出現時預後較差。 人工瓣膜分成生物瓣膜及機械性瓣膜，由於後者需抗凝血藥物預防血栓，對老人或出血傾向者不宜，而warfarin有致畸胎傾向，年輕想懷孕者不宜。又生物瓣膜（尤其是僧帽瓣）較易磨損且使用期限較短，所以不建議年輕人使用。目前一般原則為大於六十歲置換主動脈瓣者、及年輕婦女想懷孕者建議生物瓣膜，可避免抗凝血劑的問題。Homografts則是指從cadavers取下經過無菌處理，不加prosthetic stent者，近年來使用增加；因為具有低血栓形成（所以不需抗凝血藥物預防血栓）、較不易感染（對因感染性心內膜炎而須緊急置換者尤佳）及較佳的血行動力性質；缺點是較不易取得，且和豬瓣膜一樣，損耗率較高（10年損耗率約20%，術後15年則超過50%）。 繼續教育考題 1. (D) All of the following statement s regarding ventricular septal defects (VSD) are true EXCEPT: A It is the most common form of congenital heart disease in infants and children. B The most common VSD occurs in the membranous septum. C Spontaneous VSD closure occurs in 45 percent of patients by the age of 3 years. D Spontaneous closure occurs primarily by continued growth of the muscular septum. E Complete heart block following surgical repair is uncommon 2. (B) Each of the following is considered a high-risk lesion that predisposes to infective endocarditis EXCEPT:  A Aortic stenosis B Mitral valve prolapse with systolic click (no murmur) C Patent ductus arteriosus D Ventricular septal defect E Chronic aortic regurgitation 3. (C) The statements regarding the use of aortic valve homografts in the surgical management of aortic valve disease including all to the following EXCEPT: A Homografts have low thrombogenicity and do not require chronic anticoagulation therapy. B  Homografts are the prostheses of choice for patients in need of urgent cardiac surgery for infective endocarditis of the aortic valve. C The rate of structural degeneration of homografts is significantly less than that of porcine prosthetic valves. D Homografts offer a more favorable hemodynamic profile than mechanical valves. E The operative mortality of aortic homografts placement is similar to that of mechanical and bioprosthetic valve replacement. 4. (D) Which of the following statements about infective endocarditis is TRUE? A Endocarditis is not present if valvular vegetations are absent by transthoracic echocardiography. B Endocarditis caused by S. aureus is an absolute indication for surgery. C In patients with endocarditis, a vegetation ＞ 10mm, in diameter represents an absolute indication for surgery. D  The likelihood of subsequent embolic events will decrease with appropriate antibiotic therapy. E  Even if intractable heart failure develops, corrective valve surgery should be postponed until well after blood cultures have sterile. 5. (C) True statements about the natural history of untreated VSD include all of the following EXCEPT:  A  The natural history of VSD may differ depending on the size of the defect and the magnitude of the pulmonary vascular resistance. B  Regardless of size, the presence of a VSD confers an increased risk of endocarditis. C Progressive pulmonary vascular disease with reversal of shunting (Eisenmenger complex) usually occurs during the fifth decade of life in those patients with VSD who will develop this complication. D Infundibular pulmonary stenosis may develop gradually in occasional adult patients with isolated VSD. E Women with VSD that lead to ratios of pulmonary to systemic flow ＜ 2:1 gradually tolerate pregnancy well. 6. (E) Which of the following statements about endocarditis caused by S. aureus is TRUE? A Central nervous system complications are rare, occurring in fewer than 5 percent. B S. aureus native valve endocarditis is an absolute indication for surgical debridement. C The prognosis of right-sided S. aureus naive valve endocarditis is similar to that of left-sided S. aureus endocarditis. D Vancomycin is the antibiotic of choice for treatment of S. aureus endocarditis. E Prosthetic valve endocarditis with S. aureus is associated with a high mortality rate in patients treated medically. 7. (B) Which of the following statements regarding various congenital heart diseases is TRUE?  A Isolated VSD is more common in adolescents and adults than in infants and children. B The non-cardiac features of atrioventricular septal defect have the most influence on management in adolescence and adult life. C Survival in unoperated patients with tetralogy of Fallot (TOF) is fairly normal until age 40. D Adults with TOF are not suitable surgical candidates. E The decreasing benefits with age of surgical repair for pulmonary stenosis is dependent on the use of ventriculotomy and outflow patches. 8. (B) Which of the following statements regarding the management of patients with prosthetic heart valves is TRUE? A The most important cause of postoperative ventricular dysfunction is previous myocardial damage. B The most common cause for dysfunction of mechanical prosthetic valves is thrombotic obstruction. C Coronary bypass surgery should not be performed at the time of valve replacement, due to greater risk of operative mortality. D Bioprosthetic aortic valve failure is more common and occurs more rapidly in older patients than younger patients. E Echocardiography/Doppler ultrasound is not necessary unless the patient shows signs of valve dysfunction. 9. (A) Which of the following statements regarding a VSD is TRUE? A The VSD may be associated with coarctation of the aorta. B  In most infants, VSDs can lead to right ventricular failure. C Surgical closure of a VSD with aortic regurgitation does not lower the risk of infective endocarditis. D  Most VSDs remain large at age of 6 months will still undergo spontaneous closure. E Patients with a VSD who have survived to 5 to 10 years of age are no longer candidates for surgical closure of the defect. 10. (D) According to the Duke criteria, which of the following patients is most likely to have infective endocarditis? A The patient in whom the manifestation of endocarditis have resolved fully by the 4th day of antibiotic therapy. B  The patient who has Roth’s spots, fever, and a predisposition to infective endocarditis. C The patient who has an oscillating intracardiac mass and a predisposition to infective endocarditis. D  The patient who has oscillating intracardiac mass and two positive blood cultures. E The patient who fulfills three minor Duke criteria. 答案解說 (D) VSD closure occurs on the basis of adherence of the septal leaflet of the tricuspid valve to the defect, hypertrophy of the septal muscle, or ingrowth of fibrous tissue, not by the continuous growth of the septum. (B) Patients with mitral valve prolapse and an associated systolic murmur on examination are intermediate risk and warrant antibiotic prophylaxis before undergoing procedures that can result in bacteremia. Patients with incidentally detects mitral valve prolapse (e.g., by echocardiography) without an associated murmur on examination are considered to be at very low risk for infective endocarditis and do not require antibiotic prophylaxis. (C) The degeneration rate is similar to porcine heterografts. (D) (A)Though helpful, the observation of vegetations by echocardiography is not mandatory to establish the diagnosis of endocarditis. In addition, while the sensitivity of transesophageal echocardiography to detect vegetation in suspected endocarditis is 82 to 94 percent, the sensitivity of transthoracic echocardiography is ＜65 percent. (B) S. aureus is a particular aggressive organism that results in rapid destruction of valve and peri-valvular tissue. Nonetheless, antibiotic therapy alone is often curative for native valve endocarditis caused by this organism. (C) Recent studies have found that vegetations ＞10mm in diameter have a greater risk of thromboembloism than smaller vegetations, but it has not been proved that early surgical intervention in patients with larger vegetations improved the long-term outcome. (E) Patients with endocarditis and intractable heart failure due to valve dysfunction have a 50-90% mortality rate when treated conservatively; the outcome is improved with early surgical intervention. (C) In patients with small VSDs are asymptomatic and are not at risk for Eisenmenger complex. In women with larger left to right shunts, LV failure may occur during pregnancy. Progressive pulmonary vascular disease is usually occurs at the end to the second or during the third decade of life, and prognosis is very poor when Eisenmenger complex occurs. (E) (A) S. aureus has a propensity to cause metastatic infections, including central nerve system (30-50% of patients). (C) Patients with right-sided IE have a better prognosis than those with left-sided. (D) Vancomycin should be reserved for patients who have methicillin-resistant S. aureus. (B) (A) Isolated VSD is more common in infants and children than in adolescents and adults. (C) Survival in unoperated patients with TOF is poor. Only 25% of patients reach the age of 10, and only 3% reach age 40. (D) Most adults with TOF are suitable candidate for repair. (E) The decreasing benefit with age for the surgical repair of pulmonary stenosis is independent of the use of ventriculotomy or outflow patches, but is attributed to long-standing pressure overload on right ventricle. (B) (A) An important cause of post-op ventricular dysfunction is peri-operative myocardial damage. (C) Although the risk of coronary bypass surgery performed at the time of valve surgery, the long-term benefits of bypass surgery outweigh the additional surgical risk. (D) Bioprosthetic valve failure is more common and occurs more rapidly in younger patients, in chronic heart failure, and in mitral position. (E) Echocardiography/Doppler is essential at the first post-op visit as a baseline for comparison at a later date, when valvular dysfunction may occur. (A) (B) Left heart failure. (C) The IE risk is lower after surgical correction. (D) VSDs that are still large at age of 6 months will undergo spontaneous closure in only 50% of cases. (E) Patients with VSDs between age of 5 and 10 years may still be candidates for surgical closure if a significant volume overload is present. (D) Please refer to the Duke criteria.