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有效期間：民國 92年10月01日 至 92年10月15日 止

    Case Discussion

<病案討論>

75歲男性，因一天之中斷斷續續發生胸悶、氣促、及冒冷汗數次，每次約十幾分鐘，期間雖有短暫緩解，但是仍持 續覺得不適，經家人堅持下，而送至某醫學中心的急診就診。病人有高血壓及高血糖病史，均無規則治療。病人抽煙 約三十年，一天一至二包。近年偶有胸悶，大多數跟運動或情緒激動有關，休息一下就會好，因此均無求診。這幾年 來病人運動耐受性漸漸變差，爬兩樓就要休息一下，偶爾會下肢輕微水腫。這週以來，病人亦有多次胸悶發作，但是 休息後均有改善，因此並不覺得需要去看醫生。

至急診時，測得的生命跡象如下：血壓105/54 mmHg，心跳每分鐘72下，呼吸每分鐘28下，神智清楚，但四肢稍冰冷。此時實驗室檢查顯示： CK/CK-MB 312/45 U/l，Glucose 293 mg/dl，Troponin I 20 ng/ml，WBC 13.1 K/ul，Hb 15 g/dl。在使用Aspirin、NTG、Heparin、Morphine後，胸痛逐漸緩解。

追問起來，病人並無法確定此次心絞痛發作之確切時間。心臟超音波顯示心臟略有擴大，前壁收縮不佳，LVEF只 有48%，並有apical aneurysm形成。之後病人接受核子醫學檢查（Tc-99m pyrophosphate 攝影, Fig 1 ），確定為anteroseptal wall之急性心肌梗塞。由於發作時間可能超過一日，於是未再接受血栓溶解治療或緊急心導管的檢查。病人在加護 病房接受藥物治療及密切觀察三天後，情況較為穩定，轉至普通病房。然而，病人在轉至普通病房2天後又出現一次 約三分鐘的胸悶氣促，含NTG舌下片有改善。於是醫生和病人及家屬討論，進行了心導管檢查。血管攝影顯示為proximal LAD 99% stenosis。於是病人先接受在proximal LAD的經皮冠狀動脈氣球擴張術及支架植入，術後恢復良好。之後順利出院，在門診追蹤治療。

<病案說明>

  1. 急性心肌梗塞的診斷：意指下列三種情形中，出現二種或三種成立即可診斷：
    1. 缺血性胸痛。
    2. 心電圖呈現序列性變化。
    3. 心肌酵素的上升及下降。
    在部分診斷欠明的病人，可以配合心臟超音波對於心壁運動狀況，及核子醫 學的檢查（Tl-201 perfusion scan，Tc-99m PYP infarct-avid scan）加以鑑別診斷，同時，亦可協助評估梗塞的面積。
  2. 心電圖的判讀：
    1. Inferior MI with R't side V1∼5 ST elevation: 表有 inferior MI 及RV infarction。
    2. Inferior MI with V1∼5 ST depression: 非單純reciprocal change，常表示LAD也有lesion。
    3. Anterior MI with Ⅱ, III, aVF的 ST normal或elevation: LAD灌流區域也包括 inferior wall。
    4. Anterior MI with Ⅱ, III, aVF的ST depression: 為單純reciprocal change。
    5. Inferior wall MI with V1∼5 ST elevation如何與anterior wall MI 鑑別診斷：前者其precordial ST max elevation在V1，與anterior MI之max ST elevation在V2或V3不同。
    6. LBBB,WPW syndrome, pacing或previous MI的case發生AMI, EKG不一定有變化。但New onset之LBBB仍 視作acute MI。
  3. Tc99m pyrophosphate 攝影可於病人發生心肌梗塞大於24小時，但仍在七天之內使用（class IIa）。如病人求診時，胸痛發生大於24小時，而心肌酵素已經恢復正常；或是當症狀或心肌酵素均疑似心肌梗塞， 惟位置不明確時。出現≧grade 2的uptake具臨床意義。但CK<1000 U/L的病人，往往無法確定的結論。

    形狀

    與 sternum 關係

    判 讀

    圓圈形

    不管何角度皆貼著 sternum

    Anterior MI

    扁盤形

     隨著角度改變會離開 sternum 　

    Inferior MI

  4. 治療：在ACC/AHA Guideline中，Class I 指確定有益之適應症；II 指使用之效果仍有部分爭議；IIa指證據較偏向有效，IIb指有效之證據較不明確；III指該處置無效，甚至可能有害。
    1. 急性心肌梗塞首重區別ST-elevation MI或Non-ST elevation MI（包括unstable angina），這將決定是否應 早期接受血管再通術，包括血栓溶解療法，經皮冠狀動脈氣球擴張術甚或冠狀動脈繞道手術。
    2. ST-elevation（包括BBB）MI：所謂ST-elevation指ST segment上升大於0.1mv，出現於連貫的二個或二個以上 的導程。這類病人對於
      血栓溶解治療法的適應性包括有：
      • I：急性心肌梗塞發生12小時內，75歲以下。
      • IIa：75歲以上。
      • IIb：急性心肌梗塞發生12-24小時內；或高危險群併收縮壓大於180mmHg，或舒張壓大於110 mmHg。
      • III：發生時間大於24小時，心肌缺氧症狀已解除，及ST-depression MI。

      而經皮冠狀動脈氣球擴張術之適應症包括：
      • I：在ST-elevation（或LBBB）發生12小時內，或大於12小時，但症狀持續。或心肌梗塞發生36小時內， 出現心因性休克，且在心因性休克出現18小時內能進行手術者。
      • IIa：病人有血栓療法的禁忌症。
      • IIb：Non-ST elevation MI中，梗塞相關血管血流低於TIMI grade II，可以在症狀出現12小時內行之。
      • III：包括在急性期同時擴張非梗塞相關血管；病人症狀發生大於12小時，且無症狀；已接受血栓溶 解治療，且無症狀；以及在不合適的醫院進行此手術。
    3. GP IIb/IIIa receptor是血小板凝結過程中的最重要的步驟，研究顯示GP IIb/IIIa receptor inhibitors和aspirin、heparin合用，在死亡率、心肌梗塞發生率及需revascularization的比率均下降。 而Heparin/low molecule heparin則無論有無接受reperfusion therapy，均應至少使用48小時。 Heparin和Anti-Thrombin III結合後，會對Thrombin、Factor Xa去活化。而LMWH則抑制Factor Xa，可皮下注射，且Bioavailability高，出血、血小板減少症之副作用較少，且不必監測aPTT。 不同的LMWH的anti-Xa：anti-IIa比率亦不同，故臨床上使用仍有差別。
  5. AMI之急性併發症包括：
    1. 左心室功能失調 (LV dysfunction) 或心因性休克 (cardiogenic shock)： 心因性休克：代表廣泛性的左心室功能失調 (LV mass至少loss 40％以上) 或機械性缺陷 (mechanical defect，如VSD，cardiac rupture，papillary muscle dysfunction)或extensive RV infarction。
    2. 心律不整：AMI發生後4小時之內有VPC者高達93%，其中大約20%是VT或VF，各種atrial arrhythmia也在90%以上。
    3. 梗塞後心絞痛：處理與unstable angina相同，若藥物效果不彰時，應考慮IABP、PTCA或CABG。 其它較輕微的急性併發症，如心包膜炎(pericarditis)，因出現時間不同分成二種：
      1. early pericarditis：AMI 之後4天內，很少持續超過2∼3天；躺著或深吸氣會加重胸痛；
      2. Dressler's syndrome：時間約在2週∼2個月後發生，甚至到2年後； 特徵有malaise、fever、pericardial rub，WBC↑, ESR↑等。兩者治療均以Aspirin為首選， 其它NSAID或steroid (但可能增加cardiac rupture機會，宜小心使用)。而二者皆與死亡率無關。
  6. 出院前規劃：目前的心肌梗塞的準則中，相當強調心臟催迫性檢查（stress test）在預測急性心肌梗塞預 後的重要性（class I）。所謂的催迫性檢查可包括利用運動或藥物等方式。目前仍建議在5至7日後接受低度 的運動心電圖（Submaximal exercise stress）作為出院前的風險評估標準。有一研究顯示，在首次急性無 併發症的心肌梗塞後（二至四天），早期利用dipyridamole 或adenosine等血管擴張劑所做的催迫性檢查， 仍是相當安全的。若無心肌缺氧現象，提前出院也是安全的。對於急性心肌梗塞而言，預後和梗塞而壞死的 心肌有直接的相關性。在心肌灌流攝影（如Tl-201 or Tc-99m sestamibi myocardial perfusion imaging），不可逆的灌流缺損，被視之為壞死的心肌（其中包括急性期的心肌梗塞及陳舊性的心肌梗塞）。 由於在急性期時有部份stunned但仍未壞死的心肌，在一般超音波檢查中心室壁運動也會不正常，因此，在心 肌梗塞急性期的左心室收縮分率（LVEF）及心室壁運動（regional wall motion abnormality）等，都無法 正確評估心肌梗塞之範圍，而心肌灌流攝影就較無此問題。在心肌梗塞病 人出院前的左心室收縮分率，則和 心肌灌流攝影中不可逆的灌流缺損，有很好的相關性。相關研究同時顯示， 在接受血栓溶解的治療後，心臟血流攝影的灌流缺損和長期的存活有關。

繼續教育考題
1.
(A)		 True statements regarding to the clinical history of acute myocardial infarction (MI) include all of the following EXCEPT: 
AA clear precipitating factor or prodromal symptoms can be identified in 90 percent of patients with acute MI.
BBetween 20 to 60 percent of nonfatal MI are unrecognized by the patient and are identified only by a subsequent routine ECG.
COne third of patients with a prodrome have had symptoms for 1 to 4 weeks before hospitalization.
DOver one half of patients with a transmural MI have nausea and vomiting.
EThe peak frequency of MI onset is between 6AM and noon.
2.
(E)		 Each of the following statements regarding an antithrombotic therapies in the treatment of unstable angina is correct EXCEPT: 
A Aspirin reduces the incidence of cardiovascular death and nonfatal MI.
B The combination of aspirin and unfractionated heparin is superior to aspirin alone in prevention of death and nonfatal MI.
CGlycoprotein IIb/IIIa inhibitors decrease the incidence of death, nonfatal MI, and recurrent ischemia at 30 days. 
DAcute treatment with the low-molecular-weight heparin (LMWH) enoxaparin has been shown to be superior to unfractionated heparin in reducing the rate of death, nonfatal MI, and recurrent ischemia.
EProlonged administration of LMWH after hospital discharge reduces the rate of recurrent ischemic events.
3.
(A)		 True statements regarding to the indication of Tc-99m pyrophosphate infarct scan in acute MI include all of the following EXCEPT: 
AHigh sensitivity and low specificity in the detection of acute MI.
B Not routinely use, and suggested in the unable to differentiate acute MI or its location by the clinical history, ECG, and serum markers.
CUsed in 2 to 7 days after acute MI.
DThe sensitivity depends on the extent of MI and duration after the event.
4.
(A)		 All of the following features of post-myocardial infarction pericarditis are true EXCEPT:
AThrombolytic therapy increases the incidence of early post-MI pericarditis and reduces that of  Dressler's syndrome.
BPost-MI pericarditis is more common following Q wave MI.
CA pericardial friction rub can be detected as early as 12 hours after the infarction.
DThe use of heparin is not associated with an increased risk of pericarditis.
EDiagnostic ECG changes include persistently positive T waves and premature normalization of initially inverted T waves.
5.
(C)		 True statements about acute MI include all of the following EXCEPT:
AMarked hypotension in response to small doses of NTG in patients with inferior infarction suggests right ventricular infarction.
BST segment elevation in lead V4R is a sensitive and specific sign of RVI.
CLess than half of deaths caused by acute MI occur during hours 2 to 4 after the beginning of the event.
DMost deaths among patients hospitalized with acute MI are attributable to LV failure and shock.
E Careful monitoring of cardiac rhythm and treatment of primary arrhythmias has reduced the incidence of in-hospital death from acute MI.
6.
(C)		 True statements regarding thrombolytic therapy in acute MI include all of the following EXCEPT: 
AThrombolytic therapy reduces the mortality of ST-segment elevation MI by 15 to 20 percent at 1 month.
BCompared with patients with anterior ST elevation, patients who present with a bundle-branch block have a similar risk reduction with thrombolytic therapy.
CCompared with patients with anterior ST elevation, patients with inferior ST elevation have a greater risk reduction.
DClinical trial data demonstrate no mortality benefit of thrombolysis administered more than 12 hours after the onset of symptoms.
EPatients older than 75 years experience an absolute reduction of mortality similar to that of patients younger than 55 years.
7.
(A)		 Which is the true statement regarding to stent implantation?
AStent implantation decreases the restenosis rate.
BStent implantation inhibits neointimal proliferation.
CStent implantation decreases the rate of non-Q wave MI.
DStent implantation decreases the rate of Q wave MI.
EStent decreases the mortality rate when performed in the setting of acute MI.
8.
(B)		 Which of the following imaging techniques are capable of correctly identifying acutely necrotic myocardial tissue?
a. Tc-99m pyrophosphate scintigraphy.
b. Echocardiography.
c. Monoclonal antimyosin-specific antibody scintigraphy.
d. Coronary angiography.
e. Thallium-201 single photon emission computed tomography (SPECT).
Aa, b
B a, c
C a, c, e
Dd, e
Eall of the above 
9.
(C)		 All of the following statements regarding nuclear imaging are true EXCEPT:
AThe size of the resting myocardial perfusion defect after acute MI correlate with the patients' prognosis.
BIncreased lung uptake of thallium-201 at rest correlates with an unfavorable prognosis.
CSubmaximal exercise imaging prior to discharge from the hospital is a better predictor of late complications from the acute MI than adenosine or dipyridamole stress myocardial perfusion imaging.
DPatients who cannot perform exercise can be evaluated for coronary artery disease with vasodilating medications (such as dipyridamole or adenosine).
EDobutamine is an alternative pharmacological stress test agent for patients with contraindications to adenosine or dipyridamole.
10.
(A)		 All of the following characteristics of chest pain would be unusual for coronary artery ischemia-induced angina EXCEPT:  
APain that begins gradually and reaches maximum intensity over a periods of minutes.
BPain aggravated or precipitated by one deep breath.
CPain relieved within seconds by lying horizontally.
DPain localized to an area the size of the tip of the finger.
EPain relieved within a few seconds by one or tow sips of water.

答案解說

  1. (A) Up to one half of patients with acute MI have clear prodromal symptoms or an associated precipitant, including heavy exercise, anger, or mental stress. Nausea and vomiting presumably related to vagal stimulation. There is a clear circadian periodicity for the time of onset of acute MI, and the peak incidence of events occurring between 6 AM and noon. The observation may be related to circadian alterations in circulating catecholamines as well as increased platelet aggregability in he early morning.
  2. (E) LMWHs have been studied in the unstable angina and two trials, ESSENCE and TIMI 11B found the LMWH enoxaparin to be superior to unfractionated heparin at reducing rates of death, MI, and recurrent ischemia. However, other trials using different LMWHs have not shown a clear effect. Prolonged administration of LWMH after discharge has not been shown to be of benefit for most patients with unstable angina.
  3. (A) 當病史、心電圖及生化檢查無法鑑別是否有急性心肌梗塞(或定位)的狀況之下，Tc99m pyrophosphate 攝影（AHA/ACC class II a indication）可於病人發生心肌梗塞大於24小時至七天之內時使用。現在較少使用。專一性很高,但是敏感度受心肌梗塞範圍的大小及發生多久而定。
  4. (A) The use of thrombolytic therapy caused a 50 percent reduction in the incidence of early acute pericarditis after MI.
  5. (C)Fifty percent of deaths associated with acute MI occur within the first hour.
  6. (C)The relative risk reductions with thrombolytic therapy in patients with ant. MI and BBB were approximately 21 percent. Patients with inf. MI had less risk reduction.
  7. (A)Stents are very effective in preventing vascular recoil, but not decreased the rates of MI. After 6 months, angina, restenosis, and the need for target-lesion revascularization were less common in the stent group. The 6-mortality rates were not statistically different.
  8. (B)The only imaging methods currently available for the identification of acutely infarcted myocardial tissue are Tc-99m pyrophosphate and monoclonal antimyosin-specific antibody scintigraphy, but the poor spatial resolution limited the applicability in assessment of the infarct size.
  9. (C) Myocardial perfusion imaging with either thallium-201 or Tc-99m labeled compounds (e.g., sestamibi) is useful for the detection of myocardial ischemia and MI. Serial imaging can be helpful in determining the effectiveness of thrombolytic therapy, and measurement of infarct size by perfusion scintigraphy predicts subsequent ventricular remodeling. Nuclear imaging is also a useful modality for early risk stratification after an acute MI. The size of the resting perfusion defect correlates with prognosis. The increased lung uptake of thallium at rest was indicative of impaired LV function. Lastly, the dipyridamole stress testing on day 2 to 4 after acute MI is not only safe, but such testing predicts in-hospital and late cardiac complications better than submaximal exercise stress imaging. Myocardial perfusion imaging also provides important prognostic information in patients with chronic CAD. The combination of clinical and myocardial perfusion data is more predictive than the combination of clinical and cardiac catheterization data.
  10. (A)Differentiating the discomfort of noncardiac disorders from angina pectoris is possible when the quality of the pain, its duration, precipitating factors and associated symptoms are taken into consideration. For example, posture can affect the pain of myocardial ischemia, and it is often intensified by assuming the horizontal position and relieved by assuming the vertical position.

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