什么情况下胸痛不是心脏病发作?

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When Is a Heart Attack Not a Heart Attack?

By LISA SANDERS, M.D.
Published: March 16, 2008

1. Symptoms

“I don’t think he had a heart attack,” the patient’s wife declared emphatically. “I don’t care what the doctor in the hospital said.” The patient nodded his agreement. “But we need to be sure,” she added in a distinctive Long Island accent. That’s why they had gone to see Dr. Bruce Decter in New Hyde Park, N.Y., a cardiologist just out of training — to get a second opinion from someone a little closer to the books. The patient, a lanky 42-year-old man with a chiseled jaw, retreating hairline and skinny ponytail, seemed tired and anxious and grateful to have his childhood sweetheart do all the talking.

He had chest pain off and on for most of his adult life. His internist didn’t think it was his heart, and a normal stress test done the previous year seemed to confirm that. Then the week before his visit to Decter, his chest began to hurt while making love. It spread to his left shoulder and arm. And it didn’t go away. He hardly slept at all that night because of the pain and a gnawing anxiety that this time it really was a heart attack.

First thing the next morning he went to his internist. An EKG was normal, but the patient was so worried that his doctor arranged for him to see a cardiologist that afternoon. By then the patient was pale, sweaty and shaking. “I think you’re having a heart attack,” the cardiologist told the patient and then sent him straight to the E.R. The EKG done in the hospital was normal, but a series of blood tests indicated that he was having a heart attack, and a big one. He was rushed to the cardiac catheterization lab to see if the clogged vessel could be reopened. To the doctors’ utter amazement, there was no blockage; his heart looked fine.

Still, the cardiologist was certain that the patient had some kind of heart problem. As he explained it, there was either a blockage that reopened on its own, or he had a spasm in one of the coronary arteries. In either case, the patient was lucky that his heart hadn’t been permanently damaged. The cardiologist started the patient on a beta blocker — a medication that has been shown to protect the heart. But the chest pain kept coming.

2. Investigation

At his office, a week after the trip to the E.R., Decter examined the patient, a fit middle-aged man. His blood pressure was perfect. His heart rate was regular and slow. In fact, his entire exam was completely normal. He got another EKG. Also normal. The patient’s blood tests from the E.R. seemed to indicate that he had had a heart attack, but none of the EKGs or the angiogram revealed any abnormality.

The problem for Decter was one that doctors face regularly: how to reconcile tests that contradict one another. Often patients, and even doctors, think that test results provide a definitive answer — like the solution in today’s paper to yesterday’s crossword. But every test carries a risk of being wrong, and all tests need to be interpreted. This is never clearer than when different tests seem to tell different stories. Could these apparently contradictory results be shaped into a single narrative that made sense?

The blood test in question measures an enzyme that is released when a muscle like the heart is injured. That enzyme, creatine phosphokinase, abbreviated as CPK, was normal when the patient first presented to the emergency room but rose to a level 20 times higher than normal over the next several hours. In a patient who has chest pain that comes on with exertion, an elevated CPK usually means that the patient is having a heart attack.

But damage to any muscle will cause CPK to increase, so there is an additional test that can determine whether the enzymes are leaked from a damaged heart or from damaged skeletal muscle. When Decter called the lab for results of this test, he found that the CPK hadn’t come from the heart; it had come from the muscles of the arms and legs. “You’re right,” Decter told the anxious patient. “You didn’t have a heart attack.” But at this point, the young cardiologist acknowledged, he wasn’t at all sure what the patient did have.

The patient considered himself pretty healthy, he told the doctor. He took no medicine, had never smoked and exercised daily. In fact, the only other time he’d ever been in the hospital was when he was 21 and had mononucleosis. His urine then was really dark — “the color of Coca-Cola” — and the doctors were worried.

When Decter heard that, something stirred in his memory. Cola-colored urine. Perhaps this was the key. Had he had this kind of dark urine since then? he asked. The patient told him that a couple of times a month his urine would turn brown and he’d feel achy all over. It happened whenever he was sick or tired or when he exercised too hard. He’d told lots of doctors about it, but none of them could figure out what was going on.

Decter knew he was on to something. Urine that dark is usually caused by muscle breakdown. When muscle cells are damaged, they leak CPK, but they also spill several other chemicals. One of them, the compound that gives skeletal muscle its distinctive deep red hue, can turn urine a dark brown. Were the brown urine and the elevated CPK caused by the same problem? Were they both signs of some longstanding disease process that was destroying this patient’s muscle?

Decter sent his patient to Dr. Alfred E. Slonim, a pediatric endocrinologist by training who spent his career investigating diseases of the muscle. The patient called Decter after seeing the specialist, almost speechless with excitement. Slonim spent more than an hour with him and his wife, getting the history of his strange illness. “Tell him about what happens on Yom Kippur,” his wife prompted near the end of the interview. Every year on the Jewish day of atonement, the patient would fast for a day, from sunset to sunset. And every year, he would spend the day after Yom Kippur in bed, crippled by an aching in his muscles and passing dark brown urine. Once he said that, Slonim had the diagnosis: the patient had a form of the genetic disease known as carnitine palmitoyltransferase deficiency or CPT.

3. Resolution

In this rare genetic disease, patients are missing the necessary biological equipment to burn fat for energy. Normally the body uses a type of sugar provided by the diet or stored in the liver to keep the body running. When that sugar is used up, the body switches to fat for fuel. Patients with CPT can’t do that. Instead, when they run out of sugar, their bodies are forced to turn to the second backup form of energy: muscle. When this patient’s body depleted the normal fuel — because of decreased intake (fasting or illness) or increased metabolic activity (exercise or fever) — it had to turn to the energy stored in muscle just to keep the biological motor running.

This diagnosis finally allowed the patient and Decter to make sense of the original story. The CPT gave the patient terrible, chronic heartburn; the delicate tissue of the esophagus, when injured, can cause a pain that feels to many patients very much like the classic presentation of a heart attack. Certainly this patient thought he was having one the night he had sex. He didn’t sleep and didn’t eat all the next day when he was in the E.R., and that is what triggered the attack on his muscles and elevated his CPK numbers. “It’s incredible that it took a wrong diagnosis to get to the right one,” the patient told me. There’s no cure for this disease, but frequent meals can help ward off many attacks.

As for Decter, he says he doesn’t believe that this disease is quite as rare as he was told in medical school. Over the past decade, he has seen four patients with unexplained elevations in their CPKs and no evidence of heart disease. Two have tested positive for CPT-like genetic disorders. He’s still trying to figure out the other two.

http://www.nytimes.com/2008/03/1 ... lth&oref=slogin
1.症状
患者的妻子强调说:”我并不认为他是心脏病发作, 对医生说的我不在乎” . 患者也点头同意. 妻子又以一种有特色的长岛口音补充说:”但是我们必须弄清楚到底是什么病”. 这也是他们为什么去新海德公园看Bruce Decte医生的原因, 他们想得到另外的接近于他们所认为的诊疗意见, 这名医生刚刚接受完培训. 这是一名42岁的瘦长的男性患者, 有着轮廓清晰的下巴, 发际线靠上, 留着马尾巴, 似乎有点疲劳和焦虑, 对他青梅竹马的爱人所说的很感激.
在他的大多数成年生活中都会有偶尔的胸痛. 他的内科医生并不认为他的心脏有病, 前一年做的运动试验正常也似乎证实了这一点. 然后在他去看Bruce Decte医生的前一个星期, 他做爱时胸痛又发作了, 并且放射到他的左肩和手臂. 而且胸痛一直不消失, 由于胸痛和苦恼的焦虑, 他整晚未睡, 并认为这次真的时心脏病发作了.
第二天早上的第一件事就是去看他的内科医生. 心电图是正常的, 但是患者很担心, 于是医生安排他下午去看一个心脏病专家. 那时患者脸色苍白, 浑身是汗, 并且颤抖. 医生认为他是心梗了, 并且直接把他送往急诊室, 心电图也是正常的, 但是一系列的血液检查表明患者发生了心梗, 而且很严重. 他很快被送往导管室, 看看还有没有可能把阻塞的血管再通. 完全出乎医生意料的是血管没有阻塞, 他的心脏看起来很好.
这位心脏病专家依然肯定患者有某种心脏病. 他的解释是要么冠脉血管有阻塞并且自己再通了, 要么冠脉血管的某一支发生痉挛. 不管是哪一种情况, 病人都是幸运的, 因为他的心脏没有发生永久性的损害. 这位心脏病专家让患者开始服用一种倍他受体阻断剂—一种可以保护心脏的药物. 但是胸痛依然发生.
2.研究
在患者去急诊室后的一个星期后, Decter医生在他的办公室给患者做了检查, 一个形体中等的中年男性. 他的血压是完美的, 心律是规则的, 心跳慢. 事实上他的整个检查结果都是完全正常的. 他做了另外一个心电图, 也是正常的. 虽然他在急诊室的血液检查似乎表明他有心梗, 但无论是心电图还是冠脉造影都没有任何异常.
Decter医生所遇到的问题也是医生们经常遇到的一个: 如何使矛盾的检查结果统一起来. 患者经常(甚至是医生)认为检查结果提供一个明确的答案—就像今天的报纸提供的昨天报纸上迷题的答案一样. 但是每项检查都会有一定的错误风险, 并且所有的检查都需要解释. 当不同的检查出现不一致的检查结果时, 疾病不易明确诊断. 从这些明显矛盾的结果中能否提炼出一个合理的解释呢?
而在讨论的这个血液检查测的是一种酶, 它在肌肉(比如心肌)受损时释放出来. 这种酶是肌酸磷酸激酶(CPK), 在患者刚送往急诊室时是正常的, 但在接下来的几个小时内升高到正常水平的20倍以上. 在劳力后发生胸痛的患者, 升高的CPK往往意味着患者发生了心梗.
但是任何肌肉的损伤均可导致CPK升高, 因此必须做进一步检查来判断它到底是心肌损伤还是骨骼肌损伤后释放出来的. 当Decter医生打电话去实验室问检查结果后, 他发现CPK并不是从心肌释放出来的, 而是手臂和腿释放出来的. 于是Decter医生对焦虑的患者说:”你是对的, 你并没有发生心梗.” 但在这点上, 这位年轻的心脏病专家承认他完全不清楚患者到底患的是什么病.
患者告诉这位医生他认为自己非常健康, 没吃过什么药, 从不吸烟, 每天锻炼. 实际上, 唯一的另外一次住院还是他21岁时患单核细胞增多症的时候. 然后他的尿液真的变黑了—“可口可乐的颜色”—医生也很担心.
当Decter医生听到这时, 一些东西在他的脑海里浮动. 可乐颜色的尿液, 也许这就是答案. 他问了患者从那次后是否还有过黑色的尿液, 患者告诉他每个月有几次尿液会变棕色, 并且感觉浑身痛. 他向很多医生诉说了此症状, 但他们中没有人能解释它.
Decter知道他察觉到了什么, 尿液黑色通常是肌肉破坏后导致的, 当肌细胞损害后会释放CPK, 但它们也会释放出其它一些物质, 其中的一种就能使尿液变成棕黑色, 这种复合物就是使骨骼肌呈现特有的深红色的物质. 患者棕色的尿液和升高的CPK也是同样的问题所致吗? 它们是某种破坏患者肌肉的长期疾病过程的两种特征吗?
于是Decter将患者送往Alfred E. Slonim医生那里, 一个职业生涯从事肌肉研究的儿科内分泌专家. 当患者看了这位专家后, 给Decter医生打电话, 几乎兴奋得说不出话来. Slonim医生和患者及其妻子在一起待了一个多小时, 获得这种奇怪疾病的病史. 在会诊临近结束时, 患者的妻子突然站起来:”快告诉医生犹太人赎罪日发生了什么.” 每年每逢犹太人的赎罪日, 患者都禁食一天, 从日落到日落, 此后他会
由于肌肉疼痛而行动不便, 只能一整天待在床上, 并且伴有棕色的尿液. 一旦他说了这些, Slonim就给出了诊断: 肉毒碱棕榈酰基转移酶缺乏(CPT)—患者所患的是一种遗传疾病.
3. 治疗
对于这种罕见的遗传疾病, 患者丢失了燃烧脂肪所必须的生物工具. 正常情况下, 机体利用从食物中摄取的或者储存在肝脏中一种糖来供给能量. 当糖耗尽时, 机体就开始转而利用脂肪来提供能量. 而患有CPT的病人则不能利用. 相反, 当他们耗尽糖时, 他们的机体被迫转向第二个能量备用形式:肌肉. 当这名患者耗尽了常规能量—由于摄入减少(节食或疾病)或者增加的代谢活动(运动或发烧)—机体不得不靠储存在肌肉里面的能量来保持生物机体的运转.
这个诊断最终也允许患者和Decter将他们的故事变得有意义. CPT给患者带来了可怕的慢性的胸痛; 而食道受损后所致的胸痛对于许多病人来说与典型的心绞痛非常相似. 这名患者也肯定地认为他那天晚上做爱时发生了心梗. 他第二天在急诊室时整天没吃没睡, 这也触发了肌肉的破坏和CPK的升高. 患者告诉我说:”真是难以置信, 要从一个错误的诊断中来得出正确的诊断.” 而这种疾病无药可治疗, 但频繁的进食能防止发作.
至于Decter, 他说他不相信这种疾病如他在医学院被告知的那么少见. 在过去的十年中, 他已经见到四例患者有不能解释的CPK升高,而且也没有任何心脏病的证据. 其中2例CPT类似的遗传疾病阳性. 他仍然在努力研究另外两例的原因.