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Variability is the law of life

Posted by iskanbasal on March 21, 2009

Sir William Osler said, “Variability is the law of life, and as no two faces are the same, so no two bodies are alike, and no two individuals react alike and behave alike under the abnormal conditions which we know as disease.”

This statement is cited in the article about the new , precise definition of acute myocardial infarction which I already posted below. The authors Shaun Senter MD and Gary S. Francis MD describe the wide variety of presentation of myocardial infarction and explain the need to make precise diagnosis before taking action. I read the article and learned new things in this subject. When studying a certain condition on my textbooks I try to keep in mind the most important clinical features that describe it and make a single picture of the disease but I should also be aware to the variability of presentation of a pathological condition. It might be that this variability depends on the extent to which tissues and organs are involved in a certain disease  or to the way a patient’s organism responds depending on their age, sex or other factors; I’m not sure but this what I think could be. The autors review the current criteria that is established by international cardiovascular societies for making diagnosis of MI:

“The cornerstone of diagnosis remains a high level of clinical suspicion, serial ECGs, and troponine” they say. Particulary the focus on the role of troponine. There is also a clinical classification of MI in five different types.

Read the article here.

Recently I studied some chapters on the Jacques Wallach Interpretation of diagnostic tests, 8th ed and I found very good tables for the interpretation  of biomarkers in this context, one about the characteristics of serum markers for MI is this :

Early appearance: Myoglobin, CK isoforms, glycogen phosphorylase isoenzyme BB, heart fatty acid-binding protein
High specificity: cTnI, cTnT, CK-MB, CK isoforms
Wide diagnostic window: cTnT, cTnI, LD, myosin hight and heavy chains
Risk stratification: cTnT, cTnI, CK-MB
Predicts reperfusion: Myoglobin, cTnI, cTnT, CK isoforms
Indicates reinfarction after 2–4 d: CK-MB

The Wallach’s textbook confirm the possibility of false-positive ECG in >10% to 20% of AMI cases in the ED and nondiagnostic in about 50%. But here there is an additional note about newer biomarkers being studied as independent predictors of cardiac risk which I did not know before such as The ischemia-modified albumin and others.

I’d like, here below, to summarize  only the clinical features of MI which describe the clinical variability of the condition cited in the article  above:

.

  • the presentation of myocardial infarction varies from 25% of patients with no symptoms to patients with severe, crushing chest pain.
  • Discomfort may occur in the upper back, neck, jaw, teeth, arms, wrist, and epigastrium and it build up in a crescendo manner. It can lessen in the standing position. A pressure sensation, air hunger, or gas “building up” can be described.
  • Shortness of breath, diaphoresis, nausea, vomiting and even syncope may occur.
  • The only symptoms may be shortness of breath and diaphoresis
  • symptoms last from minutes to hours and can be releived by sublingual nitroglycerin.
  • Atypical presentaion or less prominent symptoms may make the diagnosis difficult in the elderly and in patients with diabetes, and in women.
  • On physical exam the patient may appear pale and diaphoretic and the skin cool. Heart sounds are soft and a fourth heart sound may be audible. BP may be low and tachycardia and pulmonary edema are poor diagnostic features.
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