Friday, April 17, 2009

Unrecognized (Silent) Non-Q-Wave Myocardial Infarction...

Just being able to say that will make you sound real smart with your friends and co-workers. You remember that myocardial infarction (MI) refers to death of the heart muscle due to interrupted or impaired blood flow to the myocardium. What about Q-waves? Recall the ECG, with the P-wave, QRS complex, and T wave... the Q portion of the QRS is normally a very small downward blip just prior to the large, prominent R peak. Anyway, large and evident Q waves are used to detect a previous MI. Other ECG abnormalities (ST changes) can suggest an acute MI or MI that is currently happening. These Q waves though show old infarctions. Believe it or not, some patients have an MI and never even notice it and may not report problems to their doctors. This is considered a "silent" or unrecognized MI... later these silent myocardial infarctions can become evident as large Q waves in the ECG. Okay, okay, we are getting to the unrecognized Non-Q-Wave Myocardial Infarction part. So consider if your patient has had one of these silent MI's BUT say they don't ever develop the abnormally large Q waves? How would you know they had a silent heart attack? You wouldn't know, right? Well, some clever scientists recently reported their use of MRI's to detect these "Unrecognized Non-Q-Wave Myocardial Infarctions." You should be feeling pretty smart by now. What is the importance of all this? As posted at PLoS Medicine, here are some possible implications of this study (summary link; article link):

  • Silent or unrecognized MI's are not being detected in patients with heart disease, since they don't always have Q waves on their ECG
  • Using MRI to detect these silent MI's showed that 70% of silent MI patients lacked Q waves whereas only 30% of patients with silent MI had Q waves
  • It seems that in silent MI (which are often small) the use of Q waves is going to miss a significant portion of patients with silent MI.
  • Non-Q-wave MI is important because it is significantly associated with increased mortality. So we would want to be able to identify these patients.

~ ~ BIO26 ~ ~

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