What does someone having a heart attack look like? I think the New York Times captured what many of us probably have in mind, when they published this picture as part of a recent series on advances in cardiovascular care:
Here is the iconic middle-aged guy, in extremis, pointing to his chest, with a team of health care professionals at the bedside. There are also signs of initial management: He has ECG electrodes on his chest, an IV in his left arm, what looks like monitor/defibrillator pads on his right chest and below his left arm and, of course, an oxygen mask.
What is wrong with this picture?
Well, a recent study from Circulation suggests that the oxygen mask may be doing more harm than good. Australian investigators randomized over 600 patients with suspected ST-segment elevation myocardial infarctions diagnosed by paramedics in the field to get either standard pre-hospital oxygen supplementation (8 L/min via face mask) or no oxygen supplementation. Among the 441 with confirmed STEMI, those who received the O2 had larger infarcts, as measured by cardiac enzyme release and follow-up cardiac MR scans. They also had a higher incidence of recurrent infarction and cardiac arrhythmia. The study was too small to detect differences in mortality or other clinical endpoints.
An accompanying editorial points out the practice guidelines for MI care, developed by the American Heart Association and American College of Cardiology, have downgraded the recommendation for supplemental O2 over several revisions, citing a lack of credible evidence to support its use. The current guidelines (2013) make no recommendation.
I think there are a couple of important lessons here:
• Even the most “sensible” treatments need to be put to the test to see if they really work. Just to continue with the MI theme, it wasn't that long ago that we routinely treated all STEMI patients lidocaine, then kept them in bed for weeks while we tried to suppress their post-MI PVCs with quinidine. All of those practices made compete sense, and all were later shown to be more harmful than helpful.
• Practice guidelines should be very “humble” about what they recommend, especially in an age when adherence to “standards” is used to assess the quality of care. Guideline developers should stick to making their recommendations on the basis of good evidence, and should, as in this case, revisit even the most tried and true recommendations as they raise the bar on quality of evidence and new information becomes available.
What do you think?