Simplification vs. Over Simplification

Since ECG instructors teach students at many different levels, it is sometimes necessary to simplify or even over-simplify some materials.  Occasionally, instructors even accidentally or purposely tell students incorrect information. This might help the student memorize criteria in the short term, but it can make it difficult to learn the correct information later.  An example that comes to mind is something I was taught a long time ago:  "all tachycardias with narrow QRS complexes and P waves where the rate is less than 150 are sinus tach, and all narrow complex tachycardias over 150 are atrial tach (or SVT)".  Now, I only have to jog about three quarters of a mile to disprove that one!  I'm sure I do not develop a dysrhythmia when I run, although I do wish I were in better shape!

Left Bundle Branch Block and Acute M.I.

Left bundle branch block and right ventricular pacing are two causes of wide QRS complex, and the resulting ST changes can make it very difficult to determine if there is acute ST elevation M.I. (STEMI).  Leads with negative QRS complexes have ST elevation in LBBB and RV pacing, often leading the novice to mistakenly diagnosis acute M.I., especially septal M.I., since Leads V1 and V2 are normally negative and have ST elevation.  Because of this, most EMS agencies and many hospital emergency departments consider the ECG with LBBB to be unfit for diagnosis of the acute M.I.   Sgarbossa et al, in 1996, published in the New England Journal of Medicine their research findings regarding ECG signs of acute M.I. in the setting of LBBB.  Their criteria for diagnosing acute MI in LBBB are now considered the gold standard. In spite of this, many people are unaware of their criteria.   Refer to the ECG on this site called, "Left Bundle Branch Block and Acute Inferior Wall M.I.", which is this week's ECG of the Week.

Since I primarily teach people who work in EMS and hospitals, I am compelled by their protocols to teach that they may not declare a "Cardiac Alert" on patients with LBBB or RV pacing. The exception is if the "left bundle branch block is new-onset". Really - rarely does a patient know if their LBBB is new!

Since new-onset LBBB is very dangerous to the patient with acute M.I., and ALL acute M.I.s are dangerous, we really would not want to miss the diagnosis of AMI just because a wide complex is present.  I have been teaching my EMS students that they must follow their prevailing protocols, but should send EVERY chest pain patients' ECGs to the hospital while they are enroute.  Fortunately, in my community, this technology is almost universal.  It is my hope that the hospital physician will pick up an M.I. and inform the paramedics that this is, indeed a "Cardiac Alert".  We are additionally fortunate in my community that nearly every hospital has an interventional cath lab.   I wonder what is happening in locations that do not have this luxury? 

Advanced Training

If you teach basic students, try to teach the abbreviated material with an eye on the future - don't give them incorrect information, just simplified information.  If you teach advanced students, give them access to the latest research and varying viewpoints.  Here are some links regarding LBBB and acute M.I.:  Sgarbossa EB et al:  Barold, Herweg; ECG Library; Life in the Fast Lane; The Heart.org, and EMEDU.