"The world is full of magic things patiently waiting for our senses to grow sharper"
- William Butler Yeats
I once overheard a group of cardiologists razzing a group of surgeons about their EKG knowledge (or lack thereof): "Their policy is, if there's more than two lines on the automated readout, consult cardiology". They all laughed as they recalled their history of less-than-compelling EKG queries from the surgeons. Because of their expertise, what they failed to realize is that we internists can also have holes in our EKG knowledge, or at least temporary EKG absent-mindedness in certain moments of terror. To clarify (or..umm...maybe relearn) some of these common EKG enigmas I spoke with world-renowned interventional cardiologist and creator of the handy-dandy hand model of cardiac vasculature, Dr. Morton Kern. Here are his 5 useful EKG tips for the absent-minded internist.
1. Never forget the standardization. It's extremely simple and quite basic but, according to Dr. Kern, is commonly overlooked by internists. This is the square wave at the beginning of each EKG. The vast majority of the time it is 10mm tall but if it's taller or shorter and you forget to check you can easily miss high or low voltage.
2. The leads all track the same heart. Poetic, I know, but oh so true! Think of a time when you spotted a missing QRS, peaked T-wave, or even an ST elevation...but only in that one weird lead. Dr. Kern urges internists to remember that, "all the beats vertically are the same beat. If you look at lead I then II then III then your rhythm strip, every beat is the same beat in time. Even though the configurations change they're all lined up. So if there is a QRS missing in lead II on that one beat you can compare to the other leads during the same beat and see if it's consistent." If it's not, it's usually not significant.
3. There's more to R-wave progression than meets the eye. "You should see evidence of the ventricular depolarization spike growing larger as the leads move anatomically from right to left closer to the left ventricle" says Kern. One of the more common diagnoses we might associate with abnormal R-wave progression is an old anterior wall infarct with scarred muscle that isn't generating voltage. But have you ever seen the R-wave get smaller as you go from V1 to V6? That could represent dextrocardia and your next move should be to "listen to the guy's chest and see where the heartbeat is"! Other times the actual position of the heart may be shifted depending on what anatomical abnormalities the patient may have. Even LVH can cause abnormal R-wave progression due to the heart being shifted more laterally.
4. Normal EKGs are misleading more often than abnormal EKGs. "An abnormal EKG almost always corresponds with coronary artery disease", but in his kingdom, also known as the cath lab, Dr. Kern has seen plenty of patients with normal EKGs also have significant coronary artery disease. He adds that if a patient has truly severe chest pain and a normal EKG it is highly unlikely that they have CAD but likely have another life-threatening cause of chest pain such as aortic dissection. According to Kern, "If you have true myocardial ischemia YOU WILL HAVE EKG CHANGES." He also notes that those patterns of ischemic changes that we all learned in medical school such as "leads II, III, and aVF correspond with inferior wall infarct" are not the slam dunk we always thought they were. "Ischemic changes in contiguous leads do usually represent disease" he assured, "but not necessarily in that territory".
5. If you're concerned for MI get another EKG now. It's 6:45 pm on a long-call day and you're the only admitting team. You get a call from the ED for an admission for ACS rule out. The ED has already discussed the patient with the cardiology fellow, which makes you feel like the case is closed. "I'm just here to write the note", you think. "Heck yes, it's an easy admission", you think. But then you see the patient and you get a sinking feeling in your gut: "Hmm, he's kinda sweaty, breathing a bit heavily. Oh, you say your chest pain is substernal, pressure like, and came on when you started mowing the lawn today?". The first troponin and EKG were stone cold normal. What would you do? Order the next set of EKG and enzymes for 6 hours later? Dr. Kern says NO. Even if the last EKG was 20 minutes ago get another EKG immediately. If you're concerned for myocardial ischemia the EKG will be dynamic and can start changing quickly. Says Kern, "It's not a crime to get a cardiac cath and have a negative result but it is a crime to ignore it and find out 6 hours later that it was a heart attack".
Do not be intimidated by EKGs. Above all Dr. Kern emphasizes that EKGs are not as difficult to interpret as it might feel sometimes. If you learn a few simple tricks they can be applied in countless scenarios. When all else fails, Kern can confirm that the automated EKG reading is accurate 90% of the time. Not that we'll need it.
And last but not least: it wasn't easy, but when I gave him no choice but to choose ONE, Dr. Kern said that the cardiology guideline that all internists must know inside and out is the 2014 AHA/ACC Guideline for the Management of Patients With Non–ST-Elevation Acute Coronary Syndromes.