The Art of ECG Interpretation: Online Tools for Learning

If you have difficulty reading ECGs, you may want to try visiting the Prehospital 12 Lead ECG blog (https://ems12lead.blogspot.com/), a great resource on cardiac rhythm analysis. In this interview, we speak with creator Tom Bouthillet about his tips on ECG interpretation. What were your reasons for starting the website? When and why was it launched? I started the Prehospital 12 Lead ECG blog in October of 2008. I had been teaching acute coronary syndromes and 12-lead ECG interpretation in various UMBC-affiliated Critical Care Transport (CCEMT-P) programs around the country, and was struck by the fact that there is a real need for enhanced education in this area. Particularly with the success of the D2B Alliance, the advent of the AHA’s Mission: Lifeline, and the development of regional STEMI systems around the country, there is unprecedented attention being given to door-to-balloon times, so it’s increasingly important that paramedics be able to interpret a 12-lead ECG. It’s also worth remembering that the ACC/AHA guidelines recommend measuring first medical contact-to-balloon times. We’ve come to call this “E2B” or “EMS-to-balloon,” although some health care professionals think E2B stands for “evaluation” to balloon or “EKG” to balloon. Regardless, it’s clear that we’re not doing STEMI patients a favor by delivering them to hospitals incapable of prompt, expertly performed primary PCI, assuming that such a hospital is available within a reasonable distance. Of course, there is not broad agreement on what that reasonable distance is, and many barriers stand in the way. For example, not all EMS systems are equipped with 12-lead ECG monitors. In some jurisdictions, ambulances are not allowed to leave the county. Many community non-PCI hospitals may be concerned about loss of revenue, especially since their reimbursement is based on an acuity index. STEMI patients have a high acuity index, so when they lose STEMI patients, they’re paid less for everything else. Because 12-lead ECG interpretation is not generally part of a paramedic’s initial education, in many EMS systems the ECG has to be transmitted to the hospital for physician interpretation, which is expensive and can have a high failure rate depending on the location. Relying on computerized interpretation is a possibility. However, while the ***ACUTE MI SUSPECTED*** message has a fairly high specificity, it’s not particularly sensitive, so it misses a lot of STEMIs. Poor data quality can also lead to false positives. The ideal solution is to train paramedics to read the 12-lead ECG with a high degree of accuracy, with a special emphasis on the STE-mimics (left ventricular hypertrophy, left bundle branch blocks, benign early repolarization, hyperkalemia, pericarditis, paced rhythm, and so on). Even then, there might be difficulty getting the emergency physicians to trust the paramedic’s judgment. One of the main thrusts of the D2B Alliance has been granting emergency physicians the authority to activate the cardiac cath lab. So, cardiologists had to learn to let go and trust their colleagues in emergency medicine. Obviously, granting paramedics this kind of authority is necessarily a step-wise process, and requires a lot of communication and robust quality feedback mechanisms. We know it can work, because it’s working now in many areas of the country. On the other hand, we know it’s important to keep false positive cardiac cath lab activations to a reasonable level, and it’s not yet clear what that level is. No matter what we do, a certain percentage of patients are going to have a clean angiography. Adding to the difficulty is the lack of consensus on how we define things like “false positives”. I suspect these issues are going to work themselves out in the next decade or so. It’s an exciting time to be involved in emergency cardiac care! Tell us about your job as a paramedic. What is a typical day like for you? How often do you have to read ECGs? What are the most common heart rhythm problems you most often come across? I’m a paramedic, but I’m also a fire lieutenant, so my typical day is probably a lot different from a paramedic with no fire suppression responsibilities. I also work on Hilton Head Island, which is a resort community with seasonal variations in population. There are about 35,000 year-round residents, but our peak summertime population can be well over 200,000. With cardiovascular disease being the number one killer in the industrialized world (Eugene Braunwald, MD calls it “the scourge of our time”), we see our fair share of chest pain patients. I should say we see our share of “suspected ACS patients”, since we all know by now that 1 out of 5 patients presents with atypical symptoms. The most common heart arrhythmia we see is atrial fibrillation (no surprise there), but it’s certainly not uncommon for our STEMI patients to present with sinus bradycardia or various degrees of heart block. It would be nearly impossible for me to count the number of ECGs I read on a daily basis, since I’m also the co-moderator of the EKG Club listserv at Yahoo! (https://health.groups.yahoo.com/group/ekg_club/), where we have over 800 members from around the world who submit ECG-based cases on a regular basis. So I read a lot of ECGs from patients I’ve never actually come into contact with. What information do you have included on the website? How often do you update the site? It started with a tutorial on axis determination, but I’ve written about everything from ST segment elevation and differential diagnosis of wide complex tachycardias to the problem of false capture with transcutaneous pacing. I set out with the goal to just have fun, and within a couple of weeks, I was getting hundreds of hits. I’m currently averaging about 15 posts per month. What ECGs do you have listed? What are some of the more interesting ECGs you have listed? My personal favorite is a STEMI patient with a bifascicular block. I’m especially interested in identifying AMI in the presence of baseline abnormalities, so it gives me the opportunity to discuss things like the “rule of appropriate T wave discordance”, which I think is critically important to accurate 12-lead ECG interpretation. Are there any specific rhythms in general that are particularly difficult to diagnose or read? Which ones? Absolutely. Wide QRS tachycardias are notoriously challenging. Then you have others that look alike, for example, atrial fibrillation and multifocal atrial tachycardia. Those are more interesting from an academic standpoint. Once you get into things like irregular or polymorphic wide complex tachycardias, you’re entering an area where you can kill the patient if you select the wrong drug, so they’re not just difficult to diagnose or read, they are also high-risk patients. I’m familiar with cases where patients with atrial fibrillation and Wolff-Parkinson-White syndrome were given the wrong drugs and had a bad outcome. When you’re playing around with antiarrhythmics, you are taking on a huge responsibility. Give us an example of a difficult case you have treated. I remember the first cardiac arrest patient I treated according to the “new” science. It was a witnessed arrest and the initial rhythm was VF, but no CPR had been initiated prior to EMS arrival. We did two minutes of CPR prior to the first shock, with delayed tracheal intubation. The patient experienced ROSC and we captured a 12-lead ECG immediately, which showed acute inferior STEMI. It was transmitted to the emergency department and the patient went to the cardiac cath lab. Unfortunately, the patient never “woke up”, but we did everything right. In hindsight, I can’t help but wonder whether or not the patient might have experienced neurological recovery had we induced hypothermia (something we don’t do yet on Hilton Head Island). They’re doing amazing things in Wake County, North Carolina. For example, in the city of Raleigh, 49% of their cardiac arrest patients are walking out of the hospital (witnessed arrests with an initial rhythm of VT/VF). Other EMS systems are starting to take notice. Hopefully with things like the Cardiac Arrest Registry to Enhance Survival (CARES), which is a national database administered by Emory and the CDC, more communities will start to measure their success rates and implement best practices. More information can be found at https://mycares.net/. What suggestions can you offer to those who are trying to learn about ECGs? What are some of the important lessons you’ve learned over the years? The most important lesson is to always interpret the ECG in light of the history and clinical presentation. That is the hardest lesson to grasp, but it’s the most important lesson of all. The other is to remember the first rule of medicine, which is “do no harm”. There is no shame in asking for an expert consultation. As for the nuts and bolts of cardiac rhythm analysis, it’s the realization that the heart has two rhythms happening at the same time, one atrial and the other ventricular (hopefully in a 1:1 relationship with a functioning AV node). This is probably why studying implantable medical devices has deepened my understanding of heart rhythms. After all, pacemakers function by offsetting defects in the heart’s electrical conduction system. For 12-lead ECG interpretation, I recommend using a systematic approach. I teach a six-step method (see below), and so far it’s kept me out of trouble: 1)Rhythm; 2) Axis; 3) Intervals; 4) Morphology; 5) Mimics; 6) Ischemia, injury, and infarct. What sorts of responses have you received about the blog? Who do you find most often visits your blog? The response has been very encouraging. Since the blog is directed primarily at EMS professionals, I’m assuming that paramedics make up the majority of my readership, but a lot of people come to the blog through Google. So, if your search term is “axis determination” or “Sgarbossa’s criteria”, you might find the Prehospital 12 Lead ECG blog. It’s been especially fun to discover that I have an international readership. My “statcounter” indicates that I’ve been visited by 82 countries and counting. What other sites or textbooks can you recommend for those learning in the field? I owe a debt to Garcia and Holtz’s 12-Lead ECG: The Art of Interpretation (Jones & Bartlett). I also have a copy of Chou’s Electrocardiography in Clinical Practice: Adult and Pediatric (Saunders), which I use for reference. The important thing is to find a book that speaks to you. I’d also suggest collecting ECGs in a scrapbook. Make sure you jot down the chief complaint, vital signs, medications, and anything else that might be clinically relevant. I’ve been collecting interesting ECGs for years, and it’s one of the more useful things I’ve ever done. As you learn more about ECG interpretation, you can go back and discover things about the “old” ECGs that you didn’t notice before. One of my favorite cases on the blog is a wide complex tachycardia that for years I thought was atrial fibrillation with a rate-activated RBBB. It turned out to be VT. Even better than putting ECGs in a book is scanning them into PowerPoint, because one thing I’ve noticed is that ECGs tend to fade over the course of a few years. For more information on developing regional STEMI systems, check out the EMS-to-balloon (E2B) Challenge listserv on Yahoo! (which I also co-moderate): https://health.groups.yahoo.com/group/E2B/. Anything else you’d like to add? A lot of people think that if you ask two cardiologists about an ECG, you’ll get two wildly different opinions. While I’ve seen that happen on occasion, that doesn’t mean there is more than one correct answer. When I worked on the Critical Care Step-down unit of a 400-bed community hospital with two cath labs and an open-heart program, I came into contact with several different cardiologists, and I found that the one who is “right” can usually explain the reason, and the reason is the most important part if you’re trying to develop expertise in this area.