Standing Under the Supraventricular Tachycardia Umbrella
When I first started learning about arrhythmias, I was taught each of the rhythms individually. Learning this way led to a strong foundation and an understanding that each arrhythmia has its own clinical presentation, diagnostic criteria, and treatment approach.
Then, I found out about a very simple classification of arrhythmias, widely accepted within the medical community, that grouped various rhythm abnormalities under one umbrella. Basically, it states that any rhythm that starts in or uses any part of the atria, atrioventricular (AV) node, or bundle of His can be grouped together into one umbrella term: supraventricular tachycardia (SVT). This umbrella term can be broken down into a couple of smaller subgroups: narrow-complex SVT and wide-complex SVT. The smaller groups could then be approached and treated safely within certain parameters. I could perfectly understand the appeal of this system, as it was very simple to learn.
As I found out, this system has been around since the prehistoric periods of the late 20th century (I am a millennial, so anything predating 1990 is prehistoric) when we had much less understanding of the pathophysiology of these rhythms and were limited in our treatment capabilities. We began with minimalistic treatment approaches that provided some cursory support for patients. It was not perfect, but it was the best we had. As time progressed, so did our pharmaceutical and therapeutic armamentarium, allowing more focal treatment strategies. In military terms, we didn’t have to use carpet-bombing to hit our target; we now had smart bombs.
Looking at another analogy may help us more clearly understand the issue facing us. Let’s go back in time to the 1800s, before Louis Pasteur developed the germ theory. At the time, we assumed that contagious diseases developed spontaneously. Despite definitive proof that “germs” were the causative organisms responsible for many diseases, people refused to accept this change in thinking for many years. Eventually, they did, and a new era was formed. Penicillin was discovered and was used to treat everything. Sometimes it worked, sometimes it didn’t. Subsequently, we found that there were multiple types of germs, and more antibiotics were discovered. We have had similar pendulum swings when viruses and prions were discovered. To make a long story short, as our knowledge of disease increased, our treatments for these diseases became increasingly focal. Soon, we developed focal antibiotic, antiviral, and other forms of therapy that were far more effective than the “shotgun” medicine we had been practicing before their discovery.
Despite multiple attempts to move away from this SVT umbrella term, people were reluctant to give it up. In 2015, the governing bodies decided to accept the inevitable and formulate a treatment strategy that would support broad-spectrum treatment of the arrhythmias in question. However, whether this is a step forward or a step backward is debatable.
We believe there is an elegant solution and approach that uses the strengths of both schools of thought to arrive at the best patient outcome. When confronting a hemodynamically unstable patient, the use of broad strokes is brilliant due to its speed of diagnosis and its ability to allow “shotgun” treatment to maintain hemodynamic stability. This approach lets you keep your patient alive long enough to figure out what he or she actually has.
To simplify the concept, let’s take another trip to analogy land and look at sports teams. On any given Sunday in the fall and winter, you will find a football game. Television coverage typically begins with a very detailed pregame assessment of the members of both teams and possible pivotal matchups to focus on during the game. Then the game starts and the focus changes to “team” play. We focus on beating the Cowboys, the Patriots, the Steelers—whichever team our team is playing. The teams are separate entities that stand in and of themselves. The players are necessary parts of the team needed to win the game. After the game, analysis refocuses on the players and the plays that affected the outcome.
What does this analogy have to do with arrhythmias? Well, before the emergent period (the pregame), you need to know the individual component players (rhythms), addressing their individuality, how they behave, and how they have to be controlled. During the emergent period (the actual game), you focus on and treat the umbrella diagnosis (the team) as a separate stand-alone entity. Your game plan has to be completely focused on the group in order to maintain hemodynamic stability. After the emergent period is over, you break down the team into the component rhythms and isolate the specific event most relevant to the outcome by completing your differential diagnosis. After identifying the culprit, you then use target-specific treatments to administer definitive care.
Always consider this emergent period as special, where emergent (shotgun) measures work well because of the need for speed. The umbrella concept is tailor-made for this period. Once stability is maintained, however, try to go back and look at the list of possible diagnoses and make a definitive diagnosis with a more focused approach.
In the coming chapters, we will provide you with a stepwise approach to patients with wide-complex tachycardias—another umbrella term. We will look at the basics and expose you to the emergent approach, then examine the individual criteria and algorithms used to arrive at a more definitive diagnosis. In Chapter 37, Wide-Complex Tachycardia: Putting It All Together, we will unify all of the components involved and give you some examples. Finally, we will cover individual rhythms in their own chapters.
We feel this approach allows you to maximize the strengths of both systems, providing you with a rapid, safe emergent means to arrive at a final specific diagnosis that allows definitive treatment and ultimate control. In the next few chapters, we hope this paradigm shift in your approach to these arrhythmias will help you simplify a very complex terrain.
—Daniel J. Garcia