Editor's Note: Commentary based on Page RL, Joglar JA, Caldwell MA, et al. 2015 ACC/AHA/HRS Guideline for the Management of Adult Patients With Supraventricular Tachycardia: A Report of the American College of Cardiology/American Heart Association Task Force on Clinical Practice Guidelines and the Heart Rhythm Society. J Am Coll Cardiol 2015 Sept 16. [Epub ahead of print].

Background

Supraventricular tachycardias (SVTs) are a heterogeneous group of arrhythmias that require atrial and/or atrioventricular nodal tissue for their initiation and maintenance.¹ SVTs are commonly encountered in clinical practice and in the emergency room, with an incidence of 35 cases per 100,000 persons per year and a prevalence of 2.25 cases per 1,000 people in the general population, not including atrial fibrillation (AF) and atrial flutter (AFL).² These arrhythmias can often be very symptomatic, causing significant palpitations, lightheadedness, chest pain, shortness of breath, and even anxiety. Fortunately, they are also responsive to treatment with medications or catheter ablation.

The term paroxysmal supraventricular tachycardia (PSVT) typically refers to three main arrhythmias: atrioventricular nodal re-entrant tachycardia (AVNRT), atrioventricular re-entrant tachycardia (AVRT), and focal atrial tachycardia (AT). Other, less common tachycardias, such as sinus node re-entrant tachycardia and junctional ectopic tachycardia (JET), also fall under the category of PSVT. In addition, macro-re-entrant ATs, including typical AFL, and multifocal atrial tachycardia are also commonly included under the umbrella term SVT. Although AF is technically an SVT, the term SVT is usually not used when referring to a rhythm that is clearly AF because AF is a very different entity, can usually be differentiated clearly from other forms of regular SVTs, and has unique management issues related to its association with stroke.³

The New Guideline

Because SVTs are a commonly encountered entity in clinical practice, it is important to have up-to-date and comprehensive guidance for their management. The 2015 ACC/AHA/HRS Guideline for the Management of Adult Patients with Supraventricular Tachycardia provides just such a comprehensive and well written reference for the evaluation and management of SVTs, including atrial flutter. It is an update of the 2003 guideline and was created by a strong group of authors, lead by the prominent heart rhythm expert Richard Page, MD, FACC.

The guideline begins with a thorough list of definitions and proceeds to a discussion of SVT epidemiology and initial evaluation of the patient with SVT of unknown mechanism. The excellent electrocardiogram examples of each SVT are strong components of the document. Next, each individual SVT is discussed in detail, and separate flow charts for both acute and chronic management are provided. Finally, special populations are addressed, including pediatric patients, adults with congenital heart disease, pregnant patients, and the elderly.

While many, if not most, of the underlying principles of SVT management have remained largely unchanged over the last decade, several updates from the 2003 guideline are provided in the new guideline. The first main update is that the current guideline more clearly separates the acute and the ongoing management of patients with SVT, providing flow charts and recommendations for acute and ongoing management of each individual arrhythmia and for SVTs of unknown mechanism. These various clinical scenarios are somewhat artificial, however, because the mechanism of tachycardia in most patients with SVT is not absolutely clear until an electrophysiology study has been performed, at which time almost all patients undergo ablation of the substrate and no longer present with tachycardia. Nonetheless, these flow charts should prove to be a useful tool for guiding both the acute management of patients in the emergency room and their ongoing management in the clinic, as well as help to put the specific guideline recommendations in perspective. Another addition to the current guideline is a discussion of, and guidance on the use of, the novel drug ivabradine. This is a new drug recently approved in the U.S. for the management of patients with heart failure, but as a specific blocker of the If current, is also being used in the management of inappropriate sinus tachycardia. Finally, the use of digoxin is deemphasized, and the drug dofetilide is mentioned more prominently in the new recommendations.

The new guideline is an excellent contribution and resource, but five points are worthy of mention:

1. Patients with health problems are commonly asked to make decisions between medical and surgical treatment options. Patients with recurrent SVT are often given the choice between an antiarrhythmic drug and an invasive catheter ablation. When weighing the risks and benefits of these two options, an accurate knowledge of the risks of catheter-based procedures is of critical importance. The risks of an ablation procedure, however, seem to be overstated in the guidelines. This may lead to unnecessarily conservative recommendations by the readers of the guideline. For example, the section covering the ongoing management of SVT of unknown mechanism provides a table (see Table 9 in the document) of major complication rates related to catheter ablation procedures for various forms of SVT. It lists major complication rates of 3.0% and 2.8% for ablation of AVNRT and AVRT, respectively. These rates seem higher than most experienced electrophysiologists see in daily practice; other studies have reported rates of major complications closer to 0.5% to 1%.^5,6 In addition, the effect of operator experience on procedural risk is not mentioned in the guideline. It has been shown that for ablation procedures for AF, for example, that operators and hospitals with higher annual procedural volumes (>25 and >50 procedures per year, respectively) have significantly lower complication rates compared to those who perform fewer procedures.⁷ Similar trends are also true across the other procedural fields of medicine, and the same is almost certainly true for SVT ablation. This fact should be mentioned more prominently in the guideline, perhaps even with a recommendation to consult with a high-volume operator or center when possible.
2. The new guideline emphasizes two treatment options for SVT – medications and ablation. However, it should also be noted that in the absence of ventricular pre-excitation during sinus rhythm (Wolff-Parkinson-White [WPW] syndrome), "doing nothing" is also an option for patients with SVT. Observation without treatment is a reasonable choice in patients with SVT, particularly in patients who have had only a single episode, are minimally symptomatic, or have infrequent, brief, self-terminating episodes. The option of clinical follow-up without treatment is, in fact, incorporated into flow diagram for the ongoing management of AVNRT (see Figure 13 in the document). However, it is omitted from the primary flow diagram for the ongoing management of SVT of unknown mechanism (see Figure 9 in the document). The option of clinical follow-up without treatment is certainly reasonable and should be more clearly incorporated into the guideline statement as an initial treatment strategy.
3. As mentioned above, clinical follow-up with no treatment is reasonable as a first-line option in many cases of SVT in the absence of WPW syndrome. On the other hand, patients with WPW syndrome should not only not be offered expectant management, but should be strongly encouraged to undergo ablation rather than be offered a trial of medical therapy. Although the overall risk of sudden cardiac death is low in patients with WPW syndrome, the risk is high enough to warrant aggressive therapy. The flow diagram in the guideline for the ongoing management of patients with AVRT and WPW syndrome (see Figure 15 in the document) states that ablation is indicated when the patient with WPW syndrome is "willing" to undergo ablation. It could have included stronger language related to the importance of ablation, leaving medical therapy as a second-line option only if the patient "refuses" or "declines" ablation.
4. While AFL is technically an SVT, the management of AFL more closely aligns with that of AF, particularly in regards to anticoagulation. As such, AFL seems somewhat out of place in the SVT guidelines, and discussing AFL as part of the AF guidelines may be a more logical approach in future guidelines. As it currently stands, a detailed discussion of anticoagulation is omitted from the SVT guideline, which simply references the AF guideline, requiring the reader to search out another document for specific recommendations. In addition, anticoagulation is omitted from the treatment flow diagrams (see Figures 18 and 19 in the document), even though it is a critical component of management, particularly in patients with stroke risk factors or those undergoing cardioversion.
5. Finally, it is notable that there is only a single Class I, Level of Evidence A, recommendation in the guideline – for the use of oral dofetilide or intravenous ibutilide for pharmacologic cardioversion of atrial flutter. High-quality evidence from randomized controlled trials seems to be lacking for the management of most SVTs. This knowledge gap of the management of SVT provides equipoise for the evaluation of various strategies, both medical and catheter-based, for the treatment of SVT.

Supraventricular tachycardia is a common clinical problem managed by many internists, cardiologists, and electrophysiologists. Despite some of the minor criticisms mentioned above, the new 2015 ACC/AHA/HRS Guideline for the Management of Adult Patients with Supraventricular Tachycardia provides an excellent and comprehensive guide to the management of SVT and is a welcomed update.

References

1. Delacretaz E. Clinical practice. Supraventricular tachycardia. N Engl J Med 2006;354:1039-51.
2. Orejarena LA, Vidaillet H Jr, DeStefano F, et al. Paroxysmal supraventricular tachycardia in the general population. J Am Coll Cardiol 1998;31:150-7.
3. January CT, Wann LS, Alpert JS, et al. 2014 AHA/ACC/HRS guideline for the management of patients with atrial fibrillation: a report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines and the Heart Rhythm Society. J Am Coll Cardiol 2014;64:e1-76.
4. Blomstrom-Lundqvist C, Scheinman MM, Aliot EM, et al. ACC/AHA/ESC guidelines for the management of patients with supraventricular arrhythmias--executive summary. a report of the American college of cardiology/American heart association task force on practice guidelines and the European society of cardiology committee for practice guidelines (writing committee to develop guidelines for the management of patients with supraventricular arrhythmias) developed in collaboration with NASPE-Heart Rhythm Society. J Am Coll Cardiol 2003;42:1493-531.
5. O'Hara GE, Philippon F, Champagne J, et al. Catheter ablation for cardiac arrhythmias: a 14-year experience with 5330 consecutive patients at the Quebec Heart Institute, Laval Hospital. Can J Cardiol 2007;23 Suppl B:67B-70B.
6. Bohnen M, Stevenson WG, Tedrow UB, et al. Incidence and predictors of major complications from contemporary catheter ablation to treat cardiac arrhythmias. Heart Rhythm 2011;8:1661-6.
7. Deshmukh A, Patel NJ, Pant S, et al. In-hospital complications associated with catheter ablation of atrial fibrillation in the United States between 2000 and 2010: analysis of 93 801 procedures. Circulation 2013;128:2104-12.

Keywords: Aged, Anti-Arrhythmia Agents, Anxiety, Arrhythmias, Cardiac, Atrial Fibrillation, Atrial Flutter, Benzazepines, Catheter Ablation, Chest Pain, Death, Sudden, Cardiac, Digoxin, Dizziness, Dyspnea, Electric Countershock, Electrocardiography, Electrophysiology, Emergency Service, Hospital, Follow-Up Studies, Heart Conduction System, Heart Failure, Incidence, Phenethylamines, Pregnancy, Prevalence, Randomized Controlled Trials as Topic, Risk Assessment, Risk Factors, Sinoatrial Node, Stroke, Sulfonamides, Tachycardia, Ectopic Junctional, Tachycardia, Sinus, Tachycardia, Supraventricular, Wolff-Parkinson-White Syndrome

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