Optimal SVT management: Are we there?

Summary

While cardiac electrophysiology has a long history with important basic observations beginning more than two centuries ago, modern clinical cardiac electrophysiology was really born with the seminal publication by Scherlag et al.¹ that demonstrated a method for intracardiac His bundle recording. Following this publication there were more than 10 years of data collection about tachyarrhythmias that included sites of origin, pathways used, and mechanisms involved. Then, in 1982 when catheter ablation began, we capitalized on the accumulated information by providing a means for therapy that actually ured patients of their tachyarrhythmias. Electrophysiologists could rightly post a sign over the entrance to their labs stating, “We fix ECGs.” Now, more than 40 years later, we understand the SVTs to a degree never before possible. The remaining challenge is atrial fibrillation, not covered in this document.

Recommendations set forth in guideline statements are common today, providing a ready resource for evidence-based medical decisions that are available to practicing physicians. The present document ably serves that purpose. Its figures and algorithms offer an easy-to-navigate, step-by-step decision-making guide to treating adult patients with all types of supraventricular tachycardias, other than atrial fibrillation. The document updates and supersedes the 2003 ACC/AHA/ESC guidelines for the management of similar patients by incorporating new and existing information from clinical trials, basic science, and evolving treatment strategies. It provides a statement about non-infant SVTs but offers no specific treatment recommendations, and also offers a brief discussion about costs.

Several points are worth emphasizing. First, table 1 provides a helpful breakdown of definitions about the strength of the recommendations: Class I strong, the recommendation is recommended; Class IIa, moderate, the recommendation is reasonable; Class IIb, weak, the recommendation might be reasonable; Class III, no benefit or producing harm, the recommendation is not indicated or is potentially harmful. The level or quality of the evidence supporting that particular recommendation is also broken down: Level A, high quality; Level B-R, moderate quality from 1 or more RCTs; Level B-NR, moderate quality from 1 or more nonrandomized studies; Level C-LD, studies with limitations of design or execution; Level C-EO, expert opinion.

The second point is that table 2 provides references to other, associated guidelines so the reader can compare the present document with previous guidelines and statements published on the same topic. The document itself gives a breakdown of each SVT.

Epidemiology and clinical presentation

While not provoking the same clinical challenge of ventricular tachyarrhythmias and sudden cardiac arrest, nevertheless SVTs have a considerable prevalence in the general population of 2.25 per 1,000 persons. Often initially presenting to emergency departments with palpitations, patients with SVT due to atrioventricular reentrant tachycardia (AVRT) using an accessory pathway have a younger mean age at onset than patients with atrioventricular nodal reentrant tachycardia (AVNRT). Women more than men have AVNRT, while more men may have AVRT. The incidence of manifest WPW pattern on the ECG is 0.1-0.3% in the general population, while the frequency of AVRT decreases with age. Symptoms relate to the rapid rate and perhaps to cannon A waves in AVNRT, from the short RP interval and atrial contraction against closed AV valves. The elevated atrial pressure and release of natriuretic protein during SVT is followed by polyuria. Elevated pressures cause uneven stretch of atrial muscle conducive to atrial fibrillation. True syncope is uncommon, but lightheadedness is frequent. While tachycardia rates in the elderly are slower, syncope is more common. More than half of the SVT episodes occur during driving, and the episodes are an obstacle in one-fourth.

ECG Evaluation

A 12-lead ECG obtained during SVT and sinus rhythm is extremely helpful in distinguishing the various types of SVT. Beginning with an analysis of the QRS complex, a duration >120ms (wide complex tachycardia, WCT) can be due to rate-related functional bundle branch block (BBB), preexisting BBB, anterograde conduction over an accessory pathway or ventricular tachycardia. Analysis of atrial and ventricular activation is next, including rates and relationships. Tables 4 and 5, and accompanying figures provide helpful criteria and examples. The algorithm in figure 7 is excellent.

Therapy

Figure 8 provides an algorithm for acute therapeutic decisions, while figure 9 gives advice on how to manage ongoing therapy, supported by information in tables 6 and 7. Table 8 outlines ablation for the individual arrhythmias, compiling success rates, complications, and references. This is critical, since so many SVTs can now be eliminated by catheter ablation techniques, a choice that can be considered early in the therapeutic setting.

Individual SVTs

The remainder of the document addresses each SVT, providing a brief description, followed by a detailed citation of acute and ongoing therapeutic recommendations. These areas include inappropriate sinus tachycardia, focal and multifocal tachycardia, AVNRT, AVRT, management, including risk stratification, of asymptomatic pre-excitation, isthmus-dependent and non-isthmus-dependent atrial flutter, and junctional tachycardia. Sections about SVTs in pediatric patients, adult patients with congenital heart disease, SVTs during pregnancy and in older patients, quality of life and cost considerations, shared decision making, and future research needs complete the document.

Overall assessment

This is an admirable document that provides extremely useful information to clinicians caring for SVT patients. It is comprehensive, thoughtful, and practical, and recommended reading. The extensive bibliography provides a ready resource to find the source documents.