Материал: 2019 ESC - supraventricular tachycardia

•Antidromic AVRT due to an atriofascicular pathway usually produces a horizontal or superior QRS axis, but a normal axis may also occur, depending on the way of insertion into the right bundle and fusion over the left anterior fascicle.

•Right bundle electrogram preceding His bundle activation during anterograde pre-excitation and SVT.

Mapping identifies the proximal and distal insertion of accessory fibres, and demonstrates pathway potentials in most cases that then guide ablation.409,411 Catheter ablation is associated with a high success rate and low recurrence rates, and is therefore recommended for all patients with recurrent symptomatic tachycardia, and especially incessant tachycardias due to concealed nodofascicular or nodoventricular pathways.418 Preventive ablation for prognostic reasons is not routinely recommended, not even in patients with preexcitation or BBB in the surface ECG, as fast conduction via the AP is unlikely due to decremental conduction properties.

11.3.10 Therapy

11.3.10.1 Acute therapy

Adenosine should be used with caution for the treatment of AVRT because of potential induction of fast AF.119,120,272 AF with fast ventricular

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conduction could also induce ventricular fibrillation, therefore electrical cardioversion should always be available. During orthodromic and antidromic AVRT, drug therapy could be directed at one of the components of the circuit, the AVN (beta-blockers, diltiazem, verapamil, or etripamil),100,129,419,420 or the AP (ibutilide, procainamide, propafenone, or flecainide)421,422 (Figure 19). Antidromic AVRT is associated with malignant WPW syndrome due to a very fast-conducting AP,403 and drugs acting mainly on the AP should be preferred. In addition, in case of antidromic AVRT with APs representing both the anterograde and retrograde limb, drugs acting on the AVN are ineffective. In drug-refractory antidromic AVRT, amiodarone may also be considered.423 425

In patients presenting with pre-excited AF, urgent cardioversion is usually required and the threshold for the use of electrical cardioversion is lower. Conduction of electrical impulses can occur preferentially via the AP due to its shorter RP compared with the AVN.426 Accordingly, any AVN-modulating agents (adenosine, verapamil, diltiazem, beta-blockers, or digoxin) should be avoided in pre-excited AF as they may contribute to a risk of ventricular fibrillation.427,428 Pharmacological cardioversion of pre-excited AF or delayed AP conduction can be achieved with ibutilide (Figure 20).421 Drugs such as procainamide, propafenone, or flecainide, which affect conduction

Yes

Synchronized cardioversion

(I B)

If ineffective

©ESC 2019

Pre-excited AF

Haemodynamic

instability

Synchronized cardioversion (I B)

Figure 20 Acute therapy of pre-excited atrial fibrillation. AF = atrial fibrillation; i.v. = intravenous.

over the AP, may also be used, even if they may not restore sinus rhythm.429 431 However, class Ic drugs should be used with caution as they do exert an effect on the AVN. In pre-excited AF, i.v. amiodarone may not be as safe as previously thought, because enhanced pathway conduction and ventricular fibrillation have been reported, and should not be considered.432 435 Procainamide appears to be safer in this setting.436

11.3.10.2 Catheter ablation

The treatment of choice for patients with symptomatic and recurrent AVRT, or pre-excited AF, is catheter ablation (Figure 21). For other patients with asymptomatic and infrequent episodes, therapeutic decisions should be balanced between the overall risks and benefits of the invasive nature of ablation vs. long-term commitment to pharmacological therapy. Ablation of the AP has a high

acute success rate and is associated with a low complication rate depending on the pathway location (Table 9).391 393,438 440 Major

complications include cardiac tamponade (0.13 1.1%) and complete AV block (0.17 2.7%) in patients in whom ablation of septal APs is attempted. With septal APs close to the AVN, the ECG typically displays a positive delta wave in leads avF and avL, and a nar-

row positive delta wave in lead V1 that has a prominently negative QRS complex.394

When targeting septal pathways and applying cryoenergy, the incidence of AV block is lower compared with radiofrequency energy.447 However, recurrence of previously blocked pathways has been reported to be significantly higher when cryoenergy is applied.438 Two approaches are available for left-sided pathways: an antegrade transseptal and a retrograde aortic approach. There is evidence that the transseptal approach, in experienced hands, results in reduced radiation and procedure times.441,448

AVRT = atrioventricular re-entrant tachycardia.

secondary to pre-excited AF that conducts rapidly to the ventricle over the AP, resulting in ventricular fibrillation, is the most feared manifestation of WPW syndrome. The risk of cardiac arrest/ventricular fibrillation has been estimated at 2.4 per 1000 personyears (95% confidence interval 1.3 3.9), but no deaths were reported in a registry of 2169 patients over an 8 year follow-up period.439 However, in a Danish registry of 310 individuals with pre-excitation (age range 8 85 years), there was a greater risk of AF and HF, driven by a right anteroseptal AP, and in patients aged >65 years there was also a statistically significant higher risk of death.22

Clinical and electrophysiological features associated with an increased risk of sudden cardiac death include younger age,439,449,450 inducibility of AV-reciprocating tachycardia during EPS,450 454 multiple APs,450,451,455,456 and demonstration of a

capability of the AP to allow rapid conduction to the ventricles.439,450,451,453 456 These variables include the shortest pre-

excited RR interval during AF (SPERRI) of <250 ms at baseline or

a short antegrade effective refractory period (ERP) of the AP (<250 ms).439,450 452,454 460 With non-invasive testing, identifica-

tion of an abrupt and complete normalization of the PR interval with loss of delta wave during exercise testing, or following procainamide, propafenone, or dispopyramide administration, has

been considered a marker of low risk. Catecholamine sensitivity is a major limiting factor of all tests, both invasive452,460 and non-invasive, including exercise testing. Intermittent loss of pre-excitation on a resting ECG or ambulatory monitoring has also been associated with APs with longer ERPs, and has been accepted as a credible risk-stratification tool.2,464 However, a number of recent studies, which have included both symptomatic and asymptomatic patients, have indicated that more than onefifth of patients with intermittent pre-excitation have AP ERPs <250 ms. Thus, intermittent pre-excitation is now recognized as an imperfect marker of a low-risk AP.

Over the past 30 years, a considerable body of literature has been published that has focused on the important topic of the evaluation and management of patients with asymptomatic preexcitation. These publications include those that describe the clinical and electrophysiological characteristics of patients with preexcitation who have experienced a cardiac arrest,

and series of patients with pre-excitation who are either sympto-

matic or asymptomatic, and are followed for variable periods of

time.22,405,439,449,450,454,456,470 472 Among these studies, there has

been one prospective RCT of catheter ablation (37 patients) vs. clinical follow-up without treatment (35 patients) of patients with asymptomatic pre-excitation.453 Catheter ablation reduced the frequency of arrhythmic events (7 vs. 77%, P < 0.001) over 5 years. One patient in the control group had an episode of cardioverted ventricular fibrillation.

Figure 22 summarizes the recommendations for the screening and management of patients with asymptomatic pre-excitation.

Recommendations for the management of patients with asymptomatic pre-excitation

AP = accessory pathway; EPS = electrophysiology study; ERP = effective refractory period; LV = left ventricular; MS = mid-septal; SPERRI = shortest pre-excited RR interval during atrial fibrillation.

aClass of recommendation. bLevel of evidence

cSuch as pilots and professional drivers.

Invasive screening with an EPS should be performed in patients with asymptomatic pre-excitation who either have high-risk occupations or are competitive athletes (Figure 22). Variables on the EPS that identify patients with a high-risk AP include a SPERRI <250 ms, AP ERP <250 ms, multiple APs, and an inducible AP-mediated tachycardia in the baseline state or during isoproterenol infusion, which should always be tried.452,460 The options for screening patients who do not fall into these groups include the use of EPS as a risk-stratifying

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tool or the use of non-invasive screening with exercise testing, drug testing, and ambulatory monitoring as risk-stratification tools.

If a patient undergoes screening with an EPS and is found to have an AP with ‘high-risk’ characteristics, catheter ablation should be performed. Catheter ablation of an AP, when performed by an experienced operator, is associated with a high cure rate (>95%) and low risk (<0.5%) of major complications (see also Section 11.1.2.3).438 440 However, it should be noted that even invasive