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..................................................... rate (brady-dependent AVB), support a diagnosis of intrinsic infranodal AVB.27

5.2.2 Pacing mode and algorithm selection 5.2.2.1 Dual-chamber vs. ventricular pacing Large, randomized, parallel trials that included patients with only AVB181 or with AVB and/or SND140 failed to show superiority of DDD over ventricular pacing with regard to mortality, and have not consistently shown superiority in terms of quality of life or morbidity (including stroke or transient ischaemic attack and AF).20,140,181 Dualchamber pacing is beneficial over ventricular pacing due to the avoidance of pacemaker syndrome, which occurred in up to a quarter of patients with AVB in these trials. In a meta-analysis of 20 crossover trials, DDD was associated with an improved exercise capacity compared with ventricular pacing. However, the effect was driven by non-rate-modulated ventricular pacemakers, and no benefit was observed from the comparison of DDD with VVIR pacing.182 Pacemaker syndrome is associated with reduction in quality of life and may require a reintervention for upgrading, justifying the preference for DDD when reasonable (i.e. in patients who do not present with significant frailty, very advanced age, significant comorbidities limiting their life expectancy, or a very limited mobility). Another consideration is the diagnosis of AF, which is more reliable from device data in patients with DDD pacemakers. On a case by case basis, in frail elderly patients, and/or when AVB is paroxysmal and pacing anticipated to be infrequent, VVIR pacing may be considered as it carries a lower complication rate.140 There is strong evidence to show that chronic conventional RV pacing may be deleterious in some patients and may lead to LV dysfunction and HF,148 even when AV synchrony is maintained.183 This effect is only partly explained by the abnormal activation sequence and may involve myocardial perfusion, and humoral, cellular, and molecular changes.184,185 Compared with a matched control cohort, patients with a pacemaker and an RV lead have an increased risk of HF, which is also associated with older age, previous MI, kidney disease, and male sex.186 Pacing-induced cardiomyopathy occurs in 1020% of patients after 24 years of RV pacing.186188 It is associated with a >20% RV pacing burden.187190 However, there are no data to support that any percentage of RV pacing can be considered as defining a true limit below which RV pacing is safe and beyond which RV pacing is harmful. For discussion of potential indications for CRT and/or HBP to prevent pacing-induced cardiomyopathy, please refer to sections 6 and 7.

5.2.2.2 Atrioventricular block in the case of permanent atrial fibrillation In the presence of AF, AVB should be suspected if the ventricular rate is slow and the ventricular rhythm regular. During prolonged monitoring, long ventricular pauses may be detected.191 In patients with AF and no permanent AVB or symptoms, there is no identifiable, minimum pause duration as an indication for pacing. In the absence of a potentially reversible cause, bradycardia or inappropriate chronotropic response (due to either intermittent or complete AVB) associated or reasonably correlated with symptoms is an indication for cardiac pacing. Any high-degree or infranodal block is also an indication for pacing, even in the absence of symptoms. In the absence of symptoms due to bradycardia and of high-degree or infranodal block, pacing is unlikely to be beneficial and is not indicated.

In patients with AF who undergo atrioventricular junction (AVJ) ablation to control rapid ventricular rates, there is evidence to show that AVJ ablation plus RV pacing improves symptoms and quality of life.192 In contrast, neutral results were found regarding the progression of HF, hospitalization, and mortality,193 except in one study.194 Compared with pharmacological rate control, AVJ ablation and CRT reduced the risks of death due to HF, hospitalization due to HF, or worsening HF by 62%, and improved specific symptoms of AF by 36% in elderly patients with permanent AF and narrow QRS.195 In other studies, this beneficial effect was limited to patients with HF or reduced ejection fraction (EF).166,196 For further discussion of the role of CRT following AVJ ablation, refer to section 6. There is weak evidence to support a benefit from para-Hisian and Hisian pacing after AVJ ablation for refractory AF.197200 For further discussion, refer to section 7.

Recommendations for pacing for atrioventricular block

Recommendations Classa Levelb

Pacing is indicated in patients in SR with permanent or paroxysmal third- or second-degree type 2, infranodal 2:1, or high-degree AVB, irrespective of symptoms.c 912 I C Pacing is indicated in patients with atrial arrhythmia (mainly AF) and permanent or paroxysmal third- or high-degree AVB irrespective of symptoms. I C In patients with permanent AF in need of a pacemaker, ventricular pacing with rate response function is recommended.201204 I C Pacing should be considered in patients with second-degree type 1 AVB that causes symptoms or is found to be located at intra- or infra-His levels at EPS.177180 IIa C In patients with AVB, DDD should be preferred over single-chamber ventricular pacing to avoid pacemaker syndrome and to improve quality of life.20,140,181,182 IIa A Permanent pacemaker implantation should be considered for patients with persistent symptoms similar to those of pacemaker syndrome and clearly attributable to first-degree AVB (PR >0.3 s).205207 IIa C Pacing is not recommended in patients with AVB due to transient causes that can be corrected and prevented. III C

AF = atrial fibrillation; AVB = atrioventricular block; DDD = dual-chamber, atrioventricular pacing; EPS = electrophysiology study; SR = sinus rhythm. aClass of recommendation. bLevel of evidence. cIn asymptomatic narrow QRS complex and 2:1 AVB, pacing may be avoided if supra-Hisian block is clinically suspected (concomitant Wenckebach is observed and block disappears with exercise) or demonstrated at EPS. ESC 2021

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