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Atrioventricular dyssynchrony in patients with permanent pacemaker due to sinus node dysfunction and first-degree atrioventricular block: does the long PR syndrome exist?

Journal of Cardiology & Current Research
Andrés Di Leoni Ferrari,1 Eduardo Bartholomay,1 Fabio Michalsky Velho,1 Anibal Pires Borges,1Matheus Bom Fraga,1Luis Manuel Ley Domingues,1José Carlos Pachón Mateos2


Background:First-degreeatrioventricularblock (AVB)mightnotbebenign.MarkedlylongPRintervalsmaycausecardiac dyssynchrony,with manyconsequences.Restoringoptimal AV synchrony represents a reasonable option for hemodynamic and clinicalimprovement.

Objectives: To compare 2 cardiac pacing strategies for bradycardia associated with first-degreeAVB: (1)longPRinterval(PRi)–narrowintrinsicQRS,avoidingventricularpacingbut potentially causing AV dyssynchrony (AVD); vs (2) optimized AV interval (oAVi)–wide pacedQRS, potentiallyinducingventriculardyssynchrony.

Methodology:ProspectivecohortstudywithpatientswithpermanentDDDpacemakersdue to sinus disease associated with first-degree AVB (binodal disease). We analyzeddiastolic filling time (DFT), defining 2 groups: patients with AV synchrony (AVS) andAVD.Clinicalandechocardiographicfollow-upwasperformedfora year.

Results: We studied 43 patients (mean age 71 years; 51.2% female). Longer PRis wereassociated with worse baseline ventricular systolic function. The AVD group (24/43)showed longer PRi (mean=283.5ms; p≤0.001) and reduced ventricular DFT (p=0.032).First-degree AVB with PRi>263ms (relative risk [RR]=1.84; p=0.024; specificity=78.9%;95% confidence interval [CI] 0.43–0.79) and DFT<40% of the cardiac cycle duration(RR=0.99; p<0.001) were independent predictors of AVD. When PRi>300ms,dyssynchrony was not correctable by AVi optimization. The AVS group (controls, n=19;mean PRi=252.4ms), despite maintaining synchrony, had worsened mitral regurgitation(p=0.008)atfollow-up.

Conclusions: First-degree AVB comprehends significantly different patients: those withAVDandAVS,determinedbyDFTandPRilength.Inthose withAVD,wehypothesized the existence of the “long PR syndrome”, defined from a PRi>263ms associated with overtDFTimpairment.


SND, sinus node dysfunction , AVB, atrioventricular block, PRi, PR interval, ACP, artificial cardiac pacing, RV, right ventricle, AVi, atrioventricular interval, AF, atrial fibrillation, HF, heart failure, ECG, electrocardiogram, DFT, diastolic filling time