Abstract
BackgroundPulmonary vein (PV) ablation is unsuccessful in atrial fibrillation (AF) patients with high left atrial (LA) pressure. Increased atrial stretch by increased pressure is proarrhythmic for AF, and myocardial scar alters wall deformation. We hypothesized that localized PV scar is proarrhythmic for AF in high LA pressure.MethodsRadiofrequency energy was delivered locally in the right PV of healthy sheep. The sheep recovered for 4 months. Explanted hearts (n = 9 PV scar, n = 9 controls) were perfused with 1:4 blood:Tyrode’s solution in a four-chamber working heart setup. Programmed PV stimulation was performed during low (∼12 mmHg) and high (∼25 mmHg) LA pressure. An AF inducibility index was calculated based on the number of induction attempts and the number of attempts causing AF (run of ≥ 20 premature atrial complexes).ResultsIn high LA pressure, the presence of PV scar increased the AF inducibility index compared with control hearts (0.83 ± 0.20 vs. 0.38 ± 0.40 arb. unit, respectively, p = 0.014). The diastolic stimulation threshold in high LA pressure was higher (108 ± 23 vs. 77 ± 16 mA, respectively, p = 0.006), and its heterogeneity was increased in hearts with PV scar compared with controls. In high LA pressure, the refractory period was shorter in PV scar than in control hearts (178 ± 39 vs. 235 ± 48 ms, p = 0.011).ConclusionLocalized PV scar only in combination with increased LA pressure facilitated the inducibility of AF. This was associated with changes in tissue excitability remote from the PV scar. Localized PV ablation is potentially proarrhythmic in patients with increased LA pressure.
Highlights
Atrial fibrillation (AF) is a common cardiac arrhythmia that afflicts approximately 10% of the population above 80 years (Kannel and Benjamin, 2009)
Electrical isolation of the pulmonary veins (PVs) from the left atrium (LA) by ablation is recommended in paroxysmal AF patients who do not respond to pharmacological therapy (Calkins et al, 2018)
Not all right PV (RPV) slices contained collagenous scar (Figure 5, right panel), which occurred at localized areas within the RPV
Summary
Atrial fibrillation (AF) is a common cardiac arrhythmia that afflicts approximately 10% of the population above 80 years (Kannel and Benjamin, 2009). Heart failure, hypertension, and valvular disease lead to increases in atrial pressure and are Proarrhythmic Pulmonary Vein Scar associated with AF (Kannel and Benjamin, 2009). A preexisting large LA, comorbidity of hypertension, and a LA pressure > 15 mmHg measured during the ablation procedure are risk factors for ablation failure (Themistoclakis et al, 2008; Evranos et al, 2016; Sramko et al, 2017). This questions the role of high atrial pressure on ablation success. We hypothesized that localized PV scar is proarrhythmic for AF in high LA pressure
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