2167Impact of dual-chamber pacing with closed loop stimulation on quality of life in patients with recurrent reflex vasovagal syncope: results from the SPAIN study

Background

Reflex vasovagal syncope (VVS) is one of the most common causes of syncope and, when recurrent, can have devastating consequences on the quality of life of patients despite pharmacological interventions. The closed loop stimulation (CLS) pacing algorithm converts, during an incipient VVS, variations in right intracardiac impedance into heart rate adaptation. The study SPAIN was the first randomized, double-blind trial robustly showing a strong reduction in syncopal recurrence in patients paced with dual-chamber (DDD)-CLS. (NCT01621464).

Purpose

To evaluate whether the differences observed in the SPAIN study regarding syncope burden and time to recurrence translate into improvements on quality of life.

Methods

This study analysed quality of life data from the SPAIN study: a randomized, prospective, double-blind, multicenter trial conducted in 10 Spanish and 1 Canadian centers. Ethics Committee approval was obtained at each participating center. Patients aged ≥40 years, with ≥5 VVS episodes and cardioinhibitory response to head-up tilt testing were included. After implant, patients were randomized 1:1 to active DDD-CLS mode for 12 months followed by sham DDI mode for the remaining 12 months or vice-versa. Quality of life was assessed via the Short Form-36 (SF-36) health survey before randomization (baseline), and at 12- and 24-month follow-up. The change in quality of life during the entire follow-up relative to baseline was compared between each pacing mode (DDD-CLS vs. DDI).

Results

Fifty-four patients were enrolled with a mean age of 56.3±10.6 years and a median of 12 syncopal episodes before randomization. Median SF-36 scores greatly increased from baseline in the DDD-CLS group across the 8 domains, whereas the response was variable in the DDI group. Comparing both pacing algorithms, median SF-36 scores were higher in the DDD-CLS group, with differences reaching statistical significance for “physical role” and “vitality” domains (p-value =0.006 and 0.014, respectively). Pacing sequence or treatment period did not significantly influence the response (p-value >0.05 for all the domains).

Conclusions

We demonstrated the beneficial effect of this physiological pacing algorithm on the quality of life of patients, as evidenced by the improvement in all the domains of the SF-36 when stimulated in DDD-CLS as compared to the sham DDI mode.

[Heart rate-ventricular extrasystole relations and their dependence on circadian rhythms]

The linear correlation of the circadian rhythms (CR) of heart rate (HR) with those of ventricular extrasystole (VE) is analyzed by electrocardiographic ambulatory monitoring in 32 patients: 22 with ischemic post-infarction cardiopathy (group A) and ten free of structural cardiopathy (group B). Variability expressed as the coefficient of ventricular extrasystole variation (100 x standard deviation/mean) presented an inverse correlation with the number of recording extrasystoles. Linear correlation between HR and VE was statistically significant in 72% of recordings in group A, and in 60% in group B. The percentage of cases with significant linear correlation was greater on analyzing the three-minute periods than with the longer periods. When the cases analyzed presented over 200 extrasystoles, the percentage with significant linear correlation between HR and extrasystole was greater in group A than in group B. The circadian rhythm of the ventricular extrasystoles using interpolation of a cosinor function was significant in 50% of group A cases, and in 60% of group B. The achrophases were diurnal in group B, but only in 45% of cases in group A, two correspondence models being found between the CR achrophases and the inverse linear correlation between HR and VE.

[Prediction of the tachycardia cycle based on auriculoventricular re-entry. Experimental study in dogs]

Seven anaesthesized mongrel dogs subject to thoracotomy were used in a electronic simile of A-V accessory pathway with retrograde conduction to generate reentrant tachycardias with different ventriculo-atrial delays. This was done both under control conditions and following amiodarone i.v. administration. The ability to predict tachycardia cycle length was studied, using a mathematical model of the circuit, in which the cycle length is obtained from the function of nodal conduction and the time of extranodal conduction of the circuit. An analysis was made of the repercussions in using four different mathematical functions describing nodal conduction: three were non-linear (exponential and hyperbolic A and B) and one linear. In the case of the first three, the consequences of using a direct non-linear data-fitting procedure or an indirect procedure by linear transformations of the functions were studied. The exponential and hyperbolic B functions provide a better prediction of tachycardia cycle length on being used in the model; in the case of these functions, a mean value of the squared differences between the real and estimated values of 19.1 +/- 31.0 ms2 and 19.1 +/- 26.7 ms2, respectively, was obtained.

Mathematical descriptions of AV nodal function curves in dogs

Thirty-four anaestheized mongrel dogs subjected to thoracotomy were used to study AV node conduction during atrial pacing at increasing rates. Epicardial atrial electrodes were used, together with endocavitary recordings of His bundle electrogram. An analysis was made of the repercussions involved in using four different mathematical functions describing nodal conduction: three were nonlinear (exponential and hyperbolic A and B) and one linear. In the case of the first three, the consequences of using a direct nonlinear data-fitting procedure or an indirect procedure by linear transformations of the functions were studied. The exponential and hyperbolic B functions provided the least mean squared residual in quantifying nodal conduction (8.6 +/- 10.8 ms2 and 10.8 +/- 13.9 ms2, respectively). The use of nonlinear function transformation into a linear representation caused loss of precision in the fit to the data in the case of the exponential function (18.3 +/- 22.2 ms2 versus 8.6 +/- 10.8 ms2, p less than 0.01) and, to a lesser extent, in the case of the hyperbolic B function (12.5 +/- 16.4 ms2 versus 10.8 +/- 13.9 ms2, P less than 0.05).