Simple mental and verbal activities markedly affect HRV through changes in respiratory frequency. This possibility should be taken into account when analyzing HRV without simultaneous acquisition and analysis of respiration.

The presence of baroreceptor-induced RR oscillations is evidence of functional, although incomplete, autonomic reinnervation.

Background — It is well established that a depressed baroreflex sensitivity may adversely influence the prognosis in patients with chronic heart failure (CHF) and in those with previous myocardial infarction. Methods and Results — We tested whether a slow breathing rate (6 breaths/min) could modify the baroreflex sensitivity in 81 patients with stable (2 weeks) CHF (age, 58±1 years; NYHA classes I [6 patients], II [33], III [27], and IV [15]) and in 21 controls. Slow breathing induced highly significant increases in baroreflex sensitivity, both in controls (from 9.4±0.7 to 13.8±1.0 ms/mm Hg, P <0.0025) and in CHF patients (from 5.0±0.3 to 6.1±0.5 ms/mm Hg, P <0.0025), which correlated with the value obtained during spontaneous breathing ( r =+0.202, P =0.047). In addition, systolic and diastolic blood pressure decreased in CHF patients (systolic, from 117±3 to 110±4 mm Hg, P =0.009; diastolic, from 62±1 to 59±1 mm Hg, P =0.02). Conclusions — These data suggest that in patients with CHF, slow breathing, in addition to improving oxygen saturation and exercise tolerance as has been previously shown, may be beneficial by increasing baroreflex sensitivity.

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Aims Pulmonary vein (PV) isolation is a curative treatment for patients with atrial fibrillation. The aim of this study was to evaluate prospectively the effects of adenosine administration on the PV activity and atrio-venous conduction after PV isolation. Methods and results Twenty-nine patients (21 m; age: 55 ± 8 years) were submitted to ostial PV isolation guided by basket catheter recordings. After successful isolation, the effects of a 12 mg intravenous bolus of adenosine were tested in 62 PVs. In 22/62 PVs (35%), left atrium (LA)-to-PV conduction was transiently (16.6 ± 7.1 s, range: 3.8-27.9 s) or permanently (3 PVs) restored in response to adenosine administration. The prevalence of this phenomenon was 39% in left superior PVs, 43% in right superior PVs, and 22% in left inferior PVs (p = 0.365). It occurred more frequently in the presence of dissociated PV activity (11/15 PVs, 73% vs. 11/47 PVs, 23%; p = 0.002), whereas it was not influenced by the median duration of the radiofrequency current (RFC) delivery for each ) min vs. 16 (IQR: 11-24) min: p = 0.636]. A lengthening or shortening of the LA-PV conduction time was observed at LA-PV conduction appearance and disappearance in 36% and 55% of the cases, respectively. Further RFC applications (median: 5.5 min, IQR: 4-11 min) at the residual conduction breakthrough(s) indicated by the basket catheter recordings definitively eliminated adenosineinduced recovery of LA-PV conduction in all cases. Finally, when present, intrinsic PV discharge was invariably depressed by adenosine administration. Conclusions Adenosine may transiently or permanently re-establish LA-PV conduction after apparently successful PV isolation. This phenomenon is abolished by additional RFC delivery. However, its possible influence on the clinical results of PV ablation must be evaluated by properly designed, randomized studies.

1. To assess the effects of acute exposure to high altitude on baroreceptor function in man we evaluated the effects of baroreceptor activation on R-R interval and blood pressure control at high altitude. We measured the low-frequency (LF) and high-frequency (HF) components in R-R, non-invasive blood pressure and skin blood flow, and the effect of baroreceptor modulation by 0. 1-Hz sinusoidal neck suction. Ten healthy sea-level natives and three high-altitude native, long-term sea-level residents were evaluated at sea level, upon arrival at 4970 m and 1 week later.2. Compared with sea level, acute high altitude decreased R-R and increased blood pressure in all subjects [sea-level natives: R-R from 1002+/-45 to 775+/-57 ms, systolic blood pressure from 130+/-3 to 150+/-8 mmHg; high-altitude natives: R-R from 809+/-116 to 749+/-47 ms, systolic blood pressure from 110+/-12 to 125+/-11 mmHg (P<0.05 for all)]. One week later systolic blood pressure was similar to values at sea level in all subjects, whereas R-R remained elevated in sea-level natives. The low-frequency power in R-R and systolic blood pressure increased in sea-level natives [R-R-LF from 47+/-8 to 65+/-10% (P<0.05), systolic blood pressure-LF from 1.7+/-0. 3 to 2.6+/-0.4 ln-mmHg2 (P<0.05)], but not in high-altitude natives (R-R-LF from 32+/-13 to 38+/-19%, systolic blood pressure-LF from 1. 9+/-0.5 to 1.7+/-0.8 ln-mmHg2). The R-R-HF decreased in sea-level natives but not in high-altitude natives, and no changes occurred in systolic blood pressure-HF. These changes remained evident 1 week later. Skin blood flow variability and its spectral components decreased markedly at high altitude in sea-level natives but showed no changes in high-altitude natives. Neck suction significantly increased the R-R- and systolic blood pressure-LF in all subjects at both sea level and high altitude.3. High altitude induces sympathetic activation in sea-level natives which is partially counteracted by active baroreflex. Despite long-term acclimatization at sea level, high-altitude natives also maintain active baroreflex at high altitude but with lower sympathetic activation, indicating a persisting high-altitude adaptation which may be genetic or due to baroreflex activity not completely lost by at least 1 year's sea-level residence.

In normal humans, electroanatomic mapping of SR identifies a typical and reproducible propagation pattern during SR. Bachmann's bundle plays the most important role in interatrial propagation. Atria are activated simultaneously by sinus impulse for a relevant portion of the systolic time interval.

Parasympathetic reinnervation depends on the surgical technique: because bicaval surgery cuts all sympathetic and parasympathetic nerves, regeneration might be stimulated similarly in both branches. Standard surgery cuts only approximately 50% of sympathetic fibers; most recipient parasympathetic axons remain intact, hence their regeneration might not be stimulated.