Background: Pulsed field ablation (PFA) is a novel form of ablation using electrical fields to ablate cardiac tissue. There are only limited data assessing the feasibility and safety of this type of ablation in humans. Methods: PULSED AF (Pulsed Field Ablation to Irreversibly Electroporate Tissue and Treat AF; https://www.clinicaltrials.gov ; unique identifier: NCT04198701) is a nonrandomized, prospective, multicenter, global, premarket clinical study. The first-in-human pilot phase evaluated the feasibility and efficacy of pulmonary vein isolation using a novel PFA system delivering bipolar, biphasic electrical fields through a circular multielectrode array catheter (PulseSelect; Medtronic, Inc). Thirty-eight patients with paroxysmal or persistent atrial fibrillation were treated in 6 centers in Australia, Canada, the United States, and the Netherlands. The primary outcomes were ability to achieve acute pulmonary vein isolation intraprocedurally and safety at 30 days. Results: Acute electrical isolation was achieved in 100% of pulmonary veins (n=152) in the 38 patients. Skin-to-skin procedure time was 160±91 minutes, left atrial dwell time was 82±35 minutes, and fluoroscopy time was 28±9 minutes. No serious adverse events related to the PFA system occurred in the 30-day follow-up including phrenic nerve injury, esophageal injury, stroke, or death. Conclusions: In this first-in-human clinical study, 100% pulmonary vein isolation was achieved using only PFA with no PFA system–related serious adverse events.
Muscle metabolism was investigated in seven men during two 35 min cycling trials at 60% peak oxygen uptake, at 35 degrees C and 50% relative humidity. On one occasion, exercise was preceded by whole-body cooling achieved by immersion in water during a reduction in temperature from 29 to 24 degrees C, and, for the other trial, by immersion in water at a thermoneutral temperature (control, 34.8 degrees C). Pre-cooling did not alter oxygen uptake during exercise (P > 0.05), whilst the change in cardiac frequency and body mass both tended to be lower following pre-cooling (0.05 < P < 0.10). When averaged over the exercise period, muscle and oesophageal temperatures after pre-cooling were reduced by 1.5 and 0.6 degrees C respectively, compared with control (P < 0.05). Pre-cooling had a limited effect on muscle metabolism, with no differences between the two conditions in muscle glycogen, triglyceride, adenosine triphosphate, creatine phosphate, creatine or lactate contents at rest, or following exercise. These data indicate that whole-body pre-cooling does not alter muscle metabolism during submaximal exercise in the heat. It is more likely that thermoregulatory and cardiovascular strain are reduced, through lower muscle and core temperatures.
Even in this relatively young, healthy, non-clinical sample, sleep complaints and primary insomnia with subsequent excess daytime sleepiness were common. There were clear associations between many personal and lifestyle factors-such as depression, long work hours, alcohol dependence, and rotating shift work-and sleep problems or excessive daytime sleepiness.
Moi Chow. Respiratory events and periodic breathing in cyclists sleeping at 2,650-m simulated altitude. J Appl Physiol 92: 2114-2118, 2002; 10.1152/japplphysiol.00737. 2001.-We examined the initial effect of sleeping at a simulated moderate altitude of 2,650 m on the frequency of apneas and hypopneas, as well as on the heart rate and blood oxygen saturation from pulse oximetry (Sp O 2 ) during rapid eye movement (REM) and non-rapid eye movement (NREM) sleep of 17 trained cyclists. Pulse oximetry revealed that sleeping at simulated altitude significantly increased heart rate (3 Ϯ 1 beats/min; means Ϯ SE) and decreased Sp O 2 (Ϫ6 Ϯ 1%) compared with baseline data collected near sea level. In response to simulated altitude, 15 of the 17 subjects increased the combined frequency of apneas plus hypopneas from baseline levels. On exposure to simulated altitude, the increase in apnea was significant from baseline for both sleep states (2.0 Ϯ 1.3 events/h for REM, 9.9 Ϯ 6.2 events/h for NREM), but the difference between the two states was not significantly different. Hypopnea frequency was significantly elevated from baseline to simulated altitude exposure in both sleep states, and under hypoxic conditions it was greater in REM than in NREM sleep (7.9 Ϯ 1.8 vs. 4.2 Ϯ 1.3 events/h, respectively). Periodic breathing episodes during sleep were identified in four subjects, making this the first study to show periodic breathing in healthy adults at a level of hypoxia equivalent to 2,650-m altitude. These results indicate that simulated moderate hypoxia of a level typically chosen by coaches and elite athletes for simulated altitude programs can cause substantial respiratory events during sleep. pulse oximetry; apnea; hypopnea RECENT STUDIES ON THE USE of altitude by athletes suggest that the best effect on subsequent physical performances may be gained by sleeping in a moderately hypoxic condition (equivalent to altitudes of ϳ2,200-3,000 m) while training close to sea level (21,22). The response to this "live high, train low" approach varies widely between individuals, with some athletes showing substantial performance gains and others showing no effect or even a negative outcome (7). Athletes spend a substantial amount of time asleep while exposed to the live high, train low stimulus (3), and the respiratory events during their sleep time increase as altitude increases (28). However, substantial differences appear to exist between individuals in both the magnitude of this effect and the altitude of onset (2,8, 39). Although sleep disturbance has been shown to decrease subsequent physical work capacity and increase the self-perception of fatigue (1), no studies have monitored the sleep physiology of athletes undergoing a live high, train low program.Hyperventilation is among the first physiological adjustments to an acute increase in altitude in an attempt to compensate for the reduced PO 2 (10, 30). Episodes of hyperventilation may be separated by intervals of hypopnea or apnea. When respiratory events are cyclic and conta...
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