Forty-eight hour Holter monitoring was undertaken of 16 male elite middle- and long-distance runners, age 25 +/- 3 years, with peak oxygen uptake 4.83 +/- 0.43 1 O2/min or 73.0 +/- 3.9 ml O2/kg/min. The athletes had pronounced bradycardia during the night-time, with heart rate calculated from four RR intervals 2 s. Of those, 10 runners had sinus pauses exceeding 2 s, the longest being 3.06 s. Three runners had AV block II, two with Mobitz type 1, and one with both Mobitz type 1 and 2. Autonomic function was estimated by time domain and power spectral analysis of heart rate variability. The runners were compared with a control group of 13 sedentary or moderately active subjects. The runners had a mean of 14 b.p.m. lower heart rate at night than the controls. The runners had higher heart rate variability in all spectral bands. In the time domain pNN50 and rMSSD, which are considered to reflect strongly vagal tone, were markedly higher in the runners than the controls. The findings suggest that an increased parasympathetic tone might at least partly explain the pronounced resting sinus bradycardias found in endurance-trained runners.

Pronounced resting bradycardia in male elite runners is associated with high heart rate variability.

Development of QRS detection algorithm designed for wearable cardiorespiratory system

https://www.heartrhythmjournal.com/article/S1547-5271(07)00598-X/pdf

Impact of rate-modulated pacing on quality of life and exercise capacity—Evidence from the Advanced Elements of Pacing Randomized Controlled Trial (ADEPT)

The development of implantable technology for cardiac rhythm management remains one of the seminal achievements of the second half of the 20th century. The modern era of cardiac pacing began in 1958, when Elmqvist and Senning1 implanted the first cardiac pacemaker by thoracotomy in a human, and Furman and Robinson2 implanted the first endocardial lead.

The focus of development of cardiac pacing has changed over the last several decades. In the 1950s through 1970s, the emphasis was on the development of more reliable power sources and leads. By the end of the 1970s, the power source problems had been largely overcome, and efforts focused on mimicking the normal physiology of cardiac contraction.

In the 1980s, in the United States, the focus on normal physiology led to the nearly universal application of dual-chamber pacing to restore atrioventricular (AV) synchrony in patients with sinus rhythm. As sensor technology improved in the 1980s and 1990s,3,4 the same physiological focus spurred the advent and generalization of sensor-driven, rate-modulated pacing to restore chronotropic competence. By the early 1990s, there were lessons from physiology and an emerging body of evidence from observational epidemiological studies.5,6 Indeed, some pacemaker physicians believed that randomized trials in pacing might not be necessary to demonstrate incremental gains in prevention of clinical events and improvement of quality of life with atrial-based pacing.7

It is certainly true that for many hypotheses, randomized trials are neither necessary nor desirable. For example, it would have been unethical to conduct randomized trials of cardiac pacing for the treatment of Stokes-Adams-Morgagni attacks because the benefit was so large.8 As a result of the evolution of progressively more sophisticated technologies, the most plausible effect sizes have become small to moderate, or between a 15% and 30% relative reduction in risk. Such effects, …

Evidence base for pacemaker mode selection: from physiology to randomized trials.

Over the last two decades the diagnostic tools used in sleep medicine have developed enormously, making it possible to study the interaction of sleep-related breathing disorders (SRBD) with cardiovascular function and the autonomic nervous system, as well as the effects of SRBD on a variety of physiological processes during wakefulness. Different modes of nasal ventilation are now available, allowing all forms of SRBD to be treated. If early diagnosis and treatment are provided, the acute and long-term sequelae of SRBD can be prevented. In addition to the care and treatment of patients with severe obstructive sleep apnoea syndrome (OSAS), future patient management will need to focus on patients with milder forms of obstructive sleep apnoea (OSA). In particular, the consequences of SRBD on cardiac arrhythmias, arterial hypertension and hypersomnolence are discussed, considering epidemiological, clinical, diagnostic and therapeutic aspects. Some economical issues arising from SRBD are also discussed, and the authors conclude that a Europewide programme for early detection, treatment and prevention of SRBD is required. This could make a large contribution to the reduction of cardiovascular morbidity and mortality and also reduce the incidence of "human error catastrophes" due to hypersomnolence.

https://erj.ersjournals.com/content/erj/8/9/1572.full.pdf

Manifestations and consequences of obstructive sleep apnoea

In order to establish normal limits for mean 24 h heart rate ( H R ¯ t and pauses, 24 h ambulatory ECG recordings from 260 healthy subjects 40–79 years of age were analysed.

The H R ¯ 24h varied from 53 to 95 beats/min (mean±2 s.d.: 74±I8 beats/min). The minimal H R ¯ t varied from 36 to 78 beats/min (mean± 2 s.d.: 56 ±16 beats/min). Analysis of variance showed an additive effect of smoking, sex, leisure-time physical activity and age on both H R ¯ t, and the effect of the three first factors was statistical significant at the 1% level for both heart rate variables. The males, the non-smokers and the physically active subjects had a lower H R ¯ 24h and a lower minimal H R ¯ t than females, smokers and passive subjects. Older subjects had a lower H R ¯ t was non-significant.

A total of 77 subjects (30%) had a pause (R-R interval≥1500 ms), but in only 12 (5%) did the pause exceed 1750 ms with the longest pause measuring 2040 ms. Further analysis of the longest pause in each of the 77 subjects with pauses showed that 46 of the longest pauses occurred at night following a gradual decrease in the R-R intervals for a few beats (‘post-acceleration pauses’). In 12 subjects the longest pause was caused by sinus arrest, and in nine cases a blocked atrial premature beat was thought to be present. Wenckebach A- V block was seen in only two subjects.

It is concluded that sex, age, smoking and leisure-time physical activity are all factors that have to be considered for a thorough evaluation of heart rate variables in the 24 h ambulatory ECG.

Mean 24 hour heart rate, minimal heart rate and pauses in healthy subjects 40–79 years of age

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Mean 24 hour heart rate, minimal heart rate and pauses in healthy subjects 40–79 years of age