Trial Information

Prevalence, Incidence and Clinical Characteristics of Sleep Disordered Breathing in Patients With Stable Chronic Heart Failure

Chronic heart failure is a complex clinical syndrome that can result from any structural or
functional cardiac or non-cardiac disorder that impairs the ability of the heart to respond
to physiological demands for increased cardiac output. Chronic heart failure is
characterised by symptoms such as exertional breathlessness and fatigue, and signs of fluid
retention as well as signs associated with the underlying cardiac disorder. Patients with
chronic heart failure suffer from reduced quality of life and a significantly higher risk of
morbidity and mortality.

There is cumulating evidence of a high prevalence of sleep breathing disorders in both
patients with acute and chronic heart failure. Most of these reports, however, suffer from
important limitations including small sample size, retrospective study design, and/or use of
pulse-oximetry or cardio-respiratory polygraphy to screen for sleep disordered breathing
rather than full-night polysomnography. Hence, previous studies may have underestimated the
full scale of concomitant sleep disordered breathing in patients with chronic heart failure.
Furthermore, to the best of our knowledge, there is no report on the incidence of sleep
disordered breathing in patients with chronic heart failure.

In this context the presence of sleep disordered breathing in patients with chronic heart
failure has important prognostic relevance. Pathophysiological effects of sleep apnea
include intermittent hypoxia, sympathetic hyperactivity, systemic inflammation, and sleep
fragmentation. These factors may contribute to the worsening of cardiac function and explain
the reportedly higher risk of cardiac morbidity and mortality in patients with both chronic
heart failure and concomitant sleep disordered breathing. Accordingly, the aims of the
present study are three-fold. First, to investigate the prevalence of sleep breathing
disorders in patients with stable moderate-to-severe chronic heart failure using the
diagnostic gold standard of full-night-polysomnography. Second, to assess the two-year
incidence of sleep disordered breathing in patients with chronic heart failure. Third, to
identify potential risk factors associated with the presence or absence of sleep disordered
breathing in patients with chronic heart failure. The latter will be assessed by using lung
function measurements, hemodynamic parameters, and laboratory markers of neurohumoral
activation, systemic inflammation, and endothelial function in patients with chronic heart
failure.

For this purpose 200 patients with stable moderate-to-severe chronic heart failure will be
studied during a 2 year-period. Patients with chronic heart failure will be screened for
eligibility during their regular visits at 4 independent heart failure outpatients clinic in
Vienna. Eligible patients will undergo full-night-polysomnography, lung function testing,
non-invasive hemodynamic monitoring, a six minute-walking-test, and laboratory measurements
at 6 months intervals for a total of 2 years (4 visits).