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Sleep-related myocardial ischemia and sleep structure in patients with obstructive sleep apnea and coronary heart
Insights
Patients with coronary heart disease and obstructive sleep apnea face cardiac risks from nocturnal ischemia linked to oxygen desaturation. These ischemic events disrupt sleep and activate the central nervous system, indicating a need for sleep apnea screening.
Area of Science:
- Cardiology
- Sleep Medicine
- Pulmonology
Background:
- Coronary heart disease (CHD) patients with obstructive sleep apnea (OSA) have increased cardiac risk from nocturnal myocardial ischemia due to oxygen desaturation.
- Sleep fragmentation in OSA patients, caused by central nervous system (CNS) arousal from obstructive apneas, may also be triggered by nocturnal myocardial ischemia.
Purpose of the Study:
- To investigate the relationship between obstructive sleep apnea, coronary heart disease, and nocturnal myocardial ischemia.
- To assess the impact of apnea-associated ischemia on sleep structure and CNS activation.
- To evaluate the efficacy of nitrate therapy in reducing ischemic episodes in these patients.
Main Methods:
- Studied 14 patients with OSA and CHD, and 7 with OSA but no CHD.
- Performed overnight polysomnography with simultaneous six-lead ECG recordings.
- Administered sustained-release nitrate in a double-blinded crossover design to assess its effect on ischemic episodes.
Main Results:
- 144 episodes of nocturnal myocardial ischemia were identified in 6 subjects, with 85.4% linked to apneas and oxygen desaturation.
- Ischemic episodes predominantly occurred during REM sleep (77.8%), with significantly lower oxygen saturation during apnea-associated ischemia (77.3% vs. 93.1%).
- Nitrate administration did not reduce ischemic episodes; ischemia itself caused significant increases in sleep arousals and sleep fragmentation.
Conclusions:
- Patients with CHD and OSA are at risk from apnea-associated ischemia, which triggers CNS activation and further sleep fragmentation.
- Nocturnal myocardial ischemia can disrupt sleep architecture independently of apneas.
- Screening for sleep apnea is recommended for patients with nocturnal ischemia, even if nitrate therapy is ineffective.
Study Objectives:
Patients with coronary heart disease (CHD) and obstructive sleep apnea may have an increased cardiac risk due to nocturnal myocardial ischemia triggered by apnea-associated oxygen desaturation. Sleep structure in patients with obstructive sleep apnea is fragmented by activation of the central nervous system (CNS) (arousal) due to obstructive apneas. Nocturnal myocardial ischemia may lead to activation of the CNS as well.
Patients:
Fourteen patients with obstructive sleep apnea and CHD disease and seven patients suffering from obstructive sleep apnea without CHD were studied. Overnight sleep studies and simultaneous six-lead ECG recordings were performed. In addition, sleep studies and ECG recordings were performed with administration of a sustained-release nitrate in these patients in a double-blinded crossover design.
Results:
Analysis of three nights' recordings revealed 144 episodes of nocturnal myocardial ischemia in six subjects. Five patients had underlying CHD and one patient exhibited diffuse wall defects of the coronary arteries; also, 85.4% of ischemic episodes were concomitant with apneas and oxygen desaturation > 3%, and 77.8% of ischemic episodes occurred during rapid eye movement (REM) sleep, although total amount of REM sleep was only 18% of total sleep time. Mean oxygen saturation was significantly lower (p < 0.05) during apnea-associated ischemic episodes than during nonapnea-associated ischemia (77.3% vs 93.1%). Nitrate administration did not reduce ischemic episodes. Sleep architecture (macrostructure) exhibited a reduction in sleep stages non-REM 3 and 4 and REM sleep. Comparing the microstructure of sleep (arousals) within episodes with and without ischemia but similar criteria like sleep stage, apnea activity, and oxygen saturation, we found significantly more (p < 0.01) and severe (p < 0.001) arousals during periods with myocardial ischemia than during control episodes. In addition, microstructure of sleep was disturbed by myocardial ischemia itself in absence of apneas.
Conclusion:
It is concluded that patients with CHD and obstructive sleep apnea are endangered by apnea-associated ischemia and that these ischemic episodes lead to activation of the CNS and additional fragmentation of sleep. Patients with nocturnal ischemia should be screened for underlying sleep apnea even if nitrate therapy fails.