- Even though arrhythmias may not pose an immediate threat to life, they may indicate the presence of some disease. It means complete health check must be done in those with such a problem.
- In young men, athletes, episodes of sinus bradycardia (abnormal slowdown in heart rate) may occur. In most cases, it is a safe condition.
- If nighttime arrhythmias occur in the presence of other heart condition, it is a reason to worry. Further, consultations with a sleep specialist and cardiologist are needed.
- Heart attack or other cardio problems are more common in the morning when REM sleep dominates. It may say about issues of the autonomic nervous system.
- Obstructive sleep apnea often causes cyclic changes in heart rhythm. These changes in heart rate during the night may be dangerous for those living with heart problems.
REM Sleep and the Heart
As we go to bed, we slip into the so-called non-REM sleep. Slowly moving from stage one to three. The third stage is a deep sleep stage. After staying in deep state for some time, we move to REM sleep. REM or Rapid eye movement is a time when we start to dream.
During the night several cycles of non-REM and REM sleep are repeated. When sleeping, all our bodily activities are tightly controlled by the autonomous nervous system. While sleeping, some brain areas are more active than others. With cyclic sleep comes the cyclic changes in our body.
When we are sleeping, so many things are happening to the heart and body.
Though physical activity is minimal in sleep, many metabolic processes happen vigorously. It is time for rejuvenation of the body, time for re-organization of memories, and much more. Though we are not aware, sleep is a much powerful thing. So many things are happening in the auto mode.
As we slowly move to deep sleep (stage four of non-REM sleep), our body temperature comes down; the parasympathetic nervous system becomes dominated. It means that heart and respiration also slow down, blood pressure comes down a bit.
When we switch to REM mode, the sympathetic system becomes more active. It means a higher respiratory rate, higher heart rate. It is entirely different from non-REM sleep.
In many people, heart rate may go down too much during non-REM sleep. It is called sinus bradycardia, a kind of arrhythmia. However, it is a benign condition and does not need treatment. Things get normal when the body switches to REM sleep.
In some people, changes between non-REM and REM sleep may not go very smoothly. Few of them may continue to have episodes of bradycardia (slow heartbeat), or even missed heartbeats even in REM sleep. On the other hand, other may feel sudden burst in heart rate (tachycardia).
These shifting of gears by heart and nervous system may be bad for those living with diseases. Sometimes, arrhythmia during the night may say about the undiagnosed illness. It could be some disease of the heart, or it could be due to a sleep disorder. Arrhythmia while sleeping may also cause heart issues like heart attack, worsening of congestive heart failure.
How can a person know if he/she has episodes of arrhythmia during the night?
Holster monitoring is perhaps the only way to diagnose such condition. In most cases, a person may not have any problem during the day. So a physician would attach ECG electrodes, and monitor heart activity continually, even when sleeping (it is called holster).
Sleep apnea and cardiac arrhythmia
This subject needs separate discussion, as changes in heart rhythm are more common when sleep pattern is disturbed. Obstructive sleep apnoea (OSA) is one of the most common sleep issues.
In OSA, due to overweight, lack of exercise, other anatomical defects, upper airway relaxes too much while sleeping. The over-relaxed upper airway may block the breathing process. Frequent and loud snoring is its most common symptom. Other symptoms of apnea are morning headaches and fatigue.
In OSA, when a person is in sleep, airway gets blocked. Fortunately, when it occurs, the brain awakes a person. Consequently, the matter is corrected. However, condition disturbs sleep a lot, as the process is repeated several times during a night.
In severe cases of sleep apnoea, there are episodes of acute hypoxia (lack of oxygen in the blood) in the night. When severe hypoxia occurs, the heart tries to compensate for low oxygen by changing its rhythm. Thus in people with apnea, there are periodic episodes of arrhythmia.
In most cases, arrhythmia associated with OSA is not life-threatening. However, things may differ for those living with medical conditions. In those with atherosclerosis, it may lead to heart attack.
OSA is usually diagnosed with the help of a special device that monitors various vitals while sleeping- it is called polysomnography.
Treatment of OSA may help prevent episodes of heart arrhythmia related to it. Most effective treatment of OSA is CPAP (continuous positive airway pressure). In CPAP higher amount of air is provided to the person while sleeping. The person has to sleep wearing a mask that is connected to the apparatus.
In conclusion, it is essential to understand the changes in heart rhythm that occur during the night. It is necessary to know how sleep cycles affect the heart. After all, heart attacks are quite common in the morning, when REM sleep is dominant.
- Janssens W, Willems R, Pevernagie D, Buyse B. REM sleep-related bradyarrhythmia syndrome. Sleep Breath. 2007;11(3):195-199. doi:10.1007/s11325-007-0105-2
- Gula LJ, Krahn AD, Skanes AC, Yee R, Klein GJ. Clinical relevance of arrhythmias during sleep: guidance for clinicians. Heart. 2004;90(3):347-352. doi:10.1136/hrt.2003.019323
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