FROM OUR MONTH-LONG SERIES, "SWEET DREAMS SWEET HEARTS," FOR NATIONAL HEART HEALTH AWARENESS MONTH

Sleep health can have a hidden impact on heart health, especially as it relates to heart rhythms.

Heart rhythm problems

When a doctor listens for heart rhythms, it's to check on the overall health of the heart.

The heart's activity will speed up and slow down over the course of the day due to things like exercise, sleep, and emotional state. However, while the speed of one's pulse can elicit some concerns from a doctor, what they are also looking for is a normal sinus rhythm.

The normal sinus rhythm is one which sticks to the exact same rhythm at all times. 

However, the heart's rhythms may be found to vary from a normal pattern. These are called arrhythmias.

What are arrhythmias? 

Arrhythmias are forms of abnormal heart rhythms.

The heart may drop some parts of its beat, or it might add an additional beat, produce a murmur, even delay a beat or introduce one too early.

Palpitations may be quick heartbeats you feel quite suddenly and which have a characteristically awkward beat pattern, not at all like the normal heartbeat you are used to.

In any case, arrhythmias can be something people will live with for a long time without realizing it, or they may come on suddenly and with disastrous consequences.

Just because you have (and live with) an arrhythmia does not mean you are necessarily in danger; it is but one of a number of cardiac observational screenings used by doctors to measure overall heart health. 

The most common form of abnormal heart rhythm (or arrhythmia) is atrial fibrillation. Frequently referred to as AFib, this is an abnormal heart rhythm in which the upper chambers of the heart quicken during the contraction of the heart (the heartbeat) in a pattern that is out of synch with the lower chambers of the heart, leading to a pattern that is not in tune with normal sinus rhythm. 

What causes arrhythmias? 

Arrhythmias point to a problem with the electrical regulation of the heart by the cardiovascular system which can be caused by:

• Coronary artery disease
• Electrolyte (sodium, calcium, or potassium) imbalances in the bloodstream
• Injured tissues following a heart attack
• Certain kinds of medications
• Post-operative healing processes

During sleep, both your cardiovascular and nervous systems undergo circadian changes when you transition to and from sleep. In some sleep stages, the heart rate slows, whereas in others (such as REM sleep), the heart rate accelerates, and it's possible that it might follow an erratic, if temporary pattern, during that time. This is considered normal and nothing to worry about.

However, in people with known heart conditions, these shifts in rhythms can become amplified and troublesome. Often, you may not even feel the presence of arrhythmias, but in some cases, you may experience the following symptoms or sensations: 

• A slowed heartbeat
• Pauses between heartbeats
• Fluttering, pounding, or skipping heart rhythms
• Anxious feelings such as trouble breathing, stress sweating, or unexplained feelings of panic

What sleep disorders are related to heart rhythm problems? 

The presence of arrhythmias during sleep is not necessarily a bad thing. However, if arrhythmias that occur during sleep aren't related to normal cardiac patterns associated with sleep, there may be more cause for concern. 

• People who suffer from insomnia by whatever cause may be almost 30 percent more likely to suffer from atrial fibrillation.
• Patients with no known cardiac conditions, who participate in overnight sleep studies, can confirm both the presence of sleep apnea and arrhythmias like atrial fibrillation while under observation.
• The relationship between sleep apnea and arrhythmias is so strong that a person who has been found to experience erratic heartbeats during a period of heart monitoring may be asked to undergo a sleep study to rule out (or identify) a hidden case of sleep apnea, especially if they snore or have other symptoms.

Why is sleep apnea especially implicated in heart arrhythmias? When you experience a pause in breathing that lasts more than ten seconds, your blood oxygen begins to dip. This is known as hypoxia, and it is a common trigger for arrhythmias in people with sleep apnea.

Other concerning physiological changes during an episode of apnea include unhealthy increases in carbon dioxide levels in the bloodstream, a surge of stress hormones which inspire "fight-or-flight" behaviors in the heart muscles (such as palpitations), and dramatic changes in respiratory pressure.

Should you worry?

Take your cues from your physician. Most arrhythmias detected in sleep are harmless. Certain kinds of abnormal cardiac rhythms that occur during sleep are considered a normal part of the process of sleep.

However, they might also reveal an underlying heart or sleep disorder that should be investigated. Here are some points to ponder: 

• If you know you have some form of heart disease, arrhythmias that occur as you sleep should be observed and tracked by a cardiac specialist. 
• The most likely time that people suffer from sudden cardiac death or dangerous arrhythmias—such as ventricular tachycardia (referred to in layman's terms as V-tach)—is in the early morning hours, when one is waking up. These risks are related to significant changes in the tone of the heart muscle that take place during the transition between sleep and wakefulness. 
• Those with a diagnosis of obstructive sleep apnea (OSA) should be concerned about becoming predisposed to cardiac problems, as OSA (when untreated) can cause great variations in heart rates and rhythms during sleep. 
• Both forms of sleep apnea (central and obstructive) are commonly experienced in people who suffer from chronic congestive heart failure. These people are at higher risk for developing arrhythmias, which can be prevented by simply treating the apnea. 
• If you suffer from insomnia, you might need to have it checked out: sometimes, ongoing chronic insomnia that is resistant to treatment may be found to actually be hidden sleep apnea.

Sources

"Clinical relevance of arrhythmias during sleep: guidance for clinicians." Gula LJ, Krahn AD, Skanes AC, Yee R, Klein GJ. Heart. 2004;90(3):347-352. Retrieved from the Internet on February 2, 2018.

"Poor sleep may increase risk for irregular heart rhythms." American Heart Association. ScienceDaily, 14 November 2016. Retrieved from the Internet on February 2, 2018.