Unconsciousness is a state where a person loses awareness and becomes unresponsive to stimuli. It can occur due to several reasons like injury, illness, drug effects, fainting etc. When a person becomes unconscious, many of the body’s vital functions like breathing and heartbeat continue to work. So does the heart continue beating when a person is unconscious? Let’s find out.
Summary
Yes, the heart typically continues to beat and pump blood when a person is unconscious. The autonomic nervous system, which controls involuntary functions like heartbeat, breathing, and digestion, is usually unaffected by the loss of consciousness. The heart rate and rhythm may change in some cases of unconsciousness, but the heart continues beating to maintain circulation and supply oxygenated blood to the body’s tissues and organs.
What happens to the body when unconscious?
Unconsciousness results from disruption of the reticular activating system (RAS) in the brain stem that regulates wakefulness and sleep. When the RAS is disrupted, it cannot send wake-up signals to the cerebral cortex, which is the part of the brain responsible for thought, memory, awareness and consciousness.
During unconsciousness, the cerebral cortex shuts down, which is why the person loses awareness, stops responding, and becomes unarousable. But other key functions of the body controlled by the autonomic nervous system and brain stem continue to work.
- Breathing – Medulla oblongata in the brain stem regulates breathing
- Heartbeat – Cardiovascular centers in the medulla oblongata and hypothalamus regulate heart rate and rhythm
- Digestion – Digestive processes are controlled by the autonomic nervous system
- Temperature regulation – Hypothalamus regulates body temperature
This allows vital organs like the heart and lungs to keep functioning even though the higher brain centers are impaired during unconsciousness. The heart continues pumping and circulating oxygenated blood throughout the body to maintain the body’s vital functions.
Why does the heart keep beating?
The heart has its own intrinsic system that generates electrical impulses to stimulate heart muscle contractions. This intrinsic conduction system contains the:
- Sinoatrial (SA) node – natural pacemaker of the heart
- Atrioventricular (AV) node
- Bundle of His
- Bundle branches
- Purkinje fibers
The SA node normally initiates electrical signals that travel through this specialized conduction system and cause the organized contraction of heart muscles that pumps blood. Even without input from the autonomic nervous system, the SA node would initiate heartbeats at around 40-60 beats per minute. This intrinsic rhythm from the SA node is what maintains the heartbeat when unconscious.
Additionally, the autonomic nervous system has some influence over heart rate through sympathetic and parasympathetic innervation of the heart. But the intrinsic SA node pacemaker activity is sufficient to drive the heartbeat even if autonomic input is disrupted during unconsciousness.
Heart rate changes during unconsciousness
Though the heart continues beating while unconscious, its rate and rhythm may change compared to the normal conscious state.
When unconscious:
- Heart rate may slow down due to parasympathetic dominance.
- Conversely, heart rate may increase if sympathetic tone is high.
- The heartbeat may become irregular in some cases.
The exact changes depend on the cause of unconsciousness and impact on the cardiovascular control centers in the brain.
For example, vasovagal syncope leads to a transient increase in parasympathetic tone and decrease in heart rate. Seizures, stroke, hypoglycemia, and other conditions may also slow the heart rate during unconsciousness.
On the other hand, traumatic brain injury can increase sympathetic outflow and result in rapid heartbeat. Similarly, excited delirium due to drug intoxication or psychiatric causes can accelerate the heart rate.
Typical heart rate changes
| Cause of unconsciousness | Typical heart rate change |
|---|---|
| Vasovagal syncope | Bradycardia |
| Seizures | Bradycardia |
| Hypoglycemia | Bradycardia |
| Stroke | Bradycardia |
| Traumatic brain injury | Tachycardia |
| Excited delirium | Tachycardia |
Can the heart stop beating when unconscious?
Though very rare, the heart can sometimes stop beating while unconscious. This is called cardiac arrest.
Cardiac arrest during unconsciousness may occur due to:
- Profound bradycardia that progresses to asystole (complete cessation of heartbeat)
- Ventricular tachycardia that deteriorates to ventricular fibrillation
- Electromechanical dissociation where the heart’s electrical system fails to stimulate coordinated muscle contractions
- Structural cardiac defects that disrupt electrical conduction like heart blocks
- Sudden blood loss or inadequate blood flow to the brain that triggers dysrhythmias
Cardiac arrest will lead to death within minutes if untreated. Hence, cardiopulmonary resuscitation (CPR) and defibrillation are critical in unconscious patients with no pulse to restore heart function and circulation.
When to seek emergency care?
Most cases of transient unconsciousness are not life-threatening. But at times, it may signify an underlying medical emergency like:
- Stroke
- Head injury
- Seizure
- Heart attack
- Low blood sugar
- Allergic reaction
Prolonged unconsciousness or inability to arouse someone is always an emergency. Seek immediate medical care if the person:
- Does not regain consciousness within 1-2 minutes
- Has difficulty breathing
- Has no pulse
- Has seizures
- Vomited blood or blood in stools
- Has symptoms or evidence of head trauma
- Has chest pain, numbness or paralysis
Rapid evaluation and treatment are crucial to prevent complications like brain damage or even death in conditions like stroke, seizures, trauma, or cardiac arrest.
Conclusion
In most cases, the heart continues beating and pumping blood to the body’s vital organs when a person becomes unconscious. This prevents immediate death and provides opportunity for the cause to be treated. But rarely, the heart can stop during profound unconsciousness leading to cardiac arrest. Hence, prompt emergency care is warranted in prolonged unconsciousness to monitor heart rhythm, resuscitate if needed, and treat any underlying condition.