2021-04-09 08:00:00
The heartbeat originates in a small area a few millimeters in diameter, the sinus node, located in the right atrium. There, specialized cells are programmed to send the electrical impulse that will trigger the contraction of the heart. This rhythm varies throughout the day, depending on the activity. An effort to climb a staircase? He accelerates. It’s time to sleep ? He slows down. Everything is automatic and placed under the control of the autonomic nervous system.
The cardiac frequency, i.e. the number of beats per minute, should remain within a range considered normal depending on age and physical activity. Sometimes, however, under the effect of stress, fatigue, or even illness, this rhythm becomes disrupted.
How does the heartbeat work?
1. The electrical impulse starts from the sinus node, at the top of the right atrium then travels to the left atrium, giving the signal for their contraction.
2. The electric current then crosses the atrioventricular node, at the junction between the atria and the ventricles, and gives the signal to the ventricles to contract in turn.
This circuit is under the control of the autonomic nervous system, beyond our control. During the day, it is the sympathetic nervous system that dominates: it accelerates the heart rate according to physical activity and stress. During the night, the parasympathetic nervous system slows the heart rate.
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What is the correct resting heart rate?
A baby’s heart beats very fast. His heart rate then slows, as he grows and as a result of physical activity:
- 120-160 beats per minute (b/min) in newborns,
- 100-120 b/min in children,
- 80-85 b/min chez l’adolescent,
- 80 b/min in sedentary adults,
- 50 b/min in athletic adults,
- 60-80 b/min in seniors.
Simply count the number of beats per minute to get his heart rate. There are three ways to take your pulse:
- By placing three fingers (the index, middle and ring finger) along the carotid arteryat the level of the neck.
- By placing two fingers (index and middle finger) on the radial arteryat the wrist.
- Using a connected watch which gives the heart rate. Some even have an electrocardiogram function.
Heartbeat too slow: when should you worry?
Below 60 beats per minutethe heart is in a situation of bradycardia. It is not necessarily pathological. Well-trained athletes, such as marathon runners, have a naturally slow heart rate, around 40 beats per minute at rest.
Also, it is normal for the heart rate to drop during sleep… until a certain point. “At night, the heart can slow down to 35 beats per minute without any problem. But if it makes prolonged pauses of three to four seconds, there is a risk of syncope or even cardiac arrest”, observes Professor Jacques Mansourati, cardiologist at Brest University Hospital.
What signs should alert?
A slow heart, associated with a shortness of breath even at rest and feeling unwell, reveals an underlying pathology.
What are the risks ?
“When the flow is too low, the heart no longer ejects enough blood to the organs. Within a few days, respiratory signs can set in due to heart failure,” explains Professor Mansourati.
What exams?
To identify the cause of this bradycardia, various examinations are necessary.
What solutions?
certain drugs, such as beta-blockers prescribed for high blood pressure, can slow the heart rate. The doctor can adjust the treatment if necessary.
As a last resort, the patient can be fitted with a pacemaker. This pacemaker is inserted under the collarbone, between the skin and the muscle. One or more probes, making it possible to conduct the electrical impulse, are introduced into the veins to the heart.
Heartbeat too fast: palpitations to watch out for
We are talking about tachycardia over 100 beats per minute. Stress, anxiety, excessive consumption of stimulants such as coffee or an attack of fever can explain this acceleration of the heart rate. If the phenomenon occurs too often, you should talk to your doctor.
Professor Mansourati details the procedure to follow: “The electrocardiogram will make it possible to verify that the heartbeat does indeed start from the sinus node and, in this case, it is often benign. But the tachycardia can come from different parts of the heart.
If it is of ventricular origin, it is more serious. Various examinations will make it possible to know the origin and the frequency of it. A blood test may reveal hyperthyroidism, anemia or other causes.”
What signs should alert?
Tachycardia makes the heart feel like racing. These palpitations are sometimes accompanied by a dizziness and a shortness of breath.
What risks?
Sinus tachycardias, related to stress, are punctual and benign. But other forms of tachycardia overstrain the heart. In the extreme, it leads to heart failure which can be serious. In a person whose coronary arteries are in poor condition, “tachycardia causes cardiac suffering which can end in a heart attack”, warns the cardiologist.
What solutions?
In the simplest cases, physical activity practiced on a regular basis will allow, according to Professor Mansourati “better control of the autonomic nervous system”. The heart rate will return to a normal, calmer rhythm. “It is better to privilege theendurance activities such as walking, running, cycling or swimming”, specifies the cardiologist.
In some cases, a antiarrhythmic treatment is needed to slow down and stabilize the heart rate. Several types of drugs can be used: beta-blockers, calcium channel blockers, flecainide or amiodarone. This last drug is very effective, but it is also the one that causes the most side effects.
In people whose tachycardia is of ventricular origin, and who are at risk of sudden death, the solution lies in pose of a defibrillateur implantable. A box, placed under the skin, is connected to the heart by a probe. If necessary, the device sends an electric shock to restore a normal heart rhythm.
Irregular heartbeat: consider atrial fibrillation
It happens that the heartbeats become, for a moment, anarchic. These extrasystoles due to an electrical conduction defect are, in the majority of cases, not serious. In the elderly, you have to think about the fibrillation atriale. “It is estimated that 10% of people over 80 have it,” says Dr. Mansourati.
What signs should alert?
Acceleration may occur abruptly, with irregular beats. Consequences: shortness of breath, malaise or fatigue.
What risks?
These disorders make contractions of the atria ineffective, which can promote formation of a clot and cause a cerebrovascular accident (CVA). As blood flow is reduced, there is a risk of heart failure.
What solutions?
If the doctor decides that the symptoms are not worrying, atrial fibrillation only requires a simple surveillance.
Prescribing blood-thinning medication helps prevent the risk of stroke. But in some cases it is necessary to remove the faulty electrical circuit, causing fibrillation. “The ablation can be done by means of a radiofrequency probe (heat cautery) or a cryotherapy balloon (cold therapy). The probes are introduced through the femoral vein and go up to the heart” , explains Professor Mansourati. The intervention is usually done under local anesthesia. Hospitalization is very short, two to three days maximum. This treatment is effective in 70 to 80% of cases. In case of relapse, the procedure is repeated.
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