What causes a slow heart rate?

Patients with bradycardia usually have physiological, systemic and improper medication. Their bradycardia will not only cause sleep disorders and nausea and vomiting after long-term exercise, but they will also have systemic diseases. Severe cases may cause hyperthyroidism, hypothyroidism, influenza, jaundice, and increased intracranial pressure. Therefore, timely diagnosis is required.

Causes

It may be caused by physiological, systemic, drug-induced or cardiovascular disease.

1. Physiological: Normal people, especially athletes who participate in physical exercise for a long time or people who do heavy physical labor, may experience sinus bradycardia. Sleepiness and fear can also cause temporary bradycardia. For example, some techniques such as compressing the eyeball, pressing the carotid sinus, vomiting, and vasoinhibitory syncope can cause sinus bradycardia.

2. Systemic diseases: influenza, typhoid fever, hypothyroidism, diphtheria recovery period, obstructive jaundice, increased intracranial pressure, certain infections such as leptospirosis, infectious mononucleosis, pituitary dysfunction, hyperkalemia, alkali poisoning, esophageal diverticulum, depression, can all cause sinus bradycardia.

3. Drug-related: Some drugs such as beta-blockers, reserpine, lidocaine, amiodarone, guanethidine, morphine, digitalis, quinidine, verapamil, neostigmine, anesthetics, etc. can cause sinus bradycardia.

4. Cardiovascular diseases: acute myocardial infarction, myocarditis, endocarditis, pericarditis invading the sinus node, chronic ischemic heart disease, sinus node inflammation, thrombosis, dilation, inflammation of the sinus node artery, certain cardiomyopathies such as amyloidosis, tetralogy of Fallot or after great vessel transposition surgery, microbial involvement of the heart, bleeding into the sinus node, familial sinus bradycardia, central nervous system diseases involving the inhibitory or accelerating centers of the heart, etc., can all lead to the occurrence of bradycardia.

Diagnosis is based on:

The electrocardiogram showed sinus P waves with a P wave rate less than 60 times per minute and a PR interval greater than 0.12 seconds.

1. For people who do not have heart discomfort, the pulse is between 50 and 60 beats per minute. This sinus bradycardia is mostly physiological, that is, it is a normal phenomenon. There is no need to worry about it affecting your health and no treatment is required.

2. For people who have heart discomfort, pay attention to counting the pulse rate when you are calm, and then count the pulse rate when you feel heart discomfort. If the pulse rate is lower than usual every time you feel uncomfortable, it means that your discomfort is caused by bradycardia and you need treatment. In severe cases, you need to install a pacemaker to speed up your heart rate. You can also check your 24-hour electrocardiogram to see what your heart rate is at its slowest. If the speed of your heartbeat has nothing to do with heart discomfort and your pulse is between 50 and 60 beats per minute, you do not need to treat your bradycardia, but you do need to do other tests to confirm whether you have heart disease.

Differential diagnosis:

1. Arrhythmia: It is a pathological phenomenon caused by abnormal heart beating due to heart disease. It mostly occurs in children, young people and the elderly, and is less common in middle-aged people. The mechanism of respiratory sinus arrhythmia is that during the breathing process, the tension of the vagus nerve and sympathetic nerve in the body changes, causing the automaticity of the sinoatrial node to change periodically and regularly. When you inhale, the sympathetic nerve tone increases and the heart rate increases. When you exhale, the vagus nerve tone increases and the heart rate slows down. The cycle of changes in heart rate is exactly equal to one breathing cycle, and the heart rhythm becomes regular when breathing stops.

2. Increased heart rate: People of different ages have different heart rates. The younger the age, the faster the heart rate. If the heart rate exceeds the normal range, it is called a fast heart rate. Parents generally know that a normal person's heart rate will increase after exercise or physical labor. The same is true for children, especially when they are frightened or crying.

3. Extreme heart rate: The rate of sinus node impulse formation in adults exceeds 100 beats per minute, which is called a fast heart rate, and the rate is usually between 101-160 beats per minute. When the heart rate starts and stops fast, the heart rate gradually increases and slows down.

4. Sinusoidal fetal heart rate: During fetal electronic monitoring, the fetal heart rate presents a sinusoidal fetal heart rate (Sinusoidal Fetal Heart Rate, SFHR). Diagnostic criteria for SFHR: (1) The baseline fetal heart rate is stable at 120-160 beats/min with regular fluctuations. (2) Amplitude 5~15 times/min. (3) Frequency 2~5 cycles/mino (4) Short-term variation is fixed or flat. (5) The sinusoidal wave oscillates above and below the baseline. (6) No normal fetal heart rate variability or response. (7) Lasts for more than 10 minutes.

Treatment and care

Patients with symptomatic bradycardia, especially those that affect their quality of life, or whose heart stops beating for more than 3 seconds, or who have transient blackouts or syncope, should receive active treatment.

In the event of an acute attack of bradycardia, in addition to treating the primary cause and stopping medications that can slow the heart rate, atropine or isoproterenol can be used to increase the heart rate. For those with a heart rate of 40 beats per minute or slower, drugs are not effective in raising the heart rate, especially in patients with recurrent syncope or presyncope, in whom a temporary pacemaker should be implanted.

After actively correcting the reversible primary cause and excluding the influence of drugs, if the patient's bradycardia symptoms cannot be reversed, a pacemaker needs to be implanted. A pacemaker is the size of a matchbox and weighs between 25 and 50 grams. The pulse generator is implanted under the skin in the upper chest, and the pacing wire is delivered to the heart through the veins. The pacemaker stimulates the heart with a certain form of artificial pulse current, causing the heart to contract effectively, thereby increasing the heart rate, relieving or eliminating the patient's symptoms and saving lives.