What is Sinus Rhythm?

Sinus rhythm is the rhythm of the heart determined by the sinus node. Electrical pulses are generated in sinus node and travel through the heart muscles and cause them to contract and beat. The sinus node is also called a natural pacemaker of the heart.

Sinus rhythm is different from heart rate.

Heart rate is a term that denotes the number of times the heart beats in a minute. A resting heart rate is 60-100 beats per minute and it is considered normal.⁽¹⁾ Depending on the demands on the heart, its rate can be either faster or slower than the normal rate.

Sinus rhythm is the pattern of the heartbeat. It is the rate at which the electrical pulses are sent from the sinus node. These pulses if sent at a normal rate are referred to as sinus rhythm.

Sinus rhythm and heart rate are linked in a way. The electrical pulses originated from the sinus node, which is the sinus rhythm. These pulses may cause the heart muscle to contract, which is called the heart rate.

A rhythm of a normal heart is known as a normal sinus rhythm. It originates from the sinus node and is transmitted through the heart muscle. Although, in adults, a normal sinus rhythm usually accompanies a heart rate of 60-100 beats per minute, a slower and faster heart rhythm can also be considered normal.

Sinus tachycardia occurs when there is rapid electrical pulses from the sinus node which in turn increases the heart rate to more than 100 beats per minute. It can occur due to hyperthyroidism, congenital heart conditions, hypoglycemia, severe bleeding, pulmonary embolism, anemia, dehydration and heart damage due to heart disease.

Sinus tachycardia is normal in certain conditions such as:

• While exercising
• Fever
• Stress and anxiety
• Having stimulants such as caffeine, nicotine or recreational drugs
• Having certain medications
• Having sinus tachycardia at rest may indicate a serious health complication.

Sinus bradycardia happens when the sinus node sends slower pulses, which leads to a slower heart rate. It causes a heart rate of 60 beats per minute or lower. It occurs due to sleep apnea, myocarditis, pericarditis, hypothyroidism, rheumatic fever and congenital heart conditions.

A heart rate of 60 beats per minute can be normal in a few people such as young adults and athletes. It also happens when a person is in deep sleep or taking certain medication. But in many people, it may indicate that the heart is not distributing oxygenated blood to the body.

An abnormal heart rate or rhythm is known as arrhythmia. It leads to sinus tachycardia and sinus bradycardia.

Sinus tachycardia can increase the risk of heart failure, stroke, and sudden cardiac arrest. The symptoms of sinus tachycardia include:

• Heart palpitations
• Fatigue
• Fainting
• Chest pain
• Lightheadedness
• Shortness of breath
• Dizziness

Sinus bradycardia may lead to confusion, disorientation, worsening of heart failure, loss of consciousness, and sudden cardiac arrest. The symptoms of sinus bradycardia include:

• Lightheadedness
• Fainting
• Shortness of breath
• Difficulty in exercising
• Feeling fatigues and weak
• Dizziness

Sick sinus syndrome is used for conditions that may point towards a problem in the sinus node. Along with sinus arrhythmia, other types of sick sinus syndrome include:

• Sinus Arrest: A condition in which the sinus node stops transmitting electrical pulses.
• Sinoatrial Block: In this, the electrical pulses move very slowly through the sinus node and may lead to a slower than normal heart rate.
• Bradycardia-Tachycardia (tachy-brady) Syndrome: The heart beats alternately from fast and slow rhythms.

Sinus rhythm is the pace of the heart set by the sinus node, which is a natural pacemaker of the body. A normal sinus rhythm keeps the heart rate within the normal range.