What is sinus rhythm?
Sinus rhythm relates to the rhythm of the heart beat, and is determined by the sinus node .
The sinus node is the heart’s natural pacemaker that creates an electrical pulse which travels through the heart muscle.
Imagine an electrical shock that is sufficient to causes the heart to contract, or beat.
The sinus rhythm is in fact different from heart rate because the heart rate refers to the number of times the heart beats in a minute, whereas the sinus rhythm, refers to the pattern of the heartbeat.
Normal sinus rhythm
Normal sinus rhythm is deemed as a healthy heart rhythm.
The electrical impulse from the sinus node is being transmitted properly.
Normal sinus rhythm in adults generally has a heart rate of 60 to 100 beats per minute. But in reality the normal heart rates varies from individual to individual.
The target heart rate zones shown below are based on what is equal to 50 to 85 percent of the average maximum heart rate for each stated age.
The average maximum heart rate is based on the calculation of 220 minus years of age.
Please be aware that these figures are averages and should be used only as a general guide.
| Age | Target heart rate zone | Average maximum heart rate |
| 25 years | 100 to 170 beats per minute | 220 beats per minute |
| 30 years | 95 to 162 beats per minute | 190 beats per minute |
| 35 years | 93 to 157 beats per minute | 185 beats per minute |
| 40 years | 90 to 153 beats per minute | 180 beats per minute |
| 45 years | 88 to 149 beats per minute | 175 beats per minute |
| 50 years | 85 to 145 beats per minute | 170 beats per minute |
| 55 years | 83 to 140 beats per minute | 165 beats per minute |
| 60 years | 80 to 136 beats per minute | 160 beats per minute |
| 65 years | 78 to 132 beats per minute | 155 beats per minute |
| 70 years and up | 75 to 128 beats per minute | 150 beats per minute |
Sinus rhythm arrhythmia
An arrhythmia is when the heart beats too many or too few times in a minute.
Sinus tachycardia
Sinus tachycardia happens when the sinus node sends too many electrical impulses in a certain amount of time. This leads to a faster heart rate.
Whilst the electric pulse causing the heart to beat may be quite normal, the actual pace of these beats is faster than it should be.
An idividual with a heart rate exceeding 100 beats per minute is considered to have tachycardia and can be referred to as being ‘tacky’.
A patient may have tachycardia and not know it, because it doesn’t always cause symptoms.
Sinus tachycardia can increase the risk of serious complications, including heart failure, stroke, or sudden cardiac arrest in some cases.
Possible causes of sinus tachycardia, could include:
- fever
- anxiety, fear, or emotional distress
- exercise
- damage to your heart due to heart disease
- anemia
- hyperthyroidism
- severe bleeding
Sinus bradycardia
The opposite to sinus tachycardia is sinus bradycardia and occurs when your sinus node fails to send sufficient electrical impulses, resulting in a heart rate of fewer than 60 beats per minute.
Be mindful that a heart rate below 60 beats per minute could be quite be normal for some individuals, such as younger adults and athletes. However, for others, this can be a sign that the heart is not distributing sufficient oxygenated blood through the body.
Like sinus tachycardia, sinus bradycardia can be caused by a number of things, including:
- damage to your heart due to heart disease
- issues with your sinus node
- electric conduction issues in your heart
- damage to your heart related to aging
- hypothyroidism
Sick sinus syndrome
Sick sinus syndrome is an overall term for a group of symptoms that indicate an issue or potential problem in connection with the sinus node.
In addition to sinus node arrhythmias, there are other forms of sick sinus syndrome, these include:
- Sinus arrest. It causes the sinus node to stop transmitting electric impulses for a brief moment.
- Sinoatrial block. When electrical impulses travel too slowly through the sinus node, it leada to a slower-than-normal heart rate.
- Bradycardia-tachycardia (tachy-brady) syndrome. The heart beat fluctuates between fast and slow rhythms.