Abnormal Rhythm

The abnormal rhythm of the heart means or indicates any variation from the typical sequence of electrical impulses generated in the heart. These variations may cause the electrical impulses too quickly, or too late or irregularly, leading to corresponding changes in the heartbeat rhythm, i.e., they occur either too fast or are delayed or erratic. These abnormal heart rates, also known as arrhythmia, can either be very brief or might last longer, and they can either be harmless or life-threatening. Problems related to the rate of the rhythm of heartbeat are generally categorised as arrhythmia. The abnormal changes in the heartbeat rhythm can hinder its function of pumping blood throughout the body. This will hinder the proper function of organs of the body, including the most vital organs like the brain, lungs, etc., and can also cause organ damage.

The Human Heart

The human heart is responsible for circulating blood throughout the entire human body. 

• It has two chambers on the upper side and two on the lower side called atria and ventricles, respectively. 
• The blood flows only in one direction when the heart contracts or beats, and the four valves inside the heart open and close to allow the blood to flow through the organ. 
• All four valves, namely the tricuspid valve, pulmonic, mitral, and aortic valve, consist of a set of flaps. 
• All the valves consist of three flaps except the mitral valve with two flaps. The pressure difference across the valves permits them to open and close, facilitating blood flow through the organ in one direction. 

The heart’s proper function depends on a sequence of highly organised contractions of the four chambers and the proper working of the valves, i.e., they must beat in an organised manner.

The Electrical System of the Heart

An electrical conduction system regulates the pumping action of the heart. It coordinates the contraction of the different chambers of the heart. 

In the right upper atrium, a small mass of specialised tissue called the Sinoatrial node or the Sinus node is responsible for generating a regular electrical impulse, 60 to 100 times in a minute under normal conditions. The electrical impulse stimulates the atria and activates them, and it triggers the contraction and pumping out of the blood of the heart’s ventricles. The contraction of the atria occurs for a short period, and they are stimulated first as compared to the two ventricles. The contraction of the ventricles represents heartbeats. As the SA node initiates the impulses for the heartbeat, it is also referred to as the ‘natural pacemaker of the heart.

From the Sinus node, the electrical impulse travels to the atrioventricular node or the AV node and then continue down to the ventricles via the bundle of His (His-Purkinje system), which divide into bundle branches, or the left and right pathways, to stimulate the left and the right ventricles. The contraction of the atria occurs prior to the contraction of the ventricles, and every contraction of the ventricle represents one heartbeat.             

In order to function correctly, this exact route is followed by the electrical impulse. The rhythm of the heartbeats depends on the transmission of this electrical impulse. The heart will beat or ‘pump’ regularly if the transmission of this electrical impulse is regular. The heart typically beats 60-100 times in a minute.

 Abnormal Rhythm

Any variation from the normal rhythm leads to abnormal heartbeats. Abnormal rhythm indicates any variation from the typical sequence of electrical impulses. Problems related to the rate of the rhythm of heartbeat are broadly categorised as arrhythmia. These variations may cause the electrical impulses too quickly, or too late or irregularly, leading to corresponding changes in the heartbeat rhythm, i.e., they occur either too fast or are delayed or erratic. These abnormal heart rates can either be harmless or life-threatening, and they can either be very brief or might last longer. Prolonged arrhythmias can be life-threatening and need to be treated accordingly. 

Tachycardia 

When the heartbeats occur faster than usual, i.e., more than 100 beats in a minute, the condition is called tachycardia. 

Types of tachycardia:

• Atrial or supraventricular tachycardia: 

In this condition, the heart’s upper chambers generate electrical impulses abnormally and interfere with the electrical impulses generated by the SA node (the heart’s pacemaker). This interference disrupts the complete filling of the heart’s chambers between contractions and affects blood flow to the body, leading to a faster heartbeat rate than average. People who smoke or drink alcohol or caffeinated substances heavily or are physically fatigued are usually affected by atrial or supraventricular tachycardia. 

• Sinus tachycardia:

The SA node generated the electrical impulses faster than usual in this condition. It does not generally affect the heart’s function. It is an average increase in the heartbeat rate and is usually caused due to anxiety, fright, severe emotional distress, or other conditions like anaemia, increased thyroid activity, etc.  

• Ventricular tachycardia: 

In this condition, the heart’s lower chambers generate electrical impulses abnormally and interfere with the electrical impulses generated by the SA node (the heart’s pacemaker). This can also disrupt the complete filling of the heart’s chambers between contractions and affect blood flow to the body, leading to a faster heartbeat rate than usual. Ventricular tachycardia is initiated at the heart’s lower chambers (the ventricles)  and can be harmless or life-threatening when other underlying heart conditions are present. 

Bradycardia

When the heartbeats occur slower than usual, i.e., less than 60 beats in a minute, the condition is called bradycardia. 

Problems related to the SA node, metabolic issues like hypothyroidism, other heart diseases, or medication-related to them are the primary causes of bradycardia. Issues related to the conduction pathways of the heart, which hinder the transport of electrical impulses from the atria to the ventricles, can also cause bradycardia. Occasional bradycardia is harmless; however, prolonged arrhythmia can be life-threatening. In such cases, a ‘pacemaker’ regulates the heart’s rhythm. 

Conclusion 

The abnormal rhythm of the heart means or indicates any variation from the typical sequence of electrical impulses generated in the heart, which causes the electrical impulses too quickly, or too late or in an irregular manner leading to corresponding changes in the heartbeat rhythm. This condition is broadly categorised as arrhythmia. The abnormal changes in the heartbeat rhythm can hinder its function of pumping blood throughout the body, thereby affecting the function of body organs.