Brief Answer: due to fever, electrolyte or metabolic changes Detailed Answer: Hi, thanks for using healthcare magic In the normal heart beat, a 'signal' is sent from a specific point of the heart called the sinus atrial node (it is called the heart's pacemaker). This signal then travels along a specific pathways (called bundle branches) which then cause the left and right side of heart to contract- the heart beat. The heart then goes back to its resting state (how it is when not contracting). Abnormal heart rhythms can occur as a result of: (1)problems at the sinus atrial node (2)another part of the heart sending off the signal instead of or in addition to the sinus atrial (3)blockage along the normal heart pathways that normally carry the signal (4)abnormal structure of the heart such as enlargement of some aspect (5)problems at the resting state stage When a person is sick abnormal heart rhythms may occur for different reasons such as: (1)fever- this affects the sinus atrial node causing it to send out signals faster , increasing heart rate (2)metabolic and electrolyte abnormalities (abnormal levels of calcium, sodium, potassium) can occur due to altered appetite, fluid loss (from fever, vomiting, diarrhoea, decreased intake). These abnormalities would affect the 'signal' at different points- at the sinus atrial node , affect the progress of the conduction or movement of the signal through the heart SUMMARY This means that the changes that occur during illness cause abnormalities in how the signal in the heart is able to move through the heart. I hope this helps, feel free to ask any other questions

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