Sinus Arrhythmia                                                                                  

The commonest arrhythmias is sinus arrhythmia. It is a normal physiological response to the phases of respiration. During inspiration the venous return is increased as the negative intrathoracic pressure "sucks" the blood into the heart. It takes longer to eject this additional volume from the heart and hence the heart rate slows. In expiration the converse is true and the rate increases.

In children the rate may vary widely with the phase of respiration - it is usually much more marked than in adults. It can be distinguished by the cyclical nature of the changes, the presence of a p wave prior to each qrs complex and the constant nature of the pqrs pattern. It is of no clinical consequence.

This page was last edited 14/2/2004