Q. Rhythm and conduction disturbances?
Alterations in cardiac rhythm occur frequently with exercise and are important in understanding a patients function and in providing predictive information as to mortality and morbidity. Arrhythmias during exertion result from symptomatically enhanced phase IV repolarization of ectopic foci, so that if the rate of the ectopic focus is faster than the normal pacer tissue in the sinus node, the focus assumes predominance and sets the rhythm. Alterations in the recovery time of cardiac tissues caused by ischaemia, and probably the battery effects associated with ischaemic tissue adjacent to normally perfused myocardium are important.