Sympathetic influences exert the opposite effect. In this regard, automaticity is an important property of the cardiac cells that is normally observed in the sinus node, the specialized fibres of the His-Purkinje system, and in some specialized atrial fibres. Bradyarrhythmias result from abnormalities either of impulse formation, that is, automaticity or of conduction. In cardiac surgery, due to the fact that the patient would be brought in a cardiac standstill and other pharmacologic agents would be used to facilitate this would lead to low cardiac output and hence bradyarrhythmias. (Debrunner, M., Naegeli, B., Genoni, M., Turina, M., and Bertel, O., 2004, p 16).
The sinus node is normally the dominant cardiac pacemaker because of its intrinsic discharge rate that is highest of all potential cardiac pacemakers. Its responsiveness to alterations in the autonomic nervous system tone is responsible for a rapid heart rate, and the reverse in slowing (Reade, M.C., 2007, p 367). ...
Whatever may be the reason, the manifestations happen due to abrupt, prolonged sinus pauses caused by failure of sinus impulse formation or block of conduction of sinus impulse to the surrounding atrial tissues (Bethea, B.T. et al., 2005, p 106). In some patients, sinus node dysfunction is accompanied by abnormalities in AV conduction, and thus aside from having absence of atrial activity, the lower pacemakers fail to emerge during sinus pauses (Daoud, E.G., Snow, R., Hummel, J.D., Kalbfleisch, S.J., Weiss, R., and Augostini, R., 2003, p. 129). External energy sources can be used to stimulate the heart when disorders in impulse formation and/or transmission lead to symptomatic bradyarrhythmias. Pacer stimuli can be applied to the atria and/or ventricles (Overbay, D. and Criddle, L., 2004, p. 26).
Temporary pacing is usually instituted to provide pacemaker support when a bradycardia is precipitated by what is presumed to be a transient event, such as, induced cardiac standstill during an open heart surgery, induced cardioplegia in bypass surgeries, ischemia, or drug toxicity (Roschkov, S. and Jensen, L., 2004, p. 33). Temporary pacing is usually achieved by insertion of an electrode catheter with the catheter positioned in the right ventricular apex and attached to an external generator. This generator will assist the heart to generate a pacing impulse on the face of reduced excitability. Excitatory impulses generated by the temporary pacing apparatus would generate depolarization potential to cause cardiac contraction. Epicardial wires allow temporary pacing after cardiac surgery (Puskas, J.D., Sharoni, E., Williams, W.H., Petersen, R., Duke, P., and Guyton, R.A., 2003, pp. E-103). Pacing is