In the absence of autocapture, it could be necessary to program a 5 V output or to reportage for lead repositioning. The chronic threshold curve showed a high voltage pattern in four patients. One diabetic patient showed an intermittent HVP during a period of hyperglycemia that end in a precoma state which required emergency treatment. HVP disappeared after control of the abnormal metabolic state. The main cause for HVP is pseudofusion beats, which are very frequent in a population such as ours with atrial fibrillation.
Most fusion beats show good sensing of evoked response.
A pseudofusion beat appears secondary to late or non detection of spontaneous R waves appearing just at the end of the escape interval. It was our hypothesis that, by increasing the level of sensitivity of the pacemaker to the R wave, the incidence of pseudofusion beats will decrease, as was demonstrated with the control of HVP by this reprogramming option. Initially this was because of the low capacity of batteries. Thereafter it was because of the high level of consumption of special functions and the need to decrease the size of batteries to have smaller pacemakers for children and very thin patients and to leave more space for sophisticated circuits with high ROM and RAM capabilities. After termination of a pacing stimulus, a decay voltage of opposite polarity exists between cathode and anode.