Noninvasive detection of insulation break

The electric current leak through an unsealed connector or insulation break can be a source of problems in cardiac pacing. This study describes a method of leak detection. The underdrive inhibition test--chest wall stimulation with external stimulator (ES)--was used for this purpose. Three cutaneous electrodes (CE) were applied: the first one above the indifferent electrode, the second one above the suspected leak location, and the third one above the active electrode. Two inhibition thresholds (IT) were measured: the first one connecting ES on first CE and second CE, and the second one connecting ES on first CE and third CE. The inhibition threshold is the value of ES output charge at which the inhibition of implanted pacemaker occurs. The relation between two ITs, not the absolute value, is significant for leak estimation. The former should be at least five times higher than the latter, if there is no current leak. During the two years of follow-up of 541 patients, 272 measurements were performed. In 52 cases the connector leak was found-both ITs were approximately equal. Twenty-seven cases were confirmed by surgery for EOL pacemaker replacement; the intrusion of body fluid was evident. Five operations were indicated because of the leak problem: two--muscle twitching, one--loss of capture, one-undersensing, and one--insulation break with lead fracture. The method, although approximate, is a reliable qualitative estimation of leak.