Impedance measurements for pacing treatment in syncopic patients

Intracardiac electrical impedance was proposed as a method of assessing of signal for pacing control since 20 years. In cardiac pacing applications of impedance method one or more intracardiac pacing leads and active pacemaker housing are used as poles for measurement procedure. The stroke volume (SV) signal can be calculated from impedance signal by specialized algorithm in typical pacing system. Our previous study has showed that in group of 42 syncopic patients developing of vasodepresive reaction the SV drop was observed significantly before blood pressure (BP) drop. We have found that the SV drop is excellent indicator of early phase of syncope. In order to confirm that impedance cardiography and Penaz plethysmographic methods for assessment of SV provide the same results additional study were performed. The group of 6 patients were enrolled in the study group. All patients underwent standard passive head up tilt test (HUT). The standard HUT with 20 min. of elevation (60%) was followed by nitroglycerine (NTG) administration of 300 mg of NTG for patients with negative (no syncope) passive result. Impedance cardiography and Penaz plethysmography were carried out parallely during whole study. The statistical ANOVA analysis of the obtained data showed no significant differences of the results obtained in two applied methods. Study has showed that SV calculated from impedance signal should be taken under consideration for early syncope detection.