Noninvasive Hemodynamic Monitoring by Transthoracic Impedance Cardiography During Different Ventricular Activation Sequences in CRT Patients

Background: Echocardiography-based programming of conduction delays in cardiac resynchronisation therapy is complex and time-consuming. Impedance cardiography (ICG) may be an alternative method. However, it is unknown whether ICG is sensitive enough to detect haemodynamic changes due to different pacing-induced ventricular activation modes. The aim of this study was to determine the ability of ICG to measure haemodynamic changes during different ventricular pacing modes in patients with a cardiac resynchronisation therapy (CRT). Methods: 18 patients were evaluated. Stroke volume (SV), cardiac output (CO) and total peripheral resistance (TPR) were measured by means of ICG. Continuous blood pressure (cBP) was recorded with the vascular unloading technique. Haemodynamic measurements of 10-minute-sampling periods, taken in the supine position, were compared during biventricular (BIV), right (RV) and left ventricular (LV) pacing and intrinsic rhythm (IR). Results: One patient was excluded from the analysis (serious haemodynamic deterioration during IR). The age of the study population was 67 ± 10 years (94% male) with a LV ejection fraction of 26 ± 6%. The majority had left-bundle-branch block (82%). Compared to IR, BIV increased SV (58 ± 11 vs 67 ± 12 ml; p = 0.0007), CO (3.6 ± 0.7 vs 4.2 ± 0.8 l/min; p = 0.0007) and reduced TPR (1975 ± 410 vs 1694 ± 390 dyn*s/cm5). cBP remained unchanged during different ventricular pacing modes. Conclusion: ICG is able to detect intraindividual changes of haemodynamic parameters induced by different pacing modes. However, its sensitivity to detect haemodynamic changes through conduction delay variations, as performed for device optimisation, remains unclear.