Noninvasive Monitoring of Stroke Volume With Resynchronization Devices in Patients With Ischemic Cardiomyopathy

BackgroundA novel method to estimate cardiac volumes based on impedance measurements using the leads of a resynchronization device has been developed. This study investigated the method in patients with ischemic cardiomyopathy and documented wall motion abnormalities.Method and ResultsFifteen postinfarction patients (age 68 ± 8 years, ejection fraction 27 ± 5%) with symptomatic heart failure and ≥1 akinetic or dyskinetic segment were included. During the implantation of a cardiac resynchronization therapy (CRT) device, acute impedance curves were recorded along with stroke volume determined by the arterial pulse contour method. In an overdrive protocol, the impedance parameter “stroke impedance” decreased in significant correlation with stroke volume in all patients. The median correlation coefficient between stroke volume and stroke impedance was 0.83 (interquartile range 0.70–0.89). Furthermore, the atrioventricular delay was optimized based on impedance and reference stroke volume. After optimization by the impedance method, it differed by 18 ± 15 ms from the figure after optimization by the invasive reference. Compared with a standard atrioventricular delay of 120 ms, stroke volume was improved by 8.6 ± 9.8% with the use of invasive optimization and by 6.4 ± 10.8% with the use of impedance-based optimization.ConclusionsIn CRT patients with chronic infarction and wall motion abnormalities, impedance is a valid parameter to estimate stroke volume and to guide optimization of CRT timing.