Introduction Patients with activation induced heart failure may benefit from cardiac resynchronization therapy (CRT). For this treatment a biventricular pacemaker is used to stimulate the myocardium. We evaluated the changes of three seismocardiographic timing intervals from patients with CRT, when the pacemaker was turned off and on. Seismocardiography (SCG) could provide a new simple technique for pacemaker optimization compared to traditional echocardiography.
Method We recruited 10 patients (40 % females, mean age 59.6 ± 13.4 years) with biventricular pacemaker. The study was approved by the local ethical committee (N-20120068) and all patients signed written inform consent. Subjects were supine in rest while ECG and SCG were recorded simultaneously at 5000 Hz. The accelerometer for the SCG recording was placed on the xiphoid process. Recordings were performed with the pacemaker turned on and off. Based on the ECG R-peak, individual beats were extracted and a mean SCG beat was calculated for each patient. Fiducial points in the SCG correlating with valve events were annotated manually according to previous work. Based on these points isovolumetric contraction time (IVCT), left ventricular ejection time (LVET) and isovolumetric relaxation time (IVRT) were computed for both settings of the pacemaker. The t-test was used to test for significant differences in timing between the pacemaker settings.
Results IVCT was significantly shorter with the pacemaker turned on (44.1 ± 6 ms) compared to off (53.1 ± 13 ms, p < 0.01). LVET and IVRT were not changed statistically significant (p = 0.1 and p = 0.9 respectively).
Discussion The results of this study illustrate some of the effects that CRT has on patients with activation induced heart failure. The shortening of IVCT indicates an improved cardiac contraction. SCG could potentially be used in a clinical setting for pacemaker optimization as an easy-to-use and affordable alternative to echocardiography.