Cardiac resynchronization therapy (CRT) is an established therapy for heart failure patients and improves symptoms, quality of life in patients with sinus rhythm, reduced left ventricular ejection fraction (LVEF) lower or equal thirty five percent, left bundle branch block and QRS duration more than one hundred fifty millisecond [1, 2]. Since approximately sixty percent of heart failure patients have a normal QRS duration they do not benefit or respond to the CRT. Cardiac contractility modulation (CCM) releases nonexcitatoy impulses during the absolute refractory period in order to enhance the strength of the left ventricular contraction and improve exercise tolerance and quality of life . The aim of the investigation was to evaluate differences in cardiac index between optimized and nonoptimized CRT and CCM to reference values with impedance cardiography, a noninvasive method. Cardiac index (CI) contains a relation of cardiac output (CO) and body surface area (BSA) from patients.
Cardiac index measurements of 36 patients with 10 CRT, 10 CCM and 16 reference patients (mean age 49.36±24.43 years, 6 females, 30 males) were mounted by noninvasive impedance cardiography and compared with an optimized and not optimized atrio- and interventricular delay.
Cardiac index consists of body surface area and cardiac output. The body surface area is calculated from the patient’s height, weight and gender. Cardiac output is made up of stroke volume multiplied by heart rate.
Stroke volume in turn was measured with left ventricular ejection time (LVET) multiplied by the amplitude of the systolic wave in the ICG, divided by the base impedance (Z0), overall the thorax and a part of the volume of the thorax which is electrically participated (VEPT).
Patient data and values were mounted by Cardio Vascular Lab 2.5 software and CardioScreen 1000 hardware (Medis Medizinische Messtechnik GmbH, Ilmenau, Germany)
Statistical analysis was performed by Origin®9.1 software (OriginLab Corperation, Northampton, MA, USA).
3.1 Cardiac index comparison with CCM- and CRT-device before and after optimizing atrio- and interventricular delay
This investigation includes 36 patients (mean age 49.36±24.43 years, 6 females, 30 males) with 10 clinical measurements of CRT and CCM patients respectively and 16 reference values as measured by students. CRT patients (mean age 62.70±0.99 years, 10 males) improved cardiac index from 2.34±0.67 l/min/m2 up to 3.27±0.99 l/min/m2 with an increase of 39.74%. The cardiac index improvement of CCM Patients (mean age 75.60±0.51 years, 3 females, 7 males) is 21.89% from 2.33±0.65 l/min/m2 to 2.84±0.51 l/min/m2. Reference values from students (mean age 24.63±1.67 years, 3 females, 13 males) serve as standard values.
Noninvasive impedance cardiography can be utilized to evaluate the improvement and increase of cardiac index in atrio- and interventricular delay optimized cardiac resynchronization therapy and cardiac contractility modulation.
Heinke M., Surber R., Kühnert H., Dannberg G., Prochnau D., Figulla H.R.: Transesophageal left ventricular posterior wall potential in heart failure patients with biventricular pacing. Biomed. Techn. 52, (2007), 173-179. Google Scholar
Heinke M., Ismer B., Kühnert H., Figulla H.R.: Transesophageal left ventricular electrogram-recording and temporary pacing to improve patient selection for cardic resynchronization. Med Biol Eng Comput (2011) 49: 851-858 Google Scholar
Kuschyk J., Roeger S., Schneider R., Streitner F., Stach K., Rudic B., Weiß C., Schimpf R., Papavasilliu T., Rousso B., Burkhoff D., Borggrefe M.: Efficacy and survival in patients with cardiac contractility modulation: Long-term single center experience in 81 patients. Int J Cardiol. (2015) 183C:76-81 Google Scholar
About the article
Published Online: 2015-09-12
Published in Print: 2015-09-01
Conflict of interest: Authors state no conflict of interest. Material and Methods: Informed consent: Informed consent is not applicable. Ethical approval: The research related to human use has been complied with all the relevant national regulations, institutional policies and in accordance the tenets of the Helsinki Declaration, and has been approved by the authors’ institutional review board or equivalent committee.