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Relationship between intracardiac impedance and left ventricular contractility in patients undergoing cardiac resynchronization therapy
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Sciences.
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2011 (English)In: Europace, ISSN 1099-5129, E-ISSN 1532-2092, Vol. 13, no 7, 984-991 p.Article in journal (Refereed) Published
Abstract [en]

Aims Cardiac resynchronization therapy (CRT) has dramatically improved the symptoms and prognosis of patients with heart failure in large randomized clinical trials. Optimization of device settings may maximize benefit on an individual basis, although the best method for this is not yet established. We evaluated the use of cardiogenic impedance measurements (derived from intracardiac impedance signals) in CRT device optimization, using invasive left ventricular (LV) dP/dt(max) as the reference. Methods and results Seventeen patients underwent invasive haemodynamic assessment using a pressure wire placed in the LV cavity at the time of CRT device implantation. Intracardiac impedance measurements were made at different atrioventricular (AV) and interventricular (VV) delays and compared with LV dP/dt(max). We assessed the performance of patient-specific and generic impedance-based models in predicting acute haemodynamic response to CRT. In two patients, LV catheterization with the pressure wire was unsuccessful and in two patients LV lead delivery was unsuccessful; therefore, data were acquired for 13 out of 17 patients. Left ventricular dP/dt(max) was 919 +/- 182 mmHg/s at baseline and this increased acutely (by 24%) to 1121 +/- 226 mmHg/s as a result of CRT. The patient-specific impedance-based model correctly predicted the optimal haemodynamic response (to within 5% points) for AV and VV delays in 90 and 92% of patients, respectively. Conclusion Cardiogenic impedance measurements are capable of correctly identifying the maximum achievable LV dP/dt(max) as measured by invasive haemodynamic assessment. This study suggests that cardiogenic impedance can potentially be used for CRT optimization and may have a role in ambulatory assessment of haemodynamics.

Place, publisher, year, edition, pages
2011. Vol. 13, no 7, 984-991 p.
Keyword [en]
Cardiac resynchronization therapy, Cardiogenic impedance, Device optimization, Haemodynamics
National Category
Medical and Health Sciences
URN: urn:nbn:se:uu:diva-156251DOI: 10.1093/europace/eur055ISI: 000292317900015OAI: oai:DiVA.org:uu-156251DiVA: diva2:431335
Available from: 2011-07-19 Created: 2011-07-18 Last updated: 2013-01-22Bibliographically approved
In thesis
1. Cardiac Resynchronization Therapy Optimization: Comparison and Evaluation of Non-invasive Methods
Open this publication in new window or tab >>Cardiac Resynchronization Therapy Optimization: Comparison and Evaluation of Non-invasive Methods
2012 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The general purpose of this thesis was to investigate new cardiac resynchronization therapy (CRT) optimization techniques and to assess their reliability when compared to invasive measurements of left ventricular contractility (LV dP/dtmax).We first assessed whether cardiac output (CO) measured by trans-thoracic impedance cardiography could correctly identify the optimal interventricular (VV) pacing interval while using invasive measurements of LV dP/dtmax as reference. We did not find any significant statistical correlation between the two optimizing methods when their corresponding optimal VV intervals were compared.

We also tested the hypothesis that measurements of right ventricular contractility (RV dP/dtmax) could be used to guide VV delay optimization in CRT. The comparison of optimal VV intervals obtained from the left and right ventricular dP/dtmax did not show a statistically significant correlation; however, a positive correlation was found when broader VV intervals were evaluated and we concluded that this finding deserves further investigation.

An interesting alternative for CRT optimization is the use of device integrated algorithms or sensors capable to adapt the CRT settings to the current needs of the individual patient. In this respect we investigated the use of cardiogenic impedance (CI) measurements obtained through the CRT-D device as a method for CRT optimization with invasive measurements of LV dP/dtmax as a reference. Our results showed that CI could be measured through the device after implantation and that a patient-specific impedance-based prediction model was capable to accurately predict the optimal AV and VV delays. To follow up on these positive results we re-evaluated the patient-specific impedance-based prediction models 24 hours post implantation and investigated the possibility of calibrating them using parameters derived from non-invasive measurements of arterial pressure obtained by finger pelthysmography at implantation.The results showed that the patient-specific impedance-based prediction models did not perform as well on the follow-up data as they did on the data from implantation day and that they correlated poorly with plethysmographic parameters.

Our studies suggest that novel methods for CRT optimization should be thoroughly evaluated and compared to established measures of left ventricular function prior to introduction into clinical practice.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2012. 52 p.
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Medicine, ISSN 1651-6206 ; 802
cardiac resynchronization therapy, device optimization, left ventricular contractility
National Category
Cardiac and Cardiovascular Systems
Research subject
urn:nbn:se:uu:diva-179785 (URN)978-91-554-8450-7 (ISBN)
Public defence
2012-10-05, Robergsalen, Akademiska Sjukhuset, Ing. 40, Uppsala, 13:00 (English)
Available from: 2012-09-14 Created: 2012-08-22 Last updated: 2013-01-22Bibliographically approved

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