Figure 4 - uploaded by Cecilia Linde
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Concept of measuring the estimated pulmonary artery diastolic (ePAD) pressure using the maximum first derivative of the RV pressure curve (+dp/dt).
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Optimization of pacing parameters such as AV delay is important in heart failure (HF) patients treated with cardiac resynchronization therapy (CRT). We hypothesized, that an implantable hemodynamic monitor (IHM) might be helpful in identifying the optimal AV-delay. 10 patients with HF, successfully treated by CRT were also implanted with an IHM tha...
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... system that continuously recorded and stored real-time pressure waveforms, device marker channel and Chronicle lead unipolar EGM. The pressure sensor inserted into the right ventricle continuously measures absolute cavity pressures. To correct for changes in atmospheric pressure, an external pressure reference is used to correct for barometric alterations in pressures and to allow a reliable measurement of absolute cardiac pressures. The resulting data contains a variety of pressure waveform characteristics that were validated in previous studies(6). The concept to measure the estimated pulmonary artery diastolic (ePAD) pressure has been evaluated and found to be a good estimate for left ventricular filling, Figure 4. The ePAD is measured as the pressure at time of pulmonary valve opening defined by maximum positive dp/dt of the RV pressure curve. For the individual patient a low left ventricular filling was considered to be a hemodynamically optimized condition for a heart failure patient. For statistical test, SPSS 12.0 for Windows, SPSS Inc. was used. The non-parametric Mann-Whitney U test was applied to compare differences within the groups and a p- level of 0.05 was considered statistically significant. Dual device implant was well tolerated by the patients and no adverse events occurred during acute AV optimization procedures. One patient was excluded due to development of chronic atrial fibrillation and could thus not complete the AV optimization procedure, since no AV delays can be assigned in patients with AF due to irregular, unsynchronized and chaotic electrical activation of the atrial chambers. Using the IHM, a U-shaped curve was obtained, indicating an optimal AV delay slightly longer (+20 ms) as compared with echo (-0.7± 1.4 mm Hg, p<0.01). Shortening the AV interval resulted in increased ePAD (+2.3 ± 2.3 mmHg, p<0.001). The relatively low ePAD at +60 ms may be associated with fusion beats at longer AV-delays. These observations were consistent in the repeated tests. In this study the IHM was used to assess the hemodynamic response to different AV delays during resting condition. During these acute tests significant changes of RV hemodynamics were observed resulting from different AV intervals programmed to CRT devices. Using RV pressures for device optimization, the optimal AV delay identified by the IHM was similar to standard echo optimization according to the Ritter method, which is also demonstrated by the U-shaped ePAD curves compared to echo optimized AV delay. The analysis of right ventricular hemodynamics suggest to avoid short AV delays in clinical practice and to perhaps chose slightly longer AV delays than those suggested by echo methods. The IHM, therefore can be considered to be a helpful tool for the identification of the optimal AV-delay in HF patients treated with CRT. However, further studies need to be performed to confirm this. Furthermore, the Chronicle device allows monitoring RV pressures continuously and therefore has the potential to measure hemodynamic alterations that reflect daily living conditions like exercise or different body positions. Automated closed-loop procedures would allow repeated device optimizations based on the hemodynamic status of the individual patient. In the future, a hemodynamic sensor may be incorporated in CRT devices for long-term recording of filling pressures and to allow for hemodynamic device optimization during daily activities of living. This work was supported in part by grants from the 1) Swedish Heart and Lung foundation, Stockholm, Sweden and 2) Medtronic Bakken Research Center B.V., Maastricht, ...
Citations
... These devices culminated in the development of the Chronicle R IHM (IHM-2; Model 9520) (Figure 2A). The IHM-1 and IHM-2 devices have demonstrated significant changes in RV pressures associated with changes in diuretic therapy (Braunschweig et al., 2002), β-adrenergic receptor blockers (Ishikawa et al., 2009), biventricular pacing (Bruns et al., 2005), and inhaled therapies for pulmonary hypertension patients (Fruhwald et al., 2003;Karamanoglu et al., 2007). ...
Heart failure (HF) is a costly, challenging and highly prevalent medical condition. Hospitalization for acute decompensation is associated with high morbidity and mortality. Despite application of evidence-based medical therapies and technologies, HF remains a formidable challenge for virtually all healthcare systems. Repeat hospitalizations for acute decompensated HF (ADHF) can have major financial impact on institutions and resources. Early and accurate identification of impending ADHF is of paramount importance yet there is limited high quality evidence or infrastructure to guide management in the outpatient setting. Historically, ADHF was identified by physical exam findings or invasive hemodynamic monitoring during a hospital admission; however, advances in medical microelectronics and the advent of device-based diagnostics have enabled long-term ambulatory monitoring of HF patients in the outpatient setting. These monitors have evolved from piggybacking on cardiac implantable electrophysiologic devices to standalone implantable hemodynamic monitors that transduce left atrial or pulmonary artery pressures as surrogate measures of left ventricular filling pressure. As technology evolves, devices will likely continue to miniaturize while their capabilities grow. An important, persistent challenge that remains is developing systems to translate the large volumes of real-time data, particularly data trends, into actionable information that leads to appropriate, safe and timely interventions without overwhelming outpatient cardiology and general medical practices. Future directions for implantable hemodynamic monitors beyond their utility in heart failure may include management of other major chronic diseases such as pulmonary hypertension, end stage renal disease and portal hypertension.
The efficacy of cardiac resynchronization therapy (CRT) through biventricular pacing (BVP) has been demonstrated by numerous studies in patients suffering from congestive heart failure. In order to achieve a guideline for optimal treatment with BVP devices, an automated non-invasive strategy based on an electrophysiological computer model of the heart is presented. The presented research investigates an off-line optimization algorithm based on different electrode positioning and timing delays.
