Ex vivo Validation of Noninvasive Epicardial and Endocardial Repolarization Mapping

Background: The detection and localization of electrophysiological substrates currently involve invasive cardiac mapping. Electrocardiographic imaging (ECGI) using the equivalent dipole layer (EDL) method allows the noninvasive estimation of endocardial and epicardial activation and repolarization times (AT and RT), but the RT validation is limited to in silico studies. We aimed to assess the temporal and spatial accuracy of the EDL method in reconstructing the RTs from the surface ECG under physiological circumstances and situations with artificially induced increased repolarization heterogeneity.Methods: In four Langendorff-perfused pig hearts, we simultaneously recorded unipolar electrograms from plunge needles and pseudo-ECGs from a volume-conducting container equipped with 61 electrodes. The RTs were computed from the ECGs during atrial and ventricular pacing and compared with those measured from the local unipolar electrograms. Regional RT prolongation (cooling) or shortening (pinacidil) was achieved by selective perfusion of the left anterior descending artery (LAD) region.Results: The differences between the computed and measured RTs were 19.0 ± 17.8 and 18.6 ± 13.7 ms for atrial and ventricular paced beats, respectively. The region of artificially delayed or shortened repolarization was correctly identified, with minimum/maximum RT roughly in the center of the region in three hearts. In one heart, the reconstructed region was shifted by ~2.5 cm. The total absolute difference between the measured and calculated RTs for all analyzed patterns in selectively perfused hearts (n = 5) was 39.6 ± 27.1 ms.Conclusion: The noninvasive ECG repolarization imaging using the EDL method of atrial and ventricular paced beats allows adequate quantitative reconstruction of regions of altered repolarization.

Comparative evaluation of visceral and renal protection methods during thoracoabdominal aortic repair (Experience of Russian Surgery Research Center named after B.V. Petrovsky)

The objective: to compare the effectiveness of visceral and renal protection methods during thoracoabdominal aortic (TAA) repair: left atrial-femoral bypass (LAFB) and cardiopulmonary bypass (CPB) in conjunction with selective perfusion (SP) of these organs.Subjects: 81 patients who underwent TAA repair were enrolled in retrospective analysis: LAFB was used in 29 patients (Group 1), CPB and SP ‒ in 52 patients (Group 2).Results. In Group 2, there were lower intraoperative blood loss volume (1,500 ml vs 4,200 ml, p < 0.001), significantly lower levels of direct bilirubin, blood creatinine, blood alpha-amylase in postoperative period, significantly shorter duration of hospital stay, ICU stay and duration of mechanical ventilation. Also in this group, there were lower incidence of multiple organ dysfunction (11.5% vs 37.9%, p = 0.005), stroke (0 vs 10.3%, p = 0.043), lower need for requirement (3.8% vs 20.7%, p = 0.022) and mortality (3.8% vs 27.6%, p = 0.003).Conclusion: During TAA repair, CPB in conjunction with selective visceral and renal perfusion is more beneficial for organ protection as compared with LAFB.

Noninvasive unipolar electrogram T-wave upslope is an accurate marker of local refractoriness in explanted hearts with drug-induced repolarization dispersion

Funding Acknowledgements Type of funding sources: Public grant(s) – National budget only. Main funding source(s): French National Research Agency Matthijs Cluitmans is supported by a Veni grant from the Netherlands Organization for Scientific Research Background The relationship between T-wave morphology in local unipolar electrograms (UEGs) as mapped with noninvasive electrocardiographic imaging (ECGI) and local repolarization time (RT) has not been validated in pronounced RT dispersion. Purpose To study the time of upslope of the T-wave (Tup) in epicardial UEGs mapped with ECGI as a marker of time of local refractoriness (trefr, a surrogate for RT) in intact hearts with RT dispersion. Methods Six pig hearts were Langendorff-perfused with selective perfusion of the LAD artery and submersed in a torso-shaped tank containing 256 electrodes on the torso surface (panel A). RT was prolonged in the non-LAD regions by infusing dofetilide (‘Dof’) and shortened in the LAD region using pinacidil (‘Pin’). Tup was determined in both invasive UEGs (recorded with epicardial electrodes) and in noninvasive UEGs (reconstructed with ECGI). Programmed stimulation was used to determine trefr, defined as the shortest coupling interval with capture. Both metrics were determined relative to the common pacing spike. Results In all six hearts, selective dofetilide and pinacidil infusion resulted in delayed trefr and Tup in the non-LAD region, and shortened invasive trefr and noninvasive Tup in the LAD region, respectively (panel B and C). Over all 59 observations, Tup showed high agreement with trefr (values close to line of identity, panel D) with strong correlation (r = 0.91). This finding was independent of T-wave polarity (positive, negative or biphasic). Conclusion The moment of steepest upslope of the T-wave in a noninvasively reconstructed UEG accurately reflects end of local refractoriness in intact hearts, in case of pronounced RT dispersion. Under these circumstances, when local RT is defined by moment of re-excitability (allowing to link it to conduction block and re-entry), ECGI T-wave upslope can be taken as a truthful marker for local RT. Abstract Figure. Results

PROTECTION OF CENTRAL AND PERIPHERAL ORGANS IN AORTIC SURGERY

The introduction into clinical practice of hypothermic circulatory arrest, both in the non−perfusion version and with an artificial circulation, was the beginning of active use of systemic hypothermia as an effective element of cerebral and visceral protection during combined cardiac surgeries, including in aorta pathology. To evaluate ways of protecting visceral organs and spinal cord, namely the "no perfusion" technique with drainage of cerebrospinal fluid, lateral aortic compression, left−atrial−femoral bypass, deep hypothermia with cardiac arrest, i.e. hypothermic circulatory arest, bypass grafting, artificial blood circulation and moderate hypothermia in surgery for acute aortic syndrome the results of treatment of the patients with acute bundle aortic aortic abdominal localization were analyzed. There was characterized the proposed and implemented in practice original method of protection, consisting in an access to aorta, which is pressed above the aneurysm at the level of bifurcation, and selective perfusion into the mouth of vessels supplying the internal organs with a custodiol solution with a temperature of 3−4°. All the patients with combined occlusion−stenotic lesions of different arterial pools have aortic prostheses with the inclusion of visceral arteries into bloodstream in different variants. The tendency of the more favorable post−surgery period in the patients to whom the implemented methods of protection were applied. Key words: aortic aneurysm, surgical treatment, organ protection.

The Effect of Preservation Temperature on Liver, Kidney, and Pancreas Tissue ATP in Animal and Preclinical Human Models

The recent advances in machine perfusion (MP) technology involve settings ranging between hypothermic, subnormothermic, and normothermic temperatures. Tissue level adenosine triphosphate (ATP) is a long-established marker of viability and functionality and is universal for all organs. In the midst of a growing number of complex clinical parameters for the quality assessment of graft prior to transplantation, a revisit of ATP may shed light on the underlying reconditioning mechanisms of different perfusion temperatures in the form of restoration of metabolic and energy status. This article aims to review and critically analyse animal and preclinical human studies (discarded grafts) during MP of three abdominal organs (liver, kidney, and pancreas) in which ATP was a primary endpoint. A selective review of recent novel reconditioning approaches relevant to mitigation of graft ischaemia-reperfusion injury via MP and for different perfusion temperatures was also conducted. With a current reiterated interest for oxygenation during MP, a re-introduction of tissue ATP levels may be valuable for graft viability assessment prior to transplantation. Further studies may help delineate the benefits of selective perfusion temperatures on organs viability.

Accuracy of direct magnetic resonance imaging-guided placement of drug infusion cannulae

An intraoperative MRI (iMRI)–compatible system has been developed for direct placement of convection-enhanced delivery (CED) cannulae using real-time imaging. To establish the precision and feasibility of this technology, the authors analyzed findings in patients who underwent direct iMRI CED cannula placement. Three consecutive patients underwent iMRI-guided placement of CED infusion cannulae (6 cannulae) for treatment of diffuse intrinsic brainstem glioma (2 patients) or Parkinson's disease (1 patient). Convective infusion cannulae were guided to the target using the ClearPoint iMRI-based navigation platform (MRI Interventions, Inc.). Placement accuracy was analyzed. Real-time iMRI during infusion cannula insertion allowed for monitoring of trajectory accuracy during placement. During cannula insertion, no reinsertions or changes due to errors in targeting were necessary. The mean radial error was 1.0 ± 0.5 mm (± SD). There was no correlation between the total length of the planned trajectory and the radial error (Pearson's coefficient: −0.40; p = 0.5). The mean anteroposterior and lateral errors were 0.9 ± 0.5 and 0.3 ± 0.2 mm, respectively. The mean in-plane distance error was 1.0 ± 0.4 mm. The mean tip error (scalar distance between the planned target and actual tip) was 1.9 ± 0.9 mm. There was no correlation between the length of the planned trajectory and any of the measured errors. No complications were associated with cannula placement. Real-time iMRI-based targeting and monitoring of infusion cannula placement is a safe, effective, and accurate technique that should enable more selective perfusion of brain regions.