Endocardial Imaging Research Articles

Epicardial left atrial appendage occlusion with a new medical device: assessment of procedural feasibility, safety and efficacy in a large animal model

BackgroundLeft atrial appendage occlusion (LAAO) represents a treatment alternative to anticoagulation in patients with atrial fibrillation. We evaluate a novel device for epicardial LAAO in a translational canine model.MethodsNine hounds (n = 9) were used to assess usability, safety, and efficacy of the TigerPaw Pro (TPP) device for epicardial LAAO. Following baseline imaging (intra-cardiac echocardiography (ICE) and angiography) and intraoperative visual inspection, usability was tested via a ``closure/re-opening`` maneuver followed by deployment of a total of twenty TPP devices (n = 20) on the left and right atrial appendages respectively. Procedural safety was evaluated by assessing for adverse-events via direct Epicardial inspection and endocardial imaging. Efficacy evaluation included assessment of device positioning, presence of residual stumps and completeness of closure. Post-mortem evaluation was performed to confirm safety and efficacy.ResultsUsability testing of all TPP devices was successful (n = 20;100%, delivery-time range 22–120 s) without any procedural adverse-events (tissue damage or tears, bleeding, vessel-impingement, structural impact). All devices fully traversed the ostium (n = 18) or appendage body (n = 2), and conformed smoothly to adjacent cardiac anatomy. In nineteen deployments (n = 19;95%), all device connector pairs were fully engaged, while in one TPP device the most distal pair remained unengaged. ICE and post-mortem inspections revealed complete closure of all appendage ostia (n = 18;100%) and only in one case a small residual stump was detected. Intraoperative safety findings were further confirmed post-mortem. Devices created a nearly smooth line of closure via symmetric endocardial tissue-coaptation.ConclusionsIn this preclinical model, the TPP demonstrated good ease of use for ostial access, ability to re-position (after engagement) and rapid deployment, while achieving safe and effective LAAO.

Field-of-view zoom during a single-shot short-axis image for cardiac contraction correction

Summary Evaluate a new method correcting for cardiac contraction during each single-shot image. Background Cardiac motion during a single-shot image causes blurring along the phase-encode axis and dark rim artefact (1). We attempt to correct for myocardial contraction during short-axis single-shot acquisition, to optimise subendocardial myocardium. Methods A myocardial perfusion sequence (balanced SSFP) was modified to vary field-of-view and in-plane offsets during each single-shot rawdata acquisition to “zoom” in [or out] following myocardial contraction [filling]. FOVzoom varied linearly during raw data acquisition, and for each phase-encode line ps caled the FOV and inplane offsets by factor Sc(p) = 1 + ((Db - De)/De) x (pN/2)/N where Db and De were LV short-axis diameter at the begin and end of the single-shot scan, and N was the total phase encode lines (96) for each single-shot. The diameters Db and De were measured using a shortaxis cine pre-scan in the same slice. The sequence acquired 300x225mm FOV (2.3x2.3x6mm). For in-vitro tests, a conical cup of fluid was imaged in circular cross-section. The slice was shifted along the cone during acquisition, so that the apparently changing diameter modelled contraction of a short-axis LV. In healthy volunteers without contrast agent, T2-preparation was used for endocardial image contrast (1). Each 200ms perfusion image was acquired during ventricular contraction, starting 80ms after the R-wave, repeated with and without FOV-zoom. Results Correct operation of the FOV-zoom was confirmed (Figure 1) including in-plane offsets. Gibbs artefact remained unfiltered in all images; the optimum setting of rawdata edge filters during FOV-tracking remains unsolved. Ironically, if FOV-zoom is setup correctly it clarified Gibbs artefact as well as the border. Blurring of the endocardial borders along the phase-encode direction (Figure 2) was reduced by FOV-zoom. The improvement was less than expected given the large change in ventricular diameter (top row) during the image. Although diastolic filling motion is most rapid, the myocardial sectors are more asynchronous even in healthy subjects, and FOV-zoom would be unsuccessful. Even for the more synchronous contraction, the origin of contraction was sometimes midway along the septal endocardial border, and this point must be positioned at the center of the FOV-zoom. Distortion of other tissues by FOV-zoom remained local causing no artefacts at the heart. FOV-zoom might be applied to other long singleshot sequences (e.g. 3D perfusion).

Intraoperative Doppler Tissue Imaging Is a Valuable Addition to Cardiac Anesthesiologists’ Armamentarium: A Core Review

Endocardial motion and surface/volume changes during the cardiac cycle are echocardiographic methods for regional (analysis of wall motion) and global (fractional area change, stroke volume, and ejection fraction) evaluation of cardiac function. These conventional methods can be subjective, and/or time consuming and, depending upon circumstances, may divert the anesthesiologist's attention from intraoperative activities. Doppler tissue imaging (DTI) is a novel echocardiographic technique, which displays and measures systolic and diastolic velocity from a myocardial region. DTI is simple to perform and independent of adequate endocardial imaging. The numeric information (velocity or time intervals) is easily obtained and measured. Assessment of systolic and diastolic function on regional (detection of ischemia) as well as global level (ejection fraction, grading of diastolic dysfunction) and evaluation of filling pressure can be derived from DTI signals and used by any practicing cardiac anesthesiologist. This review describes the principles, imaging modalities, and clinical applications of DTI.

Novel visualization of intracardiac pacing lead extractions: methodologies performed within isolated canine hearts

Several methodologies are typically employed to extract chronically-implanted pacing leads including: laser catheter systems, radio frequency catheters, mechanical cutting catheters, and/or direct traction. In the present study, Visible Heart(R) methodologies were employed to obtain novel internal and external views of such extractions. Utilizing standard cardioplegia procedures, canine hearts (n = 3) with chronically-implanted endocardial pacing leads were explanted to a unique isolated heart apparatus. Modified Krebs-Henseleit buffer allowed for clear endocardial imaging with endoscopic video cameras inserted into the cardiac chambers. Leads were extracted using: (1) laser system with sheath; (2) dissection sheath with incorporated bipolar tungsten electrode; (3) non-powered mechanical sheath; or (4) direct traction. Resultant images provide a novel perspective regarding lead extraction methodologies and the imposed force on an encapsulated lead and on the great vessels and/or heart itself; this understanding may improve the outcome and safety of future lead extractions.

In Vitro Studies of Human Hearts

Isolated mammalian hearts have been used in numerous studies that have led to many important discoveries in cardiac physiology, pharmacology, and surgery. Multiple methods of perfusion have been described including retrograde and/or antegrade flows and crystalloid or blood perfusates. Furthermore, multiple species have been utilized for such studies including the following: rat, rabbit, guinea pig, canine, and swine. The objective of this study was to describe a unique isolated heart preparation, utilizing human hearts not viable for transplant, which allows for physiologic perfusion and endocardial imaging. Utilizing standard cardiac transplantation procedures, 12 human hearts deemed not viable for transplant were explanted to an isolated heart apparatus. A clear, modified Krebs-Henseleit buffer was used as a blood substitute, which allowed for endocardial imaging utilizing 6.0 mm endoscopic video cameras inserted into the cardiac chambers. The hearts were perfused in Langendorff (retrograde) and/or working (physiologic) mode. Eleven of 12 hearts achieved the following performance in working mode: peak left ventricular pressure of 21.5 to 75.8 mm Hg, with an average of 42.7 +/- 19.9 mm Hg. Intracardiac anatomical imaging was possible in all hearts, providing unique views of normal and pathological endocardial anatomy as well as biomedical device-heart interactions. We have described a unique isolated heart preparation with which we have successfully reanimated 11 human hearts deemed not viable for transplant, perfused them by working mode, and performed intracardiac anatomical imaging. This approach provides a novel means for obtaining images of functional human cardiac anatomy and various types of unique biomedical assessments.

Three-dimensional and endocardial imaging of the coronary sinus for cardiac resynchronization therapy.

Three-dimensional and endocardial imaging of the coronary sinus for cardiac resynchronization therapy.

Endocardial imaging of the left atrium in patients with atrial fibrillation.

Endocardial imaging of the left atrium in patients with atrial fibrillation.

Rapid Serodiagnosis of Gram-positive Bacterial Endocarditis

Objectives: To characterize a serological test for diagnosing endocarditis caused by Gram-positive cocci.Methods: We have developed an indirect enzyme-linked immunosorbent assay (ELISA) for the serological detection of Gram-positive infections. The test measures serum IgG directed towards lipid S, a recently identified exocellular glycolipid antigen which is related to lipoteichoic acid. We have previously shown the test to be of value in serodiagnosis of central venous catheter-associated sepsis and infection of orthopaedic prostheses caused by coagulase-negativestaphylococci. We now describe the application of this test in endocarditis.Results: Serum IgG levels to lipid S were significantly elevated in 34 patients with Gram-positive bacterial endocarditis confirmed as 'definite' by the Duke criteria as compared to 50 control patients. The test had a sensitivity of 88% and a specificity of 88%.Conclusions: The assay is independent of culture results or endocardial imaging, making it complementary to currently used investigations. It may therefore be possible to refine the current Duke criteria for diagnosing endocarditis. We describe an algorithm which incorporates lipid S serology into a positive diagnostic strategy.

Two-dimensional echocardiographic identification of left ventricular pseudoaneurysm

Nine patients with proved left ventricular pseudoaneurysm after transmural myocardial infarction were studied by two-dimensional echocardiography. In all patients two-dimensional echocardiography successfully displayed the pseudoaneurysm. The unique two-dimensional echocardiographic characteristics of pseudoaneurysm include: (1) a sharp discontinuity of the endocardial image at the site of the pseudoaneurysm communication with the left ventricular cavity, and (2) the presence of a relatively narrow orifice in comparison with the maximum diameter of the pseudoaneurysm fundus; visualization of the maximum diameter of the pseudoaneurysm fundus frequently required a slightly different tomographic view than that required for demonstration of the orifice. The distinctive echocardiographic features of pseudoaneurysm in these patients and technical implications for optimal visualization are described. Most of the pseudoaneurysms we encountered and many of those previously described were located posteriorly. We found the use of an inferior angulated view modified from the standard apical four-chamber view extremely helpful in detecting the orifice in patients with posterior or posterolateral pseudoaneurysms. We conclude that two-dimensional echocardiography is an important technique for diagnosis of left ventricular pseudoaneurysm.

Two-dimensional echocardiographic recognition of left ventricular pseudoaneurysm.

Five consecutive patients with proved left ventricular pseudoaneurysm (PA) and 22 patients with true aneurysm (TA) were studied by two-dimensional echocardiography (2DE). In four of the five patients with PA, 2DE successfully displayed the PA. The unique 2DE characteristics of PA include: (1) a sharp discontinuity of the endocardial image at the site of the PA communication with the left ventricular cavity; (2) a saccular or globular contour of the PA chamber; and (3) the presence of a relatively narrow orifice in comparison with the diameter of the PA fundus. In addition, 2DE detected the presence of thrombotic material within the extraventricular chamber in three of four cases. By deriving the ratios of the end-systolic orifice to diameter measurements for the patients with PA (0.37 +/- 0.07) compared with TA (1.00 +/- 0.08), we found that 2DE reliably differentiated PA from TA (p < 0.001). We conclude that 2DE is a useful noninvasive method for revealing left ventricular PAs and for distinguishing PA from TA. Considering the high risk of spontaneous rupture associated with pseudoaneurysms, this noninvasive capability is of paramount clinical importance.