Automated Identification of Ventricular Tachycardia Ablation Targets: Multicenter Validation and Workflow Characterization.

Decrement evoked potentials (EPs) (DeEPs) constitute an accepted method to identify physiological ventricular tachycardia (VT) ablation targets without inducing VT. The feasibility of automated software (SW) in the detection of arrhythmogenic VT substrate has been documented. However, multicenter validation of automated SW and workflow has yet to be characterized. The objective of this study was to describe the functionality of a novel DeEP SW (Biosense Webster, Diamond Bar, CA, USA) and evaluate the independent performance of the automated algorithm using multicenter data. VT ablation cases were performed in the catheterization laboratory and retrospectively analyzed using the DeEP SW. The algorithm indicated and mapped DeEPs by first identifying capture in surface electrocardiograms (ECGs). Once capture was confirmed, the EPs of S1 paces were detected. The algorithm checked for the stability of S1 EPs by comparing the last 3 of the 8 morphologies and attributing standard deviation values. The extra-stimulus EP was then detected by comparing it to the S1 EP. Once detected, the DeEP value was computed from the extra-stimulus and displayed as a sphere on a voltage map. A total of 5,885 DeEP signals were extracted from 21 substrate mapping cases conducted at 3 different centers (in Spain, Canada, and Australia). A gold standard was established from ECGs manually marked by subject experts. Once the algorithm was deployed, 91.6% of S2 algorithm markings coincided with the gold standard, 1.9% were false-positives, and 0.1% were false-negatives. Also, 6.4% were non-specific DeEP detections. In conclusion, the automated DeEP algorithm identifies and displays DeEP points, revealing VT substrates in a multicenter validation study. The automation of identification and mapping display is expected to improve efficiency.

The Rapid Prediction of Focal Wavefront Origins: Integration With a 3-Dimensional Mapping System.

OBJECTIVES: This study assessed the accuracy of an algorithm that predicts the origin of focal arrhythmias using a limited number of data points. BACKGROUND: Despite advances in technology, ablations can be time-consuming, and activation mapping continues to have inherent limitations. The authors developed an algorithm that can predict the origin of a focal wavefront using the location and activation timing information in 2 pairs of sampled points. This algorithm was incorporated into an electroanatomic mapping (EAM) system to assess its accuracy in a 3-dimensional clinical environment. METHODS: EAM data from patients who underwent successful ablation of a focal wavefront using the CARTO3 system were loaded onto an offline version of the software modified to contain the algorithm. Prediction curves were retrospectively generated. Predictive accuracy, defined as the distance between true and predicted origin wavefront origins, was measured. RESULTS: Seventeen wavefronts in as many patients (2 with atrial tachycardia, 3 with orthodromic re-entrant tachycardia, 8 with premature ventricular complex and/or ventricular tachycardia, 4 with focal pulmonary vein isolation breakthroughs) were studied. Thirty-three origin predictions were attempted (1.9 ± 0.4 per patient) using 132 points. Predictions were successfully calculated in 31 of 33 (93.9%) attempts and were accurate to within 5.7 ± 6.9 mm. Individual prediction curves were accurate to within 3.0 ± 4.7 mm. CONCLUSIONS: Focal wavefront origins may be accurately predicted in 3 dimensions using a novel algorithm incorporated into an EAM system.

Evaluation of inotropic changes in ventricular function by NOGA mapping: comparison with echocardiography.

Assessment of left ventricular (LV) function in the catheterization laboratory is important to optimize treatment decisions and guide catheter-based local therapies. NOGA electromechanical mapping was developed to assess LV contraction during catheterization; however, quantitative analysis of its "local shortening" (LS) algorithm and direct comparison with conventional methods are lacking. We evaluated the accuracy of NOGA-based regional and global function by examining its ability to detect pharmacologically induced changes in contractility compared with echocardiography. Ten anesthetized pigs were paced to ensure a constant heart rate throughout the experiment. Electromechanical maps of the LV and short-axis echocardiograms were obtained 1) at baseline, 2) during intravenous dobutamine, and 3) after intravenous propranolol. NOGA LS and ejection fraction (EF) consistently increased under dobutamine and decreased after propranolol. NOGA LS and NOGA and echocardiography circumferential shortening correlated highly with one another (r > 0.80), as did NOGA EF with echocardiography EF (r = 0.92), although absolute values differed somewhat. Thus NOGA-based global and regional function correlates closely with echocardiography and is sensitive to changes in contractility, but, at the upper end of the scale, LV function is underestimated.

Temporal changes in the endocardial ST segment during the evolution of myocardial infarction in dogs.

Acute coronary occlusion causes ST-segment elevation on the body surface ECG and on the epicardial electrogram in the territory supplied by that artery. The occurrence and significance of endocardial ST changes have not been studied. The NOGA electromechanical mapping was performed on eight anesthetized dogs at baseline, immediately after occlusion of the LAD, and again at 5 hours to assess regional changes in the ST segment. At 3 days and 4 weeks the ventricles were remapped for comparison. Regional unipolar ST-segment elevation was measured for each zone from NOGA maps at 0, 80, and 120 ms after the J point. ST segments rose immediately in the infarct zones, as demarcated by echocardiography, compared to remote zones, but by 3 days had dropped below, and at 4 weeks returned to baseline values. Immediately postocclusion, ST elevation at 120 ms best differentiated between normal versus abnormal echo scores (concordance = 0.80), probably by correcting for pressure induced ST elevation. In conclusion, acute endocardial ST-segment changes occur in the infarct zone in the dog, showing a distinctive temporal evolution.

Technical delivery of myogenic cells through an endocardial injection catheter for myocardial cell implantation.

BACKGROUND: The next clinical frontier in the therapeutics of ischemic heart disease may involve the development and delivery of specific molecules and cells into the myocardium. The aim of the present study was to evaluate the efficiency and safety of the MyoStar injection catheter (Biosense-Webster Inc.) that has recently been developed to deliver molecules and cells to the myocardium. The 8 Fr (110 cm length) catheter comprises a navigation sensor with a 27 gauge needle at the distal tip. METHODS: Mouse myogenic cells (C2) were delivered to a tissue culture dish through different modalities: a standard laboratory pipette, a syringe needle (27 gauge) and the injection catheter. The cells were counted and monitored for growth and differentiation in the tissue culture immediately after delivery and two, three and six days later. Cells that were injected through a regular syringe needle or through the injection catheter demonstrated the same capacity to proliferate in tissue culture up to six days. RESULTS: The behavior of the cells in culture (fusion) was identical for the cells delivered to the tissue culture by a pipette or by the injection catheter. CONCLUSION: The results of the present study indicate that delivery of cells through the MyoStar injection catheter is a method with no significant loss or adverse effects to the cells along the path of the catheter. The catheter, which possesses both injection and navigation capabilities, can be used to deliver cell therapy to patients with ischemic heart disease.