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Left ventricular electromechanical mapping (LVEM) is a method for mapping the left ventricular cavity in 3 dimensions by use of a catheter that samples points on the endocardial surface. These points provide data on unipolar voltage and linear local shortening, which can then be used to evaluate myocardial ischemia and viability. The new QwikStar multielectrode catheter, which acquires data from multiple points simultaneously, potentially improves map quality and decreases mapping time in comparison with the single-point NogaStar catheter. Our study sought to validate the QwikStar catheter's LVEM capabilities in a porcine model of chronic ischemia. Eight pigs underwent ameroid placement over the proximal left circumflex artery, to induce chronic ischemia. In 60 days, LVEM was performed on each animal with the Noga-Star and QwikStar catheters. Unipolar voltage and linear local shortening results were displayed in 9-segment polar maps. The unipolar voltage data from both maps were then correlated by means of linear regression. There were no adverse events during LVEM. Mapping time was similar for both groups (QwikStar, 44.6 ± 25.62 min; NogaStar, 65.75 ± 25.33 min; P=0.13). Results of mean unipolar voltage maps acquired with the 2 catheters showed a moderate correlation (r =0.59, P <0.001). Selecting segments with more than 6 point samples increased the Pearson coefficient to 0.69 (P <0.001). Our findings show that the QwikStar catheter enables the reproducible performance of LVEM by sampling fewer points, which shortens procedure time, decreases manipulation of the left ventricular cavity, and might increase procedural safety. [ABSTRACT FROM AUTHOR]

In this histological study, we assessed the role of mesenchymal stem cells (MSCs) in the healing process that takes place during the subacute phase of myocardial infarction in dogs. Seven days after occlusion of the left anterior descending coronary artery, adult mongrel dogs received 100 x 10(6) 4'-6-diamidino-2-phenylindole (DAPI)-labeled allogenic bone marrow-derived MSCs by the transendocardial (TE, n=6) and intracoronary (IC, n=4) routes; control dogs (n=6) received no infusion. The dogs were euthanized at 21 days after occlusion. Hearts were excised and sliced from apex to base into four transverse sections, which were divided into nine segments. Paraffin sections from each segment were stained with hematoxylin and eosin, trichrome, picrosirius red, and antibodies against several extracellular matrix components. Frozen sections were immunostained for host cardiac phenotypical markers and analyzed by epifluorescence and deconvolution fluorescence microscopy (DFM). We found less unresolved necrotic myocardium and more extracellular matrix deposition in MSC-treated dogs than in controls 2 weeks after cell delivery. By DFM, no DAPI+ MSC nuclei were observed within native cardiac cells. MSCs delivered during the subacute phase of acute myocardial infarction positively affect healing, apparently by mechanisms other than differentiation into mature native cardiac cells.

Background and Objective: Left ventricular electromechanical mapping (EMM) determines myocardial viability on the basis of endocardial electrograms. The aim of the present study was to validate EMM in differentiating infarcted myocardium from viable myocardium by histopathological analysis., Methods: Sixty days after implanting an ameroid constrictor over the left circumflex artery to create chronic ischemia in 19 pigs, EMM was performed to construct unipolar voltage (UPV), bipolar voltage (BPV) and linear local shortening (LLS) maps. Noninfarcted and infarcted myocardium were identified by histopathology. Threshold determinations comparing noninfarcted tissue with scarred tissue were made by measuring the area under the receiver operating characteristic curves., Results: From the 19 hearts, 149 myocardial segments were divided into noninfarcted myocardium (n=128) and transmural infarct (n=21). UPV, BPV and LLS values (4.7+/-1.2 mV, 2.8+/-2.5 mV and 10.0+/-5.1%, respectively) of infarcted segments were significantly lower than those in noninfarcted myocardium (10.9+/-3.4 mV, 4.5+/-2.4 mV and 15.7+/-9.5%, respectively; P<0.01 for each comparison). The threshold values of UPV, BPV and LLS differentiating noninfarcted from infarcted myocardium were 6.2 mV (98% sensitivity, 95% specificity, 97% accuracy), 2.8 mV (80% sensitivity, 72% specificity, 79% accuracy) and 12.3% (68% sensitivity, 67% specificity, 68% accuracy), respectively. The relative dispersion of voltage was lower for UPV versus BPV., Conclusion: UPV can accurately differentiate infarcted from noninfarcted tissue in the chronic ischemic heart of pigs; however, BPV and LLS results were less accurate.

Background: Intravascular ultrasound (IVUS) can detect atherosclerotic compromise in coronary segments where conventional angiography cannot. However, IVUS is more invasive, expensive and laborious than angiography. We compared the detection of stenosis by IVUS and angiography and identified angiographic predictors of severe luminal stenosis on IVUS in patients with angiographically-intermediate coronary lesions., Methods: Fifty-six patients with myocardial ischemia and intermediate stenosis by quantitative coronary angiography (QCA) underwent IVUS assessment of the culprit artery. The results from IVUS and QCA were compared using the two-tailed unpaired t-test. Multiple regression analysis was performed to identify QCA parameters that could predict the presence of severe stenosis on IVUS, defined as a minimum luminal area (MLA) < or = 4 mm2., Results: A total of 63 stenotic coronary lesions were classified as intermediate by QCA; 68% of these were found to be severe on IVUS. There was a weak correlation between IVUS and QCA with respect to percentage of stenosis, minimum luminal diameter, reference segment diameter and length of atherosclerotic compromise. In contrast, there was a significant difference in the assessment of reference segment luminal diameter, which was 2.83 +/- 0.56 mm by angiography versus 3.45 +/- 0.69 mm by IVUS (p < 0.0001). The only angiographic predictor of the presence of severe coronary stenosis on IVUS was a distal reference segment diameter < or = 2.42 mm., Conclusions: In patients with angiographically-intermediate lesions, the frequency of severe stenosis detected by IVUS was high, indicating that angiography underestimated the severity of stenosis. Distal reference segment diameter was the only predictor of a small MLA and could be used to stratify these lesions into groups with higher and lower risk of severe stenosis.

Aims: The purpose of this preclinical feasibility study was to evaluate a novel integrated platform in which magnetic navigation is used to remotely guide electromechanical mapping of the left ventricle (LV) and transendocardial cell injections. Using an integrated remote system would greatly facilitate intramyocardial delivery of stem cells for treating ischaemic heart disease., Methods and Results: We used the computer-controlled Stereotaxis magnetic navigation system to guide the NOGA electromechanical mapping system in mapping viable myocardium in the LV of seven pigs. We then tested the feasibility of this system to perform transendocardial injections in three of the pigs and to deliver mesenchymal precursor cells (MPCs) to targeted myocardial segments in four of the pigs. The success or failure of each injection was determined by myocardial contrast staining in the first group and by histopathologic analysis in the last group. The mean time (+/-SD) spent mapping the LV for each pig was 49.3+/-10.6 min. The success rate for transendocardial injections was 94.4%, as indicated by myocardial contrast staining. There was a 95.8% success rate for targeted injections of MPCs, and 4',6-diamidino-2-phenylindole-labeled MPCs were detected in all but one segment of one pig. No epicardial haemorrhage or injury was observed, although there was some venous drainage., Conclusions: The integrated Stereotaxis/NOGA system has excellent remote navigability inside the LV cavity while sparing the operator from radiation exposure. This system also allows transendocardial cell injections to be performed with a high success rate. Further studies are needed to define the safety profile of this system for clinical use.