In vivo effects of contrast media on coronary thrombolysis.

OBJECTIVES: The aim of the present study was to evaluate the influence of radiographic contrast media (CM) on alteplase-induced coronary thrombolysis. BACKGROUND: Contrast media inhibit fibrinolysis in vitro and interact with endothelial cells, platelets and the coagulation system. The in vivo effects of CM on thrombolysis are not known. METHODS: Occlusive coronary artery thrombosis was induced in 4 groups of 10 dogs by the copper coil technique. After 70 min of occlusion the dogs were randomized to intracoronary injection of 2 ml kg(-1) of either saline, a low-osmolar ionic CM (ioxaglate), a low-osmolar nonionic CM (iohexol) or a high-osmolar ionic CM (amidotrizoate). Thrombolysis with alteplase and co-therapy with aspirin and heparin was initiated after 90 min of occlusion. The coronary artery flow was monitored with an electromagnetic flowmeter throughout the experiment. RESULTS: Iohexol and amidotrizoate, but not ioxaglate, were associated with longer reperfusion delays (time to optimal reperfusion: 67+/-48 min and 65+/-49 min, respectively, vs. 21+/-11 min after placebo; p < 0.05) and shorter periods of coronary perfusion (optimal perfusion time: 21+/-26 min and 21+/-28 min, respectively, vs. 58+/-40 min after placebo; p < 0.05). No significant differences were observed between groups with regard to activated partial thromboplastin times, circulating thrombin-antithrombin III complex concentrations and fibrinogen. CONCLUSIONS: In this animal model administration of iohexol and amidotrizoate before thrombolysis significantly delayed reperfusion. This interaction should be considered in the design of clinical trials of thrombolytic therapy that evaluate coronary artery patency and in patients receiving local infusions of fibrinolytic agents.

Repeated stunning precedes myocardial hibernation in progressive multiple coronary artery obstruction.

OBJECTIVE: The aim of this study was to characterize a regional myocardial flow-function relationship in collateral dependent myocardium produced by multiple coronary artery obstruction. METHODS: Ameroid constrictors were placed around the proximal right (RC) and circumflex (CX) coronary arteries and a silicon tubing cuff around the proximal LAD (left anterior descending artery) (luminal stenosis +/- 77%) in 18 dogs. Weekly two-dimensional echocardiography was performed for regional function (anterior [A], inferoposterior [IP], wall thickening [WT]), and fractional shortening (FS). Colored microspheres injected at baseline and before sacrifice, before and after dipyridamole (0.5 mg/kg) injection, determined resting flow (RF) and coronary reserve (CR), respectively. RESULTS: Coronary angiography performed at four weeks after surgery confirmed occlusion of RC and CX with collateralization and a tight stenosis of LAD. Initially, an episodic reduction in A and IP WT was observed which became persistent later (AWT: 16 +/- 3%; IPWT: 16 +/- 4%, FS: 20 +/- 4%, p < 0.005 vs. baseline [BS]). With dobutamine a biphasic response (improvement in A and IP WT between 5-15 and dysfunction between 20-30 microg/kg/min) was observed. Seven dogs were sacrificed at eight weeks and showed normal RF but reduced transmural CR (A: 75 +/- 18%; IP: 46 +/- 22% of control). Seven dogs underwent PTCA of the LAD at eight weeks and showed gradual improvement in AWT with normalization at 12 weeks (AWT: 30 +/- 5%, p < 0.001 vs. eight weeks). At sacrifice RF and CR in the A wall were normal but there was reduced subendocardial RF in the IP region (64% of BS). Further, biopsy samples showed normal histological findings and high energy phosphate content in all dogs. Radioligand binding assays using 125I-iodocyanopindolol showed downregulation of beta-adrenergic receptor density in the dysfunctional regions compared with control. CONCLUSIONS: In this canine model of viable, collateral dependent and reversibly dysfunctional myocardium, there was early episodic dysfunction followed by persistent dysfunction which was initially associated with normal RF and later with subendocardial hypoperfusion.

M cells and transmural heterogeneity of action potential configuration in myocytes from the left ventricular wall of the pig heart.

OBJECTIVE: Heterogeneity of action potential configuration in the left ventricle (LV), and the contribution of M cells to it, has been observed in the human heart and is important for arrhythmogenesis. Whether the pig heart has similar properties remains a controversial but important issue as the pig heart is currently under study for use in xenotransplantation. METHODS: Single myocytes were enzymatically isolated from the epicardium (EPI, ncells = 29), midmyocardium (MID, ncells = 38), and endocardium (ENDO, ncells = 13) of the free LV wall (npigs = 26, 14-22 weeks old, 55-80 kg), and studied at different stimulation rates during whole-cell recording (normal Tyrode's solution, K(+)-aspartate-based pipette solution, 50 microM K5fluo-3 as [Ca2+]i indicator, 37 degrees C). Standard six-lead ECGs were recorded from anesthetized pigs. RESULTS: The action potential duration (APD) was not significantly different at 0.25 Hz vs. 2 Hz for the majority of cells in all three layers. However, a subpopulation of cells behaved like M cells and had a very steep frequency response (APD90 at 0.25 Hz 538 +/- 30 ms, vs. 337 +/- 9 ms at 2 Hz, P < 0.05, n = 22). These cells were found predominantly in the MID layer (34% of cells), but also (24%) in EPI. M cells had a more pronounced spike-and-dome configuration, with a significantly larger phase 1 magnitude and plateau voltage. The frequency response of these parameters was different from the other cell types. [Ca2+]i transients tended to be larger in M cells. For the in vivo ECG of anesthetized pigs, the QT time was close to the APD90 of M cells, and J waves were seen in 7/12 recordings. CONCLUSIONS: In young adult pigs, M cells can be identified by a steep frequency response of the APD and by a spike-and-dome configuration. These cells are mostly, but not exclusively, found in the midmyocardium, and could contribute to the ECG characteristics. Their properties may however be different from those of other species, including humans.

Quantification of the spectrum of changes in regional myocardial function during acute ischemia in closed chest pigs: an ultrasonic strain rate and strain study.

The objectives of this study were to define the spectrum of regional myocardial function changes during acute ischemia in closed chest animals by using newly developed ultrasonic strain rate and strain indexes derived from regional color Doppler myocardial imaging (CDMI) velocity data. Myocardial ischemia was induced in 18 pigs either with acute total 20-second occlusions (group 1, n = 12) or graded hypoperfusion (40 to 0 mL/min, group 2, n = 6) of the circumflex coronary artery. In addition, a dobutamine challenge (5 to 10 microg/kg per minute) was performed during sustained subtotal ischemia (10 mL/min) in group 2. CDMI acquisitions with parasternal views monitored the myocardial posterior wall function. Regional radial strain rate and strain (epsilon(r)) were measured for systole, isovolumic relaxation, early diastole, and atrial filling, respectively. During total and graded ischemia, epsilon(r) profiles were consistently modified, showing a delayed onset and a decrease in regional systolic thickening as well as increased postsystolic thickening. Radial strain rate and epsilon(r) indexes decreased consistently during systole and early diastole and increased during isovolumic relaxation. End-systolic epsilon(r) could differentiate total ischemia from severe hypoperfusion (10 mL/min), decreasing from 32% +/- 8% to 16% +/- 5% (versus 60% +/- 10% at baseline). During dobutamine infusion (10 microg/kg per minute), end-systolic epsilon(r) tended to decrease from 27% +/- 5% to 18% +/- 11%, whereas postsystolic thickening increased by 2-fold (P <.05). The combined analysis of regional deformation characteristics and global cardiac event timing derived from CDMI data can identify and quantify regional function changes induced by experimental acute ischemia in closed chest pigs. This would appear to be a potentially promising new noninvasive approach to the clinical evaluation of ischemia-induced changes in segmental myocardial function.

Changes in systolic and postsystolic wall thickening during acute coronary occlusion and reperfusion in closed-chest pigs: Implications for the assessment of regional myocardial function.

The aim of the study was to characterize the impact of short-lived total coronary occlusions in closed-chest pigs on radial wall thickening within the "at-risk" myocardial segment by using gray-scale M-mode echocardiography. Twelve pigs underwent a series of 20-second total circumflex coronary artery occlusions with an angioplasty balloon. Myocardial thickening/thinning indexes were continuously monitored before ischemia, during ischemia, and on reperfusion by high-resolution M-mode recordings of the posterior wall obtained from parasternal views. The timing of regional events was compared with global systolic time intervals derived from the color Doppler myocardial imaging velocity data. Each occlusion induced a rapid decrease in end-systolic thickening (epsilon(ES)), closely paralleled by an increase in postsystolic thickening in the ischemic segment. After 20 seconds of ischemia, epsilon(ES) decreased by -86% and postsystolic thickening increased by +100%, whereas maximal thickening decreased only by -34% in comparison with preocclusion values. All wall thickening parameters returned to baseline after 15 seconds of reperfusion. During acute total ischemia in a closed-chest animal model, the changes in regional myocardial function were best characterized by the combined analysis of systolic and postsystolic thickening abnormalities and by their respective timings relative to global cardiac events markers.

Neointimal hyperplasia and late pathologic remodeling in a porcine coronary stent model.

BACKGROUND: Although coronary stenting has been demonstrated to significantly reduce restenosis compared to conventional angioplasty, occurrence of in-stent stenosis still remains one of the major limitations. This study investigates the influence of stent strut diameter on injury, inflammatory response, thrombosis and neointimal hyperplasia in a porcine coronary artery. METHODS: Coil stents made of either a 0.12 mm, 0.15 mm or 0.18 mm wire were randomly implanted in the right coronary arteries of 30 pigs. Quantitative coronary angiography analysis was performed before, immediately after, and 6 weeks following the stenting procedure. At 6 weeks, histopathology for evaluation of injury, thrombosis and inflammation, as well as morphometry for calculation of the neointimal hyperplasia and internal elastic lamina area were performed. RESULTS: Quantitative coronary analysis showed similar quantitative data before and after stent placement in the three groups. At 6 weeks, however, a significantly bigger MLD was found in the 0.18 mm group. Morphometric analysis at 6 weeks confirmed these results, showing a significantly bigger lumen area in both the 0.18 mm (1.71 +/- 0.66 mm2) and 0.15 mm (1.36 +/- 0.53 mm2) groups compared to the 0.12 mm group (0.71 +/- 0.38 mm2). The calculated neointimal hyperplasia was similar in the three groups (0.12 mm: 1.93 +/- 0.51 mm2; 0.15 mm: 1.68 +/- 0.63 mm2; and 0.18 mm: 2.16 +/- 1.48 mm2). The internal elastic membrane area, however, was significantly bigger in the 0.18 mm (3.87 +/- 1.39 mm2) compared to the 0.12 group (2.65 +/- 0.53 mm2). CONCLUSION: These results suggest that pathologic remodeling can also play an important role in late lumen loss after stent implantation.

Evaluation of the biocompatibility of two new diamond-like stent coatings (Dylyn) in a porcine coronary stent model.

UNLABELLED: Hydrogenated diamond-like carbon films (DLC, a-C:H), deposited using plasma-assisted or ion beam-assisted techniques, offer great potential as self-lubricating coatings in many tribological applications. Additionally, studies on biocompatibility have shown that DLC is an inert, impervious hydrocarbon with properties suitable for use in the biomedical field. One particular class of modified DLC coatings are diamond-like nanocomposite coatings (DLN or Dylyn , Bekaert, Kortrijk, Belgium), which offer promising solutions for many industrial applications. In this study, the biocompatibility of two diamond-like stent coatings are evaluated in a porcine coronary stent model. METHODS: Either coated or non-coated stents were randomly implanted in two coronary arteries of 20 pigs so that each group contained 13 stented arteries. Pigs underwent a control angiogram at 6 weeks and were then sacrificed. Quantitative coronary analysis before, immediately after stent implantation, and at 6 weeks was performed using the semi-automated Polytron 1000 system (Siemens, Erlangen, Germany). Morphometry was performed using a computerized morphometric program. Angiographic analysis showed similar baseline selected arteries and post-stenting diameters. At 6-week follow-up, there was no significant difference in minimal stent diameter. Histopathology revealed a similar injury score in the 3 groups. Inflammation was significantly increased in the DLN-DLC coating group. Thrombus formation was significantly decreased in both coated stent groups. Neointimal hyperplasia was decreased in both coated stent groups; however, the difference with the non-coated stents was not statistically significant. Area stenosis was lower in the DLN-coated stent group than in the control group (41 +/- 17% vs. 54 +/- 15%; p = 0.06). CONCLUSION: The results indicate that the diamond-like nanocomposite stent coatings are compatible, resulting in decreased thrombogenicity and decreased neointimal hyperplasia. Covering this coating with another diamond-like carbon film (DLC) resulted in an increased inflammatory reaction and no additional advantage compared to the single-layer diamond-like nanocomposite coating.

[Treatment of chronic alcoholic pancreatitis with a new acid-resistant pancreatin product]. / Az alkoholos eredetü idült hasnyálmirigy-gyulladás kezelése újabb savrezisztens pancreatin készítménnyel.

The authors summarised pathophysiology and therapy possibility of the chronic alcoholic pancreatitis. They introduce a new product of pancreatin use for treatment of chronic alcoholic pancreatitis. The aim of this prospective study was to asses the efficacy of this new drug in the treatment of chronic alcoholic pancreatitis. The treatment was carried out by new pancreatin product containing 10,000 FIP U lipase, 9000 FIP U amylase, and 500 FIP E protease. During the study 30 patients--suffering from alcoholic pancreatitis--were treated. They received, two tablets three times daily in a period of two weeks. The following parameters were observed and compared before and after the period of treatment: complaints of the patients, the characteristics of the stool (daily weight, frequency, fat contents, consistency) the change of the body weight and degree of abdominal pain. These parameters were compared using a score-system, before and after the period of treatment. The authors could analyse the data of 21 patients. It was proved that there was a significant decrease in frequency, daily weight and fat contents of the stool and in abdominal pain. There was not significant change in the body weight. The authors concluded that this new product is a good pancreatin preparation which is useful and suitable for effective treatment of chronic alcoholic pancreatitis, if the patient keeps abstinence.

Protein kinase C expression and subcellular distribution in chronic myocardial ischemia. Comparison of two different canine models.

We studied protein kinase C (PKC) isozyme expression and activity distribution in two models of chronically ischemic canine myocardium: (1) single vessel obstruction (SVO), produced by tight stenosis of LAD followed by preconditioning and acute ischemia (40 min); (2) three vessel obstruction (3VO), produced by LAD-stenosis and gradual occlusion of right coronary artery and left circumflex. In both models after 8 weeks of chronic ischemia the dogs were either sacrificed or had PTCA of the LAD with a follow up of another 4 weeks. Control dogs were sham operated. PKC activity was measured in subcellular fractions of tissue samples from anterior and posterior regions in the presence of histone and gamma-[32P]-ATP. PKC isozymes were detected by Western blotting. All regions perfused by the obstructed coronaries were dysfunctional at 8 weeks when compared to baseline, with improvement of anterior wall function after PTCA of LAD. PKC activity was elevated in the membrane fraction of SVO, but unchanged in the 3VO model. PKCs alpha, epsilon, and zeta prevailed in cytosol fraction of the controls (cytosol/membrane ratios were +/- 3.34, 1.38 and 4.56 for alpha, epsilon and zeta, respectively), consistent with PKC activity distribution, while delta was not detected. There was no significant difference between the groups concerning the relative membrane amount of the isozymes. PKCs alpha and epsilon were decreased in the cytosol fraction of both models at 8 weeks (for anterior region, by 56 and 57% in SVO and by 49 and 46% in 3VO, respectively) without there being any differences between anterior and posterior regions, and were low also in the PTCA group. PKC zeta distribution however varied between the two models. The amount of PKC zeta isozyme was downregulated by 45% after 8 weeks of chronic ischemia and returned towards the control values after PTCA in the anterior region of SVO, while it did not change in anterior wall after 8 weeks in 3VO but was significantly decreased (by 47%) in posterior region after PTCA. In conclusion, our results suggest modified PKC signalling in chronically ischemic canine myocardium.

Assessment of myocardial viability in a porcine model of chronic coronary artery stenosis with dual dose dobutamine magnetic resonance imaging.

In a non-surgical porcine coronary stenosis model resulting in chronic left ventricle dysfunction, we aimed in this study to evaluate the potential of magnetic resonance imaging (MRI) to distinguish dysfunctional but viable from necrotic myocardium by using multiple levels of dobutamine inotropic stimulation during a cine MRI protocol (F.P. van Rugge et al. Circulation 1994; 90: 127-138). We compared our results with histopathology. We were able to demonstrate a biphasic effect at increasing doses of dobutamine in a subgroup of animals with a high-grade coronary stenosis, while in another subgroup the coronary stenosis produced a chronic myocardial infarction, in which no functional recovery could be obtained. In this experimental protocol, dual dose dobutamine MRI proved to be an accurate and reproducible technique to perform viability studies in chronic obstructive coronary artery disease. It permits distinguishing chronic ischemic, but viable myocardium from infarcted tissue. The detection of chronically underperfused but potentially salvageable myocardium is of significant clinical importance since it may aid in determining which patients are eligible for revascularization.

Intravascular low-power red laser light as an adjunct to coronary stent implantation: initial clinical experience.

Low-power red laser light (LPRLL) irradiation enhances endothelial cell growth in vitro and in vivo and reduces restenosis in animal models. The present study reports the preliminary clinical experience in our center. Eighty-one patients were treated with LPRLL, 30 mW/1 min, for in-stent restenosis (n = 27), elective stenting for recurrent restenosis (n = 16), and stenting for treatment of a suboptimal PTCA result (n = 38). All interventions were successful and no major adverse events due to LPRLL therapy were observed. At follow-up, 12 patients (14.8%) underwent an early control coronarogram due to target vessel restenosis. At 6 months, another 20 patients showed a significant restenosis of the target vessel. Preliminary clinical evaluation demonstrates that LPRLL is feasible and safe. The preliminary results suggest that LPRLL results in a decrease of in-stent restenosis when used during primary stenting.

Optimal dosing of intravascular low-power red laser light as an adjunct to coronary stent implantation: insights from a porcine coronary stent model.

BACKGROUND: It is believed that restenosis following coronary interventions is the result of endothelial denudation that leads to thrombus formation, vascular remodeling, and smooth muscle cell proliferation. Low-power red laser light (LPRLL) irradiation enhances endothelial cell growth in vitro and in vivo, and reduces restenosis in animal models. The present study investigated the optimal dose of intravascular LPRLL therapy in the prevention of in-stent stenosis in a porcine coronary stent model. METHODS AND RESULTS: Selected right coronary artery segments were pretreated with a LPRLL balloon, delivering a dose of 0 mW during 1 min (group 1, n = 10), 50 mW during 1 min (group II, n = 10), or 100 mW during 1 min (group III, n = 10) before stenting. Quantitative coronary analysis of the stented vessel was performed before stenting, immediately after stenting, and at 6 weeks follow-up. The pigs were sacrificed, and histologic and morphometric analyses were conducted. At 6 weeks, minimal luminal stent diameter was significantly narrower in the control group compared to the 50-mW dose group (p < 0.05). These results were confirmed by morphometric analysis. Neointimal area was also significantly decreased in the 50-mW dose group. CONCLUSIONS: Intravascular LPRLL contributes to reduction of angiographic in-stent restenosis and neointimal hyperplasia in this animal model. The optimal dose using the LPRLL balloon system seems to be approximately 5 mW delivered during 1 min.

Experimental Evaluation of a New Tubular Coronary Stent (V-Flexª).

The safety, efficacy, angiographic and histological effects of a new 316 L, SS seamless stainless steel tubular stent (V-Flexª, Global Therapeutics, Broomfield, Colorado) was evaluated in a porcine coronary and peripheral artery model. Implantation in the right coronary artery was successful in all 16 pigs. Eight pigs were angiographically controlled after 6 weeks and then sacrificed for morphometric analysis. All stented coronary vessels were widely patent at this moment and morphometric analysis showed only a mild fibromuscular neointimal hyperplasia resulting in a neointimal hyperplasia of 1.15 +/- 0.38 mm2. The remaining 8 pigs were controlled and sacrificed at 12 weeks. At that time, all stented vessels were patent and neointimal hyperplasia was 1.22 +/- 0.34 mm2. Comparison with the Palmaz-Schatzª coronary stent (Cordis, Miami, Florida) in a porcine peripheral artery model demonstrated significantly less neointimal hyperplasia at 6 weeks (1.11 +/- 0.73 vs. 2.40 +/- 0.36, p = 0.001) and at 12 weeks (1.53 +/- 0.42 vs. 2.47 +/- 0.63, p = 0.003) for the V-Flex stent. In conclusion, V-Flex coronary stent implantation in a porcine coronary and peripheral arteries results in a high procedural success rate without subacute thrombotic occlusions, despite no further anticoagulation nor antiplatelet therapy. Six and 12 week histopathological and morphometric evaluation demonstrated only a mild fibromuscular neointimal hyperplasia. Comparison with the Palmaz-Schatz coronary stent in a peripheral artery model showed significantly less neointimal hyperplasia in the V-Flex stent.