Isolation of pulmonary veins using a thermoreactive implantable device with external energy transfer: Evaluation in a porcine model

BACKGROUND

Pulmonary vein isolation (PVI) is a well-established method for the treatment of symptomatic paroxysmal atrial fibrillation, but is only partly successful with a high rate of electrical reconnection. We introduce a novel technique in which PVI is accomplished by noninvasive heating of a dedicated thermoresponse implant inserted into the pulmonary veins (PV), demonstrated in a porcine model.

METHODS

A self-expanding nitinol-based implant was positioned in the common inferior PV of 11 pigs, using a fluoroscopy-guided transatrial appendage approach. Ablation was performed through contactless energy transfer from a primary extracorporal coil to a secondary heat ring (HR) embedded in the proximal part of the implant. Electrophysiological conduction was assessed prior to and postablation, and at 3 months. Histological samples were obtained acutely (n  =  4) and after 3 months (n  =  7).

RESULTS

In total, 13 PV implants were successfully positioned in the inferior PVs of 11 animals. Ablation was performed without injury of adjacent structures. PVI and bidirectional block was electrophysiologically confirmed in all cases immediately at the time of implantation and 3 months later in seven chronic animals in whom testing was repeated. Marked evidence of ablation around the proximal HR was evident at 3 months postprocedure, with scar tissue formation and only mild neointimal proliferation.

CONCLUSIONS

Successful PVI can be obtained by external electromagnetic heat transfer to a novel pulmonary vein implant.

A preliminary study of pulmonary vein implant applicability and safety as a potential ablation platform in a follow-up study in pigs

BACKGROUND

Recurrence of atrial fibrillation after an ablation procedure remains a major problem which emphasizes the need for improved pulmonary vein isolation techniques.

AIMS

The aim of this study was to describe an implantation procedure of a pulmonary vein-stent which may possibly serve as an ablation technique in the future and to examine stent safety in a follow-up study in pigs.

METHODS AND RESULTS

Eight pigs were catheterized and nine self-expanding nitinol stents were implanted through a transfemoral or transatrial approach into the antra of the pulmonary veins. After 3 months' follow-up, the animals were euthanized for further examination. During the follow-up phase, no complications were observed. Absence of thrombus formation or pulmonary vein wall dissection was noticed during anatomical and histological evaluation of the heart-lung packages. All implants were almost completely covered by neo-intima, of which thickness varied between 0.2 and 3.9 mm.

CONCLUSIONS

Stents can safely be positioned and deployed into the antra of the pulmonary veins without any acute or long-term (3 months) adverse effects. In the future, these implants could function as a permanently implanted ablation device and provide new therapeutic strategies for pulmonary vein isolation in patients with atrial fibrillation.

Self-expanding versus balloon-expandable stents in acute myocardial infarction: results from the APPOSITION II study: self-expanding stents in ST-segment elevation myocardial infarction

OBJECTIVES

This study sought to investigate whether self-expanding stents are more effective than balloon-expandable stents for reducing stent malapposition at 3 days after implantation in patients with ST-segment elevation myocardial infarction undergoing primary percutaneous coronary intervention.

BACKGROUND

Acute myocardial infarction is associated with vasoconstriction and large thrombus burden. Resolution of vasoconstriction and thrombus load during the first hours to days after primary percutaneous coronary intervention may lead to stent undersizing and malapposition, which may subsequently lead to stent thrombosis or restenosis. In addition, aggressive stent deployment may cause distal embolization.

METHODS

Eighty patients with ST-segment elevation myocardial infarction undergoing primary percutaneous coronary intervention were randomized to receive a self-expanding stent (STENTYS, STENTYS SA, Paris, France) (n = 43) or a balloon-expandable stent (VISION, Abbott Vascular, Santa Clara, California; or Driver, Medtronic, Minneapolis, Minnesota) (n = 37) at 9 European centers. The primary endpoint was the proportion of stent strut malapposition at 3 days after implantation measured by optical coherence tomography. Secondary endpoints included major adverse cardiac events (cardiac death, recurrent myocardial infarction, emergent bypass surgery, or clinically driven target lesion revascularization).

RESULTS

At 3 days after implantation, on a per-strut basis, a lower rate of malapposed stent struts was observed by optical coherence tomography in the self-expanding stent group than in the balloon-expandable group (0.58% vs. 5.46%, p < 0.001). On a per-patient basis, none of the patients in the self-expanding stent group versus 28% in the balloon-expandable group presented ≥5% malapposed struts (p < 0.001). At 6 months, major adverse cardiac events were 2.3% versus 0% in the self-expanding and balloon-expandable groups, respectively (p = NS).

CONCLUSIONS

Strut malapposition at 3 days is significantly lower in ST-segment elevation myocardial infarction patients allocated to self-expanding stents when than in those allocated to balloon-expandable stents. The impact of this difference on clinical outcome and the risk of late stent thrombosis need to be evaluated further. (Randomized Comparison Between the STENTYS Self-expanding Coronary Stent and a Balloon-expandable Stent in Acute Myocardial Infarction [APPOSITION II]; NCT01008085).

Compositional volumetry of non-calcified coronary plaques by multislice computed tomography: an ex vivo feasibility study

AIMS

Non-invasive quantitative compositional analysis of coronary plaque would be a major advantage to study coronary artery disease. This study explores the application to use the Hounsfield units (HU) distribution of coronary plaques imaged by multislice computed tomography-coronary angiography (MSCT-CA).

METHODS AND RESULTS

A dedicated computer-assisted method was developed to measure the HU distribution within a coronary plaque by MSCT-CA. To test the feasibility of the method, an ex vivo left anterior descending (LAD) coronary specimen, excised during autopsy, was imaged both by non-enhanced and enhanced MSCT-CA. Quantitative histology was used as a reference. To test the feasibility of the new volumetric analytic method, the MSCT-CA data were compared with volumetric histopathology. The coronary specimen, with a heterogeneously distributed plaque composition without large areas of calcification, was histologically sampled at five different locations, 5 mm apart, where at each location 15 sections were taken at 100 microm intervals, resulting in 75 individual histology sections. Tri-chrome Masson staining was used for histology quantification of three plaque/tissue components: smooth muscle cells (SMC), collagen and calcium. MSCT plaque composition was defined as "lower-HU" or "higher-HU" plaque and "calcium" based on the HU distribution. Comparison of the MSCT defined tissue components against histology showed a good relationship without significant differences.

CONCLUSIONS

This ex vivo study shows the feasibility of using the Hounsfield unit distribution to perform compositional coronary plaque volumetry by MSCT-CA. The results are encouraging.

The percutaneous assessment of regional and acute coronary hot unstable plaques by thermographic evaluation (PARACHUTE) study: a prospective reproducibility and prognostic clinical study using thermography to predict future ischemic cardiac events

Intravascular thermography is currently being considered as a valuable tool in assessing macrophage-rich plaques. Since it is unknown what the prognostic value is of non-obstructive atherosclerotic plaques showing temperature heterogeneity, we designed the PARACHUTE study, a prospective, reproducibility, and prognostic clinical study using thermography in patients presenting with an unstable coronary syndrome. The primary endpoint of the study is the predictive value of temperature heterogeneity towards the occurrence of ischemic coronary events and hospitalization for ischemia and/or angina. The secondary endpoints are the predictive value of high-risk plaques associated with the development of future cardiac events, assessment of safety of the procedure, assessment of temperature reproducibility and heterogeneity in coronary arteries, as defined by the total thermal burden towards the occurrence of any cardiac event. Based on an event rate of death and myocardial infarction at 1 year of 10%, a sample size of 260 patients with presumed coronary artery disease, and positive troponin level who are scheduled to undergo an intervention will be included. All three main epicardiac vessels will undergo angiography and thermography at baseline after revascularization of the flow-limiting vessel. At 12 months, angiography of all vessels and thermography of the vessel with the highest thermographic burden will be performed. Independent core laboratories will assess outcomes and a clinical endpoint committee will assess clinical events.

Re-examining minimal luminal diameter relocation and quantitative coronary angiography--intravascular ultrasound correlations in stented saphenous vein grafts: methodological insights from the randomised RRISC trial

AIMS

Angiographic parameters (such as late luminal loss) are common endpoints in drug-eluting stent trials, but their correlation with the neointimal process and their reliability in predicting restenosis are debated.

METHODS AND RESULTS

Using quantitative coronary angiography (QCA) data (49 bare metal stent and 44 sirolimus-eluting stent lesions) and intravascular ultrasound (IVUS) data (39 bare metal stent and 34 sirolimus-eluting stent lesions) from the randomised Reduction of Restenosis In Saphenous vein grafts with Cypher stent (RRISC) trial, we analysed the "relocation phenomenon" of QCA-based in-stent minimal luminal diameter (MLD) between post-procedure and follow-up and we correlated QCA-based and IVUS-based restenotic parameters in stented saphenous vein grafts. We expected the presence of MLD relocation for low late loss values, as MLD can "migrate" along the stent if minimal re-narrowing occurs, while we anticipated follow-up MLD to be located close to post-procedural MLD position for higher late loss. QCA-based MLD relocation occurred frequently: the site of MLD shifted from post-procedure to follow-up an "absolute" distance of 5.8 mm [2.5-10.2] and a "relative" value of 29% [10-46]. MLD relocation failed to correlate with in-stent late loss (rho = 0.14 for "absolute" MLD relocation [p = 0.17], and rho=0.03 for "relative" relocation [p = 0.811). Follow-up QCA-based and IVUS-based MLD values well correlated in the overall population (rho = 0.76, p < 0.001), but QCA underestimated MLD on average 0.55 +/- 0.49 mm, and this was mainly evident for lower MLD values. Conversely, the location of QCA-based MLD failed to correlate with the location of IVUS-based MLD (rho = 0.01 for "absolute" values--in mm [p = 0.911, rho = 0.19 for "relative" values--in % [p = 0.111). Overall, the ability of late loss to "predict" IVUS parameters of restenosis (maximum neointimal hyperplasia diameter, neointimal hyperplasia index and maximum neointimal hyperplasia area) was moderate (rho between 0.46 and 0.54 for the 3 IVUS parameters).

CONCLUSIONS

These findings suggest the need for a critical re-evaluation of angiographic parameters (such as late loss) as endpoints for drug-eluting stent trials and the use of more precise techniques to describe accurately and properly the restenotic process.

Comparison of assessment of native coronary arteries by standard versus three-dimensional coronary angiography

Vessel foreshortening is a major limitation of standard coronary angiography due to the 2-dimensional representation of 3-dimensional structures. Three-dimensional models may overcome it. The aim of this study was to compare measurements of coronary segments from quantitative coronary angiography (QCA) in an operator-selected "working view" of standard 2-dimensional coronary angiography with those from 3-dimensional coronary angiography (3D-CA) reconstruction models, which are automatically generated from software applied to rotational coronary angiographic acquisitions. Patients who underwent percutaneous coronary intervention were considered. Two or 3 segments of the artery needing treatment were prespecified, using bifurcations as edges. The operator selected a working view from standard angiography as the view best representing each segment. Rotational angiography was performed, allowing 3-dimensional reconstruction of the selected segments. Additionally a marker guidewire (with 4 markers 10 mm away from one another at the distal tip) was used to further measure segment length, and it was considered the "gold standard" reference. In 36 patients, 81 segments from 12 left anterior descending, 12 circumflex, and 12 right coronary arteries were evaluated. Three-dimensional coronary angiography was always feasible. Although reference vessel diameter was not different between 3D-CA and QCA (p >0.05), segment length measurements were on average 2.3 +/- 2.5 mm longer with 3D-CA than with QCA (p <0.001) and 0.4 +/- 1.8 mm longer than with marker guidewire measurement (p = 0.047). Marker guidewire measurements were 1.9 +/- 2.8 mm longer than QCA measurements (p <0.001). According to Bland-Altman plots, 3D-CA and marker guidewire measurements had the best agreement. In conclusion, 3-dimensional coronary modeling is highly feasible and yields more accurate assessments of the lengths of coronary segments than standard QCA.

"Virtual" in-vivo bench test for bifurcation stenting with "StentBoost"

"StentBoost" is a new angiographic technique that allows improved angiographic visualization of stents deployed in coronary arteries, by enhancing the X-ray focus of the region where the stent is placed. Using this technique we were able to assess the deformation and the expansion of a stent deployed to treat a bifurcation lesion between the mid-left anterior descending (LAD) artery and a big second diagonal branch, during sequential inflations of: (1) the stent per se in the LAD, (2) the ostium of the diagonal branch through the stent struts, (3) the stent again with a non compliant balloon, and (4) both branches with the kissing balloon technique. "StentBoost" guided our clinical and angiographic decision-making process and allowed us to create a "virtual" bench test of the stent deployed at the level of the bifurcation treated.

Mitochondrial uncoupling protein 2 mediates temperature heterogeneity in atherosclerotic plaques

AIMS

Rupture-prone atherosclerotic plaques show an elevated temperature, but a molecular explanation for this phenomenon is unknown. Here, we investigated whether mitochondrial uncoupling protein 2 (UCP2) could be involved because this protein is a macrophage homologue of thermogenin in brown fat tissue.

METHODS AND RESULTS

Immunohistochemistry, western blotting, and real-time quantitative polymerase chain reaction were used to detect UCP2 expression in human and rabbit atherosclerotic plaques. Temperature was measured in plaques with thermography catheters and in cultured cells with precision thermometers. UCP2 was abundantly expressed in subendothelial macrophages of atherosclerotic plaques but not in deeper layers of the plaque. Ex vivo temperature measurements in atherosclerotic rabbit thoracic aorta demonstrated a correlation between local plaque temperature, total macrophage mass, and UCP2 expression. In vitro, chemical uncoupling of macrophages with sodium cyanide resulted in heat production (DeltaT = 0.13 +/- 0.04 degrees C vs. controls). Also, overexpression of UCP2 in cultured cells led to a similar increase in temperature.

CONCLUSION

Our findings provide evidence that temperature heterogeneity in atherosclerotic plaques is at least in part attributed to UCP2 expression in macrophages. The heat generated might be used to detect unstable, macrophage-rich, atherosclerotic plaques via thermography.

Acute and mid-term local vascular effects of compliant balloon inflation (GuardWire system) on saphenous vein bypass grafts: An angiographic analysis

BACKGROUND

The GuardWire distal protection device reduces the incidence of periprocedural complications during percutaneous stenting of diseased saphenous vein grafts. Its mechanism of action is based on the occlusion of the vessel distal to the lesion with an inflated compliant balloon before the intervention, and the aspiration of embolized material after stent implantation. Although no safety issues related to the compliant balloon have been reported in vein graft treatment, concerns related to the potential injury of the balloon on the vessel wall have been raised. We thus evaluated the angiographic outcome of the vein graft segment where the compliant balloon of the GuardWire distal protection device was inflated during percutaneous interventions of diseased vein grafts.

METHODS

Forty consecutive patients undergoing vein graft stenting, all with successful delivery of the GuardWire system, were enrolled. All patients underwent 6-months follow-up angiography. Quantitative coronary angiographic analysis of the vein graft segment where the balloon was inflated was performed before and after the procedure, as well as at 6-month follow-up.

RESULTS

No differences in reference vessel diameter, minimal luminal diameter and diameter stenosis were evident between the three measurements. In particular, the difference between post-procedural and follow-up minimal luminal diameter (namely late loss) was 0.003+/-0.19 mm (95% confidence interval: -0.06-0.06).

CONCLUSIONS

This prospective study supports for the first time the "angiographic safety" of low pressure inflations of a compliant balloon in saphenous vein grafts, suggesting the absence of acute and mid-term effects on the vein graft vessel wall.

Intravascular ultrasound comparison of sirolimus-eluting stent versus bare metal stent implantation in diseased saphenous vein grafts (from the RRISC [Reduction of Restenosis In Saphenous Vein Grafts With Cypher Sirolimus-Eluting Stent] trial)

The randomized Reduction of Restenosis In Saphenous Vein Grafts with Cypher Sirolimus-Eluting Stent trial compared angiographic outcomes of sirolimus-eluting stents (SESs) versus bare metal stents (BMSs) in saphenous vein grafts (SVG). Using intravascular ultrasound (IVUS) performed during 6-month follow-up angiography, we compared the vascular effects of the 2 types of stent on SVGs. Of 75 patients (96 lesions) included, 59 patients underwent IVUS in 61 SVGs; 29 patients received 40 SESs for 34 lesions, and 30 patients received 42 BMSs for 39 lesions. IVUS parameters (diameters, areas, and volumes) were compared in the 2 groups. A specific analysis was performed for overlapping SESs. Median neointimal volume was 1.3 mm(3) (interquartile range 0 to 13.1) in SESs versus 24.5 (7.8 to 39.5) in BMSs (p <0.001). Minimal incomplete stent apposition was detected at only 3 stent edges (2 BMSs, 1 SES) next to ectatic regions of the SVG. Compared with single SESs, overlapping SESs showed significant increases in neointimal reaction, with a neointimal volume of 0.6 mm(3)/mm of stent (0.1 to 1.8) versus 0 (0 to 0.4) in single SESs (p = 0.03), and this phenomenon was mainly localized in overlapping SES segments, where neointimal volume per millimeter of stent was 1.1 mm(3)/mm (0.6 to 4.4) versus 0 (0 to 1.3) in nonoverlapping segments (p = 0.05). In conclusion, SESs effectively inhibit neointimal hyperplasia volume compared with BMSs in diseased vein grafts, without evidence of increased incomplete apposition risk. The neointimal response to overlapping SES layers seems higher than to a single SES layer.

Increased Late Mortality After Sirolimus-Eluting Stents Versus Bare-Metal Stents in Diseased Saphenous Vein Grafts

OBJECTIVES

We sought to provide long-term follow-up data of sirolimus-eluting stents (SES) versus bare-metal stents (BMS) in saphenous vein grafts (SVG) from the RRISC (Reduction of Restenosis In Saphenous vein grafts with Cypher) trial.

BACKGROUND

We have previously shown that, in SVG, the use of SES reduces 6-month restenosis and repeated revascularization procedures versus the use of BMS. These data are consistent with trials in native coronary arteries. However, recently published long-term follow-up data of these trials have revealed an increased risk of adverse events (particularly very late stent thrombosis) after SES.

METHODS

A total of 75 patients with 96 SVG lesions were randomized to SES versus BMS. All patients underwent clinical follow-up up to 3 years. Specific outcomes assessed in this secondary post-hoc analysis were all-cause mortality, myocardial infarction, and target vessel revascularization.

RESULTS

Thirty-eight patients received 60 SES for 47 lesions, whereas 37 patients received 54 BMS for 49 lesions. At a median follow-up time of 32 months (interquartile range 26.5 to 36 months), 11 deaths (7 cardiac, of which 1 was caused by very late stent thrombosis and, 3 were sudden) occurred after SES (29% [95% confidence interval (CI) 17% to 45%]) versus 0 after BMS (0% [95% CI 0% to 9%]) with an absolute difference of 29% ([95% CI 14% to 45%], p < 0.001). The rates of myocardial infarction and target vessel revascularization were not different: 18% and 34% after SES, respectively, versus 5% and 38% after BMS, respectively (p = 0.15 and p = 0.74, respectively).

CONCLUSIONS

In this secondary post-hoc analysis, BMS were associated with lower long-term mortality than SES for SVG disease. Also, the 6-month reduction in repeated revascularization procedures with SES was lost at longer-term follow-up. (RRISC Study: Reduction of Restenosis In Saphenous Vein Grafts With Cypher Sirolimus-Eluting Stent; http://clinicaltrials.gov/ct/show/NCT00263263?order=1; NCT00263263).

Randomized Double-Blind Comparison of Sirolimus-Eluting Stent Versus Bare-Metal Stent Implantation in Diseased Saphenous Vein Grafts

OBJECTIVES

We sought to compare, in a randomized fashion, sirolimus-eluting stents (SES) versus bare-metal stents (BMS) in saphenous vein grafts (SVGs).

BACKGROUND

Sirolimus-eluting stents reduce restenosis and repeated revascularization in native coronary arteries compared with BMS. However, randomized data in SVG are absent.

METHODS

Patients with SVG lesions were randomized to SES or BMS. All were scheduled to undergo 6-month coronary angiography. The primary end point was 6-month angiographic in-stent late lumen loss. Secondary end points included binary angiographic restenosis, neointimal volume by intravascular ultrasound and major adverse clinical events (death, myocardial infarction, target lesion, and vessel revascularization).

RESULTS

A total of 75 patients with 96 lesions localized in 80 diseased SVGs were included: 38 patients received 60 SES for 47 lesions, whereas 37 patients received 54 BMS for 49 lesions. In-stent late loss was significantly reduced in SES (0.38 +/- 0.51 mm vs. 0.79 +/- 0.66 mm in BMS, p = 0.001). Binary in-stent and in-segment restenosis were reduced, 11.3% versus 30.6% (relative risk [RR] 0.37; 95% confidence interval [CI] 0.15 to 0.97, p = 0.024) and 13.6% versus 32.6% (RR 0.42; 95% CI 0.18 to 0.97, p = 0.031), respectively. Median neointimal volume was 1 mm(3) (interquartile range 0 to 13) in SES versus 24 (interquartile range 8 to 34) in BMS (p < 0.001). Target lesion and vessel revascularization rates were significantly reduced, 5.3% versus 21.6% (RR 0.24; 95% CI 0.05 to 1.0, p = 0.047) and 5.3% versus 27% (RR 0.19; 95% CI 0.05 to 0.83, p = 0.012), respectively. Death and myocardial infarction rates were not different.

CONCLUSIONS

Sirolimus-eluting stents significantly reduce late loss in SVG as opposed to BMS. This is associated with a reduction in restenosis rate and repeated target lesion and vessel revascularization procedures. (The RRISC Study; http://clinicaltrials.gov/ct/show; NCT00263263).

Macroscopic assessment of porcine coronary vessel wall trauma after percutaneous cardiac catheterization and intervention

A macroscopic pathological assessment of the coronary arteries of a pig's heart, in which stent implantation and intra-vascular ultrasound and thermography pullbacks were performed, shows that during percutaneous coronary catheterization and intervention, one of the major vessel traumas occurs in the very proximal part of the coronary arteries, where the guiding catheter tip is manipulated to adequately engage the vessels.

Dissimilar relevance given to diseases by medical literature, and the potential to create biases in the clinical decision-making process: the case of late stent thrombosis

We discuss two cases of non-occlusive sub-acute/late stent thrombosis, one correctly diagnosed (with the help of intravascular ultrasound) 12 days after implantation of a sirolimus eluting stent, the other erroneously non recognized 17 days after implantation of a bare metal stent and evolving 6 weeks later in total thrombotic occlusion of the stent itself. We believe that our clinical judgment, accurate in case of sirolimus eluting stent thrombosis, but wrong in case of bare metal stent thrombosis, was largely influenced by the recent literature giving overwhelming attention, in the drug-eluting stent era, to an issue (late stent thrombosis) that was already present but under-considered, also in the bare metal stent era.

Facilitated recognition of an undeployed stent with StentBoost

Underdeployment of stents is a major cause of restenosis. Standard cinegraphic visualisation has its shortcomings. We present a case in which we used a new technique, called StentBoost. This new technique enabled us to diagnose an undeployed stent as cause of a proximal restenosis problem, with direct major therapeutic consequences.

Comparison of the CardioShield filter with the guardwire balloon in the prevention of embolisation during vein graft intervention: results from the CAPTIVE randomised trial

AIMS

This study assessed safety and efficacy of a third-generation distal protection device, MedNova CardioShield Bare Wire Myocardial Protection System, for treating Saphenous Vein Graft (SVG) disease.Treatment of SVG disease remains difficult, with increased adverse cardiac events (MACE) primarily manifested as no reflow and periprocedural infarction. Even with approved embolic protection devices, 30-day MACE rates are approximately 10%.

METHODS AND RESULTS

A multicentre randomized clinical trial evaluated a third-generation distal protection device MedNova CardioShield vs Percusurge GuardWire in 652 patients undergoing treatment of SVG disease, using a primary endpoint of 30-day death, Q-wave, non-Q-wave infarction, or target vessel revascularisation (MACE).The primary endpoint occurred in 11.4% with CardioShield vs 9.1% with GuardWire (P=.37). Intention-to-treat analysis showed a strong trend for noninferiority (P=.057). Secondary modified intention-to-treat analysis including only patients receiving treatment device and no protocol deviation (defined as treatment of another lesion not using embolic protection) supported noninferiority of CardioShield (P=.022).

CONCLUSION

Analysis of outcomes of treatment strategies for SVG disease is difficult. In this trial, final results depended on whether a patient actually received the device according to protocol. With 30-day MACE as primary endpoint, CardioShield was not demonstrated to be noninferior to GuardWire.

Traumatic ostial stenosis of internal mammary coronary graft

Because of the extensive use of arterial conduits for coronary surgery there is a growing interest in percutaneous intervention in these conduits. This kind of intervention presents a challenge for the interventional cardiologist owing to the anatomic and functional characteristics of this graft. In most cases significant internal mammary artery disease occurs at the distal anastomosis. Ostial stenoses are rare and their pathology uncertain. The authors report a case of an ostial graft lesion, most probably caused by repetitive ostial engagement of the left internal mammary artery in combination with atherosclerosis in the subclavian artery affecting the internal mammary artery.

Intravascular thermography: Immediate functional and morphological vascular findings

AIMS

To investigate safety, feasibility, and injurious effect on endothelial cells of a thermography catheter as well as effect of flow on measured temperature in non-obstructive arteries.

METHODS AND RESULTS

Safety and feasibility were tested in both rabbit aortas and pig coronary arteries. Evaluation of endothelial damage by the catheter (acute, 7 and 14 days) was performed in pig coronaries using Evans Blue, scanning electron microscopy (SEM) and Factor-VIII antibody and compared with normal arteries and arteries that underwent intravascular ultrasound (IVUS). The effect of flow on temperature heterogeneity was analysed both in vitro and in vivo conditions. All procedures were successful without any adverse events; intra- and inter-operator variability was low. Intracoronary use of the catheter was associated with acute but reversible de-endothelialization, paralleling the findings associated with IVUS use. Changes in flow velocities under physiologic flow conditions did not significantly influence the temperature differences measured both in vitro and in vivo; temperature heterogeneity was more pronounced in absence of flow.

CONCLUSIONS

Intracoronary thermography using a dedicated catheter is safe and feasible with a similar degree of de-endothelialization as IVUS. Temperature heterogeneity remained unchanged under normal physiologic flow conditions allowing clinical use of thermography.

Imaging of atherosclerosis. Intravascular imaging of the vulnerable atherosclerotic plaque: spotlight on temperature measurement

The vulnerable atherosclerotic plaque is associated with an increased number of acute coronary syndromes. Current techniques such as coronary angiography are unable to detect and prospectively evaluate these lesions. Recently, other techniques, both invasive and noninvasive, are being developed trying to detect the plaque that is at increased risk for rupture eventually resulting in increased thrombosis. This review describes briefly evolving techniques for imaging of vulnerable plaques and describes in detail intravascular thermography.

In vivo temperature heterogeneity of atherosclerotic plaques is determined by plaque composition

BACKGROUND

Temperature heterogeneity of atherosclerotic plaques has been associated with macrophage accumulation in ex vivo studies. We investigated in vivo whether modifying the cell composition of rabbit atherosclerotic plaques by dietary cholesterol lowering can influence temperature heterogeneity.

METHODS AND RESULTS

Twenty New Zealand rabbits were randomized to either a normal (n=10) or cholesterol-rich (0.3%) diet (n=10) for 6 months. Thereafter, intravascular ultrasound and intravascular catheter-based thermography of the surface of aortic arch and descending aorta were performed in all animals. Ten control and 5 hypercholesterolemic rabbits were euthanized, and their aortas were analyzed histologically. The 5 remaining rabbits received a normal diet for 3 months and underwent repeat ultrasound and thermography before euthanasia followed by histology. Ex vivo temperature was measured in 3 additional rabbits at 6 months to correlate local temperature with local plaque composition. In control animals, plaque formation and temperature heterogeneity were absent. In hypercholesterolemic rabbits, plaque formation was prominent in the thoracic aorta. Plaques were composed of fibromuscular tissue and contained, underneath endothelial cells, an accumulation of foam cells of macrophage origin. Temperature heterogeneity was markedly elevated and increased with plaque thickness. Importantly, after 3 months of cholesterol lowering, plaque thickness remained unchanged, but temperature heterogeneity was significantly decreased. This paralleled plaque histology, which showed a marked loss of macrophages. The ex vivo experiments demonstrated the relation between local temperature and local total macrophage mass.

CONCLUSIONS

In vivo temperature heterogeneity of rabbit atherosclerotic plaques is determined by plaque composition. In vivo thermography may have important clinical implications in the assessment of plaque composition.