Coronary Guidewires in Temporary Cardiac Pacing and Assessment of Myocardial Viability: Current Perspectives and Future Directions

Intracoronary guidewires used in percutaneous coronary intervention can also be configured to provide temporary ventricular pacing. Trans coronary electrophysiological parameters recorded by employing coronary guidewires may have a potential role in assessing myocardial viability and could provide a means to make an immediate on-table decision about revascularisation. To date, some small studies have demonstrated the safety of this technique in temporary cardiac pacing, but further research is required to refine this approach and establish its clinical utility in myocardial viability assessment. In this review we discuss the potential role of trans coronary electrophysiology in the assessment of myocardial viability.

Current Management of Highly Calcified Coronary Lesions: An Overview of the Current Status

The amount of coronary calcium strongly correlates with the degree of atherosclerosis and, therefore, with the rate of future cardiac events. Calcified coronary lesions still represent a challenge for interventional cardiologists, bringing not only a higher risk of immediate complications during percutaneous coronary interventions (PCI), but also a higher risk of late stent failure due to under-expansion and/or malapposition, and therefore, have a relevant prognostic impact. Accurate identification of the calcified plaques together with the analysis of their distribution pattern within the vessel wall by intracoronary imaging is important to improve the successful treatment of these lesions. The aim of this review is to guide readers through the assessment of the calcified plaque distribution using intracoronary imaging in order to select the best devices and strategies for plaque debulking and lesion preparation.

Safety and efficacy of intracoronary thrombolytic agents during primary percutaneous coronary intervention for STEMI

INTRODUCTION

Large thrombus burden in patients with ST elevation myocardial infarction (STEMI) is associated with higher rates of distal embolization, no-reflow phenomenon, abrupt closure, stent thrombosis, major adverse cardiovascular events (MACE), and mortality. Intracoronary (IC) thrombolytic agents are theoretically attractive as an adjunct to primary percutaneous coronary intervention (PPCI) as they activate endogenous fibrinolysis which results in degradation of the cross-linked fibrin matrix in coronary thrombus.

AREAS COVERED

We reviewed published studies reporting on intraprocedural anti-thrombus strategies used during PPCI including randomized controlled trials and observational studies.

EXPERT OPINION

Published studies are limited by small sample size and heterogeneity due to variation in indication, inclusion criteria, thrombolytic agent, dose, delivery mechanisms, antiplatelet and anticoagulant regimen, timing in regard to reperfusion, PCI techniques, and endpoints. Despite these limitations, data are consistent that IC administration of thrombolytic agents at low doses is associated with low rates of bleeding and vascular complications. While there is currently no compelling data demonstrating a benefit to the routine use of IC thrombolytic therapy in patients with STEMI, there is suggestive data that IC thrombolysis may have benefit in selected patients.

Has low-dose intracoronary thrombolysis gained ground in primary percutaneous intervention?

Reducing thrombus burden would improve patient's outcomes. Low-dose intracoronary thrombolytic agent administration has been considered to improve myocardial microcirculation, cardiac function, and major adverse cardiovascular events in patients presenting with ST-segment elevation myocardial infarction and high thrombus burden. This paper discusses published meta-analyses on intracoronary thrombolysis in primary percutaneous intervention.

All Roads Lead to Rome (the Heart): Cell Retention and Outcomes From Various Delivery Routes of Cell Therapy Products to the Heart

In the past decades, numerous preclinical studies and several clinical trials have evidenced the feasibility of cell transplantation in treating heart diseases. Over the years, different delivery routes of cell therapy have emerged and broadened the width of the field. However, a common hurdle is shared by all current delivery routes: low cell retention. A myriad of studies confirm that cell retention plays a crucial role in the success of cell-mediated cardiac repair. It is important for any delivery route to maintain donor cells in the recipient heart for enough time to not only proliferate by themselves, but also to send paracrine signals to surrounding damaged heart cells and repair them. In this review, we first undertake an in-depth study of primary theories of cell loss, including low efficiency in cell injection, "washout" effects, and cell death, and then organize the literature from the past decade that focuses on cell transplantation to the heart using various cell delivery routes, including intracoronary injection, systemic intravenous injection, retrograde coronary venous injection, and intramyocardial injection. In addition to a recapitulation of these approaches, we also clearly evaluate their strengths and weaknesses. Furthermore, we conduct comparative research on the cell retention rate and functional outcomes of these delivery routes. Finally, we extend our discussion to state-of-the-art bioengineering techniques that enhance cell retention, as well as alternative delivery routes, such as intrapericardial delivery. A combination of these novel strategies and more accurate assessment methods will help to address the hurdle of low cell retention and boost the efficacy of cell transplantation to the heart.

Intracoronary Thrombolysis in Patients With ST-Segment Elevation Myocardial Infarction: A Meta-Analysis of Randomized Controlled Trials

BACKGROUND

The effects of intracoronary (IC) thrombolysis therapy in patients with ST-segment elevation myocardial infarction (STEMI) receiving primary percutaneous coronary intervention (PPCI) remain unclear.

METHODS

The meta-analysis was conducted according to the PRISMA statement. All relevant studies were identified by searching the PubMed, EMBASE, Cochrane Library, and Web of Science, with no time or language limitation. The pooled risk ratio (RR) and weighted mean difference (WMD) with a 95% CI were calculated.

RESULTS

Nine randomized controlled trials involving a total of 1341 patients were included. Compared with the control group, IC thrombolysis in patients with STEMI could reduce the incidence of major adverse cardiac events (MACE; RR 0.632, 95% CI, 0.474-0.843, P = .002) and improve left ventricular ejection fraction (RR 0.343, 95% CI, 0.178-0.509, P < .001) and myocardial microcirculation. However, there was no difference noted in the mortality (RR 0.759, 95% CI, 0.347-1.661, P = .490). The incidence rate of major bleeding and minor bleeding was comparable between the 2 groups.

CONCLUSIONS

Intracoronary thrombolysis was associated with improved MACE and myocardial microcirculation in patients with STEMI having PPCI, though it failed to improve mortality.

Myocardial tissue salvage is correlated with ischemic border region temperature at reperfusion

OBJECTIVES

Our pilot study investigated the association between region-specific myocardial tissue temperature and tissue salvage using a novel tri-lumen cooling catheter to provide rapid localized cooling directly to the heart in an open-chest porcine model of ischemia-reperfusion.

BACKGROUND

Therapeutic hypothermia remains a promising strategy to limit reperfusion injury following myocardial ischemia.

METHODS

Large swine underwent 60 min of coronary occlusion followed by 3 hr of reperfusion. Prior to inducing ischemia, six temperature probes were placed directly on the heart, monitoring myocardial temperatures in different locations. Hemodynamic parameters and core temperature were also collected. Approximately 15 min prior to reperfusion, the cooling catheter was inserted via femoral artery and the distal tip advanced proximal to the occluded coronary vessel under fluoroscopic guidance. Autologous blood was pulled from the animal via femoral sheath and delivered through the central lumen of the cooling catheter, delivering at 50 ml/min, 27°C at the distal tip. Cooling was continued for an additional 25 min after reperfusion followed by a 5-min controlled rewarming. Hearts were excised and assessed for infarct size per area at risk.

RESULTS

Although cooling catheter performance was consistent throughout the study (38 W), the resulting tissue cooling was not. Our results show a correlation between myocardial tissue salvage and ischemic border region (IBR) temperature at the time of reperfusion (R² = 0.59, p = 0.027). IBR tissue is the tissue located at the boundary between healthy and ischemic tissues.

CONCLUSIONS

Our findings suggest that localized, rapid, short-term myocardial tissue cooling has the potential to limit reperfusion injury in humans.

Matrix Metalloproteinase-2 Impairs Homing of Intracoronary Delivered Mesenchymal Stem Cells in a Porcine Reperfused Myocardial Infarction: Comparison With Intramyocardial Cell Delivery

Background

Intracoronary (IC) injection of mesenchymal stem cells (MSCs) results in a prompt decrease of absolute myocardial blood flow (AMF) with late and incomplete recovery of myocardial tissue perfusion. Here, we investigated the effect of decreased AMF on oxidative stress marker matrix metalloproteinase-2 (MMP-2) and its influence on the fate and homing and paracrine character of MSCs after IC or intramyocardial cell delivery in a closed-chest reperfused myocardial infarction (MI) model in pigs.

Methods

Porcine MSCs were transiently transfected with Ad-Luc and Ad-green fluorescent protein (GFP). One week after MI, the GFP-Luc-MSCs were injected either IC (group IC, 11.00 ± 1.07 × 10⁶) or intramyocardially (group IM, 9.88 ± 1.44 × 10⁶). AMF was measured before, immediately after, and 24 h post GFP-Luc-MSC delivery. In vitro bioluminescence signal was used to identify tissue samples containing GFP-Luc-MSCs. Myocardial tissue MMP-2 and CXCR4 receptor expression (index of homing signal) were measured in bioluminescence positive and negative infarcted and border, and non-ischemic myocardial areas 1-day post cell transfer. At 7-day follow-up, myocardial homing (cadherin, CXCR4, and stromal derived factor-1alpha) and angiogenic [fibroblast growth factor 2 (FGF2) and VEGF] were quantified by ELISA of homogenized myocardial tissues from the bioluminescence positive and negative infarcted and border, and non-ischemic myocardium. Biodistribution of the implanted cells was quantified by using Luciferase assay and confirmed by fluorescence immunochemistry. Global left ventricular ejection fraction (LVEF) was measured at baseline and 1-month post cell therapy using magnet resonance image.

Results

AMF decreased immediately after IC cell delivery, while no change in tissue perfusion was found in the IM group (42.6 ± 11.7 vs. 56.9 ± 16.7 ml/min, p = 0.018). IC delivery led to a significant increase in myocardial MMP-2 64 kD expression (448 ± 88 vs. 315 ± 54 intensity × mm², p = 0.021), and decreased expression of CXCR4 (592 ± 50 vs. 714 ± 54 pg/tissue/ml, p = 0.006), with significant exponential decay between MMP-2 and CXCR4 (r = 0.679, p < 0.001). FGF2 and VEGF of the bioluminescence infarcted and border zone of homogenized tissues were significantly elevated in the IM goups as compared to IC group. LVEF increase was significantly higher in IM group (0.8 ± 8.4 vs 5.3 ± 5.2%, p = 0.046) at the 1-month follow up.

Conclusion

Intracoronary stem cell delivery decreased AMF, with consequent increase in myocardial expression of MMP-2 and reduced CXCR4 expression with lower level of myocardial homing and angiogenic factor release as compared to IM cell delivery.

Appropriate bolus administration of glycoprotein IIb/IIIa inhibitors for patients with acute coronary syndromes undergoing percutaneous coronary intervention: intracoronary or intravenous? A comprehensive and updated meta-analysis and systematic review

BACKGROUND AND AIM

This systematic review with meta-analysis sought to compare the efficacy and safety of intracoronary (IC) vs. intravenous (IV) administration of glycoprotein (GP) IIb/IIIa receptor inhibitors on clinical outcomes following per-cutaneous coronary intervention in patients with acute coronary syndromes (ST-segment elevation myocardial infarction or non-ST-segment-elevation acute coronary syndrome).

METHODS

Medline, Embase, Elsevier, and Sciences online databases as well as Google Scholar literature were used to select appropriate studies with randomised controlled design. The primary end-points were mortality and target vessel revascularisation (TVR), whereas the secondary end points were incidence of thrombolysis in myocardial infarction score 3 flow (TIMI 3 flow means complete perfusion in distal coronary artery bed), re-myocardial infarction (re-MI), major bleeding, stent thrombosis left ventricular ejection fraction (LVEF), and heart failure (HF). The literature search of all major databases retrieved 1006 stud-ies. After screening, a total of 18 trials (5812 patients) were identified with reported outcomes.

RESULTS

Pooled analysis showed IC administration of GP IIb/IIIa receptor inhibitors can significantly increase LVEF (WMD 4.97; 95% CI 3.34-6.60; p = 0.000) and the incidence of TIMI 3 flow (OR of 0.77; 95% CI 0.64-0.92; p = 0.005), and significantly decrease in incidence of HF (OR of 1.927; 95% CI 1.189-3.124; p = 0.008). Incidences of TVR, re-MI, major bleeding, stent thrombosis, and mortality showed no significant differences between the IC and IV groups.

CONCLUSIONS

Overall, the most appropriate route of administration of GP IIb/IIIa inhibitors for patients with acute coronary syndromes appeared to be an IC injection that could increase LVEF and TIMI 3 flow and decrease the incidence of HF. Furthermore, the IC administration was not associated with increased adverse event rates when compared to IV injection.

Relationship between myocardial reperfusion, infarct size, and mortality: the INFUSE-AMI (Intracoronary Abciximab and Aspiration Thrombectomy in Patients With Large Anterior Myocardial Infarction) trial

OBJECTIVES

This study sought to compare infarct size (IS) measured by magnetic resonance imaging in patients with successful (myocardial blush grade [MBG] 2/3) versus unsuccessful (MBG 0/1) microcirculatory reperfusion in the INFUSE-AMI (Intracoronary Abciximab and Aspiration Thrombectomy in Patients With Large Anterior Myocardial Infarction) trial.

BACKGROUND

Successful microcirculatory reperfusion, defined angiographically by MBG 2 or 3, is associated with improved outcomes in patients with ST-segment elevation myocardial infarction. The precise mechanism underlying this association is not well defined.

METHODS

The INFUSE-AMI trial randomized 452 patients with anterior ST-segment elevation myocardial infarction to intracoronary bolus abciximab delivered locally at the infarct lesion versus no abciximab, and to manual thrombus aspiration versus no aspiration. The primary endpoint was IS (percentage of left ventricular mass) at 30 days.

RESULTS

MBG 2/3 was achieved in 367 patients (81.4%). IS was significantly lower in patients with MBG 2/3 than in those with MBG 0/1 (median: 16.7% [interquartile range (IQR): 7.0 to 22.7] vs. 19.5% [IQR: 11.1 to 29.2]; p = 0.002). Intracoronary abciximab further reduced IS in patients with MBG 2/3 (median: 14.4% [IQR: 5.4 to 20.9] vs. 17.4% [IQR: 10.5 to 23.8]; p = 0.01). MBG 2/3 was associated with ∼30% reduction in infarct mass (p = 0.002) and ∼90% reduction in microvascular obstruction on day 5. Ejection fraction was higher with MBG 2/3 at 30 days: median: 50.3% (IQR: 43.8 to 57.8) versus 46.9% (IQR: 37.5 to 54.0); p = 0.004. At 30 days, the rate of death was significantly lower (1.7% vs. 8.3%; p = 0.0008) in the MBG 2/3 group.

CONCLUSIONS

MBG 2/3 occurs in 80% of ST-segment elevation myocardial infarction patients treated with primary percutaneous coronary intervention and is associated with smaller infarct size, less microvascular obstruction, improved ejection fraction, and significantly lower 30-day mortality. (Intracoronary Abciximab and Aspiration Thrombectomy in Patients With Large Anterior Myocardial Infarction [INFUSE-AMI]; NCT00976521).

Provocative testing for coronary reactivity and spasm

Coronary spasm is an important and often overlooked etiology of chest pain. Although coronary spasm, or Prinzmetal's angina, has been thought of as benign, contemporary studies have shown serious associated adverse outcomes, including acute coronary syndrome, arrhythmia, and death. Definitive diagnosis of coronary spasm can at times be difficult, given the transience of symptoms. Numerous agents have been historically described for provocative testing. We provide a review of published data for the role of provocation testing in the diagnosis of coronary spasm.

Intracoronary Reopro during Percutaneous Coronary Intervention in Acute and Stable Patient can Influence Stent Thrombosis Formation (IRPASST) Study

BACKGROUND

In patients with acute myocardial infarction or unstable angina undergoing coronary angioplasty, abciximab reduces major adverse cardiac events (MACE). Most clinical trials have studied mainly intravenous administration. Intracoronary (IC) bolus application of abciximab causes very high local drug concentrations and may be more effective in reducing acute and sub-acute stent thrombosis (ST). We studied whether IC bolus administration of abciximab is associated with a reduced ST and target vessels revascularization (TVR); therefore, less MACE rate compared with the standard intravenous IV bolus and infusion application.

MATERIALS AND METHODS

This was a single-center observational study conducted between June 2007 and 2009. We studied a total of 447 patients admitted with either acute coronary intervention (PCI) and stenting. Patients with bleeding disorder, recent major surgery and high blood pressure were excluded. Patients were divided into two groups: Group I (n = 199) patient received IC bolus of abciximab (reopro) 0.25 μg/kg during the PCI in cath lab. Group II (n = 248) received the standard dose of reopro-a bolus intravenous 0.25 μg/kg and maintenance dose of 0.125 μg/kg over 12 h.

RESULTS

There were no differences between the groups with regard to diabetes mellitus, group I (56%) vs. group II (58%), P = 0.613; ACS, group I (38%) vs. group II (44%), P = 0.175; Dietthylstilbestrol Drug eluted stent (DES) in group I (66.5%) vs. (57.6%) group II, P = 0.056; Bare Metal Stent (BMS) in group I (33%) vs. (40.7%) group II, P=0.093; target vessel revascularization (TRV) was seen in 9 patients (4%) in group I vs. 16 patients (6%) in group II. ST elevation was seen in 4 patients (2%) in group I vs. 7 patients (2.8%) in group II, all presented with STEMI.

CONCLUSION

In this study, there was a trend toward less ST and TVR in patients who received IC reopro vs. intravenous route both in ACS and stable CAD. The percentage of DM was high in both groups (56%), especially in Saudi patients. In-stent restenosis (ISR) was less in group I than in group II, this was mainly associated with BMS usage. The percentage of BMS was more than 30% in both groups, either due to STEMI cases or large vessel size. Randomized controlled trials are warranted to further assess IC application of abciximab in reducing ST.

Intravascular optical imaging technology for investigating the coronary artery

There is an ever-increasing demand for new imaging methods that can provide additional information about the coronary wall to better characterize and stratify high-risk plaques, and to guide interventional and pharmacologic management of patients with coronary artery disease. While there are a number of imaging modalities that facilitate the assessment of coronary artery pathology, this review paper focuses on intravascular optical imaging modalities that provide information on the microstructural, compositional, biochemical, biomechanical, and molecular features of coronary lesions and stents. The optical imaging modalities discussed include angioscopy, optical coherence tomography, polarization sensitive-optical coherence tomography, laser speckle imaging, near-infrared spectroscopy, time-resolved laser induced fluorescence spectroscopy, Raman spectroscopy, and near-infrared fluorescence molecular imaging. Given the wealth of information that these techniques can provide, optical imaging modalities are poised to play an increasingly significant role in the evaluation of the coronary artery in the future.

The Optimal Route of Administration of the Glycoprotein IIb/IIIa Receptor Antagonist Abciximab During Percutaneous Coronary Intervention; Intravenous Versus Intracoronary

The use of the glycoprotein (GP) IIb/IIIa receptor antagonist Abciximab has over the years become an important part of the anticoagulant regimen in patients with acute coronary syndrome undergoing percutaneous coronary intervention. Abciximab is a potent inhibitor of platelet aggregation and thrombus formation, but other mechanisms, such as suppression of the inflammatory pathways, have also been proposed to contribute to the benefits of Abciximab.

The optimal route of administration, i.e. intravenous versus intracoronary, of the first dose has been questioned, but only tested in small, non-randomised and retrospective studies or studies with short follow-up. No definite conclusion can be made based on these studies.

In this review we present the current knowledge published about the intracoronary administration of Abciximab including the mechanisms behind the potential beneficial effects, and the safety. The emphasis will be on clinical trials rather than on studies on the pharmacological mechanisms, as the latter have been reviewed thoroughly elsewhere.

Our conclusion from this present review is that randomized trials of intracoronary versus intravenous bolus of Abciximab are needed.

Cell therapy for cardiovascular disease: a comparison of methods of delivery

The field of myocardial regeneration utilizing novel cell-based therapies, gene transfer, and growth factors may prove to play an important role in the future management of ischemic heart disease and cardiomyopathy. Phases I and II clinical trials have been published for a variety of biologics utilizing four methods of delivery: systemic infusion, intracoronary infusion, transvenous coronary sinus, and intramyocardial. This review discusses the advantages and disadvantages of the delivery approaches above.

Intravascular laser speckle imaging catheter for the mechanical evaluation of the arterial wall

Laser speckle imaging (LSI) is a novel technique for measuring the mechanical properties of atherosclerotic plaques. In LSI, the decorrelation time constant of speckle intensity fluctuations provides an index of viscoelasticity that is closely related to plaque microstructure and composition. Here, we demonstrate for the first time, the feasibility of conducting LSI in vivo using a prototype 1.5 mm (4.5 Fr) diameter intravascular catheter. Investigation of the catheter performance using human arterial samples ex vivo shows that plaque time constants measured by the LSI catheter correlate well with those measured using a free-space bulk optics system. To demonstrate LSI in vivo, the catheter is interfaced with a portable console for intravascular evaluation in the aorta of a living rabbit. Distinct differences in arterial time constants are identified at normal aortic and stented sites in vivo with intravascular LSI.

Laser speckle imaging of atherosclerotic plaques through optical fiber bundles

Laser speckle imaging (LSI), a new technique that measures an index of plaque viscoelasticity, has been investigated recently to characterize atherosclerotic plaques. These prior studies demonstrated the diagnostic potential of LSI for detecting high-risk plaques and were conducted ex vivo. To conduct intracoronary LSI in vivo, the laser speckle pattern must be transmitted from the coronary wall to the image detector in the presence of cardiac motion. Small-diameter, flexible optical fiber bundles, similar to those used in coronary angioscopy, may be incorporated into an intravascular catheter for this purpose. A key challenge is that laser speckle is influenced by inter-fiber leakage of light, which may be exacerbated during bundle motion. In this study, we tested the capability of optical fiber bundles to transmit laser speckle patterns obtained from atherosclerotic plaques and evaluated the influence of motion on the diagnostic accuracy of fiber bundle-based LSI. Time-varying helium-neon laser speckle images of aortic plaques were obtained while cyclically moving the flexible length of the bundle to mimic coronary motion. Our results show that leached fiber bundles may reliably transmit laser speckle images in the presence of cardiac motion, providing a viable option to conduct intracoronary LSI.