Adenosine in Acute Myocardial Infarction-Associated Reperfusion Injury: Does it Still Have a Role?

The mainstay of acute myocardial infarction has long been timely reperfusion of the culprit obstruction. Reperfusion injury resulting from a multitude of pathophysiological processes has been demonstrated to negatively affect myocardial recovery and function post-infarction. Adenosine interacts directly with the sequential pathophysiological processes culminating in reperfusion injury by inhibiting them upstream. The evidence for adenosine's benefit in acute myocardial infarction has produced mixed results with regards to myocardial salvage and long-term mortality. The heterogenous evidence with regards to benefits on clinical outcomes has resulted in modest uptake of adenosine in the clinical setting. However, it is critical to analyze the variability in study methodologies. The goal of this review is to evaluate how adenosine dose, route of administration, timing of administration, and site of administration play essential roles in the molecule's efficacy. The benefits of adenosine, as highlighted in the following review, are clear and its role in the treatment of acute myocardial infarction should not be discounted.

Inaccuracy of brachial blood pressure and its potential impact on treatment and aortic blood pressure estimation.

OBJECTIVE: Although brachial cuff SBP is universally used to guide hypertension management, it can differ significantly from intraarterial SBP. We examine the potential impacts of cuff-to-intraarterial brachial SBP (bSBP) mismatch on hypertension treatment and accuracy towards central SBP. METHODS: In 303 individuals, cuff bSBP (CUFF-bSBP) and central SBP were measured using a Mobil-o-Graph simultaneously to intraarterial bSBP (IA-bSBP) and aortic SBP. According to the difference between CUFF-bSBP and IA-bSBP, we identified three phenotypes: Underestimation (CUFF-bSBP < IA-bSBP by >10 mmHg); No Mismatch (CUFF-bSBP within 10 mmHg of IA-bSBP); Overestimation (CUFF-bSBP > IA-bSBP by >10 mmHg) phenotypes. Risk of overtreatment and undertreatment, and accuracy (ARTERY society criteria: mean difference ≤5 ±â€Š8 mmHg) were determined. A multiple linear regression model was used to assess variables associated with the bSBP difference. RESULTS: Underestimation (n = 142), No Mismatch (n = 136) and Overestimation (n = 25) phenotypes had relatively similar characteristics and CUFF-bSBP (124 ±â€Š17, 122 ±â€Š14, 127 ±â€Š19 mmHg, P = 0.19) but different aortic SBP (133 ±â€Š21, 120 ±â€Š16, 112 ±â€Š18 mmHg, P < 0.001). In the underestimation phenotype, 59% were at risk of undertreatment (14% in No Mismatch), whereas 50% in the Overestimation phenotype were at risk of overtreatment (17% in No Mismatch). CUFF-bSBP accurately estimated aortic SBP only in the No Mismatch Group (mean difference 1.6 ±â€Š8.2 mmHg) whereas central BP never met the accuracy criteria. Male sex, higher height and active smoking were associated with lesser underestimation of bSBP difference. CONCLUSION: The brachial cuff lacks accuracy towards intraarterial BP in a significant proportion of patients, potentially leading to increased risks of BP mismanagement and inaccurate determination of central BP. This illustrates the need to improve the accuracy of cuff-based BP monitors.

Ultrasound guidance versus anatomical landmark approach for femoral artery access in coronary angiography: A randomized controlled trial and a meta-analysis.

OBJECTIVES: The objective was to assess the effect of ultrasound (US)-guidance compared to the anatomical landmark (AL) approach in patients requiring femoral artery (FA) access for coronary angiography/percutaneous coronary interventions (PCI). BACKGROUND: US-guidance has been proposed as a strategy to optimize FA access, potentially leading to decreased vascular complications. METHODS: Patients requiring FA access for coronary angiography/PCI were randomized to the US-guided or AL approaches. The primary endpoint was a composite of immediate procedural vascular outcomes, and access-site outcomes at day one. Results were subsequently pooled in a study-level meta-analysis of randomized trials comparing US-guided FA access to another strategy. RESULTS: A total of 129 patients were randomized (64 US-guided group; 65 AL group). The primary endpoint occurred in 30 patients (47%) with US, and in 39 patients (62%) with AL (P = 0.09). Four additional studies met the inclusion criteria and were included in the meta-analysis (1553 patients). Following data pooling, bleeding events (OR = 0.41; 95%CI 0.20-0.83; P = 0.01), venipunctures (OR = 0.18; 95%CI: 0.11-0.29; P < 0.0001), and multiple puncture attempts (OR = 0.24; 95%CI: 0.19-0.31; P < 0.0001) were significantly improved with US-guidance, but not successful common FA cannulation (OR = 0.84; 95%CI: 0.60-1.17; P = 0.29). CONCLUSION: Our study did not show significant benefits for the use of US to guide arterial femoral access compared to the anatomical landmark approach, but pooled analysis of five randomized trials showed decreased rates of bleeding events and venipunctures, and improved first-pass success. The clinical impact of these findings is uncertain, and do not warrant a systematic use of US-guidance in this clinical setting.

Porcine model of intracoronary pulverization of stent struts by rotablation atherectomy.

OBJECTIVE: To evaluate the feasibility and safety of rotablation atherectomy in a suboptimally expanded stent. METHODS: Seven pigs underwent suboptimal stent expansion in the left anterior descending coronary. Pulverization of the stent struts was performed by rotablation atherectomy with two different burr sizes. Two types of control porcine models were used: pigs with fully expanded stents and pigs without stents. Continuous electrocardiogram readings as well as microscopic and radiologic analysis of cardiac tissue were performed. RESULTS: Rotablation atherectomy reduces the suboptimally expanded stent by (26.95 ± 5.03)%. Ninety-five percent of the metal microparticles, imbedded in the suboptimally expanded stent group cardiac tissue, are less than 15 µm. Transient vasospasm and ST segments elevations were observed during rotablation atherectomy, which returned to basal conditions at the end of the intervention. CONCLUSION: Our study demonstrated the feasibility and safety of using rotablation atherectomy to pulverize stent struts in a suboptimally expanded stent.

The role of oxidized phospholipids, lipoprotein (a) and biomarkers of oxidized lipoproteins in chronically occluded coronary arteries in sudden cardiac death and following successful percutaneous revascularization.

AIMS: OxPL are pro-inflammatory and may mediate atherogenesis, thrombosis and endothelial dysfunction. We studied the histological presence and temporal increases in oxidized phospholipids on apolipoprotein B-100 particles (OxPL/apoB), lipoprotein (a) [Lp(a)] and biomarkers of oxidized lipoproteins in subjects with chronic total coronary occlusions (CTO) with sudden cardiac death (SCD) and following percutaneous coronary intervention (PCI). METHODS: Eight subjects with SCD and CTO and 33 patients with successful PCI of CTO were included. Blood samples were drawn before PCI, immediately post-PCI, at 6 and 24 h, at 3 days and at 1 week. Plasma levels of OxPL/apoB, Lp(a), IgG and IgM autoantibodies to malondialdehyde (MDA) low-density lipoprotein and apoB-immune complexes were measured in all samples and compared with previous data from 141 patients undergoing PCI of non-CTO vessels. RESULTS: Immunohistochemistry of coronary CTOs revealed OxPL and MDA-like epitopes, particularly in areas of recanalized and organized thrombus and neovascularization. Following PCI, OxPL/apoB and Lp(a) levels, expressed as percent change from baseline levels before PCI, rose gradually and progressively over the next 7 days. In contrast, levels of OxPL/apoB and Lp(a) in non-CTO vessels rose immediately post PCI and then dropped rapidly to baseline within 24 h. CONCLUSIONS: CTOs contain immunohistological evidence of OxPL and MDA-like epitopes. Successful PCI of CTOs results in a slower increase in OxPL/apoB and Lp(a) but higher increase in IgM immune complexes compared to non-CTO vessels. Pro-inflammatory oxidation-specific epitopes may impact development of CTOs and affect outcomes following PCI that can be evaluated in larger clinical trials.

Effects of distal embolization on the timing of platelet and inflammatory cell activation in interventional coronary no-reflow.

INTRODUCTION: Myocardial hypoperfusion following percutaneous coronary intervention, termed "no-reflow", may be initiated by distal coronary embolization. This study examined the effects of distal embolization on the extent and timing of inflammation and platelet activation in an experimental model of coronary no-reflow. MATERIAL AND METHODS: A no-reflow model was established in 9 Yorkshire pigs by injecting incremental doses of biologically inert polystyrene microspheres into the left anterior descending artery every 20 minutes via a transit catheter. A control group included 3 pigs that received corresponding intra-coronary boluses of normal saline. At predefined time points, coronary sinus blood samples were drawn and immediately analyzed by flow cytometry analysis for a panel of white blood cell and platelet activation markers, and the inflammatory cytokine TNFalpha. RESULTS: No-reflow was achieved after delivery of 1,169,000+/-303,000 (range: 680,000 to 2,600,000) microspheres. In the distal embolization group, there were significant increases above baseline values in polymorphonuclear-platelet aggregates (146%-218%), in monocyte-platelet aggregates (51%-94%) and in TNFalpha levels (54%-84%) at multiple time points prior to no- reflow (15% cumulative dose and higher). For Annexin A5, there was a significant increase at 52% of cumulative dose (177% above baseline). Controls only showed one significant increase above baseline value for polymorphonuclear-platelet aggregates at the time of the last injection. CONCLUSIONS: Widespread activation of interacting inflammatory and coagulation pathways following microsphere embolization occurred prior to the onset of angiographic no-reflow. This activation pattern cannot be attributed to prolonged coronary sinus instrumentation. Interactions between white blood cells (polymorphonuclears and monocytes) and platelets likely play an important role in the pathogenesis of no-reflow following distal embolization and may represent important therapeutic targets.

Comparison of electrocardiographic recordings in open-chest and closed-chest swine models.

The aim of our study was to compare the electrocardiographic recordings in an experimental open-chest swine model before and after left-sided thoracotomy to detect any surgery-induced fluctuations that might interfere with subsequent experimental interventions. We obtained electrocardiograms from 8 deeply anesthetized domestic swine and compared the respective ST-segment potentials obtained after vascular surgery and after left-sided thoracotomy and dissection of the left anterior descending coronary artery. Compared with baseline recordings, no significant ST-segment deviation on any of the electrocardiographic leads occurred after vascular surgery. However, statistically significant ST-segment depression was observed after thoracotomy. Invasive surgical procedures in open-chest swine models may lead to morphologic changes in the ST segment. The physiologic mechanism of these changes is not fully understood.

Comparison of radial versus femoral approach for percutaneous coronary interventions in octogenarians.

BACKGROUND: The safety and efficacy of a radial approach for percutaneous coronary intervention (PCI) in octogenarians is not well established. METHODS: To evaluate the benefits of a radial approach for preventing vascular complications after PCI, clinical, procedural, and outcome data were prospectively collected and compared for 228 octogenarians undergoing elective PCI either through a radial or a femoral approach. RESULTS: Radial approach was associated with longer cannulation (3.1 +/- 2.9 vs. 2.0 +/- 2.0 min, P < 0.001) and fluoroscopy times (19.3 +/- 16.1 vs. 16.1 +/- 11.8 min, P = 0.04), greater utilization of contrast media (224 +/- 46 vs. 182 +/- 20 ml, P < 0.001) and higher crossover rate (11 vs 4%, P = 0.03) to alternate access site compared with the femoral approach. However, ambulation time (5.2 +/- 3.1 vs. 11.6 +/- 6.3 hr, P < 0.001), access site bleeding (4 vs. 14%, P = 0.007), hematoma (1 vs. 11%, P = 0.001) or any vascular complication (5 vs 26%, P = 0.001) were significantly reduced with a radial approach. Procedural success rates were equivalent with both approaches. Multivariate regression analysis identified radial approach (OR = 0.23; CI = 0.08, 0.65) as an independent negative predictor of postprocedural vascular complications. CONCLUSION: Radial approach for PCI in octogenarians is technically challenging for the operator and exposes patients to greater volume of nephrotoxic contrast media. However, it results in early ambulation and significantly reduces vascular complications in this high risk population. These findings support a strategy of preprocedural risk assessment and use of radial approach for PCI in a select group of octogenarians to maximize benefits offered by this technique.

The cell cycle: a critical therapeutic target to prevent vascular proliferative disease.

Percutaneous coronary intervention is the preferred revascularization approach for most patients with coronary artery disease. However, this strategy is limited by renarrowing of the vessel by neointimal hyperplasia within the stent lumen (in-stent restenosis). Vascular smooth muscle cell proliferation is a major component in this healing process. This process is mediated by multiple cytokines and growth factors, which share a common pathway in inducing cell proliferation: the cell cycle. The cell cycle is highly regulated by numerous mechanisms ensuring orderly and coordinated cell division. The present review discusses current concepts related to regulation of the cell cycle and new therapeutic options that target aspects of the cell cycle.

Human-grade purified collagenase for the treatment of experimental arterial chronic total occlusion.

PURPOSE: Chronic total occlusions (CTO) remain a major limitation of percutaneous interventions. Procedural failure is usually due to the inability to cross the lesion with a guide wire. We have previously shown that local administration of a laboratory-grade collagenase followed by a 72-h waiting period may facilitate guide-wire crossing. The aim of the present study was to evaluate the efficacy and toxicity of a human-grade purified collagenase, suitable for clinical use, in facilitating guide-wire crossing in a rabbit model of femoral artery CTO. METHODS AND RESULTS: A chronic total arterial occlusion was constructed in femoral arteries of New Zealand white rabbits. The local administration of purified collagenase solution (150 microg) via an over-the-wire balloon system was performed in 10 CTO. Guide-wire crossing was attempted after 24 h and was successful in all cases. Different doses (50-500 microg) were administered to an additional 17 rabbits to assess collagenase effects. Local subcutaneous bruising was observed at higher doses. Histological evaluation showed no damage to the arterial wall structure. Arterial extracts from collagenase-treated arteries showed increased MMP-2 and MMP-9 activities and higher levels of local MMP-1 and degraded collagen. CONCLUSIONS: Local administration of a human-grade purified collagenase degrades collagen in CTO and is highly effective for the facilitation of guide-wire crossing in CTO.

Intravenous phosphate in the intensive care unit: more aggressive repletion regimens for moderate and severe hypophosphatemia.

OBJECTIVE: To evaluate efficacy and safety of aggressive correction of hypophosphatemia with intravenous potassium phosphate in the ICU. DESIGN AND SETTING: Randomized interventional prospective study in the medical and surgical ICU of a tertiary university hospital. PATIENTS: Critically ill patients with hypophosphatemia between June and November 1998. MEASUREMENTS AND RESULTS: Patients with moderate hypophosphatemia (<0.65 and >0.40 mmol/l; n=37) were randomized into two groups: group 1 received 30 mmol potassium phosphate intravenously in 50 ml saline over 2 h, and group 2 received 30 mmol potassium phosphate in 100 ml saline over 4 h. Patients with severe hypophosphatemia (<0.40 mmol/l; n=10) were also randomized into two groups: group 3 received 45 mmol potassium phosphate intravenously in 100 ml saline over 3 h, and group 4 received 45 mmol potassium phosphate in 100 ml saline over 6 h. Electrolytes, blood gas, renal function were monitored until day 3; urine was collected during and until 6 h after infusions. The overall efficacy of the protocols was 98% by the end of the infusion. There was no statistical difference in phosphate values between groups at the end of infusion or at 24 h. No adverse events were noted; one patient had an increase in serum potassium to 6.1 mmol/l. Phosphaturia in all groups was elevated as evidenced by fractional excretion above 20%. CONCLUSIONS: More rapid administration of large potassium phosphate boluses is effective and safe for correcting hypophosphatemia in ICU patients with preserved renal function if baseline serum potassium is below 4 mmol/l.