Liposomal Nanocarriers Designed for Sub-Endothelial Matrix Targeting under Vascular Flow Conditions.

Vascular interventions result in the disruption of the tunica intima and the exposure of sub-endothelial matrix proteins. Nanoparticles designed to bind to these exposed matrices could provide targeted drug delivery systems aimed at inhibiting dysfunctional vascular remodeling and improving intervention outcomes. Here, we present the progress in the development of targeted liposomal nanocarriers designed for preferential collagen IV binding under simulated static vascular flow conditions. PEGylated liposomes (PLPs), previously established as effective delivery systems in vascular cells types, served as non-targeting controls. Collagen-targeting liposomes (CT-PLPs) were formed by conjugating established collagen-binding peptides to modified lipid heads via click chemistry (CTL), and inserting them at varying mol% either at the time of PLP assembly or via micellar transfer. All groups included fluorescently labeled lipid species for imaging and quantification. Liposomes were exposed to collagen IV matrices statically or via hemodynamic flow, and binding was measured via fluorometric analyses. CT-PLPs formed with 5 mol% CTL at the time of assembly demonstrated the highest binding affinity to collagen IV under static conditions, while maintaining a nanoparticle characterization profile of ~50 nm size and a homogeneity polydispersity index (PDI) of ~0.2 favorable for clinical translation. When liposomes were exposed to collagen matrices within a pressurized flow system, empirically defined CT-PLPs demonstrated significant binding at shear stresses mimetic of physiological through pathological conditions in both the venous and arterial architectures. Furthermore, when human saphenous vein explants were perfused with liposomes within a closed bioreactor system, CT-PLPs demonstrated significant ex vivo binding to diseased vascular tissue. Ongoing studies aim to further develop CT-PLPs for controlled targeting in a rodent model of vascular injury. The CT-PLP nanocarriers established here show promise as the framework for a spatially controlled delivery platform for future application in targeted vascular therapeutics.

Factors Determining Left Main Coronary Artery Luminal Area.

BACKGROUND: A certain minimal luminal cross-sectional area has been traditionally used in clinical practice as a cut-off value to determine severity of left main coronary artery (LMCA) stenosis. The severity of stenosis, however, depends on the baseline luminal area (ie, area prior to stenosis), which may vary among individuals. The present study was undertaken to define normal LMCA luminal area using current technology in vivo. METHODS: LMCA luminal area was determined using multislice computed tomography coronary angiography. Eighty-six subjects with normal coronary arteries and calcium score of zero were included in this study. Left ventricular (LV) mass and LV volumes (systolic, diastolic) were also measured. RESULTS: A wide distribution was found in LMCA luminal area, with median value 17.3 mm² and range 8.1-33.9 mm². A relationship was found between log(LMCA luminal area) and log(LV mass) (r=.515; P<.001) and with body surface area (r=.273; P=.01). Significant relationships were also found between LMCA luminal area and LV volumes (systolic, diastolic). In multiple regression analysis, however, the LV mass was the only independent predictor of LMCA luminal area. CONCLUSION: LMCA luminal area varies substantially among individuals with normal coronary arteries and is related to many other factors. The data suggest that the current practice of using a minimal luminal area cut-off when assessing LMCA stenosis may be misleading, and thus available information should be individualized.

Left atrial myxoma causing coronary steal: an atypical cause of angina.

Cardiac myxomas are rare primary cardiac tumors that usually present with dyspnea or manifestations of systemic embolization. Coronary steal is a rare phenomenon of unbalanced blood flow that is seen primarily in patients who have undergone coronary artery bypass grafting and have subclavian artery stenosis. We report the case of a 72-year-old woman who presented with fatigue, weakness, and exertional chest heaviness and had abnormal results on a cardiac stress test. The results of coronary angiography showed no obstructive coronary artery disease but revealed a large intracardiac left atrial mass that was supplied by 2 anomalous coronary arteries. The patient underwent successful ligation of the anomalous coronary arteries and resection of the mass, which was histologically an atrial myxoma. The patient's symptoms resolved, and results of a repeat cardiac stress test were normal. To our knowledge, this is the first report of a highly vascularized atrial myxoma that caused coronary steal with objective evidence of ischemia, and with subsequent resolution after resection of the mass and ligation of the anomalous coronary arteries.

Comparison of Impella and intra-aortic balloon pump in high-risk percutaneous coronary intervention: vascular complications and incidence of bleeding.

OBJECTIVE: Compare vascular complications and incidence of bleeding of Impella 2.5 and intra-aortic balloon pump (IABP) in high-risk percutaneous coronary interventions (PCI). BACKGROUND: Large arterial sheath size for device insertion is associated with vascular and/or bleeding complications; gastrointestinal bleeding may also occur with anti-coagulation use. METHODS: Patients with an acute coronary syndrome receiving Impella 2.5 or IABP during high-risk PCI were studied (13 Impella; 62 IABP). Vascular complications and incidence of bleeding were compared. RESULTS: Post-procedure hematocrit was similar between groups. Blood transfusion occurred in 38.4% and 32.2% of patients in the Impella and IABP groups, respectively (P = NS); 65.3%, 30.7% and 3.8% of bleeding were due to vascular access site/procedure related, gastrointestinal and genitourinary, respectively. There was no statistical significant difference in vascular complications between the Impella and IABP groups (15.3% and 6.4% of patients, respectively); mesenteric ischemia (n = 1) and aortic rupture (n = 1) were only in the IABP group. In-hospital and one-year mortality were not statistically significant between groups. CONCLUSION: Impella can be used as safely as IABP during high-risk PCI with similar vascular and bleeding complications. Importantly, approximately one third of bleeding was from the gastrointestinal system warranting careful prophylactic measures and monitoring.

Post-infarct ventricular septal defect following thrombolytic intracranial bleed.

Mechanical complications after myocardial infarction are uncommon with advances in medical reperfusion strategies. However, such strategies are associated with bleeding complications which typically contraindicate surgical management. We describe a patient with a post-infarction ventricular septal defect and an intraventricular hemorrhage following thrombolytic therapy for an acute myocardial infarction.

Impact of 64-slice multidetector computed tomography on other diagnostic studies for coronary artery disease.

BACKGROUND: The clinical role of cardiovascular multidetector computed tomography (CT) remains in evolution, and application varies widely. Understanding its impact on the utilization of other cardiovascular diagnostic modalities could help define best practices. METHODS: Utilization of diagnostic testing was examined for the initial 1053 consecutive patients who underwent cardiovascular multidetector CT examinations after scanner installation in 2005. Yearly procedural volumes in the invasive catheterization and noninvasive stress laboratories were assessed before and after the introduction of multidetector CT. RESULTS: Ninety-one patients (8.6%) of the 1053 required invasive diagnostic catheterization; of these, nearly half subsequently underwent percutaneous or surgical intervention. Diagnostic catheterization and interventional volumes maintained their previous rates of annual increase, while the volume of stress testing decreased once multidetector CT became available. CONCLUSIONS: The major impact of multidetector CT in initial cardiovascular practice is on the need and frequency of stress testing, with far less impact on utilization of cardiac catheterization and coronary interventions.

Predictors of inpatient outcomes in hospitalized patients after left heart catheterization.

Clinical and laboratory factors predicting inpatient outcomes, specifically in-hospital mortality and length of stay (LOS), have not been defined for hospitalized patients specifically referred for left heart catheterization and coronary angiography (LHC). The objective of the study was to determine these outcomes and their predictors in hospitalized patients after LHC. Multivariate logistic regression models were used to identify risk factors for in-hospital mortality and Cox proportional hazards models were used to identify factors determining LOS in 9,420 consecutive patients hospitalized for LHC. Odds ratio for in-hospital mortality and hazard ratio for prolonged LOS were derived. The strongest predictors of mortality were advanced age, left ventricular (LV) end-diastolic pressure (EDP), LV ejection fraction (EF), systemic blood pressure, and renal insufficiency. Predictors of prolonged LOS were LVEDP, LVEF, 3-vessel coronary artery disease, and valvular disease. Clinical and laboratory characteristics of patients with an LVEF > or =50% were also compared with those of patients with an LVEF <50%. Predictors of mortality and LOS remained the same for patients with an LVEF <50%. For an LVEF > or =50%, LVEDP also determined LOS and chronic renal insufficiency provided predictive power to mortality and LOS in this subgroup. In conclusion, several readily attainable clinical and laboratory parameters predict inpatient mortality and LOS in hospitalized patients referred for LHC.

Drug eluting stent implantation for the treatment of symptomatic myocardial bridging is associated with favorable peri-procedural results and short-term outcomes.

Myocardial bridging is the most common congenital coronary abnormality, and is frequently found on post-mortem cardiac examination. Although often asymptomatic, clinical presentation can vary from unstable angina to sudden cardiac death. Only isolated cases of using drug eluting stents (DES) for bridging segments have been described. Our objective was to retrospectively analyze a series of patients undergoing percutaneous coronary intervention (PCI) with DES for symptomatic myocardial bridging and follow post-procedure outcomes. Results revealed favorable peri-procedural angiographic and short-term clinical results with DES implantation. Although initial data regarding DES implantation for symptomatic myocardial bridging are promising, long-term follow up, particularly related to in-stent restenosis will be important.

Inhibition of ribonucleotide reductase reduces neointimal formation following balloon injury.

Percutaneous transluminal coronary angioplasty (PTCA) has greatly benefited patients with occluded coronary arteries, but its benefits have been undermined by a high incidence of restenosis. The introduction of coronary stents has significantly improved the short and long term outcome but restenosis still occurs in approximately 15 to 30% of patients within 6 months. Research efforts are now being directed toward combination stenting and drug delivery. Among the therapeutic targets being pursued are agents that can impede smooth muscle cell migration and proliferation, as these processes are critical components of restenosis injury. We propose that inhibiting the conversion of ribonucleotides to deoxyribonucleotides will impede cell proliferation and, as such, limit the degree of restenosis. Therefore, we tested whether the potent ribonucleotide reductase inhibitors Didox (3,4-dihydroxybenzohydraxamic acid) and Imidate (ethyl-3,4,5-hydroxybenzimidate) can limit the neointimal proliferation associated with restenosis using a rat carotid model of balloon dilatation injury. Results demonstrated that both Didox and Imidate significantly reduced intimal thickening, resulting in a 71 and 62% decrease in the intima/media ratio, respectively. Similar efficacy was seen with the commercially available ribonucleotide reductase inhibitor hydroxyurea, demonstrating the importance of this enzyme in vascular remodeling. Results from cell proliferation studies suggest that the mechanism of protection is inhibition of smooth muscle cell (SMC) proliferation. In addition, Didox and Imidate (100 microM) are potent inhibitors of SMC migration, which may also contribute to their vascular protective effects. These results suggest that inhibition of ribonucleotide reductase may provide a potent strategy to prevent post-PTCA restenosis.

Rotational X-ray coronary angiography.

We designed and implemented a digital flat-panel-based rotational X-ray coronary angiography technique hypothesizing that luminal disease could be identified with less radiation exposure and contrast usage compared to conventional angiography. Individuals scheduled for diagnostic coronary angiography were prospectively enrolled. In addition to conventional acquisitions in standard planes, subjects underwent one additional left coronary artery (LCA) or right coronary artery (RCA) rotational (spin) acquisition using a predefined trajectory. Radiation exposure and contrast volume were recorded for each run. Seventy-five subjects were enrolled. When compared with standard five-view cine acquisition, LCA spin angiography with one cranial and one caudal run resulted in 34.38% +/- 13.65% less radiation, 18.98% +/- 4.97% less contrast, and comparable assessment of stenosis severity. One spin acquisition compared with three standard cine acquisitions for RCA angiography resulted in 59.31% +/- 29.07% lower radiation, no significant change in contrast, and comparable assessment of stenosis severity. Rotational X-ray coronary angiography provides comparable visualization of coronary anatomy compared with traditional nonrotational coronary angiography with significantly less radiation exposure and contrast volume.