Characterization of operator learning curve for transradial coronary interventions

BACKGROUND

Transradial percutaneous coronary intervention (TR-PCI) improves clinical outcomes compared to the transfemoral (TF) approach. However, inadequate training and experience has limited widespread adoption by interventional cardiologists.

METHODS AND RESULTS

Clinical and procedural characteristics for TR-PCI were prospectively collected from 1999 to 2008. To identify minimum case volume for optimum clinical benefit, single-vessel TR-PCI cases were chronologically ranked and stratified into 1 to 50, 51 to 100, 101 to 150 and 151 to 300 case volume groups for operators starting the TR approach at the study institution. Cases by operators with a >300 TR-PCI case volume comprised the control group. TR-PCI failure rates, contrast use, guide usage, and fluoroscopy time were compared among groups. A total of 1672 patients underwent TR-PCI by 28 operators. TR-PCI failure occurred in 4% and was higher in the 1 to 50 case volume group compared to the 51 to 100 (P=0.007) and control (P=0.01) groups. Contrast use was greater in the 1 to 50 group (180±79 mL) compared to the 151 to 300 (157±75 mL, P=0.02) and control (168±79 mL, P=0.05) groups. Fluoroscopy time was higher in the 1 to 50 group (15±10 minutes) compared to the 101 to 150 (13±10 minutes, P=0.04) and control (12±9 minutes, P=0.02) groups. Reasons for TR-PCI failure included spasm (38%), subclavian tortuousity (16%), poor guide support (16%), failed access (10%), and radial loop (7%). Case volume was significantly correlated with TR-PCI failure (β=-0.0076, P=0.0028), and odds of failure was reduced by 32% for each 50 increments in case volume.

CONCLUSIONS

TR-PCI success depends on operator experience, and a case volume of ≥50 cases is required to achieve outcomes comparable to experienced operators. These findings have implications both for PCI operators looking to expand their skills and for defining standards for training.

Increased myocardial expression of angiopoietin-2 in patients undergoing urgent surgical revascularization for acute coronary syndromes

BACKGROUND

Myocardial ischemia triggers the expression of multiple angiogenic factors including vascular endothelial growth factor and its receptors. However, vascular endothelial growth factor does not act in isolation.

OBJECTIVE

To identify other genes important in the angiogenic response to clinically relevant myocardial ischemia.

METHODS AND RESULTS

Paired intraoperative biopsies of ischemic and nonischemic myocardium were obtained from 12 patients with acute coronary syndromes (ACS) undergoing urgent coronary artery bypass graft surgery. Real-time polymerase chain reaction demonstrated significant upregulation of angiopoietin-2 (Ang-2) in ischemic myocardium, to a greater extent than other classical angiogenic factors. Microarray gene profiling identified Ang-2 to be among the top 10 differentially upregulated genes, in addition to genes involved in inflammation, cell signalling, remodelling and apoptosis.

CONCLUSIONS

The present document is the first report of microarray analysis of patients with ACS, and supports an important role for Ang-2 in the angiogenic response to severe ischemia in the human heart. Common gene expression patterns in ACS may provide opportunities for targeted pharmacological and cellular intervention.

Chorea in a pregnant woman with rheumatic mitral stenosis

Chorea gravidarum is a rare movement disorder of pregnancy with a broad differential diagnosis. Although often a benign condition, it may indicate underlying acute rheumatic fever, antiphospholipid antibody syndrome or a hypercoagulable state. However, now that rheumatic fever is rare in western countries, chorea gravidarum occurs most commonly in patients with chronic rheumatic heart disease. Heightened awareness of chorea gravidarum and the morbidity of the often associated rheumatic heart disease, particularly in immigrants from developing countries, is essential for early diagnosis and effective management. A case of chorea gravidarum in a woman with rheumatic mitral stenosis is described. The diagnostic approach, pathophysiology and management of this rare condition are discussed.

The exchange factor Ras-GRF2 activates Ras-dependent and Rac-dependent mitogen-activated protein kinase pathways

Ras and Rac are membrane-associated GTPases that function as molecular switches activating intracellular mitogen-activated protein kinase (MAPK) cascades and other effector pathways in response to extracellular signals [1]. Activation of Ras and Rac into their GTP-bound conformations is directly controlled by specific guanine-nucleotide exchange factors (GEFs), which catalyze GDP release. Several Ras-specific GEFs that are related to the budding yeast protein Cdc25p have been described, whereas GEFs for Rac-related GTPases contain a region that is homologous to the oncoprotein DbI [2-3]. The Ras-GRF1 and Ras-GRF2 proteins, which couple Ras activation to serpentine receptors and calcium signals, contain both Cdc25 and DbI homology (DH) regions [3-4]. Here, we demonstrate that Ras-GRF2 is a bifunctional signaling protein that is able to bind and activate Ras and Rac, and thereby coordinate the activation of the extracellular-signal-regulated kinase (ERK) and stress-activated protein kinase (SAPK) pathways.

A 54-kDa protein related to ras-guanine nucleotide release factor expressed in the rat exocrine pancreas

The polymerase chain reaction was used to amplify a cDNA encoding the catalytic region of ras-guanine nucleotide release factor (ras-GRF1) from mouse embryonic stem cell mRNA. Antibodies directed against this protein were prepared and affinity purified. Western immunoblotting of rat tissue lysates revealed a 140-kDa protein in brain as expected but, in addition, a strongly immunoreactive 54-kDa protein, p54, was identified in pancreas. Expression of ras-GRF1 in pancreas was confirmed at the RNA level by reverse-transcriptase-coupled polymerase chain reaction analysis; p54 may therefore correspond to a form of ras-GRF1 or a closely related protein. The cellular and subcellular localization of p54 was investigated by enzyme-linked immunocytochemistry and immunogold electron microscopy. In the pancreas, p54 was expressed primarily in acinar cells, where it was localized along the basolateral and apicolateral plasma membranes. Indirect immunofluorescence microscopy of cultured acini further indicated that the plasma membrane localization of p54 was dependent on the maintenance of the acinar histotype and organized acinar structure. When primary acinar cells were permitted to dissipate into monolayer cultures devoid of zymogen granules, ras-GRF1 staining became cytosolic. Our results suggest that ras-GRF1 is involved in the structure and function of the pancreas.

Cloning and characterization of Ras-GRF2, a novel guanine nucleotide exchange factor for Ras

Conversion of Ras proteins into an activated GTP-bound state able to bind effector proteins is catalyzed by specific guanine nucleotide exchange factors in response to a large number of extracellular stimuli. Here we report the isolation of mouse cDNAs encoding Ras-GRF2, a multidomain 135-kDa protein containing a COOH-terminal Cdc25-related domain that stimulates release of GDP from Ras but not other GTPases in vitro. Ras-GRF2 bound specifically to immobilized Ras lacking bound nucleotides, suggesting stabilization of the nucleotide-free form of Ras as a mechanism of catalyzing nucleotide exchange. The NH2-terminal region of Ras-GRF2 is predicted to contain features common to various signaling proteins including two pleckstrin homology domains and a Dbl homology region. Ras-GRF2 also contains an IQ motif which was required for its apparent constitutive association with calmodulin in epithelial cells ectopically expressing Ras-GRF2. Transient expression of Ras-GRF2 in kidney epithelial cells stimulated GTP binding by Ras and potentiated calcium ionophore-induced activation of mitogen-activated protein kinase (ERK1) dependent upon the IQ motif. Calcium influx caused Ras-GRF2 subcellular localization to change from cytosolic to peripheral, suggesting a possible mechanism for controlling Ras-GRF2 interactions with Ras at the plasma membrane. Epithelial cells overexpressing Ras-GRF2 are morphologically transformed and grow in a disorganized manner with minimal intercellular contacts. Northern analysis indicated a 9-kb GRF2 transcript in brain and lung, where p135 Ras-GRF2 is known to be expressed, and RNAs of 12 kb and 2.2 kb were detected in several tissues. Thus, Ras-GRF2 proteins with different domain structures may be widely expressed and couple diverse extracellular signals to Ras activation.