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Reginald Low

Publications and source records attributed to Reginald Low.

8 recordsLinked to original sources
PubMed2006

Prevention and reversal of cardiac hypertrophy by soluble epoxide hydrolase inhibitors.

Sustained cardiac hypertrophy represents one of the most common causes leading to cardiac failure. There is emerging evidence to implicate the involvement of NF-kappaB in the development of cardiac hypertrophy. However, several critical questions remain unanswered. We tested the use of soluble epoxide hydrolase (sEH) inhibitors as a means to enhance the biological activities of epoxyeicosatrienoic acids (EETs) to treat cardiac hypertrophy. sEH catalyzes the conversion of EETs to form the corresponding dihydroxyeicosatrienoic acids. Previous data have suggested that EETs may inhibit the activation of NF-kappaB-mediated gene transcription. We directly demonstrate the beneficial effects of several potent sEH inhibitors (sEHIs) in cardiac hypertrophy. Specifically, we show that sEHIs can prevent the development of cardiac hypertrophy using a murine model of pressure-induced cardiac hypertrophy. In addition, sEHIs reverse the preestablished cardiac hypertrophy caused by chronic pressure overload. We further demonstrate that these compounds potently block the NF-kappaB activation in cardiac myocytes. Moreover, by using in vivo electrophysiologic recordings, our study shows a beneficial effect of the compounds in the prevention of cardiac arrhythmias that occur in association with cardiac hypertrophy. We conclude that the use of sEHIs to increase the level of the endogenous lipid epoxides such as EETs may represent a viable and completely unexplored avenue to reduce cardiac hypertrophy by blocking NF-kappaB activation.

Animals↗
PubMed2006

Assessment of FFR-negative intermediate coronary artery stenoses by spectral analysis of the radiofrequency intravascular ultrasound signal.

BACKGROUND: Assessing the clinical importance of angiographically intermediate coronary artery stenoses at the time of cardiac catheterization remains a challenge. Spectral analysis of radiofrequency ultrasound backscatter signals, or virtual histology (VH), allows in vivo assessment of plaque composition. This study characterizes the VH composition of fractional flow reserve (FFR)-negative intermediate stenoses and adjacent vessel segments. METHODS: Intermediate coronary artery stenoses (> 40% and < 70% diameter stenosis) were assessed by pressure wire. If the FFR was > or = 0.75, percutaneous coronary intervention was deferred and VH was performed on the lesion and adjacent segments using a commercially available system. The primary clinical endpoint was any adverse cardiac event. RESULTS: Thirty-seven intermediate stenoses in 30 patients were studied. The reference vessel size was 3.02 +/- 0.71 mm, the QCA diameter stenosis was 52 +/- 6% and the FFR was 0.89 +/- 0.07. The target stenoses were characterized by VH as: thin-cap fibroatheroma (VH-TCFA; n = 22); fibrous cap atheroma (n = 5), fibrocalcific lesion (n = 7) and pathological intimal thickening (n = 3). The relative contribution of each stenosis plaque component was conserved across adjacent segments ("signature" plaque). Three patients, all with VH-TCFAs at index, had events in the clinical follow-up period of 12 +/- 2 months, but only 1 of these patients had an event related to the index stenosis. CONCLUSIONS: FFR-negative intermediate stenoses have heterogeneous plaque by VH, but are enriched in VH-TCFAs. Relative plaque composition is conserved along adjacent vessel segments. Although the specificity of VH-TCFA for index stenosis-related events appears low, larger trials are needed to assess the prognostic value of VH in this lesion subset.

Aged↗
PubMed2005

Functional roles of Cav1.3(alpha1D) calcium channels in atria: insights gained from gene-targeted null mutant mice.

BACKGROUND: Previous data suggest that L-type Ca2+ channels containing the Cav1.3(alpha(1D)) subunit are expressed mainly in neurons and neuroendocrine cells, whereas those containing the Cav1.2(alpha1C) subunit are found in the brain, vascular smooth muscle, and cardiac tissue. However, our previous report as well as others have shown that Cav1.3 Ca2+ channel-deficient mice (Cav1.3(-/-)) demonstrate sinus bradycardia with a prolonged PR interval. In the present study, we extended our study to examine the role of the Cav1.3(alpha1D) Ca2+ channel in the atria of Cav1.3(-/-) mice. METHODS AND RESULTS: We obtained new evidence to demonstrate that there is significant expression of Cav1.3 Ca2+ channels predominantly in the atria compared with ventricular tissues. Whole-cell L-type Ca2+ currents (I(Ca,L)) recorded from single, isolated atrial myocytes from Cav1.3(-/-) mice showed a significant depolarizing shift in voltage-dependent activation. In contrast, there were no significant differences in the I(Ca,L) recorded from ventricular myocytes from wild-type and null mutant mice. We previously documented the hyperpolarizing shift in the voltage-dependent activation of Cav1.3 compared with Cav1.2 Ca2+ channel subunits in a heterologous expression system. The lack of Cav1.3 Ca2+ channels in null mutant mice would result in a depolarizing shift in the voltage-dependent activation of I(Ca,L) in atrial myocytes. In addition, the Cav1.3-null mutant mice showed evidence of atrial arrhythmias, with inducible atrial flutter and fibrillation. We further confirmed the isoform-specific differential expression of Cav1.3 versus Cav1.2 by in situ hybridization and immunofluorescence confocal microscopy. CONCLUSIONS: Using gene-targeted deletion of the Cav1.3 Ca2+ channel, we established the differential distribution of Cav1.3 Ca2+ channels in atrial myocytes compared with ventricles. Our data represent the first report demonstrating important functional roles for Cav1.3 Ca2+ channel in atrial tissues.

Animals↗
PubMed2004

Characterization of a KCNQ1/KVLQT1 polymorphism in Asian families with LQT2: implications for genetic testing.

Congenital long QT syndrome (LQTS) is a genetic disease that predisposes affected individuals to arrhythmias, syncope, and sudden death. Mutations in several ion channel genes have been discovered in different families with LQTS: KCNQ1 (KVLQT1, LQT1), KCNH2 (HERG, LQT2), SCN5A (LQT3), KCNE1 (minK, LQT5), and KCNE2 (MiRP1, LQT6). Previously, the P448R-KVLQT1 missense mutation has been reported as an LQT1-causing mutation. In this report, we demonstrate the presence of the P448R polymorphism in two, unrelated Chinese LQTS families. Although absent from 500 reference alleles derived from 150 white and 100 African-American subjects, P448R was present in 14% of healthy Chinese volunteers. Given the inconsistencies between the genotype (LQT1) and clinical phenotype (LQT2) in our two LQTS families, together with the finding that the P448R appears to be a common, ethnic-specific polymorphism, mutational analysis was extended to the other LQTS-causing genes resulting in the identification of distinct HERG missense mutations in each of these two families. Heterologous expression of P448R-KVLQT1 yielded normal, wild-type (WT) currents. In contrast, the two unique HERG mutations resulted in dominant-negative suppression of the WT HERG channel. Our study has profound implications for those engaged in genetic research. Importantly, one child of the original proband was initially diagnosed with LQT1 based upon the presence of P448R-KVLQT1 and was treated with beta-blockers. However, he did not possess the subsequently determined LQT2-causing mutation. On the other hand, his untreated P448R-negative brother harbored the true, disease-causing HERG mutation. These findings underscore the importance of distinguishing channel polymorphisms from mutations pathogenic for LQTS and emphasize the importance of using appropriate ethnically matched controls in the genotypic analysis of LQTS.

Alleles↗
PubMed2003

Prospective, randomized evaluation of thrombectomy prior to percutaneous intervention in diseased saphenous vein grafts and thrombus-containing coronary arteries.

OBJECTIVES: We sought to determine whether routine thrombectomy prior to stent implantation in diseased saphenous vein grafts (SVGs) and thrombus-containing native coronary arteries would reduce peri-procedural myonecrosis and subsequently enhance event-free survival. BACKGROUND: Percutaneous coronary intervention in diseased SVGs and thrombotic native coronary arteries is complicated by a high rate of peri-procedural myocardial infarction (MI). Thrombectomy prior to intervention may enhance the safety of intervention and improve early and late outcomes in these high-risk patients. METHODS: At 60 centers in the U.S. and Canada, 797 patients with 839 diseased SVGs or thrombus-containing native coronary arteries were prospectively randomized to stent implantation with versus without prior thrombectomy with the X-SIZER device (ev3, Plymouth, Minnesota). RESULTS: Peri-procedural MI occurred in 15.8% of patients assigned to the X-SIZER device compared with 16.6% of control patients (p = 0.77), although the rate of large MI (pre-specified as the development of new pathologic Q waves or creatine phosphokinase-MB isoenzyme elevation >8 x upper limits of normal) was reduced with X-SIZER device use from 9.6% to 5.5% (multivariate risk ratio 0.35 [95% confidence interval 0.18 to 0.66], p = 0.002). Major adverse cardiac events (cardiac death, MI, or repeat target vessel revascularization) occurred in 16.8% of X-SIZER patients versus 17.1% of control patients at 30 days (p = 0.92), and in 31.3% of X-SIZER patients versus 28.2% of control patients at 1 year (p = 0.35). CONCLUSIONS: Thrombectomy with the X-SIZER device prior to stent implantation in high-risk diseased SVGs and thrombus-containing native coronary arteries may reduce the extent, but not the occurrence, of myonecrosis. Early and late event-free survival, however, were not improved by routine thrombectomy with this device.

Adult↗
PubMed2003

Catheter-based coronary bypass: a development update.

Catheter-based coronary bypass has evolved since its origin in 1995. We present a status update of one version of catheter-based bypass, percutaneous in situ coronary venous arterialization (PICVA), its successes and failures, and the many questions and challenges that remain. Initial clinical experience with PICVA demonstrated promising mitigation of angina in no-option patients, but was complicated by a relatively low procedural completion rate and a high incidence of MACE. A great deal was learned in these initial cases. The system of devices is currently undergoing significant modification, and further clinical study is underway.

Cardiac Catheterization↗
PubMed2003

Safety and efficacy of a novel device for treatment of thrombotic and atherosclerotic lesions in native coronary arteries and saphenous vein grafts: results from the multicenter X-Sizer for treatment of thrombus and atherosclerosis in coronary applications trial (X-TRACT) study.

Intervention in thrombotic lesions and diseased saphenous vein grafts frequently results in thromboembolic complications, including no-reflow, distal branch occlusion, periprocedural MI, and death. The utility of a novel thromboatherectomy device, the X-Sizer, was tested in 50 consecutive patients at nine U.S. centers. A total of 61 lesions were treated in 31 vein grafts and 19 native coronary arteries; thrombus was present in 78% of lesions, and TIMI 0-1 flow in 21%. TIMI 3 flow improved from 57% at baseline to 94% postprocedure. No patient developed visible distal thromboemboli, side-branch occlusion, or reduced antegrade flow. Thirty-day events included one death (2.0%), Q- or non-Q-wave MI in 4.0%, TVR in 6.0%, and any MACE in 6.0%. We conclude that the use of the X-Sizer prior to percutaneous intervention is safe in high-risk vein grafts and thrombotic lesions and results in a low rate of adverse events compared to historical controls.

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