Publications (14) View all
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Article: Advances in Cardiac SPECT and PET Imaging: Overcoming the Challenges to Reduce Radiation Exposure and Improve Accuracy.
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ABSTRACT: Nuclear cardiology came of age in the 1970s and subsequently has expanded so that more than 9 million single photon emission computed tomography (SPECT) studies are performed annually in North America. Coronary artery disease management has demanded a reliable technique that will detect, risk stratify, and assist with revascularization decisions. Using cardiac SPECT and positron-emission tomography (PET), researchers and clinicians have sought to achieve excellence in coronary artery disease diagnosis and risk stratification, and strive to achieve higher standards in these areas. Developments in other cardiac imaging modalities, however, such as cardiac computed tomography, cardiac magnetic resonance, and echocardiography, have raised expectations in terms of diagnostic accuracy and achieving high quality images with little or no ionizing radiation exposure. The challenge facing nuclear cardiology as it embarks upon a fifth decade of clinical use is whether high quality images can be obtained at lower radiation exposures. In this review we consider current practice in SPECT and PET perfusion imaging. We discuss emerging advances in techniques, technologies, and radiotracers that focus specifically on improvements in image quality that enhance diagnostic accuracy while reducing radiation exposure. We provide a perspective as to the future roles of cardiac SPECT and PET in ischemic heart disease, and consider emerging novel applications beyond perfusion imaging. Although for a number of years nuclear cardiology has shone brightly as a leading light for the imaging of ischemic heart disease, its half-life has not yet been reached. Instead, even with the pressure to reduce radiation exposure, the future continues to look bright for cardiac SPECT and PET.The Canadian journal of cardiology 12/2012; · 3.36 Impact Factor -
Article: Sphingosine-1-phosphate-induced release of TIMP-2 from vascular smooth muscle cells inhibits angiogenesis.
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ABSTRACT: Following myocardial infarction, angiogenesis occurs as a result of thrombus formation, which permits reperfusion of damaged myocardium. Sphingosine 1-phosphate (S1P) is a naturally occurring lipid mediator released from platelets and is found in high concentrations at sites of thrombosis. S1P might therefore be involved in regulating angiogenesis following myocardial infarction and might influence reperfusion. The aims of this study were to determine the effects of S1P in human coronary arterial cell angiogenesis and delineate the subsequent mechanisms. An in vitro model of angiogenesis was developed using a co-culture of human coronary artery endothelial cells, human coronary smooth muscle cells and human fibroblasts. In this model, S1P inhibited angiogenesis and this was dependent on the presence of smooth muscle cells. The mechanism of the inhibitory effect was through S1P-induced release of a soluble mediator from smooth muscle cells. This mediator was identified as tissue inhibitor of metalloproteinase-2 (TIMP-2). Release of TIMP-2 was dependent on S1P-induced activation of Rho kinase and directly contributed to incomplete formation of endothelial cell adherens junctions. This was observed as a diffuse localisation of VE-cadherin, leading to decreased tubulogenesis. A similar inhibitory response to S1P was demonstrated in an ex vivo human arterial model of angiogenesis. In summary, S1P-induced inhibition of angiogenesis in human artery endothelial cells is mediated by TIMP-2 from vascular smooth muscle cells. This reduces the integrity of intercellular junctions between nascent endothelial cells. S1P might therefore inhibit the angiogenic response following myocardial infarction.Journal of Cell Science 02/2012; 125(Pt 9):2267-75. · 6.11 Impact Factor -
Article: Low-dose cardiac imaging: reducing exposure but not accuracy.
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ABSTRACT: Cardiac imaging techniques that use ionizing radiation have become an integral part of current cardiology practice. However, concern has arisen that ionizing radiation exposure, even at the low levels used for medical imaging, is associated with the risk of cancer. From a single diagnostic cardiac imaging procedure, such risks are low. On a population basis, however, malignancies become more likely on account of stochastic effects being more probable as the number of procedures performed increases. In light of this, and owing to professional and industrial commitment to the as low as reasonably achievable (ALARA) principle, over the last decade major strides have been made to reduce radiation dose in cardiac imaging. Dose-reduction strategies have been most pronounced in cardiac computed tomography. This was important since computed tomography has rapidly become a widely used diagnostic alternative to invasive coronary angiography, and initial protocols were associated with relatively high radiation exposures. Advances have also been made in nuclear cardiology and in invasive coronary angiography, and these reductions in patient exposure have all been achieved with maintenance of image quality and accuracy. Improvements in imaging camera technology, image acquisition protocols and image processing have lead to reductions in patient radiation exposure without compromising imaging diagnostic accuracy.Expert Review of Cardiovascular Therapy 01/2012; 10(1):89-104. -
Article: Prognostic assessment of coronary artery bypass patients with 64-slice computed tomography angiography: anatomical information is incremental to clinical risk prediction.
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ABSTRACT: We sought to determine the incremental prognostic value of 64 multi-slice coronary computed tomography angiography (CCTA) in coronary artery bypass graft (CABG) patients. Prognostication in CABG patients can be difficult. Anatomical assessment of native coronary artery disease and graft patency might provide useful information, but the utility of CCTA in the assessment of CABG patients is unknown. Six hundred fifty-seven CABG patients with all-cause mortality follow-up were identified from a multicenter CCTA registry, of 10,628 patients from 5 CCTA centers. Clinical risk was profiled with modified logistic and additive EuroSCOREs (European Systems for Cardiac Operative Risk Evaluations). The CCTA defined coronary anatomy. Patients were classified by unprotected coronary territory (UCT) or a summary of native vessel disease and graft patency: the coronary artery protection score (CAPS). Forty-four deaths occurred during a mean follow-up of 20 months. Left ventricular ejection fraction, creatinine, age, severity of native vessel disease, UCT, CAPS, and EuroSCOREs were univariate predictors of mortality (p < 0.001). In multivariate analysis with additive EuroSCORE, UCT (p = 0.004) and CAPS were predictive of events (p < 0.001). In comparison with additive EuroSCORE, CAPS score was associated with a 27% net reclassification index. Coronary computed tomography angiography provides incremental anatomical data to clinical risk assessment to help determine the prognosis of patients after CABG. The CAPS evaluation with CCTA might help identify those patients at highest risk.Journal of the American College of Cardiology 11/2011; 58(23):2389-95. · 14.16 Impact Factor -
Article: Impact of temporary right ventricular pacing from different sites on echocardiographic indices of cardiac function.
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ABSTRACT: To assess the impact of pacing from different right ventricular (RV) pacing sites on left ventricular (LV) function. Chronic apical RV pacing may induce heart failure. To reduce this RV, mid-septum and outflow tract are suggested as alternative pacing sites. We therefore assessed cardiac performance during temporary RV pacing from apical vs. mid-septum or outflow tract sites, using echocardiography and electrocardiography. Patients scheduled for a permanent pacemaker underwent temporary pacing in dual-chamber mode (DDD) and with atrio-ventricular delay optimized. The ventricular lead was moved to either the RV apex, mid-septum or outflow tract. Comprehensive echocardiography was performed in each position. Twenty-two patients completed the study. The baseline data was collected at atrial pacing mode (AAI). QRS duration lengthened with RV apical pacing (97 ± 22 ms AAI vs. 154 ± 18 ms RV apical, P < 0.001) and shortened with mid-septum or outflow tract pacing (147 ± 14 ms RV mid-septum and 136 ± 16 ms RV outflow tract, P = 0.001 and P < 0.001, respectively, vs. RV apical). Right ventricular apical pacing was associated with reductions in stroke volume and LV ejection fraction (54 ± 6% AAI vs. 48 ± 5% RV apical, P = 0.001). Right ventricular mid-septum (52 ± 5%) and outflow tract (54 ± 6%) pacing improved LV ejection fraction in comparison with apical pacing (P < 0.01 for both). Pacing at all sites induced dyssynchrony. In comparison with RV apical pacing dyssynchrony was reduced by mid-septum or outflow tract pacing. Right ventricular pacing at the mid-septum or outflow tract results in narrower QRS complexes, less dyssynchrony, and better LV systolic function than RV apical pacing.Europace 07/2011; 13(12):1738-46. · 1.98 Impact Factor
