Publications by authors named "Ramon A Partida"

8 Publications

  • Page 1 of 1

Plaque erosion: a new in vivo diagnosis and a potential major shift in the management of patients with acute coronary syndromes.

Eur Heart J 2018 06;39(22):2070-2076

Cardiology Division, Massachusetts General Hospital, Harvard Medical School, 55 Fruit Street, GRB 800, Boston, MA 02114, USA.

Pathology and in vivo imaging studies have identified superficial plaque erosion as a frequent and important mechanism underlying acute coronary syndromes (ACS). In contrast with plaque rupture, the pathophysiological mechanisms leading to plaque erosion remain poorly understood. The advent of intravascular imaging techniques, particularly optical coherence tomography, has aided understanding of this mode of ACS in vivo by complementing previous insights from pathology studies. Appreciation of the distinct biological and clinical mechanisms of plaque erosion points to the possibility of tailored management strategies for patients presenting with ACS.
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http://dx.doi.org/10.1093/eurheartj/ehx786DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5991215PMC
June 2018

Contemporary Drug-Eluting Stent Platforms: Design, Safety, and Clinical Efficacy.

Interv Cardiol Clin 2016 07 21;5(3):331-347. Epub 2016 Jun 21.

Harvard Medical School, 25 Shattuck Street, Boston, MA 02115, USA; Department of Medicine, Smith Center for Outcomes Research in Cardiology, CardioVascular Institute, Beth Israel Medical Center, 330 Brookline Avenue, Baker 4, Boston, MA 02215, USA; Harvard Clinical Research Institute, Boston, MA, USA. Electronic address:

First-generation drug-eluting stents significantly improved treatment of coronary disease, decreasing rates of revascularization. This was offset by high rates of late adverse events, driven primarily by stent thrombosis. Research and design improvements of individual DES platform components led to next-generation devices with superior clinical safety and efficacy profiles compared with bare-metal stents and first-generation drug-eluting stents. These design improvements and features are explored, and their resulting clinical safety and efficacy reviewed, focusing on platforms approved by the Food and Drug Administration currently widely used in the United States.
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http://dx.doi.org/10.1016/j.iccl.2016.02.003DOI Listing
July 2016

Contemporary Drug-Eluting Stent Platforms: Design, Safety, and Clinical Efficacy.

Cardiol Clin 2017 May;35(2):281-296

Harvard Medical School, 25 Shattuck Street, Boston, MA 02115, USA; Department of Medicine, Smith Center for Outcomes Research in Cardiology, CardioVascular Institute, Beth Israel Medical Center, 330 Brookline Avenue, Baker 4, Boston, MA 02215, USA; Harvard Clinical Research Institute, Boston, MA, USA. Electronic address:

First-generation drug-eluting stents significantly improved treatment of coronary disease, decreasing rates of revascularization. This was offset by high rates of late adverse events, driven primarily by stent thrombosis. Research and design improvements of individual DES platform components led to next-generation devices with superior clinical safety and efficacy profiles compared with bare-metal stents and first-generation drug-eluting stents. These design improvements and features are explored, and their resulting clinical safety and efficacy reviewed, focusing on platforms approved by the Food and Drug Administration currently widely used in the United States.
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http://dx.doi.org/10.1016/j.ccl.2016.12.010DOI Listing
May 2017

Transcatheter Mitral Valve Interventions: Current Therapies and Future Directions.

Curr Treat Options Cardiovasc Med 2017 May;19(5):32

Department of Medicine, Cardiology Division, Massachusetts General Hospital, 55 Fruit Street, GRB 800, Boston, MA, 02114, USA.

Opinion Statement: Transcatheter interventions for the treatment of aortic valve stenosis have become commonplace since the advent of transcatheter aortic valve implantation. However, transcatheter mitral valve therapies have lagged in development due to the complexity of mitral valve anatomy. Transcatheter edge-to-edge leaflet repair using the MitraClip device provides an option for the treatment of severe primary mitral valve regurgitation in high or prohibitive surgical risk patients, and multiple novel approaches are evolving to replace or repair the mitral valve. Devices for the treatment of calcific mitral stenosis, primary mitral regurgitation, and functional mitral regurgitation have been developed and are currently either being evaluated in clinical trials or are in earlier stages of preclinical development. We are optimistic that our armamentarium will soon expand to include a myriad of transcatheter interventions for mitral valve disease.
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http://dx.doi.org/10.1007/s11936-017-0538-2DOI Listing
May 2017

Elimination of Transcoarctation Pressure Gradients Has No Impact on Left Ventricular Function or Aortic Shear Stress After Intervention in Patients With Mild Coarctation.

JACC Cardiovasc Interv 2016 09;9(18):1953-65

Institute for Medical Engineering and Science, Massachusetts Institute of Technology, Cambridge, Massachusetts; Cardiovascular Division, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts.

Objectives: This study sought to investigate the impact of transcatheter intervention on left ventricular function and aortic hemodynamics in patients with mild coarctation of the aorta (COA).

Background: The optimal method and timing of transcatheter intervention for COA remains unclear, especially when the severity of COA is mild (peak-to-peak transcoarctation pressure gradient <20 mm Hg). Debate rages regarding the risk/benefit ratio of intervention versus long-term effects of persistent minimal gradient in this heterogeneous population with differing blood pressures, ventricular function, and peripheral perfusion.

Methods: We developed a unique computational fluid dynamics and lumped parameter modeling framework based on patient-specific hemodynamic input parameters and validated it against patient-specific clinical outcomes (before and after intervention). We used clinically measured hemodynamic metrics and imaging of the aorta and the left ventricle in 34 patients with mild COA to make these correlations.

Results: Despite dramatic reduction in the transcoarctation pressure gradient (catheter and Doppler echocardiography pressure gradients reduced by 75% and 47.3%, respectively), there was only modest effect on aortic flow and no significant impact on aortic shear stress (the maximum time-averaged wall shear stress in descending aorta was reduced 5.1%). In no patient did transcatheter intervention improve left ventricular function (e.g., stroke work and normalized stroke work were reduced by only 4.48% and 3.9%, respectively).

Conclusions: Transcatheter intervention that successfully relieves mild COA pressure gradients does not translate to decreased myocardial strain. The effects of the intervention were determined to the greatest degree by ventricular-vascular coupling hemodynamics and provide a novel valuable mechanism to evaluate patients with COA that may influence clinical practice.
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http://dx.doi.org/10.1016/j.jcin.2016.06.054DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5402700PMC
September 2016

Edoxaban: pharmacological principles, preclinical and early-phase clinical testing.

Future Cardiol 2011 Jul;7(4):459-70

Department of Medicine, Brigham & Women's Hospital, Harvard Medical School, Boston, MA, USA.

Vitamin K antagonists have been the cornerstone of oral antithrombotic therapy to help prevent ischemic stroke in atrial fibrillation (AF) and reduce venous thromboembolic events. Despite proven clinical benefit, vitamin K antagonists have several limitations, including a narrow therapeutic window, slow onset/offset of action, need for close monitoring and significant drug/food interactions, highlighting the need for alternative therapies. Recently, the direct thrombin inhibitor dabigatran was approved by the US FDA for use in AF, and several factor Xa inhibitors are in late-stage clinical testing. Edoxaban is a novel, oral, reversible, direct factor Xa inhibitor with rapid absorption and predictable dose-dependent anticoagulation effects. Early clinical studies have shown promising results and it is currently undergoing large-scale Phase III trials for stroke prevention in AF and venous thromboembolic event prophylaxis and treatment. This review provides an overview of the current understanding, clinical trial results and pharmacology of edoxaban.
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http://dx.doi.org/10.2217/fca.11.28DOI Listing
July 2011

Electrical impedance in bovine skeletal muscle as a model for the study of neuromuscular disease.

Physiol Meas 2006 Dec 10;27(12):1269-79. Epub 2006 Oct 10.

Department of Neurology, Division of Neuromuscular Diseases, Harvard Medical School, Beth Israel Deaconess Medical Center, 330 Brookline Avenue, Boston, MA 02215, USA.

Electrical impedance myography (EIM) consists of a set of bioimpedance methods configured for neuromuscular disease assessment, in which high-frequency electrical current is applied to a limb and the consequent surface voltage pattern over a muscle is evaluated. Prior human work has shown that the EIM parameters of resistance, reactance and phase change in different neuromuscular disease states including neurogenic and myopathic conditions. These parameters are also sensitive to the angle at which current is applied and measured relative to muscle fiber direction, a characteristic known as anisotropy. In order to obtain insights into the impedance characteristics of mammalian skeletal muscle without the confounding effects of an overlying skin-fat layer, bone and irregular muscle shape, we performed EIM on three 'nearly ideal' round 16 cm diameter, 1 cm equal thickness pieces of bovine rectus abdominis muscle. Using a standardized tetrapolar electrode array with 50 kHz electrical current, we identified strong anisotropy in the measured reactance and phase, with weaker anisotropy identified for resistance. We also found that increasing amounts of muscle maceration, a rough model of myopathic or traumatic muscle fiber injury, reduced phase and muscle anisotropy when current was injected perpendicular to the muscle fibers. These findings support that EIM parameters, including muscle anisotropy, are likely to be sensitive to the pathological changes that occur in neuromuscular disease states.
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http://dx.doi.org/10.1088/0967-3334/27/12/002DOI Listing
December 2006

Electrode position and size in electrical impedance myography.

Clin Neurophysiol 2005 Feb;116(2):290-9

The Department of Neurology, Division of Neuromuscular Diseases, Harvard Medical School, Beth Israel Deaconess Medical Center and the Department of Physics, Northeastern University, Boston, MA 02215, USA.

Objective: Linear-electrical impedance myography (EIM) is a non-invasive technique for the evaluation of muscle, in which high-frequency alternating current is injected into the body via two surface electrodes, and the resulting voltage pattern over a selected muscle is measured using a second, larger set of electrodes. The precise location and size of the electrodes can be critical to the data obtained, and in this study the effects of variation in these factors were evaluated.

Methods: Linear-EIM was performed in 5 subjects while varying the location of the current injecting electrodes and in an additional 8 subjects while varying the position of the voltage electrodes.

Results: The major outcome variable, the 'spatially averaged phase' (theta(avg)), decreased as the ipsilateral current injecting electrode was moved farther from the voltage electrodes, reaching a plateau 15-20 cm distant. As for the voltage electrode array, distal-proximal shifts resulted in the greatest changes, with variation in theta(avg) being as high as 14% per cm; circumferential shifts around the limb had more modest effects.

Conclusions: Linear-EIM results depend systematically on current and voltage electrode positions, but with reasonable care variation can be minimized.

Significance: With proper attention to electrode placement, linear-EIM has sufficient reproducibility to become an important clinical tool in neuromuscular disease evaluation.
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http://dx.doi.org/10.1016/j.clinph.2004.09.002DOI Listing
February 2005
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