Samuel Unzek Freiman

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Journals/Publications

• Alexanderson Rosas, E., Kerik, N. E., Unzek Freiman, S., & Fermon Schwaycer, S. (2020). [Principles and applications of positron emission tomography (PET) in cardiology. PET in Mexico: a reality]. Archivos de cardiologia de Mexico, 72(2), 157-64.
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  Positron emission tomography (PET) offers the unique capability of measuring non-invasive by the regional myocardial substrate flow and the biochemical reaction index in millimol per minute per gram of myocardial tissue. PET also allows for the assessment or quantification of regional myocardial blood flow, cardiac metabolism, ventricular function, myocardial viability, as well as autonomous nervous system, research and evaluating of dilated myocardiopathy and of ventricular hypertrophy. PET's success is based on the radioisotopes properties, their very short half-life allows for the administration of large doses.
• Alexánderson, E., Rubinstein, J., Unzek, S., Serratos, J. E., Motola, D., Arroyo, A., Alexánderson, G., Lorenzo, A., & Victoria, D. (2020). [Myocardial perfusion evaluated with a 2-isotope technique. Experience with the first 1600 cases in Mexico]. Archivos del Instituto de Cardiologia de Mexico, 70(3), 234-40.
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  SPECT has a high sensitivity for the diagnosis of coronary artery disease. Dual isotope protocol using rest thallium and stress MIBI was introduced in Mexico 4 years ago. This protocol reunite the advantages of both radiotracers for the study of myocardial perfusion. We present our experience of the first three years. One thousand six hundred patients were studied with suspected myocardial ischemia; 288 were excluded because of an absence of a proper follow up. In 895 of the 1312 patients a coronariography was performed. Images were evaluated by dividing the heart in 20 segments using a 5 points scale (0 = normal to 4 = absence of perfusion). It was considered a perfusion defect when a segment had a score greater or equal to 2 and the SPECT study was considered abnormal if two or more segments had a MIBI stress score equal or greater than 2. The global sensitivity for diagnosis of ischemia was 96.28%. Dual isotope method is appropriate for the diagnosis of ischemic heart disease. It has a high sensitivity and specificity for the recognition of global coronary disease and for specific coronary territories. This work constitutes the greatest series in Latin America that uses this diagnosis method.
• Chhatriwalla, A. K., Cam, A., Unzek, S., Bhatt, D. L., Raymond, R. E., Lincoff, A. M., Whitlow, P. L., Ellis, S. G., Tuzcu, E. M., & Kapadia, S. R. (2020). Drug-eluting stent fracture and acute coronary syndrome. Cardiovascular revascularization medicine : including molecular interventions, 10(3), 166-71.
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  Coronary stent fracture is an underrecognized entity but has been reported more frequently in the drug-eluting stent (DES) era. Nevertheless, the clinical implications of coronary stent fracture remain unclear.
• Unzek, S., Galla, J. M., Cerqueira, M. D., & Jaber, W. A. (2020). Tc-99m tetrofosmin uptake in a male patient with gynecomastia. Journal of nuclear cardiology : official publication of the American Society of Nuclear Cardiology, 14(6), 902-3.
• Desai, S., Unzek, S., Arsanjani, R., Krause, S., Nguyen, B., Shamoun, F., & Pavlicek, W. (2019). Urinary Voiding as a Tool to Reduce Radiation Exposure in the Nuclear Stress Lab. Journal of nuclear medicine technology, 47(2), 160-162.
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  Nuclear stress testing is being increasingly justified in the cardiovascular risk stratification of patients. Radiation is an important consideration, and attempts to minimize exposure should be implemented. Efficiency and cost effectiveness are cornerstones in the delivery of quality patient care and should also be considered when implementing change. We studied 88 consecutive patients who presented to our stress lab for pharmacologic nuclear stress testing. A single-day rest-and-stress protocol with low-level exercise was used for all patients. After the stress portion of the examination, we measured Geiger counter activity above the bladder area to establish a baseline. Patients were then allowed to void, and repeat measurements were taken. We detected a 16.9% reduction from baseline radiation levels above the bladder area after voiding. Urinary voiding is a simple, cost-effective strategy at reducing radiation exposure in the nuclear stress lab.
• Chakkera, H. A., Angadi, S. S., Heilman, R. L., Kaplan, B., Scott, R. L., Bollempalli, H., Cha, S. S., Khamash, H. A., Huskey, J. L., Mour, G. K., Sukumaran Nair, S., Singer, A. L., Reddy, K. S., Mathur, A. K., Moss, A. A., Hewitt, W. R., Qaqish, I., Behmen, S., Keddis, M. T., , Unzek, S., et al. (2018). Cardiorespiratory Fitness (Peak Oxygen Uptake): Safe and Effective Measure for Cardiovascular Screening Before Kidney Transplant. Journal of the American Heart Association, 7(11).
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  Significant heterogeneity exists in practice patterns and algorithms used for cardiac screening before kidney transplant. Cardiorespiratory fitness, as measured by peak oxygen uptake (VO), is an established validated predictor of future cardiovascular morbidity and mortality in both healthy and diseased populations. The literature supports its use among asymptomatic patients in abrogating the need for further cardiac testing.
• Chao, C. J., Jaroszewski, D., Gotway, M., Ewais, M., Wilansky, S., Lester, S., Unzek, S., Appleton, C. P., Chaliki, H. P., Gaitan, B. D., Mookadam, F., & Naqvi, T. Z. (2018). Effects of Pectus Excavatum Repair on Right and Left Ventricular Strain. The Annals of thoracic surgery, 105(1), 294-301.
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  The cardiopulmonary benefits of pectus excavatum repair have been debated. Echocardiographic speckle-tracking strain and strain rate have been used to evaluate and detect subclinical myocardial dysfunction in patients receiving cardiotoxic chemotherapy, and patients with valvular heart disease. This technology was applied to evaluate the effects of pectus excavatum surgery on left ventricular (LV) and right ventricular (RV) function.
• Arsanjani, R., Lohrmann, G., Allen, S., Unzek, S., & Mookadam, F. (2016). A Multi-Modality Approach to Left Ventricular Aneurysms: True vs False. The American journal of medicine, 129(8), e113-6.
• Quader, N., Jalal, U., Raslan, S., Srivathsan, K., Wilansky, S., Unzek, S., Chandrasekran, K., & Mookadam, F. (2013). Worsening left ventricular apical peak strain early after right ventricular pacing. Ultrasound in medicine & biology, 39(2), 261-8.
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  We aimed to determine the effect of short-term right ventricle pacing (RV) on left ventricle (LV) mechanics using speckle tracking analysis. Conventional echocardiography and two-dimensional strain imaging was studied in 38 patients, mean age 81.6 ± 7.0, that had undergone pacemaker placement and were greater than 90% ventricularly paced. Mean duration of 24 months of RV pacing resulted in a significant decline in: LV apical diastolic rotational velocities (-59.0 ± -38.9 °/s to -28.0 ± -11.5 °/s, p 0.02), peak strain in the LV apical septal wall (-15.6 ± 8.5 to -13.5 ± 7.6, p 0.02), peak strain in LV apical lateral wall (-13.4 ± 8.9 to -11.4 ± 7.3, p 0.02). Thus, with only 24 months of RV pacing, there was a significant decline in peak strain of the LV apex and in apical diastolic rotational velocity that could account for eventual decline in left ventricular function.
• Pandit, A., & Unzek Freiman, S. (2012). Complete heart block associated with regadenoson: a real side effect. Journal of nuclear cardiology : official publication of the American Society of Nuclear Cardiology, 19(6), 1236-9.
• Unzek, S., & Mookadam, F. (2012). Aortic stenosis and perioperative risk: the other obstructive defect. The Journal of heart valve disease, 21(3), 311-3.
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  Whilst the prevalence of aortic valve stenosis (AS) increases with age (1), surgery restores age-corrected survival to near normal. In parallel with senescence, comorbidities are present, one such example being chronic obstructive pulmonary disease (COPD), which causes significant disability and is the third leading cause of death in the United Sates (2). The presence of COPD is associated with increased perioperative complications, and serve as a reason to deny a patient surgical intervention because of the increased surgical risk (3).
• Unzek, S., Popovic, Z. B., Marwick, T. H., & , D. G. (2011). Effect of recommendations on interobserver consistency of diastolic function evaluation. JACC. Cardiovascular imaging, 4(5), 460-7.
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  We sought the impact of recent recommendations on observer concordance on interpretation of diastolic stage and assessment of filling pressure.
• Chhatriwalla, A. K., Unzek, S., & Kapadia, S. R. (2010). Recurrent stent fracture in the right coronary artery. Clinical cardiology, 33(12), E70-2.
• Menon, V., Sengupta, J., & Unzek, S. (2009). Optimal management of acute aortic dissection. Current treatment options in cardiovascular medicine, 11(2), 146-55.
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  Acute aortic syndrome (AAS) encompasses a group of life-threatening aortic disorders that are increasing in prevalence. It classically presents with abrupt-onset chest pain that is of maximum intensity at onset. The syndrome requires prompt recognition and efficient treatment to optimize outcome. Contrast-enhanced CT is most commonly used as the definitive diagnostic imaging modality. Patients must be expeditiously transferred to institutions with case experience and medical, surgical, and endovascular expertise. Stanford type A dissections involve the ascending aorta and require emergent surgical consideration, unless underlying comorbidities make surgical risk prohibitive. Patients with Stanford type B, or descending, aortic dissection are less prone to rupture, shock, and cardiac complications. These patients are initially medically managed with targeted blood pressure and heart rate control. Surgical management is reserved for patients with intractable or recurrent pain, aortic expansion, end-organ ischemia, or progression of dissection. The feasibility of endovascular treatment is established, and its role in management continues to expand. Long-term follow-up with medical treatment and serial imaging of AAS patients is critical. Future directions in the diagnosis and treatment of AAS include using biomarkers to aid in diagnosis and prognosis, enhanced imaging with better resolution and reduced radiation exposure, and definition of the role of endovascular methods in acute and chronic settings.
• Unzek, S., & Francis, G. S. (2008). Management of heart failure: a brief review and selected update. Cardiology clinics, 26(4), 561-71.
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  Despite innovative medications and devices, heart failure (HF) continues to be the leading cause for admission to hospitals in the United States in patients older than 65 years. Many trials have succeeded in improving survival and many have failed. In this article, the authors briefly review the past, describe the present, and speculate about future HF trials.
• Unzek, S., Zhang, M., Mal, N., Mills, W. R., Laurita, K. R., & Penn, M. S. (2007). SDF-1 recruits cardiac stem cell-like cells that depolarize in vivo. Cell transplantation, 16(9), 879-86.
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  Prolongation or reestablishment of stem cell homing through the expression of SDF-1 in the myocardium has been shown to lead to homing of endothelial progenitor cells to the infarct zone with a subsequent increase in vascular density and cardiac function. While the increase in vascular density is important, there could clearly be other mechanisms involved. In a recent study we demonstrated that the infusion of mesenchymal stem cells (MSC) and MSC that were engineered to overexpress SDF-1 led to significant decreases in cardiac myocyte apoptosis and increases in vascular density and cardiac function compared to control. In that study there was no evidence of cardiac regeneration from either endogenous stem cells or the infused mesenchymal stem cells. In this study we performed further detailed immunohistochemistry on these tissues and demonstrate that the overexpression of SDF-1 in the newly infracted myocardium led to recruitment of small cardiac myosin-expressing cells that had proliferated within 2 weeks of acute MI. These cells did not differentiate into mature cardiac myocytes, at least by 5 weeks after acute MI. However, based on optical mapping studies, these cells appear capable of depolarizing. We observed greater optical action potential amplitude in the infarct border in those animals that received SDF-1 overexpressing MSC than observed in noninfarcted animals and those that received control MSC. Further immunohistochemistry revealed that these proliferated cardiac myosin-positive cells did not express connexin 43, but did express connexin 45. In summary, our study suggests that the prolongation of SDF-1 expression at the time of acute MI leads to the recruitment of endogenous cardiac myosin stem cells that may represent cardiac stem cells. These cells are capable of depolarizing and thus may contribute to increased contractile function even in the absence of maturation into a mature cardiac myocyte.
• Vasilyev, N., Williams, T., Brennan, M. L., Unzek, S., Zhou, X., Heinecke, J. W., Spitz, D. R., Topol, E. J., Hazen, S. L., & Penn, M. S. (2005). Myeloperoxidase-generated oxidants modulate left ventricular remodeling but not infarct size after myocardial infarction. Circulation, 112(18), 2812-20.
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  Inflammation after myocardial infarction (MI) heralds worse left ventricular (LV) function and clinical outcomes. However, whether inflammation affects LV function by extending myonecrosis and/or altering LV remodeling remains unknown. We hypothesized that cytotoxic aldehydes generated during oxidative stress may adversely affect remodeling and infarct size. One theoretical source of reactive aldehydes is oxidation of common alpha-amino acids by myeloperoxidase (MPO) released by leukocytes. However, a role for MPO in formation of aldehydes in vivo and the functional consequences of MPO-generated oxidants in ischemia/reperfusion models of MI have not been established.
• Askari, A., Unzek, S., Goldman, C. K., Ellis, S. G., Thomas, J. D., DiCorleto, P. E., Topol, E. J., & Penn, M. S. (2004). Cellular, but not direct, adenoviral delivery of vascular endothelial growth factor results in improved left ventricular function and neovascularization in dilated ischemic cardiomyopathy. Journal of the American College of Cardiology, 43(10), 1908-14.
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  We sought to compare the effects on angiogenesis and left ventricular (LV) function of adenoviral vascular endothelial growth factor-165 (AdVEGF-165) gene delivery by direct injection of AdVEGF-165 to the transplantation of skeletal myoblasts (SKMB) transfected with AdVEGF-165 in a rat model of ischemic cardiomyopathy.
• Askari, A. T., Unzek, S., Popovic, Z. B., Goldman, C. K., Forudi, F., Kiedrowski, M., Rovner, A., Ellis, S. G., Thomas, J. D., DiCorleto, P. E., Topol, E. J., & Penn, M. S. (2003). Effect of stromal-cell-derived factor 1 on stem-cell homing and tissue regeneration in ischaemic cardiomyopathy. Lancet (London, England), 362(9385), 697-703.
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  Myocardial regeneration via stem-cell mobilisation at the time of myocardial infarction is known to occur, although the mechanism for stem-cell homing to infarcted tissue subsequently and whether this approach can be used for treatment of ischaemic cardiomyopathy are unknown. We investigated these issues in a Lewis rat model (ligation of the left anterior descending artery) of ischaemic cardiomyopathy.