Comparison of Myocardial Infusion Technology with Caronary CT - Literature review Example

?Literature Review: Comparison of Myocardial Infusion Technology with Caronary CT Cardiovascular disorders are reported to be the leading life threatening disorder is the advanced countries.  Because of the wave of industrial enterprise and aging of natives, it is becoming more rampant. Further, boosts in its prevalence are expected.   An early diagnosis of coronary artery disease (CAD) is the most convoluted task of biological allieds. Nonetheless, various tests are valid, including MRA, ECHO, MPI (SPECT & PET), CTA (ranging from 4-slice CT to the 320-slice CT and dual source MCTA), but the selection of the “best test” is pivotal. The intention of this literature review is to study the uncertainty, advantages and disadvantages of coronary CT in comparability to magnetic imaging perfusion (MPI). Present-day researches indicated bulging in the ubiquity of diabetes from 200 million today to +300 million in 2025. Because of association in between CAD and diabetes, this may set up a serious dilemma worldwide. Furthermore, analyses indicate about 5-9% of people aged 20+ are suffering through CAD. The expiration proportion rises with age, and it is more common in males in parallel to females, but the expiration rates for men reduce promptly after age of 55. After aged 75 the death rate of women is higher than men, belonging to same age group.  It is assessed that +16 million Americans are suffering through CAD and 8 million of them had a myocardial infarction (increasing 1 Million per annum). Framingham trial forecasts about 50% & 30% of males and females respectively in the age 40+ population are suffering through CAD (Caronary Artery Disease website at ). The most convoluted part of CAD lies in its undetection, mostly CAD remains undetected until the moment of myocardial infarction or even death. It is an alarming situation for physicians; biomedical scientists and health allied to develop a mean to discover CAD in early stages, to get the best result and prevent diseases. Early detection of CAD allows a physician to reduce the potential risk factor associated with CAD. Because of severity in detection of CAD a thorough discussion of myocardial perfusion imaging (MPI) and coronary CT (CTA) is done. Bringing cutting edge information in order to facilitate the selection of the best one among MPI and CTA is the goal of review. MPI is thought about to be the most standardized, physiologically sound, and proved technology for cardiac imaging. It forms scintigraphy images based upon signal generated by radiotracers. MPI is capable of displaying local perfusion ventricular wall motion and exactly gauging left ventricular ejection fraction. Hacker et al. (2005, p. 1294) reported MPI is capable of acknowledging myocardial perfusion (MP) defects, and functional relevancy of coronary artery (CA) stenoses, along with kernel informations for a physician to take decisions. Further; normal MPI eradicates the necessity of intrusion in patients who are suffering through stable angina. However, MPI does not show promising results in case of cardiomyopathy and in the determination of atherosclerosis. Recently, CTA developed as a productive replica of invasive coronary angiography (CA). Attributes of CTA includes high exactness, and comparable excellent results of revascularization prognosis in comparison to CA. Budoff et al. (2008, p. 1724) and Mollet et al. (2005, p. 2318) reported CTA aptitude of exceptional diagnostic precision for CAD but unfortunately limited data are available in patients suffering from low to the intermediate pretest expectations of CAD. However, overvaluation of Ca plaque, artifacts because of heart dynamicity has limited positive predictive values (Meijboom et al. 2008, p. 2135) but its high negative predictive values have made CTA a beneficial method to exclude CAD. CTA has become a very useful modality for cardiac applications (Cademartiri et al. 2005, p. 16) in clinical practice because of its high spatial and temporal resolution that not only permits imaging of CA network but concurrent examination of other cardiac structures as well. Furthermore, the integration of CA calcium (CAC) and CTA has made it highly exact in the identification of atherosclerosis, precise risk stratification to choose lipid lowering target, besides gauging of ejection fraction and myocardial dynamicity (Orakzai et al. 2006, p. 555). Anatomical and functional imaging is the two modalities of cardiac imaging. CTA is principally concerned with the anatomical assessment of cardiovascular system (CVS) i.e. stenosis, whereas functional assessment, i.e. ischemia is executed by MPI (SPECT & PET). Therefore, selection of the best test is reliant on the clinical questions, since anatomical stenosis is unable to reliable prediction ischemia or hemodynamic significance and vice versa. PET and SPECT are the procedure of MPI from more than three decades; backed by firm verification revealing that detections are highly related to the presence of inducible ischemia (Gibbons 2008, p. 257). On the other hand, rise in the application of CTA is seen in clinical practices because of exceptionally high spatial and temporal resolution, along with the manifestation of sensitivity and specificity of 94% & 93% respectively (Leber et al. 2005, p. 147). Attenuation artifacts, cost, hazards of radiations are the inherited limitation of MPI, whereas the base of imaging on the anatomical features is the limitation of CTA in evaluation of patients with a high probability of CAD. Budoff et al. (2006) contrasted the accuracy of CTA and MPI in the prediction of CAD. Budoff et al. (2006) reported a sensitivity of 94%, specificity of 96%, PPV of 92% and NPV of 97% of CTA, which is considerably high in comparability with MPI sensitivity of 95%, specificity of 89%. Furthermore, CTA executed excellent vessel analysis with sensitivity and specificity of 94% and 96% correspondingly. The anatomic gold norm prefers an anatomic test such as CTA. This study contrasted on the adequately founded tools for the detection of myocardial ischemia such as MPI with a procedure that furnishes anatomical data of the epicardial CA. No issue how precise CTA is contrasted to angiography. The two things of facts acquired with these fundamentally distinctive techniques are hard to compare. Both catheter angiography and CT angiography evaluate only anatomical oddities, while MPI looks at perfusion to the myocardium. However, since revascularization is based upon angiography displaying an obstructive injury, this restriction is widely accepted and a nuclear test exhibiting a perfusion defect in the absence of significant obstruction is considered a false positive test. In 2004 meta-analysis (Underwood et al. 2004, p. 261) comparison analysis of sensitivity & specificity of MPI versus exercise echocardiography was carried out to examine CAD. This analysis, confirmed the high sensitivity of MPI-Spect for the identification of CAD for e.g stenosis. Due to high sensitivity, SPECT is serving as a gatekeeper for CA and is quickly diminishing the rate of invasive tests. Because of plenty of affirmations about its functional testing, it is immensely recognized technique for the diagnostic imaging of sufferers, which are suspected to be suffering through CAD, only in USA more than nine million MPI tests are performed per annum. Despite all firm support (while considering it as a first line test), MPI does have bunches of drawbacks. First of all, it exposed patient with the highest radiation dose. It is the most costly test; unable to identify atherosclerosis are just few of them. Furthermore, the spatial and temporal resolution of MPI-SPECT is lower in comparison to CTA. Therefore, visualization detail of MPI is not as good as CTA. Unusual growth is noticed in the field of cardiac imaging especially in CTA. CTA is capable of visualizing the CA lumen with exceptionally good exactness. The matter of cost related with MPI is vanquished by CTA, which furnishes an excellent not only NPV but PPV. Therefore, investigators inferred CTA could be utilized as trustworthy gauze before invasive angiography (Hendel et al. 2006, p. 1475).  CTA should be used as a principal gatekeeper when the likelihood of CAD is lower, and a secondary gatekeeper in patients with delicately positive MPI-SPECT prior to decide, whether to perform accepted coronary angiography in these patients because of its invasive nature. Patients are exposed to same level of radiation dose when examined through MPI and CTA (powered by dose modulation technique). Picano (2005, p. 3) reported radiation doses lies in the span of 6-8 mSv when technetium is used, but it can be high as 27 mSv in the case of thallium studies.  Generally, CTA, impart radiation dose in the span of 10-16 mSv during the examination of CAD. It is estimated that the radiation dose can be reduced by multiple folds via dose modulation. However, reduction in the radiation dose can be achieved by decreasing number of scanning, mA and scanning region of heart. Radiation dose of CTA can be lower as 0.95 mSv by applying SnapShot Cine Technology i.e 80% eradication in the radiation dose.  In this method x-ray tube is turned on to take limited data of small phase range than turning it off until the next addition. Despite of reducing radiation dose significantly, it is unable to measure the ejection fraction because of one phase scanning. Low dose CTA based on SnapShot Cine Technology is a useful tool for younger patients and children. Beyond any doubt, MPI-SPECT is the most common and widely accepted test for the prognosis of CAD in high pretest probability patients. Vasodilator is indicated in the patient who is suffering through the left bundle branch block, i.e. patients are not capable of exercise or obtain the target heart rate, as stated by Hendel et al. (2009, p. 561). As well, SPECT can be used to direct coronary intrusion because it is capable of recognizing any malfunction in any individual coronary arteries. Tremendous growth is noticed in MPI SPECT besides PET scanner because of CAD terrifying condition in developed countries. It is reported that the meticulousness of PET-Scanner is exceptionally superior to SPECT because of better spatial resolution, coincidence perception and accurate correction of attenuation. The sensitivity and specificity of PET-Scanner are found to be 89% and 90% respectively. CTA is recommended for those patients whose pretest probability lies in mid. Researchers found CTA to be equivalent to conventional CA. Chow et al. (2009, p. 135) examined 1,029 patients who suffered clinically reported cardiac CT. Among them, 482 (46.8%) patients had stress tests executed. CTA was asked to rule out CAD in 705 patients and/or to elucidate equivocal stress test results in 251 patients. A total of 543 (52.8%) CTA's showed irrelevant coronary stenosis and 37.7% were unusual. A total of 148 patients suffered both CTA and clinically indicated invasive CA. The commonness of obstructive CAD was 81%. CTA had excellent per-patient sensitivity (99%), PPV (92%), and NPV (95%) for CAD. Furthermore, contrast-enhanced CTA is capable of prognosing atherosclerosis (not feasible with MPI) and stenosis, but non contrast-enhanced CTA is incapable of stenosis prediction but atherosclerotics. It believes from the literature review on the comparison of MPI and CTA. CAD is the most life menacing disease worldwide. Due to alarming condition provoked by CAD tremendous advancement in the CAD imaging is seen and forecasted. CTA and MPI are the two widely accepted procedures for the diagnosis of CAD. The functional information originated from MPI is valuable and has no replica of it. On the other hand, the ability of CAD in the prediction of atherosclerosis and stenotic disease is incomparable with MPI because of its excellent resolution. MPI is excellent in the diagnosis of CAD when the pretest probability is higher and CTA where it is intermediate. Radiation dose of MPI is slightly lower than CTA but by using dose modulation technique it could be overcome i.e. both equal in the radiation dose. It is believed that CTA and MPI are not competative of one another but complimenter. Since precise diagnosis is crucial for the patient care. Therefore, b allied must evaluate patients clinically before screening about pretest probability of CAD and associated risks.  Merits and demerits as mentioned above can be utilized in the selection of the best test based upon patient factors, capability of CTA and MPI in the diagnosis of cardiovascular diseases. References 1. Hacker, M. Jakobs, T. Matthiesen, F, et al., (2005), "Comparison of spiral multidetector ct angiography and myocardial perfusion imaging in the noninvasive detection of functionally relevant coronary artery lesions: first clinical experiences", The Journal of Nuclear Medicine, vol. 46. 8, pp.1294-1300. 2. Budoff, M. Dowe, D. Jollis, J, et al., (2008), "Diagnostic performance of 64-multidetector row coronary computed tomographic angiography for evaluation of coronary artery stenosis in individuals without known coronary artery disease: results from the prospective multicenter ACCURACY (Assessment by Coronary Computed Tomographic Angiography of Individuals Undergoing Invasive Coronary Angiography) trial", Journal of the American College of Cardiology, vol. 52. 21, pp.1724 – 1732. 3. Mollet, N. Cademartiri, F. Van ieghemm, C, et al., (2005), "High-resolution spiral computed tomography coronary angiography in patients referred for diagnostic conventional coronary angiography", Circulation, vol. 112. 15, pp.2318-2323. 4. Meijboom, W. Meijs, M. Schuijf, J, et al., (2008), "Diagnostic accuracy of 64-slice computed tomography coronary angiography: a prospective, multicenter, multivendor study.", Journal of the American College of Cardiology, vol. 52. 25, pp.2315 - 2144. 5. Munther, K. Homoud, (2008), Coronary Artery Disease. Available from: Tufts, Open course ware:  http://ocw.tufts.edu/data/50/636849.pdf [Accessed: May 11, 2011] 6. Cademartiri, F. Runza, G. Belgrano, M, et al., (2005), "Introduction to coronary imaging with 64-slice computed tomography ", Radiol Med (Torino), vol. 110. 1-2, pp.16-41. 7. Orakzai, S. Orakzai, R. Nasir, K, et al., (2006), "Assessment of Cardiac Function Using Multidetector Row Computed Tomography ", Journal of Computer Assisted Tomography, vol. 30. 4, pp.555-563. 8. Gibbons, R, (2008), ".Noninvasive diagnosis and prognosis assessment in chronic coronary artery disease: Stress testing with and without imaging perspective", Circulation: Cardiovascular Imaging, vol. 1. , pp.257 - 269. 9. Leber, A. Knez, A. Von zilger, F, et al., (2005), "Quantification of obstructive and nonobstructive coronary lesions by 64-slice computed tomography: A comparative study with quantitative coronary angiography and intravascular ultrasound", Journal of the American College of Cardiology, vol. 46. , pp.147-154. 10. Budoff, M. Rasouli, M. Shavelle, M, et al., (2007), "Cardiac CT Angiography (CTA) and Nuclear Myocardial Perfusion Imaging (MPI)-A Comparison in Detecting Significant Coronary Artery Disease ", Acad Radiol, vol. 14. 3, pp.252-7 11. Underwood, S. Anagnostopoulos, C., et al., (2004), "Myocardial perfusion scintigraphy: the evidence", European Journal of Nuclear Medicine and Molecular Imaging, vol. 31. , pp.261 - 291. 12. Hendel, R. Patel, M. Kramer, C, et al., (2006), “ACCF/ACR/SCCT/SCMR/ASNC/NASCI/SCAI/SIR 2006 appropriateness criteria for cardiac computed tomography and cardiac magnetic resonance imaging: a report of the American College of Cardiology Foundation Quality Strategic Directions Committee Appropriateness Criteria Working Group,American College of Radiology, Society of Cardiovascular Computed Tomography, Society for Cardiovascular Magnetic Resonance,American Society of Nuclear Cardiology, North American Society for Cardiac Imaging, Society for Cardiovascular Angiography and Interventions, and Society of Interventional Radiology", Journal of the American College of Cardiology, vol. 48. , pp.1475–1497. 13. Hendel, R. Berman, D. Di carli , M, et al., (2009), "ACCF/ASNC/ACR/AHA/ASE/SCCT/SCMR/SNM 2009 appropriate use criteria for cardiac radionuclide imaging: A report of the American College of Cardiology Foundation Appropriate Use Criteria Task Force, the American Society of Nuclear Cardiology, the American College of Radiology, the American Heart Association, the American Society of Echocardiography, the Society of Cardiovascular Computed Tomography, the Society for Cardiovascular Magnetic Resonance, and the Society of Nuclear Medicine. ", Circulation, vol. 119. , pp.e561-e587. 14. Picano, E, (2005), "Economic and biological costs of cardiac imaging", Cardiovascular Ultrasound, vol. 3. , pp.13 - 17. 15. Chow, B. Larose, E. Bilodeau, S, et al., (2009), "The ‘what, when, where, who and how?’ of cardiac computed tomography in 2009: Guidelines for the clinician.", The Canadian Journal of Cardiology, vol. 25. , pp.135 - 139. Read More