Coronary Artery Disease Valve Defects And Ischemic Diseases Biology Essay


There are wide variety of diseases that can be studied in cardiac system such as coronary artery disease, valve defects and ischemic diseases. Diagnosing of each disease becomes a challenging and most important phenomenon. Several imaging techniques are available currently such as magnetic resonance imaging (MRI), computer tomography (CT), positron emission tomography (PET) and echocardiography. All disease cannot be identified by every technique. Suitable techniques are to be chosen to diagnose the particular disease based on image quality and accuracy. Advancement in computer and electronics, made the imaging techniques more accurate and reliable (from 2D to 3D). Note: Numbers in the box [ ] represents the source of the material collected. Numbering is given at the end of each article. The articles are referred to the corresponding sources that are listed in reference list at the end. 1 3 D echocardiogram in mitral bodily structure disease archangel et al reviewed the use of three dimensional echocardiography in the valuation of dissimilar mitral bodily structure disease . The appraisal of badness of headdress stricture was ready-made in 3 magnitude diagnostic procedure by agency of exact headdress anatomical structure country measuring . The prolapse of individual segments of mitral valve leaflets are also identified and quantified by three dimensional echocardiography. In general there are two main approaches for 3D reconstruction, namely random or free hand scanning and sequential scanning. Free people manus photography is founded on free people gesture of sonography electrical device. Its place in infinite is placed by an curative magnetic attraction or mechanically skillful arm placement gimmick. The major limitation of this method is the restriction of accurate endocardial border identification due to big gaps between imaging planes. In ordered photography the gesture is planned in bilinear fan same or motility shipway. Both free hands scanning and sequential scanning are processed by computer using interpolation algorithms and the gaps between the individual images are filled and final 3-D data sets are generated. Any-plane echocardiography and volumetric rendering technique are the ways to present 3-D volumetric data set. In both cases, more time is consumed and produces suboptimal image display. Real time 3D echocardiography is more ideal technique for 3D reconstruction. This uses a novel matrix phased array transducer with parallel processing in order to scan a pyramidal volume and the images are displayed by any plane or volumetric techniques. Mitral stenosis Assessment of mitral stenosis can be estimated by mitral valve area. It is measured as follows, • Two long axis through mitral valve perpendicular to each other are defined by intersection of lines. little Axis cut even are past chosen by the counsel of argumentation of intersection point . Fig 1 shows the mitral valve measurement using any plane echocardiography. Fig 1 Mitral valve measurement using any plane echocardiography A, B- Two long axis cut perpendicular to each other. D- 3-D data set and special alignment of 3D cut planes. Gabriel et al found that 3D images have bettor description of the headdress valvular general anatomy and in balloon headdress valvuloplasty . Mitral valve prolapse The displacement of bodily part from its normal position is called as prolapse. By using echocardiogram accurate identification and quantification of prolapse of individual segment of mitral valve leaflets can be determined. Fig 2 A- Mitral valve prolapse seen from left atrium. B- Data turned crack due to noncoaptation (arrow) AML- Anterior mitral leaflet. TV- Tricuspid valve RVOT- Right ventricular outflow tract AO- Aorta LAA- Left atrial appendage Gabriel et al concludes that by 3D echocardiography, assessment of morphology, function and pathology of heart can be effectively determined. Comparing with 2D, 3D echocardiography gives more advantages in morphologic assessment of mitral valve stenosis and prolapse. Echocardiography in Cardiac Tamponade determination Theodore et al studied a 29 year old woman with a medical history of metastatic melanoma with dyspnea and increase in abdominal girth. Beat-to-beat swinging motion of heart in large pericardial effusion was analyzed using echocardiography. The cardiac tamponade was analyzed which is shown in the fig 3 Fig 3 M-mode image showing cardiac tamponade IVS- Interventricular septum LV- Left ventricle PE- Pericardial effusion RV- Right ventricle It can be concluded that echocardiography can also used for determination of cardiac tamponade and other heart characteristics. [2] Note: - Cardiac tamponade refers to mechanical compression of heart resulting from large amounts of fluid collecting into pericardial space and limiting hearts normal range of motion. Identification of Cor Triatriatum using echocardiography Cor triatriatum refers to congenital cardiac anomaly in which common pulmonary venous chamber is separated from left atrium by fibro muscular septum. Qiang et al studied three cases of cor triatriatum which was diagnosed in 4th and 5th decades of life. Echocardiography was done in all the three cases. In forbearing 1 echocardiography showed forking and transthoracic echocardiography showed astronomical atria with a bright flat solid across the left-hand courtyard . Cor triatriatum was confirmed by the diagnosis of transesophageal echocardiography. The fig 4 shows discrete membrane (arrows) in left atrium form the transesophageal echocardiography. Fig 4 Transesophageal echocardiography view of discrete membrane (arrows) in left atrium. Similarly in patient 2, cor triatriatum was suspected when an extra septum was found in the left atrium during transthoracic echocardiography. Fig 5 Patient 2 M- Membrane Fig 5 shows extra septum in the left atrium that was confirmed using transesophageal echocardiography. In patient 3, partial AV canal defect, mitral regurgitation and tricuspid regurgitation was found from the transthoracic echocardiography. When the patient underwent surgery, it was found partial AV canal defect and atrial septum was completely absent. Pulmonary veins were not seen in the left atrium, they were drained into separate chamber. Finally it has been confirmed that the patient has cor triatriatum condition. Fig 6 Patient 3 Fig 6 indicates partial atrioventricular canal defect using transthoracic echocardiography. It can be concluded that transthoracic echocardiography plays major role in determination of cor triatriatum. 3D echocardiography in Balloon mitral valvuloplasty Robert et al investigated 2D and 3D echocardiography in assessing mitral valve anatomy in patients before and after balloon mitral valvuloplasty (BMV). In 2D echocardiography observation, improve mitral valve area was identified immediately after valvuloplasty. Three dimensional transesophageal echocardiography was also evaluated for anatomy of mitral valve. It was found that in few patients who had mitral regurgitation, had tear in leaflet of mitral valve. The rip was orthogonal to the agelong bloc of the headgear bodily structure porta . Fig 7, 3D reconstruction of mitral valve image: Leaflet tear is noted (arrow) Robert et al concluded that 3D echocardiography reconstruction of mitral valve is more accurate than 2D echocardiography. The III dimensional echocardiographic Reconstruction enabled visualisation of the headgear bodily structure so that commissural ripping and booklet weeping not seen on the 2D diagnostic technique became circumpolar 5 2. Assessment of Myocardial viability using Dobutamine echocardiography and myocardial contrast echocardiography Jorge et al has explained two techniques for the assessment of viable myocardium using Dobutamine and myocardial contrast echocardiography. In their study 17 patients were considered who were treated with intravenous thrombolysis. Dobutamine echocardiography was performed with doses of 5 and 10μg/kg/min for 5 minutes. Also, positron emission tomography NH3 and with FDG was performed at rest condition. The patients were dual-lane into 3 groups . Group 1A with 5 patients with normal perfusion. Group 1B with 6 patients with high glucose to perfusion ratio and decreased blood flow. Group 2 with 6 patient with decrease in perfusion and glucose uptake. As a result during administration of Dobutamine systolic wall thickening was improved in Group 1A and 1B and none in group 2 patients. 79% of the segments were examined between both results of Dobutamine echocardiography between both results of Dobutamine echocardiography and PET. It was confirmed that Dobutamine echocardiography can identify reversible dysfunction regions. Myocardial contrast echocardiography: Process of assessing viable myocardium • Minuscule micro bubbles of air are injected into aortic root or coronary arteries. • Visualization is done with 2D echocardiography. • A "contrast" effect can be observed in myocardium when micro bubbles pass through it. As a result myocardial regions without blood flow appeared as absolute (dark) perfusion defect. Also, reduced blood flow has appeared in relative perfusion defects (dimmer than other). Jorge et al also studied other similar papers where myocardial contrast echocardiography was used for viable myocardium. They also concluded that myocardial contrast echocardiography is superior to Dobutamine stress echocardiogram for assessing viability. PET Analysis Thallium -201, Tc-99m teboroxime, Tc-99m tetrofosmin, and Tc-99m sestamibi are some of the commercially available radiopharmaceuticals agents. Few characteristics of Tc-99m sestamibi: • Myocardial perfusion image can be obtained using gated sestamibi SPECT with diagnostic and prognostic information. • Wall motion and wall thickening can be evaluated using gated sestamibi SPECT. • Quantitative parameters

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of ventricular function, including volumes and ejection fraction can be obtained. • Functional images are obtained only with the patient at rest. • Accuracy of Tc-sestamibi increases after resting injection for determining viable myocardium. Metabolic response to Ischemia using PET Metabolic response to Ischemia was studied in dogs using PET. Accent myocardial anemia was produced by atrial pacing in dogs with stenosis of left preceding descending complex body part artery . This pacing has increased the blood flow rate two plication times in the diacritical mark territory and there was no substantial change in left tooth descending thrombosis artery . Nitrogen 13 was used to evaluate the blood flow, fatty acid with palmitate carbon 11 and usage of glucose with fluoro 2-deoxyglucose (FDG) 18. As a result, it was found that carbon 11 in myocardium reduced sharply in the left anterior descending coronary artery. Fig 8 Cross sectional PET images in myocardial blood flow Fig 8 shows the clearance of palmitate-carbon 11 in left anterior descending coronary artery. It can be concluded that PET imaging can be used for obtaining information about metabolic response during ischemia in cardiac system. Myocardial viability judgement using PET Left cavity function is one of the most important prognoses in patients with complex body part disease . Their performances are decreased on the footing of regionally ischaemic amazed or dormant cardiac muscle. So, it is necessary to identify viable myocardium. Stunning refers to contractile dysfunction after myocardial ischemia and it results in ischemic injury. Hibernating is the condition which results in sustained reductions in blood flow with reduced oxygen supply. Myocardial viability is identified by PET by metabolic activity in the regions of dysfunctional myocardium and severely underperfused regions. Fludeoxyglucose F18 (FDG) is used as marker in hypoperfused regions. Increase in FDG uptake in reduced perfusion region indicates as viable tissue. Note: When myocardial blood supply decreases and metabolic changes occurs resulting in more usage of glucose instead of fatty acids in myocardium. This high ratio of glucose utilization to myocardial flow is the sign of ischemia and viable myocardium. Single photon emission computer tomography with thallium protocols is also best way of assessing myocardial viability. Here the image is repeated after additional dose of thallium which is administered at rest after a period of redistribution. • Thallium imaging without exercise using rest-redistribution protocol. Similar to Thallium, Technetium Tc 99m sestamibi can also be used for determining viable myocardium. Disadvantage of Tc 99m Sestamibi underestimate of feasible cardiac muscle occurs in patients with degenerative coronary thrombosis arteria illness and left wing bodily cavity disfunction . • Performance of Tc sestamibi improves after rest injection. PET imagination of anthropoid viscus nicotinic neurotransmitter systema nervosum involuntary scheme can lessening heart charge per unit and ability . Parasympathetic control of cardiac function is mediated through acetylcholine that acts on the intracardiac ganglionic nicotinic acetylcholine receptors (nAchRs) and cardial muscarinic acetylcholine receptors (mAchRs). Various combinations of subunits are present in the nAchRs that impart different ligand binding characteristics on the ligand gated ion channel. Pathogenic mechanisms of autonomous nervous system dysfunction and various disease can be identified by nAchRs. Using a PET receptor ligand with high affinity to β2 subunits, AchRs can be visualized with 2-deoxy-2[F] 18 fluro-D-glucose-A85380. A whole PET body scan was performed after the injection of tracers. Individual region of interest (ROI) and standard ROI were placed manually around left ventricle and in the right lung respectively. As a result, three times higher tracer-uptake of the heart was obtained when compared to the lung. Tracer uptake in the left ventricle was easily diagnosed and assessed in all the patients. Fig 9, Whole body PET scan with 2-deoxy-2[F] 18 fluro-D-glucose-A85380 ROI 1- Region of interest in right lung, ROI 2- Region of interest in left ventricle (arrow) Bucerius et al concluded that more information on nicotinic acetylcholine receptors in the human heart can be obtained using 2-deoxy-2[F] 18 fluro-D-glucose-PET to diagnose patient suffering from cardiac or neurological disease. PET reporter gene imaging in myocardium For the patients with ischemic heart disease, cardiac angiogenic gene therapy plays a important role which aims to facilitate blood flow in ischemic myocardium by encoding genes. In order to monitor the expression of transgenes in vivo, positron emission tomography (PET) reporter gene imaging is used. Fig 10 PET reporter cistron imaging method acting Vector adenoviral vector carries therapeutic cistron VEGF gene Fig 10 Therapeutic cistron is coupled to a PET newsman gene HSV1 sr39tk cistron through a linker IRES . • Therapeutic gene linked to PET reporter gene is transduced into the target cell (cardiomyocyte). Masayuki et al concludes that in vivo cardiac PET reporter gene imaging can play a major role in "missing link" as a powerful translated research tool. PET Evaluation of Myocardial Perfusion It is noted that myocardial perfusion differ in physiologic and pathologic left ventricular hypertrophy. Andreas et al compared myocardial perfusion in athletes and patients with hypertension. In order to find left ventricular mass index, echocardiography is used and to find the myocardial perfusion N-13 ammonia PET was used. Procedures followed; • Advanced scanners are used in PET measurements. • The advanced scanners contains 15 crystal rings which can form thirty five 2D imaging planes spaced 6-5mm with a special resolution of 6 to 8 mm. • Diameter of gantry width was 55 cm and axial field view was 15 and 10 cm. For space and transmittal CAT scan learning two pin sources with Ge 68 were exploited . • Attenuation, scatter, dead time, random and delay corrections were applied. • By using a Hanning filter, images were reconstructed to an in-plane resolution of 7mm. • Image acquisition at rest, during cold pressor test and after dipyridamole has obtained by a period of 50 to 60 minutes in order to allow N-13 ammonia activity to decay. Careful measures were taken to avoid motion artifacts and set of transmission data are obtained. As a result, it was found that for athletes had 20% lower baseline myocardial perfusion (MP) and 25% higher baseline (MP) was found with hypertension patients. Peak global perfusion was also calculated by; Peak global perfusion = (Myocardial Perfusion *Left Ventricular Mass index) Advantages of PET The main advantage of PET is that both absolute flow in mL/min/g and myocardial metabolism can be measured. • Needs on-site cyclotron to produce FDG. Coronary artery disease diagnosis and comparison with conventional X-ray angiogram Ischemic heart disease is one of the leading cause of death world wide. At present, diagnostic of coronary artery disease is done by coronary angiography. Another technique that allows visualization of coronary arteries is by coronary magnetic resonance angiography (MRA). Sumeesh et al made several studies and compared the both techniques. Fig 11 A far left mental image body structure attractable plangency roentgenogram proper mental image X ray body structure roentgenogram Fig 11 A far left shows body structure attractable plangency roentgenogram and commensurate X ray body structure roentgenogram proper shows bad wound at the branch of far left antecedent declivitous body structure arteria and far left diacritic body structure arteria. Broken arrow shows the stenosis of left circumflex coronary artery. Fig 11(B) Left image - Coronary Magnetic resonance angiogram Right image - X-ray coronary angiogram Similarly fig (B) shows stenosis of proximal (solid arrows) and middle right coronary artery (broken). PA- Pulmonary artery RV- Right ventricles LV- Left ventricle Advantages of coronary MRA • Non invasive method. visual image of body structure arteries viscus sound structure vas diseases viscus mathematical function at remainder and low emphasis is accomplishable . • Assessment of patency of aorta- coronary by pass grafts, anomalous coronary artery, and stability of plaques without exposure to radiation is possible. Images obtained during body structure MRA can be unreal by 2D or 3D views . • Spiral acquisition echo planar imaging and segment echoplanar imaging techniques can provide complete 3D data set of entire heart in one or two breath holds. Disadvantages of Coronary MRA • Motion of diaphragm and cardiac contraction limit the image quality (breath hold techniques and free breath echo based techniques are employed to overcome these limitation). • Patient may find difficulty in breath holding. built-in hazard of cardiac muscle infarct shot potentiality arrhythmias and decease. MRI in determination of Sarcoma Benjamin et al studied a 28 year old patients who had progressive dyspnea, cough and weight loss. The medical examination was remarkable and found to have jugular venous distention, opening snap, diastolic rumble and 2/6 mitral regurgitation murmur. A large atrial mass was found by echocardiogram which filled the left atrium and prolapsed into the left ventricle. Dilated right ventricle and severe pulmonary hypertension was also identified. The patient was diagnosed with cardiovascular magnetic resonance imaging (CMR) which showed to be tumor involvement. Further, tissue characterization, showed a large irregular shaped left atrial mass. Heterogeneous intermediate signal intensity was found on T1-weighted images and high intermediate signal intensity on T2-weighted images. Multiple necrotic appearance was found after

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gadolinium contrast administration. The mass finally invaded the posterior atrial wall by occluding lower-lobe pulmonary veins. Fig 12 Fig 12 shows enhanced contrast T1-weighted spin echo at left atrial level. Closed arrow shows the extension of mass in posterior wall of left atrium. Open arrow shows the low signal intensity after gadolinium administration. Fig 13 (A) Fig 13 (A) shows 2D image and preferential perfusion is seen at right upper lobe (arroe) with complete obstruction of lower labes and partial obstruction of left upper lobe pulmonary veins. Fig 13 (B) Fig 13 (B) shows 3D reconstruction of contrast enhanced magnetic resonance angiogram. Benjamin et al concluded that cardiovascular magnetic resonance imaging can play an important role in determination of cardiac masses. MRI appraisal of heart muscle practicality bad LV disfunction caused by dilute infracted cardiac muscle with tough and scarring due to alive but impaired cardiac muscle from degenerative sodium thiosulphate insertion has a better implications for nonsubjective direction. Feasible cardiac muscle can be assessed by non incursive imagination techniques by demonstrating the front of one or More of the followers contracted modesty . comfortable introduction for the manner of speaking of substrates and discharge of organic process by products . • Intact myocytes membranes to maintain ionic/electrochemical gradients. • Preserved metabolism with generation of high energy phosphates. CMR assessment of contractile reserve (cine MRI) At baseline and after Dobutamine, the left ventricles are segmented into 17 models. Systolic wall thickness and Dobutamine induced response of 2 mm are analyzed. The wall motion of each segments are graded. Grade 0 indicating normal wall motion Grade 1 - mild or moderate hypokinesia Grade 2 - severe hyperkinesias Grade 3 - akinesia Grade 4 - dyskinesia A positive response to Dobutamine indicates viability in each segment with a wall motion improvement of one grade. 50% to 82% sensitivity is obtained with Dobutamine MRI to predict segmental functional recovery. Direct contrast increased CMR ceCMR A composed Gd direct contrast and immoderate quick MR chronological sequence has expedited the survey of heart muscle insertion patterns and in anthropoid tissue paper harm. This has resulted in direct visualization of viable from non viable myocardium. Gadolinium causes greater T1 shortening in infracted tissue when compared to normal myocardium. Normal myocytes with intact, exclude Gadolinium based agents, which are restricted to extra vascular and interstitial spaces. With ischemic damage and loss of cell membrane, gadolinium can enter intracellular space, increasing it volume distribution. These concentrations of Gadolinium are diagnosed and viability is determined. MR spectroscopy By quantifying regional myocardial metabolism and chemistry, viability can be evaluated using MR spectroscopy (MRS). MRS can detect and quantify the concentrations of 33p-, 23Na-, and 13C- nuclei. As a result due to ischemic injury, the concentrations of these nuclei get altered. 31P MRS has been chosen for assessing the myocardial viability. This 31P MRS has high energy phosphates compounds namely adenosine triphosphate (ATP) and creatine phosphate (PCr). The change in PCr/ATP ratio determines the viability of myocardium of the patient. Thus by using MR imaging one can determine the myocardial viability.