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Hypertension and Correlation to Cerebrovascular Change: A Brief Overview
Published in Ayman El-Baz, Jasjit S. Suri, Cardiovascular Imaging and Image Analysis, 2018
Heba Kandil, Dawn Sosnin, Ali Mahmoud, Ahmed Shalaby, Ahmed Soliman, Adel Elmaghraby, Jasjit S. Suri, Guruprasad Giridharan, Ayman El-Baz
Lab tests are also an important tool in making or supporting a diagnosis of hypertension. Tests that could be related to hypertension include the following: measurement of serum potassium and creatinine levels (or estimated glomerular filtration rate), which is an indication of how well the patient's kidneys are functioning; blood glucose and hematocrit; cholesterol profiles and triglycerides. An increase in serum calcium due to increased activity of the parathyroid glands can be associated with hypertension. Urine samples can be tested for albumin (microalbumin), a protein, and blood urea nitrogen (BUN). Hypertensive retinopathy, diagnosed by fundoscopic examination, is an ophthalmologic symptom of chronic hypertension or other cardiovascular diseases [5], [13]. Direct ophthalmoscopy, photography, and angiography can also reveal hypertensive choroidopathy and hypertensive optic neuropathy. A 12-lead electrocardiogram can detect signs of myocardial damage due to hypertension. An echocardiogram can be performed to identify conditions such as atherosclerosis, left ventricular hypertrophy, etc., which provide important information that may support the diagnosis of hypertension. The JNC 7 on High Blood Pressure lists high-sensitivity C-reactive protein (HS-CRP), homocysteine, and elevated heart rate as “emerging risk factors” [5].
Fractal Dimension of Retinal Vasculature
Published in Dinesh K. Kumar, Sridhar P. Arjunan, Behzad Aliahmad, Fractals, 2017
Dinesh K. Kumar, Sridhar P. Arjunan, Behzad Aliahmad
Fundus photography also allows for risk assessment of cardiovascular diseases and its subsequent complications. This includes hypertensive retinopathy which is referred to retina damage due to hypertension (high blood pressure). It is associated with long term risk of stroke [16,17] as the second commonest cause of death worldwide [18]. Some of the first observable signs are flame hemorrhages and cotton wool spots. As the disease progresses, hard exudates may appear around the macula along with swelling of the macula and the optic nerve resulting into vision impairment. Another, associated clinical biomarker is reduction in arteriolar diameter which is assessed by measuring the reduction in arteriolar diameter to venous diameter ratio (AVR) [19,20]. However, reduced AVR does not necessarily indicate constant venular diameter and therefore reflecting generalized arteriolar narrowing. Venular diameters may also change (usually increase) due to different pathologic conditions including atherosclerosis, inflammation, cholesterol levels and stroke event [21]. For instance, this ratio for the stroke incidence corresponds to both arteriolar narrowing and venular widening [5,22]. Therefore using AVR, the exact contribution of individual arteriolar and venular diameters to disease event may remain unknown. For more effective translation of retinopathy signs into clinical application and assessment purpose, hypertensive retinopathy, in a relatively new classification, is classified into four levels of none, mild, moderate and severe [23] based on the observable retinopathy signs. Generalized and focal arteriolar narrowing and arteriovenous nicking are referred to as mild hypertensive retinopathy signs. The presence of lesions such as microaneurysms and hemorrhages, hard and soft exudates (cotton wool spots) indicate the moderate level while optic disc edema is referred to as a sign for severe stage [23]. Example of retinal images with some retinopathy signs are shown in Fig. 8.2.
A new approach for retinal vessel differentiation using binary particle swarm optimization
Published in Computer Methods in Biomechanics and Biomedical Engineering: Imaging & Visualization, 2021
Samra Irshad, Xiaoxia Yin, Yanchun Zhang
Hypertensive Retinopathy (HR) is an ocular disorder that occurs due to the presence of arterial hypertension in the body. In the presence of arterial hypertension, the inner lining of arteries is damaged and as a result, they become thick and stiff (Knudtson et al. 2003). Particularly, the width of retinal arterioles (arteries) is decreased which affects the normal blood flow and this phenomenon is known as Generalised Arteriolar Narrowing (Ikram et al. 2004). The severity of this ‘decreased arteriolar width’ condition is assessed using a parameter known as Arteriovenous Ratio (AVR) (Stokoe and Turner 1966), i.e., the ratio of the width of arterioles to the width of the venules (veins). If this ratio is reduced from a normal value, then it is an indication of the presence of Hypertensive Retinopathy. The alteration in the normal patterns of retinal structures can be categorised into two groups; vascular and non-vascular abnormalities, and analysis of these pathological structures indicates the severity of hypertensive retinopathy. Generalised arteriolar narrowing is the earliest sign of Hypertensive Retinopathy (Scheie 1953) (Keith 1974) (Wong and Mitchell 2004), and as the disease progresses, other clinical signs begin to appear (e.g., retinal lesions). The disease progression makes the retinal vessels prone to many different kinds of pathologies, e.g. vessel tortuosity, hard and soft exudates, branch retinal artery and vein occlusion, sheathing of vessels, focal arteriolar narrowing and optic disk swelling, and all these retinal pathologies deteriorate the width and intensity of vessels. Moreover, hypertensive retinopathy progression has different effects on vein and artery; comparatively, arteries are observed to be more affected in presence of hypertensive retinopathy. Figure 1 shows some diseased exemplary retinal fundus images. In Figure 1(a), the development of new ‘ghost’ vessels and vessel fading can be observed. Figure 1(b) shows the retinal arteries that are hardly visible due to occlusion and sheathing of vessels with the appearance of cotton wool spots in the fundus area (e.g. the ones indicated by circle arrow). Branch retinal vein and artery occlusion are shown in Figure 1(c) and (d) which damages the vessel appearance. Figure 1(e) shows arteriosclerosis where the centre-line structure of the arterial segment has been altered.