Cardiovascular Pathology|| Primary and Secondary Hypertension, and the Causes of Hypertension

Hypertension, when diagnosed should be done using two parameters which are the systolic pressure (pressure when the ventricle is contracted) and the Diastolic pressure (when the ventricles are relaxed). With this, there is the normal blood pressure which is less than 120 in the diastolic and less than 80 in the systolic, making it <120/80. When the person has a diastolic blood pressure of 120 to 129, and a systolic pressure of 80 to 89, then the person has elevated blood pressure. When the blood pressure is 130 to 139 diastolic and over 80 to 89 systolic, then it is regarded as Stage 1 hypertension. When the patient has a diastolic pressure greater than 140, and greater than 90, then it is a Stage 2 hypertension. Patients can also have isolated blood pressure where one of the parameters is normal and the other is increased. For instance, the diastolic blood pressure is increased but the systolic blood pressure remains normal. In an isolated systolic blood pressure, the systolic blood pressure increases but the diastolic blood pressure remains the same. This is confirmed after an average of two readings in two visits.^{ncbi , sciencedirect, heart.org}

Patients can have White coat hypertension, which is hypertension that occurs only when patients are at work and not at home, and this hypertension requires a 24-hour ambulatory blood pressure monitoring which will allow for the identification of the pressure of the blood all round the day to rule out all forms of white coat hypertension. Masked hypertension is the opposite of white coat hypertension where the person has high blood pressure outside work but normal blood pressure during work time. ^ahajournals

Hypertension can be caused by several things, and looking at cases such as primary or Essential hypertension which is the most common type of hypertension accounting for about 95% of all hypertensive cases, common within people of age range 25 and 55 years and people with a family history are at risk of having this hypertension. This hypertension can be caused as a result of increased sympathetic nervous system activity such as an increase in norepinephrine, and epinephrine acting on beta receptors which increases the heart rate.

Remember that cardiac output = heart rate X stroke volume

This means that when there is an increase in heart rate, there will be an increase in cardiac output, and when cardiac output increases, blood pressure increases. The Norepinephrine and epinephrine also bind with alpha-1 receptors, binding with the myocardial of the contractile cells causing them to vaso-constrict, increasing the resistance to the blood flow, and increasing blood pressure. With an increase in Norepinephrine and Epinephrine, renin secretion is possibly causing the production of Angiotensin 2 which increases blood pressure. Being Obese is a big factor, also having high sodium retention causes more water to get into the bloodstream increasing the intravascular blood volume, and increasing blood pressure. One cause is an increase in age, which would cause less elastin present in the blood vessel, and an increase in collagen in the vessel increasing the total peripheral resistance of the blood vessel.^{ahajournals, ncbi, ncbi 2, ncbi 3, ccforum, ncbi 4}

While there is primary hypertension, there can be secondary hypertension causes and this account for about 5% of the types of hypertension. Renal disease or causes such as Renal Vascular issues such as fibromuscular dysplasia, and renal artery stenosis. These conditions prevent blood from getting into the kidneys as a result of plaque blocking the perfusion into the kidneys. It can also be a result of the narrowing of the vessels of the kidney reducing renal blood flow which will cause the release of Renin which will lead to the formation of angiotensin 2 which will then increase blood pressure. Patients with diseases of kidney tissues such as renal parenchyma (diabetic nephropathy, and polycystic kidney disease) can also have hypertension as a result of a reduction in the glomerular filtration rate of the kidney tubules, and this causes an increase in renin production which then increases blood pressure through angiotensin 2.^{msdmanuals, ncbi, aafp}

Angiotensin 2 binds to receptors in the vessels causing the vessel to vaso-constricts. When blood vessels vaso-constricts, they reduce the flow of blood through them increasing resistance and pressure. Also, it causes the adrenal gland to release Aldosterone which allows the kidney to increase sodium retention which will increase the blood volume and increased blood pressure. Also, it allows the posterior pituitary gland to secrete Antidiuretic Hormone [ADH] allowing the reabsorption of water into the bloodstream.^{ncbi, msdmanuals}

There can be drug-related causes of hypertension such as sympathomimetics works to increase the sympathetic nervous system activities such as an increase in heart rate, contractility of the heart, stroke volume, and blood pressure which could lead to secondary hypertension.^{ncbi 1, ncbi 2} Another cause of hypertension can be oral contraceptives which contain estrogen. Estrogen increases the production of angiotensinogen which will then become angiotensin 1 which will then become angiotensin 2 which increases the blood pressure of the person. ^{pubmed, msdmanuals} NSAIDs which inhibits cyclooxygenase COX-2, prevents cyclooxygenase from forming prostacyclin which will prevent the dilation of afferent arterials causing it to constrict which will allow for the retaining of sodium and water which would increase the blood pressure and cause hypertension.^ncbi

Hypertension can also be a result of endocrine causes. Remember I mention that Aldosterone which is of the adrenal gland will increase blood pressure, and Cortisol, norepinephrine, and epinephrine can also lead to hypertension. Hormones like aldosterone will increase the re-intake of sodium and allow for more potassium to be excreted causing high blood pressure. Hyperthyroidism can cause hypertension by increasing the beta receptor activities in the heart excessively such as increased heart rate, which increases cardiac output, and blood pressure.^ncbi

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Image 1 || Wikimedia Commons || Pulmonary Hypertension