Vascular Disorders

Final post on the cardiovascular system for this unit! (Is it just me, or did that go by quickly?) In this post I will mainly be focusing on hypertension (a.k.a. high blood pressure), with a tiny little bit at the end on a couple of venous disorders (thrombophlebitis and phlebothrombosis).

Hypertension

Hypertension is, simply put, high blood pressure. Normal blood pressure is around 120/80 mmHg, with a mean arterial pressure somewhere around 95mmHg. (For a bit more information on the terminology, see my earlier post on blood pressure.) This isn't a fixed value- it's pretty normal to have blood pressure slightly higher or lower than these values. If your blood pressure is much higher or lower, however, then you might have some issues.

Another thing we need to take into account is that blood pressure does fluctuate over the course of a day and in response to various stimuli. Increasing or decreasing the blood volume will increase or decrease the blood pressure, respectively. Constriction or relaxation of the arteries (i.e. vasoconstriction/vasodilation), which in turn might be due to the action of the sympathetic nervous system, RAAS system or otherwise, can also increase or decrease blood pressure.

Classifications

Hypertension is generally defined as a blood pressure above 140/90. It can also be further broken down into mild, moderate or severe hypertension (severe being >=180/110), but it's not too important to remember the cutoff values for now (to my understanding they're pretty much just a guide anyway). Hypertension can be further divided into primary/essential/idiopathic hypertension, which has no identifiable cause, and secondary hypertension, which is secondary to some other disorder or condition (pregnancy, renal disorders, endocrine disorders etc.).

Pathophysiology

In primary/essential hypertension, there is arteriolar vasoconstriction for some unknown reason. This causes an increase in peripheral resistance, which increases blood pressure. At the same time, renal blood flow is reduced, causing increased activation of the RAAS pathway and thus an increase in blood pressure. A vicious cycle!

The high blood pressure itself can have damaging effects on the arteries. It can damage the arterial wall, leading to an increased risk of atherosclerosis (see my earlier post on Coronary Artery Disease for more information on atherosclerosis). In addition to this, arteries can harden (become sclerotic) and narrow, and the arterial walls can weaken. Weak arterial walls can lead to aneurysms (bulging out of the arterial wall), which can eventually lead to rupture and haemorrhage. Excessive vasoconstriction or atherosclerosis formation can lead to a loss of blood flow to the organs, which can in turn lead to further complications.

Risk factors

Risk factors for hypertension are pretty similar to risk factors for other diseases discussed so far. Once again, age, gender (again males are more susceptible) and genetics are uncontrollable factors. In addition to these, certain ethnicities may be at greater risk. Controllable risk factors for hypertension include obesity, salt intake, physical inactivity, stress, smoking, alcohol consumption and certain drugs (notably corticosteroids and oral contraceptives).

Diagnosis

Hypertension is usually asymptomatic, which is why it's often known as "the silent killer." It can be detected by measuring blood pressure, which is why having your blood pressure tested every so often can be important.

Treatment

Unfortunately, there is no cure for primary hypertension, and so controlling your blood pressure is a life-long process. Most people with hypertension should aim to keep their blood pressure below 140/90, but if they have diabetes as well (another "enemy to the blood vessels," as my prof says), they should aim to keep their blood pressure below 130/80.

Just like other cardiovascular diseases, treatment involves a mix of drug and non-drug therapies, as well as treating any complications that may arise. (Treating the cause probably also comes into it as well in the case of secondary hypertension.) Drug treatments involve diuretics, sympatholytics (i.e. blockers of various aspects of the sympathetic nervous system, such as β-blockers), calcium channel blockers, inhibitors of the RAAS pathway and vasodilators. Non-drug treatments include dietary changes such as reducing salt intake and ensuring adequate potassium, calcium and magnesium, as well as other lifestyle modifications such as stress management techniques and regular exercise.

Unfortunately, despite our best efforts, some people do not respond very well to treatment. This is known as resistant hypertension, and is defined as persistently elevated blood pressure despite treatment. This is more likely to happen in older people, obese people and people with other contributing factors such as renal disease. In these cases, patients may be on multiple drugs to try and keep their blood pressure under control.

If hypertension is not controlled, organs can be damaged, leading to kidney failure, blindness and so on. Severe hypertension with end organ damage is called malignant hypertension. This is a medical emergency!

Thromboembolic Disease

Now for a last little bit about a couple of issues affecting the veins: thrombophlebitis and phlebothrombosis. They're not quite the same thing, though they are unfortunately pretty easy to mix up.

First things first: thrombophlebitis ends with -itis. If you're sharp, you've probably already figured that this condition involves inflammation- and you're right! Thrombophlebitis is inflammation followed by thrombus formation, and is more common in superficial veins.

Phlebothrombosis is a bit different. It also involves a thrombus, but no inflammation is involved- rather, the thrombus appears to form spontaneously (and you might not even know about it until it starts giving you problems). It is more common in deep veins. A classic example of this is DVT (deep vein thrombosis), the constant threat of long-haul air passengers (*cough*15hrflightbetweenHongKongandToronto*cough*).

There are similarities in the pathogenesis of thrombophlebitis and phlebothrombosis. There are three main factors, known as "Virchow's triad." These factors are slow blood flow (stasis), endothelial injury and hypercoagulability, which can all lead to thrombus formation. If not treated, there might be complications: parts of a thrombus can break off, becoming an embolus, and get lodged somewhere else. A common place for thrombi to become lodged is in the lungs. Make sure to do yo' in-flight exercises, kids!

Oh right, I just said "if not treated" without even saying what the treatments are! Well, prevention is better than cure, so once again, moving around can help, as can special stockings. Otherwise, anticoagulants such as heparin can help, and in more extreme cases, a surgical procedure called a thrombectomy might be required.

That's this topic done! Fingers crossed for the topic test on Thursday now...