#11: Hypertension: The Silent Killer

#11: Hypertension: The Silent Killer


They call it “The Silent Killer.”

That’s because most people feel nothing, even when the condition is relatively severe. Many people don’t even know they have it. But left untreated, this monster can cause untold damage to tissues and organs all over the body –particularly the heart, kidneys, and brain.
Those are important. I’m talking about hypertension, or high blood pressure. Without treatment, it can be devastating. But when diagnosed and treated properly, it can be well-controlled and compatible with a long, vigorous, productive life. Hypertension may be silent and sneaky, but it’s not at all unmanageable. The first step is to know our enemy. (Super Fancy Music) Hi, I’m Jonathon Sullivan, and welcome back to Greysteel. Your circulatory system is really just a pump and some pipes that, well, circulate your blood throughout your body. The circulation of the blood allows you to oxygenate the blood and fill it with nutrients and hormones and other yummy stuff, deliver that yummy stuff to your tissues, pick up the carbon dioxide and reaction products and other “exhaust” generated by your cellular engines, and deliver all that gunk to waste disposal areas –particularly your lungs for the CO2 and your kidneys for other stuff. The pump is obviously the heart, and as most of us have known since we were, like, 5, the pipes are the arteries, veins, and capillaries. And like any system of pump and pipes, our circulatory system has a bunch of pressure gradients to make the blood go round and round. The pressure on the lung side, called the pulmonary circulation, is pretty low, and we won’t talk about that much today. The other side of our circulation is the systemic circulation, basically everything else. But sometimes, the pressure in the arterial tree can get too high, and that’s not good. That’s hypertension. The most basic definition of hypertension is blood pressure that’s high enough to damage the heart, blood vessels, or other structures. But clinicians and academic bodies love numbers and definitions, and most clinicians will define hypertension as a sustained, resting systolic blood pressure of 140 mmHg or greater, or a resting diastolic blood pressure of 90 mmHg or greater. Remember that most people think of a resting blood pressure of 120/80 as being normal, although some authorities think even this level of blood pressure can
promote some degree of cardiovascular damage. Diagnosis depends on separate measurements at least a month apart with
good equipment under specific conditions. It’s not the kind of thing you can diagnose with one visit to the ER when you have an ankle sprain or in one of those blood pressure
measuring chairs at the drugstore. The most accurate approach seems to be 24-hour ambulatory blood pressure monitoring. Now, hypertension comes in multiple flavors. For example, there’s pulmonary hypertension, which is elevated blood pressure on the right-side, or in the pulmonary circulation. That’s not as common, and it’s kind of a different thing, so we’re not going to talk about it today.

We’re interested in the far more common arterial hypertension, and we can divide that into two types, primary and secondary hypertension.

Secondary hypertension is high blood pressure that’s caused by another identifiable pathology. For example, a tumor of the adrenal glands, called a pheochromocytoma,
can cause high blood pressure, among other problems. When the tumor is removed, the high blood pressure goes away. Thyroid disease, problems with kidney circulation, structural disease of the aorta –all can cause secondary hypertension. Primary hypertension, also called essential hypertension, is far, far more common. About 90-95% of cases of high blood pressure are primary in nature. Primary hypertension may afflict as many as 1 billion people worldwide, and probably affects about 35% of the population of North America. The risk goes up with increasing age, male sex, low socioeconomic status, obesity, diabetes, obstructive sleep apnea, and in
African-Americans and certain other ethnic groups. And here’s the real kicker: Up to 20% or more of those with the condition don’t even know they have it. And that’s bad. So what’s going on? What causes this? Well…. See, these small arteries and arterioles aren’t just passive pieces of biological PVC pipe that sit there while blood flows by. They’re active structures. Arterioles are the smallest branching level of arteries before the capillaries, and they have muscular walls that can relax and contract, causing the pressure inside them –and in the capillary bed–to go up or down. This gives your body a lot of control over the perfusion of various capillary beds, so that you can increase the circulation in some tissues and organs while decreasing it in others, as the situation demands. These muscular arterioles are regulated by input from the autonomic nervous system, which controls and integrates so much of your physiology, and also from various hormones. They also respond to local tissue concentrations of various chemicals like oxygen, carbon dioxide, nitrous oxide, and the acid concentration or pH. In essential hypertension, one or more underlying mechanisms causes sustained, abnormal, harmful constriction of the arterioles, increasing the blood pressure. These mechanisms include genetic factors, and there does seem to be a form of inheritance. But there doesn’t seem to be a single genetic variant that causes high blood pressure in most people, which leads many scientists to think that hypertension is multifactorial. Changes in the sympathetic nervous system seem to play a role in essential hypertension. This is the fight or flight side of the autonomic nervous system, which increases both arterial resistance and heart rate and cardiac output. Chronic stress can lead to over-activation of the sympathetic system and help promote high blood pressure, and there may be a genetic component making some people and populations more susceptible to this kind of sympathetic over-activation. Some authors have suggested that an imbalance between dietary sodium and dietary potassium may play a role in the development of essential hypertension, by causing excessive contraction of the arteriolar walls. This is an ongoing area of investigation, but it’s a good reminder to eat your fruits and vegetables and maybe show a little bit of restraint with the salt shaker. Finally, dysfunction of the renin-angiotensin-aldosterone system appears to be very important. This is a complex hormonal system responsible for helping us maintain fluid balance, and blood pressure, but it can get out of whack. When it does, it produces inappropriate amounts of aldosterone and angiotensin. Angiotensin tells blood vessels to contract more, increasing blood pressure, and aldosterone causes us to hang on to fluid and salt, thereby increasing the
volume of blood in the blood vessels and further increasing our blood pressure, not to mention contributing to
other nasty effects like edema or swelling. The ultimate consequence is a level of pressure inside the arteries, arterioles and capillaries that pounds at you with every heartbeat. High blood pressure, if untreated, damages the endothelium, or the delicate lining of blood vessels, leading to atherosclerosis, which in turn puts us at risk for heart attack, stroke, and many other horrible complications. The heart, which has to push against this elevated blood pressure, beat after beat, day after day, year after year, will eventually begin to change in structure and function, and will eventually not be able to keep up –that’s heart failure, and it’s every bit as bad as it sounds. Damage to the small vessels of the brain promotes various kinds of stroke and neurodegeneration. Damage to small vessels of the retina leads to hypertensive retinopathy and possible visual loss. The constant pounding of the capillary beds and fine structures of the kidney leads to hypertensive nephropathy, or kidney disease. This is particularly bad news, because the kidney is closely integrated with the renin-angiotensin-aldosterone system that we spoke of earlier and so it plays a central critical role in the regulation of blood pressure and blood volume. Kidney disease promotes high blood pressure and high blood pressure, worsens kidney disease. This vicious cycle culminates in end stage renal disease and dialysis which is no fun. And while they are relatively uncommon, there are a few hypertension related catastrophes that we see in emergency medicine more often than we’d like, like hypertensive encephalopathy, in which high blood pressure causes coma and seizures, intracranial hemorrhage, or bleeding into the brain, and aortic dissection, which causes a massive tear and unzipping of the largest artery in your body. We hate that. The bastard of it is that while most of this damage is going on, YOU FEEL NOTHING. High blood pressure pounds at capillary beds throughout your body, but aside from maybe some fatigue or an occasional bout of dizziness, you’re asymptomatic. This is why it’s so important for you, the athlete of aging, to get regular checkups and make sure
this monster isn’t sneaking up on you. That’s because mild hypertension or, better yet, a prehypertensive state, can often be treated very effectively with lifestyle modifications alone–diet, exercise, stress reduction, and so on. The effect of these interventions on hypertension in particular will vary from person to person, as they vary from study to study, but the effect of these lifestyle modifications on your health in general will be nothing but positive. And even if you turn out to have full-blown high blood pressure requiring medical intervention, the addition of a carefully selected antihypertensive agent to these lifestyle modifications can be lifesaving, and enable you to get on with a happy, healthy, active life. We’ll talk more about these very important, very commonly used medicines in our next episode. I hope you’ll join us then. Thanks for watching this episode of Greysteel. Our content is offered for ejumacational and infotainment purposes only, and will never be provided as medical advice for any particular person, patient, disease or condition. When it comes to your health, you should work closely with your physician. A reminder that our new book “The Barbell Prescription” is now out on Kindle and it’s a very beautiful, very functional adaptation of the book.
Check it out at amazon.com. You can buy the paperback at TheBarbellPrescription.com. I’d like to thank my friends and colleagues, Doctors Austin Baraki and Phil Lewalski,
for their helpful comments on this episode. This episode is brought to you in part by our patrons at Patreon. If you’d like to join them and help us make more of these videos, just go to Patreon.com/greysteel. Or if you just want just want to make sure you don’t miss out on any more free content on healthy aging, go to YouTube.com/greysteel and subscribe to our channel. That really helps us out a lot. Until next time, stay strong, and stay healthy.