Hypertension History: What We've Learned and Why Your Blood Pressure Matters
Hypertension is the medical term for high blood pressure. The management of hypertension has been probably the greatest medical success story of the twentieth century.
While the measurement of blood pressure dates back into the nineteenth century, clear evidence of what the blood pressure should be and how an elevated pressure could be treated dates to the latter half of the twentieth century. Blood pressure has always been expressed in millimeters of mercury (mm Hg). This measurement refers to the height that a column of mercury is elevated to produce the appearance and cessation of sounds as the blood is pumped through the system of arteries by pressure from the heart. Blood pressure is expressed in two numbers, the systolic or top number and the diastolic or bottom number. The systolic number is produced by the pulsation of blood forced through the arterial system by the contraction of the ventricle, or lower pumping chamber of the heart.
During a measurement, the cuff around the upper arm is inflated until it is clearly above the anticipated upper, or systolic, number, then it is slowly deflated while we listen for the sounds of the blood flow. The systolic, or first, number is produced when the force of the blood flow is greater than the pressure from the tightness of the air around the arm in the inflated cuff, and the pressure in the blood stream sends the blood spurting past the pressure from the cuff. This is the first sound heard as we are listening for with the stethoscope. The diastolic, or second, number is the disappearance of the sounds of the blood flow, indicating the baseline pressure in the arterial system as the pressure in the blood system drops below the lowest amount of pressure achieved by the pulsation of blood from the heart.
While many people have commented on the dramatic increase in longevity in the United States and other industrialized nations, a careful observation of the onset of this increase in the life span of Americans will trace back to the beginning of the treatment of elevated blood pressures in the early 1970s. It comes as quite a shock to many people, even those that work in medicine, when I tell them, prior to 1970, physicians did not treat hypertension unless the diastolic pressure was greater than 110 mmHg. Today that degree of elevation of the diastolic pressure would be considered an emergency elevation needing immediate treatment. Prior to 1970, blood pressure in the range of 170/98 was just noted and not treated. U.S. President Franklin Roosevelt died of a massive brain hemorrhage at the now relatively young age of 64, a problem rarely seen anymore today when his blood pressure would have been aggressively controlled.
I am always struck by the irony of the nearly perfect correlation of the "War on Hypertension" with my own medical career. The first article encouraging the treatment of elevated blood pressures lower than the diastolic pressure of 110 mmHg was published in September of 1970, the first month that I entered medical school. When I began to develop a research program in my faculty role in the 1980s, hypertension research became my initial and very successful focus for decades. I had the great opportunity to research hypertension, along with publishing many articles on it, and also to do educational lectures for other physicians throughout the United States.
After the publication of the original article in the autumn of 1970, national and even worldwide interest in detecting and treating blood pressure ensued, what I call the War on Hypertension. All medical facilities began to monitor blood pressure. There were mass screenings of blood pressure offered in a wide variety of non-medical settings, such as church meetings and community gatherings. There were even national television public service announcements encouraging people to take their blood pressure medication.
As this national effort began, there were two major questions: What numbers for blood pressure should be our targets for control, and what medication should we use to achieve these levels? Research addressing these two questions ran parallel through the next few decades.
Here in the United States, we focused our early research on treating patients with an elevation of the bottom number, or diastolic hypertension, even though many patients may have had elevation of their systolic blood pressure number also (mixed hypertension). In Europe, the research focused on both the systolic and diastolic numbers as treatment targets. Throughout the 1970s and 80s, a series of research projects around the world showed that lowering blood pressure with medication reduced a variety of stroke and heart related problems. Throughout that era, we gradually recognized that the target goal was to lower the diastolic number to less than 90 mm Hg, which remains our treatment target for most people even now.
By 1980, after a decade of this new interest in treating blood pressure, we began to notice the death rate from heart problems and stroke starting to decline in a clear pattern of improvement. This pattern of decline was also noticed in several European nations, where there had also been a new effort to control blood pressure. Since the treatment of high blood pressure had been the only widespread new treatment of the heart and vascular system, this improvement was clearly related to our new efforts at controlling blood pressure.
In the early 1990s several studies in the United States and Europe answered the very important question about whether we should be treating an elevated systolic number, even if the diastolic number is normal. The studies focused on older patients with an elevated systolic number, and showed quite clearly that lowering this elevated systolic number resulted in reductions of heart problems and stroke rates.
These studies closed the loop, showing that control of both the systolic and diastolic numbers was important for proper health. Further research focused on determining the target levels of blood pressure that we should achieve with our medication. For routine patients, those with high blood pressure but without damage to vital organs like the heart, brain, or kidneys, the targets are less than 140/90. Lower targets are recognized for patients with kidney failure, heart disease, previous stroke, and diabetes.
National health surveys demonstrate that we are continuing to make progress in the quality of blood pressure control in the United States. In the 1970s, surveys showed the percentage of patients with their hypertension controlled to acceptable levels was only about 10%. By 2003, the control rates for blood pressure in patients with hypertension had increased to more than 30%. In the latest survey, covering the 2007-2008 years, the percentage of patients with hypertension who have their blood pressure controlled jumps to a remarkable 48.4%.
This improvement represents a tremendous success in the delivery of medical care here in the United States. While there are multiple factors that contributed to this amazing improvement in control rates, availability of low cost generic drugs a principal factor, the major cause of this success is probably increased vigilance by both the medical community and patients to control the pressure. As someone who has written numerous articles on the treatment of hypertension and has delivered hundreds of lectures nationally on the management of hypertension, this is a very gratifying pattern of progress. With that success, we have seen the death rate from heart disease decrease by 50% since the 1970s. This fact should only encourage us to work harder to manage high blood pressure in all patients.
Other important issues relate to high blood pressure, including the impact of age, ethnicity, and lifestyle concerns like weight. It should not come as a surprise to anyone if they develop hypertension as they age into their fifties or sixties. Indeed, by the time that we are into our sixties over 60% of Americans have developed high blood pressure.
Hypertension is more common in African Americans than in Americans of other ethnicity, with about a 10-15% higher rate. The reason for this is not at all understood, and is further complicated by the fact that the disorder is often more severe and more difficult to control in African Americans. This simply means we must be more aware and treat this disorder more aggressively in African Americans. This may be an issue of particular importance in younger African American men, where significant hypertension can frequently be seen in men in their thirties.
Proper technique states that blood pressure should be obtained in the physician’s office with the patient sitting quietly for five minutes, the arm for measuring the pressure rested at about heart level on a table or similar structure, and both feet flat on the floor. While there is interest in whether readings by the patient outside of the office (home BP readings) or by a 24-hour blood pressure device may be useful in the future to improve management of blood pressure, the only accurate reading is that obtained in the medical office, properly measured as I described. Since all of our long term research projects showing blood pressure treatment reduced heart attack and stroke were done by readings in the physician’s office, I believe this is the only completely reliable way to monitor and guide blood pressure management.
Future research may give us better information on the use of home blood pressure and/or 24-hour ambulatory pressure readings, but that time is not here yet. It is widely recognized in the hypertension research community that blood pressure readings measured by patients at home are about 5 to 10 mm Hg lower than those obtained in the office. At this stage in our experiences, patients should not use these naturally occurring lower readings at home to delay treating their high blood pressure that is detected in the office.
Medications and Treatments
There has been a brisk debate for over two decades on whether one type of medication to lower blood pressure produces superior reduction of heart attack and stroke compared to any of the other classes. This argument began with the markedly different costs of the different classes of blood pressure lowering medications. In the 1980s, only the diuretics and some of the beta blocker medications were available as low cost generic pills. Now, more than 20 years later, nearly all of the blood pressure lowering medications have become low cost generic medications—making it much easier for physicians and patients to develop a medication regimen that is both successful and affordable. Having studied this issue very thoroughly for the book I wrote several years ago, no evidence supports the claim that treatment of blood pressure with any particular class of medication is superior in reducing heart attack and stroke when used to treat the overall high blood pressure population. While there are differences in certain sub-groups of patients, in general it can be said, "That you control the blood pressure is what matters, not how you control it!"
There has been considerable interest in non-medication, or lifestyle measures to control blood pressure. Sodium restriction is probably of limited value in most high blood pressure patients who do not have heart or kidney failure also. Losing weight is clearly the most important and successful non-medication effort to control blood pressure. However, as we all know, successful weight loss requires constant attention and significant personal discipline for nearly all of us. I would not delay starting medication therapy while waiting a considerable period of time as a patient struggles to lose weight. Medication can be started promptly and then reduced or stopped in the future if the patient loses weight successfully. A regular exercise program can also lower blood pressure, particularly if strictly adhered to.
One issue many patients are not aware of is that in studies where patients are compelled to add further medication to control blood pressure, the majority of high blood pressure patients need at least three different medications in combination. I myself take four blood pressure medications, and I have patients on five different blood pressure medications. Remember, the consequences of not controlling your blood will be early heart disease or stroke, so be willing to take an aggressive approach if so advised by your physician.
Thiazide diuretics, or fluid pills, have been widely used to control blood pressure since their development in the 1950s. Contrary to popular belief, their ability to lower blood pressure is unrelated to the diuresis, or increased fluid loss through increased urination. The exact mechanism through which they lower blood pressure remains unclear even after all these decades of use. Diuretics are effective in nearly all patients, but are particularly useful, almost essential, in two particular groups of patients—the elderly with an elevation of the systolic number, and in African Americans with resistant hypertension, usually in addition to other agents.
Thiazide diuretics are easy to use, with a once daily dose, and are very inexpensive. They are not free of side effects, however, frequently causing fatigue, lethargy, sexual dysfunction, an increase in blood sugar in those with a tendency towards diabetes, and loss of potassium. Lower doses we now use have reduced but not eliminated these side effects. Diuretics have been combined with a variety of other blood pressure medications in combination products that should be more convenient for patients once the correct doses have been determined.
Angiotensin converting inhibitors, popularly known as ACE-Inhibitors, are premier agents in the treatment of hypertension and a wide variety of other diseases of the heart and vascular system. Included in this category are agents such as lisinopril, enalapril, and fosinopril, among others. ACEs lower both the systolic and diastolic pressure equally well and work in patients of all ages. While African American hypertensives are not quite as responsive as hypertensives of other ethnic groups, the ACEs are effective if given in their maximum doses. Their main side effect is a dry, tickle in the throat cough that can be seen in between 5-20% of patients. There is a very rare but more serious problem called angioedema, resulting in swelling of the lips, face, and even throat.
In addition to lowering blood pressure, ACEs treat many other serious medical problems, so that many patients are placed on ACE inhibitors even when they do not necessarily have high blood pressure. So, if a patient has heart attack, angina, heart failure, diabetes, or kidney failure, it is typical for them to be placed on an ACE even if their blood pressure is already normal. In people with these problems, treatment with an ACE inhibitor has been shown to protect against heart attack, improve heart function, and protect against kidney decline. Fortunately, these agents are now all available as low cost generic preparations.
Calcium Channel Blockers have been among the most popular of the blood pressure treatment medications. One agent, amlodipine, marketed as Norvasc®, has been the most widely prescribed blood pressure lowering agent in history. Calcium channel blockers come in two main categories. Agents like amlodipine are used sometimes to treat angina or heart pain from blockage of the arteries of the heart, but mostly it is used is to control elevated blood pressure. The other group of calcium channel blockers includes verapamil and diltiazem, which are frequently used to treat abnormal rhythms of the heart, particularly fast heart beats coming from problems in the top of the heart. They are also used for the treatment of high blood pressure, even in the absence of heart rhythm problems.
The amlodipine group of agents remains very popular for treating high blood pressure, being very potent in lowering pressure rapidly. Their side effects are quite modest, with only some swelling of the lower legs and constipation seen frequently. However, they have not been shown to have the wide variety of protective properties for other disease and organs like the ACE inhibitors, specifically in heart attack or heart failure patients, and do not reduce kidney failure in kidney or diabetic disease. They do have protective properties only in patients with diabetes. In light of these patterns, these agents remain very useful and will continue to be so in the treatment of hypertension, but not across the wide range of other problems like the ACE inhibitors.
Beta Blockers (metoprolol, carvedilol, atenolol, and others) are interesting agents. Though initially very popular medications for the treatment of hypertension, that popularity has waned in the last decade. Beta blockers work by reducing the effects of the adrenergic, or adrenalin based, nervous system. By reducing the adrenergic system, they do lower blood pressure reasonably. However, re-examination of their record in treating hypertension has raised questions as to whether they should be used regularly instead of other agents for treating hypertension. While the beta blockers do a reasonable job in reducing the diastolic pressure, they are less effective at lowering the systolic pressure number. Since elevation of the systolic number is often the more difficult pressure to control, that pattern has reduced the use of beta blockers in routine hypertension, or hypertension in patients who do not have other complicating problems. However, in patients with a wide variety of complicated problems, particularly heart problems, the beta blockers are life saving medications. In patients with a previous heart attack or chest pain from heart problems, or with heart failure, beta blockers are critical therapy. They have also been shown to be effective in treating heart rhythm problems, migraine headaches, and tremors (or trembling of the hands). Beta blockers are sometimes difficult to tolerate, causing fatigue, lethargy, and sexual dysfunction. Such side effects are often related to the dose taken, so careful attention to dosing is important.
The Angiotensin Receptor Blockers (ARBs) are the latest large group of blood pressure lowering agents to come onto the market. Only a few of the agents have been on the market long enough to become low cost generic medications, with most still being higher cost. Also, the ARBs are the only group of blood pressure lowering agents where there is a clear difference in the potency, or blood pressure lowering effect, between the older, weaker medications and the newer, more effective ones. ARBs are extremely well tolerated, essentially having no side effects. They also have been shown to reduce kidney failure in people with diabetes, regardless of whether they have elevated blood pressure or not. One agent, Micardis®, has been shown to reduce heart attacks and other problems in people with diabetes or heart problems, while another, Atacand ®, has been helpful in treating heart failure. Whether these benefits could be seen with the other agents in the ARB category is not known. Overall, the ARBs are very useful, well tolerated blood pressure lowering medications with other benefits for certain of the agents on the market.
Several other classes of blood pressure lowering agents are available for your physician to consider as additional therapy if your pressure cannot be controlled by combinations of the agents discussed previously. Many of these are older agents with considerable side effects. Other agents, the alpha-1 blockers, have limited potency but still are useful as additional therapy on top of the other agents to control problem hypertension.
In summary, hypertension, or high blood pressure, is the most frequent, long-term medical problem currently seen in modern medical care. However, patients and physicians can successfully control this very common and serious problem. The advances in the development of modern medications have allowed us to control this disease and to produce a major reduction in heart attack and stroke, and to produce the great increase in longevity that we are seeing in the United States now. If you have hypertension, work closely with your physician to control this major illness.
ABOUT THE AUTHOR
Robert Guthrie M.D., is both a family physician and a general internist, and he currently is a professor at The Ohio State University in Columbus, OH. At Ohio State, he conducts research projects to develop new medications for the treatment of common disorders like high blood pressure and diabetes. He has published one book, numerous medical articles, has lectured extensively nationally and internationally, and been a long-term participant on local and national radio broadcasts. This column discusses a wide variety of health topics of interest to the general public.