Hypertension
By Dr Paul Chiam
Published on Medical Grapevine on August 2015
Hypertension is a common condition whose incidence rises with age. With with an aging population, it is increasingly common. Hypertension is usually diagnosed when the patient has 2 separate readings of blood pressure (BP) > 140/90 mmHg.
Some of our patients have “white coat” hypertension; though this condition usually does not require treatment, there is some evidence that it is not as benign as previously thought, and close monitoring of the patient’s BP would be required. However, for the purpose of this article, white coat hypertension would not be further discussed.
Why bother detecting hypertension
Hypertension is asymptomatic in the vast majority of patients. In rare cases, very high blood pressure can result in headaches (although most headaches are unrelated to the patient’s BP), blurred vision (due to papilloedema) and shortness of breath (left ventricular failure). In most people, it is however, a “silent” killer. Long standing poorly controlled hypertension increases arterial stiffness and causes end organ damage leading to an increased risk of stroke, myocardial infarction, heart failure, renal failure and aortic aneurysm.
This makes it important to detect and treat patients, especially younger patients, to reduce the risk of such events. It has been shown however, that even very elderly patients (> 80 years) derive benefit in the treatment of hypertension as they experience less stroke and less cardiac adverse events. Thus regardless of age, treatment of hypertension would be beneficial in virtually all patients.
Causes of hypertension
In the vast majority of patients with hypertension, no specific cause can be found (“essential” hypertension). Usually many factors contribute to hypertension in such patients including genetics (family history), lifestyle (sedentary lifestyle), stress (high stress environment), high salt diet etc.
In few patients (usually the very young patients < 35 years), an underlying disease may be the cause of hypertension. In this age group, investigations (including an ultrasound of the renal arteries, blood and urine tests) are performed to rule out an underlying disease. In older patients, particularly those > 65 years, the commonest underlying cause (if any) is renal artery stenosis. In these rare cases, treatment of the underlying disease may “cure” the patient of hypertension.
Treatment of hypertension
Most patients with hypertension can achieve satisfactory BP control with lifestyle modifications and drug therapy. A low salt diet, regular exercise, weight loss and reduced stress can lead to a lower BP. These may help patients with mild hypertension; however, as it is unlikely that the BP would be reduced by more than 10 mmHg on average even with these measures, most patients will still require some drug therapy.
The new JNC 8 guidelines (issued in 2014) from the American Joint National Committee on Hypertension have recommended a slight relaxation of blood pressure targets as compared to the previous JNC 7 guidelines. For elderly (>60 years) with hypertension, the guidelines recommend initiating therapy when the BP is ≥ 150/90 mmHg and to treat to a target BP of ≤ 150/90 mmHg (previously the target was ≤ 140/90 mmHg). For younger patients (< 60 years), the recommendation is to initiate therapy when the BP is ≥ 140/90 mmHg and to treat to a target BP of < 140/90 mmHg (previous target unchanged).
The other significant recommendations are for patients ≥ 18 years with diabetes mellitus or chronic kidney disease, the guidelines now recommend initiating therapy when the BP is ≥ 140/90 mmHg and to treat to a target BP of < 140/90 mmHg (previous targets were 130/80 mmHg for both patients with diabetes or chronic kidney disease [CKD]).
These new targets have come about from a comprehensive review of only randomized trial data compared to JNC 7 where non-randomized trial data and expert opinion were also used in generating the guidelines. Thus these new targets were derived from larger trials showing clinical benefit in treating the various groups of patients to the respective targets.
The new guidelines also recommend only 4 classes of drugs as the first line in treating (non-black) patients with hypertension: thiazide-type diuretics, calcium channel blockers (CCB), angiotensin converting enzyme inhibitors (ACEI) and angiotensin receptor blockers (ARB). However, note that ACEI and ARB should not be used together in the same patient.
This is different from the JNC 7 guidelines where a thiazide-type diuretic was recommended as the initial therapy for most patients. Significantly, beta-blockers are no longer recommended for initial BP treatment because of a higher rate of composite cardiovascular events in some studies (driven largely by an increase in stroke).
In patients with CKD between age 18 – 75 years, anti-hypertensive treatment should include an ACEI or an ARB, as these drugs have been shown to improve renal outcomes.
A few different dosing strategies are also suggested by the JNC 8 guidelines to try to reach BP goals. The conventional method has been to maximise the first drug before adding a second. Another option would be to use an initial drug, and to add a second drug before reaching the maximum dose of the first drug. A third option would be to start 2 drugs at the same time especially if the systolic BP is ≥ 160mmHg and /or the diastolic BP is ≥ 100mmHg, OR if the SBP is ≥ 20mmHg and/or the DBP is ≥ 10mmHg. Whichever the method employed, titrate drugs doses or add a third drug to achieve BP targets. If BP goals still cannot be achieved after maximizing doses of all 3 classes of drugs, then antihypertensive drugs from other classes can be used (eg. hydralazine etc.). In patients with refractory hypertension or in complicated patients with hypertension, a referral to a cardiologist or a hypertension specialist may be indicated.
Conclusion
The new guidelines represent a simplification and “relaxation” of BP targets with a goal of < 150/90mmHg for elderly patients above age 60 years, and < 140/90mmHg for all other patients (younger patients, or patients of any age with diabetes or chronic kidney disease). However, for pre-existing hypertensive patients with BP control below the new targets, there is no necessity to amend or adjust their therapeutic regimen.
