14

14 CASE 14


A 45-year-old man presents at the clinic after having a reading of elevated blood pressure at a health department screening. His blood pressure is 160/110 and is equal in both arms and legs. He has no other health concerns.


He is alert and cooperative but appears to be anxious. The patient reports being a social drinker and smokes 1½ packs of cigarettes a day. He indicates that he is too busy to exercise. There is a family history of heart disease but no family history of diabetes.



PHYSICAL EXAMINATION



VS: T 37°C, P 80/min, R 15/min, BP 165/110 mm Hg

PE: BMI 32


LABORATORY STUDIES



SMA-12: All within normal ranges

ECG: Left axis deviation


DIAGNOSIS


Essential hypertension



PATHOPHYSIOLOGY OF KEY SYMPTOMS


Arterial blood pressure is determined by the volume of blood in the arterial system and the arterial compliance. Volume of blood in the arteries reflects the inflow from the cardiac output and the outflow, determined by total peripheral resistance (see Fig. II-2)


Hypertension has few, if any, symptoms. It is only when systolic blood pressure is in the range of 200 mm Hg that symptoms of headache, nausea, and dizziness become apparent. Most instances of hypertension are discovered at screenings or when the patient is at the health care provider for unrelated problems.


There are numerous endocrine problems that are characterized by intermittent or persistent hypertension. These include pheochromocytoma, excessive aldosterone production, and excessive angiotensin II production. These hormone levels can be measured to rule out secondary causes of the hypertension.


Acute alterations in arterial blood pressure are buffered by the arterial baroreceptor reflex. When blood pressure in the carotid sinus or aortic arch falls there is a reflex activation of the sympathetic nervous system and inhibition of the parasympathetic nervous system. The resultant increases in heart rate, ventricular contractility, arteriolar constriction, and venous constriction all act to restore blood pressure back toward normal (Fig. 14-1).


image

FIGURE 14–1 Typical carotid sinus reflex effect on aortic arterial pressure caused by clamping both common carotids (after the two vagus nerves have been cut).


Persistent hypertension, however, is tied more closely to renal regulation of circulating blood volume. The arterial baroreceptors adapt over time, resetting to the new blood pressure level. Blood volume regulation by the kidneys does not show that adaptation and, consequently, is the dominant long-term regulator of arterial blood pressure.


The patient shows signs of anxiety, which causes an increase in sympathetic activity. A diagnosis of hypertension is confirmed after separate determinations of an elevated blood pressure. Anxiety can be a confounding factor, as the increase in sympathetic nervous system activity can cause an acute increase in blood pressure. Consequently, a determination of hypertension is made only after three separate readings of an elevated blood pressure. The need for an accurate diagnosis must be balanced against the potential risk to the patient. If left untreated for 3 months, there is a twofold increase in cardiovascular morbidity and mortality in high-risk hypertensive patients.


Essential hypertension is a diagnosis of exclusion. Physical examination and diagnostic testing rule out secondary causes of hypertension, because the treatment options need to be directed against the underlying cause for the elevated blood pressure.


Chronic hypertension results in a hypertrophy of the left ventricle. This hypertrophy can be evident on cardiac imaging or can be manifested by a left axis deviation of the electrocardiogram. The ventricular hypertrophy results from the increased work load imposed on the left ventricle due to the elevated afterload (arterial pressure). This ventricular remodeling occurs only after many months of persistent hypertension (Fig. 14-2).


image

FIGURE 14–2 Left axis deviation in a hypertensive heart (hypertrophic left ventricle). Note the slightly prolonged QRS complex as well.

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Jul 4, 2016 | Posted by in PHYSIOLOGY | Comments Off on 14

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