INTRODUCTION TO HYPERTENSION (HTN)
Definition: HTN is simply defined as a persistently abnormal elevation in blood pressure, < 140/90mmHg. HTN is not diagnosed unless BP is elevated on multiple occasions (at least 2-3) or if the patient is complications of HTN (as with patients admitted with hypertensive emergency). We treat HTN because it is a major risk factor for stroke, MI, CCF, CKD, retinopathy and peripheral vascular disease. The risk of hypertensive complications increases continuously throughout the BP range.
Physiology of HTN: HTN is caused by a combination of cardiac output, peripheral vascular resistance and sodium retention (regulated by the renin-angiotensin system). The latter 2 factors are more important. All treatment of HTN targets these factors.
Epidemiology: HTN is a growing problem in sub-Saharan Africa. Early studies indicated HTN was rare in Africa but several recent studies have shown that the prevalence of HTN is now 5-15% (higher in urban areas). One from Tanzania indicated that HTN occurs in 22% of males and 18% of females in Dar es Salaam and 13% of both men and women in rural areas (Edwards et al., 2000)! The average blood pressure in this group was higher than studies from America and Europe!
Types of HTN:
- Essential (Primary) HTN – most common (95%) and due to a combination of genetic, environmental factors (salt intake, weight, exercise etc) and age. Usually develops after the age of 30 but can develop earlier.
- Secondary HTN – HTN due to other causes. All patients < 30yo with HTN should be assessed for these conditions.
- Renal – most common; can be related to CKD or renal artery stenosis
- Cushing’s syndrome – hypercortesolemia
- Conn’s syndrome - hyperaldosteronemia
- Coarctation of the Aorta
- Pheochromocytoma – catecholamine producing tumor
- Hyperthyroidism or hypothyroidism.
Degrees of HTN:
- Mild (Grade 1) = 140-160/90-99mmHg
- Moderate (Grade 2) = 160-180/100-109mmHg
- Severe (Grade 3) = > 180/110mmHg
- Hypertensive Urgency – severe HTN but no end organ damage
- Hypertensive Emergency – severe HTN with end organ damage
i. Usually does not occur unless sudden increase in DBP to < 130mmHg. Was called malignant HTN in the past.
ii. Signs of end organ damage can include encephalopathy (confusion with severe HA), blurry vision/retinal hemorrhage, angina, pulmonary edema, aortic dissection and acute kidney injury
Symptoms/Signs: Most patients with HTN are asymptomatic! Symptoms and signs develop only with complications of HTN or in cases of secondary HTN. The only reliable sign of HTN is the blood pressure.
- Measuring the BP – The blood pressure cuff must be large enough so that the bladder of the cuff encircles the arm + 30%! If the cuff is too small the blood pressure will be falsely elevated.
Diagnosis: HTN is diagnosed if BP is elevated on 3 separate occasions. Once the diagnosis of HTN has been made the following steps tests should be ordered:
- Cr, electrolytes, RBG, cholesterol, ECG, fundoscopy in all patients
- TSH, Renal US (with dopplers), urinary catecholamines/VMA/cortisol, serum renin/aldosterone, CXR, Echo if looking for cause of secondary HTN
Other important concepts:
“Burnt out” HTN – Occurs in patients who have had severe, long standing HTN but have now progressed to CCF (usually with dilated ventricles) with decreased systolic function and a blood pressure that is now normal or low.
Case #1
A 25 year old obese female patient comes to your clinic for a pregnancy test. Her LMP was 28 days ago but she is “hoping that she is pregnant.” She has not other complaints. Her past medical and social histories are unremarkable? The test is negative but on examination you note that the patient’s blood pressure is 150/96.
- Would you diagnose this patient with hypertension?
Not yet. Must have at least 2 measurements or complications.
- If not, how would you follow the patient?
Have the patient return to clinic in 1-2 weeks for repeat BP.
You have the patient return to clinic in 1 week and her BP is still 150/96. The patient still denies any complaints.
- What is your impression?
Hypertension.
- If this patient has hypertension, what other disease will she be at risk for?
We treat HTN because it is a major risk factor for stroke, MI, CCF, CKD, retinopathy and peripheral vascular disease.
- What are the 2 most important pathophysiologic contributers to hypertension?
Increased PVR and sodium retention. Review pathophysiology.
- How common is hypertension in adults > 30yo in Tanzania?
Approximately 10%! Review epidemiology.
- What grade of hypertension does this patient have?
Grade I (mild). Review grades of hypertension.
- Are you surprised that the patient does not have any symptoms? Do most patient with hypertension have symptoms?
No, most patients with hypertension are asymptomatic until the hypertension is severe.
- What physical exam signs do you commonly find in patients with hypertension?
The only reliable sign of hypertension is BP. No other signs unless complications or secondary cause.
The patient’s exam is normal. You diagnose the patient with mild (grade I) hypertension and decide to send her for investigations.
- What makes you think that this is not a simple case of essential hypertension?
Essential hypertension uncommon in patients < 30 year old. Review difference between essential and secondary hypertension.
- Which types of secondary hypertension would you consider in this patient?
CKD would be the most likely. Review all types secondary hypertension but emphasize that most of these are rare most would have physical signs or symptoms (review these).
- Which investigations would you send?
Cr, electrolytes, RBG, cholesterol, ECG, fundoscopy, TSH. Other investigations less important as other secondary causes of hypertension less likely in this patient with no symptoms and normal physical examination.
The patient’s creatinine returns as 300 mmol/L. The potassium is 4.0meq/L and the sodium is 140meq/L. All other investigations are normal.
- What is your impression now?
Mild hypertension secondary to kidney disease.
- What would you have thought if the creatinine was normal, the potassium was low and the sodium was high?
Hyperaldosteronism (Conn’s), review pathophysiology in this condition.
The patient never returns to clinic but 1 year later you admit her to the hospital with a chief complaint of headache and confusion for 1 day. There is no fever. The BP is 210/140 and the GCS is 14/15. The neurologic exam is otherwise normal (with no hemiparesis). All other systems are normal.
- What is your impression? Be specific. Hypertensive Emergency with Hypertensive Encephalopathy.
