Hypertension

First, some definitions...

• Normal blood pressure: systolic <120 mmHg and diastolic <80 mmHg
• Prehypertension: systolic 120 to 139 mmHg or diastolic 80 to 89 mmHg
• Hypertension:
• Stage 1: systolic 140 to 159 mmHg or diastolic 90 to 99 mmHg
• Stage 2: systolic ≥160 or diastolic ≥100 mmHg

Primary (Essential) Hypertension 

Pathogenesis - poorly understood for but the following have been implicated in primary HTN

• Increased sympathetic neural activity
• Increased Ang II and mineralcorticoid activity
• Genetic predisposition
• Reduced nephron mass

Risk Factors 

• Excess Na or ETOH intake
• Obesity and weight gain
• Physical inactivity
• dyslipidemia
• Depression
• Vitamin D deficiency

Secondary causes of HTN

• Medications - chronic NSAIDs, oral contraceptives and antidepressants. 
• Primary renal disease - vascular and glomerular
• Hyperaldosteronism - the presence of primary mineralocorticoid excess, primarily aldosterone, should be suspected in any patient with the triad of hypertension, unexplained hypokalemia, and metabolic alkalosis.
• Cushing's syndrome
• Hyper/Hypothyroidism and Hyperparathyroidism
• Obstructive sleep apnea
• Coarctation of the aorta

When should you start working up secondary causes of HTN?

It is not cost effective to perform a complete evaluation for secondary hypertension in every hypertensive patient. Thus, it is important to be aware of the clinical clues that suggest secondary hypertension. Clinical clues include...

• Severe or resistant hypertension. Resistant hypertension is defined as the persistence of hypertension despite concurrent use of adequate doses of three antihypertensive agents from different classes, including a diuretic.
• An acute rise in blood pressure developing in a patient with previously stable values.
• Age < 30 years of age in non-obese, non-black patients with a negative family history of and no other risk factors (obesity, HLD) for hypertension.
• Malignant or accelerated hypertension (patients with severe hypertension and signs of end-organ damage such as retinal hemorrhages or papilledema, heart failure, neurologic disturbance, or acute kidney injury). 
• Proven age of onset before puberty.

Tests to order and Physical Exam findings

• BMP to look at the BUN and CR and assess for primary renal disease
• US of the renal vasculature to search for RAS or Fibromuscular Dysplasia 
• On physical exam, carotid, abdominal, or femoral bruits suggest atherosclerotic disease and possible renal artery stenosis, diminished femoral pulses and/or a discrepancy between arm and thigh blood pressures suggest aortic coarctation or significant aortoiliac disease
• Screening for primary aldosteronism begins with a paired, morning measurement of the plasma aldosterone concentration (PAC) and plasma renin activity (PRA) to determine whether the patient has an elevated or high-normal PAC, suppressed PRA, and elevated PAC/PRA ratio
• If the patient is showing clinical clues for pheochromocytoma (episodic headache, sweating, and tachycardia) then measuring fractionated metanephrines and catecholamines in a 24-hour urine collection is the intial step. 
• For Cushing disease workup, UptoDate recommends two first-line tests should be abnormal to establish the diagnosis of Cushing's syndrome. First line tests include...late night salivary cortisol, urinary cortisol, and the low-dose dexamethasone suppression tests
• Sleep study for OSA
• TSH and PTH levels