What are the stages of hypertension according to Harrison's Principles of Internal Medicine?

Stages of Hypertension According to Harrison's Principles of Internal Medicine

Blood Pressure Classification System

Harrison's Principles of Internal Medicine follows the JNC 7 (Joint National Committee) classification system, which categorizes blood pressure into four distinct levels based on office measurements 1, 2:

Normal Blood Pressure

• Systolic BP <120 mm Hg AND Diastolic BP <80 mm Hg 1, 2
• This represents optimal cardiovascular health with the lowest risk for future hypertensive complications 1

Prehypertension

• Systolic BP 120-139 mm Hg OR Diastolic BP 80-89 mm Hg 1, 2
• This is not a disease category but rather a designation to identify individuals at high risk of developing hypertension 1
• Individuals in this range have twice the risk of developing hypertension compared to those with normal BP 2
• Cardiovascular risk doubles for every 20 mm Hg systolic or 10 mm Hg diastolic increase above 115/75 mm Hg 2
• Lifestyle modifications are strongly recommended to prevent progression 1

Stage 1 Hypertension

• Systolic BP 140-159 mm Hg OR Diastolic BP 90-99 mm Hg 1, 2
• Requires confirmation within 2 months with repeated measurements 1
• Drug therapy is typically initiated along with lifestyle modifications 1

Stage 2 Hypertension

• Systolic BP ≥160 mm Hg OR Diastolic BP ≥100 mm Hg 1, 2
• This category combines what were previously stages 2 and 3 in JNC 6, as the management approach is similar 1
• Requires evaluation or referral to care within 1 month, or immediately if BP is extremely elevated (e.g., 180/110 mm Hg) depending on clinical situation 1

Critical Measurement Requirements

Blood pressure classification must be based on the average of ≥2 properly measured, seated readings on each of ≥2 separate office visits 1, 3. The patient should be:

• Seated quietly for at least 5 minutes with feet on the floor and arm supported at heart level 1
• Avoiding caffeine, exercise, and smoking for at least 30 minutes prior to measurement 1
• Using an appropriately sized cuff (bladder encircling at least 80% of the arm) 1

Important Classification Rules

When systolic and diastolic pressures fall into different categories, the higher category should be used for classification 1, 3. For example, a BP of 160/86 mm Hg would be classified as Stage 2 hypertension based on the systolic value 1.

Key Differences from Other Guidelines

While Harrison's follows JNC 7 classification, it's important to note that the 2017 ACC/AHA guidelines lowered the threshold for hypertension to ≥130/80 mm Hg 1, 3. However, the JNC 7 classification (≥140/90 mm Hg) remains widely used and is what Harrison's references 1, 2. The European guidelines (ESC/ESH) also maintain the ≥140/90 mm Hg threshold but use a more granular six-category system with Grade 1,2, and 3 hypertension 1, 3.

Common Pitfalls to Avoid

• Do not diagnose hypertension based on a single elevated reading - multiple measurements over time are essential to avoid misclassification, particularly to exclude white-coat hypertension 1, 3
• Do not ignore prehypertension - this range carries significant cardiovascular risk and warrants aggressive lifestyle modification 1, 2
• Do not use immediate-release nifedipine or hydralazine for acute BP lowering in hypertensive urgencies, as these can cause unpredictable drops 4