Chapter 6

Initiation and Monitoring of Antihypertensive Therapy

• Drug therapy is initiated after establishing:
  • -    The diagnosis of hypertension.
  • -    That life style modification alone is not enough to normalize blood pressure.
  • -    That treatment is cost effective.
• Unless there is an emergency or urgency, a period of observation and blood pressure monitoring varying from one week up to twelve months may be needed before starting drug treatment.
•   Assessment of absolute cardiovascular risk i.e. probability of developing a serious cardiovascular event in the coming years will guide the need and urgency of drug therapy. Priority is given to high risk patients.
• Cardiovascular risk profile depends upon the presence of: 1. Clinical atherosclerotic cardiovascular disease. 2. Target organ damage. 3. Number and severity of other cardiovascular risk factors.  4.   Diabetes mellitus  5. Level of blood pressure.
• Threshold blood pressure required to start drug intervention varies from 135/85 to 160/100 mmHg depending upon the global cardiovascular risk profile.

Assessment of Cardiovascular Risk Profile

• ·   While establishing the diagnosis of hypertension, the physician should assess the global risk profile of the patient. This approach will guide the therapeutic policy, timing and threshold for initiation of drug therapy and aggressiveness of blood pressure lowering.
• ·   The risk of cardiovascular disease in patients with hypertension is determined not only by the level of blood pressure but also by the presence or absence of target organ damage, other cardiovascular risk factors, associated clinical conditions and diabetes. These factors independently modify the risk of subsequent cardiovascular diseases and are used for empiric classification of patients with hypertension into risk groups for therapeutic decisions.

Cardiovascular Risk Categorization

Depending upon the global risk profiling, hypertensive patients can be categorized into three groups:

Risk Group A (Low risk): patients with no other cardiovascular risk factors, no target organ damage or associated atherosclerotic cardiovascular diseases.

Risk Group B (Intermediate risk): patients with risk factors (not including diabetes) but with no target organ damage or associated atherosclerotic cardiovascular diseases.

Risk Group C (High risk): patients with diabetes, target organ damage or associated atherosclerotic cardiovascular diseases.

Table 5. Cardiovascular Risk Factors

Table 6. Target Organ Damage and Associated Atherosclerotic Diseases

Initiation of Antihypertensive Drug Therapy

• ·   Unless there is an emergency or blood pressure > 210/120 mmHg, no drug treatment should be instituted during the first two office visits so as to rule out the presence of "white coat" hypertension.
• ·   Duration of blood pressure monitoring before initiating drug therapy varies depending upon blood pressure level, risk profile and response to life style modification (table 7).
• ·   Threshold for antihypertensive drug treatment is 160/100 mmHg in low risk group, 140-150/90 mmHg for intermediate risk group and 135-140/85 mmHg in high risk group (table 8). The previous blood pressure cut points are the average of blood pressure readings taken on three separate office visits at least one week apart.

Table 7. Duration of Observation Period (life style modification) before     

         Initiating Drug Therapy

Table 8. Threshold for Initiating Therapy after an Observation Period

Selection of Antihypertensive Agents

•   Start with a small dose of thiazide diuretics in all patients with mild to moderate hypertension unless they are contraindicated or there are specific indications for other agents.
•   In severe cases (blood pressure > 180/110 mmHg), it is recommended to start by more than one drug or a fixed dose combination (should include a diuretic) and to increase the dose or add a third drug if blood pressure remains elevated above target level after 4-8 weeks.

Factors Influencing Choice of First Drug

Target Organ Damage and Associated Cardiovascular Diseases

• Renal disease: ACE-inhibitors or angiotensin receptor blockers (ARBs)+ thiazide diuretics (loop diuretics if serum creatinine is above 2.5 mg/dl).
• Coronary disease: beta adrenergic blockers, ACE-inhibitors and if necessary calcium antagonists.
• Heart failure: ACE-inhibitors and thiazide diuretics.
• After stroke: thiazide diuretics.
• Peripheral arterial disease: calcium antagonists.

Other Cardiovascular Risk Factors

• Elderly: start with small dose of thiazide diuretics and add calcuim antagonists or ARBs if necessary. Check blood pressure always in the supine and standing positions. Be aware of the marked fluctuations in blood pressure, the auscultatory gap when measuring blood pressure and the frequent comorbid conditions.
• Diabetes mellitus: initiate drug therapy within days after confirming the diagnosis of hypertension aiming at a target blood pressure of less than 140/85 mmHg, even lower levels in presence of proteinuria. Start with ACE-inhibitors and add thiazide diuretics, calcium antagonists, beta blockers or ARBs if necessary. In presence of proteinuria, ARBs may replace ACE-inhibitors as initial therapy.
• Hypercholesterolaemia: alpha adrenergic blockers, central alpha agonists, calcium antagonists, ACE-inhibitors.

Concomitant Disease

• ·   Obesity: thiazide diuretics.
• ·   Benign senile prostatic hypertrophy: alpha adrenergic blockers.
• ·   Migraine: beta-adrenergic blockers.
• ·   Essential tremors: beta-adrenergic blockers.
• ·   Anxiety, tachycardia, hyperdynamic heart: beta-adrenergic blockers.
• ·   Supraventricular tachyarrhythmias: non- dihydropiridine calcium antagonists.

Target Blood Pressure

• ·   Target blood pressure varies from 135/85 to 140/90 mmHg depending upon risk profile:
• -    Low and intermediate risk groups: below 140/90 mmHg
• -    High risk group: below 135/85 mmHg.

Monitoring of Drug Therapy

• ·   Antihypertensive drugs require a period of up to two months to achieve their maximal hypotensive effect. Do not change drugs at short intervals.
• ·   Recheck blood pressure at one to two monthly intervals until blood pressure remains at target level for two consecutive visits then recheck at 3 to 6 month intervals depending upon the risk profile.
• ·   In absence of adequate blood pressure response (fall in systolic blood pressure by 10 mmHg and diastolic blood pressure by 5 mmHg) after one to two months of drug therapy add another drug from a different pharmacologic group or use single dose combination.
• ·   Treatment and follow-up should continue indefinitely. The frequency of visits to doctors’ office depends upon level of blood pressure and risk profile.