18.1 Hypertension and Angina

Pathophysiology and Diagnosis of Hypertension and Angina

Hypertension and angina are two cardiovascular conditions that directly affect how well the heart delivers blood and oxygen to the body. Hypertension raises the pressure against arterial walls, while angina signals that the heart muscle itself isn't getting enough oxygen. Both conditions share overlapping risk factors, and understanding their mechanisms is the foundation for knowing why specific drug classes are used to treat them.

Mechanisms of Hypertension and Angina

Hypertension develops through two main hemodynamic pathways: increased cardiac output and increased peripheral vascular resistance. Blood pressure is the product of these two factors, so a rise in either one raises BP.

• Increased cardiac output results from elevated heart rate, increased stroke volume, or both
• Increased peripheral vascular resistance occurs through vasoconstriction, atherosclerotic plaque buildup in arteries, and arterial stiffening that comes with aging

At the molecular level, there's normally a balance between vasoconstrictors (angiotensin II, endothelin-1, catecholamines) and vasodilators (nitric oxide, prostaglandins). In hypertension, this balance tips toward vasoconstriction.

The renin-angiotensin-aldosterone system (RAAS) is a key regulator here. When renal perfusion drops, the kidneys release renin, which ultimately produces angiotensin II (a potent vasoconstrictor) and triggers aldosterone release (causing sodium and water retention). This system is the target of several major antihypertensive drug classes you'll study in this unit.

Contributing factors include:

• Genetic susceptibility to blood pressure dysregulation
• Environmental factors such as high sodium intake, obesity, sedentary lifestyle, and chronic stress

Angina occurs when there's a mismatch between myocardial oxygen supply and demand, resulting in ischemia and the characteristic chest pain.

Decreased oxygen supply can result from:

1. Coronary artery stenosis: narrowing from atherosclerotic plaque (the most common cause)
2. Coronary artery spasm: sudden vasoconstriction of a coronary artery (seen in Prinzmetal's/variant angina)
3. Anemia: fewer red blood cells means reduced oxygen-carrying capacity
4. Hypoxemia: low blood oxygen levels from pulmonary or other causes

Increased oxygen demand can result from:

1. Tachycardia: a faster heart rate means the myocardium needs more oxygen per minute
2. Hypertension: higher afterload forces the heart to work harder with each contraction
3. Hypertrophic cardiomyopathy: a thickened ventricular wall requires more oxygen
4. Aortic valve stenosis: the left ventricle must generate more pressure to eject blood through a narrowed valve

Notice that hypertension appears on both sides of this equation: it's a risk factor for atherosclerosis (reducing supply) and it increases cardiac workload (raising demand). That's why treating hypertension is also a strategy for preventing angina.

Blood Pressure Guidelines for Diagnosis

These categories are based on the ACC/AHA guidelines. For diagnosis, BP should be confirmed over multiple visits, not from a single reading.

Pay attention to the "and" vs. "or" distinctions. For normal BP, both numbers must be in range. For Stage 1 and Stage 2, either number being elevated is enough for the diagnosis. A hypertensive crisis requires immediate medical attention regardless of which value is elevated.

Symptoms of Hypertension and Angina

Hypertension is often called the "silent killer" because it's frequently asymptomatic in early stages. That's why routine screening matters so much.

When symptoms do appear, they may include headache, dizziness, shortness of breath, chest pain, blurred vision, and nausea. Clinical signs of chronic hypertension include:

• Elevated BP readings on repeated measurement
• Retinal changes on fundoscopy (arteriovenous nicking, hemorrhages, exudates)
• Left ventricular hypertrophy (detected by an S4 heart sound or displaced apex beat on exam)

Angina presents with chest pain or discomfort, typically described as pressure, squeezing, or fullness in the center of the chest. The pain may radiate to the neck, jaw, shoulder, back, or arm. Associated symptoms include shortness of breath, fatigue, nausea, and lightheadedness.

Clinical signs during an anginal episode can include:

• Elevated heart rate and blood pressure
• S4 gallop (if left ventricular dysfunction is present)
• New mitral regurgitation murmur (if papillary muscle dysfunction occurs from ischemia)

Causes and Diagnosis of Cardiovascular Conditions

Hypertension is classified by cause:

• Primary (essential) hypertension accounts for 90–95% of cases. It's multifactorial, driven by genetics, environment, and behavior. There's no single identifiable cause.
• Secondary hypertension (5–10% of cases) has an identifiable underlying cause. Common culprits include renal artery disease, endocrine disorders (primary aldosteronism, Cushing's syndrome, pheochromocytoma), obstructive sleep apnea, and coarctation of the aorta.

The diagnostic approach for hypertension follows these steps:

1. Confirm elevated BP readings across multiple visits (not just one high reading)
2. Assess for end-organ damage using echocardiogram, renal function tests (BUN, creatinine, GFR), and fundoscopy
3. Evaluate for secondary causes if the clinical picture suggests them (e.g., renal artery ultrasound, aldosterone-to-renin ratio)

Angina causes include obstructive coronary artery disease (the most common), coronary artery spasm (Prinzmetal's angina), microvascular dysfunction, aortic valve stenosis, and hypertrophic cardiomyopathy.

Diagnostic workup for angina:

1. ECG during an episode to detect ST-segment changes or other ischemic patterns
2. Exercise stress test to provoke and identify ischemia under controlled physical exertion
3. Coronary angiography to directly visualize coronary arteries and locate stenosis or blockages
4. Echocardiogram to evaluate heart structure, wall motion abnormalities, and ejection fraction
5. Cardiac MRI for detailed structural and functional assessment when other tests are inconclusive

Cardiovascular Risk Factors and Prevention

Risk factors for both hypertension and angina fall into two categories:

Modifiable risk factors (the ones you can intervene on):

• Hypertension
• Smoking
• Diabetes mellitus
• Dyslipidemia (elevated LDL, low HDL, high triglycerides)
• Obesity
• Physical inactivity

Non-modifiable risk factors:

• Age (risk increases with age)
• Sex (males at higher risk earlier; female risk increases post-menopause)
• Family history of cardiovascular disease

Prevention centers on lifestyle modifications: dietary changes (reduced sodium, the DASH diet), regular physical activity, smoking cessation, weight management, and control of blood glucose and lipids. These strategies reduce myocardial oxygen demand and slow atherosclerotic progression. For many patients, lifestyle changes alone aren't sufficient, which is where the pharmacologic agents covered in the rest of this unit come in.