Atherosclerosis and Chronic Stable Angina

Atherosclerotic Plaque Formation

• Endothelial dysfunction initiates atherosclerosis through impaired vasodilatory capacity and increased permeability to lipoproteins, driven by shear stress, smoking, hypertension, and hyperglycemia
• Low-density lipoprotein (LDL) oxidation within the subendothelial space activates scavenger receptors on macrophages, leading to foam cell formation—the hallmark of early atherosclerotic lesions (fatty streaks)
• Smooth muscle cell migration from the media into the intima occurs in response to platelet-derived growth factor (PDGF) and fibroblast growth factor (FGF), creating a fibrous cap that stabilizes the plaque

Ischemic Mechanism in Stable Angina

• Fixed stenosis (typically ≥70% diameter reduction in epicardial coronaries) reduces maximal coronary blood flow (coronary flow reserve becomes impaired), preventing appropriate increase in myocardial oxygen delivery during increased metabolic demand
• Supply-demand mismatch occurs when myocardial oxygen demand (determined by heart rate, contractility, and wall tension) exceeds oxygen supply, causing reversible subendocardial ischemia (predominantly affecting the subendocardium due to higher metabolic demand and lower perfusion pressure)
• Coronary autoregulation maintains constant coronary blood flow across a wide range of perfusion pressures; however, with significant stenosis, vessels distal to the obstruction lose the ability to vasodilate and maintain adequate perfusion during stress

Collateral Development

• Arteriogenesis (formation of mature collateral vessels) occurs in response to chronic ischemia and hemodynamic forces, potentially providing alternative perfusion pathways that can partially compensate for severe stenosis and reduce anginal frequency

Major Modifiable Risk Factors

• Dyslipidemia (elevated LDL, low HDL, elevated triglycerides)—LDL is directly atherogenic; each 39 mg/dL reduction in LDL decreases major vascular events by ~22%
• Hypertension—damages endothelium and promotes atherosclerotic plaque progression; target BP <130/80 mmHg in coronary disease
• Cigarette smoking—causes endothelial dysfunction, increases thrombosis, oxidizes LDL; smoking cessation is the single most impactful intervention
• Diabetes mellitus—accelerates atherosclerosis through glycation of LDL, endothelial dysfunction, and enhanced inflammation; glycemic control reduces microvascular but not macrovascular events
• Obesity and metabolic syndrome—associated with insulin resistance, dyslipidemia, and chronic inflammation
• Physical inactivity—exercise reduces anginal frequency and improves coronary flow reserve

Non-Modifiable Risk Factors

• Age and sex—men aged ≥45 years and postmenopausal women; estrogen appears cardioprotective
• Family history of premature coronary disease—first-degree relative with MI before age 55 (men) or 65 (women)
• Genetic dyslipidemia (familial hypercholesterolemia, familial combined hyperlipidemia)

Other Contributing Factors

• Chronic inflammatory states (rheumatoid arthritis, systemic lupus erythematosus, chronic kidney disease)
• Thrombophilia and elevated lipoprotein(a)
• Sleep apnea and psychosocial stress

Cardinal Symptom: Anginal Chest Discomfort

• Quality: Described as pressure, heaviness, tightness, or squeezing; patients often use clenched-fist sign to describe location
• Location: Substernal, with classic radiation to left arm, jaw, or epigastrium; right arm involvement less common but still significant
• Duration: Typically 3–15 minutes; episodes lasting >30 minutes suggest acute coronary syndrome or alternative diagnosis
• Triggers: Predictable exertional component (walking uphill, sexual activity, cold weather); emotional stress; heavy meals
• Relief: Rest or sublingual nitrates provide relief within 5–15 minutes

Associated Symptoms

• Dyspnea—anginal equivalent (especially in elderly, women, and diabetics); may be sole presenting symptom
• Diaphoresis, nausea, palpitations—reflect sympathetic activation

Atypical Presentations

• Women and elderly: More likely to present with dyspnea, fatigue, nausea, or jaw pain; studies demonstrate worse outcomes due to delayed diagnosis
• Diabetics: Increased prevalence of silent ischemia due to autonomic neuropathy

Physical Examination

• Often normal at rest; findings only appear during or immediately after anginal episode
• Transient S4 gallop (reflecting reduced LV compliance from acute ischemia)
• Transient systolic murmur of mitral regurgitation (papillary muscle dysfunction during ischemia)
• Signs of heart failure: Elevated JVP, rales, peripheral edema (suggests ischemic cardiomyopathy)
• Aortic stenosis stigmata: Slow carotid upstroke, late-peaking systolic murmur (important differential diagnosis and independent CAD risk factor)
• Xanthomas and corneal arcus: Suggest familial hypercholesterolemia
• Absent femoral pulses: Peripheral arterial disease (associated with higher CAD prevalence)

Clinical Assessment: Canadian Cardiovascular Society (CCS) Grading of Angina

• Class I: Angina with strenuous exertion only
• Class II: Slight limitation of ordinary activities
• Class III: Marked limitation; angina with minimal exertion
• Class IV: Angina at rest (severe, unstable; requires acute evaluation)

Electrocardiography (ECG)

• Baseline ECG: Normal in ~50% of patients with stable angina; essential to document for comparison
• During angina: ST-segment depression (most common; ≥1 mm in ≥2 contiguous leads suggests ischemia), T-wave inversion, or ST elevation (less common in stable angina)
• Posterior MI pattern: ST elevation in V1-V2 may reflect posterior wall ischemia (compare to posterior leads V7-V9)
• Value: Localizes ischemia anatomically; serial ECGs detect new changes

Exercise Stress Testing (EST)

• Indications: Intermediate-risk patients with interpretable baseline ECG; assess functional capacity and inducible ischemia
• Positive test criteria:
• ≥1 mm ST depression in ≥2 contiguous leads
• ST elevation in non-Q-wave leads
• Symptom reproduction with hemodynamic changes
• Downsloping or horizontal ST changes (higher risk than upsloping)
• Interpretation: Diagnostic accuracy ~85%; limited in patients with baseline ST changes (LVH, LBBB, digoxin use), female sex, and pre-excitation
• Prognosis: Deeply positive tests (early ST depression with high-risk morphology, failure to increase BP, or exercise-induced hypotension) indicate worse outcomes

Coronary Imaging: Stress Testing with Imaging (Preferred in Many Scenarios)

• Stress echocardiography (exercise or dobutamine): Detects regional wall motion abnormalities during ischemia; superior sensitivity/specificity (~85–90%); useful with abnormal baseline ECG
• Myocardial perfusion imaging (MPI) with technetium-99m or thallium-201: Identifies reversible perfusion defects reflecting ischemia; normalcy rate ~95%; can quantify extent of ischemia and LV function
• SPECT imaging limitations: Lower specificity in women (breast attenuation artifact) and fixed defects from prior MI
• PET imaging (with adenosine or rubidium-82): Gold standard for quantifying coronary flow reserve; reserved for select cases due to cost

Coronary Computed Tomography Angiography (CCTA)

• High sensitivity (>95%) and negative predictive value for excluding significant CAD; excellent for low-to-intermediate risk patients
• Advantages: Non-invasive, rapid, provides information on plaque composition and coronary calcification
• Limitations: Lower specificity (~65–80%) for intermediate stenosis; overestimates severity in calcified vessels; radiation exposure; not suitable for acute evaluation

Biomarkers

• Troponin (I or T): Normal in stable angina; elevation suggests acute coronary syndrome
• B-type natriuretic peptide (BNP): Elevated if concurrent heart failure (poor prognostic sign)
• High-sensitivity C-reactive protein (hsCRP): Marker of inflammation; associated with increased risk but not routinely recommended for risk stratification alone

Coronary Angiography (Invasive)

• Gold standard for defining coronary anatomy and stenosis severity (>70% diameter reduction is hemodynamically significant for most vessels)
• Indications:
• High-risk findings on non-invasive testing
• Severe symptoms uncontrolled on medical therapy
• Equivocal non-invasive results in high-risk patients
• Assessment of LV function and hemodynamics
• Fractional flow reserve (FFR): Pressure-derived measure of stenosis significance; FFR ≤0.80 indicates functional ischemia; guides revascularization decisions for intermediate stenosis (50–70%)
• IVUS or OCT: Allows detailed plaque characterization; identifies high-risk morphology

Diagnostic Algorithm

1. 1.Clinical assessment + baseline ECG → Determines pre-test probability
2. 2.Low probability, no ischemic changes: Reassurance; lifestyle modification
3. 3.Intermediate probability: Stress testing (exercise if able; imaging if baseline ECG abnormal)
4. 4.High probability or high-risk stress test: Coronary angiography
5. 5.Positive angiography: Assess for revascularization based on symptom severity and ischemic burden

First-Line Medical Therapy: Anti-Anginal Agents

Beta-Blockers

• Mechanism: Reduce myocardial oxygen demand by decreasing heart rate, contractility, and BP
• Agents: Metoprolol, atenolol, carvedilol (non-selective agents preferable for CAD)
• Target: Resting heart rate 55–60 bpm; titrate until symptom control or adverse effects
• Evidence: Reduce anginal frequency by ~70%; improve exercise tolerance; prognostic benefit post-MI
• Contraindications: Severe bradycardia, AV block, decompensated heart failure, severe COPD/asthma
• Adverse effects: Fatigue, sexual dysfunction, bronchospasm, masks hypoglycemia in diabetics

Calcium Channel Blockers (CCBs)

• Mechanism: Dilate coronary arteries and peripheral vasculature; reduce contractility
• Agents:
• Dihydropyridines (amlodipine, nifedipine)—potent vasodilators; reflex tachycardia; use with beta-blocker
• Non-dihydropyridines (diltiazem, verapamil)—negative inotropes; rate-slowing; safer if combined with beta-blocker
• Evidence: Reduce angina ~70%; non-inferiority to beta-blockers
• Caution: Avoid dihydropyridines as monotherapy (reflex tachycardia increases demand); verapamil and diltiazem contraindicated with concurrent beta-blocker if baseline bradycardia or AV block

Nitrates

• Mechanism: Vasodilate large epicardial coronary arteries and peripheral vasculature; reduce preload and wall tension (demand reduction)
• Acute relief: Sublingual nitroglycerin (onset 2–3 minutes, duration 30 minutes)
• Long-acting agents: Isosorbide dinitrate, isosorbide mononitrate patches (sustained-release formulations)
• Tolerance: Develops with continuous exposure; mitigated by 12-hour nitrate-free interval daily
• Adverse effects: Headache, reflex tachycardia (mitigate with beta-blocker), hypotension; contraindicated with phosphodiesterase-5 inhibitors (sildenafil, tadalafil)—risk of profound hypotension

Second-Line Anti-Anginal Agents

Ivabradine

• Mechanism: Selective inhibitor of sinoatrial node current (If); reduces heart rate without negative inotropic effect
• Indication: Symptomatic CAD in sinus rhythm; contraindicated in decompensated heart failure
• Advantage: No interaction with sexual dysfunction medications (unlike beta-blockers)

Ranolazine

• Mechanism: Partially inhibits myocardial fatty acid oxidation; shifts metabolism toward glucose; reduces intracellular calcium overload and ischemic dysfunction
• Indication: Refractory angina as add-on therapy
• Note: Does not reduce BP or heart rate; no mortality benefit; modest symptom improvement

Trimetazidine

• Mechanism: Inhibits mitochondrial long-chain 3-ketoacyl-CoA thiolase, reducing fatty acid oxidation
• Indication: Refractory angina (less commonly used in US)

Antiplatelet and Anticoagulant Therapy

Aspirin

• Dose: 75–100 mg daily (lower doses equivalent to higher in CAD)
• Mechanism: Irreversible COX-1 inhibition; reduces thromboxane A2 and platelet aggregation
• Benefit: Reduces MI and vascular death by ~25% (NNT ~67 over 2 years)
• Contraindication: Active bleeding, aspirin allergy

P2Y12 Inhibitors

• Indications: Generally not used in stable angina unless recent acute coronary syndrome or revascularization
• Agents (if indicated): Clopidogrel, prasugrel, ticagrelor
• Duration: Typically 12 months post-ACS or post-PCI

Anticoagulation

• Indication: Reserved for acute coronary syndromes or concurrent atrial fibrillation
• Not routinely used in stable angina without these additional indications

Lipid-Lowering Therapy

Statins (Primary Therapy)

• Agents: Atorvastatin 40–80 mg daily, rosuvastatin 20–40 mg daily (high-intensity), pravastatin 40 mg daily, simvastatin 40 mg daily (moderate-intensity)
• Target LDL: <70 mg/dL for CAD patients; <55 mg/dL in very-high-risk patients (recurrent events)
• Mechanism: HMG-CoA reductase inhibition; reduce cholesterol synthesis, plaque progression, and inflammation
• Evidence: Reduce major vascular events by ~30% over 2 years; reduce mortality
• Adverse effects: Myalgia (rare true myositis), elevated transaminases, new-onset diabetes (rare); monitor CK and LFTs at baseline and if symptomatic

PCSK9 Inhibitors

• Indications: Inadequate LDL lowering on maximal statin ± ezetimibe; familial hypercholesterolemia; very-high-risk patients
• Agents: Evol

Complications of the disease

• Acute coronary syndrome (EMERGENCY): rupture or erosion of a thin-capped, lipid-rich plaque exposes tissue factor and collagen → platelet adhesion and thrombus. Signaled by pain at rest, pain lasting >20–30 minutes, or a change in the patient's usual anginal pattern; new ST deviation and rising high-sensitivity troponin distinguish it from stable angina. Activate the ACS pathway per the ACC/AHA chest pain and ACS guidelines.
• Sudden cardiac death (EMERGENCY): ischemia creates dispersion of repolarization and reentry, most often ventricular fibrillation / pulseless VT — the shockable rhythms requiring immediate defibrillation under AHA ACLS.
• Ischemic cardiomyopathy / HFrEF: repetitive ischemia, infarct scar, and adverse remodeling drop EF. Signaled by exertional dyspnea, S3, elevated JVP, and elevated BNP; treat with the four guideline-directed classes per the AHA/ACC/HFSA heart failure guideline — ARNI (or ACEI/ARB), beta blocker, MRA, and SGLT2 inhibitor.
• Ischemic mitral regurgitation: papillary muscle dysfunction or annular dilation → new apical holosystolic murmur, pulmonary edema.
• Arrhythmia and conduction disease: scar-based monomorphic VT, atrial fibrillation, or AV block from nodal artery ischemia.
• Systemic atherosclerosis: the same plaque biology yields stroke/TIA, peripheral artery disease with claudication, renal artery stenosis, and abdominal aortic aneurysm.

Complications of therapy

• Nitrate–PDE5 inhibitor interaction (EMERGENCY): additive cGMP accumulation → refractory hypotension; do not give nitrates within about 24 hours of sildenafil or 48 hours of tadalafil.
• Stent thrombosis (EMERGENCY): abrupt occlusion, usually from premature antiplatelet discontinuation, presents as STEMI; in-stent restenosis instead causes gradual recurrence of exertional angina over months.
• Statin myopathy: myalgias with normal CK are common; rhabdomyolysis with markedly elevated CK and pigmenturia is rare and drug-interaction driven.
• Bradyarrhythmia: verapamil or diltiazem plus a beta blocker → symptomatic bradycardia or high-grade AV block.
• Bleeding: aspirin-related GI hemorrhage; retroperitoneal hematoma after femoral access (flank pain, unexplained hypotension, falling hematocrit).
• Other: contrast-associated acute kidney injury after angiography; ranolazine QT prolongation; ivabradine visual phosphenes; post-CABG atrial fibrillation, stroke, and late graft failure.

• The typical angina triad: substernal discomfort, provoked by exertion or emotional stress, relieved by rest or nitroglycerin. All three = typical; two = atypical; one or none = noncardiac. The clenched-fist (Levine) sign over the sternum is the classic buzzword.
• Single best first step in any stable chest pain stem: a resting 12-lead ECG (plus lipid panel, glucose/A1c, hemoglobin, TSH as indicated). A normal resting ECG never excludes CAD — roughly half of stable angina patients have one.
• Revascularization does not prolong life in stable disease: per the 2023 AHA/ACC chronic coronary disease guideline, informed by COURAGE and ISCHEMIA, PCI added to optimal medical therapy improves angina and quality of life but not death or MI. The exam-tested exception is anatomy with a survival benefit from surgery — left main disease, or multivessel disease with reduced EF or diabetes (FREEDOM favors CABG over PCI in diabetics).
• Separate disease-modifying from symptom-modifying drugs: aspirin and high-intensity statin change outcomes; nitrates, ranolazine, and ivabradine only relieve symptoms. Add an ACE inhibitor or ARB when hypertension, diabetes, CKD, or LVEF ≤40% coexists.
• The one association examiners love: diabetes + autonomic neuropathy → silent ischemia, so an elderly diabetic presenting with isolated exertional dyspnea or nausea is an anginal equivalent, not GERD.
• Choose the stress test by the baseline ECG: LBBB, ventricular pacing, LVH with repolarization change, or digoxin effect make exercise ECG uninterpretable — use vasodilator myocardial perfusion imaging (avoid the exercise-only answer). If the patient cannot exercise, use pharmacologic stress; avoid adenosine/dipyridamole in active bronchospasm.
• Distractor to avoid — vasospastic (Prinzmetal) angina: rest or nocturnal pain with transient ST elevation and nonobstructed arteries. Calcium channel blockers are first line; beta blockers can worsen it by leaving alpha-mediated vasoconstriction unopposed.
• Second distractor: short-acting dihydropyridine monotherapy (immediate-release nifedipine) causes reflex tachycardia and can worsen angina — never the best answer.