Coronary Artery Disease (CAD)

This briefing summarizes key information regarding Coronary Artery Disease, covering stable angina pectoris, acute coronary syndromes (ACS), and management in specific patient populations.

I. Stable Angina Pectoris

Definition and Diagnosis: Stable angina pectoris is characterized as "reproducible angina (discomfort or pressure of the chest, neck, or arms) of at least 2 months' duration that is precipitated by a stable level of exertion or emotional stress and is relieved with rest." In contrast, unstable angina is defined by "new-onset angina or angina occurring at a relatively low level of exertion, occurring at rest, or accelerating in frequency or severity," carrying an increased short-term risk for acute myocardial infarction (MI).

The evaluation of angina involves a focused history to elicit details on:

• Anginal Characteristics: Quality, location, radiation, duration, aggravating factors (exertion, anxiety, meals), relieving factors, and associated symptoms (shortness of breath, nausea, diaphoresis).
• Atypical Presentation: Certain groups, including "women and patients with diabetes mellitus, may present only with atypical symptoms, including exertional dyspnea, nausea, or exaggerated fatigue."
• Physical Examination: Focuses on the cardiovascular system and ruling out conditions mimicking angina (e.g., heart failure, pulmonary hypertension, valvular heart disease, hypertrophic cardiomyopathy).
• Diagnostic Testing: The initial step is to determine pretest probability of CAD. Stress testing is used for diagnosis and prognosis. If abnormal, further evaluation is warranted.

General Approach to Treatment: Treatment for stable angina involves a multi-pronged approach, encompassing:

1. Risk Factor Modification: "Regular physical activity, weight loss, tobacco cessation, and dietary changes." Blood pressure control (goal <130/80 mm Hg) and diabetes management are also emphasized.

• Cardioprotective Medications:Aspirin: Low-dose (75-162 mg/d) is recommended for secondary prevention due to similar efficacy and lower bleeding risk compared to high-dose. Clopidogrel is an alternative for aspirin-intolerant patients.
• Lipid-lowering Therapy (Statins): High-intensity statin therapy (atorvastatin 40-80 mg/d or rosuvastatin 20-40 mg/d) is a cornerstone of secondary prevention, significantly reducing MI, death, and stroke. Nonstatin medications (ezetimibe, PCSK9 inhibitors) may be added for statin intolerance or inadequate LDL reduction. Icosapent ethyl provides further risk reduction in high-risk patients with hypertriglyceridemia.
• ACE Inhibitors/ARBs: Indicated in stable angina with concomitant diabetes, chronic kidney disease, LV dysfunction (EF ≤40%), heart failure, or history of MI. ARBs are alternatives for ACE inhibitor intolerance, but combination therapy is not recommended.
• Antianginal Medications:β-Blockers: First-line therapy, reducing heart rate, contractility, and blood pressure, thereby decreasing myocardial oxygen demand. Titration to a resting heart rate of 55-60/min is aimed for. Caution is advised with non-dihydropyridine calcium channel blockers due to additive negative effects.
• Calcium Channel Blockers: Useful as first-line, when symptoms persist despite β-blockers, or when β-blockers are not tolerated. Short-acting dihydropyridines should be avoided. Non-dihydropyridines are contraindicated in LV dysfunction.
• Nitrates: Improve myocardial oxygen delivery and reduce oxygen demand. Short-acting sublingual nitrates are for acute relief. Long-acting nitrates require a nitrate-free interval (8-12 hours) to prevent tolerance. Concurrent use with phosphodiesterase-5 inhibitors is contraindicated due to hypotension risk.
• Ranolazine: Reduces wall tension and myocardial oxygen consumption. Has a modest QT-prolonging effect and interactions with CYP3A4 inhibitors.

Coronary Revascularization: Revascularization aims to "lessen angina and improve quality of life" in stable syndromes. In high-risk cases (left main CAD, large ischemic burden, heart failure), it's indicated for "prevention of future events and improved survival."

• Percutaneous Coronary Intervention (PCI): Catheter-based techniques to relieve coronary obstruction. Drug-eluting stents are preferred. PCI "has not been shown to be superior to guideline-directed medical therapy in reducing the risk for death or MI in patients with stable angina but no anatomic or physiologic criteria for revascularization."
• Coronary Artery Bypass Grafting (CABG): A reasonable option for multivessel CAD, resulting in "decreased recurrence of angina, lower rates of MI, and fewer repeat revascularization procedures compared with PCI or medical therapy alone," especially with arterial conduits. CABG is associated with improved survival in patients with left main or three-vessel CAD and is indicated in those with multivessel disease and diabetes. It also improves 10-year survival in patients with severe LV dysfunction.

After Revascularization:

• Antiplatelet Therapy: Indefinitely after revascularization. Dual antiplatelet therapy (DAPT) with aspirin and a P2Y12 inhibitor is crucial to reduce stent thrombosis and ischemic events. Duration depends on individual risk factors (minimum 1 month for bare metal stents, at least 6 months for drug-eluting stents in stable angina).
• Routine Periodic Testing: "Routine periodic anatomic or ischemic testing without a change in clinical or functional status is not recommended for risk stratification or to guide therapeutic decision making in patients with chronic coronary disease, including for secondary prevention after a coronary revascularization procedure."

II. Acute Coronary Syndromes (ACS)

General Considerations: ACS results from "acute or subacute plaque rupture or erosion and coronary blood flow impairment, manifesting as acute-onset chest pain or an angina equivalent." It's characterized by serum biomarkers of myocardial injury (elevated troponin T or I).

• STEMI vs. NSTE-ACS: Differentiated by ECG findings.
• ST-elevation MI (STEMI): "ST-segment elevation of at least 1 mm in two or more contiguous limb or chest leads" (specific criteria for V2/V3). New bundle branch block may be a STEMI equivalent. STEMI signifies the need for "rapid initiation of reperfusion therapy."
• Non–ST-elevation acute coronary syndrome (NSTE-ACS): Categorized by cardiac injury biomarkers. Non–ST-elevation MI is biomarker-positive without STEMI criteria. Unstable angina is biomarker-negative.
• Mimics of STEMI: Acute pericarditis, acute aortic syndromes, severe hypercalcemia, LV hypertrophy, and supraventricular tachycardias can present with similar ECG findings or symptoms. Careful history, physical exam, and biomarker patterns are crucial for differentiation.

Reperfusion (for STEMI): "Prompt reperfusion with primary PCI (PPCI) or thrombolytic therapy is indicated in all patients with STEMI who do not have limited life expectancy from other nonreversible disease." Shorter reperfusion times correlate with improved outcomes.

• Primary Percutaneous Coronary Intervention (PPCI): Preferred method when available within 90 minutes (first medical contact to PPCI) or 120 minutes (transfer to P...