Chapter 1-04: Diseases and Pathophysiology in Cardiology

ISCHEMIC HEART DISEASE

Stable coronary artery disease (CAD)

• Types: Asymptomatic CAD or stable angina (angina that occurs reliably with exertion and emotional stress, relived with rest or nitroglycerin; due to fixed atherosclerosis)

• Diagnosis: Stress testing; computed tomography angiography (CCTA) vs. invasive coronary angiogram to assess anatomy

• Workup: HgA1c, lipid panel, ECG, TTE to assess LV function

• Treatment:

  • - Address risk factors and disease pathology:

    • Smoking cessation

    • Exercise/weight loss/diet

    • Control hypertension (goal at least <140/90 mmHg), ACEi (or ARB if intolerant of ACEi)

    • Treat DM (preferably with SGLT2 inhibitors or GLP-1 agonists)

    • Treat HLD, start statin (e.g., atorvastatin, rosuvastatin; goal LDL <70 mg/dL)

      • - Consider addition of ezetimibe if LDL not at goal (IMPROVE-IT 2015)

      • - Consider addition of PCSK9 inhibitor if LDL still not at goal and/or family history (FOURIER 2018)

      • - Consider addition of icosapent ethyl if fasting triglycerides >135 mg/dL in patients with known CAD or DM (REDUCE-IT 2019)

    • Aspirin (particularly if prior ACS event)

    • Beta blocker (BB) (particularly if prior ACS event)

  • - Address symptoms (antianginal therapy for stable angina):

    • Beta blocker (BB): Increases coronary blood supply (↓HR → ↑coronary diastolic filling time → ↑blood supply) and decreases myocardial demand (↓contractility → ↓wall stress/O₂ demand)

    • Calcium channel blocker (CCB): If second agent required; similar mechanism as BB

    • Nitrates: Vasodilation of coronary arteries; venodilation → ↓preload → ↓wall stress/O₂ demand

      • - Nitroglycerin (sublingual/transdermal/spray; taken as needed)

      • - Isosorbide dinitrate (oral; taken BID or TID)

      • - Isosorbide 5-mononitrate (oral; taken daily or BID)

    • Ranolazine: Inhibits late inward sodium current in ischemic myocytes (Phase 0) → ↓Ca²⁺ overload → ↓wall stress/O₂ demand and ↑coronary blood flow.

    • Revascularization: Consider in patients who are symptomatic despite optimal medical therapy; only revascularize physiologically significant lesions as identified by stress testing or fractional flow reserve (FAME 2 2012; ISCHEMIA 2020).

      • - EXCEPTIONS: Revascularization has mortality benefit in:

        • Significant left main disease (i.e., >50% stenosis LAD): All patients should be revascularized; CABG vs. PCI depends on anatomic complexity and surgical candidacy; decision should be made after multidisciplinary review.

        • Significant 3-vessel CAD (i.e., >70% stenosis in 3 vessels): All patients should be revascularized; CABG preferred to PCI in patients who are good surgical candidates (SYNTAX 2009), especially in patients with diabetes (FREEDOM 2012).

        • HFrEF: Consider revascularization, especially if severe CAD or viable myocardium (limited data, though may have long-term benefit).

Myocardial infarction

• Type I MI: Spontaneous MI (aka acute coronary syndrome from thrombus in a coronary artery) (Figure 1.13)

  • - ACS without ST elevation (NSTEMI)

    • NSTEMI: Subendocardial ischemia

      • - Criteria: Rise and/or fall in troponin (Table 1.6) AND at least one of the following:

        • Symptoms of acute myocardial ischemia

        • New ischemic ECG changes (e.g., significant ST-T changes or LBBB)

        • Development of pathologic Q waves

        • Imaging evidence of loss of myocardial function ...