Angina Pectoris/Stable Angina: Pathogenesis and clinical findings
Authors: Ryan Iwasiw Alexander Arnold Julia Gospodinov Reviewers: Mandy Ang Sarah Weeks* Frank Spence* Shahab Marzoughi * MD at time of publication
Atherosclerosis
(Fatty plaque accumulates inside the intimal walls of arteries)
↓ Blood vessel lumen diameter
↓ Volume of blood is supplied to the heart
Predictable period of physical activity or emotional stress
↑ Heart rate
↓ Time for coronary arteries to fill heart with blood (diastole)
↑ Heart contractility
↑ Oxygen demand of heart muscle tissue (myocardium)
↓ Myocardial blood supply
Imbalance between blood supply & oxygen demand causes myocardial ischemia
Angina Pectoris/Stable Angina
Myocardial ischemia causes cardiac muscle cells (cardiomyocytes) to switch from oxygen-dependent (aerobic) to oxygen-absent (anaerobic) metabolism
Anaerobic metabolism produces metabolites that stimulate cardiac spinal afferent nerves
Myocardial visceral afferent & somatic sensory nerve fibers mix & enter the spinal cord via T1-T4 nerve roots
Brain interprets ↑ nerve signaling as nerve pain coming from the skin of T1-T4 dermatomes (referred pain)
↑ lactic acid production & ↓ cellular pH impairs cardiomyocytes’ function
Damaged cardiomyocytes impair myocardial relaxation & cause ↓ left ventricular contractility & cardiac output
Blood backs up into left ventricle, atrium, & pulmonary vasculature
↑ Pulmonary capillary pressures pushes fluid out & into the lung’s alveoli
↓ Gas exchange & oxygenation
↑ Respiratory rate & Dyspnea (shortness of breath)
Blood flow begins at the epicardium (outer heart layer) & ends at endocardium (inner layer)
Subendocardium (innermost heart layer) receives the least blood flow causing non-transmural (partial thickness) heart wall ischemia
Anterior/septal & lateral wall ischemia triggers ↑ sympathetic nervous system (SNS) activity given the proximity of cardiac SNS innervation
Inferior wall ischemia triggers involuntary ↑ in Vagus nerve activity given the nerve’s proximity
Bradycardia (↓ heart rate)
Nausea
Adrenal medulla releases Norepinephrine hormone
Activation of sweat glands via SNS acetylcholine neurotransmitter release
Hypotension (↓ blood pressure)
Pain radiation to left arm, jaw, abdomen & upper back
Chest pain, pressure, or discomfort
Unstable Angina (unpredictable & worsening chest pain)
See relevant Calgary Guide slide on Unstable Angina
Binds arterial smooth muscle α1 receptors
↑ Coronary arteries’ vascular tone (vasoconstriction)
Hypertension (↑ blood pressure)
Activates β1 receptors in the heart
Tachycardia (↑ heart rate)
Diaphoresis (↑ sweating)
Legend:
Pathophysiology
Mechanism
Sign/Symptom/Lab Finding
Complications
Published Aug 8, 2013; updated Feb 5, 2024 on www.thecalgaryguide.com