Ischaemic Heart Disease (IHD) for PLAB 1
Ischaemic Heart Disease (IHD), also known as coronary artery disease (CAD), is a leading cause of morbidity and mortality worldwide. Understanding its pathophysiology, clinical presentation, diagnosis, and management is crucial for PLAB 1 preparation. This module will cover the core knowledge required.
Pathophysiology: The Atherosclerotic Process
IHD is primarily caused by atherosclerosis, a chronic inflammatory disease characterized by the buildup of plaque within the walls of arteries. This plaque formation narrows the arteries, reducing blood flow to the heart muscle (myocardium). The key steps involve endothelial dysfunction, lipid accumulation, inflammatory cell infiltration, and plaque rupture.
Risk Factors for Ischaemic Heart Disease
| Modifiable Risk Factors | Non-Modifiable Risk Factors |
|---|---|
| Hypertension | Age |
| Hyperlipidemia (High Cholesterol) | Family History of Early CAD |
| Diabetes Mellitus | Male Sex |
| Smoking | |
| Obesity | |
| Physical Inactivity | |
| Unhealthy Diet |
Understanding and managing modifiable risk factors is a cornerstone of IHD prevention and treatment.
Clinical Manifestations of IHD
The clinical presentation of IHD varies depending on the severity and chronicity of the underlying atherosclerosis and the degree of myocardial ischemia.
Stable Angina
Characterized by predictable chest pain or discomfort (angina pectoris) that occurs with exertion or emotional stress and is relieved by rest or nitroglycerin. It's typically described as a pressure, tightness, or squeezing sensation in the chest, often radiating to the left arm, jaw, or back. This occurs when the heart's demand for oxygen exceeds its supply during increased activity.
Unstable Angina
A more serious form where angina occurs at rest, is new-onset, or is increasing in frequency or severity. It indicates a higher risk of imminent myocardial infarction.
Myocardial Infarction (Heart Attack)
Occurs when blood flow to a part of the heart muscle is severely reduced or blocked, causing irreversible damage to the myocardium. Symptoms can include severe, prolonged chest pain (often not relieved by rest or nitroglycerin), shortness of breath, sweating, nausea, and dizziness. STEMI (ST-elevation myocardial infarction) and NSTEMI (non-ST-elevation myocardial infarction) are key classifications.
Stable angina is predictable and occurs with exertion, relieved by rest. Unstable angina is unpredictable, occurs at rest, or is increasing in severity, indicating a higher risk of MI.
Diagnosis of Ischaemic Heart Disease
Diagnosis involves a combination of patient history, physical examination, electrocardiogram (ECG), cardiac biomarkers, and further investigations.
The electrocardiogram (ECG) is a vital diagnostic tool for IHD. Key findings in acute myocardial infarction include ST-segment elevation (STEMI), ST-segment depression, T-wave inversion, and Q waves. These changes reflect the electrical activity of the heart muscle and indicate areas of ischemia or infarction. For example, ST elevation in specific leads suggests infarction in a particular region of the myocardium supplied by a specific coronary artery.
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Cardiac biomarkers, such as troponin I and troponin T, are released into the bloodstream when heart muscle is damaged. Elevated levels are highly specific for myocardial infarction. Other investigations may include echocardiography, stress testing (exercise ECG or pharmacological stress with imaging), and coronary angiography for definitive assessment of coronary artery stenosis.
Management of Ischaemic Heart Disease
Management strategies aim to relieve symptoms, prevent further ischemic events, and improve prognosis. This includes lifestyle modifications, medical therapy, and revascularization procedures.
Medical Management
Key medications include:
- Antiplatelets: Aspirin, clopidogrel (to prevent clot formation).
- Beta-blockers: Reduce heart rate and blood pressure, decreasing myocardial oxygen demand.
- Statins: Lower cholesterol levels and stabilize plaques.
- ACE inhibitors/ARBs: Reduce blood pressure and protect the heart.
- Nitrates: Vasodilators to relieve angina symptoms.
Revascularization Procedures
For significant coronary artery disease, procedures like Percutaneous Coronary Intervention (PCI) with stenting or Coronary Artery Bypass Grafting (CABG) surgery may be indicated to restore blood flow to the myocardium.
Antiplatelets (e.g., Aspirin), Beta-blockers, and Statins are common examples.
Complications of IHD
Potential complications include heart failure, arrhythmias (e.g., atrial fibrillation, ventricular tachycardia), valvular heart disease, and sudden cardiac death.
Learning Resources
Provides a comprehensive overview of ischaemic heart disease, its causes, symptoms, and treatments from a reputable health service.
Details the symptoms, causes, risk factors, and diagnosis of coronary artery disease, offering a patient-centric perspective.
An accessible explanation of CAD, its impact on the heart, and how it develops, from a leading cardiovascular health organization.
A detailed medical reference for healthcare professionals covering the pathophysiology, diagnosis, and management of myocardial infarction.
A comprehensive resource for learning ECG interpretation, with specific sections on identifying changes related to myocardial infarction.
Official clinical guidelines from the UK's National Institute for Health and Care Excellence on the management of stable angina.
An educational video explaining the process of atherosclerosis in a clear and understandable manner.
An in-depth review of cardiac biomarkers, their role in diagnosing MI, and their interpretation, suitable for advanced understanding.
While not directly providing questions, this link leads to official information about the PLAB exam, often a starting point for finding practice materials or understanding exam structure.
Compares and contrasts two major revascularization procedures for IHD, explaining when each might be recommended.