Master Cardiovascular System
for PLAB 1

Core Concepts

The cardiovascular system's primary role is to circulate blood, delivering oxygen and nutrients while removing metabolic waste. It comprises the heart, blood vessels, and blood.

• Cardiac Output (CO): CO = Heart Rate (HR) x Stroke Volume (SV). Regulated by preload (venous return), afterload (resistance), and contractility.
• Electrical Conduction: Originates at the SA node (pacemaker), propagates through AV node, Bundle of His, Bundle Branches, and Purkinje fibres. Dysfunctions lead to arrhythmias.
• Ischaemic Heart Disease (IHD): Caused by atherosclerosis in coronary arteries. Manifests as stable angina, unstable angina, or myocardial infarction (MI).
• Heart Failure (HF): Inability of the heart to pump sufficient blood. Can be systolic (reduced ejection fraction) or diastolic (impaired filling).
• Valvular Heart Disease: Stenosis (narrowing) or regurgitation (leakage) of heart valves (aortic and mitral most common).
• Arrhythmias: Abnormal heart rhythms (e.g., Atrial Fibrillation, SVT, Ventricular Tachycardia/Fibrillation).
• Hypertension: Persistently elevated systemic blood pressure, a major risk factor for CV events.
• Peripheral Vascular Disease (PVD): Atherosclerosis affecting arteries outside the heart and brain, commonly in the lower limbs.

Clinical Presentation

• Chest Pain: Anginal (retrosternal, constricting, radiating to arm/jaw, exertional, relieved by rest/GTN) vs. non-anginal. Acute MI presents as crushing, severe, prolonged pain.
• Dyspnoea: Exertional dyspnoea, orthopnoea (SOB when lying flat), paroxysmal nocturnal dyspnoea (PND) are hallmarks of heart failure.
• Palpitations: Awareness of one's own heartbeat; can be regular/irregular, fast/slow, associated with anxiety or serious arrhythmias.
• Syncope/Presyncope: Transient loss of consciousness due to global cerebral hypoperfusion; can be vasovagal, orthostatic, or cardiac (e.g., severe aortic stenosis, arrhythmia).
• Oedema: Peripheral (pitting, bilateral in HF), pulmonary (crackles on auscultation, CXR changes).
• Claudication: Muscle pain (classically calf) on exertion, relieved by rest, due to arterial insufficiency (PVD).
• Cough: Persistent, often non-productive cough, worse at night, can be a symptom of left-sided heart failure.

Diagnosis (Gold Standard)

Key diagnostic tools vary by condition but provide crucial information:

• Electrocardiogram (ECG): Essential for arrhythmias, ischaemia (ST changes, T wave inversion), MI (ST elevation, Q waves), hypertrophy.
• Cardiac Biomarkers: Troponin (T/I) for MI diagnosis (rises 3-6h, peaks 12-24h). BNP/NT-proBNP for heart failure.
• Echocardiography (Echo): Gold standard for assessing cardiac structure, valve function, chamber size, and myocardial contractility (ejection fraction).
• Coronary Angiography: Gold standard for diagnosing and assessing severity of coronary artery disease.
• Blood Pressure Measurement: Crucial for diagnosis and monitoring of hypertension.
• Chest X-ray (CXR): Assesses cardiomegaly, pulmonary oedema, pleural effusions in heart failure.
• Doppler Ultrasound: For peripheral vascular disease (ankle-brachial pressure index - ABPI), deep vein thrombosis (DVT).

Management (First Line)

• Acute Coronary Syndrome (ACS): MONA (Morphine, Oxygen, Nitrates, Aspirin), then dual antiplatelet therapy, statins, beta-blockers, ACEi. Reperfusion (PCI or thrombolysis) is critical.
• Heart Failure (HFrEF): Diuretics (symptom relief), ACEi/ARB, Beta-blockers (titrated slowly), Mineralocorticoid Receptor Antagonists (MRA - e.g., spironolactone). Consider SGLT2 inhibitors.
• Hypertension: Lifestyle modification (diet, exercise, salt restriction). First-line drugs: ACEi/ARB, Calcium Channel Blockers (CCB), Thiazide-like diuretics. Beta-blockers for younger patients/specific indications.
• Atrial Fibrillation (AF): Rate control (beta-blockers, CCB) or rhythm control (amiodarone, flecainide). Anticoagulation (DOACs or warfarin) based on CHA2DS2-VASc score to prevent stroke.
• Valvular Heart Disease: Surveillance for mild cases. Surgical repair or replacement for severe, symptomatic, or progressive disease.
• Peripheral Vascular Disease (PVD): Lifestyle modification (smoking cessation, exercise), antiplatelet therapy (aspirin, clopidogrel), statins. Revascularization (angioplasty, bypass surgery) for severe/disabling claudication or critical limb ischaemia.

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