cardiovascular

These lectures are actually one connected story:

  1. The heart pumps blood

  2. Blood pressure must be controlled

  3. The kidneys help regulate blood pressure

  4. High blood pressure damages vessels/organs

  5. This contributes to heart failure + kidney disease

  6. Drugs target these mechanisms

That’s basically the whole topic.

WHAT IS CARDIOVASCULAR DISEASE?

Definition

Diseases affecting:

  • heart
    AND/OR

  • blood vessels

MAIN RISK FACTORS

  • hypertension

  • smoking

  • diabetes

  • obesity

  • inactivity

  • high cholesterol

  • age

  • family history

COMMON CARDIOVASCULAR DISEASES

  • coronary artery disease

  • myocardial infarction (heart attack)

  • stroke

  • heart failure

  • arrhythmias

  • aneurysms

  • peripheral vascular disease

  • chronic kidney disease

THE HEART

Four chambers

  • right atrium

  • right ventricle

  • left atrium

  • left ventricle

TWO PHASES OF CARDIAC CYCLE

Systole

Heart contracts/pumps.

Diastole

Heart relaxes/fills.

STROKE VOLUME

Definition

Amount of blood pumped per heartbeat.

Typical:
≈ 100 mL

HEART RATE

Typical adult:
≈ 60 bpm

CARDIAC OUTPUT

Definition

Amount of blood pumped per minute.

Formula:

CO = HR \times SV

Typical:

  • 60 × 100 mL
    ≈ 6 L/min

BLOOD PRESSURE

Definition

Force of blood against arterial walls.

Depends on:

  1. cardiac output

  2. systemic vascular resistance

SYSTEMIC VASCULAR RESISTANCE (SVR)

Definition

Resistance to blood flow in circulation.

Vasoconstriction

Blood vessels narrow →

SVR increases →

blood pressure rises.

Vasodilation

Blood vessels widen →

SVR decreases →

blood pressure falls.

NORMAL BLOOD PRESSURE

Typical healthy adult:

120/80\ mmHg

SYSTOLIC VS DIASTOLIC PRESSURE

Systolic

Pressure during contraction.

Diastolic

Pressure during relaxation.

BLOOD PRESSURE CONTROL

Main organs involved:

  • kidneys

  • heart

  • arteries

  • brain

MOST IMPORTANT:

  • kidneys

THE KIDNEY

Main functions

  • filter blood

  • remove toxins

  • regulate water

  • regulate electrolytes

  • help control blood pressure

NEPHRON

Functional unit of kidney.

Main parts:

  • glomerulus

  • Bowman’s capsule

  • renal tubule

RAAS (RENIN-ANGIOTENSIN-ALDOSTERONE SYSTEM)

MOST IMPORTANT EXAM TOPIC.

WHAT TRIGGERS RAAS?

Low blood pressure →

reduced kidney perfusion →

reduced sodium delivery →

macula densa detects change →

RAAS activated.

RAAS SEQUENCE

1. Renin released

2. Renin converts:

Angiotensinogen \rightarrow Angiotensin\ I

3. ACE converts:

Angiotensin\ I \rightarrow Angiotensin\ II

4. Angiotensin II effects

Vasoconstriction

Raises blood pressure.

Aldosterone release

Kidneys retain:

  • sodium

  • water

Raises blood volume and BP.

HYPERTENSION

Definition

BP > 140/90\ mmHg

IMPORTANT POINT

Often:

  • asymptomatic

But still causes organ damage.

CONSEQUENCES OF HYPERTENSION

  • stroke

  • heart attack

  • heart failure

  • aneurysms

  • CKD

  • arrhythmias

HEART FAILURE

Definition

Heart too weak or stiff to pump sufficient blood.

COMMON CAUSES

  • ischaemic heart disease

  • hypertension

  • valvular disease

  • diabetes

HEART FAILURE FEATURES

  • breathlessness

  • fluid retention

  • oedema

  • weakness

  • dizziness

  • chest pain

IMPORTANT TESTS

Blood test

NT-proBNP

Imaging

Echocardiogram.

CHRONIC KIDNEY DISEASE (CKD)

Definition

Reduced kidney function or kidney damage for >3 months.

COMMON CAUSES

  • diabetes

  • hypertension

  • vascular disease

  • inflammatory disease

CKD FEATURES

  • fluid retention

  • weakness

  • breathlessness

IMPORTANT TESTS

eGFR

Measures kidney function.

Urine protein

Checks kidney damage.

IMPORTANT LINK

Heart failure and CKD commonly occur together because both involve:

  • vascular damage

  • RAAS activation

  • fluid retention

OEDEMA

Definition

Fluid accumulation.

LEG OEDEMA

Peripheral swelling.

PULMONARY OEDEMA

Fluid in lungs →
breathlessness.

DIURETICS

Function

Remove excess water.

LOOP DIURETICS

Act on:

  • loop of Henle

Block:

  • sodium reabsorption

  • potassium reabsorption

Result:

  • less water reabsorbed

  • more urine produced

Used in:

  • heart failure

  • CKD

ACE INHIBITORS

Mechanism

Block ACE enzyme.

Prevent:

Angiotensin\ I \rightarrow Angiotensin\ II

EFFECTS

  • less vasoconstriction

  • less aldosterone

  • less salt/water retention

  • lower BP

ARBs (ANGIOTENSIN RECEPTOR BLOCKERS)

Mechanism

Block effects of Angiotensin II.

Similar effects to ACE inhibitors.

BIG EXAM COMPARISONS

Drug

Main effect

Diuretics

Remove water

ACE inhibitors

Block ACE/RAAS

ARBs

Block Ang II effects

MOST IMPORTANT EXAM CONTENT

Prioritise:

  • cardiac output

  • systole vs diastole

  • blood pressure

  • SVR

  • RAAS sequence

  • hypertension

  • heart failure

  • CKD

  • oedema

  • diuretics

  • ACE inhibitors

  • ARBs

ENTIRE CVS TOPIC IN ONE FLOW

Heart pumps blood →

cardiac output generates blood pressure →

kidneys regulate BP using RAAS →

RAAS increases vasoconstriction + water retention →

chronic hypertension damages vessels/organs →

heart failure + CKD develop →

fluid retention/oedema occurs →

diuretics remove fluid →

ACE inhibitors/ARBs block RAAS and lower BP.