G6 SYL2017 / 17A15: Outline the cardiovascular changes with morbid obesity

17A15: Exam Report

Outline the cardiovascular changes associated with morbid obesity.

42% of candidates passed this question.

Many candidates did not include enough detail in their answers.

Higher scoring answers included more depth such as the following: blood volume, left ventricular changes, arterial blood pressure, pulmonary artery pressures, risks of ischaemia, arrhythmias etc.

G6 SYL2017 / 17A15: Outline the cardiovascular changes with morbid obesity

Definitions

Obesity = condition of excess body fat

BMI > 30kg/m2

CVS Consequences

HTN

  • X 10 more common
  • Multifactorial
    • ↑blood vol → ↑CO → ↑BP
    • Hyperinsulinaemia → activates SNS → ↑Na+ reabsorption → BP

IHD

    • ↑Cholesterol
    • HTN
    • DM
    • (Above are compounding factors)

NB: obesity is an independent RF for IHD

↑ Blood Volume & CO

  • Due to ↑metabolic demands of fat tissue
  • Extra blood vol is distributed to the fat tissue (cerebral & renal BF unchanged)
  • ↑O2 consumption & CO2 production despite ↑CO

Cardiac Arrhythmias

      • Precipitation is multifactorial
        • Tissue hypertrophy/dilatation
        • Hypoxia
        • ↓K+ from diuretics
        • CAD
        • ↑Catecholamines
        • Fatty infiltration of conducting tissue

Cardiac Dysfunction

    • LVH
    • ↑LV wall thickness & myocyte size
    • Hypertrophy to compensate for ↑CO
    • ↑LV size & dilatation → ↑LV wall stress as per Law of LaPlace:
Wall Tension Afferent
    • LV Systolic Dysfunction
    • ↑Wall stress from LVH → contributes to systolic dysfunction
    • Impaired LV Diastolic Filling & ↑LV filling pressure
    • LVEDP → most specific measure for LV diastolic function
    • LV hypertrophy predisposes to impaired diastolic filling & ↑pressures
    • LA dilatation
    • ↑LA size 2° impaired LV filling
    • PA Hypertension
    • OSA → ↑CO2/↓O2 → RV enlargement → RV failure
Obesity2