Canonical Question
CVS – Responses
Master answer
Obesity
- excessive fat accumulation in adipose tissue
- WHO classification based on BMI (weight in kg/ height in m2)
| BMI | |
|---|---|
| Underweight | <18.5 kg/m2 |
| Normal weight | ≥18.5 to 24.9 kg/m2 |
| Overweight | ≥25 to 29.9 kg/m2 |
| Obesity | ≥30 kg/m2 |
| Obesity class 1 | 30 to 34.9 kg/m2 |
| Obesity class 2 | 35 to 39.9 kg/m2 |
| Obesity class 3 | BMI ≥40 kg/m2 |
*Alternate names from different classifications:
| BMI | |
|---|---|
| Severe Obesity | ≥ 35 or 40 kg/m2 |
| Morbid Obesity | ≥ 35 kg/m2 + obesity-related health conditions or ≥ 40 kg/m2 |
| Super Obesity | ≥ 45 or 50 kg/m2 |
Characteristics:
- Changes depend on extent + duration of obesity
- Complex genetic and environmental causes
- Increased caloric intake
- Increased metabolic rate (normal for BSA)
- associated with HTN, HF, IHD, cardiomyopathy, sudden cardiac death, arrhythmias, PVD, DVT, CVD
- Hormonal changes:
- ↑ SNS
- ↑ HR + ↑ SV
- ↑ RAAS → Na+ retention → ↑ blood vol → ↑ MAP (Systemic HTN)
- ↑ MAP → LVH → LV dilation → LV failure
- LV diastolic failure + ↑ PVR → RV hypertrophy
- ↑ Leptin → Cardiac remodelling + LVH
- Plasminogen Activator Inhibitor-1 → ↓ fibrinolysis → predisposes to VTE
- Inflammatory Adipokines → Impairs endothelial function → ↑ SVR
- insulin resistance + hyperlipidaemia → inflammatory mediator upregulation → disrupt endothelial function → IHD + cerebrovascular disease + PVD
- ↑ SNS
- Mechanical Effect: Compression of abdominal + leg vessels
- ↓ VR → supine hypotension + ↑ risk DVTs
Changes in CVS:
- Increased VO2 : Due to increased LBM and fat mass.
- Increased Blood Volume : Due to increased angiotensin II and aldosterone.
- Increased Stroke Volume: Due to:
- Increased preload (major factor)
- Increased contractility (minor factor) due to increased circulating adrenal hormones.
- Increased Cardiac Output: To maintain DO2.
- Initially with preserved ejection fraction
- ↑ Peripheral vascular resistance
- Inflammatory Adipokines → Impairs endothelial function
- ↑ SNS
- Diastolic dysfunction: Due to myocardial fibrosis impairing relaxation.
- direct deposition of fat in myocardium → conduction disease (& predisposition to arrhythmias) + cardiomyopathy
- OSA
- Pulmonary HTN → cor pulmonale
- Polycythaemia → ↑ viscosity
Kerr / JC 2020
Exam appearances
| Exam | Exact wording | Relationship | Success |
|---|---|---|---|
| 2017A Q15 | Outline the cardiovascular changes associated with morbid obesity. | historical_member | — |
| 2025B Q12 | (a) Define morbid obesity (5% of marks). (b) Outline the cardiovascular changes associated with morbid obesity (95% of marks). | safe_repeat | 23.00% |