22B12: Exam Report

Describe the effects of ageing on the cardiovascular system

46% of candidates passed this question.

The physiological changes associated with ageing are well described in the major texts although candidates do need to assimilate this information from a number of sources.

Core components of the answer templates that were frequently missed included those of; concentric hypertrophy and its effects on afterload, as well as the difference between compliance, elastance, elasticity, elastin and collagen and how ageing affects these elements.

A template using broad headings such as the effects on the heart/myocardium, the vasculature, the autonomic nervous system, the conduction system and perhaps epithelial function would be a good starting point when constructing an answer to this question.

The examiners noted that several candidates wrote at length about various pathologies that increase in incidence with ageing which does not adequately address the core of the question.

G6i / 22B12: Describe the effects of ageing on the cardiovascular system

Ageing

Ageing = the normal physiological process of progressive degeneration beginning at 30 yrs and progressing at a variable rate.  It is associated with an increased vulnerability to stress with a diminished ability to maintain normal body homeostasis.

1. Effects on the conduction system

  • No change to resting HR
  • Max HR decreases from 200 to 160 (due to decreased B adrenergic responsiveness)
  • Fibrous infiltration of SA node → susceptible to supraventricular arrhythmia and ectopics
  • AVN and bundle of His unchanged

2. Effects on Heart/myocardium/Valves:

  • Collagen replaces elastin → increased connective tissue in the heart
  • Amyloid and Lipofuscin deposits within myocytes → increase in total myocardial wall thickness in response to increase in left ventricular outflow impedance → reduced Ejection Fraction
  • Increased endocardial fibrosis → decreased compliance of the heart, impaired conduction
  • Valvular calcifications → valvular incompetence → increased resistance
  • Max SV reduced
  • Reliance on atrial kick
  • Total CO decreases by 1%/1 yr after age 30
  • Reduced CO → increases circulation time

*CO decline is thought to be due to sedentary lifestyle and age-related diseases

3. Effects on the vasculature

  • Decreased large arteries elasticity → increase SBP and MAP
  • Increased peripheral resistance → increase DBP (although recent studies suggest a decrease due to rapid run-off of blood in the stiff large arteries)
  • Decreased Windkessel effect due to decreased elasticity of large arteries
  • PASP and PADP increase, PVR increase as well

4. Effects on the ANS

  • Impaired baroreceptor reflex → postural hypotension, also implications in response to sepsis and hemorrhage
  • Hyperactivity of carotid sinus → physiologic vagotonia & bradycardia
  • Reduced sympathetic neurons and autonomic responsiveness to stress
  • Reduced responsiveness of cardiac B receptors (due to reduced receptor number +/- affinity +/- decreased cAMP after receptor activation)
  • Increased circulating catecholamines due to above

5. Effects on endothelial function

  • Decreased NO-mediated vasodilation
  • Decreased ANP
  • Overall increased SVR

Author: Mema Idrees