Notes on Cardiac Physiology and Ageing Heart Health

Cardiac Physiology: Protecting the Heart During Ageing

Overview of Ageing and Heart Health

• Increased Life Expectancy: Public health advancements have significantly raised life expectancy, with projections indicating that by 2030, individuals over 65 will make up nearly 20% of the population.

• Demographic Trends: The oldest age groups (≥85 years) represent the fastest-growing cohort, expected to increase by over 230% by 2050.

Physiological Changes in the Ageing Heart

• Heart Structure and Function Changes:

  • Decreased Heart Rate: Significant changes in the sinoatrial node lead to a reduced heart rate.

  • Increased Arrhythmias: With age, there's a rise in arrhythmic events, influenced by factors such as AMPK activation and KlubR1 pathways.

  • Cellular Changes:

  • Accumulation of senescent progenitor cells and myocytes, which impact the heart's function and structure (related to genes like SIRT1, p66).

  • Increased apoptotic and necrotic cells affecting myocardial tissue.

  • Fibrosis and Hypertrophy: Associated with pathways involving SIRT1 and IGF-1.

• Tissue and Vascular Changes:

  • Arterial Stiffness: Ageing leads to arterial thickening and decreased elasticity (linked to BubR1).

  • Functional Declines: Reduced heart volume, poor capillary-to-fibre ratio, and compromised blood vessel elasticity contribute to various cardiovascular challenges.

Consequences of Ageing Affecting Heart Health

• Cardiovascular Disease (CVD):

  • CVD is the leading cause of death in older adults, accounting for approximately 40% of all deaths.

  • Heart failure (HF) is notably higher in those aged 65 and above, with approximately 88% of HF deaths occurring within this group.

Intrinsic and Extrinsic Factors Leading to Heart Issues

• Life Long Impact of Insults: Cumulative effects from conditions like myocardial infarctions and hypertension lead to maladaptive myocardial remodelling and HF.

• Research Insights: Studies using animal models have identified transcriptional changes linked with cardiac aging, which mirror conditions in HF:

  • Altered stress response pathways, mitochondrial function, fatty acid metabolism, and inflammation are key factors.

Behavioral and Environmental Risks for Coronary Heart Disease (CHD)

• Primary Risk Factors:

  • Behavioral: Alcohol and drug use, poor diet, tobacco smoke, and low physical activity.

  • Metabolic: High body mass index (BMI), high blood pressure, high cholesterol, and high fasting glucose.

  • Environmental: Pollution and occupational hazards.

Exercise and the Ageing Heart

• Performance Declines: Older adults (aged 60-80) show diminished heart performance during peak exercise compared to younger individuals (aged 20-30).

• Autonomic Nervous System (ANS) Response:

  • Heart's reaction to exercise is regulated through a shift in ANS, where acute exercise increases sympathetic tone and decreases parasympathetic tone, resulting in increased heart rate (HR) and contractility.

  • Ageing diminishes this responsiveness, leading to sympathetic dysregulation and reduced catecholamine effectiveness (increased noradrenaline levels).

• Reversibility Through Exercise:

  • Evidence indicates that regular aerobic exercise can improve heart responsiveness to adrenergic stimuli in older adults, enhancing exercise capacity by up to 28% and improving heart contractility.

  • Effects can be negated with β1-receptor antagonism, highlighting the role of exercise in cardiac health.

Stress Cardiomyopathy (Takotsubo Cardiomyopathy)

• Emotional Impact on the Heart:

  • Extreme stress can induce symptoms resembling heart attacks, such as chest pain and dyspnea.

  • A significant sympathetic response can lead to transient left ventricular apical ballooning and arrhythmias.

  • Demographics at Risk: Predominantly affects females, especially those over 50 or with a history of psychiatric or neurological issues.

• Mortality Risk: While stress-induced heart conditions can be severe, overall mortality rates are low and reoccurrence is infrequent.

Contents

1. Overview of Ageing and Heart Health

2. Physiological Changes in the Ageing Heart
   2.1 Heart Structure and Function Changes
   2.2 Tissue and Vascular Changes

3. Consequences of Ageing Affecting Heart Health

4. Intrinsic and Extrinsic Factors Leading to Heart Issues

5. Behavioral and Environmental Risks for Coronary Heart Disease (CHD)

6. Exercise and the Ageing Heart

7. Stress Cardiomyopathy (Takotsubo Cardiomyopathy)