Cardiac Physiology: Stress, the Heart, and CVD Notes

Coronary Heart Disease (CHD)

• Definition: CHD refers to the heart's inability to perfuse adequately due to blockages in the coronary arteries.

• Statistics: In the UK,

  • 1 in 7 men and 1 in 11 women die from CHD.

  • Responsible for nearly 70,000 deaths annually in the UK, translating to approximately 190 deaths daily (one every eight minutes).

Deaths from Cardiovascular Disease (CVD)

• England (2015): 129,147 deaths from CVD under 75.

• Scotland (2016): 15,131 deaths.

• Wales (2015): 9,027 deaths.

• Northern Ireland (2015): 3,773 deaths.

• Total UK (2015): 158,155 deaths from CVD, with approximately 670,000 people living with the condition.

Diagnosis of CHD

• Methods:

  • ECG (Electrocardiogram)

  • Stress testing

  • Nuclear scanning

  • Coronary angiography (detects blockages, often using contrast agents)

• Common ECG findings:

  • ST elevation / flattening or inversion of T waves / presence of Q waves.

Risk Factors for CHD

• Incontrollable factors:

  • Gender

  • Age

  • Heredity

  • Ethnicity

• Controllable factors:

  • Smoking

  • Obesity

  • Sedentary lifestyle

  • Diabetes

  • High blood pressure (hypertension)

  • High blood cholesterol

  • Stress.

Understanding Stress

• Types of Stress:

  • Eustress: Positive, motivating stress that can improve performance.

  • Distress: Negative stress that impairs focus and efficiency.

• Physiological Response:

  • Activation of sympathetic nervous system leads to the release of adrenaline, increasing heart rate and blood pressure.

• Stress Response:

  1. Sympathetic Adrenomedullary Axis (SAM): Rapid response to acute stress, enhancing survival.

  2. Hypothalamic–Pituitary–Adrenal (HPA) Axis: Slower response involving cortisol release, regulating longer-term stress responses.

Acute vs. Chronic Stress Effects

• Acute Stress:

  • Fight or flight response.

  • Symptoms: Increased heart rate, higher blood pressure, spikes in catecholamines, risk of ventricular arrhythmias.

• Chronic Stress:

  • Long-term effects lead to mental strain, coping issues, and potential adaptations that may negatively impact cardiovascular health.

Myocardial Infarction (MI) vs. Cardiac Arrest

• Myocardial Infarction (MI):

  • Caused by complete obstruction of blood flow in a coronary artery, leading to tissue death due to lack of blood supply.

• Cardiac Arrest:

  • Cessation of effective heartbeat, can precede or result from an MI.

Physiological Mechanisms in Cardiac Events

• Dysfunctional ion channels enhance the risk of arrhythmias. Key ionic channels affected include:

  1. Sodium Channels (e.g., Nav1.5) for depolarization.

  2. Potassium Channels (e.g., KCNQ1, hERG/Kv11.1) for repolarization.

  3. Calcium Channels (e.g., L-type) for excitation-contraction coupling.

• Triggers include ischemia, acidosis, and electrolyte imbalances leading to cardiac arrhythmias or arrest.

Impact of Stress on Cardiac Health

• Strong correlation between chronic stress and various cardiovascular outcomes, including hypertension and myocardial events.

• Behavioral pathways related to stress contribute to poor adherence to medication and lifestyle choices detrimental to heart health.

Learning Outcomes

• Understand definitions and risk factors related to CHD.

• Comprehend how acute and chronic stress affects cardiac health.

• Recognize the physiological processes involved in myocardial infarction and cardiac arrest in the context of stress.

This integrated understanding of stress and its relation to cardiac health is vital for treatment and prevention strategies in cardiovascular disease.

Contents

1. Definition

2. Statistics

3. Deaths from Cardiovascular Disease (CVD)

4. Diagnosis of CHD

5. Risk Factors for CHD

6. Understanding Stress

   • 6.1. Types of Stress

   • 6.2. Physiological Response

   • 6.3. Stress Response

7. Acute vs. Chronic Stress Effects

   • 7.1. Acute Stress

   • 7.2. Chronic Stress

8. Myocardial Infarction (MI) vs. Cardiac Arrest

   • 8.1. Myocardial Infarction (MI)

   • 8.2. Cardiac Arrest

9. Physiological Mechanisms in Cardiac Events

10. Impact of Stress on Cardiac Health

11. Learning Outcomes