Week 3 - Ischaemic Heart Disease

Question 1

Define Cardiovascular disease

Answer 1

Any condition that affects the structure and function of the heart and blood vessels

Question 2

What are some examples of cardiovascular disease?

Answer 2

• Coronary Artery Disease (CAD) - Angina, myocardial infarction
  
  • Cerebrovascular disease (CVD)
  • Peripheral vascular disease (PVD)
  • Heart Failure (HF)
  • Hypertension
  • Rheumatic Heart Disease
  • Congenital Heart Disease

Question 3

What is Rheumatic Fever?

Answer 3

• Autoimmune disease that results from a Group A Streptococcus (GAS) infection in the throat
• Is linked to poor housing conditions, overcrowding, socioeconomic deprivation, barriers to primary health care access and a lack of treatment for strep throat
• Is largely unseen in the developed world but NZ has one of the highest rates in the world - mainly in the North Island
• If untreated, it may develop into rheumatic heart disease and go on to damage the heart - valve/s may need to be replaced
• 92% of all cases of rheumatic fever affect Māori and pacific island children and young people (aged 4-19)

Question 4

Define Ischaemic Heart Disease

Answer 4

The term is given to heart problems caused by narrowed heart arteries. When arteries are narrowed, less blood and oxygen reach the heart muscle. Ischemia occurs when there is insufficient blood flow and blood volume to supply the O2 needs of the myocardium

Question 5

What is the underlying pathophysiology of Ischaemic Heart Disease?

Answer 5

Usually atherosclerosis

Question 6

What is Angina?

Answer 6

• Symptom of reversible myocardial ischaemia
• Usually predictable and manageable
• Occurs due to a stable lesion/plaque in the coronary artery
• A type of chest pain caused by reduced blood flow to the heart (often described as squeezing, pressure, heaviness, tightness or pain in the chest)

Question 7

What is the key pathophysiology of IHD?

Answer 7

Ineffective myocardial oxygen perfusion

• Myocardial oxygen demand is greater than oxygen supply
• At risk of heart muscle damage/necrosis
• Damaged muscle behaves ineffectively
• At risk of arrhythmia (damaged muscle does not convey impulses well)
• May lead to cardiac arrest

Question 8

What is a Myocardial Infarction and its characteristics?

Answer 8

• Results from sustained ischaemia or sudden complete blockage of the coronary artery from plaques (atherosclerosis). If the plaques rupture, you can have a heart attack (myocardial infarction)
• Myocardial tissue distal to the obstruction dies
• Can be partial thickness (NSTEMI) or full thickness (transmural) (STEMI)
• Life-threatening
• Complications include:
  
  • Cardiogenic shock, heart failure, ventricular fibrillation (VF) which can lead to death

Question 9

Definition of an MI

Answer 9

• Non-ST-Elevation Myocardial Infarction (NSTEMI) involves partial thickness myocardial wall damage
• ST-Elevation Myocardial Infarction (STEMI) involves full thickness myocardial wall damage (with/without necrosis)

Question 10

Compare STEMI and NSTEMI together

Answer 10

• Stemi:
  
  • Full thickness damage to the myocardium (transmural)
  • Sudden complete blockage of a coronary artery
  • ST segment evaluation on an ECG
  • No need to wait for bloods - ECG finding is definitive
• NSTEMI:
  
  • Partial thickness damage to the myocardium
  • Partial blockage of a coronary artery
  • Not visible on an ECG
  • Need bloods for cardiac biomarkers to diagnose

Question 11

What is Acute Coronary Syndrome (ACS)?

Answer 11

• Group of clinical symptoms that are consistent with acute myocardial ischaemia. Unless interventions are applied promptly ACS can result in myocardial death
• ACS is the term for an imbalance of 02 supply and demand. The underlying pathophysiology is atherosclerosis which can lead to plaque rupture and thrombus formation

Question 12

What conditions fall under Acute Coronary Syndrome?

Answer 12

• Unstable angina (UA),
• Non—ST-segment elevation myocardial infarction (NSTEMI),
• ST-segment elevation myocardial infarction (STEMI)

Question 13

What are some Signs and symptoms of IHD & ACS?

Answer 13

Pale, grey, confused, tachycardic, hypotensive, hypertensive, chest pain, dyspnoea, weak thready pulse, feeling of impending doom, think it’s indigestion, feel like an elephant on their chest, tachypnoeic, fatigue, anxiety, ECG abnormalities, pain radiating across the chest, down the left arm, into the jaw, into the back, palpitations, restlessness, tightness in chest, hypoxaemia, diaphoresis, cyanosis, dizzy, light-headed, nausea

Question 14

How does the body minimise the effects of an MI?

Answer 14

• In absence of O2, cell function will deteriorate:
  
  • Ischaemia: Lack of O2
  • Injury: Potentially reversible damage
  • Infarction: Necrosis - permanent damage

Question 15

How is ACS/MI diagnosed?

Answer 15

• History (chest pain and related symptoms)
• 12 Lead ECG (ST elevation height and area of the heart)
• Blood tests

Other Diagnostic Investigations that may be Untaken Include::

• Coronary angiogram +/- Angioplasty
• Echocardiography (ECHO)
• Transoesophageal Echocardiography
• Exercise tolerance test (ETT)
• Electrophysiological studies (EPS)
• Chest X-Ray

Question 16

What are some blood tests that might be used for the diagnosis of ACS?MI?

Answer 16

• Troponin T and I - Cardiac specific enzymes
  • Cardiac enzymes: Creatinine kinase (CK-MB) - mainly in cardiac muscle, myoglobin -
    cardiac and skeletal muscle
  • Electrolytes - K+, NA+, important for electrical conduction and kidney function
  • Complete blood count (CBC)
  • Lipid Profile - fasting
  • Brain Naturide Peptide (BNP)

Question 17

What is the underlying Pathophysiology for ACS?

Answer 17

• Atherosclerosis which can lead to plaque rupture and thrombus formation
• Thrombus formation may occlude the coronary artery leading to aerobic metabolism and potential cell death
• Pain may be different to the usual angina
• ACS can occur without precipitants
• Unrelieved by the individual’s usual methods of symptom relief
• Lasts longer than 20 minutes

Question 18

What are some Precipitants of Angina/ACS?

Answer 18

• Exercise/Exertion:
  
  • Increase HR, CO and Myocardial O2 demand
• Extremes of Temperature:
  
  • Vasoconstriction increases resistance
  • Vasodilation decreases venous return
• Eating a heavy meal:
  
  • Increased parasympathetic stimulation - blood diverted to the GI system
• Emotions/stress:
  
  • Increase HR, CO and Myocardial O2 demand
• Effects of drugs:
  
  • Can Increase or decrease HR and BP

Question 19

What are some Priority goals of management for ACS?

Answer 19

Open the artery and keep it open:

• Increase oxygen supply to the myocardium - give nitrates and consider O2 is SaO2 < 93%
• Relieve pain, reduce O2 demand and signs of ischaemia
• Preserve viable myocytes
• Receive Obstruction:
  
  • Manage thrombus to re-perfuse the artery and minimise permanent damage

Question 20

What are some interventions for ACS?

Answer 20

• Follow the Heart Foundation Angina Action Plan
• Percutaneous Coronary Intervention (PCI)
• Thrombolysis - Fibrinolytic therapy (dissolve clots)
  
  • Alteplase/Metalyse
  • Streptokinase
  • Tissue plasminogen activator (TPA)

Question 21

What is the difference between a HEART ATTACK and CARDIAC ARREST?

Answer 21

• Heart attack is a MI
  
  • Results from a blocked coronary artery
  • This prevents oxygen-rich blood from reaching the myocardium
  • Without oxygen, the myocardial cells begin to die
    
    • = Circulation problem
• Cardiac arrest is a sudden cessation of the heart’s functioning
  
  • Triggered by an electrical malfunction in the heart that causes an arrhythmia (Irregular
    heart beat)
  • Disrupts the pumping action
    
    • = Electrical problem