Coronary Heart Disease pt.1

Session Overview

Rob Widdop introduces the session focusing on coronary heart disease (CHD), building on prior discussions related to atherosclerosis. The importance of acknowledging copyright regulations and land rights is also mentioned.

Lecture Objectives

  • Acute and Chronic Forms of CHD: Discuss examples of acute and chronic coronary heart disease.

  • Acute Coronary Syndrome (ACS): Explain acute coronary syndrome and acute myocardial infarction (AMI) alongside their diagnoses.

  • Biomarkers: Understand the use of biomarkers such as creatine kinase (CK) and troponin for diagnostic purposes in cardiovascular conditions.

  • ECG Measurements: Discuss how ECG can be utilized for prediction in coronary conditions.

  • Cardiac Remodeling: Review how cardiac remodeling post-infarction can lead to heart failure (HF).

  • Treatment Overview: Conclude with examples of medications used to treat various aspects of coronary heart disease, particularly focusing on stable angina and heart failure treatments, including nitric oxide and angiotensin-related compounds.

Importance of Cardiovascular Disease

  • Cardiovascular disease is a significant health issue, accounting for 1 in 4 deaths.

  • Local statistics indicate that the primary causes of cardiovascular-related deaths include coronary heart disease, stroke, and heart failure.

  • Often hypertension is not reported, even though it can be a contributing factor to these deaths.

Case Study

  • A 50-year-old male presents with substernal pain, a history of high lipids, poor dietary habits, and family history of heart disease (father survived heart attack, uncle deceased).

  • He exhibits elevated blood pressure and some left ventricular thickening, leading to a diagnosis of stable effort angina.

Definition of Coronary Heart Disease

  • CHD, also referred to as ischaemic heart disease or coronary artery disease, encompasses a spectrum of conditions rather than a singular diagnosis.

  • Disease Continuum: Patients may present acutely in emergency settings or exhibit chronic stable forms of the disease. Acute manifestations can include:

    • Acute coronary syndrome (ACS)

    • Angina presenting with radiating chest pain

    • Suspected heart attack (acute myocardial infarction)

Acute Coronary Syndrome (ACS)

  • Defined as the reduction in blood flow to the heart, resulting in chest pain or potential cardiac arrest.

  • Diagnosis:

    • Patient must present with chest pain.

    • An ECG is conducted immediately.

    • **Categories of Presentation: **

      • ST-Elevation Myocardial Infarction (STEMI): Persistent elevation in ST segment noted on the ECG; these patients require immediate treatment including reperfusion.

      • Non-ST-Elevation Myocardial Infarction (NSTEMI) or Unstable Angina: Chest pain without evident ST elevation, which can involve varied ECG changes.

ECG and Myocardial Infarction Diagnosis

  • The ECG displays characteristic patterns; it consists of:

    • Atrial signal followed by QRS complex (ventricular contraction).

    • Elevation in the ST segment implies potential STEMI requiring prompt care.

  • Pathology of Infarction:

    • Vessel occlusion due to atherosclerosis can lead to increased risk of thrombus formation and subsequent myocardial infarction (MI).

    • MIs are characterized by tissue death and necrosis.

    • Diagnosis involves measuring cardiac biomarkers and assessing imaging results.

Cardiac Biomarkers for Myocardial Infarction

  • Importance of Biomarkers:

    • Released when cardiac muscle is damaged during an infarction.

    • Creatine Kinase (CK): Historically used but not specific to cardiac tissue (also found in skeletal muscles).

    • Cardiac Troponin: Currently regarded as the gold standard for diagnosing myocardial infarction.

    • Detection Window: Troponin levels can be measured within 4 to 10 hours post-MI, with peak levels occurring later.

  • Diagnostic Requirements for AMI:

    • Significant elevation in cardiac troponin combined with one or more criteria including:

    • Ischaemic symptoms

    • Abnormal ECG findings

    • Imaging showing heart function issues

    • Autopsy results indicating thrombus.

Acute Myocardial Infarction Insights

  • Size and location of the infarct matter significantly as they determine the extent of cell death and inflammation, impacting long-term cardiac function due to low regenerative capacity of cardiomyocytes.

  • Most dead tissue is replaced by fibrotic tissue rather than functional muscle, complicating recovery and leading to potential complications such as heart rupture.

  • Risk factors that lead to acute MIs include existing coronary artery disease, electrical failures, valve issues, and drugs like cocaine or amphetamines causing vasoconstriction.

Chronic Forms of Coronary Heart Disease

  • Following acute events, patients might enter a chronic phase, such as experiencing:

    • Angina Pectoris: Characterized by severe chest pain, often radiating to the arms and accompanied by shortness of breath. Symptoms may include nausea and vomiting, especially in females.

    • Types of Angina:

    • Stable Angina: Pain triggered by exertion or stress.

    • Unstable Angina: Unpredictable pain due to plaque instability or thrombus formation.

    • Variant Angina: Occurs without significant coronary artery disease and is related to coronary vessel spasms.

Treatment Options for Angina

  • Initial Management: Modifying risk factors is essential. Surgical procedures may be necessary to clear obstructed vessels.

  • Chronic Treatment Regimen:

    • Nitro Vasodilators: Used both acutely for immediate relief and chronically for ongoing management of symptoms. An example is glyceryl trinitrate (GTN).

  • Mechanism of Action of Nitro Vasodilators:

    • They release nitric oxide (NO) into the bloodstream, activating guanylate cyclase, which increases cyclic GMP, leading to relaxation of vascular smooth muscle. This reduces both preload and afterload on the heart, lowering oxygen demand and facilitating increased coronary perfusion.

  • Administration and Limitations:

    • Nitrovasodilators may be administered sublingually due to significant first-pass metabolism, or through a transdermal patch.

    • Side effects include hypotension, headache, and potential tachycardia; the combination with phosphodiesterase type 5 inhibitors (like Viagra) is contraindicated due to risk of severe hypotension and cardiovascular collapse.

Conclusion

  • In this first session, Widdop covered medications such as nitroglycerin for angina, emphasizing how crucial it is to address risk factors actively along with drug therapy.

  • Future sessions will elaborate on additional pharmaceuticals and strategies to manage coronary heart disease effectively, including examining underlying lipid profiles and their implications for treatment.