Cardiac Anatomy and Coronary Artery Disease

• Coronary artery disease (CAD) is the primary cause of most cardiac-related issues

Cardiac Anatomy

• The heart is a four-chambered muscular organ responsible for pumping blood throughout the body
• The heart consists of two atria (right and left) and two ventricles (right and left)
• The atria receive blood, while the ventricles pump blood out of the heart
• The right atrium receives deoxygenated blood from the body via the superior and inferior vena cavae
• The right ventricle pumps deoxygenated blood to the lungs via the pulmonary artery
• The left atrium receives oxygenated blood from the lungs via the pulmonary veins
• The left ventricle pumps oxygenated blood to the body via the aorta
• Valves ensure unidirectional blood flow through the heart:
  • Tricuspid valve: between the right atrium and right ventricle
  • Pulmonic valve: between the right ventricle and pulmonary artery
  • Mitral (bicuspid) valve: between the left atrium and left ventricle
  • Aortic valve: between the left ventricle and aorta
• The coronary arteries supply the heart muscle with oxygenated blood
  • The main coronary arteries are the left main, left anterior descending (LAD), circumflex, and right coronary artery (RCA)
• The heart's electrical conduction system controls heart rate and rhythm
  • Sinoatrial (SA) node: the heart's primary pacemaker, located in the right atrium
  • Atrioventricular (AV) node: delays the electrical impulse, allowing the atria to contract before the ventricles
  • Bundle of His: conducts the impulse from the AV node to the ventricles
  • Left and right bundle branches: conduct the impulse through the ventricles
  • Purkinje fibers: distribute the impulse throughout the ventricular myocardium, causing contraction

Cardiac Pathophysiology

• Atherosclerosis: plaque buildup inside the arteries, leading to narrowing and reduced blood flow
  • Can lead to angina (chest pain) or myocardial infarction (heart attack) if a coronary artery is affected
• Ischemia: insufficient blood supply to the heart muscle, often due to CAD
  • Prolonged ischemia can lead to tissue damage or death (infarction)
• Myocardial Infarction (MI): occurs when blood flow to a part of the heart is completely blocked, causing tissue damage
  • Commonly caused by a thrombus (blood clot) forming on a ruptured atherosclerotic plaque
  • Diagnosed by ECG changes and elevated cardiac biomarkers (e.g., troponin) in the blood
• Angina Pectoris: chest pain caused by temporary myocardial ischemia
  • Stable angina: predictable and relieved by rest or nitroglycerin
  • Unstable angina: unpredictable and may occur at rest; a sign of worsening CAD
• Heart Failure: the heart's inability to pump enough blood to meet the body's needs
  • Can result from various conditions, including MI, hypertension, and valve disorders
  • Leads to fluid retention, shortness of breath, and fatigue
• Arrhythmias: abnormal heart rhythms caused by disturbances in the heart's electrical conduction system
  • Tachycardia: heart rate too fast (usually >100 bpm)
  • Bradycardia: heart rate too slow (usually <60 bpm)
  • Atrial fibrillation: rapid, irregular atrial contractions
  • Ventricular tachycardia: rapid, life-threatening ventricular contractions
  • Ventricular fibrillation: disorganized, ineffective ventricular contractions; leads to cardiac arrest
• Cardiomyopathy: disease of the heart muscle, making it harder for the heart to pump blood
  • Dilated cardiomyopathy: enlarged heart with weakened pumping ability
  • Hypertrophic cardiomyopathy: thickened heart muscle, which can obstruct blood flow
  • Restrictive cardiomyopathy: stiff heart muscle, limiting its ability to fill with blood
• Valvular Heart Disease: conditions affecting the heart valves, disrupting blood flow
  • Stenosis: narrowing of a valve, restricting blood flow
  • Regurgitation (insufficiency): leakage of blood backward through a valve
• Hypertensive Heart Disease: heart problems caused by long-term high blood pressure
  • Can lead to left ventricular hypertrophy, heart failure, and increased risk of arrhythmias
• Congenital Heart Defects: structural abnormalities of the heart present at birth
  • Examples include ventricular septal defect (VSD), atrial septal defect (ASD), and tetralogy of Fallot
• Cardiac Tamponade: compression of the heart caused by fluid accumulation in the pericardial sac
  • Restricts the heart's ability to fill with blood, leading to decreased cardiac output
  • Beck's triad (hypotension, muffled heart sounds, and jugular venous distension) is a classic sign
• Pericarditis: inflammation of the pericardium (the sac surrounding the heart)
  • Causes chest pain that may worsen with breathing or lying down

Patient Assessment

• Gather a thorough history, including:
  • Chief complaint
  • History of present illness (HPI)
  • Past medical history (PMH)
  • Medications
  • Allergies
  • Social history (smoking, alcohol, drug use)
  • Family history (cardiac disease, hypertension, diabetes)
• Key questions to ask:
  • "Can you describe your chest pain?" (location, intensity, duration, quality, radiation)
  • "What makes the pain better or worse?"
  • "Do you have any other symptoms, such as shortness of breath, nausea, vomiting, sweating, or dizziness?"
  • "Do you have a history of heart problems?"
• Vital Signs:
  • Heart rate (HR)
  • Blood pressure (BP)
  • Respiratory rate (RR)
  • Oxygen saturation (SpO2)
  • Temperature
• Assess level of consciousness (LOC) and mental status
• Cardiac-Specific Assessment:
  • Auscultate heart sounds (normal S1 and S2, extra sounds like S3 or S4, murmurs)
  • Auscultate lung sounds (clear, wheezes, crackles)
  • Palpate pulses (rate, rhythm, strength)
  • Observe for signs of fluid retention (edema in extremities, jugular venous distension)
  • Examine skin color and temperature (pale, cool, diaphoretic)
• 12-Lead ECG:
  • Essential for identifying cardiac arrhythmias, ischemia, and infarction
  • Placement of electrodes:
    • V1: 4th intercostal space, right sternal border
    • V2: 4th intercostal space, left sternal border
    • V4: 5th intercostal space, midclavicular line
    • V3: Midway between V2 and V4
    • V5: 5th intercostal space, anterior axillary line
    • V6: 5th intercostal space, mid-axillary line
    • Limb leads: RA, LA, RL, LL (placed on the limbs)
  • Analyze the ECG for:
    • Heart rate and rhythm
    • P waves (atrial depolarization)
    • QRS complexes (ventricular depolarization)
    • T waves (ventricular repolarization)
    • ST segment (elevation or depression indicates ischemia/infarction)
    • PR interval (time from atrial to ventricular depolarization)
    • QT interval (total time for ventricular depolarization and repolarization)
• Blood Glucose:
  • Check blood glucose level, especially in patients with altered mental status or suspected diabetes
• Capnography (ETCO2):
  • Can provide information about ventilation and perfusion
• Continuous Monitoring:
  • Continuously monitor ECG, vital signs, and SpO2
• SAMPLE History:
  • Signs and Symptoms
  • Allergies
  • Medications
  • Pertinent Past History
  • Last Oral Intake
  • Events Leading to the Incident
• OPQRST for Pain Assessment:
  • Onset
  • Provocation/Palliation
  • Quality
  • Region/Radiation
  • Severity
  • Timing
• Physical Exam Techniques:
  • Inspection: Look for visible signs of distress, such as cyanosis, diaphoresis, or difficulty breathing.
  • Palpation: Check for pulses, edema, and tenderness.
  • Auscultation: Listen to heart and lung sounds for abnormalities.