MS1 Chapter 21

• The heart is located in the mediastinum, within the thoracic cavity
• The heart is enclosed by 3 membranes:

  • Fibrous pericardium
  • Parietal pericardium
  • Visceral pericardium (epicardium)
• Layers of the pericardial sac:

  • Fibrous pericardium: outermost; forms a loose-fitting pericardial sac around the heart
  • Parietal pericardium: second, middle layer; serous membrane that lines the fibrous layer
  • Visceral pericardium (epicardium): third, innermost layer; serous membrane on the surface of the heart muscle
  • Between the parietal and visceral layers is serous fluid, which prevents friction as the heart beats
• Cardiac Structure and Vessels:

  • Four chambers: right/left atrium, right/left ventricle
  • Cardiac layers: Epicardium, myocardium, endocardium
  • Coronary arteries
  • Valves: Tricuspid, pulmonary, mitral, aortic
• Cardiac Chambers:

  • Four chambers: Right atrium, Left atrium, Right ventricle, Left ventricle
  • Although each ventricle pumps the same amount of blood, the left ventricle pumps with approximately five times the force of the right ventricle
• Coronary Arteries:

  • The two main coronary arteries are the right coronary artery & left coronary artery
  • A "widowmaker" heart attack is caused by blockage of the LAD
• Cardiac Valves:

  • Tricuspid Valve: Located between the right atrium & right ventricle, has 3 cusps
  • Mitral Valve: Located between the left atrium & left ventricle, has 2 cusps
  • Pulmonary Valve: Located between the right ventricle & the pulmonary artery
  • Aortic Valve: Located between the left ventricle & the aorta
• Blood Vessels:

  • Arteries carry blood from the heart to capillaries, carrying oxygen-rich blood
  • Veins carry blood from capillaries to the heart, carrying deoxygenated blood
  • Capillaries form extensive networks in most tissues
• Blood Flow Through the Heart:

  • Pulmonary Circulation: Begins at right ventricle, pumps deoxygenated blood towards lungs for gas exchange. Oxygenated blood returns to the left atrium
  • Systemic Circulation: Begins at left ventricle, pumps oxygenated blood towards the body tissues. Deoxygenated blood returns to the right atrium
• Cardiac Conduction:

  • Sinoatrial (SA) node initiates each heartbeat
  • Atrioventricular (AV) node can initiate each heartbeat if the SA node is nonfunctional
  • Bundle of His can generate the beat of the ventricles
• Renin-Angiotensin-Aldosterone Mechanism:

  • Kidneys play a role in the regulation of blood pressure
  • Decreased blood pressure stimulates the kidneys to secrete renin, raising blood pressure
• Stroke Volume:

  • Amount of blood ejected by a ventricle in 1 contraction, averages 60 to 80 mL/beat
• Cardiovascular Disease:

  • Number 1 cause of death
  • Healthy lifestyle includes smoking cessation, exercise, dietary fat reduction, normal BP, glucose, cholesterol levels, normal weight
• Cardiovascular Assessment:

  • Includes health history, physical assessment, and diagnostic studies
• Cardiac Output (CO):

  • Stroke volume multiplied by heart rate = cardiac output
  • With an average resting heart rate of 75 beats per minute, average resting cardiac output is 5-6 L
• Ejection Fraction (EF):

  • Measure of ventricular efficiency
  • Normally 55% to 70%(🩸 ejected from the Left Ventricle per 💗)
  • Decreased EF leads to heart failure
• System Regulation of the Heart:

  • The heart generates its own electrical impulse, which begins at the SA node
  • The nervous system can change the heart rate in response to environmental circumstances
• Physical Examination:

  • Includes general appearance, vital signs, orthostatic BP, height, weight
• Blood Pressure:

  • Systolic "top number"
  • Diastolic "bottom number"
  • Normal is 120/80 mmHg
• Hormones and the Heart:

  • Epinephrine increases heart rate, force of contraction, cardiac output, and systolic blood pressure
  • Aldosterone regulates sodium/potassium levels
• Aging and the Cardiovascular System:

  • Atherosclerosis leads to buildup of lipids on walls of arteries
  • Resting BP increases
  • Vein valves become more incompetent
  • Heart muscle becomes less efficient
  • Arrhythmias become more common
• Health History:

  • Includes symptoms, allergies, medications, past medical and surgical history, family history, functional limitations
• Physical Examination Continued:

  • Orthostatic BP is taken lying, sitting, and standing to detect abnormal variations with postural changes
• Orthostatic BP:

  • BP and pulse are taken lying, sitting, and standing to detect abnormal variations with postural changes
  • Positive findings indicate "orthostatic hypotension"
  • Criteria for orthostatic hypotension:
  • Drop in SBP > 15 mmHg
  • Drop or increase in DBP > 10 mmHg
  • Increase in heart rate > 20 BPM
  • Use caution when taking orthostatic vital signs as patients often report dizziness, light-headedness, or syncope
  • Factors that may cause orthostatic hypotension: deficient fluid volume, diuretics, analgesics, pain
• Respirations:

  • Assess rate and ease of respirations
  • Evaluate breath sounds, sputum characteristics, and cough
• Inspection:

  • Oxygenation status is noted through skin, mucous membrane, lip, and nailbed color
  • Different skin colors indicate oxygen deficiency:
  • Dark skin: whitish or gray color around the mouth and blue or gray conjunctiva
  • Yellowish skin: grayish-greenish color
  • Light skin: dark blue skin and mucous membranes
• Extremities:

  • Assess hair distribution, skin, nails, edema, and color
  • Check for jugular vein distention (JVD) in a 45- to 90-degree upright position
  • Distention of jugular veins indicates an increase in venous volume, often caused by right-sided heart failure
• Pulse:

  • Apical pulse is measured for 1 minute
  • Normal heart rate is 60-100 BPM
  • Athletic individuals may have a slower resting heart rate due to a well-conditioned heart
  • Compare apical rate with radial rate for equality
  • Pulse deficit: when there are fewer radial beats than apical beats, report to healthcare provider
• Capillary refill:

  • Assess capillary refill time by briefly squeezing the nailbed and observing the time for color to return
  • Normal capillary refill time is 3 seconds or less, indicating arterial blood flow to the extremities
  • Longer times suggest anemia or decreased blood flow
• Blood Studies:

  • Cardiac biomarkers include Troponin (specific to heart muscle), Creatine kinase/CK-MB (heart, brain, & skeletal muscles), and Myoglobin (cardiac & skeletal muscles)
  • Elevated levels of these biomarkers may indicate recent myocardial infarction
• Clubbing:

  • Occurs from oxygen deficiency over time
  • Early signs include a loss of the normal 160-degree angle at the nail base, causing a flat nail
  • Later signs include an elevated nail base with an angle exceeding 180 degrees, and the nail feels spongy when squeezed
  • To assess clubbing, put index fingers at the nailbeds/first joint together; a diamond shape in the space is normal
• Palpation:

  • Check the temperature of extremities for bilateral equality
  • Assess for edema by applying pressure over bony areas; pitting edema is indicated if indentation remains
• Auscultation:

  • Listen to heart sounds (S1, S2, S3, S4)
  • Murmurs are caused by narrowed valve openings or valves that do not close tightly
  • Pericardial friction rub is caused by inflammation of the pericardium, producing a grating sound like sandpaper being rubbed together
• Troponin:

  • Elevates 2-6 hours after cardiac damage
  • Peaks 15-20 hours after cardiac damage
  • May remain elevated for 5-7 days after cardiac damage
• Reactive protein:

  • Increases with inflammation and can predict the risk for myocardial infarction
  • Homocysteine elevation may damage the lining of arteries, increasing cardiovascular disease risk
  • Elevated lipids (triglycerides, cholesterol, phospholipids) also increase cardiovascular disease risk
• Diagnostic Tests (Noninvasive):

  • Chest radiograph (x-ray) evaluates heart enlargement, calcifications, fluid around the heart, and more
  • Cardiac Computed Tomography (CT) scan and angiography evaluate heart structures
  • Coronary Magnetic Resonance Imaging (MRI) assesses ischemia and heart damage (patient must show card if a pacemaker is present)
  • Electrocardiogram (ECG or EKG) records cardiac electrical activity and is a diagnostic test for heart attacks
• Diagnostic Tests (Invasive):

  • Angiography involves injecting dye to visualize vessels
  • Cardiac catheterization evaluates heart vessels and chambers
  • Hemodynamic monitoring includes arterial line placement for continuous blood pressure measurement
  • Electrophysiology study assesses the heart's electrical system
• Therapeutic Interventions:

  • Lifestyle and cardiac care focus on risk factor prevention through diet, exercise, weight loss, and smoking cessation
  • Antiembolism devices like compression stockings and intermittent pneumatic compression devices increase circulation in the legs
  • Oxygen may be given for chest pain to ensure the heart receives sufficient oxygen
• Cardiac Surgery:

  • Preparation includes holding certain medications, educating the patient on coughing & deep breathing, and pain management
  • Cardiopulmonary bypass involves diverting blood away from the heart and lungs for surgical procedures
• Review Questions:

  1. Epinephrine effects on the heart include increasing heart rate, strengthening force of contraction, increasing cardiac output, and increasing systolic blood pressure

  2. Effects of aging on the cardiovascular system include arteriosclerosis, decreased blood pressure, less efficient heart muscle, and common arrhythmias

  3. During data collection of the cardiovascular system, the nurse should inspect capillary refill, clubbing of nailbeds, nailbed color, jugular veins, and pupil size