Patient Assessment and Cardiac Function Quiz

Cardiac Anatomy and Physiology

• The presentation covers cardiac anatomy and physiology, objectives, a case study, and details on heart function.
• Objectives include accurately identifying anatomy involved in circulation (mediastinum, heart, blood vessels), describing blood flow, identifying blood supply to the heart, and explaining the cardiovascular, electrical, and mechanical systems.
• The objectives also include identifying inherent heart rates, nerve supply, describing the cardiac cycle, and the processes occurring at each phase.
• A case study presents a patient (Mrs. W) with a recent left lung resection, ovarian cancer history, smoking history, and osteoarthritis. Initial vitals are provided (HR 140 bpm irregular, BP 128/70, RR 12, O2Sat 97% with room air).
• The case prompts a course of action ("To treat or Not To Treat").
• Other cases/patients are presented that detail cardiac conditions, with a focus on abnormal nuclear stress tests, breast cancer, mastectomy, CAD, CHF, diabetes, exposure to secondhand smoke, hypertension, ischemic cardiomyopathy, positive tuberculosis skin tests, psoriasis, etc.
• The presentation highlights structural elements involved in circulation, primarily the heart, central components located within the mediastinum, great vessels for central pulmonary and systemic circulation, and the components of systemic circulation (arteries, arterioles, capillaries, veins).
• The definition and structure of the mediastinum are described along with its surrounding tissue, nerves, blood and lymph vessels, lymph nodes and fat. Volume changes within the mediastinum are also discussed.
• The pericardium is described as a double-walled fibrous sac enclosing the heart and roots of great vessels including tough, thick outer layer, attached to outer layer of great vessels, and central tendon of the diaphragm.
• The inner double layered sac (serous pericardium) has parietal pericardium (outer layer) and visceral pericardium (inner layer).
• The pericardial cavity is thin and filled with serous fluid, allowing the heart to beat frictionlessly.
• Clinical notes cover pericarditis (inflammation of the pericardium) that can present as substernal pain and pericardial effusion. Pericardial rubs are also mentioned.
• The heart is a muscular pump propelling blood via blood vessels throughout the body. It's pyramidal/cone-shaped, located 2/3 to the left of the median plane, and contained within the pericardial sac.
• Specific anatomical features include the apex (found in the 5th intercostal space, midclavicular line, and tip of the left ventricle), and the base (formed by the two atria, located in the 2nd intercostal space).
• Heart layers (epicardium, endocardium, myocardium) are presented and their responsibilities.
• The myocardium contains most myocardial fibers working to contract the heart as well as special fibers of myocardial muscle forming the conduction system (SA and AV nodes, AV bundle, and Purkinje fibers).
• Two structural categories of myocardial cells are presented (mechanical and conductive).
• The metabolic processes in the myocardium are almost exclusively aerobic.
• Coronary sulcuses/grooves (aka atrioventricular sulcus/groove, coronary sinus, anterior interventricular sulcus) are highlighted.
• The cardiac skeleton, composed of annulus/fibrosus(fibrocartilaginous tissue) separates atria from ventricles, acts as electrical insulation, and supports the valves.
• Blood (review content) is composed of red blood cells (RBC), white blood cells (WBC), platelets, and plasma.
• The presentation includes 2 detailed heart anatomy diagrams.
• The heart consists of two sides with four chambers––two upper chambers (receiving areas) and two lower chambers (discharging areas).
• Blood volume in pulmonary circulation is equal to systemic circulation volume. Pulmonary arterial pressure is 1/6th of systemic pressure.
• The right atrium has a thin muscular wall and receives venous blood (superior and inferior vena cava and coronary sinus, during diastole). The SA node is located within the posterior wall of the right atrium and fossa ovalis.
• The right atrium has pectinate muscles and clinical note covering orthotopic heart transplants.
• Atrioventricular (AV) valves separate the atria and ventricle, and allow for one-way blood flow. Structures such as the valvular orifice surrounded by an annulus, leaflet/cusps, chordae tendineae, papillary muscles, and trabeculae carneae are also discussed.
• The presentation describes the structure and location of the tricuspid valve.
• The Right Ventricle receives blood from the right atrium via the tricuspid valve and pumps blood into pulmonary artery via pulmonary valve. It's shaped like a crescent, has a thin myocardial wall, and is divided into two portions (body and infundibulum/conus arteriosus).
• The Right Ventricle's resistance of pulmonary circulation is approximately one tenth that of systemic circulation.
• Specific values for normal systolic and diastolic pressures are provided.
• Semilunar valves (3 leaflets/cusps––anterior, right, and left), pulmonary valve, and aortic valve are described and their functions discussed (prevent backflow).
• Locations of the pulmonary and aortic valves are detailed.
• Detailed description of the Left Atrium - structure, function, and the role of the mitral valve.
• Mitral valve insufficiency/problems are discussed along with related clinical notes on diseases specific to the mitral valve.
• The Left Ventricle is a conically shaped cavity that forms the apex of the heart. It receives blood from the left atrium via the mitral valve and pumps blood into the aorta, which completes systemic circulation via the aortic valve. It comprises nearly the entire left border and inferior wall of the heart and has a thick muscular wall two to three times thicker than the right ventricle.
• The Left Ventricle contains two sections, inflow and outflow tracts. Large papillary muscles form chordae tendineae which attach to the mitral valve cusps.
• The Ventricular Septum partitions the ventricles and includes both muscular and membranous parts.
• The Aortic Valve and its structure and location are discussed.
• General anatomic locations of valves (relative to the chest) are shown graphically.
• The Great Vessels are described as primary blood vessels and includes the Vena Cava (SVC and IVC), Pulmonary veins (4 veins, 2 from each lung), pulmonary arteries (2 arteries), and the Aorta.
• The basic design of blood vessels, composed of three layers (tunics)––Tunica Intima: innermost layer, Tunica Media: mainly smooth muscle, Tunica Adventitia or Externa: contains both elastic and collagenous fibers—is explained.
• Details of arteries, veins, and capillaries are discussed including the smallest blood vessels and the relationship to arterioles and venules.
• Lymphatics are compared to vascular capillaries; they start in tissues as blind-ended tubes that increase in size becoming larger lymph vessels. Lymphatic valves prevent backflow. Lymphatic vessels carry lymph, and lymph passes through lymph nodes.
• The aorta is the largest artery in the body. Coronary arteries, branching from the aorta, supply the heart muscle. Its three main branches from its arch are the brachiocephalic artery, the carotid artery, and the subclavian artery.
• The aorta's make-up includes the ascending aorta, aortic arch, descending aorta, which further divides into thoracic and abdominal aorta. Aortic sinuses, an anatomic dilation of the ascending aorta, are presented (generally 3 aortic sinuses, from which right and left coronary arteries arise), preventing cusps of the aortic valve from sticking.
• Circulation to the heart - The right and left side of the heart are reviewed (detailing their functions and processes). Focus is on blood flow between heart chambers and between the heart and various sections of the body.
• The coronary and arterial supply to the heart muscle discusses the arising source of this blood (right and left coronary artery), grooves for pathways around the heart, and what determines right vs. left coronary dominance (crux of the heart and AV node supply).
• Coronary arteries are branches arising from the aorta, which travel in the heart in grooves, giving rise to perforating arteries that further reach deep into the myocardium. The heart has about 1 capillary for each muscle cell.
• Details on the Left Coronary Artery (LCA), particularly the left anterior descending (LAD), and the left circumflex (LCX) are provided. Details on the Right Coronary Artery are highlighted along with its branches, including right marginal branch, and posterior descending artery.
• The right coronary artery, detailed for function and supplying blood to specific areas including the right atrium, right ventricle, interventricular septum, and the inferior wall of the left ventricle. This artery is also highlighted as providing blood to the SA and AV nodes.
• Venous drainage of the heart is described and focuses on the coronary veins' tendency to follow coronary arteries, collection of deoxygenated blood from the myocardium, and the primary role of the coronary sinus. The coronary sinus empties into the right atrium and receives blood from the great cardiac vein, middle cardiac vein, and small cardiac vein––with the smallest being the thebesian veins.
• Functions of the heart and cardiovascular system, including delivering oxygen and nutrients to tissues, removing carbon dioxide and waste products, transporting heat to maintain body temperature, and transporting white blood cells to fight infection.
• Summary of electrical and mechanical systems, discussion of conduction video links, and the electrical, mechanical systems - discussion includes: resting cardiac muscle (myocardium), depolarization, repolarization, and recovery.
• Electrocardiogram (EKG) records electrical activity, provides information on the heart's function and structure, and records depolarization and repolarization data ( P wave, QRS, T wave).
• The conduction system of the heart covers: sinoatrial (SA) node, internodal pathways, atrioventricular (AV) node, bundle of His, bundle branches, and Purkinje fibers.
• The SA node function ("pacemaker”) provides the normal innate rate of impulse generation (60-100 bpm). The location is at the superior vena cava and right atrial junction. It initiates the cardiac cycle via action potentials leading to depolarization which spreads through the atria. The SA node stimulates the AV node via internodal tracts.
• The atrioventricular (AV) node receives impulses from the SA node, conducts them to the bundle of His, and slows the process to allow time for atrial filling of the ventricles. The average intrinsic rate is 40-60 bpm. The function and processes of impulse transmission in a normal heart, associated with the AV node, are highlighted.
• The bundle of His divides into left and right bundle branches and terminates into Purkinje fibers which stimulate ventricular contraction with a rate of ~20-40 bpm.
• Heart rate discussion of pacemakers, particularly focusing on the different intrinsic rates of the SA node, the AV node, and the bundle of His/Purkinje Fibers (normal heart rates).
• Consideration of clinical notes associated with conduction system abnormalities and its relevance to ECG abnormal readings and myocardial infarction.
• Fundamental properties of myocardial cells (automaticity, rhythmicity, conductivity, and excitability) discussed––properties critical to the operation of the heart's conduction system.
• Innervation of the cardiovascular system (ANS): sympathetic and parasympathetic divisions.
• The sympathetic system dominates in stressful situations, increasing heart rate and cardiac output(CO). The parasympathetic system dominates in relaxed states, decreasing heart rate and lowering oxygen demand.
• The cardiac plexus is nerve tissue located anterior to the tracheal bifurcation, made up of sympathetic parasympathetic nerves. Neurotransmitters like norepinephrine and acetylcholine reach their receptors via this plexus.
• A diagram/description of the autonomic innervation of the heart is provided, covering the sympathetic and parasympathetic pathways.
• Neural summary for nerve supply (sympathetic and parasympathetic) including factors that increase heart rate, speed of contraction, and force of contraction as well as factors slowing heart rate (“fight or flight” considerations).
• Cardiac reflex mechanisms including baroreceptors (High and Low BP), chemoreceptors, and stimulation of stretch receptors to regulate heart rate.
• The description of the Cardiac Cycle includes two phases––diastole (ventricular relaxation) and systole (ventricular contraction) providing a timeline for each phase. A video link for this topic is referenced. The presentation provides details on the stages of the heart cycle, including various stages of diastole (Mid and Late Diastole) and systole (Early Systole, Late Systole), and then early diastole.
• The cardiac cycle includes specific values for phases like atrial systole, atrial diastole, ventricular systole, and ventricular diastole.
• Cardiac output (CO) is defined as the amount of blood ejected by the left ventricle into the aorta per minute (HRxSV). Venous return is the amount of blood returned to the right atria per minute; stroke volume (SV) is the amount of blood ejected by each ventricle during one contraction, affected by preload, contractility, and afterload.
• Preload is the pressure in the left ventricle before contraction, related to the stretch of muscle fibers at the end of diastole as described in the Frank-Starling Mechanism. Compliance is tied into preload; compliance describes the relationship between pressure and volume as it changes in the ventricles. The presentation identifies a relationship between preload (LV end diastolic pressure, the volume at the end of diastole) and EDV.
• Contractility is the muscle fibers’ integrity and effectiveness in force and rate, and how it's affected by changes in rate (especially > 120 bpm). The presentation notes that if muscle becomes hypertrophied, filling time, volume per beat, and effectiveness decrease.
• Afterload is described as resistance, pressure, or impedance the ventricle works against to eject blood. It's dependent on the volume/mass, size/thickness of the ventricle, and vascular impedance. There is an inverse relationship between afterload and stroke volume. An increase in afterload causes a decrease in stroke volume.
• Frank-Starling Mechanism describes the relationship between ventricular filling pressure, end-diastolic volume, and ventricular mechanical activity. Optimal filling pressure ranges for the left ventricle (LV) are found. The relationship between pressure and stretch of muscle fibers is also described in detail along with how it can impact performance if pressure is too high or too low.
• A graphic representation of the Frank-Starling mechanism shows that there's an optimal range for pressure related to myocardial fiber stretch. Changes outside these pressure ranges affect performance.
• Heart cycle summary videos are cited.