Exam 21 - Intro to Cardiac I

Cardiovascular System Overview

• The cardiovascular system pumps blood throughout the body
• It facilitates the transport of oxygen and nutrients to cells
• It removes waste products
• The heart pumps about 1,000 gallons of blood each day
• The heart beats around 100,000 times a day
• The heart transports blood through 60,000 miles of blood vessels
• The heart sits in the chest cavity between the lungs, in the mediastinum
• Two-thirds of the heart lie to the left of the midline
• The wider base is superior, below the second rib
• The apex is inferior, slightly to the left between the fifth and sixth ribs near the diaphragm

Heart Wall Layers

• The pericardium is the outermost, double-layered serous membrane
• It covers the heart
• It has serous fluid for friction-free movement while the heart contracts and relaxes
• The myocardium is the thickest, strongest middle layer
• It is cardiac muscule tissues responsible for pumping blood
• The endocardium is the innermost, thin layer
• It's made of connective tissue

Heart Chambers and Blood Flow

• The heart functions using two separate pumps
• The right side receives deoxygenated blood and pumps it to the lungs
• The left side receives oxygenated blood from the lungs and pumps it throughout the body
• The heart is divided into right and left halves by the septum
• The heart has four chambers
• The right atrium receives deoxygenated blood from the body
• It arrives via the superior vena cava (head, neck, and arms), inferior vena cava (lower body), and coronary sinus (heart muscle)
• The right ventricle receives deoxygenated blood from the right atrium
• It pumps it to the lungs via the pulmonary artery
• The left atrium receives oxygenated blood from the lungs via the pulmonary veins
• The left ventricle receives oxygenated blood from the left atrium
• It pumps it to the body
• The left ventricle is the thickest, most muscular chamber

Heart Valves

• Four valves ensure blood flows in one direction, preventing backflow
• Atrioventricular valves include the tricuspid and mitral valves
• The tricuspid valve sits between the right atrium and ventricle, having three cusps
• The mitral valve sits between the left atrium and ventricle, having two cusps
• Semilunar valves include the pulmonary and aortic valves
• The pulmonary valve sits between the right ventricle and the pulmonary artery, having three cusps
• The aortic valve sits between the left ventricle and the aorta, having three cusps

Electrical Conduction System

• Specialized tissue masses in the heart wall form the electrical conduction system
• Automaticity: The heart's inherent ability to contract rhythmically
• Irritability: The ability to respond to stimuli like nerve cells
• The autonomic nervous system controls the heart
• The sympathetic nervous system causes arterial vasoconstriction
• It increases contraction force and accelerates AV conduction time
• The parasympathetic nervous system decreases sinus node discharge
• It slows conduction through the AV node
• The sino-atrial (SA) node (pacemaker) is in the right atrium
• It regulates heartbeat and causes atrial contraction
• The atrioventricular (AV) node is in the lower posterior atrium
• It delays impulses for complete atrial contraction and ventricular filling
• The Bundle of His, in the interventricular septum, divides into left and right bundle branches and Purkinje fibers, causing ventricular contraction

Cardiac Cycle and Heart Sounds

• A cardiac cycle is one complete heartbeat
• Atria contract while ventricles relax, and ventricles contract while atria relax
• Diastole is the relaxation phase
• Systole is the contraction phase
• One cardiac cycle takes about 0.8 seconds
• Heart sounds come from valve closure
• "Lub" or S1 happens when AV valves (tricuspid and mitral) close
• "Dub" or S2 happens when semilunar valves (pulmonic and aortic) close
• Heart murmurs, swishing sounds, can mean valve closure issues or other abnormalities
• Murmurs can be rumbling, blowing, harsh, or musical
• Assess murmurs identifying the sound, anatomical location, loudness, and intensity
• Grading murmurs ranges from Grade I (low intensity, not easily audible) to Grade VI (loudest intensity)

Circulation

• Blood vessels are arteries, veins, and capillaries
• Arteries carry blood away from the heart
• Veins carry blood back to the heart
• Capillaries allow oxygen and nutrients to exchange within tissues
• Systemic circulation pumps blood from the left ventricle to all body parts
• It returns to the right atrium, delivering oxygen/nutrients and removing waste
• Coronary arteries (right and left) branch off from the aorta
• They perfuse the myocardium
• The right coronary artery perfuses the right atrium, right ventricle, and the posterior left ventricle part
• The left coronary artery supplies blood to the anterior wall and apex of the left ventricle
• Pulmonary circulation pumps deoxygenated blood from the right ventricle to the lungs
• It returns to the left atrium
• Deoxygenated blood moves via arteries and oxygenated blood moves via veins in pulmonary circulation

Cardiac Output

• Cardiac output (CO) comes from heart rate and stroke volume
• Preload: Ventricular stretch before contraction, influenced by blood volume at end-diastole
• Afterload: Ventricles must overcome this resistance to deliver stroke volume
• Contractility: Strength of myocardial muscle fiber shortening during systole influenced by preload

Diagnostic Tests

• Chest radiography shows heart size, shape, position, and outline
• Fluoroscopy (action-motion radiograph) observes movement during procedures like pacemaker placement
• Angiograms use radiographs after injecting contrast dye
• They diagnose vessel occlusion and congenital anomalies
• Nursing role: Check for allergies (iodine, shellfish), get consent, monitor the catheter insertion site for bleeding, check circulation and monitor vital signs
• Cardiac catheterization visualizes heart chambers, valves, vessels, and coronary arteries
• Cardiac catheterization diagnoses cardiac pathology, measures heart pressures, assesses blood, determines valvular defects, and looks at angiography
• Pre- and post-procedure care for cardiac catheterization includes monitoring for occlusion, hypoxemia, hemorrhage, dysrhythmias, and pulmonary emboli and maintain awareness of patient status changes
• Electrocardiogram (EKG) graphs hearts conduction system
• Ten electrodes (six chest leads, four limb leads) view the heart from twelve different angles
• Heart monitors continuously monitor heart rhythm and electrical activity
• Ambulatory or Holter monitors watch rhythms 12-48 hours at home
• It's used for suspected cardiac disease with normal resting rhythm
• Exercise-stress testing measures heart capacity under exertion
• It evaluates myocardial ischemia and dysrhythmias
• Thallium scanning uses a radioactive isotope to detect ischemic or infarcted myocardial tissue ("cold spots")
• Echocardiography uses ultrasound of heart size, shape, motion, and ejection fraction

Laboratory Tests

• Coagulation studies are used for patients on anticoagulants (heparin, Coumadin)
• They measure PTT (for heparin) and PT/INR (for Coumadin)
• Cardiac enzymes: levels of Troponin I (gold standard) are measured
• It's a cardiac specific marker to look for myocardial damaged
• It rises in 3 hours after MI, peaks at 14-18 hours, and remains elevated for 2-3 weeks
• B-type natriuretic peptide (BNP): is measured
• It's a hormone secreted to respond to ventricle expansion/pressure overload
• A level above 100 pg/ml indicates heart failure (HF)
• Higher BNP levels indicates more dangerous HF

Interventional Cardiology

• Intervention cardiology is used to treat acure MI
• Primary PCI is recommended for acute STEMI
• It reduces ischemia and prevent myocardial damage
• It includes PTCA, rotational atherectomy, laser atherectomy, thrombectomy, intracoronary stenting
• Percutaneous Transluminal Coronary Angioplasty (PTCA) compresses intracoronary plaque to increase blood flow
• A coronary stent, a tube, is used to widen the lumen
• It squeezes plaque against the artery walls, providing structural support