Cardiovascular System: Anatomy and Physiology

Anatomy and Physiology of the Cardiovascular System

• The cardiovascular system assessment includes health history, demographics, and family/genetic history.
• Cultural/social factors like food, drinking, and smoking are considered
• Risk factors are divided into modifiable (BP, cholesterol) and non-modifiable (age, family history, genetics).
• Common cardiovascular symptoms include chest pain/discomfort, pain in the upper body, SOB/dyspnea, peripheral edema, palpitations, and fatigue.
• Past health, medications, nutrition, elimination, activity/exercise, sleep, self-perception, roles, relationships, and coping mechanisms are important to note.
• Physical assessment involves general appearance and examination of skin and extremities for edema or cyanosis.
• Other assessments include pulse pressure, blood pressure, arterial pulses, jugular venous pulsations, inspection, palpitation, and auscultation
• Any affect on the heart can have knock on effects on every other system in the body

Anatomy of the Heart

• The heart has three tissue layers: the endocardium (lining), the myocardium (muscle), and the epicardium (serous layer).
• The pericardium, a sac surrounding the heart, consists of the visceral pericardium (covers the heart) and the parietal pericardium (lines the pericardial sac).
• Heart chambers include the atria (receive blood) and ventricles (pump blood), separated by the septum.
• Location of the heart is in the mediastinum, extending downward and to the left.
• The point of maximal impulse is at the apex of the heart, in the 5th intercostal space, midclavicular line.

Age related Cardiac Changes

• Older adults are at a higher risk for developing heart problems like being admitted to hospital
• Risk factors are modifiable like smoking, HTN and hypercholesterolemia.
• Normal age-related changes include left ventricular wall thickening, tighter valves, slower heart rate, rigid myocardium, and longer recovery periods.
• There is an increased vasovagal tone which can cause Syncope
• Considerations need to be made for doing orthostatic HR/BP
• There can be decreased baroreceptor sensitivity, loss of pacemaker cells, and cardiac rhythm disturbances (especially atrial fibrillation).

Symptoms in Women

• Gender is an important consideration for cardiac symptoms
• Women may not feel angina the same as older adults and may experience atypical angina.
• Women can describe "choking or strangling; discomfort; indigestion, tightness in abdomen”, chronic fatigue, shortness of breath, and paroxysmal nocturnal dyspnea (PND).

ECG Electrode Placement

• The client needs to disrobe above the waist and remove any jewelry
• Chest hair needs to be clipped if lead placement is not possible.
• Limb leads should be placed on the limbs and ensure white is on the right
• Properly identify the patient with two identifiers
• Explain the procedure will not cause pain.
• The procedure needs to be performed in a supine position with HOB flat.

ECG Electrode Placement cont

• Must measure placement exactly
• Small errors can mean the difference between an accurate read
• Avoid placement over bones where possible
• If there is a lot of interference move the limb leads closer to the heart.
• If client respiration is interfering tell them to hold their breath
• Use a pillow to support the contact of the chest
• For the limb electrodes: "White on the right, Black opposite (left), Smoke over fire (black electrode), Fire (red electrode), Snow over grass (white), and Grass (green)."
• Electrocardiogram (ECG) records electrode placement (adhesion).
• The ECG can assist with interpretations of abnormalities

Heart Physiology

• Sinoatrial node (pacemaker) fires between 60-100 bpm, then atrioventricular node -> Bundle of His -> Bundle branches -> Purkinje fibers -> which causes the ventricles to contract
• The Cardiac Output is the total amount of blood ejected from one ventricle of the heart in L/min and 5-6L is normal
• Atria and Ventricles contract and relax in an organized fashion in a 2 phased cardiac cycle
• Systole the contraction phase; and Diastole is the relaxation phase
• Cardiac output is Stroke Volume times heart rate
• Stroke Volume is the volume of blood ejected by one ventricle per heartbeat (60mL normally)
• Three factors determine stroke volume which are preload (stretch of ventricular muscle), afterload (resistance to ejection), and contractility (force of contraction).
• The cardiac cycle generates 2 heart sounds with each heartbeat audible with a stethoscope

Heart Sounds

• S1 is the first heart sound is the closure of the mitral and tricuspid valves (Lub)
• S2 is the second heart sound is the closure of the aortic and pulmonic valves (Dub)
• S3 and S4 are abnormal heart sounds like murmurs and friction rubs
• Murmurs mean turbulent blood flow through normal or abnormal valves
• Pericardial friction rub is an abornmal heart sound heard over the left sternal border

Cardiac Rythms

• The electrocardiogram records cardiac electrical activity
• Depolarization is the electrical impulse that activates the heart to contract and discharge
• Repolarization is the heart muscle relaxes
• P wave: atrial depolarization PR interval: rate of cardiac impulse transmitted from the AV node
• QRS complex: Ventricular depolarization which then contracts
• ST segment: ventricular depolarization occurs prior to ventricular repolarization
• T wave: Ventricular repolarization is occurring
• QT interval: time for ventricular repolarization to complete

Normal Sinus Rythms

• The SA node depolarizes the atria
• Ventricle depolorization occurs
• Ventricular repolarization
• Rate: Above 60-100 beats/min and Rhythm: Regular
• P waves: Present, consistent configuration, one P wave before each QRS complex
• PR interval: 0.12-0.20 second and constant QRS duration: 0.04-0.10 second and constant

Sinus Bradycardia

• Impacts overall health
• Symptomatic clients report fatigue, increased shortness of breath, dizziness or falls
• Labs should be checked: Electrolytes, Thyroid hormone panel, Troponin, Blood and Urine
• Nursing fall precautions for symptomatic bradycardia includes recognizing cues, assessing for manifestations of decreased cardiac output
• The nurse should also identify the cause of bradycardia and instruct client on lifestyle changes to decrease potential for injury.
• Treatment for unstable clients is IV atropine 1 mg repeat every 3-5 minutes not to exceed a total of 3 mg

Sinus Tachycardia

• Impacts overall health and the client may be asymptomatic or symptomatic
• Symptoms include palpitations, dizziness, lightheadedness, elevated temperature, chest pain, difficulty breathing
• Clients could be at risk to fall and if symptomatic, they should decrease physical intensity and change position slowly
• Fall precautions should be in place and any precipitating factors identified
• Reduce and discontinue substances that increase heart rate plus stress management is crucial
• Identify the underlying cause of tachycardia and interventions to decrease fever, pain, stress or anxiety performed
• Medications which may be administered include adenosine and betablockers
• In some cases catheter ablation may be an option which destroys cardiac cells responsible for increased heart rate.

More Rhythms

• Atrial Flutter is regular but there can be lightheadedness, palpitations, hypotension, Dizziness, chest discomfort and shortness of breath
• Atrial fibrillation is irregular and there is a lack of oxygen, irregular pulse, hypotension, heart palpitations, increased heart rate, Chest discomfort, Shortness of breath
• Atrial fibrillation can also show Exertional fatigue, Anxiety, Dizziness, Lightheadedness and Syncope and manifest in ways that interfere ADLs
• The client is at risk of a stroke or bleeding

Atrial Fibrillation Implementation

• With Atrial fibrillation Irregular rhythm: P waves are replaced by atrial activities between QRS
• If there is a rapid ventricular response greater than 100/min
• Interventions include Electrocardioversion, Catheter ablation, Anticoagulants and Diet modification
• Focus on client Safety and Bleeding precautions for clients on anticoagulant therapy and avoid activities like Falls or Shaving
• Blood can pool in the atrium and clot and people with AFib are on blood thinners

Supraventricular Tachycardia

• Common manifestations reported might include Dizziness, Lightheadedness, Syncopal episodes, Hypotension, Shortness of breath Palpitations or an Increased risk of falls
• Treatment includes Vagal maneuvers, IV adenosine, IV diltiazem
• Also IV esmolol or IV metoprolol can be used with a defibrillator on hand

Premature Ventricular Contractions

• Clients who are asymptomatic will be unaware of PVCs
• Symptomatic will feel palpitations lightheadedness, chest pain or shortness of breath
• Bigeminy is every other beat is a PVC but Trigeminy is when every 3rd beat is a PVC
• Blood tests cannot identify PVCs but can help identify potential causes for PVCs, like checking for Potasium, Magnesium and Thyroid levels
• Medication treatments: Beta blockers, Antiarrhythmic medications (Flecainide, Propafenone and Amiodarone) or Cathter Ablation

Heart Emergencies

• Untreated Ventricular Fibrillation will need shock
• CardioPulmonary Arrest Rythms
• Shockable Rythms: Ventricular fibrillation and Ventricular tachycardia
• Non Shockable Rythms include Cardiac Asystole and Pulseless electrical activity

Modalities and Management

• Interventions include Pacemakers, Cardioversions and Defibrillation
• Nurses are responsible for patients understanding regarding mechanical therapy
• Pacemakers are electronic devices used when meds along are inadequate to stimulate the heart
• Devices are implanted and can be permanent or temporary
• Malfunctions can occur like Infection, Bleeding or hematoma formation and Dislocation of lead

Cardioversion and Defibrillation

• Treat tachydysrhythmias with electrical current that depolarizes myocardial cells and recapture the sinus node
• Ensure current delivery is synchronized with patients ECG during cardioversion
• Current delivery is unsychronized during defibrillation
• Ensure contact between skin, pads, and paddles and the use of conductive mediums
• If cardioverting, turn synchronizer on, and use reverse for defibrillating
• Before hand it is vital that no one is in contact with patient, bed, or equipment

Testing Methods

• Lab tests for Cardiac issues focus on cardiac biomarkers and blood chemistry. Lipid profile and Brain (B-type) natriuretic peptide
• B-Natriuretic Peptide (BNP) indicates if there is lung or heart-initiated dyspnea. if levels rise its a heart problem to monitor
• Electrocardiography can assist in interpreting these issues
• Cardiac Stress Testing, either exercise or pharmacologic are useful diagnostic tools
• Myocardial cells release specific enzymes like creatine kinase [CK]), CK isoenzymes (CK-MB), and proteins (myoglobin, troponin T, and troponin I)

More Testing

• Echocardiography, a noninvasive ultrasound to measure ejection fraction or examine the size, shape, and motion of cardiac structures
• Cardiac Catheterization by radial or femoral access is Invasive procedure used to diagnose structural and functional diseases of the heart.
• Pulmonary artery pressure and oxygen saturations may be obtained with Right Heart Cath
• Left Heart Cath involves use of contrast agent and nurses need to always monitor puises