Study Guide Cardiovascular System Objectives: Following completion of this section, the student should be able to: Describe the anatomy and physiology for the cardiovascular system. Recognize the appropriate diagnostic test and the nursing implications for both pre- and post procedure. Define the various disorders associated with the cardiovascular system. Anatomy and Physiology What is most important to remember about the cardiovascular system, is that it is system of one pump and many tubes. There is an immense complexity to this system, as the novice nurse, a basic understanding of this system is required to provide safe and effective care. Interior View of the Heart The heart consists of 4 chambers. These chambers are two (2) atria and two (2) ventricles. These are the right and left atrium and right and left ventricle. These structure transport blood to the body and lungs by pumping a coordinated fashion. When the right side of the heart contracts, the blood is injected into the pulmonary artery. This blood returns to the left atrium. Once this blood enters the left ventricle it is then injected into the aortic vessel where it will supply oxygen and nutrients to the body. The fibroserous sac that encloses and protects the heart is called the pericardium. It consists of two layers: the visceral (inner) and parietal layer (outer). Between the two layers of the pericardium is a fluid filled layer. This serous layer reduces friction when the heart contracts. The heart itself consists of three layers. They are: Epicardium: the outer layer of the muscle tissue Myocardium: the thick muscular layer in the middle Endocardium: the inner most layer The four valves of the heart prevent back-flow of the blood and are responsible for the “lub-dub” heart sounds on auscultation. These values are: Atrioventricular Values: Tricuspid: the valve that lies between the atrium and ventricle on the right side of the heart Mitral(Bicuspid) : the valve that lies between the atrium and ventricle on the left side of the heart Semilunar Values: Pulmonic: the valve between the right ventricle and the pulmonary artery Aortic semilunar: the valve between the left ventricle and the aorta. The blood supply to the heart itself is as follows: Left Coronary artery o Left anterior descending (LAD): it supplies  Anterior wall of the left ventricle  Anterior ventricular septum  Apex of the left ventricle o Circumflex artery  Left atrium  Lateral and posterior portion of the left ventricle Right Coronary artery (RAC) o The RAC gives rise to the acute marginal artery that becomes the posterior descending artery. o The RAC supplies blood to the sinoatrial (SA) and atrioventricular node (AV) nodes, the septum, as well as the right atrium and ventricle. o The Posterior descending artery supplies the left atrium and the inferior and posterior sections of the left ventricle, as well as the posterior portion of the right ventricle. The Pathway of a red blood cell through the heart: The deoxygenated blood arrives at the heart through the inferior or superior vena cava to the right atrium. It travels through the tricuspid valve to the right ventricle. Once in the ventricle it passes through the pulmonic valve to the pulmonary artery to the lung where the blood once again becomes oxygenated. It returns to the heart through the pulmonary veins. The now oxygen rich blood enters the heart through the left atrium. Once it passes through the mitral valve, it enters the left ventricle. The red blood cell once again continues its journey thought the blood once it enters the aorta. (See diagram below). The Pathway of Blood through the Cardiovascular System Heart sounds The most common sounds associated with auscultation of the heart are a result of the closure of the semilunar and atrioventricular valve. They are: S1: this is the sound of the closure of the mitral and tricuspid valve. It is heard over the mitral area. S2: the closer of the aortic and pulmonic valve creates this sound. It is heard best over the base of the heart. S3: this sound, although common in children is associated with CHF and the failure of the ventricles to eject blood. It is heard during ventricular filling. S4: this sound is associated with ventricular hypertrophy and resistance in filling. It is also associated with coronary artery disease, hypertension and aortic stenosis. It is heard during atrial contractions. Friction rubs: this sound is the result of abrasion of the pericardial surfaces secondary to inflammation. Gallops: this transient sound heard during systole and diastole. It is a result of impedance of blood flow. Murmurs: this sound is a result of blood follow through narrowing valves or incomplete closure of valves that causes a prolonged sound. The electrical conduction of the heart is as follows: The normal impulse for the heart originates in the sinoatrial (SA) node of the heart. The SA node, also known as the pacemaker of the heart, is located at the junction of the superior vena cava and the right atrium. The intrinsic rate for the SA node is 60100 beats per minute (BPM). The electrical signal then travels to the atrioventricular (AV) node. If the SA node for any reason is not functioning, the AV node will begin the contractions in the heart. The intrinsic rate for the AV node is 40-60 beats per minute. The electrical conduction continues to the Bundle of His, both right and left branches, then finally to the Purkinje fibers. (See diagram below) Electrical Conduction through the Heart Sinoatrial (SA) node Intrinsic rate: 60-100 BPM Atrioventricular (AV) node Intrinsic rate: 40-60 BPM Purkinje fibers Intrinsic rate: 30-40 BPM Bundle of His Intrinsic rate: 30-40 BPM This chain of events is what is captured on an electrocardiogram (EKG or ECG). It appears as follows. The P- wave is the depolarization of the atrium. The QRS complex is the depolarization of the ventricles. This is also the point where the atrium repolarizes; however, it is lost in the larger electrical activity of the ventricle. The T-wave is the repolarization of the ventricles. Diagnostic Tests The Diagnostic tests to be covered in this section are: Electrocardiogram 24- Hour ECG record (Holter Monitor) Cardiac Catheterization Echocardiogram Stress test Non-Stress test Hemodynamic monitoring Chest x-ray Blood chemistry test Hematologic studies Arterial blood gases Electrocardiogram (ECG): This is the graphic representation of a heart’s electrical activity. Assure the patient that this is a non-invasive test. However, it will require that the patient lie still for several minutes. 24- Hour ECG record (Holter Monitor): This is an extended reversion of the ECG. It is designed to monitor the patient’s cardiac electrical activity for a 24-hour period. The nurse is responsible to explain to the patient the purpose the procedure. The patient must be instructed the need to keep an activity diary. Advise the patient not to shower or bath during the test and that the use of microwaves and electrical shavers are prohibited. Cardiac Catheterization: This test involves the injection of radiopaque dye into the heart through the use of a catheter. Fluoroscope is used to examine the coronary arteries. This procedure can also be useful to in assessing the intracardiac pressures, oxygenation and cardiac output. Before the procedure, the nurse should instruct the patient of the follow: No food or drink after midnight Discuss any anxiety that the patient may feel Assess baseline vital signs, and peripheral pulses Ensure that the patient has given informed consent Inform the patient the symptoms of nausea, chest pain, flushing of the face or sudden urge to urinate is possible form the injection of radiopaque dye Assess the patient for any possible allergies to seafood, iodine or radiopaque dyes. After the procedure: Monitor vital signs and peripheral pulses Maintain a pressure dressing on site as well as bed rest for 8 hours Keep patients affected leg straight for 6-8 hours, if the arm is used for access keep it straight for an additional 3 hours Encourage fluids; unless contraindicated Assess for any sign of chest pain and report any complaints immediately If any bleeding occurs at the site, apply manual pressure and contact primary health care provider. Echocardiogram (Echo): This is a non-invasive examination of the heart. This test uses high frequency sound waves of varying intensity to produce images of the intra-cardiac structure as well as monitor the direction of blood flow. The nurse needs to assess the patient’s ability to lie still for 30 to 60 minutes. The nurse should also explain the procedure fully to the patient. Stress test: This test is also known as exercise ECG. This non-invasive test is designed to study the heart’s electrical activity while exercising and monitoring for signs of myocardial ischemia. The nurse is responsible to: Explain the procedure to the patient Inform the patient to avoid food and drink for 2- 4 hours before the procedure Instruct the patient to wear loose fitting clothing and supportive shoes Inform the patient to report any: o Chest pain o Shortness of breath o Leg cramps o Dizziness Perform a cardiopulmonary assessment Non-Stress test: This test, also known as nuclear cardiology, uses radioisotopes to examine the heart. The heart is monitored after the injection of isotopes. It provides images of myocardial perfusion and contractility. The nurse’s responsibilities include: Explanation of the procedure Ensure that the patient has given informed consent Assess the patient’s ability to lie still for the procedure After the procedure, assess the injection site for any signs of bleeding Hemodynamic monitoring: This diagnostic test can be a single procedure or continuous monitoring. It uses a balloon tipped catheter, flow directed pulmonary artery catheter to measure intracardiac pressures and cardiac output. The nurse is responsible to: Explain the procedure to the patient Obtain informed consent Assess insertion for any signs of infection Monitor the pressure tracing and record the results Assess for any signs of complications such as: o Arrhythmias o Hemorrhage o Clot formation o Air embolus Chest x-ray: The radiographic picture created by a chest x-ray provides an image of the size and position of the heart, as well as the other organs in the chest. The nurse’s responsibilities include the assessment of the patient’s ability to hold their breath. The nurse should also ensure that the patient removes all jewelry from the chest area. Blood chemistry test The assessment of blood chemistry includes information such as; blood urea nitrogen, creatinine, sodium, potassium, bicarbonate, glucose, magnesium, calcium, phosphorus, cholesterol, triglycerides, creatine kinase (CK), CK isoenzymes, aspirate, aminotransferase, cardiac troponin levels, myoglobin, lactate dehydrogenase (LD), LD isoenzymes. The nurse’s responsibilities include: Notation of any drug that the patient is on that might alter test results Restrict the patients exercising prior to the blood sample Withhold any IM injections, if possible, prior to the blood draw With hold any food or drink if ordered Assess for any bleeding at the site Hematologic studies: This is a process for using a blood sample to analyze and measure red and white blood cells count, erythrocyte sedimentation rate, prothrombin time, international normalized ratio, partial thromboplastin time, platelet count, hemoglobin and hematocrit levels. The nurse’s responsibilities include the assessment of any drug that might alter the result, and assessment of the venipuncture site for bleeding. Arterial blood gases: An ABG or an arterial blood gas is the assessment arterial blood to determine tissue oxygenation, ventilation and acid-base status. The nurse’s responsibilities include the following: Documentation of the patient’s temperature Document the rate and method of oxygenation if applicable After the procedure, apply direct pressure for at least 5 minutes and a pressure dressing for 30 minutes Occasionally assess the site for any signs of bleeding or hematoma Disorders of the Cardiovascular system: The disorders that will be covered in this section include: Cardiac Disorders: Angina Arrhythmias Cardiac tamponade Cardiogenic shock Cardiomyopathy Coronary Artery Disease Endocarditis Heart failure Myocardial Infarction Myocarditis Acute Pericarditis Vascular Disorders: Abdominal Aortic Aneurysm Thoracic aortic aneurysm Arterial occlusive disease Venous occlusions Hypertension Cardiac Disorders Angina: This disorder is associated with chest pain. It is the result of inadequate oxygen supply to cardiac muscle tissue. An essential point to remember is that although there is al lack of oxygen to the myocardial tissue, it does not result in cellular death. There are three types: Stable: symptoms are constant and are relieved by rest Unstable: pain increases in severity, duration and frequency. Prinzmetal (Variant): pain is unpredictable and not always relieved by rest. Associated with coronary artery vasospasm. Risk Factors: Aortic stenosis Atherosclerosis Pulmonary stenosis Activity or disease that results in an increase in metabolic demands Small-vessel disease Thromboembolism Vasospasm Clinical Manifestations: Anxiety Dyspnea Diaphoresis Epigastric pain Palpitations Usually occurs at times of: o Exertion o Emotional stress o Exposure to cold Pain may be substernal crushing or compressing; lasting 3-5 minutes Diagnostic tests: Blood chemistry Cardiac enzymes Coronary angiography ECG: would show ST-depression and T-wave inversion Holter monitor Treatments: 2-4 liters of oxygen Semi-fowler’s position Drug therapy: o Anticoagulant o Beta-blocker o Calcium channel blocker o Low-dose aspirin o Nitrates Assess cardiovascular and hemodynamic stability Monitor chest pain to clarify location, type and intensity Dietary changes: o Low fat o Low sodium o Low cholesterol Encourage weight lose Allow patient to discuss anxiety Arrhythmias: Arrhythmias refer to a host of potential abnormalities in the electrical activity for the heart. This results in irregularities of heart rate and rhythm. It can vary in severity. They most commonly seen disorders include: Atrial fibrillation Asystole Ventricular fibrillation Ventricular tachycardia Risk Factors: Congenital abnormalities Drug toxicity Degeneration of conductive tissue Heart disease Myocardial Infarction (MI) Myocardial ischemia Detailed information on each of these disorders is provided here: Atrial fibrillation: This disorder is associated with palpitations and feel faint; however, it can be asymptomatic. A diagnostic test for this disorder includes an ECG, which will not have any P waves. It appears on an EKG as: The treatment of Atrial fibrillation includes the following: Drug therapy: o Aminodarone o Digoxin o Cardizem o Procainamide o Verapamil Permanent pacemaker Radio frequency catheter ablation Synchronized cardioversion Monitor cardiovascular and hemodynamic stability Asystole: This disorder is associated with apnea, cyanosis, pulselessness and no palpable blood pressure. The ECG would show no electrical activity. The picture below shows an EKG representation of normal sinus rhythm transitioning into asystole: The treatment for this disorder includes: ACLS protocol: o Intubation o Possible transcutaneous pacing Drug therapy: o Atropine o Epinephrine Cardiopulmonary resuscitation (CPR) Buffering agents: such as sodium bicarbonate Ventricular fibrillation: This disorder is associated with; apnea, pulselessness and no palpable blood pressure. The ECG would show rapid and chaotic ventricular rhythm with wide irregular QRS complexes and no visible P-waves. It appears on an EKG as: The treatment of this disorder includes: ACLS protocol Drug therapy: o Amiodarone o Epinephrine o Lidocaine o Magnesium sulfate o Procainamide o Vasopressin CPR Defibrillation Implantable cardiac defibrillator