Chapter 31 Assessment of Cardiovascular System Flashcards
The heart ♣ Has four chambers: ♣ Is composed of three layers: o Is surrounded by a? o Has four valves:
♣ Has four chambers: the right and left atrium and right and left ventricles.
♣ Is composed of three layers: endocardium (thin inner lining), myocardium (layer of muscle), and epicardium (outer layer).
o Is surrounded by a fibroserous sac called the pericardium.
o Has four valves: mitral, aortic, tricuspid, and pulmonary. These maintain the one-way flow of blood.
Heart: The thickness of the wall of each chamber is different. The atrial myocardium is thinner than that of the ventricles, and the left ventricular wall is two or three times thicker than the right ventricular wall. The thickness of the left ventricle is necessary to?
produce the force needed to pump the blood into the systemic circulation.
Blood flow:
1, The right atrium receives venous blood from the inferior and superior venae cavae and the coronary sinus. The blood then passes through the tricuspid valve into the right ventricle.
2, With each contraction, the right ventricle pumps blood through the pulmonic valve into the pulmonary artery and to the lungs.
3, Oxygenated blood flows from the lungs to the left atrium by way of the pulmonary veins.
4, It then passes through the mitral valve and into the left ventricle.
5, As the heart contracts, blood is ejected through the aortic valve into the aorta and thus enters the systemic circulation.
The right side of the heart receives venous blood from the body (via the vena cava) and pumps it to the lungs where it is oxygenated. Blood returns to the?
left side of the heart (via the pulmonary veins) and is pumped to the body via the aorta.
The pulmonic and aortic valves (also known as semilunar valves) prevent blood from?.
regurgitating into the ventricles at the end of each ventricular contraction.
Blood supply to myocardium: The myocardium has its own blood supply, the coronary circulation. Blood flow into the two major coronary arteries occurs primarily during diastole (relaxation of the myocardium). The left coronary artery arises from the aorta and divides into two main branches: the left anterior descending artery and left circumflex artery. These arteries supply the left atrium, left ventricle, interventricular septum, and a portion of the right ventricle. The right coronary artery also arises from the aorta, and its branches supply the right atrium, right ventricle, and a portion of the posterior wall of the left ventricle. In 90% of people the atrioventricular (AV) node and the bundle of His receive blood supply from the?
right coronary artery. For this reason, blockage of this artery often causes serious defects in cardiac conduction.
Blood flow into the two major coronary arteries occurs primarily during?
diastole (relaxation of the myocardium)
Blood supply to myocardium: The divisions of coronary veins parallel the coronary arteries. Most of the blood from the coronary system drains into the?
coronary sinus (a large channel), which empties into the right atrium near the entrance of the inferior vena cava.
Conduction system: consists of specialized tissue responsible for creating and transporting electrical impulse (action potential). This impulse starts depolarization of the heart cells and subsequently heart contraction. The electrical impulse begins in the?
1) sinoatrial (SA) node (pacemaker of the heart). Each impulse coming from SA node travels through interatrial pathways to depolarize the atria, resulting in a contraction.
2) electrical impulse travels from atria to AV node through internodal pathways.
3) signal then moves through bundle of His and left and right bundle branches. left bundle branch has two fascicles (divisions): anterior and posterior. action potential moves through walls of both ventricles by means of Purkinje fibers.
4) ventricular conduction system delivers the impulse within 0.12 second. This triggers a synchronized right and left ventricular contraction and ejection of blood into the pulmonary and systemic circulations.
5) repolarization occurs when contractile fiber cells and conduction pathway cells regain resting polarized condition. Heart muscle cells have a compensatory mechanism that makes them unresponsive or refractory to restimulation during the action potential. During ventricular contraction, there is an absolute refractory period during which heart muscle does not respond to any stimuli. After this period, heart muscle gradually recovers its excitability, and a relative refractory period occurs by early diastole.
The coronary circulation provides blood to the myocardium (heart muscle). The right and left coronary arteries are the?
first two branches off the aorta.
The conduction system consists of specialized cells that create and transport electrical impulses. These electrical impulses initiate?
depolarization of the myocardium. This triggers a cardiac contraction.
Each electrical impulse starts at the?
SA node (located in the right atrium), travels to the AV node (located at the atrioventricular junction), through the bundle of His, down the right and left bundle branches (located in the ventricular septum), and ends in the Purkinje fibers.
Electrocardiogram: The letters P, QRS, T, and U are used to identify the separate waveforms.
1) P wave, begins with the firing of the SA node and represents depolarization of the atria.
2) The QRS complex represents depolarization from the AV node throughout the ventricles.
* There is a delay of impulse transmission through the AV node that accounts for the time between the beginning of the P wave and the beginning of the QRS wave.
3) The T wave represents repolarization of the ventricles. 4) The U wave, if seen, may represent repolarization of the Purkinje fibers, or it may be associated with hypokalemia.
Electrocardiogram: Intervals between these waves (PR, QRS, and QT intervals) reflect the time it takes for the signal to travel from one area of the heart to another. These time intervals are?
measured, and changes from these time references often indicate pathologic conditions
Mechanical System.
Depolarization triggers mechanical activity.
1) Systole, contraction of the heart muscle, results in?
2) Relaxation of the heart muscle, diastole, allows for?
3) Cardiac output (CO), the amount of?
1) ejection of blood from the ventricles.
2) filling of the ventricles.
3) blood pumped by each ventricle in 1 minute, is calculated by multiplying the amount of blood ejected from the ventricle with each heartbeat: stroke volume (SV) times heart rate (HR) per minute: CO = SV x HR
1) For the normal adult at rest, CO is maintained in the range of?
2) Cardiac index (CI) is the?
3) The CI adjusts the CO to the body size. The normal CI is?
1) 4 to 8 L/min
2) CO divided by the body surface area (BSA).
3) 2.8 to 4.2 L per minute per meter squared (L/min/m2)
Amount of blood ejected with each heart beat
Stroke volume
Amount of blood pumped by each ventricle in 1 minute
Normal:
Cardiac output: Amount of blood pumped by each ventricle in 1 minute
Normal 4-8 L/min
Cardiac index:
Normal:
Cardiac index: CO divided by body surface area
Normal 2.8-4.2 L/min/m2
Factors Affecting Cardiac Output.
Numerous factors can affect either the HR or SV, and thus the CO. The HR, which is controlled primarily by the autonomic nervous system, can reach as high as 180 beats/min for short periods without harmful effects. The factors affecting the SV are?
preload, contractility, and afterload. Increasing preload, contractility, and afterload increases the workload of the heart muscle, resulting in increased O2 demand.
Frank-Starling law states that, to a point, the more the myocardial fibers are stretched, the greater their force of contraction. The volume of blood in the ventricles at the end of diastole, before the next contraction, is called preload. Preload determines the amount of?
stretch placed on myocardial fibers. Preload can be increased by a number of conditions such as hypertension, aortic valve disease, and hypervolemia
Factors affecting cardiac output: Contractility can be increased by?
epinephrine and norepinephrine released by the sympathetic nervous system. Increasing contractility raises the SV by increasing ventricular emptying.
Factors affecting cardiac output:
1) Afterload is the?
2) Afterload is affected by the?
1) peripheral resistance against which the left ventricle must pump.
2) size of the ventricle, wall tension, and arterial blood pressure (BP). If the arterial BP is elevated, the ventricles meet increased resistance to ejection of blood, increasing the work demand. Eventually this results in ventricular hypertrophy, an enlargement of the heart muscle without an increase in CO or the size of chambers
Factors Affecting Cardiac Output
1) Preload: Volume of blood in ventricles at the end of diastole
2) Contractility
3) Afterload: Peripheral resistance against which the left ventricle must pump
A patient is receiving a drug that decreases afterload. To evaluate the patient's response to this drug, what is most important for the nurse to assess? A. Heart rate B. Lung sounds C. Blood pressure D. Jugular venous distention
C. Blood pressure (trying to reduce afterload so we must reduce BP)
The cardiovascular system must respond to numerous situations in health and illness (e.g., exercise, stress, hypovolemia). The ability to respond to these demands by altering CO is termed?
cardiac reserve
Factors affecting SV are preload, contractility, and afterload.
- Preload is the volume of blood in the ventricles at the end of diastole
- afterload represents the systemic resistance against which the left ventricle must pump.
Blood Vessels.
The three major types of blood vessels in the vascular system are the arteries, veins, and capillaries.
- Arteries, except for the pulmonary artery, carry oxygenated blood away from the heart.
- Veins, except for the pulmonary veins, carry deoxygenated blood toward the heart.
- Small branches of arteries and veins are arterioles and venules.
- Blood circulates from the left side of the heart into arteries, arterioles, capillaries, venules, and veins, and then back to the right side of the heart.
Heart structure: The arterial system differs from the venous system by the amount and type of tissue that make up arterial walls. The large arteries have thick walls composed mainly of elastic tissue. This elastic property cushions the impact of the pressure created by ventricular contraction and provides recoil that propels blood forward into the circulation. Large arteries also contain some?
smooth muscle. Examples of large arteries are the aorta and pulmonary artery.
Arterioles have relatively little elastic tissue and more smooth muscle. Arterioles serve as the major control of?
arterial BP and distribution of blood flow. They respond readily to local conditions such as low O2 and increasing levels of CO2 by dilating or constricting.
The innermost lining of the arteries is the endothelium. The endothelium maintains hemostasis, promotes blood flow, and, under normal conditions, inhibits blood coagulation. When the endothelial surface is disrupted what happens?
(e.g., rupture of an atherosclerotic plaque), the coagulation cascade is initiated and results in the formation of a fibrin clot.
Capillaries.
The thin capillary wall, made up of endothelial cells, has no elastic or muscle tissue. The exchange of cellular?
nutrients and metabolic end products takes place through these thin-walled vessels. Capillaries connect the arterioles and venules.
Heart structure: Veins are large-diameter, thin-walled vessels that return blood to the right atrium.
1) The venous system is a?
2) The larger veins contain semilunar valves at intervals to maintain the?
3) The amount of blood in the venous system is affected by a number of factors, including?
1) low-pressure, high-volume system.
2) blood flow toward the heart and to prevent backward flow.
3) arterial flow, compression of veins by skeletal muscles, alterations in thoracic and abdominal pressures, and right atrial pressure.
The largest veins are the superior vena cava, which returns blood to the heart from the head, neck, and arms, and the inferior vena cava, which returns blood to the heart from the lower part of the body. These large-diameter vessels are affected by the?
pressure in the right side of the heart. Elevated right atrial pressure can cause distended neck veins or liver engorgement as a result of resistance to blood flow.
Venules are relatively small vessels made up of a small amount of?
muscle and connective tissue. Venules collect blood from the capillary beds and channel it to the larger veins.
Regulation of the cardiovascular system
1) Autonomic nervous system
- Sympathetic
- Parasympathetic
2) Baroreceptors
3) Chemoreceptors
Effect on Heart.
Stimulation of the sympathetic nervous system increases?
HR, speed of impulse conduction through the AV node, and force of atrial and ventricular contractions. This effect is mediated by specific sites in the heart called beta (β)-adrenergic receptors, which are receptors for norepinephrine and epinephrine.
Effect on heart: stimulation of the parasympathetic system (mediated by the vagus nerve) does what?
slows the HR by decreasing the impulses from the SA node and thus conduction through the AV node.
Effect on Blood Vessels.
The source of neural control of blood vessels is the sympathetic nervous system. The alpha1 (α1)-adrenergic receptors are located in?
vascular smooth muscles. Stimulation of α1-adrenergic receptors results in vasoconstriction. Decreased stimulation to α1-adrenergic receptors causes vasodilation.
Effect on blood vessels: The parasympathetic nerves have selective?
distribution in the blood vessels. For example, blood vessels in skeletal muscle do not receive parasympathetic input.
Baroreceptors in the aortic arch and carotid sinus (at the origin of the internal carotid artery) are sensitive to?
2) Stimulation of these receptors (e.g., volume overload) sends information to the vasomotor center in the brainstem. This results in temporary?
3) Decreased arterial pressure causes?
1) sensitive to stretch or pressure within the arterial system.
2) inhibition of the sympathetic nervous system and enhancement of the parasympathetic influence, causing a decreased HR and peripheral vasodilation.
3) the opposite effect.
Chemoreceptors are located in the aortic and carotid bodies and the medulla. They are capable of causing changes in?
- When the chemoreceptors in the medulla are triggered, they?
- changes in respiratory rate and BP in response to increased arterial CO2 pressure (hypercapnia) and, to a lesser degree, decreased plasma pH (acidosis) and arterial O2 pressure (hypoxia).
- stimulate the vasomotor center to increase BP
Stimulation of baroreceptors and chemoreceptors, located in the aortic arch and carotid sinus, can initiate changes in?
HR and arterial pressure
Blood Pressure
1) The arterial blood pressure is a measure of the?
2) The systolic blood pressure (SBP) is the?
3) The diastolic blood pressure (DBP) is the?
1) pressure exerted by blood against the walls of the arterial system.
2) peak pressure exerted against the arteries when the heart contracts.
3) residual pressure in the arterial system during ventricular relaxation (or filling).
The two main factors influencing BP are?
CO and systemic vascular resistance (SVR)
BP = CO x SVR
- SVR is the force opposing the movement of blood. This force is created primarily in small arteries and arterioles. Normal blood pressure is SBP <120 mm Hg and DBP <80 mm Hg
BP can be measured by?
1) invasive techniques (catheter inserted in an artery)
2) noninvasive techniques (using a sphygmomanometer and a stethoscope, or an automated noninvasive device).
Noninvasive, indirect measurement of BP can be done with a sphygmomanometer and stethoscope. The sphygmomanometer consists of an inflatable cuff and a pressure gauge. The BP is measured by auscultating for sounds of turbulent blood flow through a compressed artery, termed?
- What is the recommended site for taking a BP?
Korotkoff sounds
- The brachial artery is the recommended site for taking a BP.
Blood pressure: Systolic blood pressure (SBP) - Diastolic blood pressure (DBP) - BP =
- Systolic blood pressure (SBP) < 120 mm Hg - Diastolic blood pressure (DBP) < 80 mm Hg - BP = CO x SVR
A mean arterial pressure (MAP) >___ mm Hg is necessary to sustain the vital organs of an average person under most conditions.
> 60 mm Hg
Pulse pressure is the?
difference between the SBP and DBP
- normally about one third of the SBP. If BP is 120/80 mm Hg, the pulse pressure is 40 mm Hg.
- increased pulse pressure due to an increased SBP may occur during exercise or in individuals with atherosclerosis of the larger arteries.
- A decreased pulse pressure may be found in heart failure or hypovolemia.
Another measurement related to BP is mean arterial pressure (MAP). The MAP refers to the?
average pressure within the arterial system that is felt by organs in the body. It is not the average of the DBP and SBP, because the length of diastole exceeds that of systole at normal HRs. MAP is calculated as follows:
MAP = (SBP + 2DBP)/3
Mean arterial pressure: A person with a BP of 120/60 mm Hg has an estimated MAP of 80 mm Hg. In patients with invasive BP monitoring, this value is automatically calculated and takes the patient’s HR into consideration. A MAP greater than 60 mm Hg is needed to?
- When the MAP falls below this number for a period of time, what happens?
- MAP greater than 60 mm Hg is needed to adequately perfuse and sustain the vital organs of an average person under most conditions.
- vital organs are underperfused and will become ischemic.
MAP Range
60-100 mm Hg
- Risk for cardiovascular disease (CVD) increases with?
- CVD leading cause of death in adults \
- Cardiovascular changes result of?
- age
- > 65 years of age
- aging, disease, environmental factors, and lifetime behaviors
Gerontologic Considerations: Effects of Aging on the Cardiovascular System
- With increased age, the amount of collagen in the heart increases and elastin decreases.
1) These changes affect the?
2) One of the major changes in the cardiovascular system is the response to physical or emotional stress. In times of increased stress, what happens?
3) The resting supine HR is not markedly affected by aging. When the patient changes positions (e.g., sits upright), the?
1) heart muscle’s ability to stretch and contract.
2) CO and SV decrease due to reduced contractility and HR response.
3) sympathetic nerve pathway may be affected by fibrous tissue and fatty deposits, resulting in a blunted (reduced) HR response
Age related changes
- Increased collagen, decreased elastin
- Decreased response to stress
- Heart valves become thick and stiff.
- Number of pacemaker cells decrease.
- Decreased number and function of β-adrenergic receptors
- Blood vessels thicken and less elastic
- Increase in SBP and decrease or no change in DBP
- Incompetent venous valves
- Orthostatic hypotension
- Postprandial hypotension
Gerontologic Considerations: Effects of Aging on the Cardiovascular System
- Heart valves become thicker and stiffer from lipid accumulation, degeneration of collagen, and fibrosis. The aortic and mitral valves are most frequently affected. These changes result in either?
regurgitation of blood when the valve should be closed or narrowing of the orifice of the valve (stenosis) when the valve should be open. The turbulent blood flow across the affected valve results in a murmur.
Gerontologic Considerations: Effects of Aging on the Cardiovascular System
- The number of pacemaker cells in the SA node decreases with age.
1) By age 75, a person may have only 10% of the normal number of pacemaker cells. Although this is compatible with adequate SA node function, it may account for the frequency of some sinus dysrhythmias in older adults. Similar decreases 663also occur in the number of conduction cells in the internodal tracts, bundle of His, and bundle branches. These changes contribute to the development of atrial dysrhythmias and heart blocks. About 50% of older adults have an abnormal resting ECG that shows increases in the PR, QRS, and/or QT intervals
The number of pacemaker cells in the SA node decreases with age. By age 75, a person may have only 10% of the normal number of pacemaker cells. Although this is compatible with adequate SA node function, it may account for the frequency of some sinus dysrhythmias in older adults. Similar decreases 663also occur in the number of conduction cells in the internodal tracts, bundle of His, and bundle branches. These changes contribute to the development of atrial dysrhythmias and heart blocks. About 50% of older adults have an abnormal resting ECG that shows increases in the PR, QRS, and/or QT intervals
Gerontologic Considerations: Effects of Aging on the Cardiovascular System
- The number of pacemaker cells in the SA node decreases with age.
1) By age 75, a person may have only?
2) Similar decreases also occur in the number of conduction cells in the?
3) About 50% of older adults have an abnormal resting ECG that shows?
1) 10% of the normal number of pacemaker cells.
2) internodal tracts, bundle of His, and bundle branches. 3) increases in the PR, QRS, and/or QT intervals
Gerontologic Considerations: Effects of Aging on the Cardiovascular System
The autonomic nervous system control of the cardiovascular system changes with aging. The number and function of β-adrenergic receptors in the heart decrease with age. So the older adult not only has a decreased response to physical and emotional stress but also is less sensitive to β-adrenergic agonist drugs. The lower maximum HR during exercise results in?
only a twofold increase in CO compared with the three or four times increase seen in younger adults.
Gerontologic Considerations: Effects of Aging on the Cardiovascular System
- Arterial and venous blood vessels thicken and become less elastic with age. Arteries increase their sensitivity to vasopressin (antidiuretic hormone). With aging both of these changes contribute to a?
- Valves in the large veins in the lower extremities have a reduced ability to?
- progressive increase in SBP and a decrease or no change in DBP. Thus an increase in the pulse pressure is found.
- return the blood to the heart, often resulting in dependent edema.
Gerontologic Considerations: Effects of Aging on the Cardiovascular System
- Orthostatic hypotension, which is estimated to be present in more than 30% of patients over age 70 with?
- Postprandial hypotension (decrease in BP of at least 20 mm Hg that occurs within 75 minutes after eating) may also occur in about?
- Both orthostatic and postprandial hypotension may be related to?
- systolic hypertension, may be related to drugs and/or decreased baroreceptor function.
- a third of otherwise healthy older adults.
- falls in older adults. Despite the changes associated with aging, the heart is able to function adequately under most circumstances.
Subjective Data: Health information
1) History of present illness
2) Past health history
3) Past and current medications
4) Surgery or other treatments
Subjective Data: Functional health patterns
1) Health perception-health management pattern
2) Nutritional-metabolic pattern
3) Elimination pattern
4) Activity-exercise pattern
Past Health History.
Many illnesses affect the cardiovascular system directly or indirectly. Ask the patient about a history of?
chest pain, SOB, fatigue, alcohol and tobacco use, anemia, rheumatic fever, streptococcal throat infections, congenital heart disease, stroke, palpitations, dizziness with position changes, syncope, hypertension, thrombophlebitis, intermittent claudication, edema, and varicosities.
Genetic Risk Alert
1) Coronary Artery Disease
2) Cardiomyopathy
3) Hypertension
1) Coronary Artery Disease
• Specific genetic links, especially related to lipoprotein genes, have been identified for some families with CAD.
• The clustering of CAD in families is strong if there is early age of onset affecting several relatives.
2) Cardiomyopathy
• Hypertrophic cardiomyopathy can be caused by autosomal dominant mutations.
• Dilated cardiomyopathy can be caused by autosomal and X-linked dominant mutations.
3) Hypertension
• Hypertension results from a complex interplay between genetic and environmental factors.
• Lifestyle choices (e.g., smoking, lack of exercise) may trigger genetic tendencies to hypertension.
Sleep-Rest Pattern.
Cardiovascular problems often disrupt sleep. Paroxysmal nocturnal dyspnea (attacks of shortness of breath, especially at night that awaken the patient) and Cheyne-Stokes respiration (periods of very shallow breaths to alternating periods of apnea and deep, rapid breathing) are associated with heart failure.
- Many patients with heart failure need to sleep with?
- Sleep apnea has been associated with an increased risk of?
- Nocturia, a common finding with?
- several pillows or upright in a chair. Note the number of pillows needed to sleep or the need to sleep upright (orthopnea) and whether this has changed recently.
- life-threatening dysrhythmias, especially in patients with heart failure
- cardiovascular patients, also interrupts normal sleep patterns. Fully explore both conditions.
