115-NCLEX-RN Review Made Incredibly Easy, Fifth Edition (Incredibly Easy...

32 Cardiovascular system

through the aortic valve to the aorta and throughout the body.

The body electricThe system that conducts electrical impulses and coordinates the hearts contractions consists of the SA node, internodal tracts, AV node, bundle of His, right and left bundle branches, and Purkinje fibers.

A normal electrical impulse is initiated at the SA node, the hearts intrinsic pacemaker, which results in the following chain of events: atrial depolarization atrial contraction impulse transmission to the AV node impulse transmission to the bundle of His, bundle branches, and Purkinje fibers ventricular depolarization ventricular contraction ventricular repolarization.

Hows it working?Cardiac function can be assessed by measuring the following parameters: Stroke volume (SV) is the amount of blood ejected from a ventricle with each beat (normally, 70 ml). Cardiac output (CO) is the total amount of blood ejected from a ventricle per minute. Cardiac output equals stroke volume multi-plied by heart rate (HR) (CO SV HR). Ejection fraction is the percent of left ventricular end-diastolic volume ejected dur-ing systole (normally, 60% to 70%).

A system of canalsBlood flows throughout the body via arteries and veins as well as through smaller

vessels such as arterioles, capillaries, and venules: Arteries are three-layered vessels (intima, media, adventitia) that carry oxygenated blood from the heart to the tissues. Arterioles are small-resistance vessels that feed into capillaries. Capillaries join arterioles to venules (larger, lower-pressured vessels than arterioles), where nutrients and wastes are exchanged. Venules join capillaries to veins. Veins are large-capacity, low-pressure vessels that return unoxygenated blood to the heart.

Think of these vessels as a series of large and small canals forming an interlocking system of blood flow.

Keep abreast of diagnostic testsHere are the most important tests used to diagnose cardiovascular disorders, along with common nursing interventions associated with each test.

Graphing the hearts electrical activityElectrocardiography is a noninvasive test that gives a graphic representation of the hearts electrical activity.

Nursing actions Determine the clients ability to lie still for several minutes.

Key treatments Surgery: open-heart surgery using cardiopulmonary bypass for valve replacement (in severe cases) Anticoagulant: warfarin (Coumadin) to prevent thrombus formation around diseased or replaced valves

Key interventions Watch closely for signs of heart failure or pulmonary edema and for adverse effects of drug therapy.

Place the client in an upright position. Maintain bed rest and provide assistance with bathing. If the client undergoes surgery, watch for hypotension, arrhythmias, and thrombus formation. Monitor vital signs, ABG levels, intake and output, daily weight, blood chemistries, chest X-rays, and pulmonary artery catheter readings.

Cardiovascular refresher (continued)

VALVULAR HEART DISEASE (CONTINUED)

Cardiac output is the total amount

of blood ejected from a ventricle per

minute.

Memory joggerTo remem-ber how

blood flows from the heart, think Arteries away and veto, for veins to.Arteries away arteries carry oxy-genated blood away from the heart to the tissues. Veto veins, by con-trast, carry blood to the heart.

313419NCLEX-RN_Chap03.indd 32313419NCLEX-RN_Chap03.indd 32 4/8/2010 7:01:37 PM4/8/2010 7:01:37 PM

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