Cardiac Alterations

Cardiac Alterations

1. Depolarization= electrical activation; caused by influx of sodium into cell while potassium exits

2. Repolarization: resting state of cell; caused by potassium reentry into cell while sodium exits

3. Cardiac Action Potential

   • Refractory Periods= Effective and Relative
     • Relative RP: phase where cells require stronger than normal stimulus in order to depolarize
     • Effective RP: phase where cell is unable to depolarize

4. Cardiac Cycle: events occuring in heart from beginning of one beat to the next; cycle # depends on HR

   • 3 Major Sequential Events= Diastole; Atrial Systole; Ventricular Systole

5. Cardiac Output: amount of blood pumped by ventricle in L/min; CO= SV x HR

   • Contractility: Ability of cardiac muscle to shorten in response to electrical impulse
   • Afterload: resistance to blood ejection from ventricle
   • Preload: degree of stretch of cardiac muscle at end of diastole
   • Ejection Fraction: % of end diastolic VL ejected w/ each heart beat

6. HR: controlled by ANS and baroreceptors;

7. SV: controlled by preload (Frank-Starling Law) & afterload (by systemic vascular + pulmonary vascular resistance

8. CV System Assessment

   • Health History; Demographic Information; Genetic/Family History; Cultural/Social factors
   • Risk Factors: modifiable; nonmodifiable
   • Physical Assessments: gen. appearance; skin/extremities; pulse pressure; bp/orthos. changes; arterial pulses; heart insp., palpation, ausc.
   • Health/Family/Social Hist Asses.: *11 FHP
   • Lab Tests: Blood chem.; hematology; coagulation; brain natriuretic peptide

9. Monitors/Imaging/Diagnostic Tests

   • Electrocardiaography= 12 lead EKG; Continuous monitoring= telemetry; ambulatory; hardwire
   • Cardiac Stress Testing= exercise: pt on treadmill; ekg./ v.s/ symp. monitored
   • Pharmacologic stress testing: vasodilating agents given to mimic exercise
   • Echocardiography: noninvasive ultrasound test used to: measure ejection fraction; examin size, shape, motion of cardiac structures
     • Transthoracic: looks at motion of heart, how it moves
   • Hemodynamic Monitoring: central venous pressure; pulmonary art. pressure; intra-arterial b/p monitoring

10. Cardiac Catheterization: invasive procedure used to diagnose structural/functional heart diseases and great vessels

    • Nursing Inter.: observe cath site for bleeding/hematoma; assess peripheral pulses; assess temp, color, and cap refill of affected extremity; screen for dysrhyth.; bed rest 2-6 hrs; tell pt to report chest pain, bleeding;

11. Values to watch for MI: creatinine kinase (CK; cardiac specific enzyme released in an hour and peaks at 24), Troponin T and I (myocardial muscle protein released when heart muscle damaged), and myoglobin (protein found in skeletal and cardiac); these values are increased during MI