Chapter 25 Assessment of Cardiovascular Function
1. Diastole – ventricular relaxation resulting ventricular filling
2. Systole – ventricular
... [Show More] contraction resulting in ejection of blood from the ventricles into the pulmonary artery and aorta
3. Preload – degree of stretch of the cardiac muscle fibers at the end of diastole
4. Afterload – the amount of resistance to ejection of blood from the ventricle
5. Contractility – ability of the cardiac muscle to shorten in response to an electrical impulse
6. Cardiac output – amount of blood pumped by each ventricle in liters per minute (CO = HR x SV)
7. Ejection fraction – percentage of the end-diastolic blood volume ejected from the ventricle with each heartbeat
8. Depolarization – electrical activation of a cell caused by the influx of sodium into the cell while potassium exits the cell
9. Repolarization – return of the cell to resting state, caused by reentry of potassium into the cell wall while sodium exists the cell
10. S1 – the first heart sound produced by closure of the av (mitral and tricuspid) valves
11. S2 – the 2nd heart sound produced by closure of the semilunar (aortic and pulmonic) valves
The Anatomy of the Heart
• Three layers:
o Endocardium = inner layer and lines the inside of the heart and valves
o Myocardium – middle layer, responsible for the pumping action (contraction)
• Epicardium – the exterior layer
• Heart Valves
o Atrioventricular valves = tricuspid and mitral
o Semilunar valves = pulmonic and aortic
Heart Chambers
• During diastole, the heart is in relaxation phase which allows the ventricles to fill reparation for contraction
• Systole, refers to contraction of the atria and the ventricles
• Apical Impulse (point of maximal impulse [PMI]) is heard at the intersection of the midclavicular line of the left chest wall and the 5th intercostal space
Function of the Heart
• Sinoatrial (SA) node – the primary pacemaker of the heart
o in a normal resting adult heart has an inherent firing rate of 60 to 100 impulses per
minute: rate changes in response to metabolic demands of the body
• Atrioventricular (AV) node – the secondary pacemaker of the heart
• Cardiac output – refers to the total amount of blood ejected by one of the ventricles in liters per minute
o Cardiac output in a resting adult 4 to 6 L/min
o CO=SV x HR
• Stroke volume – the amount of blood ejected from one of the ventricles per heartbeat o the average resting stroke volume is about 60 – 130 mL
• Blood Pressure
• A normal BP in adults is considered a systolic BP less than 120 mm Hg over a diastolic BP less than 80 mm Hg
• Hypertension – systolic BP that is consistently greater than 140 mm Hg or a diastolic BP greater than 90 mm Hg
• o Hypotension – an abnormally low systolic and diastolic BP lightheadedness or fainting Pulse Pressure
• Normally 30 – 40 mm Hg is an indicator of how well the patient maintains CO Pulse Rate
• Varies from a low of 50 bpm in healthy, athletic young adults and 100 bpm after exercise/excitement
Heart Auscultation
Normal Heart Sounds
• S1 – the 1st heart sound
Tricuspid and mitral valve closure
• S2 – the 2nd heart sound
Pulmonic and aortic valve closure Abnormal Heart Sounds
• S3 – 3rd heart sound
Heard early in diastole during the period of rapid ventricular filling as blood flows from the atrium into a noncompliant ventricle
• S4 – 4th heart sound
Occurs late in diastole, and is heard just before S1
• Murmurs – are created by turbulent flow of blood in the heart
Diagnostics – Laboratory Tests
• Cardiac Biomarker Analysis
• The diagnosis of MI is made by evaluating the Hx and physical examination, the ECG, and lab tests that measure serum cardiac biomarkers. The following substances leak into the interstitial spaces of the myocardium and are carried by the lymphatic system into general circulation which are then detected in serum blood samples in abnormally high levels
• Myocardial cells that become necrotic from prolonged ischemia or trauma release specific enzymes:
• Creatinine kinase [CK]
• CK isoenzymes [CK-MB]
• Proteins [myoglobin, troponin T, and troponin I] Lipid Profile
• Cholesterol, triglycerides, and lipoproteins are measured to evaluate a person’s risk of developing CAD
• Blood specimens for the lipid profile should be obtained after a 12-hour fast
• Two major sources of cholesterol are diet (animal products) and the liver (where cholesterol is synthesized)
o LDLs – are the primary transporters of cholesterol and triglycerides into the cell
• Normal: less than 160 mg/dL
• One harmful effect of LDL is the deposition of these substances in the walls of arterial vessels [Show Less]