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Chapter 1 Cardiovascular Disorders
I. Normal cardiac anatomy, physiology, and function A. Cardiac and coronary artery anatomy (see Figure 1-1)
The left anterior descending artery is the most common site of coronary artery occlusion.
B. Cardiac cycle (see Figure 1-2)
In 10% of patients, the posterior descending artery derives from the left coronary artery.
C. Cardiac output (CO)
1. Heart rate (HR) a. Number of cardiac contractions per unit time; commonly expressed as beats per minute (bpm) b. If HR is too high (normal = 60–100 bpm), then diastolic filling is decreased 2. Stroke volume (SV) a. SV is the change in blood volume from immediately before initiation of contraction to completion of contraction (i.e., SV = end diastolic volume to end systolic volume) b. It is determined by contractility (i.e., SV = [end diastolic volume]-[end systolic volume]), preload (amount of myocardial stretch at end of diastole), and afterload (resistance ventricles must overcome to empty their contents) c. SV increases with catecholamine release, an increase in intracellular Ca, a decrease in extracellular Na, digoxin use, anxiety, and exercise d. SV decreases with β-blockers, heart failure, acidosis, and hypoxia 3. Fick principle—
a. Rate of O 2 use can be determined by comparing O 2 content in expired air to that in inhaled air; arterial and venous O 2 content can be measured directly from the corresponding vasculature b. CO increases during exercise, initially by increasing SV and later by increasing HR 4. Mean arterial pressure = CO × total peripheral resistance (TPR) = diastolic arterial pressure + 1/3 pulse pressure 5. Pulse pressure = systolic arterial pressure - diastolic arterial pressure
D. Electrocardiogram (ECG) (see Figure 1-3)
1. Measures flow of electrical impulses through the heart to provide information regarding cardiac function P.2
FIGURE 1-1 (A) Anterior and posterior views of the heart. LA, left atrium; LV, left ventricle; RA, right atrium;
I. Normal cardiac anatomy, physiology, and function A. Cardiac and coronary artery anatomy (see Figure 1-1)
The left anterior descending artery is the most common site of coronary artery occlusion.
B. Cardiac cycle (see Figure 1-2)
In 10% of patients, the posterior descending artery derives from the left coronary artery.
C. Cardiac output (CO)
1. Heart rate (HR) a. Number of cardiac contractions per unit time; commonly expressed as beats per minute (bpm) b. If HR is too high (normal = 60–100 bpm), then diastolic filling is decreased 2. Stroke volume (SV) a. SV is the change in blood volume from immediately before initiation of contraction to completion of contraction (i.e., SV = end diastolic volume to end systolic volume) b. It is determined by contractility (i.e., SV = [end diastolic volume]-[end systolic volume]), preload (amount of myocardial stretch at end of diastole), and afterload (resistance ventricles must overcome to empty their contents) c. SV increases with catecholamine release, an increase in intracellular Ca, a decrease in extracellular Na, digoxin use, anxiety, and exercise d. SV decreases with β-blockers, heart failure, acidosis, and hypoxia 3. Fick principle—
a. Rate of O 2 use can be determined by comparing O 2 content in expired air to that in inhaled air; arterial and venous O 2 content can be measured directly from the corresponding vasculature b. CO increases during exercise, initially by increasing SV and later by increasing HR 4. Mean arterial pressure = CO × total peripheral resistance (TPR) = diastolic arterial pressure + 1/3 pulse pressure 5. Pulse pressure = systolic arterial pressure - diastolic arterial pressure
D. Electrocardiogram (ECG) (see Figure 1-3)
1. Measures flow of electrical impulses through the heart to provide information regarding cardiac function P.2
FIGURE 1-1 (A) Anterior and posterior views of the heart. LA, left atrium; LV, left ventricle; RA, right atrium;