Cardiology 101 

The normal amount of blood in an adult is about 5 liters or 5.3 quarts. 

Heart Rate - number of beats in one minute 

Stroke Volume - amount of blood ejected with each beat 

Cardiac output is a measure of heart's pumping ability and is equal to the amount of blood pumped from the ventricles in one minute. It is the product of heart rate (number of heart beats in one minute) and stroke volume (the amount of blood ejected with each beat). The equation is CO = HR x SV Symptoms of decreased cardiac output are: 

• changes in mental functioning  
• decreased urine output  
• cool, clammy, pale skin  
• sweating  
• weak and rapid pulses  
• heart palpitations  
• thirst  
• nausea 

Preload is the amount of heart muscle tension at the end of a beat during diastole (muscle relaxation), and reflects the amount of blood left in ventricles after contraction. 

Afterload is the amount of heart muscle tension needed to eject blood into circulation. 

Contractility is the ability of the heart muscle fibers to expand and contract.

 Blood Pressure is the pressure exerted by blood on the wall of a blood vessel. It is measured during heart contraction (systole) and relaxation (diastole). In a healthy young adult normal blood pressure is about 120 mmHg systolic and 80 mmHg diastolic: 120/80 mmHg. 

High blood pressure is pressure greater than 140/90 mmHg. Blood pressure varies with stroke volume (the amount of blood pumped with each contraction), blood thickness (viscosity), heart rate and blood vessel resistance. Blood pressure is decreased by changing position from laying or sitting to standing, rest, sleep, and very fast, slow or irregular heart rates. Blood pressure increases with exercise, caffeine, nicotine, cold environment, eating a large meal, pain, and stress. Orthostatic Hypotension - a decrease in systolic BP of over 10 to 15 mmHg and a drop in diastolic BP upon standing up from a sitting position. This may be caused by blood pressure medications, dehydration or blood loss, peripheral vascular disease, prolonged bed rest, or aging. 

There are four different valves in heart which control blood flow between the four chambers of the heart and the pulmonary and aortic arteries: The tricuspid valve is between the right atrium and right ventricle. The pulmonic valve is between the right ventricle and the pulmonary artery. The mitral (or bicuspid) valve is between the left atrium and left ventricle. The aortic valve is between the left ventricle and the aortic artery.

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