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Systole
Period of heart contraction
Diastole
Period of heart relaxation
Cardiac cycle
Blood flow through heart during one complete heartbeat
Atrial systole
Phase where atria contract, pushing remaining 20% of blood into ventricle
End diastolic volume (EDV)
Volume of blood in each ventricle at end of ventricular diastole
Isovolumetric contraction
Phase when ventricles are completely closed, volume remains constant, ventricles continue to contract
Pressure in aorta
Reaches about 120 mm Hg during isovolumetric contraction
End systolic volume (ESV)
Volume of blood remaining in each ventricle after systole
Dicrotic notch
Aortic pressure raises as backflow rebounds off closed valve cusps
Heart rate
Heart beats around 75 times per minute
Cardiac cycle duration
Lasts about 0.8 seconds
Atrial systole duration
Lasts about 0.1 seconds
Ventricular systole duration
Lasts about 0.3 seconds
Quiescent period
Total heart relaxation that lasts about 0.4 seconds
Normal systolic volume
120 mm Hg
Normal diastolic volume
80 mm Hg
Ventricular filling (passive)
When atrial pressure is greater than ventricular pressure, the AV valves are forced open, and blood flows passively into the atria and on through to the ventricles.
Ventricular filling with atrial contraction
The atria contract to complete the filling of the ventricles, achieving the end diastolic volume (EDV).
Isovolumetric contraction phase
The contraction of the ventricles begins, and ventricular pressure increases, closing the AV valves.
Ventricular ejection
Ventricular pressure continues to rise; when the pressure in the ventricles exceeds the pressure in the great vessels exiting the heart, the SL valves open, and blood is ejected.
Isovolumetric relaxation
The ventricles relax, decreasing the pressure in the ventricles; the decrease in pressure causes the SL valves to close. The dicrotic notch is the result of a pressure fluctuation that occurs when the aortic valve snaps shut.
Heart sounds
Two sounds (lub-dup) associated with closing of heart valves.
First heart sound
Closing of AV valves at beginning of ventricular systole.
Second heart sound
Closing of SL valves at beginning of ventricular diastole.
Pause between lub-dups
Indicates heart relaxation.
Mitral valve closure
Mitral valve closes slightly before tricuspid.
Aortic valve closure
Aortic closes slightly before pulmonary valve.
Heart murmurs
Abnormal heart sounds heard when blood hits obstructions.
Incompetent valve
Fails to close completely, allowing backflow of blood.
Stenotic valve
Fails to open completely, restricting blood flow through valve.
Cardiac output (CO)
Amount of blood pumped out by each ventricle in 1 minute.
Cardiac output formula
Equals heart rate (HR) times stroke volume (SV).
Stroke volume (SV)
Volume of blood pumped out by one ventricle with each beat.
Stroke volume formula
SV = EDV - ESV.
Normal adult cardiac output
CO = HR 75 beats/min x SV 70 ml/beat = 5.25 L/min.
Hypocalcemia
Depresses heart.
Hypercalcemia
Increases HR and contractility.
Hyperkalemia
Alters electrical activity, which can lead to heart block and cardiac arrest.
Hypokalemia
Results in feeble heartbeat; arrhythmias.
Tachycardia
Abnormally fast heart rate (>100 beats/min).
Bradycardia
Heart rate slower than 60 beats/min.
Coronary atherosclerosis
Clogged arteries caused by fat buildup; impairs oxygen delivery to cardiac cells.
Congestive heart failure (CHF)
A condition where persistent high blood pressure causes the myocardium to exert more force, leading to chronic increased ESV, hypertrophy, and weakness.
Multiple myocardial infarcts
A condition where the heart becomes weak as contractile cells are replaced with scar tissue.
Dilated cardiomyopathy (DCM)
A condition where ventricles stretch and become flabby, and myocardium deteriorates, potentially due to drug toxicity or chronic inflammation.
Left-sided heart failure
Results in pulmonary congestion where blood backs up in the lungs.
Right-sided heart failure
Results in peripheral congestion where blood pools in body organs, causing edema.
Decompensated heart failure
A condition where failure of either side of the heart ultimately weakens the other side, leading to a seriously weakened heart.
Pulse
The alternating surges of pressure in an artery that occur with each contraction and relaxation of the left ventricle, averaging 70-76 beats per minute in the resting state.
Superficial temporal artery
An artery located anterior to the ear, in the temple region.
Facial artery
An artery that runs in line with the corner of the mouth.
Common carotid artery
An artery located at the side of the neck.
Brachial artery
An artery located in the cubital fossa, where it bifurcates into the radial and ulnar arteries.
Radial artery
An artery located at the lateral aspect of the wrist, above the thumb.
Femoral artery
An artery located in the groin.
Popliteal artery
An artery located at the back of the knee.
Posterior tibial artery
An artery located just above the medial malleolus.
Dorsalis pedis artery
An artery located on the dorsum of the foot.
Systemic arterial blood pressure (BP)
Measured indirectly by auscultatory methods using a sphygmomanometer.
Systolic pressure
The pressure when sounds first occur as blood starts to spurt through the artery, normally less than 120 mm Hg.
Diastolic pressure
The pressure when sounds disappear because the artery is no longer constricted, normally less than 80 mm Hg.
Hypertension
Sustained elevated arterial pressure of 140/90 mm Hg or higher.
Prehypertension
A condition where values are elevated but not yet in the hypertension range, often transient during fever, physical exertion, and emotional upset.
Primary hypertension
Accounts for 90% of hypertensive conditions, with risk factors including heredity, diet, obesity, age, diabetes mellitus, stress, and smoking.
Secondary hypertension
Less common hypertension due to identifiable disorders including obstructed renal arteries, kidney disease, and endocrine disorders.
Hypotension
Low blood pressure below 90/60 mm Hg.
Orthostatic hypotension
Temporary low BP and dizziness when suddenly rising from a sitting or reclining position.
Chronic hypotension
A hint of poor nutrition and a warning sign for Addison's disease or hypothyroidism.
Acute hypotension
An important sign of circulatory shock.
Circulatory shock
A condition where blood vessels inadequately fill and cannot circulate blood normally, leading to inadequate blood flow that cannot meet tissue needs.
Hypovolemic shock
A type of shock that results from large-scale blood loss.
Vascular shock
A type of shock that results from extreme vasodilation and decreased peripheral resistance.
Cardiogenic shock
A type of shock that occurs when an inefficient heart cannot sustain adequate circulation.
