Cardiac Cycle: From 3 Different Sources
The sequence of events, lasting for less than a second, that make up each beat of the heart. A heartbeat has 3 phases. In diasystole, the heart relaxes. During atrial systole, the atria contract, and in ventricular systole, the ventricles contract. The sinoatrial node (the heart’s pacemaker) regulates the timing of the phases by sending electrical impulses to the atria and ventricles.
The various sequential movements of the heart that comprise the rhythmic relaxation and expansion of the heart muscles as ?rst the atria contract and force the blood into the ventricles (diastole), which then contract (systole) to pump the blood round the body. (See ELECTROCARDIOGRAM (ECG).)
Cardiac Disease
See HEART, DISEASES OF.
the sequence of events between one heartbeat and the next, normally occupying less than a second. The atria contract simultaneously and force blood into the relaxed ventricles. The ventricles then contract very strongly and pump blood out through the aorta and pulmonary artery. During ventricular contraction, the atria relax and fill up again with blood. See diastole; systole.
Absence of a palpable pulse, and thus of circula tion of blood around the body by the heart contraction. The cause may be asystole or ventricular fibrillation.... cardiac arrest
Relating to the heart... cardiac
The volume of blood pumped out per minute by the ventricles of the heart. It is one measure of the heart’s e?ciency. At rest, the heart of a healthy adult will pump between 2.5 and 4.5 litres of blood every minute. Exercise will raise this to as much as 30 litres a minute but, if this ?gure is low, it suggests that the heart muscle may be diseased or that the person has suffered severe blood loss.... cardiac output
Drugs whose main actions are to increase the force of myocardial contraction and reduce the conductivity of the nerve ?bres in the atrioventricular node of the heart. They are useful in treating supraventricular tachycardias (rapid heart rhythm) and some forms of heart failure. Glycosides are a traditional group of cardiac drugs, originally derived from the leaves of foxglove plants and used as digitalis. The active principle has long been synthesised and used as DIGOXIN. They are potentaially toxic and their use, especially during initial treatment, should be monitored. Side-effects include ANOREXIA, nausea, vomiting, diarrhoea and abdominal pain; drowsiness, confusion and DEPRESSION may occur. An abnormally slow heart rate may develop. The glycosides should be used with special care in the elderly who are sometimes particularly susceptible to their toxic effects.... cardiac glycosides
The procedure used to restart the action of the heart if it is suddenly arrested. In many cases the arrested heart can be made to start beating again by rhythmic compression of the chest wall. This is done by placing the patient on a hard surface – a table or the ?oor – and then placing the heel of the hand over the lower part of the sternum and compressing the chest wall ?rmly, but not too forcibly, at the rate of 60–80 times a minute. At the same time arti?cial respiration must be started by the mouth-tomouth method. (See APPENDIX 1: BASIC FIRST AID.) Open heart massage is sometimes undertaken if an arrest occurs during a chest operation – the heart being directly handled by the resuscitator.... cardiac massage
The muscle, unique to the heart, which comprises the walls of the atria and ventricles. It consists of long broadening cells (?bres) with special physiological characteristics which enable them to keep contracting and expanding inde?nitely.... cardiac muscle
Obsessional fear about the state of the heart. It tends to occur after a heart attack and may result in the patient’s experiencing the symptoms of another attack.... cardiac neurosis
Compression of the heart due to abnormal accumulation of ?uid within the ?brous covering of the heart (PERICARDIUM). The result is irregular rhythm and death if the ?uid is not removed.... cardiac tamponade
A series of key cellular chemical reactions starting and ending with oxaloacetic acid. Also called the citric acid or tricarboxylic acid cycle, it produces energy in the form of ADENOSINE TRIPHOSPHATE (ATP) and is the last stage in the biological oxidation of fats, proteins, and carbohydrates. Named after Sir Hans Krebs, a German biochemist working in England in 1900, who won the Nobel Prize for his discovery.... krebs cycle
1 The entire course of a person’s life – from infancy to old age. 2 The genetically prescribed course followed by all living organisms, including humans.... life cycle
Abnormal rhythm of the heartbeat. Most commonly seen after someone has had a myocardial infarction, but also present in some normal individuals – especially if they have taken a lot of co?ee or other stimulant – and in those with a congenital abnormality of the heart-muscle conducting system. The cause is interference in the generation or transmission of electrical impulses through the heart’s conducting system. Occasional isolated irregular beats (ectopic beats) do not necessarily mean that conduction is faulty. Arrhythmias can be classi?ed as tachycardias (more than 100 beats a minute) or bradycardias (slower than 60 beats a minute). Heartbeats may be regular or irregular. (See HEART, DISEASES OF.)... cardiac arrhythmia
A diagnostic procedure in which a tube is inserted into a blood vessel under local anaesthetic and threaded through to the chambers of the heart to monitor blood ?ow, blood pressure, blood chemistry and the output of the heart, and to take a sample of heart tissue. The technique is used to diagnose congenital heart disease and coronary artery disease. Another application is in the diagnosis and treatment of valvular disease in the heart.... cardiac catheterisation
Slowing the action of the heart... cardiac depressant
See HEART, ARTIFICIAL.... cardiac pump
Compression of the outside of the sternum and ribs, effectively emptying and filling the heart to push blood through arteries to supply oxygen to the body - particularly to the brain.... external cardiac compression
Breathing difficulty in which bronchospasm and wheezing are caused by accumulation of fluid in the lungs (pulmonary oedema). This is usually due to reduced pumping efficiency of the left side of the heart (see heart failure) and is not true asthma. Treatment is with diuretic drugs.... asthma, cardiac
One of a group of tests used to assess the function of the heart in people who experience chest pain, breathlessness, or palpitations during exercise. The test establishes whether the patient has coronary artery disease. An ECG machine records the patterns of the heart’s electrical activity while the heart is stressed. This is usually achieved by the patient exercising on a treadmill or cycling. Specific changes in the electrical pattern as exercise levels increase indicate angina. Cardiac stress testing may be used in conjunction with radionuclide scanning to identify damaged areas of heart muscle.... cardiac stress test
Dropsy of heart origin is distinguished from renal dropsy by an increase in oedema as the day proceeds. In the morning there may be no swelling but by the evening legs become swollen from the ankles upwards. Fluids stagnate in the tissues from inability of the heart to perform efficiently as a pump. The condition is a symptom of heart failure with increasing breathlessness which may lead to general dropsy.
Symptoms: worse after exercise, breathlessness, headache, general weakness, feeble pulse, pale face, skin cold, swollen tissues pit on pressure.
Treatment. Alternatives:– Teas. Black Cohosh, Broom tops, Buchu, Dandelion, Hawthorn, Parsley root. Tea. Formula. Equal parts: Broom tops, Motherwort, Yarrow. 2 teaspoons to each cup water brought to boil and simmered 5 minutes in covered vessel. 1 cup 3-4 times daily.
Tablets/capsules. Buchu, Dandelion, Hawthorn, Juniper, Motherwort.
Formula. Dandelion 2; Hawthorn 2; Stone root 1. Mix. Dose: Powders: 750mg (three 00 capsules or half a teaspoon). Liquid extracts: 1 teaspoon. Tinctures: 2 teaspoons. Thrice daily.
Practitioner. Lily of the Valley, BPC 1934: 5-20 drops, 2-3 times daily.
Squills, tincture: resembles Digitalis in action. Dose: 1-3 drops, as prescribed.
Tinctures. Dandelion 2; Lily of the Valley 2; Stone root 1; Cayenne (tincture) quarter. Mix. Dose: 1 to 2 teaspoons thrice daily.
Popular formula. Tincture Scilla 5.0; Tincture Crataegus 10.0; Tincture Valerian to make 30.0. 15 drops thrice daily. (German Extemporaneous Formulae)
Diet. High protein. See: DIET – HEART AND CIRCULATION. ... cardiac dropsy
A diagnostic test in which a fine, sterile catheter is introduced into the heart via a blood vessel. It is used to diagnose and assess the extent of congenital heart disease (see heart disease, congenital) and coronary artery disease, and to diagnose and treat some disorders of the heart valves (see valvuloplasty). During the procedure, the pressure within the heart’s chambers can be measured, samples of blood and tissue can be taken, and a radiopaque substance can be injected to allow the heart’s cavities to be X-rayed.... catheterization, cardiac
A medical term meaning disturbance of heart rhythm, sometimes used as an alternative to arrhythmia (see arrhythmia, cardiac).... dysrhythmia, cardiac
a form of education in resuscitation skills using a *resuscitation mannikin wired up to a heart rhythm simulator that can mimic all common cardiac arrest situations. Candidates may be expected to perform basic life support as well as advanced life support and display skills in airway maintenance and team leadership. This form of teaching and assessment is widely used in advanced life support courses.... cardiac arrest simulation
a designated team of doctors in a hospital who attend *cardiac arrests as they occur and administer protocol-driven treatment according to the latest guidelines. See also medical emergency team.... cardiac-arrest team
An abnormality of the rhythm or rate of the heartbeat. Arrhythmias, which are caused by a disturbance in the electrical impulses in the heart, can be divided into 2 main groups: tachycardias, in which the rate is faster than normal, and bradycardias, in which the rate is slower.
In sinus tachycardia, the rate is raised, the rhythm is regular, and the beat originates in the sinoatrial node (see pacemaker). Supraventricular tachycardia is faster and the rhythm is regular. It may be caused by an abnormal electrical pathway that allows an impulse to
circulate continuously in the heart and take over from the sinoatrial node. Rapid, irregular beats that originate in the ventricles are called ventricular tachycardia. In atrial flutter, the atria (see atrium) beat regularly and very rapidly, but not every impulse reaches the ventricles, which beat at a slower rate. Uncoordinated, fast beating of the atria is called atrial fibrillation and produces totally irregular ventricular beats. Ventricular fibrillation is a form of cardiac arrest in which the ventricles twitch very rapidly in a disorganized manner.
Sinus bradycardia is a slow, regular beat. In heart block, the conduction of electrical impulses through the heart muscle is partially or completely blocked, leading to a slow, irregular heartbeat. Periods of bradycardia may alternate with periods of tachycardia due to a fault in impulse generation (see sick sinus syndrome).
A common cause of arrhythmia is coronary artery disease, particularly after myocardial infarction. Some tachycardias are due to a congenital defect in the heart’s conducting system. Caffeine can cause tachycardia in some people. Amitriptyline and some other antidepressant drugs can cause serious arrhythmias if they are taken in high doses.
An arrhythmia may be felt as palpitations, but in some cases arrhythmias can cause fainting, dizziness, chest pain, and breathlessness, which may be the 1st symptoms.
Arrhythmias are diagnosed by an ECG. If they are intermittent, a continuous recording may need to be made using an ambulatory ECG.
Treatments for arrhythmias include antiarrhythmic drugs, which prevent or slow tachycardias.
With an arrhythmia that has developed suddenly, it may be possible to restore normal heart rhythm by using electric shock to the heart (see defibrillation).
Abnormal conduction pathways in the heart can be treated using radio frequency ablation during cardiac catheterization (see catheterization, cardiac).
In some cases, a pacemaker can be fitted to restore normal heartbeat by overriding the heart’s abnormal rhythm.... arrhythmia, cardiac
the volume of blood pumped from the heart’s left ventricle divided by body surface area, expressed as litres per minute per square metre (l/min/m2). It is determined by heart rate and stroke volume index (the volume of blood pumped by the heart with each beat), and provides a normal range (2.5–4.0 l/min/m2) regardless of the size of the patient.... cardiac index
reflex control of the heart rate. Sensory fibres in the walls of the heart are stimulated when the heart rate increases above normal. Impulses are sent to the cardiac centre in the brain, stimulating the vagus nerve and leading to slowing of the heart rate.... cardiac reflex
a programme of staged exercises and lifestyle classes designed for people recovering from a heart attack and run through the local hospital by dedicated health care professionals, who may include specialist nurses, occupational therapists, and physiotherapists.... cardiac rehabilitation
(CRT) a treatment for heart failure that involves ventricular pacing with multiple *leads. The aim is to restore coordinated ventricular contraction and hence improve cardiac function.... cardiac resynchronization therapy
see Krebs cycle.... citric acid cycle
(CCF, congestive heart failure) see heart failure.... congestive cardiac failure
the periodic sequence of events in sexually mature nonpregnant women by which an egg cell (ovum) is released from the ovary at four-weekly intervals until *menopause. The stages of the menstrual cycle are shown in the diagram. An ovum develops within a *Graafian follicle in the ovary. When mature, it bursts from the follicle and travels along the Fallopian tube to the uterus. A temporary endocrine gland – the corpus luteum – develops in the ruptured follicle and secretes the hormone *progesterone, which causes the lining of the uterus (endometrium) to become thicker and richly supplied with blood in preparation for pregnancy. If the ovum is not fertilized the cycle continues: the corpus luteum shrinks and the endometrium is shed at *menstruation. If fertilization does take place the fertilized ovum becomes attached to the endometrium and the corpus luteum continues to secrete progesterone, i.e. pregnancy begins.... menstrual cycle
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