Cardiovascular System



Cardiovascular System
The circulatory system, also called the cardiovascular system or the vascular system, is an organ system that permits blood to circulate and transport nutrients (such as amino acids and electrolytes), oxygen, carbon dioxide, hormones, and blood cells to and from the cells in the body to provide nourishment and help in fighting diseases, stabilize temperature and pH, and maintain homeostasis. The study of the blood flow is called hemodynamics. The study of the properties of the blood flow is called hemorheology.
The circulatory system is often seen to comprise two separate systems: the cardiovascular system, which distributes blood, and the lymphatic system, which circulates lymph.[1] The passage of lymph for example takes much longer than that of blood.[2] Blood is a fluid consisting of plasma, red blood cells, white blood cells, and platelets that is circulated by the heart through the vertebrate vascular system, carrying oxygen and nutrients to and waste materials away from all body tissues. Lymph is essentially recycled excess blood plasma after it has been filtered from the interstitial fluid (between cells) and returned to the lymphatic system. The cardiovascular (from Latin words meaning "heart" and "vessel") system comprises the blood, heart, and blood vessels.[3] The lymph, lymph nodes, and lymph vessels form the lymphatic system, which returns filtered blood plasma from the interstitial fluid (between cells) as lymph.
While humans, as well as other vertebrates, have a closed cardiovascular system (meaning that the blood never leaves the network of arteries, veins and capillaries), some invertebrate groups have an open cardiovascular system. The lymphatic system, on the other hand, is an open system providing an accessory route for excess interstitial fluid to be returned to the blood.[4] The more primitive, diploblastic animal phyla lack circulatory systems.

Structure
The essential components of the human cardiovascular system are the heart, blood and blood vessels.[5] It includes the pulmonary circulation, a "loop" through the lungs where blood is oxygenated; and the systemic circulation, a "loop" through the rest of the body to provide oxygenated blood. The systemic circulation can also be seen to function in two parts–a macrocirculation and a microcirculation. An average adult contains five to six quarts (roughly 4.7 to 5.7 liters) of blood, accounting for approximately 7% of their total body weight.[6] Blood consists of plasma, red blood cells, white blood cells, and platelets. Also, the digestive system works with the circulatory system to provide the nutrients the system needs to keep the heart pumping.[7]
The cardiovascular systems of humans are closed, meaning that the blood never leaves the network of blood vessels. In contrast, oxygen and nutrients diffuse across the blood vessel layers and enter interstitial fluid, which carries oxygen and nutrients to the target cells, and carbon dioxide and wastes in the opposite direction. The other component of the circulatory system, the lymphatic system, is open.

Development

The development of the circulatory system starts with vasculogenesis in the embryo. The human arterial and venous systems develop from different areas in the embryo. The arterial system develops mainly from the aortic arches, six pairs of arches which develop on the upper part of the embryo. The venous system arises from three bilateral veins during weeks 4 – 8 of embryogenesis. Fetal circulation begins within the 8th week of development. Fetal circulation does not include the lungs, which are bypassed via the truncus arteriosus. Before birth the fetus obtains oxygen (and nutrients) from the mother through the placenta and the umbilical cord.[11]

Arterial development

The human arterial system originates from the aortic arches and from the dorsal aortae starting from week 4 of embryonic life. The first and second aortic arches regress and forms only the maxillary arteries and stapedial arteries respectively. The arterial system itself arises from aortic arches 3, 4 and 6 (aortic arch 5 completely regresses).
The dorsal aortae, present on the dorsal side of the embryo, are initially present on both sides of the embryo. They later fuse to form the basis for the aorta itself. Approximately thirty smaller arteries branch from this at the back and sides. These branches form the intercostal arteries, arteries of the arms and legs, lumbar arteries and the lateral sacral arteries. Branches to the sides of the aorta will form the definitive renal, suprarenal and gonadal arteries. Finally, branches at the front of the aorta consist of the vitelline arteries and umbilical arteries. The vitelline arteries form the celiac, superior and inferior mesenteric arteries of the gastrointestinal tract. After birth, the umbilical arteries will form the internal iliac arteries.

Venous development

The human venous system develops mainly from the vitelline veins, the umbilical veins and the cardinal veins, all of which empty into the sinus venosus.
Cardiovascular History and Examination
A careful and detailed clinical assessment is essential in order to assess the likely cause and severity of symptoms, arrange appropriate investigations and referral, avoid unnecessary investigations and to assess individual risk of cardiovascular disease or cardiomyopathy.

History

The most common and most important cardiac symptoms and history are:
  • Chest pain, tightness or discomfort.
  • Shortness of breath.
  • Palpitations.
  • Syncope ('blackouts', 'faints', 'collapse') or dizziness.
  • Related cardiovascular history, including transient ischaemic attacks, stroke, peripheral arterial disease and peripheral oedema.

Chest pain

  • Chest pain is very important as a symptom of heart disease but is sometimes difficult to evaluate.
  • Location: usually in the front of the chest (retrosternal) but can also be in the upper abdomen, neck, jaw, left arm or left shoulder.
  • Radiation: may spread to the neck, jaw, back and left or right arm.
  • Nature: chest pain due to cardiac ischaemia is typically tight and crushing in quality:
    • Patients tend to describe the angina pains with the flat of their hand horizontally across the middle of their chest; they tend to describe oesophageal spasms with a clenched fist at the upper xiphisternum edge, moving in a vertical manner.
    • Patients may refer to anginal pain as indigestion.
  • Other features include duration, aggravating and relieving factors and associated symptoms - eg, nausea and/or vomiting, sweating, dizziness and palpitations.

Breathlessness

See also separate Breathlessness article.
  • Cardiac causes include severe pulmonary oedema, acute myocardial infarction, cardiac arrhythmia, pericarditis and pericardial effusion.
  • Dyspnoea on exertion is the most common type of dyspnoea and may precede other evidence of heart failure.
  • Orthopnoea: ask whether the patient has to sleep propped up at night and if so with how may pillows.
  • Establish whether there is any paroxysmal nocturnal dyspnoea or breathlessness at rest. These may last from minutes to hours and be accompanied by wheezing, sweating, distress and cough with frothy or bloodstained sputum. This is commonly termed 'cardiac asthma', although uraemia may cause similar symptoms.
  • Cheyne-Stokes or periodic breathing: this often occurs during sleep, with a long cycle time; it may be found in chronic pulmonary oedema or poor cardiac output.

Palpitations

See also separate Palpitations article.
  • Palpitations do not necessarily indicate any underlying cardiac pathology but may be presentation of a cardiac arrhythmia.
  • Description may be bumping, throbbing, or thumping.
  • Rhythm: ask the patient to tap out the rate and regularity; a missed beat or an extra large bump suggests extrasystoles.
  • Duration: sudden short episodes suggest paroxysmal tachycardia; longer duration with irregularities suggests atrial dysrhythmia.
  • Associated symptoms: pain, dyspnoea, feeling faint or syncope.

Other history to explore

  • Drugs/medication: prescribed, over-the-counter, or illegal drug abuse.
  • Associated cough:
    • Duration, paroxysms or constant, dry or productive?
    • Associations: is it related to chest pains; any fever or shivering fits?
    • Sputum: colour, quantity and any haemoptysis?
  • Limb ischaemia, intermittent claudication.
  • Gastrointestinal symptoms: chronic heart failure may cause abdominal discomfort due to liver enlargement and abdominal distension.
  • May present with failure to thrive in children or weight loss in adults (although fluid retention caused by heart failure will cause an increase in body weight).
  • Urinary symptoms: oliguria can be an important symptom of heart failure.
  • Cerebral symptoms:
    • Syncope of cardiac origin may closely resemble benign vasovagal attacks and can be caused by aortic stenosis or regurgitation (or even pulmonary stenosis), or excessively fast or slow ventricular rate (heart block, atrial dysrhythmia, paroxysmal tachycardia).
    • Dizziness, headache, and mental changes are not uncommon symptoms of severe hypertension, arterial degeneration and cardiac failure.

Past medical history

  • Enquire about any raised blood pressure, heart problems, fainting fits, dizziness or collapses.
  • Note whether there have been any heart attacks, any history of angina and any cardiac procedures or operations (type and date of intervention and outcome).
  • Previous levels of lipids if ever checked or known.
  • Ask whether there is any history of rheumatic fever or heart problems as a child.
  • General: note any other operations or illnesses, especially history of myocardial infarction, hyperlipidaemia, hypertension, stroke, diabetes.

Family history

Ask about hypertension, coronary heart disease, stroke, diabetes, hyperlipidaemia, congenital heart disease and any early deaths (before the age of 60) in the family.

Lifestyle

  • Include ensuring appropriate primary prevention of cardiovascular disease (including calculation of cardiovascular risk) and secondary prevention of cardiovascular disease.
  • Smoking.
  • Obesity: calculate body mass index (BMI); acute weight increase may indicate fluid retention and heart failure.
  • Diet: healthy or unhealthy.
  • Physical activity or inactivity, including exercise tolerance: ask whether there is anything that they cannot do because of any of the symptoms. It is best to try to quantify this - for example, inability to walk 50 yards rather than inability to walk. Note what changes they have had to make. For example, ask whether the patient stopped walking up the stairs or stopped work because of angina and/or breathlessness.
  • Occupation: establish whether this is sedentary or active and, if the latter, how active.
  • Stress levels - occupational and others.

Examination

General

  • Build (obesity or wasting); shortness of breath; difficulty in talking; note whether they look ill.
  • Look for pallor, jaundice, sweatiness and clamminess, and for xanthelasma around the eyes.
  • Look for any evidence of syndromes or non-cardiovascular conditions associated with cardiovascular abnormalities - eg, Down's syndrome, Marfan's syndrome, Turner syndrome, ankylosing spondylitis.

Cyanosis

  • This is seen below the fingernails and toenails but also in the lips, cheeks, ears and nose.
  • It may increase in the cold and on exertion.
  • Cyanosis may be a very late sign in an anaemic patient, due to their low haemoglobin (because cyanosis depends on a finite amount of deoxygenated haemoglobin not the ratio of deoxygenated haemoglobin).
  • In patients with dark skin, cyanosis is best seen on the inner lining of the eyelids or the inner surface of the lips.

Face

  • Malar flush - redness around the cheeks (mitral stenosis).
  • Xanthomata - yellowish deposits of lipid around the eyes, palms, or tendons (hyperlipidaemia).
  • Corneal arcus - a ring around the cornea (normal ageing or hyperlipidaemia).
  • Proptosis - forward projection or displacement of the eyeball (Graves' disease).

Hands

  • Finger clubbing.
  • Splinter haemorrhages (infective endocarditis).
  • Janeway lesions - macules on the back of the hands (infective endocarditis).
  • Osler's nodes - tender nodules in the fingertips (infective endocarditis).
  • Sweaty palms, tremor (thyrotoxicosis).
  • Lax joints (Marfan's syndrome).
  • Visible capillary pulsations in the nail bed (Quincke's sign - often seen in aortic regurgitation but can occur in normal individuals if the skin is warm, and in hyperthyroidism; can also be seen by pressing a glass slide on an everted lip).

Pulse

See also separate Pulse Examination article.
  • Rate: average 72/minute in adults, faster in children and may slow in old age. Also slower in athletes. Compare with apex rate.
  • Rhythm:
    • Respiratory variations are common in healthy individuals (if there is noticeable quickening in inspiration and slowing in expiration, this is termed sinus arrhythmia).
    • The most common irregularities are atrial arrhythmias and extrasystoles (which may disappear on exertion).
  • Character:
    • Thready, strong, bounding, collapsing ('water hammer' and its 2-stroke, dicrotic/hyperdicrotic variant) or slow-rising (plateau) or anacrotic (variant of slow-rising, with an extra wave on the upstroke).
    • A pulse that weakens in inspiration is called 'pulsus paradoxus' (as opposed to the normal increase in volume) and is found in constrictive pericarditis, pericardial effusion, restrictive cardiomyopathy and severe asthma.
    • 'Pulsus alternans' (an alternate variation in size of pulse wave) is an important sign of left ventricular failure but may be normal in the presence of a fast ventricular rate.
    • 'Pulsus bigeminus': groups of two heartbeats close together followed by a longer pause. The second pulse is weaker than the first. Pulsus bigeminus is caused by premature ventricular contractions after every other beat. It can be a sign of heart disease, particularly hypertrophic obstructive cardiomyopathy, or may be an innocent and temporary phenomenon.
  • Inequality of pulses:
    • Radials: congenital abnormality, aortic arch aneurysm, a few cases of coarctation of the aorta, supravalvular aortic stenosis (rare), Takayasu's disease and occlusion of the subclavian artery by external pressure.
    • Lower limb arteries: atherosclerosis of the larger arteries is the most common cause. Arterial embolism is an important cause in both the upper and lower limbs.
    • Dissecting aortic aneurysm may cause progressive occlusion, and even reappearance if re-entry occurs.
    • Arteritis and other inflammatory diseases occasionally cause occlusion.
  • Peripheral pulses:
    • Femoral pulses (radial femoral delay in coarctation) and foot and ankle pulses.
    • Listen over the renal and femoral artery for murmurs.

Check blood pressure

  • This should be measured in the brachial artery, using a cuff around the upper arm.
  • A large cuff must be used in obese people, because a small cuff will result in the blood pressure being overestimated.
  • Systolic pressure is at the level when first heard (Korotkoff I) and the diastolic pressure is when silence begins (Korotkoff V).
  • In patients with chest pain, or if ever the radial pulses appear asymmetrical, the pressure should be measured in both arms because a difference between the two may indicate aortic dissection.

Chest examination

  • Check the level of the jugular venous pressure.
  • Chest examination:
    • Look to see if the chest wall is deformed (eg, funnel chest) and moves equally (inequality of expansion is usually due to respiratory disease).
    • Note the respiratory rate; it is related to the pulse rate in the ratio of about 1:4 and remains constant in the same individual.
    • Ask the patient to breathe out and, using both hands resting lightly on the side walls of the chest with thumbs meeting in the middle, ask them to breathe in to assess the expansion of the chest on full inspiration by noting how far the examiner's thumbs move apart.
    • Observe and palpate the trachea to detect any deviation to the left or right (noting any thyroid swelling); otherwise, a false impression may be given of cardiac enlargement if the apex beat is displaced towards the axilla.
    • Palpate and percuss to find any areas of dullness (fluid or lung collapse); palpate with the flat hand over the 5th intercostal space to feel the maximum impulse (apex of the heart) and note its position; the apex is better defined by the light use of two fingers (noting the rib space and its position relative to an imaginary line dropped from the middle of the clavicle).
    • Feel over the anterior chest wall for any thrills associated with cardiac murmurs.
  • Auscultation of the heart - see separate Heart Auscultation and Heart Murmurs in Children articles.

Examination of other areas

  • Abdomen - see also separate Abdominal Examination article:
    • Palpate the abdomen for hepatomegaly and splenomegaly (congestive cardiac failure), or spleen alone (infective endocarditis).
    • Feel for enlargement of the aorta (aneurysm); feel with the hands flat either side of the aorta - feel for pulsation and tenderness.
  • Peripheral oedema:
    • Assess ankle swelling by pressing the thumb firmly (not hard) above the medial malleolus and see if it leaves an impression.
    • In a bed-bound patient the swelling is likely to be in the sacral area, genitalia and back of the thighs, rather than the ankles.
    • Oedema may also cause pleural effusion, pericardial effusion or ascites.
  • Fundoscopy:
    • Look for the silver wiring effect in hypertension, swollen disc in malignant hypertension, microaneurysms and fluffy deposits.
    • Also, look for Roth's spots in infective endocarditis.

Investigations

  • These may include:
    • Blood tests (for fasting glucose and/or glycosylated haemoglobin, renal function, LFTs, TFTs, lipid profile, cardiac enzymes, ESR or CRP).
    • 12-lead ECG and ambulatory ECG monitoring, exercise ECG testing.
    • Ambulatory blood pressure monitoring.
    • CXR.
    • Spirometry.
    • Echocardiogram.
    • Cardiac catheterisation.
    • Angiography.
  • NB: computer-assisted auscultation uses a digital stethoscope combined with acoustic neural networking to provide a visual display of heart sounds and murmurs and analyses the recordings to distinguish between innocent and pathological murmurs. This may be used more in the future.
Reference links






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