Variations in blood pressure Medical Assignment Help

The systolic blood pressure varies by up to 10 mmHg between the right and left brachial arteries. Standing usually causes a slight reduction of the systolic pressure «20 mmHg) and an increase in the diastolic blood pressure «10 mmHg). In postural (orthostatic) hypotension, a large postural fall of both the systolic and diastolic pressures is associated with dizziness. When anirregular heart rhythm such as atrial fibrillation is present, the blood pressure is variable. Because the blood pressure is normally liable to variation it must be estimated on several occasions before it can be declared elevated.

Taking the blood pressure.

Taking the blood pressure.

JUGULAR VENOUS PULSE (JVP)

There are no valves between the internal jugular vein and the right atrium and observation of the column of blood in the internal jugular system is therefore a good measure of right atrial pressure. The external jugular cannot be relied upon because of its valves and because it may be obstructed by the fascial and muscular layers through which it passes; it can only be used if typical venous pulsation is seen, indicating no obstruction to flow.
An abnormally low jugular venous pressure cannot be measured clinically. Causes include haemorrhage and other forms of hypovolaemia. Elevation of the jugular venous pressure occurs in heart failure. It is also produced by:
• Constrictive pericarditis
• Cardiac tamponade
• Renal disease with salt and water retention
• Overtransfusion or excessive infusion of fluids
• Superior vena caval obstruction (but in this case pulsation is absent)
In constrictive pericarditis or cardiac tamponade, ventricular filling is reduced during inspiration because the ventricles are squeezed by the pericardial fluid or noncompliant pericardium, which tightens as the diaphragm descends. Thus, the level of venous pressure increases during inspiration (Kussmaul’s sign). Other causes of an increased jugular pressure also distort the shape of the pressure wave and are considered below.

Measurement of the jugular pressure.

Measurement of the jugular pressure.

The jugular venous pressure wave

This consists of three peaks and two troughs.
The peaks are described as a, c and v waves and the troughs are known as x and y descents:
1 The a wave is produced by atrial systole.
2 The x descent occurs when the atrial contraction finishes.
3 As the pressure falls there is a small transient increase that produces a positive deflection called the c wave. This is caused by transmission of the rapidly increasing right ventricular pressure before the tricuspid valve closes.
4 The v wave develops as the venous return fills the right atrium during continued ventricular systole.
5 The y descent follows the v wave when the tricuspid valve opens.

The a wave can be distinguished from the v wave by observing the venous pulse while palpating the carotid artery. The a wave occurs immediately before carotid pulsation and the v wave occurs simultaneously with carotid pulsation.
The main abnormalities of the shape of the jugular venous pressure wave are elevations of the a and v waves and steepness of the y descent.

Large a waves

These are caused by increased resistance to ventricular filling, as seen with right ventricular hypertrophy due to pulmonary hypertension or pulmonary stenosis. They may also be caused by tricuspid stenosis, but this is unusual because patients with tricuspid stenosis are usually in atrial fibrillation and therefore do not have a waves.

Various jugular venous waveforms.

Various jugular venous waveforms.

A very large a wave occurs when the atrium contracts against a closed tricuspid valve. This is known as a ‘cannon wave’. Cannon waves occur irregularly in complete heart block and in ventricular tachycardia. In both these situations there is atrioventricular dissociation, and by random chance there is occasional simultaneous atrial and ventricular contraction. In junctional rhythms the atria and ventricles usually contract simultaneously and rapid, regular cannon waves are produced.

Large  waves

Tricuspid regurgitation results in giant v waves (systolic waves) because the right ventricular pressure is transmitted directly to the right atrium and the great veins.

Steep r descent

Diastolic collapse of elevated venous pressure can occur in right ventricular failure but is more dramatic in constrictive pericarditis and tricuspid regurgitation. At the end of ventricular systole the elevated atrial pressure suddenly falls when the tricuspid valve opens. However, the ventricles are stiff and cannot be distended. The venous pressure therefore rapidly rises again. This rapid fall and rise of the jugular venous pulse is known as Friedreich’s sign.

EXAMINATION OF THE PRECORDIUM

Inspection

Deformities should be looked for as they can mimic cardiac abnormalities. For example, pectus excavatum (funnel chest) or kyphoscoliosis may cause an ejection systolic murmur. The position of the apex beat and other cardiac pulsations should be noted; a left ventricular aneurysm may produce an eccentric and abnormal pulsation.

Palpation

The apex beat is defined as the most inferior and most lateral point of cardiac pulsation. It is usually felt just inside the mid-clavicular line at the level of the fourth or fifth left intercostal space. Cardiac enlargement, particularly left ventricular dilatation, displaces the apex beat to the left. The apex beat may also be displaced by a pneumothorax, pulmonary collapse or skeletal abnormalities such as scoliosis. The apex beat is normally just palpable and confined to a point that can be covered by one finger. There are several abnormal forms: TAPPING -a sudden but brief cardiac impulse felt in mitral stenosis.
T H R U S TING- vigorous but non-sustained pulsation typical of ‘volume overload’ due to mitral or aortic regurgitation.
HEAVING-vigorous and sustained pulsation due to ‘pressure overload’ as in aortic stenosis and systemic hypertension.
IMPALPABLE-OCCurS in emphysema, pleural effusion, obesity and pericardial effusion.
DOUBLE -two apical pulsations with each heart beat may be felt in hypertrophic cardiomyopathy. This may be due to a palpable atrial impulse. A double apex can also be due to accentuated outward movement in late systole in ventricular aneurysm.
A parasternal heave is elicited by pressing the outstretched hand flat against the sternum or against the costal cartilages just to the left of the sternum. It occurs because of right ventricular hypertrophy. An enlarged left atrium may also cause a parasternal heave. Left atrial pulsation can be distinguished from pulsation due to right ventricular hypertrophy because it occurs before the apex beat or carotid pulsation. Vigorous pulmonary artery pulsation may be appreciated by palpation in the second left interspace. This is usually due to pulmon ary hypertension. Thrills are palpable murmurs that are most easily appreciated with the flat or ulnar border of the hand rather than with the fingers. A thrill implies a definite abnormality. Systolic thrills in the aortic area are usually due to aortic stenosis, whereas at the apex a systolic thrill is due to mitral regurgitation. A diastolic thrill is usually caused by mitral stenosis; a diastolic thrill due to aortic regurgitation is uncommon. Heart sounds that are very loud may also be palpated. In systemic hypertension the aortic second sound may be felt, and in pulmonary hypertension the pulmonary component of the second sound may be felt. Occasionally a third or fourth heart sound may be palpated.

Percussion

Percussion is not usually undertaken, but it may allow the approximate position and size of the heart to be determined.

Auscultation

The sounds best heard with the bell or the diaphragm of the stethoscope. There are four areas where the heart sounds and valvular murmurs are best heard:
1 The aortic area is in the second intercostal space immediately to the right of the sternum. The aorta arches upwards and forwards from the aortic valve and the murmur of aortic stenosis is transmitted best to this area.
2 The pulmonary area is in the second interspace just to the left of the sternum. This is the closest point to the pulmonary valve, where the murmur of pulmonary stenosis and the pulmonary component of the second heart sound are loudest.
3 The tricuspid area is in the fourth interspace to the left of the sternum (left sternal edge). Not only is this close to the tricuspid valve but is also over the ventricles. Therefore, as well as the murmurs and sounds from the tricuspid valve, the murmurs of pulmonary and aortic regurgitation and third and fourth right ventricular sounds are heard well here.
4 The mitral area or apex is the point at which the apex beat is felt. The first heart sound and mitral murmurs are loudest here, and aortic regurgitation and third and fourth left ventricular sounds are often heard best at this point. The sequence of cardiac auscultation is summarized.

Use of the stethoscope.

Use of the stethoscope.

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