Here is an essay on ‘Echocardiography’ for class 8, 9, 10, 11 and 12. Find paragraphs, long and short essays on ‘Echocardiography’ especially written for school and medical students.
Essay on Echocardiography
Essay # 1. Introduction to Echocardiography:
The use of ultrasound in the diagnosis of heart disease is called echocardiography. The ultrasound is so named because it is beyond the reach of human hearing. The sound waves when passed in an homogenous medium, travels in a straight line.
If, however, any object of different density (called acoustic impedance) seems to come on its way, the sound will reflect mostly and refract partly. These reflected sound waves, called echoes, during their onward and return passage, can be converted into electrical wave patterns which can be seen in the television screen and recorded in a graphic paper.
When the high frequency sound waves are travelling along tissues of two different types e.g. muscles and blood, an echo is generated; which returns to the transducer. The time taken for this echo to return is a measure of distance of the reflective structure from the transducer.
The basic circuit of the echocardiography instrument allows one transducer, which is responsible to transmit a known amount of ultrasound and then it acts as a receiver, for the returning echoes. When the returning echo takes the form of a spike it is called A-mode.
When these spikes were converted to a dot (brightness), it is called B-mode. One can then sweep the oscilloscope in order to introduce a time axis. It is useful in detecting echoes on a moving object, such as heart and hence called M (Motion)-Mode display. Initially M-Mode echocardiography was used for all diagnostic purposes.
However, with the advancement of technology in ultrasound two-dimensional echocardiography was introduced. The later further enhanced the diagnostic capability of the instrument. Finally, Doppler was added which bridged few loop holes in echocardiographic diagnosis.
The ultrasound equipment is a complex instrument. The transducer contains a piezo-electric crystal, which when stimulated electrically can vibrate at a very high frequency, producing a burst of ultrasound, which it transmits. During the receiving cycle, the same piezo-electric crystal responds to the reflected sound and vibrates which is converted back to electric signal and can thus be amplified and appropriately displayed and also recorded.
Essay # 2. Methods Involved in Echocardiography:
In echocardiography no special preparations of the patient are necessary. The patient lies in the comfortable bed with semi-inclined (30° inclination) position and turned towards the left. The operator sits comfortably by his side and puts a small transducer in the left precordium between 2nd and 4th left intercostal space near the sternal edge.
The transducer is directed perpendicularly on the chest wall. Initially the mitral valve is identified and then by turning the transducer either towards the apex or towards the base, the other cardiac structures are identified. One can scan to and fro, from base to apex frequently.
Usually 4 different views are taken as follows:
(1) At the level of apex
(2) At the level of mitral valve
(3) At the junction of left atrium and left ventricle containing the anterior leaflet of the mitral valve
(4) At the level of the aorta and left atrium.
With M-mode only ice pack view of the heart showing these 4 views can be seen. However, with two dimensional transducer, a larger area of the heart can be seen and by rotating the transducer long axis, short axis, apical, two chamber and four chamber views, subcostal views, suprasternal views are taken. This technique can document the whole of cardiac silhouette.
Essay # 3. Indications for Performing Echocardiography:
An echocardiography helps in identification of cardiac structures and any abnormality can be detected.
However, it is valuable in identifying following diseases:
Mitral stenosis, mitral valve prolapse, flails mitral valve, aortic stenosis and regurgitation.
Vegetations in any valves and pericardial effusion.
Left ventricular function, hypertrophic cardiomyopathy, restrictive cardiomyopathy and congestive cardiomyopathy.
Congenital Heart Diseases:
Atrial septal defect, co-arctation of aorta, pulmonary stenosis, and bicuspid aortic valve, Endocardial cushion defect, truncus arteriosus, tetralogy of fallot, tricuspid atresia, pulmonary atresia,
Ebstein’s anomaly, some forms of ventricular and septal defects, double outlet right ventricle and single ventricle etc.
Mitral Valve Disease:
Echo Characteristic of Normal Mitral Valve M-Mode:
In M-mode study, mitral valve looks like a ‘M’ and ‘W’ pattern. The anterior leaflet looks like capital ‘M’ and posterior leaflet looks like ‘W’. The leaflets have the following points which are to be remembered as it signifies important cardiac events.
Mitral valve opens widely during diastole- Its initial opening is labelled as D-E point, and then there is sudden closure, which is labelled as E-F slope, then there is a short period of diastasis during which time nothing is happening and finally there is atrial contraction which is manifested by a point and then the two leaflets meet at systole, labelled as C-D following that cycle repeats itself.
Historically, mitral stenosis was first diagnosed through echocardiography. In mitral stenosis the two leaflets of mitral valve are thickened and E-F slope is significantly reduced because the stenotic valve remains open during diastole. The posterior leaflet of the mitral valve is moving anteriorly, instead of being a virtual mirror image motion of the anterior leaflet.
The E-F slope can be measured and accordingly, semi quantitative assessment of degree of stenosis can be made. There are some exceptions to this rule. With two dimensional echocardiography, the characteristic “bowing” of the anterior leaflet, can be seen. The posterior leaflet either is immobile or moving anteriorly, the leaflets ends are thickened and there is little separation between the two leaflets seen on long axis view.
In the short axis view, irregular surface area of the reduced mitral valve can be seen and the actual surface area of mitral valve can be determined. Four chamber apical views also show characteristic doming of the mitral valve, with large left atrium and normal or smaller than normal sized left ventricle. The right ventricle comparatively appears more enlarged.
In mitral regurgitation however, if it is of rheumatic origin, one can still see the thickened mitral valve. E-F slope is still reduced and abnormal posterior leaflet motion is seen. Indirect evidence of severe left atrial enlargement and left ventricular enlargement can seen. In two dimensional studies one can sometimes document inadequate co-amputation of the mitral valve leaflets during systole. With added Doppler techniques, further information regarding severity of mitral regurgitation can be made.
A common clinical mimicar of mitral stenosis is left atrial myxoma. Left atrial myxoma has similarities with mitral stenosis. They both have reduced E-F slope but in left atrial myxoma there is definite a line of separation between the edge of tumour and the mitral valve leaflet.
Moreover, there are clouds of echoes behind the mitral valve must be shown through repeated scanning from aortic root to left ventricular apex. With two dimensional study, not only the left atrial myxoma can be seen, but also the right atrial myxoma can be seen too. It shows the characteristic to and fro movement of the tumour like a Ping Pong ball, moving in and out of the left atrium.
Mitral Valve Prolapse:
This is a common disease and with echocardiography increasing number of such cases is being diagnosed. Here, the normal echo pattern of mitral valve is seen during diastole but during systole, either the posterior leaflet is pouching downwards or the whole of both leaflets are pouching downwards (Hammocking).
Phonocardiogram can be taken at the same time, showing the click, occurring at the same time with mitral valve prolapse. Again one should be very careful in diagnosing this mitral valve prolapse, as it can be produced artificially through irregular positioning of transducer. The transducer must be in perpendicular to mitral valve and both anterior and posterior leaflets of the mitral valve must be shown and repeated scanning should be done.
Sometimes one can use amyl-nitrate to document this mitral valve prolapse. Again with two dimensional study mitral valve prolapse can be better demonstrated and it can be seen at long axis view where either the posterior leaflets are pouching towards the left atrium or both leaflets are pouching towards left atrium.
Mitral leaflets are sometimes thickened and in four chamber apical and two chamber apical views, the mitral valves in systole can be demonstrated occupying a position 2 mm below the line drawn from mitral annulus. However, one cannot fairly assess the amount of mitral regurgitation directly. The Doppler technique will help in these cases.
Besides mitral valve prolapse, non-rheumatic mitral regurgitation can occur in papillary muscle dysfunction, flail mitral valve, where echocardiography can also help. Mitral valve can be the seat of sub-acute bacterial endocarditis and vegetations can be seen over the mitral valves. It consists of dense fuzzy echoes over the anterior and posterior leaflets of the mitral valves, together or independently and being mobile it has a characteristic to and fro movement during systole and diastole.
Fluttering of the mitral valve is seen in aortic insufficiency.
The Aortic Valve Disease:
The aortic valve has 3 cusps, right coronary, left coronary and non-coronary cusps. In M-mode only two cusps are documented. In two-dimensional study all three cusps can be seen.
In M-mode, one can see two walls of the aortic root moving parallel to each other, showing up as two bright lines, as a box like configuration during systole. These boxes represent the opening of the leaflets, as initial separation, of two leaflets, and then it remains separated and finally closes forming a single line occupying the mid posterior during diastole. The anterior echo is formed by the right coronary cusps and the posterior echoes by the non-coronary cusps.
If aortic root is measured during systole, normally it is less than 35 mm. Dilatation of the aortic root seen in Marfan’s disease, aortic aneurysms. The leaflet-separation of the aortic valve can also be measured at its middle and if it is less than 1 cm. then aortic stenosis is likely. The aortic valve is thickened and can be documented as two or more layers during diastole.
Various measurements, related to determine the severity of aortic stenosis has been postulated. It correlates with gradients and surface area of the aortic valve in children but not in adults, due to thickening of the valves, calcification, rheumatic affection etc. However, with two-dimensional study one can further document bicuspid or unicuspid aortic valve with doming and to and fro movements of the domed stenotic valves during systole and diastole, characteristic of congenital aortic stenosis.
Though in bicuspid aortic valve, one can see the eccentrically placed aortic leaflets during diastole but the later can be artifactual. Hence, two dimensional studies must be done. Now with added Doppler technique, one can assess the flow velocity and give some idea about the severity of the stenosis.
When aortic regurgitation is associated with aortic stenosis, the echo features of aortic stenosis, will be seen, in addition fluttering of the mitral valve can be documented. It looks like fine tremor-like motion of anterior or sometimes both anterior and posterior leaflets of mitral valve.
In simple aortic regurgitations, the aortic valve may be normal. Sometimes only thickening of the aortic valve can be seen. Aortic root may be dilated. Indirect evidence of left ventricular volume overload will be seen and recently it was claimed that by measuring the systolic dimensions of left ventricle, one can determine, suitability of aortic valve replacement.
Left ventricular systolic dimension of 55 mm is the key figure, as above that figure usually causes increased mortality. With two dimensional study, one can see prolapse of the aortic valve leaflets and inadequate apposition of the two aortic valve leaflets during diastole. With added Doppler technique, further direction velocity of blood flow can be determined both during systole and diastole, thus enhancing the accuracy in the diagnosis (Aortic valve disorders).
Aortic valve vegetation can be detected fairly accurately both in M-mode and two dimensional studies. In M-mode one can document, fuzzy echoes attached to either leaflets of the aorta. In two dimensional views, one can see echo-refractile mass, mobile, attached to either anterior or posterior cusp of the aortic valve.
It has a characteristic to and fro motion which once seen cannot be forgotten sometimes, the vegetation mass could be detached, causing embolism to distant areas and that also could be documented through echocardiography study.