It is clear from thd literature that LV dysfunction is an independent determinant of the prognosis id patients with ischemic heart disease. Several parameters can be measured for Jsessment of LV systolic function.
1) M-Mode Echlocardiography
With the cursor- beam cutting the left ventricle just beyond the tips of mitral valve in an adequate parasternal long axis view, the M-Mode shows the left ventricular We wall and septa1 thickness in systole and diastole. The LV systolic and iastolic dimensions can be measured and following parameters can be calcul ted
Fractional Shbrtening (FS) = (LVED-LVES x 100)/LVED
LVED-Left ventricular end diastolic dimensions
LVES-Left ventricular end systolic dimensions
Normal value = 28-44 per cent
This describes the systolic function at base of the heart. In absence of regional wall motion abnormalities, this may reflect rest of the left ventricle. This is usually calculated automatically from online software using M-Mode ventricular dimensions in systolic and diastolic
Ejection Fraction = 2x fraction shortening provided there .are no RWMA.
2) Two Dimensional Echocardiography
I)Eye Balling
Two-dimensional echocardiography provides a good visual perception of cardiac functions. With experience, the echocardiologist learns to perceive and approximate the LV ejection fraction visually. This is called Eye Balling. Whenever this method is used, a value to the nearest 10 per cent or a range (e.g. 40-50 per cent) should be given since estimate can never be precise.
11) Modified Simpson s ' Method
This is the commonest method available for objective calculation of left ventricular volumes, which can be computed to obtain LV ejection fraction. In modified Simpson's method LV is traced in diastole and systole in apical 4 chamber and two chamber views. LV is cut along its long axis into 20 cross sections.
LV volume = 7c/4 (a1 x bl)x)(L/20)
diameter of LV in apical 4 L view
a1 =diameter of LV in apical 4 L view
1) M-Mode Echlocardiography
With the cursor- beam cutting the left ventricle just beyond the tips of mitral valve in an adequate parasternal long axis view, the M-Mode shows the left ventricular We wall and septa1 thickness in systole and diastole. The LV systolic and iastolic dimensions can be measured and following parameters can be calcul ted
Fractional Shbrtening (FS) = (LVED-LVES x 100)/LVED
LVED-Left ventricular end diastolic dimensions
LVES-Left ventricular end systolic dimensions
Normal value = 28-44 per cent
This describes the systolic function at base of the heart. In absence of regional wall motion abnormalities, this may reflect rest of the left ventricle. This is usually calculated automatically from online software using M-Mode ventricular dimensions in systolic and diastolic
Ejection Fraction = 2x fraction shortening provided there .are no RWMA.
2) Two Dimensional Echocardiography
I)Eye Balling
Two-dimensional echocardiography provides a good visual perception of cardiac functions. With experience, the echocardiologist learns to perceive and approximate the LV ejection fraction visually. This is called Eye Balling. Whenever this method is used, a value to the nearest 10 per cent or a range (e.g. 40-50 per cent) should be given since estimate can never be precise.
11) Modified Simpson s ' Method
This is the commonest method available for objective calculation of left ventricular volumes, which can be computed to obtain LV ejection fraction. In modified Simpson's method LV is traced in diastole and systole in apical 4 chamber and two chamber views. LV is cut along its long axis into 20 cross sections.
LV volume = 7c/4 (a1 x bl)x)(L/20)
diameter of LV in apical 4 L view
a1 =diameter of LV in apical 4 L view
b1 = diameter of LV in apical 2 L view
All present day echocardiography machines have built in software for calculation of LV volumes and ejection fraction by modified Simpson's method. The echocardiogram can be manually traced offline during diastole and systole and the machine automatically gives LV volumes and ejection fraction. For accuracy of above method the mandatory requirement is adequate endocardia1 visualization. This method is operator dependent and depends on operator's experience.
All present day echocardiography machines have built in software for calculation of LV volumes and ejection fraction by modified Simpson's method. The echocardiogram can be manually traced offline during diastole and systole and the machine automatically gives LV volumes and ejection fraction. For accuracy of above method the mandatory requirement is adequate endocardia1 visualization. This method is operator dependent and depends on operator's experience.
 |
| LV in diastole - LV in systole |
Two Dimensional ech~cardiographic image demonstrating calculation of LV volumes by modified simpson's method
Assessment of Diastdlic Function
Myocardial ischemia Clters diastolic function of left ventricle. The earliest abnormality to appear with prolonged ischemia is delayed myocardial relaxation i.e. A > E., increased deceleration time. Diastolic function after myocardial infarction (MI) depends upon the interaction of various factors:
Assessment of Diastdlic Function
Myocardial ischemia Clters diastolic function of left ventricle. The earliest abnormality to appear with prolonged ischemia is delayed myocardial relaxation i.e. A > E., increased deceleration time. Diastolic function after myocardial infarction (MI) depends upon the interaction of various factors:
- Ventricular compliance
- LA pressure
- Loading conditioos
- Heart rate
Medications
Patients with severe LV dysfunction after MI demonstrate restrictive filling pattern i.e. E >>> A and decreased deceleration time. Patients with restrictive transmitral filling pattlern most likely experience heart failure. Basics of diastolic dysfunction are explained in subsequent section.
Direct Visualisation o f Coronary Arteries
Coronary arteries cad be directly visualized using two-dimensional echocardiography, especially in patients with good window. The commonest artery to be seen is the left main, proximal LAD and LCx in the SAX view the level of aortic valve. RCA and LCx can be seen in the AV groove using apical window. The arteries are not visualized as a continuous channel, they are seen in small portions in diaerent phases of cardiac cycle. The visualization is better on Transesophageal echocardiography.Echocardiography in Ischaemic Heart Disease
Patients with severe LV dysfunction after MI demonstrate restrictive filling pattern i.e. E >>> A and decreased deceleration time. Patients with restrictive transmitral filling pattlern most likely experience heart failure. Basics of diastolic dysfunction are explained in subsequent section.
Direct Visualisation o f Coronary Arteries
Coronary arteries cad be directly visualized using two-dimensional echocardiography, especially in patients with good window. The commonest artery to be seen is the left main, proximal LAD and LCx in the SAX view the level of aortic valve. RCA and LCx can be seen in the AV groove using apical window. The arteries are not visualized as a continuous channel, they are seen in small portions in diaerent phases of cardiac cycle. The visualization is better on Transesophageal echocardiography.Echocardiography in Ischaemic Heart Disease
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