COLOUR DOPPLER ECHOCARDIOGRAPHY IN THE MANAGEMENT OF CONGENITAL HEART DISEASE

ABSTRACT

Twenty patients with various forms of congenital heart disease admitted to Army Hospital Delhi Cantt were studied. After detailed clinical examination and routine investigations they were subjected to two dimensional and subsequently colour Doppler echocardiography. Two patients were operated on the data obtained by echocardiographi. studies only. Seven patients required preoperative catheterisation in addition to echographic examination. The operative procedures confirmed the lesions delineated on colour Doppler echocardiography. Three patients are on echocardiographic review and remaining seven are awaiting surgery to further confirm the diagnosis offered on colour Doppler echo. One pateint of complex lesion died before detailed evaluation could be carried out. Thus colour Doppler echocardiography, though considered highly accurate and non invasive investigation for assessment of congenital heart disease is still in the stage of infancy in paediatric set up and requires a high degree of expertise before it can replace preoperative catheterisation in majority of cases.

Introduction

In the last decade, non invasive cardiovascular imaging and haemodynamic assessment have revolutionised the management of congenital heart disease (CHD) and have often rendered cardiac catheterisation unnecessary specially in cases of atrial septal defect [1,2]. Two dimension echocardiography (Echo) can be used to study congenital malformations, valvular structure and function, sub-valvular structures, ventricular function, ejection fraction, intracavity masses, pericardial disease and other structures [3]. Using two dimension colour coded Doppler flow imaging, both the time course and spatial blood flow in the heart can be rapidly visualised and co-related with cardiac structures. The colour modality acts as an angiogram in revealing the direction of flow, abnormal flow patterns and subjectively the volume of flow through shunts and regurgitant lesions. The blood flow information provided by colour flow imaging often outlines small defects that are not well seen with conventional Echo. The result is a non invasive colour angiogram of the two dimensional image of the cardiac anatomy with a colour representation of blood as it flows through the anatomy [4,5].

In colour flow imaging, direction is indicated by one of the two possible colour ranges of red or blue. Velocity of blood flow is represented by the colour intensity within this colour range. The higher the velocity of flow, the brighter is the colour display. The flows towards the transducer are shown as increasing brightness of red and flows away as increasing brightness of blue with colour proportional to the velocity [6,7]. In this manner, Doppler colour flow imaging clearly shows areas of normal flow, abnormal flow and turbulant jets [8].

Definitive diagnosis can be made before catheterisation in many conditions and in many other lesions catheterisation can be avoided altogether and patients can be operated upon purely on Echo data [9, 10, 11]. Present study was undertaken to evaluate the efficacy of colour Doppler Echo in the diagnosis and management of CHD.

Material and Methods

Twenty children with various types of CHD admitted to Army Hospital Delhi Cantt during the period from Apr 90 to Mar 91 were studied. The patients were clinically assessed and relevant laboratory investigations including electrocardiographic studies were carried out on them. Subsequently these patients were subjected to two dimension Echo, colour Doppler Echo and colour M mode studies at Central Medical Establishment (Air Force), Delhi Cantt.

Two dimensional Echo, Doppler, M-mode and colour Doppler studies were carried out on a WING MED CFM 700 colour Echo machine using a special specific paediatric Echo probe of 5 mega hertz frequency. Appropriate and relevant portions of these studies were recorded on a video cassette for subsequent evaluation and in certain cases on special recording paper for further reference.

Results

Twenty patients of various forms of CHD admitted for corrective or palliative surgery or in whom the disease had been recently detected were studied. Their age and sex distribution is given in Table 1. The types of CHD studied are depicted in Table 2. The subsequent investigations, mangement and outcome of these patients are shown in Table 3.

TABLE 1.

Age and sex distribution of patients

Age Group	Male	Female
1 – 3 years	6	4
4 – 6 years	2	2
7 – 9 years	3	1
10 – 12 years	1	1
Total	12	8

TABLE 2.

Various types of lesions studied

Lesion	No of patients
VSD	01
VSD with PS	02
VSD with pulmonary atresia	01
VSD with ASD	02
VSD with PDA	02
ASD	01
PDA	01
Coarctation of aorta	01
Aorto-pulmonary window	01
Tetralogy of Fallot	04
Transpostion of great arteries	01
Single ventricle	01
Complex lesions	02
Total	20

TABLE 3.

Management and outcome of patients

Number of patients operated	09
(a) Based on echo only	02
(b) On echo and cath findings	07
Number of patients on echo follow up	03
Number of patients awaiting surgery	07
Number of patients of complex lesion died before catheterisation	01
Total	20

Two of the patients, one with an atrial septal defect (ASD) and one with a patent ductus arteriosus (PDA) were operated upon without these patients undergoing cardiac catheterisation i.e., on the data solely based on Echo and colour doppler studies.

Discussion

Cardiac catheterisation and angiography are comparatively risky procedures and though the incidence of mortality and morbidity is low, certain complications are known to occur. Furthermore with the advent of colour Doppler Echo, the anatomical and haemodynamic data gathered are as good and in certain lesions considered better in comparison to cardiac catheterisation. During this study it was realised that one of the most important aspects in assessment was the experience and technical skill of the physician performing the Doppler studies and its interpretation.

In ASD, colour Doppler flow studies clearly demonstrated the flow patterns across the defect and whereever there were doubtful lesions, these were clarified by presence or absence of flow and mosaic pattern (presense of turbulance) across the atrial septum (Fig. 1).

Fig. 1.

Mosaic pattern of turbulant flow across an atrial septal defect seen as an admixture of yellow to red and blue colours originally.

In this study one patient with isolated ASD was successfully operated upon based solely on Echo findings, confirming the criteria of Kitakabe [12] that surgery in patients with ASD can be carried out without the necessity of cardiac catheterisation.

In two patients, the ASD was associated with ventricular septal defect (VSD) and in three others where it was associated as a part of complex lesion, the defect was well appreciated as to its type, size, hemodynamic consequences and direction of flow by colour flow imaging. Our findings were consistent with those of other workers [13,14].

In the patients with VSD, the presence or absence of the defect was easily delineated and the degree of flow across the defect could be subjectively graded easily by noting the type of colour flow across the defect. Measurement of flow and pressure could also be assessed easily. The same has been reflected in the work done by Sahn et al [15].

Among two of the three patients of PDA, the ductus could be directly visualised with two dimensional Echo and the magnitude of the shunt estimated using doppler and colour flow imaging. In the third patient although the ductus could not be visualised, the flow and shunting could be seen clearly (Fig. 2). Our findings are in agreement with those of Liao et al and Swensson et al [16,17].

Fig. 2.

Colour echocardiogram in M-mode. Graphic display of increased flow in the pulmonary artery (originally in blue colour).

In a patient with coarctation of aorta, the patient also had associated aortic stenosis and regurgitation. The coarctation was localised and its severity assessed with a combination of two dimension Echo and colour flow mapping. The flow and pressure measurements of the aortic valve lesions were also assessed by a combination of these two examinations on the lines described by Sahn et al [18].

In patients with Tetralogy of Fallot, after delineation of anatomy by two dimensional Echo and Doppler examination, colour flow imaging was used to screen for the presence of septal defects, the location of right ventricular obstruction, the size of the pulmonary artery and the right ventricular morphology as per the description given by Flanagan [18].

In patients with other complex cardiac lesions, colour Doppler Echo provided definitive diagnosis. This was in agreement with the findings of Alboliras et al [20]. In these cases, ultimately cardiac catheterisation and angiography had to be resorted to obtain the exact anatomical data, especially in patients who were to be taken for surgery.

In almost all of our cases the diagnosis given by colour Doppler Echo were confirmed either by cardiac catheterisation or surgery, thus proving the efficacy of this non invasive mode of investigation in CHD.