The following points highlight the defects caused due to acyanotic congenital heart disease that is found in humans. The defects are: 1. Ventricular Septal Defect 2. Atrial Septal Defect 3. Patent Ductus Arteriosus 4. Aortico-Pulmonary Septal Defect 5. Ruptured Sinus of Valsalva 6. Fistula of a Coronary Artery.
1. Ventricular Septal Defect:
Defect in the ventricular septa may present as an isolated phenomenon or isolated malformation or it may be associated with a variety of other congenital disorders, e.g. Tetralogy of Fallot, endomyocardial cushion defect, tricuspid atresia, etc.
According to the situation of ventricular septal defect, it can be classified into 1) Perimembranous, type when membranous portion of the septum is defective; 2) Supracristal type, when the defect is situated in the outflow tract of the right ventricle; 3) Muscular type, when central or muscular part of inter-ventricular septum was involved; 4) Ventricular septal defect of the common atrio-ventricular canal type, when it is part of the complete endocardial cushion defect.
Hemodynamics:
Blood from the left ventricle is shunted into the right ventricle and is then thrown into the pulmonary circulation, which is engorged and then returned to the left artium and left ventricle which is again shunted back to the right ventricle. Hence, there is significant enlargement of the left atrium, left ventricle and right ventricle.
The pulmonary arteries are dilated in this condition. As time progresses, there is increasing resistance in the pulmonary circulation causing pulmonary hypertension and as a result of which, the shunt becomes less and less and finally there may be reversal of the shunt from right to left, the condition called Eisenmenger’s Syndrome.
Clinical manifestations are largely depending upon the size of the defect and the reaction of the pulmonary circulation. If the defect is very small, the majority of the children are asymptomatic. Where the defect is large, it may present with heart failure even at a very early stage of their life. Shortness of breath is a common symptom. Fatiguability and failure to thrive are the two symptoms for which the child presents to the pediatrician.
General condition is usually satisfactory except that they probably have increased respiration rate than average and there is a systolic thrill best heard at the second and third intercostal spaces. Pansystolic murmur heard loudest at the left lower sternal area. Second sound is normal. It is moderately split with increase in the pulmonary blood flow; there may be an ejection type systolic murmur at the left upper sternal area. There may be a rumbling mid-diastolic murmur heard best at the apex due to increase flow across the mitral valve.
X-Ray:
In the early stage heart size may be absolutely normal with moderate degree of shunt, there may be cardiomegaly, increased pulmonary vascular congestion and left atrial enlargement or combined ventricular hypertrophy.
Most cases can be diagnosed correctly with an echocardiography, particularly the two dimensional views which determine the site of the defect and the extent of the defect and with added Doppler tracings, the actual flow velocity and calculation therefore of the shunt is possible.
The two-dimensional echocardiography, particularly the four chamber apical view, would detect the presence of any membranous type of ventricular septal defect, below aortic valve. The muscular defects are not very easy to diagnose, particularly if they are multiple, however, with some degree of reservations, it is possible to detect the large muscular type of ventricular septal defect.
Angiogram:
Angiogram does show the actual shunting of the dye from the left ventricle to the right ventricle/Pressure studies would also indicate increase in the pressure and oxygen saturation in the right ventricle as well as pulmonary arteries.
The natural history of the ventricular septal defect indicates that a large majority of small defects are closed spontaneously. Unless the defect is large, all patients should have periodic checkup through echocardiography examination. In addition, complications e.g. infected endocarditis, recurrent pneumonia; congestive heart failure and pulmonary hypertension need regular watch.
Treatment:
Treatment is usually surgical and includes if it is isolated phenomenon, closure of the ventricular septal defect. It is associated with other congenital malformations; the surgical treatment would be directed accordingly to the presence of those defects. Once the right to left shunt is established, surgical treatment is naturally contraindicated. Sometimes the repair of the ventricular septal defect is done in two stages, initially by pulmonary artery banding in the early infancy and later by proper closure of the ventricular septal defect. This again depends upon the different surgeons and different centres.
2. Atrial Septal Defect:
In intrauterine life, the foramen ovale is the normal channel of communication as there is no pulmonary circulation for oxygenation of blood.
Foramen ovale normally closes after birth but some cases the communication persists, which is called atrial septal defect (A.S.D.). A.S.D. according to its site can be classified into the following types:
(1) Fossa ovalis type, where the persistance of the defect at the fossa ovalis level.
(2) The atrial septal defect of the secondum in which the defect is near the region of fossa ovalis. Sometimes the defect could be multiple small openings, and sometimes usually there is one single large opening seen.
(3) The third type is sinus venosus defect, which is situated near the opening of the superior vena cava and is usually associated with partial anomalous pulmonary venous return.
(4) The fourth type is the septum primum defect, which is a part of the endocardial cushion defect in which the atrial septum defect is associated with a cleft mitral valve, with or without abnormal tricuspid valve. The defect in the atrial septum is at lower portion of the atrial septum adjacent to the atrio-ventricular valves.
Hemodynamics:
Here the blood from the left atrium is shunted to the right atrium, which also accommodates the usual venous return. Hence larger volume of blood flows into the right ventricle and into the lungs. Lungs are congested and returned the blood to the left atrium and then again shunted quickly into the right atrium. As a result the pulmonary vascular resistance increases with increased pulmonary arterial pressure and subsequently right ventricular pressure, leading to pulmonary hypertension. Sometimes the shunt may be reversed causing central cyanosis (Eisenmenger Syndrome).
Clinical manifestations are alike in all these four types of the condition and the large majority of the children are asymptomatic, though some amount of exertional intolerance has been common.
Recurrent attacks of chest infection and pneumonitis is also common.
Physical Signs:
The pulse is usually normal. Venous pressure is normal. The heart is usually enlarged, with right ventricular preponderance. There is a systolic murmur which is of ejection type and is usually best heard at the pulmonary area and is produced by the torrential flow in the pulmonary artery. There may be an ejection sound following the loud first sound present due to the same reasons.
The second sound however, is split widely and is fixed, that means it does not vary during inspiration and expiration. These auscultatory findings are really very characteristic of this condition. Sometimes a mid-diastolic murmur can be heard due to the torrential flow across the tricuspid valve and could be heard at the apex.
Electrocardiogram:
Electrocardiogram shows evidence of right ventricular diastolic volume overload, and they consist of right axis deviation, right ventricular hypertrophy with rsR’ pattern in E.C.G. There may be tall P waves or sometimes normal P waves, PR interval may be prolonged. These may be associated other cardiac arrhythmias like atrial fibrillation and heart block and occasionally Wolff Parkinson White Syndrome.
The echocardiographic examination is very characteristic and in the large majority of the patients a diagnosis can be reached with echocardiography. Cardiac catheterization is usually not required, unless other associated congenital lesions are suspected.
Echocardiographic:
The echocardiographic findings consisting of right ventricular volume overload, paradoxical inter-ventricular septal motion, relatively smaller sized left ventricle and normal left atrial size. In two dimensional echocardiography examination the actual site of the defect can be established.
Cardiac Catheterization:
Cardiac catheterization will indicate increased oxygenation at the level of the right atrium. Right atrial, right ventricular, pulmonary arterial pressure elevation will be noted. Angiogram will also show the shunting of the dye at the level of the atrium.
Complications:
Cardiac arrhythmias are not uncommon in this condition. Atrial fibrillation is the commonest cardiac arrhythmias seen, though Wolff Parkinson White Syndrome and heart block have been reported.
Treatment:
In the Western World all patients with atrial septal defect, whether they are asymptomatic or symptomatic, undergo surgical repair operation because the mortality rate is almost nil.
Endocardial Cushion Defect:
(Common atrio-ventricular canal and osteum primum defect)
In this condition, lack of fusion of embryonic endocardial cushions tissue leads to a variety of anatomic defects involving atrio-ventricular valves and the cardiac septum.
Clinical Manifestations:
Symptomatology is the same as in atrial septal defect. Physical findings are however diverse because of the associated presence of mitral incompetence from cleft mitral leaflet.
In this condition, as expected, the left ventricle is also enlarged along with left atrial enlargement, which is not present in atrial septal defect of the secundum type.
Radiology:
Radiology confirms cardiac enlargement of both the ventricles and right atrium. Pulmonary arteries are also large, and the pulmonary vascularity is increased.
Electrocardiogram:
Electrocardiogram is highly characteristic. This shows left axis deviation, counterclockwise inscription of the superiorly orientated QRS vector loop, biventricular hypertrophy, prolonged PR interval and tall P waves.
Echocardiographic:
Echocardiographic examination shows the presence of atrial septal defect along with right ventricular volume overload, left ventricular enlargement, left atrial enlargement and defective anterior leaflet of mitral valve.
Treatment:
Treatment is corrective surgery with artificial heart lung machine and closure of the defect as well as the cleft of the mitral valve is repaired.
Endocardial cushion defect in its complete form consists of a large central defect involving the lower portion of the atrial septum and upper portion of the ventricular septum. Instead of separate mitral and tricuspid valves, the large common anterior leaflet bridges the atrio-ventricular canal defect. The morphology and the attachment of this common anterior leaflet form the basis of the Rastelli’s classification.
Hemodynamics:
There is a significant shunt from the left to the right both at atrial and as well as the ventricular level. Pulmonary congestion is increased resulting in earlier appearance of pulmonary hypertension.
This condition is usually symptomatic. The majority of the children show fatiguability, recurrent pulmonary congestion and infection, and shortness of breath. Some with obvious heart failure.
J.V.P. is increased; cardiac enlargement is moderate to massive. Systolic thrill is frequently palpable at the third intercostal space due to ventricular septal defect. First sound is normal. There is a harsh systolic murmur heard best at the third intercostal space. Second sound is widely split with increased pulmonary valve closure sound. Low frequency mid-diastolic murmur is also heard at the left parasternal edge.
X-Ray:
X-ray shows significant cardiac enlargement with both ventricular enlargement, right atrial enlargement as well as severe pulmonary congestion. Selective right ventricular angiography is extremely helpful in diagnosis of endocardial cushion defects, deformity of the mitral or the common atrio-ventricular valve and the distortion of the outflow tract of the left ventricle, the so-called goose neck deformity can be well demonstrated in the large majority of the patients. They have cleft leaflet of the mitral valve and mitral incompetence also is demonstrated easily in the cin angiography.
Prognosis of this case depending upon the magnitude of the shunt and the degree of pulmonary vascular resistance and usually it involves surgery of an extensive nature and the mortality is higher than simple repair of the atrial septal defect. Pulmonary arterial banding car be done in the earlier stages and at later phase, complete correction of this defect is possible.
According to Rastelli classification there are three types. Rastelli type A is the most common type, where there is a septal defect with cleft in the mitral or tricuspid valves but anchoring of either mitral or tricuspid or both to the crest of the ventricular septum on the ipsi-lateral side.
Rastelli type B where the chordal attachments from medial portions of the cleft mitral valve is related to the papillary muscle on the right side of the septum crossing the ventricular septal defect, requiring mitral valve replacement operation.
Rastelli type C in which it is a floater, free floater anterior leaflet without having any attachment to the chords. This condition is not amendable to surgery. The leaflets are anchored to the right or left ventricle respectively.
3. Patent Ductus Arteriosus:
During foetal life the ductus arteriosus conveys blood from pulmonary artery into the aorta and it closes soon after birth as soon as pulmonary circuit is opened up. If the ductus remains patent, the blood from the high pressure areas, aortic blood is shunted into the pulmonary artery. This is a common congenital cardiac defect, which may occur as an isolated anomaly or it could be associated with other congenital disorders.
Hemodynamics:
Here the blood flows from the aorta into the pulmonary artery and hence the left ventricular output is reduced depending upon the magnitude of the shunt. Consequently the pulmonary blood flow is increased.
Clinical Manifestation:
Majority of the children having patent ductus arteriosus are symptomless. However if the ductus is large, the shunt is significant, so the patients develop signs and symptoms of left ventricular failure namely, shortness of breath during exertion, paroxysmal nocturnal dyspnoea, and finally left heart failure with pulmonary oedema. Retardation of the growth could occur as well.
Physical Signs:
Pulse is of the water hammer characteristic, the low diastolic pressure with increased pulse pressure is noted, jugular venous pressures is not increased, apical pulse is of the left ventricular type with some cardiac enlargement, a thrill may be present in the left second intercostal space.
Classically the murmur has been described as machinery, humming top, rolling thunder in quality. It characteristically begins soon after the first sound reaches its maximum intensity at the end of the systole and wanes in late diastole. Second heart sound, when heard, may be normal splitting with A2 and P2 being equal.
Electrocardiogram:
The electrocardiogram may be normal or show left ventricular hypertrophy depending on the left ventricular volume overload.
X-Ray:
X-ray chest shows significant pulmonary vascular markings with dominant pulmonary arteries. Cardiac size is usually enlarged with left ventricular preponderance. The left atrium is also enlarged. The aortic knob is usually normal, or sometimes prominent.
Echocardiographic:
Echocardiographic examination is also characteristic and it shows the presence of left atrial enlargement, left ventricular enlargement and the ductus can be demonstrated in the large majority of the cases by means of two dimensional echo studies. Recent Doppler technique not only confirms the diagnosis but measures the flow calculating the amount of shunt.
Cardiac Catheterization:
Cardiac catheterization is usually unnecessary.
Treatment:
Treatment is surgical closure of the ductus.
4. Aortico Pulmonary Septal Defect:
This defect consisting of a hole between the ascending aorta and the main pulmonary artery. Here there is no abnormality in the aortic valve, pulmonary valve, ventricular septum, or inter-atrial septum.
Symptoms resemble a large ventricular septal defect.
The clinical manifestations are similar as in patent ductus arteriosus. ECG and X-rays are almost similar to patent ductus arteriosus. Cardiac catheterization and selective aortography with the injection of contrast medium into the ascending aorta would document the site of the lesion.
Treatment:
Treatment is surgical correction.
5. Fistula of the Coronary Artery:
Fistula of the coronary artery exists between the coronary artery and the vein or the coronary artery may directly empty into the right ventricle. The physical signs may closely simulate patent ductus arteriosus as the machinery murmur is also common. The anatomic abnormality can only be demonstrated by injection of the contrast material into the ascending aorta. The treatment consists of surgical repair of the fistula.
6. Rupture of the Sinus Valsalva:
When one of the sinus of the valsalva of the aorta is weakened either due to congenital aneurysm or rupture and they open into the right atrium or the right ventricle. The clinical manifestations closely simulate that of the patent ductus arteriosus, except the machinery murmur which is heard so characteristically at the left upper intercostal space more on the right side.
Cardiac catheterization may be indicated and aortography with injection of a contrast material into the ascending aorta determines the site of the aneurysm and rupture. Surgical correction again is essential.