Isolated aortic stenosis-development of pulmonary hypertension in childhoodJJ Dalal, HL Kulkarni, AP Jain, KG Nair
Department of Cardiology, K.E.M Hospital, Parel, Bombay-400012, India
Pulmonary hypertension is uncommon in children with isolated congenital aortic stenosis, and even when present is usually mild. It is primarily due to transmission of the elevated left ventricular end-diastolic pressure through the pulmonary capillary circulation and may be then further elevated by reflex vasoconstriction. In some cases the stretching of a patent foremen ovate secondary to elevated left atrial pressure; may lead to a significant left to right shunt which further enhances pulmonary hypertension. This report discusses two cases of isolated aortic stenosis developing pulmonary hypertension in childhood.
There are various causes of left ventricular outflow tract obstruction such as valvular and supravalvular aortic stenosis, and fixed and dynamic forms of subvalvular stenosis.  Aortic stenosis forms 3% of all congenital heart diseases.  Congenital valvular aortic stenosis may be classified as unicuspid, bicuspid, tricuspid, undifferentiated and membrane type, the anatomical structure usually correlating with the age, and commonly bicuspid in these below 15 years. 
Pulmonary hypertension secondary to resistance to left ventricular filling may be due to many factors such as systolic hypertension, left ventricular outflow obstructions, coronary artery disease and altered compliance as in patients with cardiomyopathy.  Though left ventricular failure can raise the pulmonary artery pressure as high as 90 mm Hg.  this is uncommon, the rise usually being mild to moderate. This is a report of two children with significant pulmonary hypertension secondary to isolated valvular aortic stenosis.
Two children with severe aortic stenosis and pulmonary hypertension were studied. Electrocardiographic and roentgenographic study was performed in both cases.
Echocardiograms were recorded using a Unirad diagnostic Ultrasound Unit model 902. Recordings were made on a photography film 120 size using a Graflex 197 A, Camera.
Cardiac catheterization data was recorded with a Sanborn model 760 on a three channel recorder.
A.P., a 5 year old boy presented with a history of grade II dyspnoea and exertional syncope of two years' duration. There was no history of angina or congestive cardiac failure. His physical and mental milestones were normal. There was no history of rheumatic fever.
Examination revealed an averagely built boy with normal facies and a regular pulse rate of 100/min. The pulse upstroke was slow and a carotid thrill was present. His B.P. was 100'70 mm. Hg., in both the upper limbs. There was no cyanosis or clubbing. The apex was located in the 5th left intercostal space just outside the midclavicular line. Auscultation revealed a normal splitting of the second heart sound with a slight accentuation of the pulmonic component. An aortic ejection click followed by a grade 5/6 ejection systolic murmur were present in the aortic area.
The chest X-ray showed a normal cardiothoracic ratio with no evidence of post-stenotic aortic dilatation. There was evidence of pulmonary venous congestion. His ECG showed an axis of + 70° with biventricular hypertrophy and T wave inversions in V5 and V6. His vectorcardiogram showed a frontal plane QRS axis of + 80° with a clockwise loop. The horizontal plane showed a type C loop. Echocardiography revealed a normal mitral valve motion. The left ventricular cavity size was normal but there was a marked thickening of the left ventricular posterior wall. The aortic valve closure line was eccentric with full opening of the leaflets and no evidence of calcification.
Cardiac catheterization data are depicted in [Table 1]. The transventricular gradient. recordings are shown in [Figure 1] (See on page 11GB). Aortic root angiography revealed a deformed aortic valve with no evidence of aortic incompetence (See [Figure 2] on page 116B).
At surgery a deformed bicuspid severely stenosed aortic valve was found. The opening was enlarged by splitting the function for a small distance along the commissural line.
K.B., a 12 year old boy was admitted with a history of exertional dyspnoea, angina and exertional palpitations of 3 years' duration. There was no history of syncope or congestive cardiac failure. There was no past history of rheumatic fever.
On examination, the patient was small built with a pulse rate of 90/min, and a blood pressure of 90/60 mm.Hg, in both the upper limbs. There was no cyanosis or clubbing. Cardiovascular examination revealed the apex beat in the 6th left intercostal space in the anterior axillary line. A mild right ventricular heave and a basal systolic thrill were present. On auscultation, the second sound was normally split with an accentuation of the pulmonary component. An aortic ejection click followed by a grade 4/6 ejection systolic murmur were present in the aortic area and conducted to the carotids.
His X-ray showed a cardiac enlargement (cardiothoracic ratio 65%) with the presence of pulmonary venous congestion. His ECG showed an axis of + 90° with evidence of biventricular hypertrophy (See [Figure 3] on page 116B) . The echocardiogram showed a significant enlargement of the left ventricle (systolic dimension - 4.0 cm., diastolic dimension = 5.1 cm.). The aortic valve was not calcified and the closure line was central. Cardiac catheterization data are depicted in [Table 1].
At surgery a severely Stenosed tricuspid aortic valve was present. The obstruction was relieved by slitting open two of the three commissural fusions.
The presence of isolated aortic valvular stenosis in childhood favours the aetiological factor to be congenital rather than rheumatic.  The fact that many of these valves are structurally abnormal further stresses this possibility. Echocardiography has been helpful in non-invasively detecting these abnormalities,  as in case 2, where the eccentric aortic valve closure line suggested a bicuspid valve. This echocardiographic feature is not diagnostic,  but in the present case the bicuspidity was confirmed at surgery.
Braunwald,  in a study of hundred cases of congenital aortic stenosis found a 16% incidence of pulmonary - hypertension and in only four of these was the pulmonary hypertension more than mild, leading him to conclude that significant pulmonary hypertension in isolated aortic stenosis signified very severe obstruction or an associated intracardiac shunt.
The pulmonary hypertension in patients with isolated aortic stenosis is due to retrograde transmission of the elevated pulmonary venous pressure across the capillary bed and reflects the elevated left ventricular end-diaistolic pressure. , In both cases in the present study, cardiac catheterization has revealed s: vere critical aortic stenosis  and marked elevation of left ventricular enddiastolic pressures. The raised left ventricular end-diastolic pressure generally results from left ventricular failure, but may also be due to reduced ventricular compliance  Because of the small difference in the pressures between the pulmonary artery and the left atrium which normally averages only 6 to 9 mm Hg., an elevation of the left atrial pressure causes an equal or slightly greater increase of pulmonary artery pressure. The occasional further rise of pulmonary artery pressure, as present in both the cases in this study, is suggestive of a reflex vasoconstrictive element and results. in
The absence of any atrial shunting in both our cases showed that the high pulmonary artery pressure was predominently based on the transmission of the high left ventricular end-diastolic pressure and reflex vasoconstriction.
We are thankful to Dr. C. K. Deshpande, Dean, K.E.M. hospital for allowing us to publish this material.
[Figure 1], [Figure 2], [Figure 3]