The first cardiac surgery to close a patent ductus1 and to create an artificial ductus,2 was performed by a team consisting of a surgeon and a pediatri' cian interested in children's heart disease. They used the diagnostic armamentarium of that time: history, physical examination, an x-ray, a 3-lead electrocardiogram, and a complete blood count, Dr. Helen Taussig augmented these diagnostic procedures with cardiac fluoroscopy, analyzing each cardiac chamber as well as the amount of pulmonary vascularity and pulsations in the pulmonary artery, and the barium swallow to decide which way the aorta arched, whether there were any retroesophageal vessels, and whether the left atrium was enlarged. This information was necessary for preoperative assessment of the cyanotic child with typical tetralogy of Fallot or tricuspid atresia. The operation consisted of anastomosis of the end of the subclavian artery, on the side opposite that to which the aorta arched, to the pulmonary artery on that side. One could also diagnose coarctation of the aorta by simple clinical tools when that operation came into being.3
However, when patients presented with atypical or complex cardiac lesions, it was evident that additional and more precise diagnostic means were needed. Cardiac catheterization and angiocardiography filled the need. As these studies became increasingly informative and safe even for newboms, and miniaturization of operating room equipment and perfection of postoperative care brought the "ideal" age for surgery into the newborn period, it became commonplace to perform cardiac catheterization with selective angiocardiography prior to all operations except for the simple patent ductus arteriosus. Now, as noninvasive techniques have been developed that provide anatomic and physiologic information, we have begun to reconsider whether catheterization is essential prior to surgery.4
Let us consider some of the common childhood conditions that require surgery and current recommendations about preoperattve cardiac catheterization.
COMMON CARDIAC CONDITIONS DURING CHILDHOOD
Patent Ductus Arteriosus
Patent ductus arteriosus has long been a "stethoscope diagnosis. " The characteristic sign is a continuous murmur with late systolic accentuation in the pulmonary area (the second and third left interspaces). The pulmonic component radiates to the lung fields. This diagnosis is more easily made when the child is supine rather than upright. Physiologic significance of the ductus is indicated by the size and overactivity of the heart, width of the pulse pressure, the radiologie evidence of increased pulmonary blood flow and left ventricular enlargement, and electrocardiographic evidence of left ventricular hypertrophy. All children with a persistently patent ductus need closure of the ductus, usually by suture ligation. They should be operated on in infancy if they are in cardiac failure or if they fail to thrive. Echocardiography with Doppler studies visualizes the ductus and the continuous shunt of blood through it. Unless there is something atypical about these patients' findings, they do not require preoperative cardiac catheterization.
Atrial Septal Defect
The stethoscope is also used to make the diagnosis of atrial septal defect (ASD). In an asymptomatic, acyanotic, often slender child with a left precordial bulge, a grade 2 to 3 of 6 ejection-type systolic murmur can be heard in the pulmonary area along with a widely and fixedly split second heart sound. When the left-to-right shunt is sizable, a short, mid-diastolic murmur can be heard in the tricuspid area. X-ray shows right-sided enlargement and engorgement of the main pulmonary artery and branches. If the electrocardiogram shows right axis deviation and right bundle branch block, the defect is usually a secundumtype of defect, the common type. If on the other hand, there is left axis deviation with right bundle branch block, the defect is in the primum location. Echocardiography with Doppler studies can confirm this diagnosis, estimate the amount of shunt, and identify the drainage of most of the pulmonary veins and the function and character of the mitral valve. Surgery is indicated for children with ASD. Information obtained by Doppler studies usually suffices without catheterization before surgery. Indeed for ASD, catheterization with angiocardiography provides only indirect evidence of effects of the shunt; it cannot image the hole. This is possible by two-dimensional echocardiography, which can display the defect and assess flow.
Ventricular Septal Defect
Unlike the other two left-to-right shunting lesions just discussed, in which surgery is indicated for almost all patients with the clinical picture despite absence of symptoms, ventricular septal defect (VSD) needs surgical repair only in those with a demonstrable burden on the heart or lungs. Such a burden indicates the infant or child has a sizable left-to-right shunt through a large or a medium-sized defect, or associated aortic régurgitation. The majority of children have a small defect and are not candidates for surgery.
The stethoscope detects the hallmark of VSD, the holosystolic murmur at the lower left sternal border. Presence of an enlarged and overly active heart with left- and sometimes right-sided cardiomegaly on x-ray, and left ventricular hypertrophy on electrocardiogram indicates volume overload of the heart and pulmonary circulation. Accentuation of the pulmonic closure sound indicates pulmonary hypertension. An early diastolic murmur at the second and third left parasternal spaces identifies aortic régurgitation.
Cross -sectional echocardiography with Doppler confirms the presence of the medium- or large-sized VSD, and identifies the location (eg, perimembranous, muscular) and the number of defects. Doppler studies can also estimate the shunt and pulmonary pressure and identify any valvular régurgitation or possible ductal patency or ASD. Therefore, it is not always essential to do preoperative cardiac catheterization for the infant or child with a large VSD. If the decision for surgery rests on measuring the pulmonary arterial pressure and resistance, and determining whether elevated pressure is fixed, catheterization is needed.
Coarctation of the Aorta
Coarctation of the aorta is a bedside diagnosis made when a discrepancy in strength of pulses and in pressure in the arms and legs is noted. Symptoms range from cardiac failure in infancy to the customary freedom from symptoms in childhood. Surgery is indicated unless the Coarctation is mild and there are no arteries of collateral circulation. It is crucial to know the degree of collateralization before planning surgery. The measurement of blood pressure in arms and legs does not give this information. The pressure in the arms may be near normal because the Coarctation is mild, in which case there is no need for collateral circulation, or because there is rich collateral circulation in association with severe Coarctation of the aorta.
Echocardiographic imaging of the entire aortic arch, area of coarctation and coarctation shelf, as well as patency of the ductus and size of the descending aorta, is usually excellent. Doppler estimates of grathents across the left ventricular outflow tract and coarctation, as well as flow through a ductus, provide physiologic information. The problem concerns estimating adequacy of collateral circulation. If that can be judged, because rib-notching is present on x-ray or because large intercostals are imaged just below the coarctation, then surgery can proceed without catheterization.
A special situation is that of the newborn in cardiac failure due to the coarctation. These infants are often critically ill and should be treated promptly for cardiac failure. Surgery should begin as soon as the child is stable. Frequently, ventricular septal defect is associated with coarctation. The echocardiogram can determine whether the septum is intact or defective, and if defective, whether there is a large VSD or a single ventricle. This information may suffice for planning the next step in management - to relieve the obstruction to aortic flow.
The severity of aortic stenosis can be judged by the Doppler-measurable systolic pressure grathent. The site of stenosis, usually valvular but sometimes sub- or supravalvular, can also be displayed using Doppler methodology.
The ejection-type aortic systolic murmur detects aortic stenosis. The x-ray usually shows no cardiac enlargement. The electrocardiogram often underestimates the severity of stenosis. If it shows left ventricular hypertrophy and "strain," however, the stenosis is severe.
Valvulvar thickening and eccentric closure of the stenotic aortic valve, as well as the amount of hypertrophy of left ventricular free wall and septum, are usually well appreciated. A discrete subaortic stenosis and other forms of subaortic stenosis are also well recognized echocardiographically. If Doppler flow volocity and estimate of pressure grathent across the outflow tract of the left ventricle are out of keeping with the clinical findings, catheterization is needed.
Pulmonic stenosis, whether valvular or sub- or supravalvular, can be recognized with the stethoscope, and its severity judged by the degree of right ventricular hypertrophy and "strain" indicated by the electrocardiogram. Although clinical and echocardiographic data can combine to select the child with moderate or severe stenosis for surgery, the advent of relief of the stenosis by balloon valvoplasty calls for cardiac catheterization.
Cyanotic Congenital Heart Disease with Decreased Pulmonary Blood Flow
Cyanotic congenital heart disease with decreased pulmonary blood flow needs surgical palliation or repair. A full workup that includes echocardiography and barium swallow to detect the side of the aortic arch may suffice before a shunt procedure to increase pulmonary blood flow. For intracardiac repair, however, more detailed analysis, through catheterization, of anatomy and function is needed. In addition, the origin and course of the coronary arteries should be identified to provide sufficient information for what is often complex surgery, eg, for repair of tetralogy of Fallot or tetralogy- like lesions, or for palliation by the Fontan procedure for tricuspid atresia or double inlet left ventricle.5
Transposition of the Great Arteries
Transposition of the great arteries is now recognized in the first few hours of a cyanotic newborn's life. The echocardiogram is essential; so too is cardiac catheterization, to perform the life-saving balloon atrial septostomy,5 which permits venous mixing at atrial level. This procedure is an essential management technique in centers that prefer to postpone physiologic repair, which consists of rerouting venous blood to match the transposed arteries. The "venous switch" operations are the Mustard6 and Senning7 operations. An option developed in the last few years is to perform the arterial switch operation in the newborn.8 If the operating room and surgeons are available to perform the switch, a balloon septostomy at catheterization may not be needed.
These examples of common anomalies for which surgery is often indicated provide some of the considerations involved in opting for or against preoperative cardiac catheterization. The cardiologie team must be highly experienced and capable in echocardiography with Doppler studies for the cardiologists and the surgeons at the center to rely on these studies as confirmation of the diagnosis before surgery.
1 . Grass RE, Hubbanl JP: Surgical ligarion of paient ductus artenosus: Reputi of dw Erst RiccesAil case. ifMA 1939; 112:729-731.
2. Blalock A. Taussig HB: The surgical treatment of malformations of Ae heart in which there is pulmonary srenusis or pulmonary atiesia. JAMA I1MS; 128:189-202.
3. Rashkind WJ: Historical aspects of surgery for congenital heart disease, J Thmnc Cantouac Stag 1982-, 84:6 19-42 5.
4. 14th Bethesda Conference: Noninvasive diagnostic instrumentation ta assessment of cardiovascular disease m the young. } Am Coll Cardio! 1985; 5(January iupp4):l6ZS-164S
5. Puntan F, Baud« L· Surgical repair of tncuspid atresia. Thorax 1971; 26:240-248.
6. Mustard WT: Successful tiro stage correction of transposinon uf the great vessels. Siafrj 1964; 55:469.
7. Semung A: Surgical correction of transposition of the great vessels inrgm 1959: 45:966-980.
8. fatene AD, Fontes VF. Paulina PP, et al: Successful anatomic correction of transposition of the &eat vessels. A preliminary repon. ?t?} Braj QndwJ 1975. 28:461-464.