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Ventricular septal defects (VSDs) are the most common group of congenital cardiac malformations and occur in 2–6 in 1000 live births.1,2 The pattern of defect can range from a tiny hole in the muscular septum, with a good chance of spontaneous closure, to complicated lesions requiring open heart surgery.3–6 The prognosis of patients with VSD is good; a large study of patients with congenital VSD found 87% survival at 25 years although there was a small but significant risk of serious arrhythmia and sudden death even among patients with small defects.6 Left ventricular function in some patients may be impaired although the mechanism involved is uncertain.7
The prevalence of additional cardiac malformations has been defined in selected groups of patients. In 156 infants with defects large enough to consider cardiac surgery, investigation by echocardiography and cardiac catheterisation confirmed the presence of infundibular pulmonary stenosis in 25%, subaortic ridges in 3%, and persistent ductus arteriosus in 15%.8 A study of 207 patients with muscular VSD found an association with coarctation of the aorta in 11 patients (5%).4 Studies of other cardiac abnormalities, such as persistent ductus arteriosus, confirmed the coexistence of VSD (eight of 146 patients in one group, 5%).9 The presence or development of such abnormalities may necessitate cardiac surgery or long term follow up.
The prevalence of additional abnormalities identified by modern ultrasound technology including colour flow Doppler has not been examined prospectively in a large unselected population. Transthoracic echocardiography with Doppler colour flow mapping is a sensitive and specific technique for the confirmation of clinically suspected VSD2,8,10 and the delineation of associated structural abnormalities.
The aim of this study was to examine the prevalence and characteristics of cardiac abnormalities in patients with congenital VSD by using modern echocardiographic techniques and to identify any further structural abnormalities that may develop with age. Patients with conotruncal abnormalities (transposition of the great arteries, tetralogy of Fallot, persistent truncus arteriosus, or double outlet right ventricle), univentricular heart, and atrioventricular septal defects have a different clinical entity with higher morbidity, mortality, and a corresponding need for corrective surgery. They have not been included in this study.
Details were prospectively recorded for consecutive patients referred to a regional centre for paediatric cardiology or associated satellite clinics who were found to have congenital VSD. VSD was diagnosed by clinical examination and confirmed by transthoracic echocardiography including Doppler colour flow mapping. Additional cardiac abnormalities were sought in these patients and recorded if present.
In addition, patients followed up at an adult congenital heart disease clinic with a known diagnosis of VSD were identified.
Subsequent follow up visits were recorded, as well as details of clinical events including the need for cardiac surgery and cardiovascular complications such as endocarditis and death.
Pulmonary valvar stenosis was diagnosed by echocardiography according to conventional criteria and classified as mild (<25 mm Hg), moderate (25–49 mm Hg), or severe (> 49 mm Hg) based on estimated pressure gradients calculated by measurement of flow velocities across the valve.11 Infundibular pulmonary stenosis was graded in severity by the same criteria.
Aortic valve prolapse was diagnosed when a deformed aortic valve pivoted from the crest of the interventricular septum, noticeable in the parasternal long axis view.12 The degree of aortic regurgitation was defined as trivial if the colour flow regurgitation jet was limited to just below the aortic valve, mild if it did not quite reach the mitral valve tip, moderate if it reached the mitral valve tip, and severe if it was beyond the mitral valve tip.13
The χ2 test was used for frequency comparisons between groups and was applied only where more than 20% of the expected values in the contingency table are greater than 5. Percentages shown are of the total study population unless otherwise specified. We used SPSS software (version 9.0, SPSS Inc, Chicago, Illinois, USA).
Between 1991 and 1998, 1448 patients with congenital VSD were identified and assessed by echocardiography. Figure 1 shows the age distribution, which is clearly bimodal, representative of the two patient populations (paediatric and adult groups) studied.
Associated cardiac defects
Table 1 shows additional associated cardiac defects in order of frequency for new paediatric referrals and adults seen at the adult congenital clinic. When all patients were considered together the most commonly associated cardiac abnormalities were infundibular pulmonary stenosis (5.8%), aortic prolapse (3.6%), pulmonary valvar stenosis (2.7%), osteum secundum atrial septal defect (2.2%), persistent ductus arteriosus (1.9%), and coarctation of the aorta (1.5%). The latter three defects listed were significantly less frequent in the adult group because most had been corrected in childhood by surgery or percutaneous intervention. Aortic valve prolapse was more frequent in the adult group (6.7% v 1.3%, p < 0.0001), as was infundibular pulmonary stenosis (7.8% v 4.3%, p < 0.005).
The majority of VSDs occurred in isolation but in 19.6% of patients they were associated with one other cardiac abnormality, in 2.4% with two other abnormalities, and in only 0.1% with three abnormalities (table 2). Muscular defects were less common in the adult group as would be expected due to spontaneous closure in childhood and adolescence.
In their first year of life 743 patients were assessed. Figure 2 shows eight years of prospective clinical follow up with 4% cumulative all cause mortality (29 deaths) by the age of 8 years. The majority of deaths occurred during the first year in infants with additional genetic abnormalities as table 3 and table 4 show. No patient developed endocarditis in the follow up cohort. In addition, 16 patients were assessed in the first year of life but were then lost to follow up and have not been included in this analysis. Eleven of these patients had small muscular defects.
Figure 3 shows an increase in the number of patients with aortic regurgitation with age with a peak between 11 and 15 years of age.
Overall 105 patients in the adult group required corrective surgery (including percutaneous closure) although in most cases this was performed in childhood with a mean (SD) age of 4.7 (4.7) years at the time of surgery. During the prospective follow up of the paediatric group 106 patients required corrective surgery (12.6%), and this was performed at a mean (SD) age of 1.4 (2.1) years.
Of the 15 paediatric patients with aortic valve prolapse, moderate or severe regurgitation was detected in five (33%). Of the 46 adult patients with aortic valve prolapse, moderate or severe regurgitation was apparent in five (all of whom underwent surgery with aortic valve replacement in three and cusp resuspension in two) and 19 patients had trivial or mild aortic regurgitation.
We have found that about 20% of patients with congenital VSD have additional cardiac abnormalities. Most abnormalities were detected at the initial assessment but aortic prolapse and infundibular pulmonary stenosis may develop subsequently. Such abnormalities may influence management, although the overall prognosis from VSD was excellent in this population and the risk of endocarditis was low.
Secondary aortic regurgitation may result from the venturi effect of high velocity flow beneath an inadequately supported right aortic valve cusp14 or following maldevelopment of the aortic commissure. Continuing clinical follow up is therefore required for patients with VSD beyond adolescence and in our study 82% of cases of secondary aortic regurgitation were detected before the age of 20 years. Extending the follow up of patients to the age of 30 would allow the detection of 89% of patients with secondary aortic regurgitation. The indications for aortic valve surgery in aortic root prolapse are controversial. Recent evidence suggests that the progression from mild to severe incompetence may be rapid and that surgical intervention should be early.15
Echocardiography with colour flow mapping is an effective technique for the detection of VSD16 and in fact is more sensitive than cardiac catheterisation in the detection of multiple septal defects.8 Echocardiography has also been shown to be as sensitive as cardiac catheterisation in the detection of other cardiac abnormalities, such as infundibular pulmonary stenosis.8 Echocardiography continues to develop with advances such as harmonic imaging17 and transducer characteristics18 that allow higher frequency imaging and improved image quality. Colour flow Doppler processing has been the most important advance in the detection of VSD, as flow across the interventricular septum can be easily detected.19 Although other techniques are evolving such as the use of contrast agents,20 three dimensional echocardiography,21,22 and magnetic resonance imaging,23 it seems unlikely that these advances will significantly increase the confirmation rate of clinically suspected VSD or of associated cardiac abnormalities.
This study was not primarily designed to measure long term clinical outcome and all cause mortality was recorded to ensure that cases were not missed because of misclassification of death. The prevalence statistics of associated cardiac abnormalities reflects true clinical practice, as patients were assessed consecutively without selection bias.
Echocardiography confirms the presence of additional cardiac abnormalities in 22% of patients with congenital VSD. These should be sought during the initial assessment, and the subsequent development of aortic prolapse or infundibular pulmonary stenosis should be monitored during clinical follow up. Follow up to the age of 30 years allows the detection of most but not all cases of secondary aortic regurgitation.
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