Doppler assessment of the interventricular pressure drop in patients with ventricular septal defects

Ventricular septal defect

Ventricular septal defects account for up to 40% of all congenital cardiac malformations. The diagnosis encompasses a broad range of anomalies, including isolated defects and those associated with other congenital cardiac malformations. Presentation, symptoms, natural history, and management of ventricular septal defects depend on size and anatomical associations of the anomaly, patient's age, and local diagnostic and interventional expertise. In this Seminar, we describe the anatomical range of ventricular septal defects and discuss present management of these malformations. Genetic determinants, diagnostic techniques, physiological considerations, and management challenges are examined in detail. Unfortunately, in many circumstances, evidence on which to guide optimum management is scarce. We present some longer term considerations of ventricular septal defects in adolescents and adults, with particular emphasis on patients with raised pulmonary vascular resistance and Eisenmenger's syndrome.

Bidirectional shunt flow across a ventricular septal defect: pulsed Doppler echocardiographic analysis

Pulsed Doppler echocardiographic and hemodynamic examinations were performed in 31 patients (mean age 17.8 years) with isolated ventricular septal defect (VSD). Three groups were studied: group I (n = 6) patients had severe pulmonary vascular obstructive disease (PVOD); group II (n = 12) patients had pulmonary hypertension (PH) without severe PVOD; group III (n = 13) patients had no PH. Bidirectional shunting was detected in 9 VSD patients (6 in group I and 3 in group II). Patients with low to moderately elevated right ventricular pressures demonstrated left-to-right shunting across the defect throughout the cardiac cycle. When systolic pressure in the right ventricle reached approximately 60% of the left ventricular pressure, right-to-left shunting occurred across the defect during early and mid diastole. However, in patients with Eisenmenger syndrome (group I) the right-to-left shunting occurred during late systole with continuation during the early and mid diastolic period. The earlier occurrence of right-to-left shunting (index < 0.5 second) signifies the presence of severe PVOD.

Right heart pressure determination by Doppler in infants with tricuspid regurgitation

Doppler and direct measurements of right ventricle to right atrial pressure drop were made during cardiac catheterisation on 28 occasions in 26 infants with congenital heart disease. Age was 10 days to 12 months (median 4.5 months), and weight was 3.1 to 9.0 kg (median 4.7 kg). We measured peak velocity of tricuspid regurgitation by continuous wave Doppler, and the pressure drop was calculated using the modified Bernoulli equation (delta p = 4v2). There was a high correlation (r = 0.95) between direct and Doppler measurements. Doppler values tended to underestimate the right ventricle to right atrial pressure drop, but this was not of clinical significance (mean 2 mm Hg). The 95% confidence interval for the Doppler velocity was -0.41 to +0.26 m/sec, and was consistent across the range of pressures studied. Variability between observers was tested, by two observers performing sequential paired examinations on 16 newborn babies with tricuspid regurgitation. The coefficient of repeatability was 6.3 mm Hg (95% confidence interval 4.7 to 9.5 mm Hg) or 0.26 m/sec (0.18 to 0.50 m/sec). This method of right ventricular pressure estimation, validated previously only in older children and adults, is a reproducible and accurate technique in infants with tricuspid regurgitation.

Estimation of pulmonary vascular resistance in patients with ventricular septal defects by echo-Doppler cardiography

The pulmonary vascular resistance is one of the parameters considered in the evaluation of patients with ventricular septal defects. We describe a new method to estimate resistance. The method estimates the systolic resistance in the pulmonary circulation and we assume that there is a linear relation between this resistance and the traditional resistance in which a continuous flow in systole and diastole is assumed. The systolic resistance was compared to the traditional resistance index in a group of patients whose invasive data were evaluated retrospectively. A close correlation between the two estimates of resistance was found and when the results were applied to another group of patients examined non-invasively and invasively there was no significant difference between the invasive resistance index and the non-invasive estimate arrived at by the new method.

Changing role of non-invasive investigation in the preoperative assessment of congenital heart disease: a nine year experience

The total surgical experience of a supraregional paediatric cardiology unit over a nine year period (January 1980 to December 1988) was reviewed to assess the effect of the introduction of the full range of ultrasound techniques. A total of 1517 patients underwent cardiac surgery (955 cardiopulmonary bypass, 562 closed procedures). Of these, 485 patients (32%) did not undergo cardiac catheterisation before operation: 217 bypass (23% of all procedures under cardiopulmonary bypass) and 268 closed procedures (48%). The overall ratio of catheterisations to operations for patients undergoing palliative or corrective surgery fell from 0.97 (1980) to 0.38 (1988). The patients were classified as (a) neonates (0-28 days), (b) infants (one to 12 months), and (c) children (one to 14 years). The main impact of non-invasive surgical referral was in neonates (total catheter:operation ratio 0.38; neonates 0.2 for 1988). The surgical population was further divided according to the principal echocardiographic technique available: (a) 1980-4 cross sectional imaging; (b) 1985-6; imaging plus spectral Doppler ultrasound; (c) 1987-8; imaging plus spectral Doppler ultrasound and colour flow mapping. A fall in the catheter:operation ratio for all age groups was most pronounced in the last four years. This reflects increased familiarity and surgical confidence with non-invasive diagnostic assessment. The introduction of each new echocardiographic technique was associated with a significant fall in the total catheter:operation ratio compared with the preceding period. Six incorrect ultrasound diagnoses were made during the entire period; one of these patients died in the early postoperative period. The integration of Doppler ultrasound with cross sectional imaging has made non-invasive assessment an increasingly practical alternative to preoperative cardiac catheterization.

Echocardiographic spectrum of double inlet ventricle: evaluation of the interventricular communication

To determine the spectrum and associated anomalies of double inlet ventricle (single ventricle), echocardiographic data of 50 patients with double inlet ventricle were reviewed and compared with the data obtained by cardiac catheterization, cardiac surgery and autopsy. Standard echocardiographic planes were used to determine the cardiac anatomy and the size of the interventricular communication. Double inlet by way of two perforate valves was found in 44 patients. In 42 of the 44 patients the dominant ventricular morphology was of the left ventricular type (double inlet left ventricle); in 13 of these 42 patients stenosis of one atrioventricular (AV) valve was found. Double inlet right ventricle and double inlet indeterminate ventricle were each found in one patient. Double inlet by way of a common AV valve was found in six patients, all of whom had atrial isomerism. The diagnosis of double inlet ventricle was accurate by two-dimensional echocardiography in all 44 patients. A restrictive interventricular communication was shown in 13 patients and a nonrestrictive communication in 17 patients by cardiac catheterization. Patients with a restrictive interventricular communication had a significantly smaller interventricular communication area normalized by the body surface area (mean +/- SD 1.21 +/- 0.53 cm2/m2) than did those with a nonrestrictive interventricular communication (2.33 +/- 0.71 cm2/m2) (p less than 0.01). Infants with an aortic anomaly had a significantly smaller interventricular communication area (1.35 +/- 0.65 cm2/m2) than did those without an aortic anomaly (2.57 +/- 0.76 cm2/m2) (p less than 0.05). Echocardiography provides an accurate noninvasive diagnosis in patients with double inlet ventricle, offering reliable information about the restrictive interventricular communication.