Usefulness of Blalock-Taussig shunt Doppler flow velocity profiles in the assessment of pulmonary artery pressure and flow

AIM

To assess the utility of continuous wave Doppler evaluation of velocity profiles across a Blalock-Taussig (BT) shunt in the evaluation of pulmonary artery pressure and pulmonary blood flow.

METHODS AND RESULTS

Eleven children with complex congenital heart disease with a BT shunt as the sole source of pulmonary blood supply were studied prospectively (median age 5 (0.3-21) months). Doppler evaluations of shunt flow velocity profile and cardiac catheterization were carried out simultaneously. Pulmonary artery pressure and flow were estimated using the modified Bernoulli equation and velocity time integral of shunt flow. There was a positive correlation between (1) the Doppler estimates for mean pulmonary artery pressure, using the diastolic flow velocity, and the mean pulmonary venous wedge pressure ( r = 0.93, SEE = 1.0 mmHG; P<0.001 ) and (2) the Doppler derived and calculated pulmonary blood flow ( r = 0.9, SEE = 0.19 l/min; P<0.001). In contrast, the Doppler estimates for mean pulmonary artery pressure using the peak or mean Doppler gradients were poor.

CONCLUSION

The diastolic BT shunt flow velocity can be used reliably to predict mean pulmonary artery pressure when a BT shunt is the sole source of pulmonary artery flow. There was agreement between Doppler predicted pulmonary blood flow and catheter based calculations. These findings may prove a useful tool for perioperative management.

Coronary normograms and the coronary-aorta index: objective determinants of coronary artery dilatation

This is a prospective study to establish the normal ranges of the proximal left (LCA) and right (RCA) coronary artery diameters in normal children. Echocardiographic measurements of the internal diameters of the LCA, RCA, and the aortic annulus (AoA) were performed on 390 Asians with normal hearts, between the ages of 2 months to 8 years. The maximal diameters of the LCA and RCA in diastole were measured at predetermined sites. The LCA and RCA diameters correlated linearly with age, height, weight, body surface area, as well as the AoA (Pearson's R > 0.8, p <0.005). Regression equations and z-score graphs were constructed. The coronary-aorta index (coronary artery to aortic annulus ratio) falls within a narrow range- LCA/AoA = 0.15 +/- 0.02 (range 0.09-0.21), RCA/AoA = 0.13 +/- 0.02 (range 0.09-0.20). This is independent of age, sex, weight, height, and body surface area. We have established reference ranges for proximal coronary artery diameters in normal children. The regression equations and z-score graphs for the LCA and RCA provide objective determination of coronary size abnormalities. The coronary-aorta index can serve as a quick guide to detect coronary dilatation.

Pulmonary artery diameters in premature infants: normal ranges

The aim of this study is to establish the norms for pulmonary arterial diameters in the premature infants. One hundred and thirty cross-sectional echocardiograms were performed on 62 premature neonates (23.4 weeks to 36 weeks gestation) in the Neonatal Intensive Care Unit. Except for small atrial septal defects/patent foremen ovale (< or =3 mm) or patent ductus arteriosus (PDA), babies with structural heart defects were excluded. The weight at echocardiography ranges from 470 grams to 2,445 grams, with a mean of 1,157 grams. The diameter of the pulmonary annulus (PA), left pulmonary artery (LPA) and right pulmonary artery (RPA) were measured at peak systole at predetermined sites. Sizes of the atrial septal defect and PDA were also measured, if present. There was no difference in the diameter between the left and right pulmonary arteries (p=0.254, paired t-test) in the same patient. After controlling for weight, the mean diameters of the LPA and RPA were larger in patients with PDA (p=0.002) compared to those without PDA (p=0.002), while their pulmonary annulus were comparable in size (p=0.691). Between the gestational ages of 23 and 36 weeks, the diameter of PA, LPA and RPA correlated linearly with weight (Pearson R = 0.84, 0.82, 0.65 and 0.71, respectively; p<0.0005). Prediction graphs and regression equations are given. These normal ranges can be used for assessment of pulmonary artery diameters in premature neonates.

Echocardiographic features and management of neonatal ductal aneurysm

OBJECTIVES

To determine the case incidence of ductus arterious aneurysm among our neonates, and to report on our experience in the presentation, echocardiographic features, management and outcome of this condition.

METHODS

Retrospective review of cases diagnosed within a 1-year period from 1 July 1998 to 30 June 1999.

RESULTS

Eight cases of neonatal ductus arteriosus aneurysm (DAA) were diagnosed from 1 July 1998 to 30 June 1999. There were 998 new neonatal echocardiograms done during this period, giving us a case incidence of 0.8 per 100 echocardiograms. Only 1 patient was diagnosed antenatally, all others were detected incidentally on echocardiography done for other indications. None had symptoms related directly to the DAA and there was no suggestive mediastinal mass on chest X-ray. Majority were term infants (88%) and there was a predominance of male infants (75%). Three were associated with patent ductus arteriosus (PDA), while in the others, the ductus arteriosus were non-patent at first echocardiography. In the 3 infants whose ductus arteriosus was patent, the PDA was inserted into the pulmonary artery from an unusually superior direction. Close serial echocardiography on some of our patients suggested that resolution of the aneurysm is by thrombosis, manifesting as an echogenic area, followed by regression. In our series, 7 had total resolution, while 1 patient had a persistent echogenic area which became progressively smaller.

CONCLUSIONS

We found ductus arteriosus aneurysms in 0.8% of our neonatal echocardiograms. An unusually superior insertion of PDA into the pulmonary artery is a marker for its presence. Asymptomatic aneurysms resolve spontaneously and should be managed expectantly. Thrombosis plays a part in the resolution of ductal aneurysm.

Thrombocytosis in childhood

INTRODUCTION

Thrombocytosis is a common condition in infancy and childhood. There are very few paediatric literature on its incidence and clinical significance.

METHOD

We conducted a prospective study over 18 months (January 1993 to June 1994) on all patients admitted with a platelet count done. Cases with platelet count > 600 x 10(9)/L were reviewed and followed-up. Serial platelet count were done at 1 week, 2 weeks, 3 weeks, 4 weeks, and then monthly until it normalised.

RESULTS

One hundred and thirty-five cases out of 10,288 admissions had raised platelet count. There was a preponderance of male (sex ratio M:F = 1.7:1). Majority was less than 1 year old. Seventy-eight percent had associated infection of which 2/3 were due to bacterial infections, Pneumonia was the most common bacterial infection associated with thrombocytosis whilst gastroenteritis was the most common cause for non-bacterial infection and Kawasaki's disease constituted the majority of the non-infective etiology. Cases with platelet count > 900 x 10(9)/L, 73.3% were due to bacterial infection. Three cases of Kawasaki's disease had platelet counts > 900 x 10(9)/L. Fifty-two percent of cases developed thrombocytosis within 4 days of illness. In nonbacterial infection, the thrombocytosis normalised by about 1 week after onset. For bacterial infection, the thrombocytosis normalised later depending on the severity of infection. In majority of the Kawasaki's disease, the platelet count normalised by the third week.

CONCLUSION

Primary thrombocytosis is rare in paediatric age group. None of the cases developed any symptoms associated with thrombocytosis. Secondary thrombocytosis is a benign and common phenomenon in children.

Transcatheter closure of patent ductus arteriosus using detachable spring coils

OBJECTIVE

To report our experience with transcatheter PDA closure using detachable spring coils.

METHODS

Suitable patients who presented between March 1996 to July 1997 were selected for coil occlusion of PDA after the diagnosis is confirmed on colour doppler echocardiography. Twenty-seven patients underwent an attempt at transcatheter closure of PDA with coils. Twenty-one were native ducts while 6 were residual ductal leaks following surgical ligation (4) and Rashkind umbrella occlusion (2).

RESULTS

The patients' age ranged from 20 months to 39 years (median 5.5 years) and weighed from 10.5 kg to 49 kg (median 21 kg). The PDA diameter ranged from 1.3 mm to 5 mm (mean 2.4 mm). Twenty-four patients had coils successfully deployed (one coil in each patient) and all had PDA diameter of < or = 3.5 mm. Seventeen had complete occlusion on echocardiographic colour doppler assessment within 24 hrs. Follow-up colour doppler assessment showed complete occlusion in all 24 patients by 6 months. There were no cases of coil embolisation or any other complications. Unsuccessful coil deployment was encountered in 3 patients with PDA diameter of > or = 4 mm.

CONCLUSION

The detachable coil system allows for complete control over coil release and therefore deployment is precise and complications are minimised. Transcatheter closure of PDA with the detachable coil is a safe and effective method especially for small ducts (< or = 3.5 mm).

Accidental ingestions in childhood

One-hundred and twelve cases of accidental poisoning were admitted over a 2-year study period (December 1990 to December 1992). Data was collected upon admission and patients were subsequently followed-up. Fifty-four percent of admission were boys. Majority of them were toddlers between the ages of 1 and 3 years. Thirty percent of accidental ingestions occurred during the school/public holidays. These occurred when the caretakers were preoccupied. Forty-nine percent of patients ingested oral medication; 16% ingested household liquids and the rest ingested other household products like cockroach tablets and thermometer mercury. The most commonly ingested medications were paracetamol, salicylate and bronchodilators, whilst chlorox, kerosene and detergents were the common household liquids ingested. The ability of the caregivers to quantitate the ingested product was poor. The mean hospital stay of the patients was 2.5 days. The majority of them were admitted for observation which did not require antidotes. Four cases were observed in the intensive care unit. There were no fatalities during the study period. Forty-four percent of the patients had samples taken for toxicology analysis, of which, less than half had positive results. All the patients were advised on the safety measures to look out for after admission. Less than 10% of cases had prior knowledge of such measures before the accidents occurred.

Occlusion of persistent left superior vena cava to unroofed coronary sinus using vena cava filter and coils

A 48 year old female with complex cyanotic heart disease and pulmonary hypertension was partly cyanosed because of a persistent left superior vena cava draining into an unroofed coronary sinus. The left superior vena cava, which measured 22 mm in diameter, was successfully occluded with a Günther Tulip Vena Cava Mreye Filter which acted as a barrier for embolisation coils.

The changing trend in the pattern of infective etiologies in childhood acute lower respiratory tract infection

The etiologic agents causing acute lower respiratory tract infection (LRTI) in hospitalized children were compared for 1995 and 1988. Between May 1994 to April 1995, 397 children were admitted to Tan Tock Seng Hospital for acute LRTI compared to 240 children in 1988. The following criteria for LRTI were used: (i) age less than 12 years with a community-acquired LRTI; (ii) presence of cough or fever of less than 2 weeks' duration; and (iii) presence of tachypnea, chest retractions or pulmonary infiltrates on chest X-ray. Sputum cultures were considered suitable for culture if there were less than 25 epithelial cells per low power field. Moraxella catarrhalis was considered only if heavy growth of more than 3+ was seen. Etiological agents were found in about 70% of patients in both studies. Viruses constituted 41.3% of the etiologic agents in 1995 but constituted only 28% in 1988; 36% had a bacterial etiology in 1995 compared to 15% in 1988. The most common bacteria in 1995 was M. catarrhalis (34.7%) followed by non-type B Haemophilus influenzae (33%). In contrast, in 1988, Mycoplasma (33%) was the predominant organism followed by H. influenzae (17%) and M. catarrhalis (11.4%). The increased incidence of M. catarrhalis could be due to antibiotic selection. A mixed viral-bacterial etiology was found in 12.3% of the 1995 cohort. The majority of the bacteria were positive by sputum cultures; only 4 (3.3%) had positive blood cultures. No penicillin resistance was detected in 1988; however, in 1995, penicillin resistance was found in 17% of the Streptococcus pneumoniae, 38.5% of H. influenzae and 83% of M. catarrhalis. It was also found that 30% of the S. pneumoniae were also resistant to erythromycin, and 23% were resistant to sulfamethoxaxole-trimethoprim; 5% of the H. influenzae had multiple resistance to erythromycin, sulfamethoxazole-trimethoprim and chloramphenicol. Among those patients with antibiotic resistance, 30% had received prior antibiotics of which 18% had had two or more antibiotics, frequently erythromycin or amoxycillin/ampicillin. Judicious use of antibiotics is required to check the rising trend of antibiotic resistance.