Desmond F. Duff

Mechanisms of cardiac arrhythmias after the Mustard operation for transposition of the great arteries.

To determine the mechanisms of the cardiac arrhythmias frequently seen after the Mustard operation for transposition of the great arteries, intracardiac electrophysiologic studies were performed in 52 children 1 to 8 years after the Mustard operation. Sinus nodal automaticity as judged from the response to rapid atrial pacing was abnormal in 28 of the 52 children. Sinoatrial conduction (conduction of the sinus impulse to the atrium) was found to be abnormal in three of nine patients studied with the atrial extrastimulus method. Conduction of the sinus impulse from the high right atrium to the atrioventricular (A-V) node was abnormally delayed in only 2 of 41 subjects. The low lateral wall of the right atrium was depolarized late in 3 of 11 subjects (including the preceding 2). Two subjects showed delayed A-V nodal conduction and one delayed His-Purkinje conduction. The mechanism of supraventricular tachycardia induced in the laboratory was determined to be sinoatrial nodal reentry in four subjects and atrial muscle reentry in four. Two of the four with atrial muscle reentry had prolonged high right atrium to low lateral right atrium intervals during sinus rhythm. Thus, damage to the sinus node remains the most common cause of arrhythmias after the Mustard operation. In addition, delayed atrial conduction may predispose to atrial muscle reentrant tachycardia.

Hemodynamic effects of dobutamine in children

Dobutamine is useful for augmenting cardiovasuclar function in adults. However, no information is available on the action of dobutamine in children. To determine its hemodynamic effects in children, we infused dobutamine into 12 children with congenital heart disease during diagnostic cardiac catheterization. We administered dobutamine in two doses: first 2 and then 7.75 microgram/kg per min for 10 minutes each. We meaured heart rate, cardiac output, systemic and pulmonary arterial, right atrial and pulmonary capillary blood pressures before and during the infusion of dobutamine. Systemic and pulmonary vascular resistances, cardiac index and stroke index were calculated. Cardiac output, cardiac index, stroke volume, stroke index and systemic arterial phasic and mean blood pressures increased sugnificantly (P less than 0.05) and pulmonary capillary mean blood pressure decreased significantly (P less than 0.05) during the infusion of each dose of dobutamine compared with control values. Heart rate, pulmonary and right atrial mean blood pressure and systemic and pulmonary vascular resistance were unchanged with either dose of dobutamine. We noted no adverse effect from the drug.

Infradiaphragmatic total anomalous pulmonary venous return. Review of clinical and pathological findings and results of operation in 28 cases.

Twenty-eight cases of infradiaphragmatic total anomalous pulmonary venous return are presented, 17 without associated complex intracardiac anomalies (group A), and 11 with additional complex lesions (group B). The anomalous site of connection was to the portal vein in 19 cases (68%), to the inferior vena cava in 4 (14%), the ductus venosus in 2 (7%), to the left hepatic vein in 2 (7%), and unknown in one. A patent foramen ovale was present in 82 per cent of cases in group A and 40 per cent in group B and was frequently associated with a small left atrium and left ventricle. Nine cases (8 in group A; 1 in group B) had surgical correction, with 3 long-term survivors. The surgical mortality was 66 per cent. The postoperative haemodynamic status of the 3 surviving patients is very satisfactory, though 1 had a residual atrial septal defect. Factors which adversely affected the surgical outcome were: (1) a critically ill infant, (2) small left atrium and left ventricle, (3) a patent foramen ovale rather than atrial septal defect, (4) systemic arterial oxygen saturation less than 70 per cent, and (5) pulmonary arterial pressure in excess of systemic arterial pressure. The mortality for the entire series was 93 per cent.

Elective Mapping and Surgical Division of the Bundle of Kent In a Patient With Ebstein's Anomaly Who Required Tricuspid Valve Replacement

A 14 year old girl with Ebsteins anomaly and Wolff-Parkinson-White syndrome without supraventricular tachycardia underwent closure of an atrial septal defect and tricuspid valve commissurotomy. Her postoperative course was complicated by her first episodes of recurrent debilitating paroxysmal supraventricular tachycardia. Severe tricuspid insufficiency with low cardiac output necessitated a repeat intracardiac operation. At reoperation the patient underwent successful tricuspid valve replacement with concomitent cardiac mapping and division of the bundle of Kent. In patients with heart disease requiring intracardiac repair who also have Wolff-Parkinson-White syndrome, elective surgical division of the anomalous bundle is recommended whether or not preoperative attacks of tachycardia have occurred.

Pulmonary vascular obstruction associated with cholesteryl ester storage disease

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Infradiaphragmatic total anomalous pulmonary venous return. Diagnosis and surgical repair in a 10-year-old child.

A unique case of infradiaphragmatic total anomalous pulmonary venous return in a 10-year-old girl is described. A persistent ductus arteriosus, ventricular septal defect, and large atrial septal defect were also present. Corrective surgery was performed at 10 years of age, with an excellent clinical result. The factors which permitted this unprecedented period of survival included non-obstructed drainage of the pulmonary venous blood into the inferior vena cava and a large atrial septal defect.

Left and right ventricular systolic time intervals in the newborn. Usefulness and limitation in distinguishing respiratory disease from transposition of the great arteries.

To determine their usefulness in the evaluation of the cyanotic newborn, left and right ventricular systolic time intervals were determined by echocardiography in 67 neonates; 21 were normal, 25 had neonatal respiratory disease, and 21 had dextro-transpositicn of the great arteries. The time intervals were measured from high-speed recordings of aortic and pulmonary valve motion. In normal newborns, the right ventricular pre-ejection period tended to be shorter than the left ventricular pre-ejection period while right ventricular ejection time was longer than that of the left ventricle. The ratio of right ventricular pre-ejection period/ejection time was lower than the ratio of these intervals for the left ventricle in 15 of 21 infants (mean 0 33 + 0 05 SD compared to 0-39 + 0-06, P < 0-001). In patients with respiratory disease, the ratio of right ventricular pre-ejection period/ ejection time was increased, primarily because of prolongation of the pre-ejection period. As a result, the ratio of right ventricular pre-ejection period/ejection time was greater than the left ventricular ratio in 15 of 25 patients and the ratios were equal in 8 (mean 0 44 + 0 11 vs 0-38 + 0-08, P < 0-005). Likewise, in infants with transposition of the great arteries, right ventricular pre-ejection period/ ejection time was greater than left ventricular pre-ejection period/ejection time (0.42 + 0-10 vs 0-26 + 0*06, P < 0.001), and the lowest values of left ventricular pre-ejection period/ejection time were recorded in this group. The pulmonary valve closed later than the aortic valve in 46 (70 %) of the subjects studied; simultaneous semilunar valve closure occurred in 19 (29%)°, and in 1 subject with respiratory disease the pulmonary valve closed before the aortic valve. Thus, the ratio of right ventricular pre-ejection period/ejection time was greater than the left ventricular ratio in both neonatal respiratory disease and transposition of the great arteries. A very low left ventricular ratio (less than 0.25) and delayed closure of the posterior semilunar valve suggest the latter diagnosis.

244 THE HEMODYNAMIC EFFECTS OF DOBUTAMINE IN CHILDREN

Dobutamine(DB), a relatively new inotropic drug, is useful for augmenting cardiovascular function in adults. There is, however, no information available concerning the effects of DB in children. To determine the hemodynamic effects of DB in children we infused DB into ten children with congenital heart disease during the course of routine cardiac catheterization. We infused DB at two doses (2 and 8μg/kg/min) for ten minutes each. We measured heart rate (HR), cardiac index (CI), systemic (SAP) and pulmonary arterial (PAP), right atrial (RAP), and pulmonary arterial wedge (PWP) blood pressures before and during infusion of DB. Systemic (SVR) and pulmonary (PVR) vascular resistances and stroke index (SI) were calculated.During infusion of 8μg/kg/min of DB, phasic and mean (x) SAP increased from 108/60,80 to 148/74,105 mm Hg (p<.05); CI increased from 3.6 to 4.6 L/min/m2 (p<.05); and SI increased from 38 to 48 ml/beat/m2. These indices also were increased significantly (p<.05) from control during infusion of 2μg/kg/min of DB.Phasic and mean PAP, PWP, RAP, HR, PVR, and SVR were unchanged from control at both doses of DB. We noted no adverse effects from the drug.DB appears to be a useful inotropic agent to augment cardiovascular function in children.