Brenda E. Armstrong

Noninvasive detection of retrograde descending aortic flow in infants using continuous wave Doppler ultrasonography Implications for diagnosis of aortic run-off lesions

Continuous wave Doppler ultrasonography was utilized to detect and characterize descending aortic blood flow velocity patterns in 27 preterm and term infants with or without an aortic run-off lesion proximal to the descending aorta. The effects of coexistent intracardiac defects on the velocity time profiles were evaluated by comparing records from patients with no intracardiac defects or systemic run-off lesions to those with a variety of intracardiac defects but no systemic run-off lesion. No significant alterations were noted. In all patients, the velocity tracing in systole was triangular in shape. During diastole, however, there were qualitative and quantitative differences between patients with and without a proximal run-off lesion. In those without a run-off lesion, retrograde descending aortic flow was present only in early diastole, and aortic flow velocity oscillated around the zero baseline during mid and late diastole. In those with a run-off lesion, retrograde flow present in early diastole continued throughout diastole. Quantitatively, the ratio of the area under the retrograde flow portion of the tracing to the forward flow portion was significantly greater in those with a run-off lesion. The velocity time profiles obtained with CW Doppler were similar to those previously obtained invasively with electromagnetic flow probes of catheter-mounted velocitometers. CW Doppler ultrasonograpy provides a reliable, noninvasive method for describing descending aortic blood flow velocity in infants.

Factors affecting use of the Doppler-determined time from flow onset to maximal pulmonary artery velocity for measurement of pulmonary artery pressure in children.

Measurement of the time from onset to maximal or peak velocity (TPV) of pulmonary artery (PA) flow has been proposed as a noninvasive means of determining PA pressure. The effects of age, heart rate, increased PA pressure and flow, pulmonary valve obstruction and altered PA vascular resistance on this measurement were evaluated. In 84 children, aged 1 day to 18 years, TPV was measured using continuous-wave Doppler echocardiography. The children were separated into 3 groups. Group I (n = 33) consisted of children with no cardiovascular abnormalities. Group II (n = 33) consisted of children with a variety of cardiovascular diseases producing varying PA pressures and flows. Group III (n = 18) consisted of children who had valvular pulmonic stenosis with PA to right ventricular gradients greater than 40 mm Hg. Doppler studies of group II and III patients were performed in conjunction with measurement of PA pressures and flows at the time of cardiac catheterization. In group I TPV showed a significant negative linear correlation with heart rate (r = -0.86, p less than 0.001). The ratio of observed TPV to predicted TPV (TPVN) determined using the regression equation for TPV vs heart rate or TPV/TPVN was heart rate- and age-independent (p greater than 0.1) and ranged from 0.81 to 1.31 (mean 1.005). In group II TPV/TPVN was inversely related to the natural log of the PA pressures (systolic, r = -0.91; mean, r = -0.87; diastolic, r = -0.82; all p less than 0.01), whether pressure elevation was due to increased flow, resistance or left atrial hypertension.(ABSTRACT TRUNCATED AT 250 WORDS)

Late outcome of survivors of intervention for neonatal aortic valve stenosis

BACKGROUND This study examined the late outcome after intervention for neonatal aortic valve stenosis. METHODS Seventy-three neonates (59 boys and 14 girls) underwent intervention for critical aortic valve stenosis during the first 30 days of life at two institutions, The Hospital for Sick Children, London, and Duke University Medical Center, Durham, North Carolina. Procedures performed include closed valvotomy (n = 12), open valvotomy with inflow occlusion (n = 14), open valvotomy with cardiopulmonary bypass (n = 33), balloon valvotomy (n = 12), and other procedures (n = 2). The mean age at the first intervention was 8 +/- 1 days. RESULTS The hospital mortality was 52.1%. The mean duration of follow-up for the hospital survivors (n = 35) was 8.3 +/- 1.1 years. The actuarial survival for the hospital survivors was 93.3% +/- 4.7% at 10 years and 83.9% +/- 9.8% at 15 years, whereas event-free survival (reintervention, endocarditis, or early death) was 61.8% +/- 9.3% at 5 years, 34.2% +/- 10.8% at 10 years, and 27.4% +/- 10.6% at 15 years. Three patients have died and 11 patients have required aortic valve replacement during the follow-up period. The age at the initial intervention, the type of initial intervention, and the year of initial intervention were not predictive of early death or need for reintervention. At last follow-up, 26 of the long-term survivors (n = 32) were in functional class I and 6 were in functional class II. CONCLUSIONS Aortic stenosis in the neonatal period is a difficult problem with a high initial mortality. Late survival and functional class are excellent for patients surviving the initial hospitalization, but most require further intervention within 10 years.

The force-interval relationship of the left ventricle.

The force-interval relationship the dependence of cardiac contractility on the rate and pattern of stimulation has been shown to be independent of preload, but sensitive to the inotropic and disease state of the heart. The force-interval relationship was evaluated for the left ventricles of 42 patients, ages 1.5- 20 years, during cardiac catheterization using a micromanometer pressure transducer-tipped catheter and an atrial pacing electrode catheter. The left ventricular (LV) minor axis was monitored echocardiographically, and the end-diastolic dimension (EDD) and posterior wall thickness (PW) were measured. Hearts were paced at a variety of basic cycle intervals, to (1/heart rate), and two test stimuli were introduced at various times during a pause in the regular stimulation (test intervals t, and t2 were measured relative to the last regular systole before the pause). For t, < to and t2 2 tl + to Pma of the second test systole was greater than Pma for the last regular systole before the pause (equivalent to postextrasystolic potentiation). The ratio of these values of Pmax (test to regular) for systoles with equal LVEDDs, the force-interval ratio, was used to characterize the relationship. Patients were divided into three groups: group 1 (n = 17) patients had normal LVEDD, LVPW and pressure indices. Group 2 (n = 17) patients had increased LVEDD or LVPW but normal pressure indices. Group 3 (n = 4) patients had increased LVEDD and depressed pressure indices. The force-interval relationship was similar for groups I and 2: Pmax increased monotonically with t, or t2. However, the force-interval ratio was larger for group 2. The relationship for group 3 was different. Pmaz was a biphasic function of the test interval, increasing for small values of t, or t2 and decreasing for larger values of t,. The force-interval ratio was smaller than or equal to unity for short values of t,. This postextrasystolic depression was never found in groups I or 2.

Polysplenia with pulmonary arteriovenous malformations.

SummaryA patient with polysplenia syndrome, dextrocardia, left atrial isomerism, normal great vessel relationships, and no intracardiac shunts developed progressive cyanosis and clubbing. Pulmonary arteriovenous malformations (PAVMs) were diagnosed by angiography and confirmed by lung biopsy. Superior mesenteric arteriogram revealed hypoplasia of the intrahepatic portal vein branches and a portosystemic shunt. The possible etiologies of PAVMs are discussed.

Junctional tachycardia in infants and children after open heart surgery for congenital heart disease

Abstract Junctional tachycardia may occur in the postoperative period and is associated with mortality and significant morbidity in infants and children. 1–5 Limited numbers of postoperative patients have been reported. 2,4,6 Successful pharmacologic treatment of junctional tachycardia in infants and children has been limited. 2,4,6,7 This report describes the characteristics of junctional tachycardia in infants and children in the postoperative period and their treatment at Duke University Medical Center.

Epicardial Ventricular Pacemaker Electrode longevity in Children

While epicardially implanted electrodes remain the most widely used in children for ventricular pacing, their expected longevity remains unknown. The longevity of 126 such electrodes implanted from January 1970 through December 1985 was evaluated in 81 children followed up for 1 to 192 months (median 63). Age at initial implant was 1 day to 18 years. Each child had from 1 to 5 electrodes implanted; 85 electrodes were of the sutureless helical type and 41 were of the suture-fixated type. Electrode failure, defined as loss of capture with a high pacing threshold found at operation or sensing failure, occurred in 38 electrodes from 1 to 157 months postimplant (median 37). Mode of failure was high threshold with high impedance (n = 15), low impedance (n = 6), complete inability to pace (n = 8), sensing failure (n = 2) or high threshold with no measure of impedance (n = 7). Actuarial life table analysis of electrode longevity showed a 88 +/- 3% (standard error of the estimate) survival rate at 6 months with no significant decrease until 53 months (75 +/- 5%, p less than 0.05). There was then a gradual steady decrease to 49 +/- 7% by 101 months. From 101 to 157 months no significant decrease occurred. Survival rate decrease was greatest within the first 6 month period postimplant (-12%). Electrodes surviving to 6 months are highly likely to survive until 53 months. Of those surviving to 53 months, 74% should survive to 120 months.

Use of contrast echocardiography for evaluation of right ventricular hemodynamics in the presence of ventricular septal defects.

SUMMARY Intracardiac blood flow is altered in the presence of a ventricular septal defect (VSD), with different sizes of defects producing different flow patterns that can be visualized by peripheral injection contrast echocardiography. The utility of these patterns in allowing estimation of right ventricular pressure and resistance to ejection of blood from the right ventricle (RV) was investigated. Forty-four patients underwent 46 contrast echocardiographic procedures, all within 24 hours before cardiac catheterization. All patients were placed in one of four groups based on catheterization findings. Group I, which consisted of patients with no VSD, or a small VSD with a pulmonary-to-systemic flow ratio (Qp/Qs) < 1.5:1 and right ventricular pressure < one third systemic, had echo-dense material appear in the RV only. Group II consisted of those with moderate-sized VSDs with Qp/Qs 2 2.5:1 and right ventricular pressure 60-80% systemic; in these patients echodense material appeared in the RV and in the left ventricle (LV) anterior to the mitral valve. The contrast appeared in the LV in early diastole and cleared from the LV in systole, with none appearing in the aorta or left atrium. Time from the preceding QRS to appearance of echo-dense material in the LV divided by the R-R interval (appearance time to R-R interval ratio) was 0.62 - 0.69. Group III consisted of those with large VSDs, Qp/Qs > 3:1 and systemic right ventricular pressure with low pulmonary vascular resistance and no pulmonary stenosis. These patients had appearance of echo-dense material in the LV during early diastole anterior to the mitral valve as in group II, but the material remained in the LV to be ejected into the aorta. Appearance time to R-R interval ratio was the same as in group II. Group IV consisted of patients with tetrology of Fallot and one patient with a large VSD and increased pulmonary vascular resistance. Echo-dense material again appeared in the LV early in diastole and was ejected into the aorta during systole. The appearance time/R-R ratio was significantly less than in groups II or III, allowing a clear separation between those patients in group III from group IV. Contrast echocardiography allows estimation of the right ventricular pressure and evaluation of increased resistance to pulmonary flow due to either pulmonary stenosis (PS) or increased pulmonary vascular resistance in the presence of VSDs. This technique also provides a minimally invasive method which may be useful for serial evaluation of such patients, and will permit early detection of developing PS, and possibly increasing pulmonary vascular resistance. Decreasing right ventricular pressure due to spontaneous closure of the VSD may also be detected by this technique.

Catecholamine induced double tachycardia: case report in a child.

A six‐year‐old girl with syncope in association with atrial flutter‐fibrillation and ventricular tachycardia produced by exercise or emotion is presented. The tachycardias could be reproduced by low‐dose isoprolerenol infusion and were blocked by high dose propranolol therapy. Catecholamine‐induced tachyarrhythmias should be suspected in children with unexplained syncope in association with exercise or emotion.

Heart block in children - Evaluation of subsidiary ventricular pacemaker recovery times and ECG tape recordings

SummaryTo evaluate subsidiary ventricular pacemaker function in 20 children with congenital or surgically induced complete heart block, we measured recovery times following overdrive ventricular pacing. Long-term ECG tape recordings were performed in eight of these children. Ages ranged fom 1 month to 17 years. The resting R-R intervals ranged from 595 to 1,740 msec. The ventricles were paced at various cycle lengths of 400 to 1,000 msec with either transvenous electrode catheters or surgically implanted epicardial electrodes. His bundle recordings showed that the site of block did not allow separation of patients with symptoms from those without symptoms. Prolonged recovery times were present in patients with block above the His bundle recording site who had symptoms of syncope or dizziness, as well as in patients who had a wide QRS. However, some asymptomatic patients with heart block above the His bundle recording site also had long recovery times. None of the asymptomatic patients who had ECG tape recordings had paroxysmal tachycardia in more than 300 hours of recordings. However, one symptomatic patient with congenital heart block and a prolonged recovery time had brief episodes of paroxysmal ventricular tachycardia that produced no symptoms at the time of recording. The results suggest that the coexistence of prolonged recovery times and paroxysmal tachycardia may be predisposing factors to the development of symptoms in patients with complete heart block. We believe that further electrophysiologic investigation of this possibility is warranted in patients with heart block.