Biomedical subjects
Publications and source records attributed to D W Hannon.
This study provides normal fetal cardiac dimensional data in a large patient group over a wide range of gestational ages. Perpendicular imaging decreased lateral resolution error, resulting in normal values with narrower confidence limits than in prior studies.
We report a unique case of Kawasaki disease with late sudden death from obliteration of the lumen of the full length of the left anterior descending coronary artery. Sequential echocardiograms showed early uniform coronary dilatation that resolved before sudden death. The implications of obliterative "healing" of coronary ectasia are unknown.
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Congenital diseases of the aorta may be divided into three main groups. The most common group includes diseases which obstruct blood flow to the distal circulatory system. The second category includes those diseases which obstruct either the trachea or the esophagus. A third category of congenital diseases of the aorta includes abnormalities of the mechanical composition of the aorta. The major clinical manifestations included in each of these groups will be discussed.
This report reviews our experience with the use of adenosine for diagnosis and treatment of narrow QRS complex tachyarrhythmias in children. All electrocardiograms obtained since the introduction of adenosine for clinical use at one pediatric tertiary care institution during an 18-month period were reviewed, and those patients receiving adenosine were included for study. Of the 24 patients who received adenosine, the median age was 4 years; four neonates were included. Adenosine produced atrioventricular block in 21 (88%) of 24 patients. It terminated the tachyarrhythmia in 11 patients and produced atrioventricular block but did not terminate the tachyarrhythmia in 10 patients. The mechanism of the arrhythmia was known in three patients before adenosine administration. Adenosine was useful in establishing the mechanism of the tachyarrhythmia in 17 of the remaining 18 patients but was not useful in one patient, in whom the arrhythmia was successfully terminated because a good-quality electrocardiogram was not obtained during adenosine administration. Therefore the mechanism of the supraventricular tachycardia was ultimately determined for all patients in whom adenosine successfully produced atrioventricular block and had acceptable electrocardiographic tracings. Side effects were limited and transient. We conclude that adenosine was a safe and effective agent for the pharmacologic treatment of narrow QRS complex tachyarrhythmias in our patients, including those less than 1 year of age. If proper electrocardiographic recordings are performed during adenosine administration, it is also helpful in establishing the cause of the tachyarrhythmia.
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The effect of digoxin on contractility and symptoms in infants with a large ventricular septal defect (VSD) is controversial. Nineteen infants with symptoms of congestive heart failure due to a VSD were studied with load-independent indexes during 4 study periods: (1) before any medication; (2) while on chronic diuretics; (3) while on both diuretics and digoxin; and (4) while on diuretics alone, to determine if digoxin: (a) increases "contractility" when added to diuretic therapy; and (b) improves symptoms. Symptoms, signs (heart and respiratory rates, and weight gain), shortening fraction, preload (left ventricular end-diastolic dimension), afterload (left ventricular end-systolic wall stress) and contractility were measured at each period. The difference between the measured and predicted velocities of circumferential fiber shortening for the measured left ventricular end-systolic wall stress served as an index of contractility. Eighteen infants also underwent catheterization. Mean pulmonary-to-systemic blood flow ratio was 3:1. When digoxin was added to diuretics, contractility index was significantly greater than in control subjects (0.13 +/- 0.15 vs 0.0 +/- 0.12 circ/s, p = 0.04). When patients were again on diuretics alone (after discontinuation of digoxin), contractility index was no longer different. Symptoms and signs were not significantly improved by either diuretics or digoxin. It is concluded that in infants with a large left-to-right VSD shunt and receiving digoxin and diuretics, contractility index was significantly greater than in control subjects. However, neither diuretics alone nor in combination with digoxin improved symptoms significantly.
Forty-two infants with a ventricular septal defect (VSD) (21 asymptomatic and 21 symptomatic) were compared with 17 control infants to determine if symptoms of congestive heart failure (i.e., tachypnea/poor growth) were due to depressed contractility or defect size, or both. Echocardiographic indexes of defect size, left ventricular performance (shortening fraction), preload (left ventricular end-diastolic dimension), afterload (left ventricular end-systolic wall stress) and contractility (the relation between velocity of circumferential fiber shortening and wall stress) were measured. Clinical assessment included measurement of weight and respiratory rate. Pulmonary and systemic blood flow were assessed in 17 symptomatic and 3 asymptomatic patients by cardiac catheterization. Although there was no significant difference in age, the symptomatic group had significantly lower weight (5.5 +/- 2.9 vs 7.3 +/- 2.3 kg, p less than 0.05) and a higher respiratory rate (53 +/- 14 vs 43 +/- 6 breaths/min, p less than 0.05), compared with control subjects. The mean pulmonary to systemic blood flow ratio in the symptomatic group was 2.9:1. Preload indexed for body surface area was significantly higher in the groups with a VSD compared with control subjects (asymptomatic, 8.5 +/- 1.7 cm/m2; symptomatic, 9.1 +/- 1.7 cm/m2; control subjects, 6.8 +/- 1.1 cm/m2; p less than 0.05). Shortening fraction, afterload and contractility were not significantly different among all groups. A defect size greater than 0.5 cm (or defect size indexed for body surface area greater than 1.8 cm/m2) was predictive of the presence of symptoms. It is concluded that contractility is normal in infants with a VSD. Symptoms may be related to pulmonary congestion.(ABSTRACT TRUNCATED AT 250 WORDS)
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The effects of extracorporeal membrane oxygenation (ECMO) on cardiac function and its determinants (preload, afterload, contractility, and heart rate) are largely unknown, although some evidence exists that function may decrease. To determine whether cardiac function decreases and what changes in the determinants take place during and after ECMO, we observed 26 newborn infants with persistent pulmonary hypertension. Serial echocardiograms were performed before ECMO, during maximum cardiopulmonary bypass, and after ECMO. Cardiac function was assessed by using standard echographic ejection phase indices (shortening fraction and cardiac output). Heart rate, preload (left ventricular end-diastolic dimension and area), afterload (left ventricular end-systolic wall stress), and contractility (relationship between velocity of circumferential fiber shortening and wall stress) were also measured. Ejection phase indices significantly decreased during ECMO (shortening fraction 33% to 25%, cardiac output 205 to 113 ml/kg/min; p less than 0.05) and returned to normal after ECMO (shortening fraction 26% to 34%, cardiac output 107 to 240 ml/kg/per minute; p less than 0.05). Heart rate also significantly decreased during ECMO (158 to 118 beats/min; p less than 0.05). Preload significantly increased after ECMO (left ventricular end-diastolic dimension 1.4 to 1.6 cm, left ventricular end-diastolic area 1.9 to 2.2 cm2; p less than 0.05). There were no significant changes in contractility and afterload during any study period. We conclude that, although left ventricular ejection phase indices and heart rate decreased during ECMO, these changes were transient and resolved when bypass was terminated. Contractility and afterload did not appear affected by bypass.
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To characterize the sympathetic nervous system response to congestive heart failure (CHF) in infants and children, plasma catecholamine levels were measured in 102 subjects undergoing routine cardiac catheterization (mean age 3.3 years, range 0.1 to 14.7), including 61 with left-to-right shunts. Plasma norepinephrine levels were significantly higher (p less than 0.0001) in children with CHF than in those without CHF. A highly significant association (p less than 0.0001) was found between the level of plasma norepinephrine and severity of CHF symptoms. This relation was found for CHF secondary to lesions producing a left-to-right shunt and CHF resulting from primary myocardial dysfunction. In congenital lesions with a left-to-right shunt, plasma norepinephrine levels correlated well with size of the shunt (Qp/Qs) (r = 0.75, p less than 0.001) and degree of pulmonary arterial hypertension (r = 0.70, p less than 0.001). Elevation of plasma norepinephrine concentrations in infants and children are seen with severe CHF regardless of its origin.
By means of postoperative radionuclide angiography we identified a subset of infants undergoing primary repair of their ventricular septal defects (VSD) who had postoperative morbidity and ventricular dysfunction. Twenty-three consecutive infants undergoing repair of an uncomplicated VSD were studied. Radionuclide-determined postoperative ventricular dysfunction (VD), as defined by a left ventricular ejection fraction less than 0.30 2 to 4 hours after surgery, was correlated with clinical signs of postoperative morbidity. Six patients developed postoperative VD. Clinical correlates of VD included the use of postoperative inotropic support, increased number of postoperative intensive care days, and a low growth rate 3 months postoperatively. Potential predictors of VD were evaluated. A preoperative pulmonary-to-systemic blood flow ratio (Qp/Qs) greater than 3.0 and a pulmonary-to-systemic vascular resistance ratio (Rp/Rs) less than 0.20, taken in combination, gave a positive predictive value for VD of 100%. It is concluded that the preoperative Qp/Qs and Rp/Rs can be used to predict those infants at risk for postoperative morbidity following repair of their VSD.
Radionuclide equilibrium gated ventriculograms were performed in 23 infants before and after surgery for congenital heart disease using standard parallel hole general purpose collimation followed by a pinhole collimation technique to magnify images and improve spatial resolution. A second group of nine infants had pinhole collimated gated ventriculography during cardiac catheterization for comparison with cineangiographic ejection fraction. In group I, pinhole collimation gave improved ventricular and atrial separation over general purpose parallel collimation for determination of left ventricular ejection fraction (42 of 42 studies calculable vs 37 of 42) and for right ventricular ejection fraction (36 of 37 studies calculable vs 20 of 37). In patients with transposition, pinhole technique allowed right ventricular ejection determination in nine of nine studies but in only one of nine was right ventricular ejection fraction possible by standard parallel collimation. In group II, the correlation between left ventricular ejection fraction by cineangiography and pinhole radionuclide ventriculography was excellent (r = 0.95). The correlation for right ventricular ejection fraction between cineangiography and pinhole radionuclide ventriculography was 0.82. Pinhole radionuclide ventriculography is a useful, practical clinical tool that can be used to assess ventricular function in small infants in an intensive care or outpatient setting.
The incidence and timing of spontaneous closure of isolated secundum atrial septal defects are unknown. Twenty-nine consecutive infants under 12 months of age with clinical evidence of significant left-to-right shunting through atrial septal defects were evaluated by M-mode and two-dimensional echocardiography (2DE). All had right ventricular hypertrophy by ECG. Right ventricular, right atrial, and left atrial areas were measured and right ventricular and left atrial dimensions were obtained in all patients. Spontaneous closure of the defect in four infants was suggested by normalization of clinical examination and ECG and was documented by 2DE and M-mode echocardiography at 15 to 31 months of age. All of the remaining patients, who had suitable 2DE echocardiograms and who did not spontaneously close their defects, had enlarged right ventricular and right atrial areas. Left atrial areas were normal in the four who closed spontaneously and were large in all but three who did not close. The mean diameter of the defect was similar for all patients. The 14% incidence reported here may underestimate the true incidence of spontaneous closure, since seven patients had surgical closure, all prior to 30 months of age, the oldest age at which spontaneous closure was documented. An atrial septal flap, found in all four patients who closed spontaneously but only in 4 of the 16 patients who did not close spontaneously, may contribute in some way to spontaneous closure. Since spontaneous closure may occur up to 30 months, it seems clear that surgical closure should not be performed before that age unless medical management has failed to control symptoms.
Paroxysmal supraventricular tachycardia developed in two infants with structurally normal hearts and no evidence of ventricular preexcitation. In both infants, the onset of the arrhythmia was associated with the presence of an indwelling jugular venous catheter in the body of the right atrium. Repeated episodes of the arrhythmia occurred while the catheter remained in place. Restoration and maintenance of sinus rhythm could only be achieved after withdrawal of the catheter.
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