David W. Hannon

Plasma norepinephrine levels in infants and children with congestive heart failure

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.

Comparative electrophysiologic and coronary hemodynamic effects of diltiazem, nisoldipine and verapamil on myocardial tissue*

The effects of diltiazem, nisoldipine (a nifedipine derivative) and verapamil on electrical and mechanical activity were studied in isolated canine Purkinje fibers and in isolated human atrial appendage. The actions of these three drugs on atrioventricular (A-V) conduction and coronary resistance were studied in open chest dogs in which autonomic effects were minimized by alpha and beta receptor blockade, bilateral vagotomy and atrial pacing after crushing of the sinus node. In isolated canine Purkinje fibers superfused with 5.4 m M of potassium in Tyrodes solution, normal action potentials and tension development were observed. Administration of diltiazem, nisoldipine and verapamil produced complete excitation/contraction uncoupling. The 50 percent effective concentrations for each drug in relation to tension development were calculated to be: diltiazem, 3 × 10 −7 M ; nisoldipine, 1.4 × 10 −8 M ; and verapamil, 4.2 × 10 −8 M . The ease with which the effects of the drugs could be washed out differed among the three agents. The percent of control tension achieved during washout was 40 percent for diltiazem, 75 percent for nisoldipine and 90 percent for verapamil. The reductions in tension development were accompanied by reductions in plateau amplitude and action potential duration at 50 percent of repolarization. Action potential duration at 90 percent of repolarization was significantly decreased by diltiazem, unchanged by nisoldipine and significantly increased by verapamil. In potassium-depolarized, isoproterenol-restored canine Purkinje fibers that demonstrated slow channel-dependent electrical activity, diltiazem, nisoldipine and verapamil all blocked action potential and subsequent tension development. These effects of diltiazem were completely reversed after 30 minutes of washout, but the effects of nisoldipine and verapamil were more difficult to reverse. In human atrial tissue, these three agents also abolished spontaneous slow channel-dependent action potentials. All three drugs produced excitation-contraction uncoupling and blocked slow channel-dependent electrical activity in canine and human cardiac tissue presumably by blocking the slow inward current. The different effects of each drug on action potential configuration suggest that each drug may also significantly affect other membrane currents. In intact open chest dogs, each drug lengthened atrial-His conduction times without affecting intraatrial or intraventricular conduction times. Coronary resistance was also decreased by each drug. High concentrations of each drug produced second degree A-V block and severe hypotension. As with the studies in isolated tissues the decreasing order of potency was nisoldipine, verapamil and diltiazem.

Relation of symptoms to contractility and defect size in infants with ventricular septal defect

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)

Use of adenosine for diagnosis and treatment of tachyarrhythmias in pediatric patients

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.

Return of plasma norepinephrine to normal after resolution of congestive heart failure in congenital heart disease.

Abstract Plasma norepinephrine is elevated in both adult and pediatric patients with congestive heart failure (CHF), and the degree of elevation corresponds to the severity of the CHF.1–4 It is not known whether this abnormal increase in adrenergic activity is reversible with the resolution of CHF.

Magnetic resonance imaging for diagnosis of pulmonary vein stenosis after “correction” of total anomalous pulmonary venous connection

Abstract Stenosis of individual pulmonary veins is a rare cause of obstructed pulmonary venous blood flow that may be difficult to diagnose. 1 Recent reports 2,3 have shown that pulmonary artery wedge angiography and pulsed Doppler echocardiography are useful in assessing such stenosis. Magnetic resonance imaging (MRI) has the potential advantage of the ability to define anatomic and flow characteristics of cardiovascular lesions. This case report describes the use of MRI in demonstrating the anatomy and flow characteristics of pulmonary venous obstruction in an infant after repair of obstructed total anomalous pulmonary venous connection (TAPVC) to the left vertical vein.

When is Echocardiography Unreliable in Patients Undergoing Catheterization for Pediatric Cardiovascular Disease

Technologic advances in echocardiography (e.g., better spatial resolution, Doppler, and color flow mapping) have improved our ability to demonstrate anatomy and physiology in previously problematic conditions, precluding catheterization and angiography in some instances. However, diagnostic catheterization remains necessary in other instances. The aims of this study were to determine whether echocardiography alone was sufficient to delineate the anatomic and flow abnormalities in patients subsequently selected to undergo catheterization and, if not, under what circumstances was echocardiography unable to establish the definitive diagnosis. Echocardiograms of 252 infants and children who underwent catheterization during a 14-month interval were analyzed retrospectively to determine whether the echographic assessment was nondiscrepant (group 1) or discrepant (group 2) with the catheterization assessment. Any deviation in the complete accurate assessment constituted a discrepancy; identification of more than one discrepancy in a single patient was possible. Independent variables included patients age, weight, operative status, use of color flow mapping, echocardiograph operator, and interval between echocardiogram and catheterization. To determine whether the discrepancies were clinically significant, data from patients in group 2 were reviewed independently by three cardiologists to determine whether patient management would have changed given the added data provided by catheterization. Echocardiographic evaluations were discrepant in 155 instances. In 54 of 155 instances (35%), discrepancies were judged to be clinically significant (group 3). Twenty-three of 54 cases (43%) involved extracardiac lesions (i.e., aortic arch, pulmonary arterial, bronchial collateral, and pulmonary venous anomalies), 20 of 54 (37%) involved pressure gradients, 7 of 54 (13%) involved intracardiac lesions, and 4 of 54 (7%) involved coronary arterial lesions.(ABSTRACT TRUNCATED AT 250 WORDS)

Pinhole radionuclide ventriculography in small infants.

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.

NORMALIZATION OF PLASMA NOREPINEPHRINE FOLLOWING REPAIR OF INTRACARDIAC LEFT TO RIGHT SHUNTS

Plasma norepinephrine (PNE) is elevated in patients with conogestive heart failure (CHF) and the degree of elevation corresponds to the severity of the CHF. This study was performed to determine whether PNE returns to normal in children with CHF secondary to a left to right intracardiac shunt after repair of the defect. We measured PNE in 32 children (aged 0.1 to 13.3 years) undergoing cardiac catheterization and divided them into four groups for analysis: I) Pre-operative (op) patients with severe CHF from an intracardiac left to right shunt (N=10), II) Intracardiac left to right shunts repaired 0.3 to 4.0 years previously (N=7) who had the same degree of left to right shunting (Qp/Qs) and CHF pre-op as Group I, but post-op were asymptomatic on no medications, III) Pre-op patients with cyanotic heart disease and no CHF (N=7), and IV) Cyanotic heart disease (N=8), repaired 0.7 to 7.0 years previously.For group II, there was an inverse relationship between the LN PNE and time interval since repair (R=−0.71). We conclude that PNE is markedly elevated in patients with severe CHF but returns to normal in a log linear fashion after repair of intracardiac left to right shunts and resolution of CHF. In contrast, PNE in cyanotic heart disease is normal pre- and post-operatively.