Mair, Douglas D.

The April 1973 issue of Pediatrics contained a Letter to the Editor from Gerald B. Merenstein, M.D. In his letter, Dr. Merenstein was guilty of a fundamental error in the understanding of the mechanism of oxygen uptake by the tissues. Because this misconception is not uncommon, I believe that the topic deserves comment. Dr. Merenstein compared systemic arterial oxygen content of two neonates in a hypothetical example (he referred to oxygen content as oxygen capacity, but this error is relatively unimportant). His illustration was as follows:

Objectives.A multicenter retrospective study was conducted to investigate the possible metabolic causes of pediatric cardiomyopathy and evaluate the outcome of patients treated with l-carnitine.Methods.Seventy-six patients diagnosed with cardiomyopathy were treated with l-carnitine in addition to conventional cardiac treatment, and 145 patients were treated with conventional treatment only. There were 101 males and 120 females between 1 day and 18 years old. Cardiomyopathy diagnoses included dilated (148 patients), hypertrophic (42 patients), restrictive (16 patients), mixed diagnosis (11 patients), and 4 with an unknown type. Of 76 l-carnitine-treated patients, 29 (38%) had evidence to suggest a disorder of metabolism, and of 145 control patients, 15 (10%) were suspected to have a disorder of metabolism. These metabolic disorders were thought to be the cause for the cardiomyopathy of the patients. The duration of l-carnitine treatment ranged from 2 weeks to >1 year. Information was collected on length of survival (time-to-event), clinical outcome, echocardiogram parameters, and clinical assessments. Data were collected at intervals from baseline to study endpoint, death, transplant, or last known follow-up visit.Results.l-Carnitine-treated patients were younger than control patients and had poorer clinical functioning at baseline, yet they demonstrated lower mortality and a level of clinical functioning and clinical severity comparable to control patients on conventional therapy by the end of the study. An analysis of the interaction between clinical outcome and concomitant medications unexpectedly revealed that the population of patients treated with angiotensin-converting enzyme (ACE) inhibitors (40% of patients) had significantly poorer survival (although their greater likelihood for poor survival may possibly have made them more likely to receive ACE inhibitors).Conclusion.Results suggest that l-carnitine provides clinical benefit in treating pediatric cardiomyopathy. There is a need for further exploration of potential explanatory factors for the higher mortality observed in the population of patients treated with ACE inhibitors.

Six years have passed since the first successful surgical correction of truncus arteriosus. A review of our experience enables some conclusions regarding the operation. Patients with mild or moderate truncal valve incompetence do not need truncal valve replacement. Patients with severe truncal valve incompetence require valve replacement, which is associated with a significantly increased surgical mortality. The surgical mortality is not increased in hemodynamically favorable patients who have only one pulmonary artery. However, these patients are especially likely to have early development of severe pulmonary vascular disease. The surgical mortality for the patient with uncomplicated disease and two pulmonary arteries, with pulmonary resistance of less than 8.0 units m 2 , is 10%. In patients with pulmonary resistance between 8.0 and 12 units m 2 , the mortality is approximately three times greater. Patients with pulmonary resistances greater than 12.0 units m 2 are probably inoperable. Different hemodynamic criteria must be applied in assessing the operability of patients with a single pulmonary artery. A systemic arterial oxygen saturation less than 85% in a patient with two pulmonary arteries and without pulmonary artery stenosis or a pulmonary artery band usually indicates inoperability. Elective operation usually is deferred until a patient is four years old, but if the patient's clinical condition warrants, the procedure can be done at any time after the age of one year, with a good chance of success. Follow-up on most operated patients has been encouraging.

From 1957 through 1971, 18 patients whose ages ranged from 10 months to 18 years underwent surgical correction of tetralogy of Fallot with absent pulmonary valve. All patients had associated pulmonary arterial aneurysms; in two the left pulmonary artery also was absent. Right middle lobectomy had been performed previously on one patient for lobar emphysema; seven other patients had recurrent pulmonary infections. The ventricular septal defect was closed with a patch in 12 patients and by direct suture in 6. Concomitant infundibular resection was done in all. In four the narrow pulmonary valve annulus was enlarged with an outflow patch, and multiple radial incisions were made in the valve annulus in seven others. The pulmonary arterial aneurysms were not resected in any patients. There were three hopsital deaths (17%) and two late deaths. Complete heart block developed intraoperatively in three patients, all operated on prior to 1963, contributing to the early death of one patient and to the late deaths of the other two. In a follow-up of all 13 survivors at 8 months to 15 years (median 6 years), results were excellent and equal to those of patients who have undergone repair of tetralogy of Fallot with pulmonary valve.