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Treatment of paroxysmal supraventricular tachycardia in infancy
Appraisal therapy
and reappraisal Edited by Arthur
C. DeGraff
Treatment of paroxysmal supraventricular tachycardia
of cardiac
and Alan F. Lyon
in infancy
Dennison Young, M.D.* New York, N. Y.
P
aroxysmal supraventricular tachycardia of infancy occurs most prominently in the first month of life, with a decreasing frequency over the next 3 months. Ventricular conduction is usually 1 :l ; the rate varies from 160 to 300, with 180 to 200 usually the critical level. Brief episodes which last a few hours cause no clinical difficulty and are not a problem in treatment. Longer episodes (48 hours or more) almost invariably produce congestive heart failure, even though there is usually no underlying heart disease, and are an urgent indication for treatment. Whether the focus is clearly in the atrium, or in the node, or impossible to define, the therapy is the same and somewhat different from that of paroxysmal atria1 tachycardia in the adult. Treatment. Obviously all modalities of nursing care and adjunctive therapy will be directed toward such a sick infant: i.e., appropriate antibiotics if infection is present, humidified oxygen, proper positioning, a minimum of handling, feeding by nasogastric tube or parenteral fluids, and morphine for the restlessness and irritability. In some, the paroxysms terminate spontaneously, but this cannot be predicted for the individual patient. Reflex vagal stimulation by carotid sinus or eyeball pressure or by induced vomiting is rarely effective. Specific cardiac therapy Received for publication Dec. 9. 1963. *Physician-in-Charge. Pediatric Cardiology. Ave., New York 67, New York.
565
Department
is directed toward suppression of the ectopic focus of impulse-formation. Digitalis is almost invariably effective in “idiopathic” supraventricular tachycardia and slightly less so in these arrhythmias associated with the WolffParkinson-White syndrome (10 per cent of the cases). Digoxin, because of rapid absorption, relatively rapid dissipation, and uniformity of action whether given intravenously, intramuscularly, or orally is the glycoside of choice. The digitalizing dose in the first year of life is 75 pg per kilogram of body weight, except in premature infants, in whom 50 pg is probably safer. Half the calculated dose, either orally or intramuscularly, depending on the condition of the infant, is given initially, and then half of the remainder is given in 4 to 6 hours and the balance 6 to 8 hours later. Thus, presumably full digitalization will have been achieved within a period of 12 to 14 hours. If by then the arrhythmia has not been converted to a normal sinus mechanism, an additional one fifth of the digitalizing dose can be given at subsequent 4-hour intervals until conversion is achieved, or toxicity precludes further administration. Frequent electrocardiographic monitoring is mandatory for recognition of either conversion or evidence of toxicity. If conversion is accomplished, a of Pediatrics,
Mont&ore
Hospital,
210th
St. and Bainbridge
daily maintenance dose of cligosin is continued as one third to one fifth of the digitalizing dose, started 8 to 12 hours later and given in two portions. Usually, digitalis is so successful in the conversion of paroxysmal supraveiitricular tachyrardia to normal sinus rhythm in infants that, even in large pediatric centers, other drugs are rarely necessary. Should digitalis fail, quinidine is the nest drug to be used. Full digitalization is preferred prior to its use. Quinidine can be administered safely in doses of 4 to 6 mg. per kilogram of body weight by nasogastric tube at Z-hour intervals for four to five doses. Here, too, frequent electrocardiographic monitoring is necessary for recognition of toxic manifestations, these being, as with digitalis, premature ventricular contractions and widening of the QRS interval. Almost all attacks of paroxysmal supraventricular tachvcardia will be terminated by the use of digitalis alone or with quinidine. A few persist, however, and, not UJlCOlllJllOJl~~~, so much time has then elapsed that the clinical condition has become extremely critical. Therefore, despite the risk involved, the use of the rapidacting cholinergic or cholinomimetic drugs, such as neostigmine or methacholine, in a single dose, becomes imperative. Neostigmine may be given subcutaneously in a dosage of 0.013 mg. per kilogram of body weight. The recommended dosage of methacholine is 0.045 to 0.048 mg. per kilogram of body weight given subcutaneously, but, in our experience, a dosage of 0.50 mg. per kilogram of body weight has been Constant electrocardiographic effective. monitoring must be maintained subsequent to the administration of these drugs. It should be emphasized that methacholinc be administered only by subcutaneous route, and that atropine be readily available to counteract the side effects. In addition to the varying degree of heart block or cardiac arrest, vomiting, lacrimat.ion, salivation, and sweating may be prominent manifestations of less serious nature. Severe bronchospasm may be precipitated; this Jllay even require the administration of epinephrine in addition to atropine intra-
The fivefold potentiating efiect of neostigmine OII the cardiac action of nrethacholine sho~11d also be noted. Deaths have been reported with this condition. intravenous atropine tna\ abolish the reaction and must be used promptly. There is 110 significant experience with the use of procaine amide or with vasopressors, such as phenyvlephrine or norepinephrine, in the supraventricular tachycnrdia of infancy. To our knowledge, electrical countershock has not been used in infants, hut in view of its known effectiveness for such arrhythmias in adults, there seems to be no reason why it could not be used. Prophylaxis. After successful termination of the attack of paroxysmal supraventriculnr tnchycardia the question of the possibility of future attacks arises. It is cotnforting to know that in infants with the “idiopathic” variety whose initial attack has occurred within the first 4 months of life, recurrences are unlikely after a year. In those whose attacks are associated with the Wolff-Parkinson-\7\ihite syndrome, recurrences are rare after about 18 months of age. Although it is usual for an infant to have but one attack, this is not predictable for the individual. Consequently, it is advisable that the infant whose attack has responded to digitalis be kept on a maintenance dose for the nest month. With a recurrence, redigitalization is indicated until 1 year of age or so in the “idiopathic” group, and until 18 months of age in those with the Wolff-Parkinson-M’hite syrndrome. In the latter patients, as in initial therapy, in addition to digitalis, quinidine may also have to be administered in doses of at least 6 mg. per kilogram of body weight four times a day, and often in considerably larger amounts. Here, too, medication may be stopped after 1 month and observation for recurrence instituted. In those who require neostigmine or methacholine for conversion, prophylaxis with these drugs cannot be maintained. Should there be recurrences in such patients, it is advisable to initiate therapy with digitalis, to be followed by quinidme if necessary, before JTSOJ?iJlg to the parasympathomimetic drugs. venousl~~.
and reappraisal Edited by Arthur
C. DeGraff
Treatment of paroxysmal supraventricular tachycardia
of cardiac
and Alan F. Lyon
in infancy
Dennison Young, M.D.* New York, N. Y.
P
aroxysmal supraventricular tachycardia of infancy occurs most prominently in the first month of life, with a decreasing frequency over the next 3 months. Ventricular conduction is usually 1 :l ; the rate varies from 160 to 300, with 180 to 200 usually the critical level. Brief episodes which last a few hours cause no clinical difficulty and are not a problem in treatment. Longer episodes (48 hours or more) almost invariably produce congestive heart failure, even though there is usually no underlying heart disease, and are an urgent indication for treatment. Whether the focus is clearly in the atrium, or in the node, or impossible to define, the therapy is the same and somewhat different from that of paroxysmal atria1 tachycardia in the adult. Treatment. Obviously all modalities of nursing care and adjunctive therapy will be directed toward such a sick infant: i.e., appropriate antibiotics if infection is present, humidified oxygen, proper positioning, a minimum of handling, feeding by nasogastric tube or parenteral fluids, and morphine for the restlessness and irritability. In some, the paroxysms terminate spontaneously, but this cannot be predicted for the individual patient. Reflex vagal stimulation by carotid sinus or eyeball pressure or by induced vomiting is rarely effective. Specific cardiac therapy Received for publication Dec. 9. 1963. *Physician-in-Charge. Pediatric Cardiology. Ave., New York 67, New York.
565
Department
is directed toward suppression of the ectopic focus of impulse-formation. Digitalis is almost invariably effective in “idiopathic” supraventricular tachycardia and slightly less so in these arrhythmias associated with the WolffParkinson-White syndrome (10 per cent of the cases). Digoxin, because of rapid absorption, relatively rapid dissipation, and uniformity of action whether given intravenously, intramuscularly, or orally is the glycoside of choice. The digitalizing dose in the first year of life is 75 pg per kilogram of body weight, except in premature infants, in whom 50 pg is probably safer. Half the calculated dose, either orally or intramuscularly, depending on the condition of the infant, is given initially, and then half of the remainder is given in 4 to 6 hours and the balance 6 to 8 hours later. Thus, presumably full digitalization will have been achieved within a period of 12 to 14 hours. If by then the arrhythmia has not been converted to a normal sinus mechanism, an additional one fifth of the digitalizing dose can be given at subsequent 4-hour intervals until conversion is achieved, or toxicity precludes further administration. Frequent electrocardiographic monitoring is mandatory for recognition of either conversion or evidence of toxicity. If conversion is accomplished, a of Pediatrics,
Mont&ore
Hospital,
210th
St. and Bainbridge
daily maintenance dose of cligosin is continued as one third to one fifth of the digitalizing dose, started 8 to 12 hours later and given in two portions. Usually, digitalis is so successful in the conversion of paroxysmal supraveiitricular tachyrardia to normal sinus rhythm in infants that, even in large pediatric centers, other drugs are rarely necessary. Should digitalis fail, quinidine is the nest drug to be used. Full digitalization is preferred prior to its use. Quinidine can be administered safely in doses of 4 to 6 mg. per kilogram of body weight by nasogastric tube at Z-hour intervals for four to five doses. Here, too, frequent electrocardiographic monitoring is necessary for recognition of toxic manifestations, these being, as with digitalis, premature ventricular contractions and widening of the QRS interval. Almost all attacks of paroxysmal supraventricular tachvcardia will be terminated by the use of digitalis alone or with quinidine. A few persist, however, and, not UJlCOlllJllOJl~~~, so much time has then elapsed that the clinical condition has become extremely critical. Therefore, despite the risk involved, the use of the rapidacting cholinergic or cholinomimetic drugs, such as neostigmine or methacholine, in a single dose, becomes imperative. Neostigmine may be given subcutaneously in a dosage of 0.013 mg. per kilogram of body weight. The recommended dosage of methacholine is 0.045 to 0.048 mg. per kilogram of body weight given subcutaneously, but, in our experience, a dosage of 0.50 mg. per kilogram of body weight has been Constant electrocardiographic effective. monitoring must be maintained subsequent to the administration of these drugs. It should be emphasized that methacholinc be administered only by subcutaneous route, and that atropine be readily available to counteract the side effects. In addition to the varying degree of heart block or cardiac arrest, vomiting, lacrimat.ion, salivation, and sweating may be prominent manifestations of less serious nature. Severe bronchospasm may be precipitated; this Jllay even require the administration of epinephrine in addition to atropine intra-
The fivefold potentiating efiect of neostigmine OII the cardiac action of nrethacholine sho~11d also be noted. Deaths have been reported with this condition. intravenous atropine tna\ abolish the reaction and must be used promptly. There is 110 significant experience with the use of procaine amide or with vasopressors, such as phenyvlephrine or norepinephrine, in the supraventricular tachycnrdia of infancy. To our knowledge, electrical countershock has not been used in infants, hut in view of its known effectiveness for such arrhythmias in adults, there seems to be no reason why it could not be used. Prophylaxis. After successful termination of the attack of paroxysmal supraventriculnr tnchycardia the question of the possibility of future attacks arises. It is cotnforting to know that in infants with the “idiopathic” variety whose initial attack has occurred within the first 4 months of life, recurrences are unlikely after a year. In those whose attacks are associated with the Wolff-Parkinson-\7\ihite syndrome, recurrences are rare after about 18 months of age. Although it is usual for an infant to have but one attack, this is not predictable for the individual. Consequently, it is advisable that the infant whose attack has responded to digitalis be kept on a maintenance dose for the nest month. With a recurrence, redigitalization is indicated until 1 year of age or so in the “idiopathic” group, and until 18 months of age in those with the Wolff-Parkinson-M’hite syrndrome. In the latter patients, as in initial therapy, in addition to digitalis, quinidine may also have to be administered in doses of at least 6 mg. per kilogram of body weight four times a day, and often in considerably larger amounts. Here, too, medication may be stopped after 1 month and observation for recurrence instituted. In those who require neostigmine or methacholine for conversion, prophylaxis with these drugs cannot be maintained. Should there be recurrences in such patients, it is advisable to initiate therapy with digitalis, to be followed by quinidme if necessary, before JTSOJ?iJlg to the parasympathomimetic drugs. venousl~~.