Atrial tachycardia: a rare disease sheds light on common questions.
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Humans↗
Biomedical subjects
A Garson
Publications and source records attributed to A Garson.
Flecainide acetate for resistant arrhythmias in the young: efficacy and pharmacokinetics.
Drug efficacy and pharmacokinetics were assessed in 63 patients, aged 5 days to 30 years (mean 8 years), who received flecainide acetate for control of resistant arrhythmias. Doses of flecainide ranged from 59 to 225 mg/m2 body surface area per day (mean 141) in divided doses every 8 to 12 h and serum trough levels ranged from 0.10 to 0.99 micrograms/ml (mean 0.36). Flecainide controlled or partially controlled arrhythmia in 53 (84%) of the 63 patients: 7 of 7 patients who had the permanent form of junctional reciprocating tachycardia, 12 of 13 who had an atrial ectopic tachycardia, 10 of 10 who had ventricular tachycardia and 18 of 25 patients who had reentrant supraventricular tachycardia. Five of seven patients who had the latter arrhythmia were unsuccessfully treated with flecainide. They had Wolff-Parkinson-White syndrome and developed asymptomatic, incessant, slower orthodromic reciprocating tachycardia while receiving the drug. Transient blurred vision was reported in three patients and two patients had transient hyperactivity. No significant hemodynamic side effects were seen in any patient. Twenty-five patients underwent oral pharmacokinetic investigation. Young infants (less than 1 year of age) had a mean plasma elimination half-life (t 1/2) approximating that (11 to 12 h) found in older children and healthy adults; children aged 1 to 12 years had a shorter mean t 1/2 of 8 h. Dosing schedules based on milligrams per square meter body surface area correlated better with plasma flecainide levels than did dosing based on milligrams per kilogram body weight.(ABSTRACT TRUNCATED AT 250 WORDS)
Administration, Oral↗
Epicardial mapping: ventricular epicardial activation is unaffected by heart position.
Epicardial ventricular mapping was performed in five dogs during sinus rhythm with a sock array containing 41 bipolar electrodes. Maps were generated with a computer-assisted mapping system when the heart was in situ and when the heart was lifted by 44 degrees out of the chest. Times of earliest and latest epicardial activation in these two states did not differ. Despite a different frontal plane QRS axis, location of earliest activation was not affected by lifting the heart. In two of the five animals, the site of latest epicardial activation was minimally different from the heart in situ, but the general pattern of epicardial activation was unchanged. Therefore, the change in frontal plane QRS axis with lifting the heart was due to a change in heart position rather than a general change of heart activation.
Animals↗
Surgical treatment of arrhythmias in children.
Primary surgical treatment of many tachyarrhythmias in children is now possible. In those with life-threatening arrhythmias not responsive to any form of medical treatment, the choice for surgery is clear. These arrhythmias include atrial fibrillation with the Wolff-Parkinson-White syndrome, PJRT, or atrial ectopic tachycardia with severe congestive cardiomyopathy, incessant ventricular tachycardia in infancy, and recurrent sustained ventricular tachycardia in postoperative congenital heart disease. In the majority of patients, however, surgical treatment remains an option to be weighed carefully against chronic medical treatment. Surgery is now possible with very low mortality for infants and children with Kent bundles, atrial ectopic tachycardia, and the permanent form of junctional reciprocating tachycardia. The mortality, morbidity, and likelihood of eventual resolution of the arrhythmia with each type of management plan should be considered. With possible direct surgical ablation of atrial flutter and newer forms of catheter treatment of arrhythmias, the future looks promising.
Arrhythmias, Cardiac↗
Diagnosis and treatment of arrhythmias.
The preceding is intended as a guide to facilitate the recognition, interpretation, and management of vasodepressor syncope and pediatric cardiac arrhythmias. Drug dosages not provided in the text are readily available elsewhere. There are several important "take home messages" provided here, gleaned from this chapter--the "do nots." Do not (1) use digoxin chronically in overt WPW syndrome, (2) miss the diagnosis of long QT syndrome, (3) diagnose "SVT with aberration"--rule out VT first, (4) use sinus-suppressant drugs in patients with sick sinus syndrome without an implanted pacemaker, (5) use IV verapamil to convert SVT in patients less than 1 year old, with congestive heart failure or on beta-blockers, or (6) use ocular pressure to convert SVT.
Adolescent↗
Encainide for resistant supraventricular tachycardia in children: follow-up report.
Forty-one children (26 weeks gestational age to 20 years) with drug-resistant supraventricular tachycardia were treated with oral encainide, and 29 were followed for 3 to 34 months (mean 15). Diagnoses obtained by electrocardiographic criteria (23 patients) or electrophysiologic testing (18 patients) included permanent junctional reciprocating tachycardia in 15 children, paroxysmal atrioventricular reciprocating tachycardias (AVRT) in 13, atrial ectopic tachycardia in 4, atrial flutter in 1, chaotic atrial tachycardia in 5 and junctional ectopic tachycardia in 3. Encainide was completely effective in 54% (22 of 41 study patients) and partially effective in an additional 24% (10 of 41 patients), when combined with propranolol or verapamil. Within 1 month, 13 (32%) discontinued encainide for inefficacy or intolerance. Encainide was most effective in the treatment of permanent junctional reciprocating tachycardia (60% effective) and AVRT (69% effective). It controlled only 40% of primary atrial tachycardias. Encainide was well tolerated on a long-term basis in patients not experiencing symptoms during initiation. In study infants younger than age 6 months, encainide was associated with excessive QRS aberrancy during initiation in 4 of 13 (31%), compared with 3 of 28 (11%) in older children. Ventricular proarrhythmia occurred in 2 children and 1 died suddenly. Mean effective encainide dose was 3.5 mg/kg/day or 86 mg/m2/day. In 4 children who had nonextensive metabolism of encainide, the drug was ineffective. Encainide is effective in the treatment of some resistant forms of permanent junctional reciprocating tachycardia and AVRT in otherwise healthy children. Children younger than age 6 months and those with either previous proarrhythmic events or severe cardiac dysfunction appear to have a high incidence of adverse effects.
Administration, Oral↗
Experimental right ventriculotomy: effects on local propagation at a small size scale.
Repair of tetralogy of Fallot and ventricular septal defect frequently requires righ ventriculotomy. Although the mechanisms for right bundle branch block (RBBB) have been frequently discussed, the pathogenesis of this electrocardiographic abnormality is still unknown. To determine if disruption of the distal subendocardial Purkinje fiber network in the right ventricular free wall produced RBBB and if cellular electrophysiologic abnormalities in or near the ventriculotomy scar could provide a substrate for conductance disturbances, we investigated the electrocardiographic and electrophysiologic effects of experimental right ventriculotomy in 12 beagles. On the surface electrocardiogram no significant differences in QRS duration (lead II) or morphology were apparent between the control group (n = 6) and the postventriculotomy animals (n = 6) (QRS duration = 34 +/- 4 versus 34 +/- 7 ms, respectively). Using microelectrode techniques, the right ventricular endocardial surface was carefully mapped. To facilitate analysis, data were grouped into five regions: outflow septum, outflow free wall, inflow free wall, and ventriculotomy region. No significant delays of regional activation were noted in the postventriculotomy group compared to the control group: outflow septum--30 +/- 16 versus 36 +/- 16 ms; outflow free wall--33 +/- 10 versus 38 +/- 19 ms, inflow septum--32 +/- 7 versus 33 +/- 13 ms, inflow free wall--35 +/- 11 versus 35 +/- 22 ms, and ventriculotomy region--32 +/- 10 versus 31 +/- 16 ms, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)
Action Potentials↗
Ethmozine (moricizine HCl): a promising drug for "automatic" atrial ectopic tachycardia.
Atrial ectopic tachycardia is an uncommon life-threatening supraventricular tachycardia in children and is resistant to usual antiarrhythmic drugs. Whereas the cellular mechanism of atrial ectopic tachycardia is unknown, atrial ectopic tachycardia may be due to a form of automaticity. Moricizine HCl has been used primarily for ventricular rhythm disturbances; the drug depresses abnormal automaticity and delayed after-depolarizations but has little effect on normal automaticity. Because of this property, we have used moricizine HCl in 4 patients with atrial ectopic tachycardia. As evidenced by continuous 24-hour Holter monitoring, moricizine HCl was successful in suppressing atrial ectopic tachycardia in each patient. During a limited follow-up (6 months) no side effects have occurred. Moricizine HCl is a promising primary drug for atrial ectopic tachycardia.
Adolescent↗
Usefulness of intravenous propafenone for control of postoperative junctional ectopic tachycardia.
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Child, Preschool↗
Newer antiarrhythmic drugs in children.
Our experience with the use of five new antiarrhythmic drugs for treating life-threatening arrhythmias in children will be briefly reviewed. Prevention of recurrent episodes of atrial flutter with digoxin and local anesthetic antiarrhythmic drugs often is only moderately successful, benefiting 65% of patients. Amiodarone is particularly useful for those patients who cannot be controlled on this regimen. We caution that the heart rate be monitored carefully when therapy with amiodarone is initiated in patients likely to have sick sinus syndrome. We have found mexiletine useful for controlling significant ventricular arrhythmias in patients with congenital heart disease. Likewise, 79% (11 of 14) of patients with ventricular tachycardia treated with amiodarone were well controlled. However, the range of disease categories (congenital heart disease, myocarditis, cardiomyopathy) in which amiodarone is effective is much broader than for mexiletine. Although other investigators have used amiodarone successfully for controlling supraventricular tachycardia in the Wolff-Parkinson-White syndrome or secondary to concealed accessory AV connections, we recommend surgical ablation. Propafenone has significantly improved our ability to control postoperative JET. Although JET is self-limited in duration and spontaneously remits, it frequently produces life-threatening hemodynamic compromise in the postoperative setting. Propafenone slows the ventricular rate into a range in which AV sequential pacing may be instituted. Generally, after 24 to 72 hours, the patient may be quickly weaned from propafenone. Chronic incessant supraventricular tachycardia (SVT) is frequently associated with a dilated cardiomyopathy. The two most common mechanisms of incessant SVT are PJRT and AET. We have found encainide and ethmozine extremely effective in suppressing tachycardia episodes in PJRT and AET, respectively. Medical therapy has been associated with few side effects.
Adolescent↗
Clinically significant differences between the "old" analog and the "new" digital electrocardiograms.
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Adolescent↗
Amiodarone efficacy in a young population: relationship to serum amiodarone and desethylamiodarone levels.
Serum amiodarone and desethylamiodarone levels were measured in children and young adults receiving chronic amiodarone therapy. The study population consisted of 34 children and young adults with ventricular tachycardia (36%), atrial flutter (36%), and recurrent supraventricular tachycardia (27%). The mean age was 12.9 +/- 8.6 years (range 4 months to 23 years) and the mean daily dose of amiodarone was 6.6 +/- 3.7 mg/kg/day (range 2.5 to 25 mg). Serum amiodarone and desethylamiodarone levels after 10.1 months (range 1 to 40 months) were 0.85 +/- 0.63 microgram/ml and 0.67 +/- 0.42 microgram/ml, respectively. In three patients for whom amiodarone therapy was unsuccessful, serum amiodarone levels were 0.27, 0.85, and 1.18 micrograms/ml. There was no significant correlation between serum amiodarone or desethylamiodarone levels and dosage of amiodarone. Four patients, all 13 years or older, developed toxicity (skin rash [one patient], keratopathy [two patients], and hyperthyroidism [one patient]). There was no correlation between serum amiodarone and desethylamiodarone levels and toxicity; although there was a trend toward elevated reverse serum triiodothyronine levels in patients who developed toxicity, the values fell within the range of those patients without toxic side effects. Serum amiodarone levels do not appear to be of great value in predicting efficacy and toxicity of amiodarone in children and young adults receiving chronic drug therapy.
Adolescent↗
The science and practice of pediatric cardiology in the next decade.
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Cardiac Catheterization↗
Electrical ablation of atrial muscle. I. Early and late anatomic observations in canine atria.
Electrode catheter ablation (ECA) of atrial muscle may be a useful technique for the treatment of drug-refractory supraventricular tachycardias originating in the right atrial free wall (RAFW). We performed this study in order to determine: (1) the safety of electrical shocks applied to the RAFW and (2) the early and late anatomic effects of ECA. Twelve beagle puppies, ranging in age from 2.0 to 7.5 months and weighting 2.3 to 8.0 kg, underwent electrical ablation of the RAFW, using energy doses of 100 to 400 J. At the highest energy doses tested (400 J), one puppy died of refractory ventricular fibrillation and one of low cardiac output. Atrial perforation and cardiac tamponade occurred in two puppies, each of which received one shock of 200 J. The area of myocardial damage following ECA shocks of 150 J was greater than for shocks of 100 J, 94 +/- 14 vs 56 +/- 11 mm2, respectively (p less than 0.02). Acutely, ECA produced transmural hemorrhagic necrosis. Eleven weeks after electrical ablation, atrial fibrosis was apparent at the site of ablation. In conclusion, ECA may be used to fulgurate atrial tissue in the RAFW. We recommend 150 J as a safe upper limit in small subjects, although higher energy doses may not produce cardiac perforation or adverse hemodynamic effects in larger subjects.
Animals↗
Electrical ablation of atrial muscle. II. Early and late electrophysiologic observations in canine atria.
Electrical ablation techniques (ECT) have had limited success in achieving control of arrhythmias originating in the right atrial free wall (RAFW). To ascertain determinants for successful ECT, we studied the clinical and cellular electrophysiologic effects of electrical ablation of the RAFW. After performing electrical ablation of the RAFW in 12 beagle puppies, the following studies were performed: Holter monitoring first 24 hours (eight puppies), and 11 weeks later (four puppies); clinical electrophysiologic study (four puppies); and microelectrode study (ME) (eight puppies). Arrhythmias (AR) and conduction disturbances (CD) frequently occurred immediately following ECT: ventricular tachycardia (VT) (seven puppies), junctional tachycardia (one puppy), and asystole or complete AV block (AVB) (four puppies). Holter monitoring during the first 24 hours after ECT revealed VT (four puppies), frequent ventricular premature depolarizations (one puppy), and type 2 second-degree AVB (four puppies). AR were rarely seen late after ECT. During clinical EP study 11 weeks after ablation, atrial fibrillation was induced in three of four puppies; none had AR prior to ECT. Early ME study revealed a nonhomogeneous atrial infarct--a central zone of "dead" cells surrounded by peripheral islands of depressed cellular activity. Cells with normal action potential characteristics were noted in between. We conclude that Electrical ablation of the RAFW is associated with a high incidence of early AR and CD. Because of the nonhomogeneous nature of tissue injury produced during ECT, careful atrial mapping is critically important. Local regions of conduction delay and block may provide a substrate for the late development of atrial arrhythmias.
Action Potentials↗
Cryoablative techniques in the treatment of cardiac tachyarrhythmias.
Of 175 patients treated surgically for potentially lethal or refractory cardiac tachyarrhythmias, 53 underwent mapping and definitive operation using cryoablative techniques as the primary or adjunctive method. Included were 16 patients with supraventricular tachycardia caused by accessory pathways (Kent bundle) in the right anterior or posterior paraseptal location. Cryoablation was successful in abolishing tachycardia in 93.7% (15 of 16). Six patients (100%) with permanent junctional reciprocating tachycardia were cured by cryoablation. Eighteen of 19 patients with atrial ectopic tachycardia were treated by cryoablation alone or in combination with excision of the atrial appendage, with success in 15 (83.3%). Five of these were left atrial foci cured by cryoablation. Fourteen right atrial foci were treated by excision of the appendage only (1 patient), excision of the appendage and local cryoablation (8 patients), and cryoablation alone (5 patients). Three of these underwent partial (2 patients) or complete (1 patient) atrial disconnection after excisional and cryoablative techniques failed to control the tachycardia. Multiple ectopic atrial foci were common (9 patients), and successful cryoablation was accomplished in 100% of the patients with a single atrial ectopic focus (10 patients) but in only 66% of those with multiple foci. Thirteen of 19 infants with critical ventricular tachycardia were treated by cryoablation at the site of the ectopic focus, either alone or in combination with excision of the area. Elimination of tachycardia was accomplished in 13 patients (100%). Myocardial hamartoma (Purkinje cell tumor) was the histological diagnosis in 11 of the infants with ventricular tachycardia.(ABSTRACT TRUNCATED AT 250 WORDS)
Adolescent↗
Incessant ventricular tachycardia in infants: myocardial hamartomas and surgical cure.
Infants with incessant ventricular tachycardia (occurring greater than 10% of the day) have generally been described in pathologic studies. This report describes 21 patients with incessant ventricular tachycardia present greater than 90% of the day and night; the age at diagnosis ranged from birth to 30 months (mean 10.5 months). The most common clinical presentation was cardiac arrest (11 patients, in 5 after digitalis for presumed supraventricular tachycardia); another 6 patients had congestive heart failure and 4 were asymptomatic. Three patients had coexisting Wolff-Parkinson-White syndrome. The rate of incessant ventricular tachycardia ranged from 167 to 440 (mean 260 beats/min) and the QRS duration from 0.06 to 0.11 second. The most common electrocardiographic (ECG) pattern (10 of 21) was right bundle branch block with left axis deviation, but other right and left bundle branch block patterns were observed. Conventional and investigational antiarrhythmic agents (nine patients received amiodarone) failed to eliminate incessant ventricular tachycardia in all. Electrophysiologic studies localized incessant ventricular tachycardia to the left ventricle in 17 (to the apex in 2, the free wall in 9 and the septum in 6) and to the right ventricular septum in 4. No structural abnormalities were found on the echocardiogram or angiocardiogram. All 21 patients had surgery at an age of 3.5 to 31 months (mean 16). In 15 a tumor was found: 13 myocardial hamartomas (9 discrete, 4 diffuse throughout both ventricles) and 2 rhabdomyomas (1 multiple). Myocarditis was found in one patient (the oldest). In four, only myocardial fibrosis was found; results of one biopsy were normal.(ABSTRACT TRUNCATED AT 250 WORDS)
Anti-Arrhythmia Agents↗
Mexiletine: an effective antiarrhythmic drug for treatment of ventricular arrhythmias in congenital heart disease.
The use of antiarrhythmic drugs to suppress ventricular arrhythmias in pediatric patients with a structurally or hemodynamically abnormal heart appears to improve long-term prognosis. The previously successful use of phenytoin to treat serious ventricular arrhythmias led to the investigation for an alternative antiarrhythmic agent, in the same antiarrhythmic drug class, for those patients who develop side effects or become intolerant to phenytoin's antiarrhythmic effect. Forty-two children and young adults (age range 5 months to 34 years, mean 15.5 years) were treated with mexiletine. Arrhythmias treated were ventricular tachycardia (25), ventricular couplets (8), multiform ventricular premature beats (4) and frequent uniform ventricular premature beats (5). Anatomic diagnoses included congenital heart disease (postoperative in 26, unoperated in 2), cardiomyopathy (7), no heart disease (4) and other (3). Thirty-three patients had been previously treated with 1 to 5 (mean 1.6) antiarrhythmic drugs. In the short term, ventricular arrhythmias were effectively suppressed in 30 (71%) of all 42 patients treated. During follow-up (ranging to 42 months, median 10.6), 18 (60%) of the 30 acute responders continued to have excellent control. Early suppression of ventricular arrhythmias was more effective in patients with congenital heart disease (89%) than in those with cardiomyopathy (29%) or no heart disease (43%) (p less than 0.01). Initial complexity of ventricular ectopic activity had no effect on treatment results. Of 25 patients previously treated with phenytoin, in whom alternative antiarrhythmic therapy was required, 40% had long-term arrhythmia control when treated with mexiletine. Mexiletine therapy was terminated for side effects in only five patients (12%). Mexiletine is recommended for young patients with congenital heart disease and serious ventricular arrhythmias.
Adolescent↗