Alex Zinner

Treatment of atrial automatic tachycardia by ablation procedures

Sixteen cases of atrial focus tachycardia are described clinically, electrophysiologically and hemodynamically. In each case multiple attempts at drug treatment (average 2.5 drugs) had failed. After delineation of the electrophysiologic mechanism, the patients were treated by surgical removal or cryoablation or catheter electroablation of the focus. In two of four patients catheter ablation was successful and without complication. Surgical treatment was successful in 13 of 14 patients. Left ventricular function, which had been abnormal in 10 patients, normalized in all but 1 patient whose echocardiographic shortening fraction improved from 10 to 27%. There have been no recurrences in a follow-up period of 6 months to 5 years (mean 2.2 years). It is recommended that any atrial automatic focus tachycardia that produces hemodynamic compromise undergo definitive treatment. Patients with chronic tachycardia rates of more than 140 beats/min should be followed up closely.

Junctional automatic ectopic tachycardia: New proposed treatment by transcatheter His bundle ablation☆

Three infants with junctional automatic ectopic tachycardia (JET) were seen over an 8-month period. Each had decreased left ventricular function. Two were treated with amiodarone, which together with propranolol reduced the tachycardia rate 10 to 40 bpm, but did not result in sinus rhythm. One patient died suddenly at home, as had 50% of our patients with JET treated with conventional medication. Two patients were treated by transcatheter ablation of the bundle of His and implantation of an atrial synchronous pacemaker. Neither has had subsequent tachycardia or required drugs. One patient resumed sinus rhythm and does not use his pacemaker. The other patient has complete AV block and continues to use her pacemaker. This aggressive approach to this lethal dysrhythmia offers hope for prevention of the former bad prognosis.

Surgical treatment of supraventricular tachycardia in infants and children

The technique, indications and results of surgical division of accessory atrioventricular connections in 10 infants and children with drug-resistant supraventricular tachycardia are described. The patients ranged in age from 6 months to 15 years. Four patients had associated congenital heart disease. Division of accessory connections were performed on free wall pathways in nine patients (seven right atrial, two left atrial) and on a septal pathway in one patient. Four patients had both anterograde and retrograde conduction over the accessory connection (manifest Wolff-Parkinson-White conduction) whereas six had only retrograde conduction (concealed Wolff-Parkinson-White conduction). The manifst Wolff-Parkinson-White conduction was abolished by surgical division in all four patients. In 8 of the 10 patients the procedure stopped the attacks of paroxysmal supraventricular tachycardia for follow-up periods ranging from 9 months to 3 1/2 years; no patient receives medication to date.

Decrease in canine endocardial and epicardial electrogram voltages with exercise: implications for pacemaker sensing.

Individuals with permanently implanted pacemakers who have normal sensing and pacing at rest may demonstrate abnormalities, particularly of atrial sensing, with exercise. Exercise is known to cause changes in the surface electrocardiographic voltages. The purpose of this study was to evaluate changes in endocardial and epicardial voltages during exercise in canines with permanently implanted pacing leads similar to those permanently implanted in humans with pacemakers. Six adult mongrel dogs were equipped with transvenous atrial and ventricular endocardial bipolar screw‐in leads from a jugular venosection, and with atrial and ventricular bipolar stab‐on leads from a left thoracotomy. Exercise was performed at one week following implantation and at weekly intervals for a total of 4 weeks. The animals were studied at rest and at a single workload of 3 miles per hour at a 30% elevation. Unfiltered electrograms were recorded with a VR‐12 Electronics‐for‐Medicine photographic recorder. The mean decreases of electrograms with exercise from resting voltage were: 15% for atrial endocardial unipolar leads: 11% for atrial endocardial bipolar leads; 4% for atrial epicardial unipolar leads; 15% for atrial epicardial bipolar leads; 8% for ventricular endocardial unipolar leads; 18% for ventricular endocardial bipolar leads; 0.1% for ventricular epicardial unipolar leads and 5% for ventricular epicardial bipolar leads.

Chronic epicardial his bundle recordings in awake nonsedated dogs: A new method

Recording cardiac electrical potentials from the region of the bundle of His in the awake, nonsedated animal would allow a more physiologic evaluation of impulse transmission through the specialized atrioventricular conduction system than anesthetized preparations. We present a new technique to localize and record chronic His bundle potentials using standard electronic equipment which obviates the need for intravascular catheters or an atriotomy. Six mature and four immature mongrel dogs underwent a midline thoracotomy. The bundle of His electrogram was recorded from the right atrial epicardium alongside the noncoronary aortic cusp. A flexible tripolar electrode probe with 3 mm interelectrode distance attached to a standard electronic recorder was used to localize the area of greatest His bundle impulse. Silver solder electrodes were sutured to the designated area and the wires were externalized to the back. Electrophysiological measurements were made 1 to 20 weeks later to confirm the accuracy and stability of the His bundle electrogram. These recordings were comparable to the standard internal catheter measurements both before and during atrioventricular impulse interference caused by atrial pacing or pharmacologic intervention. Electrodes sutured to the designated area do not interfere with impulse conduction and allow stable His bundle recordings in all activity ranges in the chronic animal.

Atrial tracking (synchronous) pacing in a pediatric and young adult population

One hundred pediatric and young adult patients underwent implantation of an atrial tracking pacemaker. Seventy-four pacemakers paced in an atrioventricular (AV) sequential mode at the lower rate limit (DDD) while 26 paced in a ventricular demand mode at the lower rate limit (VDD). Five patients required reoperation during follow-up of 1 month to 2.5 years (mean 1.5 years). Six additional patients required programming to ventricular demand (3) or AV sequential (3) pacing, because of development of sinus bradycardia (2), atrial sensing problems (1) or pacemaker-mediated tachycardia (3). Pulse generators that could sense atrial signals less than 1.0 mV and had a programmable atrial refractory period did not require reprogramming out of the atrial tracking mode. No patient developed atrial flutter or fibrillation. Sensing problems during exercise occurred in 37% of the first 60 pacemakers but in none of the last 40, which had improved electronic components. Atrial tracking pacing is feasible in pediatric and young adult patients.

Automated On‐Line Measurement of Electrophysiologic Intervals During Cardiac Catheterization

A small dedicated, computer‐controlled waveform analyzer was used to automatically measure the R‐R cycle length, low right atrium to His, and His to ventricle intervals obtained during electrophysiologic studies on 35 patients. These measurements were compared to intervals handmeasured separately and found to correlate well (0.92, 0.63, and 0.75, respectively). The sources of error, possible pitfalls, and future uses of this technique are discussed.

The Incidence of Retrograde Conduction in Children

With the increasing use of “physiological” Pacemakers in the pediatric age group, retrograde conduction in children has become of clinical importance. Pacemaker which sense atrial depolarization may sense “retrograde” P waves. The pacemaker may then act as the antegrade limb of a reciprocating tachycardia circuit. While the patients own conduction system act the retrograde limb. We reviewed the data of 127 patients who underwent antegrade and retrograde electrophysiologic study at Taxes Childrens Hospital, with regard A‐V node; the incidence of retrograde conduction in patients after surgical correction of a tetralogy of Fallot was singnificantly lower (33%). None of the patients with third degree A‐V block had retrograde conduction. The mean retrograde conduction time was 162 ms (range 70‐335 ms) at the slowest pacing rate and 257 ms (range 80‐475 ms) at the fastest pacing rate. This high incidence of retrograde conduction and the variability of conduction times must be taken into when “physiological” pacemaker are to be implanted.

Comparative electrophysiologic effects of digoxin in the nonsedated chronically instrumented puppy

The electrophysiologic effects of acute but not chronic administration of cardiac glycosides have been studied. Nineteen chronically instrumented beagle puppies underwent 2-week courses of parenteral digoxin in three dosage regimens: six received digoxin, 0.04 mg/kg/day; seven received 0.03 mg/kg/day; and 11 received 0.02 mg/kg/day. Mean serum concentrations were 3.2 ng/ml, 1.3 ng/ml, and 1.0 ng/ml, respectively. Significant electrophysiologic effects on sinus node function were produced only by the highest dose. Atrioventricular node conduction was significantly delayed among animals receiving both high and middle dosages. All three regimens significantly effected atrioventricular specialized conduction system functional refractory periods. Atropine decreased digoxin-induced effects on all measured parameters but totally eliminated the digoxin effect on the corrected sinus node recovery time.