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Biomedical subjects

J J Gallagher

Publications and source records attributed to J J Gallagher.

At least 163 records · Page 9Linked to original sources
PubMed1979

Reaction of the myocardium to cryosurgery: electrophysiology and arrhythmogenic potential.

The acute and chronic electrophysiological effects of a cryolesion produced in the left ventricle were studied in six dogs. All dogs had frequent ventricular premature beats (VPB) and five of six dogs had ventricular tachycardia during the first 4 days after the cryolesion; only one of the six dogs continued to have VPBs after 1 week, and this dog had identical VPBs before the creation of the cryolesion. Neither control dog had VPBs. Two additional dogs underwent epicardial and transmural mapping studies immediately after production of a cryolesion. VPBs in these animals were shown to originate at the border of the cryolesion. Epicardial activation sequence during normal sinus rhythm was not altered by the chronic cryolesion. The border zone of the chronic cryolesion was sharply demarcated with normal potentials recorded outside of the lesion and "extrinsic" potentials recorded within.

Animals↗
PubMed1979

Reentry within the atrioventricular node: surgical cure with preservation of atrioventricular conduction.

Paroxysmal supraventricular tachycardia (PSVT) is commonly caused by reentry within the atrioventricular (AV) node. This arrhythmia was abolished by operative dissection of the AV junction in a patient with disabling tachycardia that was not controlled by drugs. The operation was intended to create complete AV block, but AV conduction persisted after surgery. An electrophysiologic study 1 year after the operation revealed that the operation changed AV conduction in both the antegrade and retrograde directions, which may explain the absence of tachycardia. The patient has been free of arrhythmias for 18 months.

Atrioventricular Node↗
PubMed1979

Epicardial mapping of the onset of ventricular tachycardia initiated by programmed stimulation in the canine heart with chronic infarction.

The initial beats of ventricular tachycardia (VT) induced by programmed stimulation (PS) of the heart have frequently been observed to differ in QRS configuration from the subsequent uniform QRS complexes of tachycardia. The transient nature of these initial beats has made their study difficult during epicardial mapping with conventional, hand-held recording electrodes. Twenty-four dogs were studied with PS 1-10 months after coronary ligation. Twenty-six epicardial electrograms were recorded simultaneously during PS. The data were digitized for computer generation of isochronic maps for any desired beat. Three patterns of initiation were observed in episodes of tachycardia in which the initial beats differed from the subsequent beats of VT (11 of 18 runs of VT). Most frequently, the initial beats of VT originated near the pacing electrode before moving to a stable infarction zone location. Less frequently, the initial beats were due to transient reentry in the bundle branches or a transient shifting of early breakthrough sites in the infarction zone.

Animals↗
PubMed1979

Atypical patterns of retrograde conduction over accessory atrioventricular pathways in the Wolff-Parkinson-White syndrome.

Patterns of ventriculoatrial conduction have been used to distinguish retrograde conduction over an accessory atrioventricular pathway from that over the normal atrioventricular conduction system. Ventriculoatrial conduction at a constant interval during incremental ventricular pacing and during progressive prematurity of ventricular extrastimuli has been considered characteristic of conduction over an accessory pathway. We describe three patients with the Wolff-Parkinson-White syndrome who had progressive or sudden increments in ventriculoatrial conduction over an accessory pathway during fixed-rate ventricular pacing or during introduction of ventricular extrastimuli. Such properties have been considered characteristic of conduction over the normal atrioventricular conduction system. We conclude that retrograde conduction over accessory pathways may resemble conduction over the normal atrioventricular conduction system.

Adult↗
PubMed1979

Ventriculoatrial intervals: diagnostic use in paroxysmal supraventricular tachycardia.

Reciprocating tachycardias due to reentry either within the atrioventricular (AV) node or using an accessory AV pathway are a common cause of paroxysmal supraventricular tachycardia in humans. Unfortunately, although of potential therapeutic value, differentiation of these forms of reciprocating tachycardia may be difficult and require detailed electrophysiologic study. To develop diagnostic criteria that permit exclusion of participation of an accessory AV pathway in reciprocating tachycardia without extensive laboratory testing, results of electrophysiologic studies were examined in 50 patients with Wolff-Parkinson-White syndrome, 15 patients with accessory AV pathways that conducted only in the ventriculoatrial direction, and 15 patients with reentry within the AV node. The interval between onset of ventricular activation and both earliest recorded atrial activity (V-Amin) and high lateral right atrial electrogram (V-HRA) was measured during tachycardia. A V-Amin of 61 ms or less or V-HRA of 95 ms or less did not occur in patients with accessory AV pathways, but occurred frequently (12 of 15 and seven or eight, respectively) in patients with reentry within the AV node. Therefore, in patients with paroxysmal reciprocating tachycardias, V-A interval measurements provide a screening test capable of excluding participation of an accessory AV pathway.

Adolescent↗
PubMed1978

Surgical treatment of arrhythmias: current status and future directions.

A variety of surgical interventions have evolved for the treatment of intractable or life-threatening arrhythmias unresponsive to conventional pharmacologic or pacemaker therapy. Supraventricular arrhythmias associated with rapid ventricular responses can be indirectly treated with ablation of the atrioventricular conduction system and insertion of a pacemaker. Ventricular tachyarrhythmias have previously been treated with sympathectomy, resection of tissue or revascularization. More recent approaches include the simple ventriculotomy, encircling endocardial ventriculotomy, cryosurgical ablation and insertion of the automatic implantable defibrillator. Refinement of methods to localize more precisely the origin of ventricular arrhythmias may allow design of more direct surgical procedures. The surgical treatment of arrhythmias related to the preexcitation syndromes remains the model of electrophysiologic surgery. It is now feasible to divide accessory pathways with a high degree of success and at low risk in selected patients.

Arrhythmias, Cardiac↗
PubMed1978

Effect of catheter position on the initiation of atrial echoes with atrial pacing and premature stimulation in patients with accessory pathways.

Eleven patients with an accessory pathway and reciprocating tachycardia were studied using both fixed rate atrial pacing and the atrial extrastimulus technique. Six of the patients had an accessory pathway that conducted in both the anterograde and retrograde direction; but the effective refractory period of their accessory pathway in the anterograde direction was relatively long and was greater than the longest coupling intervals that initiated atrial echoes. Five patients had an accessory pathway that conducted only in the retrograde direction. The extrastimulus technique could be used with stimulation sites near to and remote from the accessory pathway in 10 of the 11 patients. Atrial echoes were initiated by a single atrial extrastimulus at both sites in 7 of the 10 patients, and in each patient the upper limit of the echo zone was longer with stimulation at the site near the accessory pathway. In the other three patients atrial echoes were initiated only during stimulation at the site near the accessory pathway because either atrial refractoriness or atrioventricular nodal refractoriness was encountered before the echo zone was entered during stimulation at the site remote from the accessory pathway. Differences in the longest cycle length that initiated an atrial echo during fixed rate atrial pacing were similarly demonstrated in three patients. In these three patients, pacing at the site near the accessory pathway initiated echoes at a longer cycle length than pacing at the site remote from the accessory pathway. In three other patients the electrophysiologic characteristics of atrioventricular conduction prevented a demonstration of these differences. Catheter position is an important variable in the initiation of atrial echoes in patients with accessory pathways.

Arrhythmias, Cardiac↗
PubMed1978

Cryoablation of drug-resistant ventricular tachycardia in a patient with a variant of scleroderma.

A 37-year-old man with a benign variant of scleroderma (CRST syndrome: calcinosis circumscripta, Raynaud's phenomenon, sclerodactyly, and telangiectasia) presented with recurrent ventricular tachycardia. Preoperative electrophysiologic study suggested that the mechanism of tachycardia was an ectopic pacemaker focus in the right ventricle. Right ventricular dilatation, tricuspid insufficiency, normal pulmonary pressures, and normal coronary arteries were also demonstrated. At surgery, epicardial mapping localized the site of origin of ventricular tachycardia to the anterior right ventricle near the crista supraventricular. Intramural recordings of the site of tachycardia demonstrated autonomous activity unreflected on the peripheral ECG during brief periods of sinus rhythm. Local epicardial cooling of this area with a cryoprobe promptly terminated ventricular tachycardia with resumption of tachycardia on warming. The focus was ablated by freezing the area at -60 degrees C. The patient remained free of dysrhythmia on no anti-arrhythmic agents for eight months at which time he had a single recurrence of ventricular tachycardia from a different site in the right ventricle. This technique offers a method for ablating sites of dysrhythmia arising in diffusely diseased myocardium.

Adult↗