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Biomedical subjects

R Yee

Publications and source records attributed to R Yee.

At least 253 records · Page 14Linked to original sources
PubMed1984

Surgical repair of Wolff-Parkinson-White syndrome: a new closed-heart technique.

The conventional operation for ablation of accessory pathways in Wolff-Parkinson-White (WPW) syndrome requires an endocardial approach and necessitates cardiopulmonary bypass and hypothermic cardiac arrest. Cryosurgical ablation of these pathways from the epicardial surface has been described but limited to superficial accessory pathways. We report a new closed-heart technique combining dissection of the atrioventricular (AV) pad and cryosurgery. Six patients with WPW syndrome underwent operation for ablation of accessory pathways associated with disabling tachyarrhythmia refractory to medical management. All pathways were located in the left lateral AV sulcus as determined by preoperative and intraoperative electrophysiological assessment. The heart was exposed through a median sternotomy. The AV fat pad and its vascular contents were dissected away from the atrium at the site of the pathway. A small segment of the ventricle adjacent to the sulcus was exposed. The fat pad was retracted to avoid cryoinjury to the coronary vessels. A cryoprobe, 1.5 cm in diameter, was applied to the exposed AV junction (-60 degrees C for 2 minutes) to create transmural fibrosis. After ablation of the pathway was verified, the chest was closed. All 6 patients have remained free from preexcitation during short-term follow-up. This simplified technique is applicable to patients with free wall accessory pathways. This group constitutes the majority of symptomatic patients with WPW syndrome at our institution.

Adolescent↗
PubMed1984

Refractory paroxysmal sinus tachycardia: management by subtotal right atrial exclusion.

A 27 year old woman presented with recurrent episodes of disabling paroxysmal sinus tachycardia (150 to 180 beats/min) in the absence of identifiable organic disease. Tachycardia was resistant to all drug therapy. Programmed stimulation could not induce the tachycardia but high dose propranolol therapy failed to suppress sinus tachycardia in response to isoproterenol infusion. Because of the disability resulting from refractory tachycardia, the patient underwent a new operative procedure to create exit block around the region of abnormal impulse formation. This resulted in the appearance of a stable junctional escape rhythm at 60 beats/min. No adverse effects occurred and the patient has remained free of symptoms after a follow-up period of 10 months.

Adrenergic beta-Antagonists↗
PubMed1984

Surgical correction of the Wolff-Parkinson-White syndrome in the closed heart using cryosurgery: a simplified approach.

The conventional operation for ablation of accessory atrioventricular (AV) pathways in the Wolff-Parkinson-White syndrome requires an endocardial approach to the AV groove and necessitates the use of cardiopulmonary bypass and induced cardiac arrest. The feasibility of creating transmural atrial fibrosis at the level of the AV anulus in the closed heart in dogs without damaging the vascular contents of the AV fat pad was demonstrated. This was done by dissecting the fat pad from the atrium and applying a cryoprobe to the exposed atrial-anular region after retraction of the fat pad. The technique was then applied to successfully ablate 12 left parietal wall accessory pathways in 11 patients with the Wolff-Parkinson-White syndrome. This simplified approach to any parietal wall accessory pathway does not require cardiopulmonary bypass or induced cardiac arrest and may broaden the indications for this operation.

Adolescent↗
PubMed1984

Changes in pacing threshold and R wave amplitude after transvenous catheter countershock.

Transvenous electrode catheter countershock in patients with recurrent ventricular tachyarrhythmias may be followed by transient bradycardia and require temporary pacing with a catheter. The serial changes in R wave amplitude and stimulation threshold after catheter countershock in 11 halothane-anesthetized open chest dogs ranging in weight from 11.8 to 24 kg were studied. Ventricular fibrillation was electrically induced and followed by catheter defibrillation using nonsynchronized trapezoidal waveform (65% tilt) current discharge in incremental doses (5 to 50 J). Significant decreases in bipolar R wave amplitude (8.3 +/- 1 versus 2 +/- 0.2 mV, p less than 0.001) and increases in stimulation threshold (1 +/- 0.1 versus 2.3 +/- 0.4 V, p less than 0.001) were observed using the countershock catheter 15 seconds after countershock; these changes persisted for up to 10 minutes. To determine whether these changes were localized to the defibrillating catheter and whether they were species-specific, a second electrode catheter was positioned in the right ventricle distant from the countershock catheter in five pigs. Increases in stimulation threshold were observed only at the countershock catheter, suggesting that changes were secondary to local changes at the catheter-myocardium interface. No significant change in R wave amplitude or stimulation threshold was observed at the countershock catheter in three pigs given transthoracic shocks (60 to 250 J). It is concluded that current discharge through the countershock catheter results in a significant temporary reduction in R wave amplitude and an increase in pacing threshold. This may make pacing through the countershock catheter unreliable after shock delivery.

Animals↗
PubMed1984

Comparative functional effects of chronic ventricular demand and atrial synchronous ventricular inhibited pacing.

We compared the effects of chronic ventricular inhibited (VVI) and atrial synchronous ventricular inhibited (VDD) pacing on functional capacity in 8 patients with complete atrioventricular heart block. Permanent VDD (Medtronic #2409, ASVIP) pacemakers were implanted in four men and four women (age range 27-76 years, mean 58.9 +/- 18.4 years), and randomly assigned to a three-month period of VDD or VVI pacing in this single blinded, crossover study. Functional capacity was assessed by questionnaire, graded treadmill exercise testing and radionuclide angiocardiography prior to pacemaker implant and following each pacing period. Following 3 months of pacing in each of VVI and VDD pacing modes, maximum heart rate (83.4 +/- 14 vs 134.9 +/- 16.4 beats/min, p less than 0.001) and double product (147.5 +/- 58.3 vs 218.9 +/- 52.7, p less than .001) were greater with VDD pacing. Although exercise duration on treadmill exercise testing (5.3 +/- 2.9 vs 6.9 +/- 3.1 minutes, p less than 0.1) was greater in the VDD mode, the difference was not significant. Similarly, there was no significant difference in functional capacity as measured by questionnaire scores (50.1 +/- 8.4 vs 46.9 +/- 8.9, p less than 0.1) or in left ventricular ejection fraction for the two pacing modes (.54 vs .55, p less than .5). Only one patient reported a subjective improvement with physiologic (VDD) pacing, whereas the remaining patients stated no preference. We conclude that VDD pacing offers improved maximal cardiac work during exercise compared to VVI pacing.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1984

Wide QRS tachycardia: multiple mechanisms in a patient after myocardial infarction.

A 34-year-old man was hospitalized for extensive antero-apical myocardial infarction. Eight weeks after discharge from the hospital, he had intermittent rapid palpitations. During several episodes, a rapid, regular, wide-QRS-complex tachycardia with left bundle branch (LBB) morphology was recorded. All antiarrhythmic agents administered to the patient were unsuccessful in alleviating his symptoms, which were thought to be due to supraventricular tachycardia (SVT) with aberration. An electrophysiologic study was performed and revealed three morphologically distinct types of wide complex tachyarrhythmias: 1) Tachycardia 1 was determined to be A-V re-entry with antegrade conduction utilizing the normal A-V conducting system and retrograde conduction over a concealed accessory pathway located in the left A-V groove; 2) tachycardia 2 was identified as ventricular tachycardia (VT); and 3) tachycardia 3 was considered to be a second morphologic type of ventricular tachycardia as the morphology was identical to some of the episodes documented clinically. The patient was treated with oral amiodarone which was unsuccessful until combined with quinidine; this regimen has suppressed recurrence of VT during a four-month period of follow-up. The occurrence of wide-QRS-complex tachycardia in this patient immediately suggested the diagnosis of VT, but our other findings were unexpected. This case illustrates the need for considering all possible mechanisms when seeking to manage tachyarrhythmias, even if the diagnosis appears obvious.

Adult↗
PubMed1984

Syncope in the Wolff-Parkinson-White syndrome: incidence and electrophysiologic correlates.

Syncope in the patient with Wolff-Parkinson-White (WPW) syndrome raises the specter of rapid tachyarrhythmias and the possibility of sudden cardiac death. We reviewed the records of 55 consecutive WPW patients referred for electrophysiologic evaluation of known or suspected arrhythmias to determine the incidence and significance of syncope. Twelve patients (22.6%) reported the occurrence of at least one episode of syncope. In eleven (20%) of these, syncope was preceded by rapid palpitations. Forty-three patients (77.4%) had no syncopal episodes. These two groups did not differ significantly with regard to age, sex, presence of associated cardiac or neurologic disease, drug history or accessory pathway location. There was no significant difference in cycle length of reciprocating tachycardia (syncope = 295.6 +/- 59.8 vs non-syncope = 334.5 +/- 59.6 ms, p less than .5), shortest R-R intervals between preexcited beats (260 +/- 78.6 vs 246.7 +/- 55.4 ms, p less than .5) and average R-R interval (364.4 +/- 37.9 vs 367.4 +/- 77.5 ms, p less than .5) measured during atrial fibrillation. The anterograde effective refractory period of the accessory pathway (292.1 +/- 31.9 vs 299 +/- 58.1 ms, p less than .5) and the shortest cycle length with 1:1 conduction over the accessory pathway (306.7 +/- 75 vs 289.1 +/- 77.5 ms, p less than .5) similarly did not differ. We conclude that syncope occurs in approximately 20% of patients with the Wolff-Parkinson-White syndrome referred for assessment of tachycardia. Patients with syncope do not have distinct clinical features or a more malignant electrophysiologic profile, suggesting that other extracardiac factors may play an important role in the genesis of syncope in this group.

Adolescent↗
PubMed1984

Recurrent ventricular tachycardia responsive to verapamil.

We describe five young patients with recurrent ventricular tachycardia in the absence of organic heart disease. In all patients tachycardia could be terminated or prevented with verapamil. Tachycardia in four patients was very similar, with a QRS pattern of right bundle branch block and left axis deviation. Electrophysiology studies in two patients showed that VT was inducible in one patient (rapid atrial or ventricular pacing, ventricular extrastimuli) but not in the other. The clinical and electrocardiographic similarities in these patients suggest that their ventricular tachycardias may share a common pathophysiology and may be dependent on slow channel activity.

Adolescent↗
PubMed1984

Concealed conduction in accessory atrioventricular pathways: an important determinant of the expression of arrhythmias in patients with Wolff-Parkinson-White syndrome.

Concealed conduction into accessory atrioventricular pathways has been postulated to explain variability of R-R intervals during atrial fibrillation in patients with Wolff-Parkinson-White syndrome. We examined the occurrence of concealed conduction into atrioventricular pathways using extrastimulus techniques in 26 consecutive patients undergoing electrophysiologic studies for the Wolff-Parkinson-White syndrome. Anterograde pathway concealment was demonstrated (10 patients) by introducing a second atrial extrastimulus (A3) after block in the accessory pathway occurred following the first extrastimulus (A2). The apparent effective refractory period (ERP) of the atrioventricular pathway with A3 (after A2 blocked in the pathway), or ERPB, was always greater than the ERP of the atrioventricular pathway (505 +/- 100 vs 323 +/- 105 msec, mean +/- SD; p less than .001), a finding explained by concealment into the pathway by the blocked A2. A measure of the apparent prolongation of refractoriness due to anterograde concealment (delta ERPB), defined as the difference between ERP and ERPB at a given cycle length, was derived. The average R-R interval in atrial fibrillation correlated better with delta ERPB (r = .8, p less than .01) than with the ERP (r = .6, p = NS), supporting the influence of anterograde atrioventricular pathway concealment in modulating the ventricular response during atrial fibrillation. By similar techniques, concealed retrograde conduction in the atrioventricular pathway could be demonstrated in 16 of 26 patients. In two of these patients "bystander" atrioventricular pathway conduction during orthodromic reciprocating tachycardia that did not involve the atrioventricular pathway did not occur, even though the ERP of the pathway should have permitted it, a finding readily explained by repetitive retrograde concealment into the atrioventricular pathway during tachycardia. Concealed conduction can be demonstrated in most patients with Wolff-Parkinson-White syndrome and is an important factor in the clinical expression of their arrhythmias.

Adolescent↗
PubMed1984

[Surgical section of the bundle of Kent in the closed heart].

The conventional operation for ablation of accessory pathways (AP) in the WPW syndrome requires an endocardial approach and necessitates cardiopulmonary bypass and hypothermic cardiac arrest. Cryosurgical ablation of AP from the epicardial surface has been described but was limited to superficial AP. We report a new closed-heart technique combining dissection of AV pad and cryosurgery. Eight patients with WPW syndrome, aged 6-56, underwent surgery for ablation of AP associated with disabling tachyarrhythmia refractory to medical management. All AP were located in the left lateral AV sulcus as determined by preoperative and intraoperative electrophysiological assessment. The heart was exposed through a median sternotomy. The AV fat pad and its vascular contents were dissected away from the atrium at the site of the AP, sacrificing some atrial vessels. The dissection left some fat adherent to the thin-walled atrium close to the level of the mitral annulus. A small segment of the ventricle adjacent to the sulcus was exposed. The fat pad was retracted to avoid cryo-injury to the coronary vessels. A cryoprobe (1.5 cm diameter) was applied to the exposed AV junction (-60 degrees C for 2 minutes) to create transmural fibrosis. After verification of AP ablation, the chest was closed. All 8 patients have remained free of preexcitation during short term follow-up (1 to 8 months). This simplified technique is applicable to patients with free-wall AP, a group constituting the majority of symptomatic WPW patients at our institution.

Adult↗
PubMed1982

Low energy countershock using an intravascular catheter in an acute cardiac care setting.

We examined the feasibility, effectiveness, and safety of using an intravascular catheter positioned in the right ventricular apex for countershock in a coronary care unit setting in 8 patients who had recurrent ventricular tachyarrhythmia. Countershock using 2.5 to 40 J stored energy (damped sinusoidal wave form) was attempted 115 times to terminate 100 episodes of ventricular tachyarrhythmia (ventricular tachycardia, 91; ventricular flutter, 3; ventricular fibrillation, 6). Eighty-six (87%) of 99 countershock attempts for ventricular tachycardia, 3 (60%) of 5 for ventricular flutter, and 4 (36%) of 11 for ventricular fibrillation were successful using this technique. The catheters remained in stable position for 1 to 16 days without dislodgment. A majority of the countershocks were delivered by the regular nursing staff in the coronary unit. We conclude that low energy countershock through an intravascular catheter system is feasible, safe, and effective in a coronary care unit setting. Such a system should be beneficial in the acute management of patients who have recurrent ventricular tachycardia or fibrillation. The catheter lead may also prove useful in managing ventricular tachyarrhythmias that occur during electrophysiologic studies.

Adult↗