Search PubMed⌕ Search

Biomedical subjects

R Yee

Publications and source records attributed to R Yee.

At least 163 records · Page 9Linked to original sources
PubMed1992

Feasibility of an implantable arrhythmia monitor.

Conventional Holter monitoring is of limited benefit in patients with infrequent symptoms suspected to be related to arrhythmia. A small recorder implanted subcutaneously might obviate many limitations of conventional monitoring. To determine the feasibility of obtaining adequate electrocardiographic signals from such a device, a prototype was temporarily implanted in 17 patients undergoing pacemaker implantation. The prototype contained four disc-shaped titanium electrodes, 0.21 inches in diameter embedded in epoxy. The four electrodes were in a square configuration spaced 0.72 inches center to center and were placed face down in a subcutaneous pocket in the left pectoral region. Bipolar recordings were made from a horizontal pair, a vertical pair, and both diagonal paris of electrodes (interelectrode distance 1.02 inches) and recorded on electromagnetic tape after filtering at 0.5-250 Hz. The mean peak-to-peak amplitude in each configuration was determined over a five-beat interval. Clear recordings were obtained from all 17 patients with recognizable P, QRS, and T waves. The amplitude of the signals obtained from the diagonal pairs of electrodes (175 +/- 51 and 170 +/- 54 microV) were greater than obtained from either the vertical pair (142 +/- 62 microV, P = 0.08 compared to diagonal electrodes) or the horizontal pair of electrodes (105 +/- 54 microV, P < 0.01). The maximum amplitude recorded from any configuration was 189 +/- 54 microV. In six patients the device was also tested with the electrodes face up in the subcutaneous pocket.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1992

Should a VVIR pacemaker increase the heart rate with standing?

To assess the usefulness of incorporating a posture sensor into a ventricular inhibited rate modulated pacemaker, the hemodynamic effects of increasing the ventricular pacing rate with standing were studied in 15 pacemaker dependent patients aged 55 +/- 3.5 years. In a randomized cross-over design, the pacing rate remained at 70 or was increased to 100 beats/min immediately prior to standing. Blood pressure was monitored continuously and forearm blood flow was measured by venous occlusion plethysmography. There was no difference in supine blood pressure (117 +/- 4/63 +/- 3 compared to 118 +/- 5/64 +/- 4 mmHg) or forearm blood flow (2.88 +/- 0.36 vs 2.94 +/- 0.32 mL/100 mL/min) before the 70 or 100 pacing rate intervention. With standing, blood pressure fell to an equivalent degree at the two pacing rates (fall in mean blood pressure at 70 beats/min 6 +/- 4 and at 100 beats/min 8 +/- 2 mmHg, P = 0.7). After 1 minute of standing differences in blood pressure were similar, but after 2.5 minutes of standing the increase in mean blood pressure was less at 70 than at 100 beats/min (increase from control 28 +/- 2 compared to 36 +/- 3 mmHg, P = 0.002). Forearm blood flow decreased after standing for 1 and 2.5 minutes but there was no difference between the 70 and 100 pacing rates (fall in forearm blood flow at 2.5 minutes 0.50 +/- 0.24 and 0.59 +/- 0.25 mL/100 mL/cm2).(ABSTRACT TRUNCATED AT 250 WORDS)

Heart Rate↗
PubMed1992

A permanent transvenous lead system for an implantable pacemaker cardioverter-defibrillator. Nonthoracotomy approach to implantation.

A transvenous lead system for implantable defibrillators would obviate a surgical thoracotomy and reduce the morbidity and mortality associated with implantation. We evaluated the clinical performance of a new nonthoracotomy lead system that included a defibrillation lead in the coronary sinus. At the time of defibrillator implantation, transvenous defibrillation leads were inserted percutaneously through the left subclavian vein into the right ventricular apex (RVA), superior vena cava (SVC), and distal coronary sinus (CS) under fluoroscopic guidance. A subcutaneous patch electrode (SQ) was also available if required. The first single- or dual-pathway electrode configuration that successfully terminated three of four ventricular fibrillation episodes using 18 J or less was implanted. Eleven men and three women aged 39-77 years (60.0 +/- 10.1 years) with left ventricular ejection fraction ranging from 16% to 63% (33.4 +/- 13.1%) were evaluated. Nine presented with ventricular tachycardia, three had ventricular fibrillation, and two had both. A totally transvenous lead system (RVA/CS/SVC) was implanted in seven patients (50%) with a mean defibrillation threshold of 15.6 +/- 2.9 J (10-18 J). Four patients received a partial transvenous lead system (RVA/CS/SQ). An effective nonthoracotomy lead system was not found in three patients; they received epicardial electrodes. After cumulative follow-up of 73 patient-months, nine patients remain alive and free of problems related to the implanted nonthoracotomy leads. One patient died of respiratory failure 3 months after defibrillator implant, and the leads from another patient were removed at 9 months because of bacterial infection. A transvenous lead system that includes a defibrillation lead in the coronary sinus is a safe, reliable, and, at least in the short term, effective nonthoracotomy approach for automatic defibrillator implantation.

Adult↗
PubMed1992

Syncope associated with supraventricular tachycardia. An expression of tachycardia rate or vasomotor response?

BACKGROUND: Syncope in patients with supraventricular tachycardia has been suggested to be an ominous finding, predictive of rapid rates during tachycardia. METHODS AND RESULTS: To explore the mechanism of syncope during supraventricular tachycardia, tachycardia was induced in the supine position and after passive head-up tilting to 60 degrees in 13 patients with atrioventricular (AV) node reentry, eight patients with AV reentry, and one patient with atrial tachycardia. Tilt testing was also performed in sinus rhythm for 30 minutes (the last 15 minutes with isoproterenol infusion). Mean +/- SEM age was 38 +/- 3 years, and 11 patients had a history of syncope (median number of syncopal episodes, three; range, one to 30). The cycle length of tachycardia when upright was shorter than when supine (297 +/- 9 compared with 357 +/- 10 msec, p less than 0.001), and mean blood pressure fell to a greater extent after the onset of tachycardia (fall in mean blood pressure, 53 +/- 6 compared with 24 +/- 3 mm Hg, p less than 0.001). Mean blood pressure correlated significantly with tachycardia cycle length when supine (r = 0.58, p = 0.005) but not when tilted upright (r = 0.18, p = 0.45). Syncope occurred in seven patients during upright tachycardia. These seven patients had a greater fall in mean blood pressure with upright tachycardia than the 15 patients without syncope (fall in mean blood pressure, 70 +/- 4 compared with 45 +/- 5 mm Hg, p = 0.01), but there was no difference in the tachycardia cycle length (311 +/- 10 compared with 290 +/- 11 msec, p = 0.29). Six of the seven patients with tachycardia-induced syncope also had syncope with tilt testing in sinus rhythm compared with four of the 15 patients without tachycardia-induced syncope (p = 0.02). CONCLUSIONS: These data support the view that syncope during supraventricular tachycardia is related to vasomotor factors and does not predict a more rapid tachycardia rate.

Adult↗
PubMed1992

Effect of atropine and isoproterenol on tachycardia induction in asymptomatic patients with Wolff-Parkinson-White electrocardiographic pattern.

OBJECTIVE: To determine if pharmacological interventions aimed at altering autonomic tone would allow induction of orthodromic atrioventricular reentrant tachycardia in asymptomatic patients with the Wolff-Parkinson-White electrocardiographic pattern. DESIGN: Prospective interventional protocol in consecutive eligible patients. SETTINGS: University hospital. PATIENTS: Eighteen asymptomatic patients (13 male and five female) with the Wolff-Parkinson-White electrocardiographic pattern without inducible tachycardia in the drug-free state. INTERVENTION: Electrophysiological assessment was performed at baseline, after intravenous administration of atropine (0.03 mg/kg) and during isoproterenol infusion (0.5 to 2 micrograms/min). RESULTS: Orthodromic reciprocating tachycardia was not inducible at baseline because of absent retrograde accessory pathway conduction in seven patients. In five patients, orthodromic atrial echo beats could be induced (which blocked retrogradely in the accessory pathway in three patients and anterogradely in the atrioventricular node in two). In the remaining six patients, neither orthodromic echo beats nor reciprocating tachycardia could be induced despite intact retrograde accessory pathway conduction. Following atropine administration (mean dose 1.9 +/- 0.3 mg), anterograde and retrograde accessory pathway effective refractory periods decreased from 360 +/- 172 to 284 +/- 62 ms and from 340 +/- 38 to 296 +/- 32 ms, respectively (both P < 0.05 versus control). Orthodromic reciprocating tachycardia was induced in two patients (nonsustained in one). During isoproterenol infusion (mean dose 1.0 +/- 0.3 micrograms/min), anterograde and retrograde accessory pathway effective refractory periods decreased further to 243 +/- 23 and 248 +/- 22 ms, respectively (both P < 0.05 versus after atropine); two further patients had inducible orthodromic reciprocating tachycardia (nonsustained in one). No patient with absent retrograde accessory pathway conduction developed retrograde accessory pathway conduction or reciprocating tachycardia with isoproterenol and/or atropine. CONCLUSIONS: Isoproterenol and/or atropine allowed tachycardia induction in four of 18 asymptomatic patients with the Wolff-Parkinson-White electrocardiographic pattern. In the majority of these patients, tachycardia is not inducible because of deficient retrograde accessory pathway conduction which does not improve with autonomic facilitation.

Adolescent↗
PubMed1992

Sudden cardiac death in the Wolff-Parkinson-White syndrome.

Sudden death in the Wolff-Parkinson-White syndrome is an uncommon event but strikes in otherwise healthy children or young adults, often without much warning. They tend to occur in symptomatic but have also been reported in asymptomatic individuals. Several studies have been done profiling the sudden death survivor in the Wolff-Parkinson-White syndrome. In general, they tend to be symptomatic, have a short RR interval between preexcited beats during atrial fibrillation, have multiple pathways and may be associated with familial occurrence and Ebstein's anomaly. Several noninvasive investigations can help to assess the risk for sudden death, but the gold standard remains the use of electrophysiological testing. The management of patients with documented ventricular fibrillation or resuscitation from sudden death is unquestionably ablation of the accessory pathway but for the asymptomatic patients, it is still controversial whether they should be routinely studied by electrophysiological studies.

Death, Sudden, Cardiac↗
PubMed1991

Surgery for supraventricular tachyarrhythmias.

Since the first successful surgical intervention for Wolff-Parkinson-White syndrome by W. C. Sealy, a surgical electrophysiological intervention has been developed for every single supraventricular arrhythmia. The surgical rationale is based on the site of the mechanism of the arrhythmia and associated pathology which characterizes the "arrhythmogenic substrate". Wolff-Parkinson-White syndrome is a congenital heart disease characterized by an accessory atrioventricular connection distinct from the AV node-His bundle system. It is associated with AV reentrant tachycardia and/or atrial fibrillation with fast ventricular responses via the accessory pathway. The current surgical management is ablation of the accessory pathway using either an endocardial dissection or epicardial approach. Surgical ablation is associated with high efficacy and low morbidity. Epicardial dissection of the accessory pathway on the beating heart has helped to localize variant accessory pathways associated with Coumel's tachycardia or Mahaim's fiber electrophysiological entity. AV nodal reentrant tachycardia can be cured using direct AV nodal dissection (or perinodal cryoablation). Atrial flutter can be interrupted by cryoablation of the arrhythmogenic substrate located in the coronary sinus orifice of the region modifying atrial inputs. Chronotropic atrial function abolished by chronic or paroxysmal idiopathic atrial fibrillation can be restored using the corridor operation (sinus node-AV node insulation). Surgery is an alternative in patients with resistant atrial tachycardias. Currently surgery is indicated only after other non-invasive EP interventions have been either attempted or rejected.

Atrial Fibrillation↗
PubMed1991

Radiofrequency catheter ablation of accessory pathways: a learning experience.

Success rates of approximately 90% have recently been reported with radiofrequency catheter ablation of accessory pathways. This study determined whether this success could be repeated using a conservative approach generally limiting fluoroscopy time to 1 hour. Consecutive patients referred for management of arrhythmias associated with accessory atrioventricular pathways were included over a 9-month period. Ablation was attempted in 75 patients with 84 pathways. Overall success rate (including second attempts in 9 patients) was 60 of 84 accessory pathways (71%). Success rates for the first 3 months (n = 23) were 52%, the second 3 months (n = 23) 60% and the last 3 months (n = 38) 90%. Success rate varied with pathway location, with left lateral pathways having the best early success rates. Mean fluoroscopy time for successful procedures of 33 +/- 21 minutes was shorter than the time for unsuccessful procedures of 63 +/- 24 minutes (p = 0.001). There were no major complications and no patients with successful procedures (n = 53) have had recurrence of accessory pathway conduction or reciprocating tachycardia (follow-up 1 to 10 months). A conservative approach can yield success rates approaching 90% in a short time. The absence of major complications supports earlier reports suggesting that radiofrequency catheter ablation of accessory pathways is a reasonable first-line therapy in the Wolff-Parkinson-White syndrome.

Adolescent↗
PubMed1991

Epicardial mapping in patients with "nodoventricular" accessory pathways.

Some patients with electrophysiologic features suggesting nodoventricular fibers have been shown to have right parietal atrioventricular (AV) accessory pathways with decremental conduction properties intraoperatively. The experience with 11 patients (7 women and 4 men, mean age +/- standard deviation 25 +/- 5 years) who had electrophysiologic features consistent with a nodoventricular pathway and who underwent operative correction was reviewed. At electrophysiologic study, all patients had absent or minimal preexcitation in sinus rhythm. During atrial pacing and extrastimulus testing, maximal preexcitation with left bundle branch block morphology developed and the AH and AV intervals progressively prolonged. Preexcited tachycardia was initiated in all patients (AV reentrant tachycardia in 10 patients and AV node reentrant tachycardia in 1 patient). At operation all patients had a right parietal accessory pathway demonstrated. Intraoperative mapping demonstrated the earliest site of ventricular activation during anterograde preexcitation to be at the midanterior right ventricle, consistent with insertion of these pathways into the right bundle branch system, in 7 patients. The ventricular insertion was at the AV groove in 4 patients, in keeping with the typical Wolff-Parkinson-White syndrome. Retrograde conduction over the pathway was not demonstrated in any patient. Two patients had evidence of a second accessory AV pathway in the left paraseptal region. Operative AV node ablation was electively performed in 2 patients without affecting preexcitation in either case. In 1 of these patients, accessory pathway conduction was temporarily abolished by ice mapping in the right anterolateral AV groove.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1991

Sinus node-atrioventricular node isolation: long-term results with the "corridor" operation for atrial fibrillation.

The "corridor" operation is designed to restore sinus rhythm to patients with atrial fibrillation by electrically isolating the sinus node, a band of atrial tissue and the atrioventricular (AV) node from the remaining atrial tissue. Nine patients with drug-refractory atrial fibrillation underwent this operation; four patients had chronic atrial fibrillation and five had paroxysmal atrial fibrillation; the mean duration of symptoms was 12 +/- 8 years. Patient ages ranged from 25 to 68 years (mean 48 +/- 12). At preoperative electrophysiologic study, no patient had evidence of an accessory AV pathway or AV node reentry. Sinus node recovery time could not be determined in five patients because of recurrent atrial fibrillation during or before programmed stimulation. At operation the corridor of atrial tissue connecting the sinus and AV nodes was successfully isolated from the remaining left and right atrial tissue in all patients. One patient required early reoperation for recurrent atrial fibrillation before hospital discharge. At the predischarge electrophysiologic study, the corridor remained isolated in all patients except for one patient who had intermittent conduction between the corridor and excluded right atrium. One patient had nonsustained atrial fibrillation and one had atrial tachycardia evident in the corridor. Atypical AV node reentry of uncertain significance was induced in one other patient. Over a total follow-up of 191 patient months (mean 21 +/- 20), seven patients remained free of atrial fibrillation. Two patients had recurrent atrial fibrillation, which in one patient was effectively controlled by a single antiarrhythmic agent. A permanent pacemaker was implanted in four patients for sinus node dysfunction.(ABSTRACT TRUNCATED AT 250 WORDS)

Arrhythmia, Sinus↗
PubMed1991

Characteristics of accessory pathways exhibiting decremental conduction.

The prevalence, electrophysiologic characteristics and functional significance of decremental conduction over an accessory pathway were examined in this retrospective study of 653 patients who had an accessory pathway demonstrated at electrophysiologic study. Decremental conduction was identified in 50 patients (7.6%). In 15 patients with anterograde decremental conduction, the accessory pathway was right parietal or septal in 14 patients and left parietal in 1 patient. In the 40 patients with retrograde decrement, the accessory pathway was left parietal in 19, posteroseptal in 13, right parietal in 2 and right anteroseptal in 6 patients. Anterograde conduction over the accessory pathway was absent in 11 of the 40 patients with retrograde decrement. Retrograde conduction over the accessory pathway was absent in 9 patients with anterograde decrement. There was no significant difference in the accessory pathway effective refractory period, or shortest cycle length with 1:1 conduction over the accessory pathway in anterograde and retrograde directions. The shortest RR interval in atrial fibrillation between 2 preexcited QRS complexes was longer in patients with anterograde decremental conduction than in a control group of patients with anterograde-conducting accessory pathways without decremental properties. These data demonstrate that decremental conduction over accessory pathways is uncommon. Anterograde decremental conduction usually occurs in right-sided or septal pathways that often do not conduct in the retrograde direction.

Adolescent↗
PubMed1991

Closed heart cryoablation of the His bundle using an anterior septal approach.

His bundle cryosurgical ablation using a closed heart anterior septal approach was used in 6 patients. There were 3 men and 3 women, aged 24 to 73 years. Three patients had atrial fibrillation and 2 patients had atrial flutter (2 with combined episodes of atrial tachycardia). One patient had atrial tachycardia. Five patients had no structural heart disease and 1 patient had left ventricular dilatation (ejection fraction, 0.35). All patients undergoing His bundle cryosurgical ablation had permanent heart block without intraoperative complications (mean follow-up, 25 months). Closed heart anteroseptal cryoablation of the His bundle is effective and is an alternative to attempted catheter ablation.

Adult↗
PubMed1991

Effects of lidocaine and verapamil on defibrillation in humans.

Patients with automatic defibrillators frequently require chronic antiarrhythmic drug therapy or receive acute therapy with the onset of symptoms. The effects on energy requirements for defibrillation of lidocaine hydrochloride and verapamil hydrochloride, two commonly used antiarrhythmic agents, were examined in 20 successive patients undergoing corrective arrhythmia surgery. The minimum energy requirement for ventricular defibrillation before and 5 minutes after the administration of 150 mg of lidocaine intravenously (n = 8), or 10 minutes after 10 mg of verapamil intravenously (n = 12), were determined. Each patient was assigned to receive either verapamil or lidocaine. Three mesh coil defibrillating electrodes (Medtronic 6891, 6892) were sutured to the epicardium of the right and left ventricles. Ventricular fibrillation was induced using alternating current. After a minimum of 10 seconds of fibrillation, the minimum energy for defibrillation was established using sequential pulse defibrillation. The preselected drug was then infused and the ventricular defibrillation energy was again determined after 5 or 10 minutes circulation time. Lidocaine did not alter the minimum energy for defibrillation (3.0 +/- 1.4 J vs. 3.0 +/- 1.8 J, mean +/- SD), despite plasma levels of lidocaine that averaged 13.2 +/- 1.9 mumol/l. In contrast, verapamil significantly increased (3.9 +/- 2.2 J vs. 6.5 +/- 2.9 J) the minimum energy necessary for defibrillation. The difference in defibrillation energy was significantly correlated to the fall in systolic blood pressure induced by verapamil administration (r = 0.72). These data reinforce the necessity for determining efficacy of defibrillation when medication changes are instituted. Verapamil should be used with caution in patients with automatic defibrillators and marginal defibrillation threshold.

Adult↗