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Biomedical subjects

G J Klein

Publications and source records attributed to G J Klein.

At least 145 records · Page 8Linked to original sources
PubMed1992

Differential effect of intravenous procainamide on anterograde and retrograde accessory pathway refractoriness.

Although procainamide may markedly impair or abolish anterograde conduction over an accessory atrioventricular (AV) pathway, orthodromic AV reentry may remain inducible. This difference may be related to a systemic differential effect of procainamide on anterograde and retrograde accessory pathway refractoriness. To examine this phenomenon, an infusion of procainamide producing five incremental blood levels over 75 min was administered to 15 patients with the Wolff-Parkinson-White syndrome. At each procainamide level, accessory pathway effective refractory period and accessory pathway block cycle length were determined in the anterograde and retrograde directions. At baseline, there were no significant differences between anterograde and retrograde accessory pathway effective refractory periods (282 +/- 7 vs. 266 +/- 9 ms, p = 0.08) and block cycle lengths (288 +/- 15 vs. 283 +/- 9 ms, p = 0.66). The concentration of procainamide resulting in 50% prolongation of accessory pathway refractoriness was less in the anterograde direction than in the retrograde direction (27.5 [log concentration -4.56 +/- SE 0.13] vs. 64.6 [-4.19 +/- 0.11] mumol/liter, p = 0.02). Similarly, the concentration of procainamide resulting in 50% prolongation of accessory pathway block cycle length in the anterograde direction (25.1 [-4.60 +/- 0.13] mumol/liter) was less than in the retrograde direction (52.5 [-4.28 +/- 0.07] mumol/liter, p = 0.01). The probability of persistence of accessory pathway conduction in the anterograde direction was less than in the retrograde direction by Kaplan-Meier analysis (p = 0.04).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1992

Electrophysiologic substrate associated with pacing-induced heart failure in dogs: potential value of programmed stimulation in predicting sudden death.

To investigate the possible mechanisms of sudden death and the potential role of electrophysiologic testing in congestive heart failure, this study evaluated the electrophysiologic substrate in a model of heart failure induced by rapid pacing. Seventeen mongrel dogs underwent cardiac pacing at 220 to 240 beats/min for 5 weeks (paced group) and 11 other dogs served as a sham-operated control group. Rapid pacing of the right ventricle produced clinical and hemodynamic features of congestive heart failure. Dogs in the paced group had prolonged cardiac conduction time as reflected by longer epicardial activation time (36.1 +/- 2.4 vs. 30.8 +/- 0.8 ms, p less than 0.05). The ventricular effective refractory period was significantly prolonged after the development of heart failure (141 +/- 4 vs. 177 +/- 5 ms, p less than 0.01, at a basic pacing cycle length of 300 ms), whereas no significant change was found in the control group (140 +/- 4 vs. 145 +/- 4 ms, p = NS). The prolongation of the ventricular effective refractory period correlated with an increase in left ventricular end-diastolic pressure (r = 0.55, p less than 0.001) and the ventricular effective refractory period correlated inversely with cardiac index (r = -0.49, p less than 0.025). The rest membrane potential of ventricular muscle was less negative in the paced group compared with the control group (-80.7 +/- 2.2 vs. -85.6 +/- 2.2 mV, p less than 0.05). Intracellularly recorded action potential duration of ventricular muscle was longer in the paced than in the control group (236 +/- 9.8 vs. 198.9 +/- 2.6 ms, p less than 0.01), action potential duration at 90% repolarization).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

A unique preexcitation pattern related to an atypical anteroseptal accessory pathway.

Accessory atrioventricular pathways have traditionally been classified by anatomical location to four areas, namely anteroseptal, posteroseptal, and right and left free walls. Each of these have been associated with a relatively distinct preexicitation pattern electrocardiographically. We describe a patient with a unique ECG pattern suggesting preexicitation to the right ventricular outflow region. Preoperative and intraoperative electrophysiological testing confirmed the presence of an accessory pathway with an atrial insertion site near the His bundle, decremental anterograde conduction, and a ventricular insertion site in the upper part of the interventricular septum. Operative ablation near the atrial insertion site eliminated preexicitation.

Adult↗
PubMed1992

Effects of defibrillation shocks delivered directly over a major coronary artery.

This study investigated the influence of defibrillator shocks delivered directly over a coronary artery, independent of ventricular fibrillation, on cardiac hemodynamics. Thirty-six open chest, halothane anesthetized pigs were randomized to receive six shocks at one of 5.0, 7.5, or 10.0 joules (J). Shocks were delivered between two mesh electrodes (Medtronic TX-7) sutured onto the epicardium, one over the left anterior descending coronary artery and the second directly opposite on the posterobasal ventricular surface. Shock delivery was synchronized to the R wave of the cardiac cycle, to reduce the risk of inducing fibrillation, with a 5-minute stabilization period between successive shocks. Pressure from the left ventricle, the left anterior descending coronary artery, distal to the mesh electrode and the left circumflex (control) artery and contractility in the regions perfused by both arteries were measured. The shocks invariably produced an immediate (2-second postshock), but transient, depression in systolic pressure of the same magnitude for the left anterior descending coronary artery, circumflex artery and the left ventricle that recovered by 5-minute postshock. There was no dose dependent relationship to energy. Also there was no clear difference in myocardial wall motion between the area perfused by the left anterior descending coronary artery and that perfused by the circumflex artery. These results suggest that shocks up to 10 J delivered over an epicardial artery do not cause arterial spasm and do not compromise coronary artery blood flow.

Animals↗
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

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

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↗
PubMed1991

Predictive accuracy of electrophysiologic localization of accessory pathways.

Operative ablation of accessory pathways depends critically on preoperative localization when technical limitations preclude complete intraoperative mapping. To assess the accuracy of localization, 345 patients undergoing operative ablation were studied; 316 (91.6%) had a single accessory pathway and 29 (8.4%) had multiple accessory pathways. The electrophysiologic study was diagnostically complete and accurate in 294 patients (93%) with a single accessory pathway and 19 (61%) with multiple accessory pathways. A left lateral accessory pathway was most accurately localized with excellent sensitivity (99%) and positive predictive value (98.5%). Diagnostic errors occurred in 33 patients because of 1) incorrect localization (n = 16), 2) failure to detect a second pathway (n = 9), and 3) diagnosis of a second pathway not verified intraoperatively (n = 8). Multiple pathways were more prevalent in the group with errors (33.3% vs. 5.8%, p = 0.0001), as were unidirectional pathways (48.5% vs. 24.3%, p = 0.003). It is concluded that preoperative localization of accessory pathways is sufficiently accurate to allow intraoperative mapping to be brief and focused.

Adult↗