Search PubMed⌕ Search

Biomedical subjects

K G Lurie

Publications and source records attributed to K G Lurie.

At least 19 recordsLinked to original sources
PubMed1999

Evaluation of left ventricular based pacing in patients with congestive heart failure and atrial fibrillation.

Acute hemodynamic data of left ventricular based pacing were assessed in 2 groups of patients with severe cardiac failure: 11 patients with atrial fibrillation and 17 patients with sinus rhythm. Both biventricular and left ventricular pacing significantly improved acute hemodynamic findings to a similar degree in both groups, suggesting that left ventricular based pacing may be beneficial in patients with severe cardiac failure regardless of whether or not they are in sinus rhythm.

Aged↗
PubMed1999

Resumption of motor vehicle operation in vasovagal fainters.

This study surveyed current practice patterns with respect to the manner by which cardiac arrhythmia specialists advise patients with vasovagal syncope regarding resumption of motor vehicle operation. Among 66 physician-respondents from 9 countries, 98% indicated that they rely on tilt-table testing to establish a diagnosis, and, if an effective treatment is found based on serial tilt-table testing, they recommend a 6- to 7-week symptom-free waiting period before advising return to driving.

Attitude of Health Personnel↗
PubMed1999

Prehospital discharge defibrillation testing in ICD recipients: a prospective study based on cost analysis.

Prehospital discharge defibrillation testing is often performed to verify the function of newly implanted cardioverter defibrillators (ICDs). To determine whether elimination of predischarge testing could reduce costs without placing patients at additional risk, 31 patients were randomized in this prospective clinical evaluation to either receive or not receive a predischarge ICD defibrillation test. Expenses associated with postimplant care was the primary endpoint. All patients underwent induction of ventricular fibrillation after 6 months to evaluate ICD function. The groups were well matched in terms of patient characteristics, initial lead implant parameters, and defibrillation thresholds. Elimination of prehospital discharge testing resulted in a savings of $1,800/patient after 6 months, with no difference between groups in terms of ICD complication rates or unanticipated hospital admissions. Further studies are needed to better define the most appropriate time to assess defibrillation thresholds in the first year after implantation.

Aged↗
PubMed1999

"Sagging heart syndrome": a cause of acute lead dislodgment in two patients.

Acute passive fixation atrial lead dislodgment occurred due to an unexpected and marked postural descent of the heart after permanent pacemaker implantation in two patients. Sagging of the heart in these two individuals may have been related to a history of morbid obesity followed by weight loss of over 100 pounds. Lead replacement with active fixation leads was required in both cases. The term "sagging heart syndrome" is proposed to describe this clinical entity. In certain adult populations, such as in patients with a history of significant weight loss, the "sagging heart syndrome" may represent a previously unrecognized cause of acute lead dislodgment.

Electrodes, Implanted↗
PubMed1999

Modulation of AV nodal and Hisian conduction by changes in extracellular space.

Previous studies have demonstrated that the extracellular space (ECS) component of the atrioventricular (AV) node and His bundle region is larger than the ECS in adjacent contractile myocardium. The potential physiological significance of this observation was examined in a canine blood-perfused AV nodal preparation. Mannitol, an ECS osmotic expander, was infused directly into either the AV node or His bundle region. This resulted in a significant dose-dependent increase in the AV nodal or His-ventricular conduction time and in the AV nodal effective refractory period. Mannitol infusion eventually resulted in Wenckebach block (n = 6), which reversed with mannitol washout. The ratio of AV nodal to left ventricular ECS in tissue frozen immediately on the development of heart block (n = 8) was significantly higher in the region of block (4.53 +/- 0.61) compared with that in control preparations (2.23 +/- 0.35, n = 6, P < 0.01) and donor dog hearts (2.45 +/- 0.18, n = 11, P < 0.01) not exposed to mannitol. With lower mannitol rates (10% of total blood flow), AV nodal conduction times increased by 5-10% and the AV node became supersensitive to adenosine, acetylcholine, and carbachol, but not to norepinephrine. We conclude that mannitol-induced changes in AV node and His bundle ECS markedly alter conduction system electrophysiology and the sensitivity of conductive tissues to purinergic and cholinergic agonists.

Acetylcholine↗
PubMed1998

Usefulness of pindolol in neurocardiogenic syncope.

We prospectively studied the efficacy of pindolol, a beta-adrenergic blocker with intrinsic sympathomimetic activity (ISA), for the prevention of syncope recurrences in 31 patients with recurrent neurocardiogenic syncope. Pindolol proved to be an effective treatment, even in patients who had previously failed treatment with conventional beta blockers, suggesting a clinical benefit from addition of ISA to beta blockade in this setting.

Adolescent↗
PubMed1998

Physiologic cardiac pacing in patients with contemporary implantable cardioverter-defibrillators.

Contemporary implantable cardioverter-defibrillators (ICD) incorporate single-chamber ventricular pacing capability. However, because poor ventricular function and/or congestive heart failure is common in the ICD population, the provision of more "physiologic" pacing modes has been receiving increased attention. To evaluate the potential impact of ICDs with physiologic pacing features, we assessed the frequency with which atrial-based pacing modes with or without rate responsiveness are currently used in ICD recipients. Further, we characterized those clinical variables at initial ICD implant that tended to be associated with subsequent need for physiologic pacing. Clinical findings were reviewed in 250 consecutive patients who received ICDs with VVI pacing capability at the University of Minnesota Cardiac Arrhythmia Center between January 1991 and February 1997. Adjunctive physiologic pacing was undertaken in 35 patients (14%): 13 before or at the same time as their ICD, and 22 within a mean of 2.5 years after initial ICD surgery. A history of atrial tachyarrhythmia before ICD implantation (p <0.0001) and treatment with antiarrhythmic drugs at the time of ICD surgery (p <0.05) were predictors of subsequent need for physiologic pacing. The type of presenting ventricular tachyarrhythmia and electrophysiologic parameters (such as the HV interval and the shortest atrial pacing cycle length associated with 1:1 anterograde atrioventricular conduction) were not associated with a subsequent decision to implant a physiologic pacing system. Thus, we conclude that despite the need to implant a second device, physiologic pacing is currently used in an important subset of ICD recipients. Further, certain clinical features at time of ICD implant appear to characterize these patients and may prove helpful in patient selection for the next generation "dual-chamber" ICD.

Adolescent↗
PubMed1998

Vasopressin combined with nitroglycerin increases endocardial perfusion during cardiopulmonary resuscitation in pigs.

Although vasopressin increases vital organ blood flow during cardiopulmonary resuscitation (CPR), endocardial perfusion remains suboptimal. This study was designed to assess the effects of vasopressin versus a combination of vasopressin and nitroglycerin on vital organ blood flow in a porcine model of CPR. After 4 min of cardiac arrest, and 3 min of closed-chest compressions, 14 animals were randomly treated with either 0.4 U/kg vasopressin (n = 7) or 0.4 U/kg vasopressin combined with 5 microg/kg nitroglycerin (n = 7). Coronary and cerebral perfusion pressure as well as left ventricular myocardial blood flow was comparable between groups throughout the experiment. Ninety seconds after drug administration, vasopressin combined with nitroglycerin resulted in comparison with vasopressin alone in significantly higher mean (+/- standard error of the mean) left ventricular endocardial blood flow (78+/-7 vs 51+/-5 ml x min(-1) x 100 g(-1); P < 0.05), and a significantly higher endocardial/epicardial perfusion ratio (0.93+/-0.09 vs 0.57+/-0.06; P < 0.05). Seven of seven animals in the vasopressin group, and four of seven animals in the vasopressin and nitroglycerin group (NS) were resuscitated successfully and survived the 2-h observation period. We conclude that, when compared with vasopressin therapy alone, combined vasopressin and nitroglycerin improved endocardial perfusion significantly immediately after drug administration during CPR.

Analysis of Variance↗
PubMed1998

Review article: heart rate and blood pressure control in vasovagal syncope.

Vasovagal syncope is characterized by transient failure of usually reliable physiologic mechanisms responsible for maintaining both systemic arterial pressure and cerebral blood flow. Two circulatory phenomena are almost universally present: systemic arterial vasodilation and bradycardia. A third phenomenon, cerebrovascular constriction, has also been described but its contribution to the faint is less well established. The neural reflex pathways responsible for triggering the circulatory changes in the vasovagal faint are incompletely understood, but have recently been the subject of renewed interest. In part, this interest probably stems from the frequency with which vasovagal symptoms are now recognized to be the cause of fainting spells. Additionally, however, there is an increasingly recognized need to develop treatment strategies for those affected patients in whom recurrent vasovagal symptoms are particularly troublesome. It is the goal of this discussion to focus on those aspects of circulatory control, and in particular on potential interactions among certain neural and humoral systems, which may contribute to the inappropriate physiologic responses associated with the vasovagal faint.

Afferent Pathways↗
PubMed1998

Submuscular versus subcutaneous pectoral implantation of cardioverter-defibrillators: effect on high voltage pathway impedance and defibrillation efficacy.

Implantable cardioverter-defibrillator (ICD) pulse generators are now routinely positioned in a pectoral location, either submuscularly (under the pectoralis muscles) or subcutaneously (over the pectoralis muscles). Furthermore, in current ICDs, the generator shield usually participates in the defibrillation energy pathway ("hot can"). Consequently, the precise generator location could affect defibrillation system efficacy. To assess this issue, we compared high voltage pathway impedance and defibrillation threshold (DFT) in 20 patients undergoing submuscular and 46 patients undergoing subcutaneous pectoral implantation of an Angeion Sentinel ICD and an AngeFlex dual-coil defibrillation lead. Measurements were performed at time of ICD implant, pre-hospital discharge, and 1, 3 and/or 6 months later. Following induction of ventricular fibrillation, 569 biphasic waveform shocks were delivered between the generator shield and either the distal defibrillation coil (RV/can configuration) or both proximal and distal coils (RV/SVC/can configuration). Impedance differences between submuscular and subcutaneous implants were approximately 3-4 Ohms (p value of 0.132 to < 0.001 depending on time of follow-up and lead configuration). A significant increase in impedance over time was noted independent of implant location and lead configuration. The DFT at implant or pre-discharge was assessed in 27 individuals, and was 9.9 +/- 3.8 J in 8 patients in the submuscular group, and 7.4 +/- 3.3 J in 19 patients in the subcutaneous group (p = 0.057). In conclusion, anatomic location of a "hot can" ICD generator (submuscular versus subcutaneous) influences impedance to defibrillation current, but the impact is of small magnitude and does not appear to result in clinically important differences in DFT.

Aged↗
PubMed1998

Comparison of right atrial and peripheral procainamide infusion levels in patients with spontaneous or induced atrial fibrillation.

As part of a new effort to develop an implantable drug infusion/pacing system to treat atrial fibrillation, this study examined the effects of rapid intracardiac procainamide infusion in humans with pacing-induced atrial fibrillation. Twenty patients with atrial fibrillation for > 5 minutes during an EP study received 500 mg of procainamide either via a peripheral venous infusion (n = 5) or directly in the right atrium (n = 15). Peak coronary sinus and femoral vein procainamide blood levels (mean +/- SEM) during 10, 5, and 3.3 minute central infusions were 17.0 +/- 4.1, 25.1 +/- 4.5, 45.6 +/- 5.1 and 11.3 +/- 3.2, 17.1 +/- 6.4, 18.7 +/- 5.0, respectively. In contrast, peak coronary sinus and femoral procainamide levels following the 5 minute intravenous infusion were 17.7 +/- 5.1 and 9.3 +/- 2.1. Changes in QT, QTc, QRS, and RI intervals were similar at each infusion rate. Systolic blood pressures (BP) decreased more with higher procainamide infusion rates but similar when comparing intravenous versus central drug administration at the same rate. The mean +/- SEM decreases in blood pressure with the 10, 5, and 3.3 min procainamide infusions were 12f5, 20f11, and 39f14, respectively. Conversion to sinus rhythm was not a primary endpoint given the often transient nature of acute atrial fibrillation in this setting. We conclude that significantly higher femoral vein and coronary sinus procainamide levels can be achieved by central rather than peripheral drug infusion. These data support that concept that rapid central infusion of anti-arrhythmic therapy can result in high intracardiac levels of antifibrillatory agents for the treatment of paroxysmal atrial fibrillation.

Adult↗
PubMed1998

A method for permanent transvenous left ventricular pacing.

LV-based pacing has recently been reported to be of benefit in patients with severe cardiac failure and left bundle branch block. LV permanent pacing has been reported using epicardial leads but the surgical mortality is excessive. A transvenous approach is now favored. In this regard, cannulation of the coronary sinus and of one of its tributaries using only the permanent electrode is feasible but technically challenging. We describe a "long guiding sheath" method using catheterization, and a long radiopaque and peelable sheath. Once the coronary sinus is cannulated with the electrophysiological catheter, the long sheath is advanced to the mid-part of the coronary sinus. The permanent pacing electrode is then placed through the sheath and into a tributary of the coronary sinus. This method has been attempted in 10 patients and was successful in 8, with an average lead insertion time of 21 +/- 5.5 minutes and an average fluoroscopic time of 11 +/- 5.5 minutes. In conclusion, although transvenous left ventricular pacing remains a challenge, the "long guiding sheath" approach appears to facilitate this procedure with both a high success rate and an acceptable procedure time.

Bundle-Branch Block↗
PubMed1998

Perfusion technique determines alveolar fluid resorption rate in the isolated perfused rat lung.

The isolated perfused lung (IPL) preparation is a well-established model for the study of alveolar epithelial sodium transport. We noted that preparations of normal fluid-filled rat lungs with recirculated perfusate reproducibly lost weight, whereas preparations in which the perfusate was discarded after a single pass through the lungs had a variable and lesser weight change. To confirm this, we performed IPL experiments by using male Sprague-Dawley specific-pathogen-free rats (175-225 g). In 10 IPLs, perfusate initially was discarded after passing through the lungs and then was recirculated continuously. During the single-pass period, the rate of weight change was +0.7 +/- 2.0 mg/min compared with -9.0 +/- 1.3 mg/min for the recirculating period. Adenosine 3',5'-cyclic monophosphate (cAMP) accumulated during recirculation. The weight loss induced by recirculation was reproduced by perfusion with 8-bromoadenosine 3',5'-cyclic monophosphate or terbutaline in single-pass fashion and blocked when the kinase inhibitor H-8 or phosphodiesterase was present in the recirculating perfusate. In summary, perfusate recirculation in the IPL stimulates fluid resorption at least partially via cAMP. This should be factored into the design and interpretation of IPL experiments.

8-Bromo Cyclic Adenosine Monophosphate↗
PubMed1998

Optimizing standard cardiopulmonary resuscitation with an inspiratory impedance threshold valve.

OBJECTIVES: This study was designed to assess whether intermittent impedance of inspiratory gas exchange improves the efficiency of standard cardiopulmonary resuscitation (CPR). BACKGROUND: Standard CPR relies on the natural elastic recoil of the chest to transiently decrease intrathoracic pressures and thereby promote venous blood return to the heart. To further enhance the negative intrathoracic pressures during the "relaxation" phase of CPR, we tested the hypothesis that intermittent impedance to inspiratory gases during standard CPR increases coronary perfusion pressures and vital organ perfusion. METHODS: CPR was performed with a pneumatically driven automated device in a porcine model of ventricular fibrillation. Eight pigs were randomized to initially receive standard CPR alone, while seven pigs initially received standard CPR plus intermittent impedance to inspiratory gas exchange with a threshold valve set to -40 cm H2O. The compression:ventilation ratio was 5:1 and the compression rate was 80/min. At 7-min intervals the impedance threshold valve (ITV) was either added or removed from the ventilation circuit such that during the 28 min of CPR, each animal received two 7-min periods of CPR with the ITV and two 7-min periods without the valve. RESULTS: Vital organ blood flow was significantly higher during CPR performed with the ITV than during CPR performed without the valve. Total left ventricular blood flow (mean+/-SEM) (mL/min/g) was 0.32+/-0.04 vs 0.23+/-0.03 without the ITV (p<0.05). Cerebral blood flow (mL/min/g) was 20% higher with the ITV (+ITV, 0.23+/-0.02; -ITV, 0.19+/-0.02; p<0.05). Each time the ITV was removed, there was a statistically significant decrease in the vital organ blood flow and coronary perfusion pressure. CONCLUSIONS: Intermittent impedance to inspiratory flow of respiratory gases during standard CPR significantly improves CPR efficiency during ventricular fibrillation. These studies underscore the importance of lowering intrathoracic pressures during the relaxation phase of CPR.

Animals↗
PubMed1997

Evaluation of different ventricular pacing sites in patients with severe heart failure: results of an acute hemodynamic study.

BACKGROUND: Multisite ventricular pacing has recently been proposed as an additional treatment for patients with severe congestive heart failure. To further assess the potential value of this technique, we compared the acute hemodynamic changes associated with pacing the right ventricular apex (RVA) or outflow tract (RVOT) alone, the left ventricle (LV) alone, or biventricular (BIV) pacing of the RVA and LV together. METHODS AND RESULTS: Acute hemodynamic findings were measured in 27 patients with severe heart failure despite optimal therapy and either first-degree AV block and/or an intraventricular conduction defect. In the 23 patients with a high pulmonary capillary wedge pressure (PCWP) (>15 mm Hg), data were collected after transvenous pacing at different ventricular sites in either the VDD mode (AV delay=100 ms) or the VVI mode in patients with atrial fibrillation (n=6). The mean baseline cardiac index was 1.82 L x min(-1) x m(-2). Mean+/-SD baseline systolic blood pressure (SBP) (118.5+/-15.2 mm Hg), PCWP (26.4+/-6.6 mm Hg), and V-wave amplitude (39.1+/-14.6 mm Hg) were similar before and after either RVA or RVOT pacing. In contrast, LV-based pacing (either LV alone or BIV pacing) resulted in higher SBP (P<.03) and lower PCWP (P<.01) and V-wave amplitude (P<.001) than either baseline or RV pacing measurements. With LV pacing alone, SBP, PCWP, and V waves were 126.5+/-15.1, 20.7+/-5.9, and 25.5+/-8.1 mm Hg, respectively. The results with LV pacing alone were similar to those obtained with BIV pacing. CONCLUSIONS: In patients with severe congestive heart failure, both LV pacing alone and BIV pacing resulted in a similar and significant acute improvement in SBP, PCWP, and V-wave amplitude compared with baseline measurements and RV pacing alone. These results provide a strong basis for initiating long-term studies examining the chronic effects of LV-based pacing in patients with medically refractory congestive heart failure.

Adult↗