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Biomedical subjects

V Paul

Publications and source records attributed to V Paul.

At least 37 records · Page 2Linked to original sources
PubMed2000

Does the mechanism of action of biatrial pacing for atrial fibrillation involve changes in cardiac haemodynamics? Assessment by Doppler echocardiography and natriuretic peptide measurements.

AIMS: The antifibrillatory mechanism of biatrial (BI) pacing has not been fully elucidated. We investigated the role of a haemodynamic mechanism in eight patients implanted with a BI pacemaker (Chorus RM) by comparing changes in mitral Doppler flow and atrial and B-type natriuretic peptide levels (ANP, BNP) with BI pacing compared with sinus rhythm and right atrial (RA) pacing. METHODS AND RESULTS: Measurements were taken after 60 min in the supine position in each of two pairs of randomized pacing modes: (a) AAI40 beats x min(-1), (allows sinus rhythm mean rate 56 beats x min(-1), SR) vs AAI 40 beats x min(-1) with synchronized left atrial pacing (SRSync); (b) overdrive AAI RA pacing (89 beats x min(-1) (n = 6) or 70 beats x min(-1) (n = 2)) vs overdrive AAI BI pacing. Within each pair there was significant earlier activation of the left atrial Doppler signal in relation to the surface ECG P wave with BI pacing (SR 163 +/- 10 ms vs SRSync 144 +/- 21 ms (P = 0.02), and RA 232 +/- 14 ms vs BI 196 +/- 16 ms (P = 0.001)), and significant shortening of the P-R interval (SR 163 +/- 29 ms vs SRSync 148 +/- 20 (P = 0.007) and RA 261 +/- 27 ms vs BI 232 +/- 23 (P = 0.001)). The net observed effect was of no change in the atrioventricular timing sequence (delay of peak E or A to QRS/ mitral valve closure) and no change in other Doppler echo parameters. Levels of the cardiac peptides ANP and BNP were raised compared with healthy controls, but did not significantly change during the study. CONCLUSION: Acute BI pacing shortens the P-R interval and causes earlier left atrial contraction in relation to the surface electrocardiogram P wave. It does not alter the atrioventricular timing cycle, any other Doppler measurements or change cardiac peptide levels. This suggests that BI pacing does not cause haemodynamic changes that could account for any antifibrillatory properties.

Aged↗
PubMed2000

A comparison between passive and active fixation leads in the coronary sinus for biatrial pacing: initial experience.

AIMS: It has been reported that biatrial pacing can prevent the recurrence of atrial fibrillation. This technique requires a stable coronary sinus (CS) lead position for left atrial pacing. We report our experience of CS pacing with a specifically designed lead [Medtronic 2188 (n= 19)] and active fixation leads [Pacesetter Tendril (n=3), Medtronic Capsurefix (n=6)] in 21 patients with paroxysmal atrial fibrillation and a normal mean left atrial size of 39 mm (range 33-54 mm). METHODS AND RESULTS: Using the Medtronic 2188 lead, successful initial CS canulation and lead positioning was achieved in all 19 patients. One patient developed subclavian vein thrombosis 3 months after initial implant. Eight patients (42%) experienced subsequent lead displacement (12 displacements in total). Of these, seven had their lead replaced with active fixation leads. In addition, two patients underwent active fixation lead implantation at first implant. CS canulation and lead positioning was successful in all nine patients. No patient suffered displacement of an active fixation lead. There were no complications in this group. Twelve of the 19 (66%) Medtronic 2188 leads were functioning at long-term follow-up (11 +/- 4 months) with a biatrial pacing threshold of 2.4 +/- 1 V. Eight of the nine (89%) active fixation leads were functioning at long-term follow-up (6 +/- 3 months) with a biatrial pacing threshold of 2.9 +/- 1.1 V. Using a combined approach 95% of patients had a functioning CS lead at long-term follow-up. CONCLUSION: Active fixation leads can safely be used for left atrial pacing via the CS with good long-term pacing thresholds and stability.

Aged↗
PubMed2000

Initial United Kingdom experience with the use of permanent, biventricular pacemakers: implantation procedure and technical considerations.

AIMS: To describe the institution of a biventricular pacing programme with particular reference to the implantation procedure and new technological considerations. METHODS AND RESULTS: Analysis of outcomes of a consecutive series of 54 patients undergoing attempted biventricular pacemaker implantation between February 1998 and April 1999. Successful implantation was achieved in 49 of the 54 patients (91%). Five patients required lead repositioning after initial successful implantation. Left ventricular lead pacing thresholds were found to be satisfactory and stable in the long term, with pacing thresholds of 1.3 V, 1.9 V and 1.6 V at implantation, 1 and 3 months, respectively. Left-sided lead function was not dependent on lead position within the tributaries of the coronary sinus. The implantation procedure was found to be safe, although one patient died during long-term follow-up. CONCLUSION: With appropriate previous experience in complex and coronary sinus pacing and with access to up-to-date pacemaker and lead technology, a biventricular pacemaker implantation service can be instituted with good medium-term results.

Adult↗
PubMed2000

Initial results with left ventricular pacemaker lead implantation using a preformed "peel-away" guiding sheath and "side-wire" left ventricular pacing lead.

We report our preliminary experience with the use of preformed "peel-away" guiding sheaths and "side-wire" pacing leads for permanent biventricular pacemaker insertion in 13 patients with heart failure. Three of these patients were undergoing an upgrade of a preexistent VVIR pacing system after prior His ablation for medically refractory atrial fibrillation. Six of the patients had undergone attempted biventricular pacemaker insertion, but required left ventricular lead repositioning after total implantation failure or late displacement of the lead. The remaining patients were undergoing new system implantation. Target vessel cannulation was achieved in all patients. However, in one patient, diaphragmatic pacing throughout the target vessel length prevented successful implantation. All other implants were ultimately successful (92% success rate). We conclude that device implantation using a preformed sheath and side-wire pacing lead is feasible and may offer significant benefits over implantation with currently available technology.

Adult↗
PubMed2000

Preliminary results with the simultaneous use of implantable cardioverter defibrillators and permanent biventricular pacemakers: implications for device interaction and development.

We report our preliminary experience with the combined use of implantable cardioverter defibrillators (ICD) and biventricular pacemakers in six patients with heart failure and malignant ventricular arrhythmia. Two patients underwent ICD implantation for malignant ventricular arrhythmia after previous biventricular pacemaker implantation. One patient underwent biventricular pacemaker insertion for NYHA Class III heart failure after previous ICD implantation. Two patients underwent single device implantation. In the sixth patient, a combined implantation failed due to an inability to obtain a satisfactory left ventricular pacemaker lead position. The potential for device interaction was explored during implantation. In two patients a potentially serious interaction was discovered. Subsequent alterations in device configuration and programming prevented these interactions with long-term use. No complication of combined device use has been demonstrated during a mean follow-up of 2 months (range 1-4 months). Satisfactory ICD and pacemaker function has also been demonstrated. We conclude that combined device implantation may be feasible with currently available pacing technology and that further prospective studies are required in this area.

Adult↗
PubMed1999

Evaluation of biatrial pacing, right atrial pacing, and no pacing in patients with drug refractory atrial fibrillation.

It has been suggested biatrial pacing may prevent the recurrence of atrial fibrillation (AF). To further evaluate this hypothesis, we performed a randomized, single-blinded study in 19 patients with drug refractory AF. The study compared biatrial pacing with conventional right atrial (RA) pacing and a control period of inhibited pacing. The pacing modes utilized were DDD with a base rate of 70 beats/min for biatrial and RA pace (with and without biatrial resynchronization, respectively) and 40 beats/min for the control period. The duration of each pacing mode was 3 months. The number of AF episodes and their duration were obtained from pacemaker Holter memory (Chorus RM ELA Medical). Comparison of the control period (n = 11) with either pacing strategy showed a significant decrease in the total duration of AF (control 27 +/- 35 days, biatrial 8 +/- 15 days p = 0.02, RA 11 +/- 27 days p = 0.04). However, there was no effect on the number of AF episodes (control 79 +/- 108, biatrial 36 +/- 75 p = 0.32, RA 41 +/- 80 p = 0.11). The total percentage of atrial pacing also significantly increased when the control period (6 +/- 9%) was compared with both RA pace (62 +/- 33%, p = 0.008) and biatrial pace (63 +/- 31, p = 0.003). When biatrial pacing was compared with RA pace (n = 19), there was no significant difference in either the duration of AF (biatrial 16 +/- 26 days vs RA 19 +/- 31 days, p = 0.7) or the number of AF episodes (biatrial 56 +/- 91 vs RA 87 +/- 106, p = 0.34). In conclusion, pacing (either type) at a base rate of 70 beats/min has an antifibrillatory effect when compared with inhibited pacing at 40 beats/min. No additional benefit of biatrial pacing over right atrial pacing was demonstrated in this study.

Aged↗
PubMed1999

Role of nitric oxide on GABA, glutamic acid, activities of GABA-T and GAD in rat brain cerebral cortex.

The results of the present study clearly shows that a correlation exists between nitric oxide (NO) and gamma-aminobutyric acid transaminase (GABAT-T) activity as well as gamma-aminobutyric acid (GABA), glutamic acid and the activity of glutamic acid decarboxylase (GAD). Supporting of this 10 min after the administration of L-Arginine (L-Arg) increased GABA concentration and diminished the activity of GABA-T. There was no change in GAD activity and glutamic acid level. Administration of convulsion inducing agent Picrotoxin (PCT) decreased the NO concentration in the brain and enhanced the activity of GABA-T, and the fact that the NOS inhibitor (N(G)-nitro-L-Arg methyl ester (L-NAME) diminished the activity of NOS and increased the activity of GABA-T provide another support for the involvement of NO on GABA-T activity. The present study clearly showed that high concentrations of NO in the brain suppresses the activity of GABA-T.

4-Aminobutyrate Transaminase↗
PubMed1999

Involvement of nitric oxide and nitric oxide synthase activity in anticonvulsive action.

The anticonvulsant drug Diazepam (DIA-2 mg/kg b. wt), the nitric oxide (NO) donor L-Arginine (L-Arg-2000 mg/kg b. wt) and the putative nitric oxide synthase (NOS) inhibitor N(G)-Nitro-L-Arginine methyl ester (L-NAME-50 mg/kg b. wt) were used to determine the role of endogenous NO on convulsions induced by picrotoxin (PCT-5 mg/kg b. wt) in rats. Rats given a convulsant dose of PCT (5 mg/kg b. wt) had convulsion and it suppresses the NOS activity and NO concentration in brain regions. The anticonvulsant L-Arg alone significantly increases the NO concentration and NOS activity in brain regions, but not diazepam. Whereas DIA, along with L-Arg, enhances the NO and NOS activity when compared to L-Arg alone. The combination of both OIA and L-Arg completely suppressed the convulsions. L-NAME alone had no effect to produce convulsions but it completely decreased NO concentration and NOS activity and potentiated the PCT convulsions. This was reverted by pre- and post treatment of DIA plus L-Arg indicating, the increased NO concentration and NOS activity in brain regions suppresses convulsions.

Animals↗
PubMed1999

Spatial and temporal expression of the cystathionine beta-synthase gene during early human development.

We report the cystathionine-beta synthase (CBS) gene expression pattern during early human embryogenesis (3 to 6 weeks post conception) by in situ hybridization and in fetal and adult tissue by Northern Blot analysis. Probes were chosen to recognize either the common sequence to all known CBS mRNAs or the sequences of two different major exons 1 issued of we have previously identified. We demonstrate by in situ hybridization that CBS is continuously expressed from the earliest stages studied (22 days post conception) during embryogenesis in the tissues of developing embryos which will after birth present clinical abnormalities in homocystinuria patients. It is expressed at an especially high level in the neural and cardiac systems until the liver primordium appears. In embryonic central nervous system, the whole neural tube and primary brain vesicles are labeled. Secondary brain vesicles labeling are dependent on the neuroepithelium differentiation. The ventricular layer of the rhombencephalon, cranial nerve nuclei and then after cerebellar cortex derived from rhombencephalon ventricular layer are strongly labeled. Thalamus and other derivatives of the diencephalon plate, the neuroblastic layer of the retina, lens and dorsal root ganglia are labeled. After 35 days post conception, CBS mRNAs was detected in endocardial cells and in cells derived from the neural crest of the heart and in particular developing mesodermic regions such as the primitive hepatocytes of the liver, mesonephros vesicles, various endocrine glands and developing bones. We could not detect tissue specificity of different probes at this embryonic stage. Northern blot analysis consistently detected mRNA species in fetal 25 weeks post conception brain, liver and kidney. The common cDNA probe revealed the 2.5 and 3.7 kb mRNA species from brain, liver and kidney. The exon 1b probe detected only the 2.5 kb mRNA and the exon 1c probe the 3.7 kb mRNA in these three tissues. In adult tissue, the 1b probe detected only the 2.5 kb mRNA and the 1c probe only the 3.7 kb mRNA in the liver.

Adult↗
PubMed1999

Staurosporine derivatives from the ascidian eudistoma toealensis and its predatory flatworm pseudoceros sp

Two new indolocarbazole alkaloids, 3-hydroxy-3'-demethoxy-3'-hydroxystaurosporine (5) and 11-hydroxy-4'-N-demethylstaurosporine (6), were isolated from the marine ascidian Eudistoma toealensis and its predator, the marine flatworm Pseudoceros sp. In addition, five known derivatives were isolated in their protonated states, which caused the pyran-ring system to adopt a boat conformation. The structures were determined by 1D and 2D homonuclear and (1)H-detected heteronuclear NMR spectroscopy and from comparisons with published data. The heteronuclear correlations were necessary to establish reliable data for the structure elucidation.

Journal Article↗
PubMed1999

Initial experience in the extraction of chronically implanted pacemaker leads using the Excimer laser sheath.

OBJECTIVE: To assess the safety and efficiency of the Excimer laser sheath in extracting chronically implanted pacemaker leads. PATIENTS: Eight patients were studied (one female, mean age 62 years, range 34 to 77) with 17 pacemaker leads (five atrial, 10 ventricular, two implantable defibrillator). The mean implantation time was 65 months (range 23 to 188). The indications for lead extraction were chronic infection (7), superior vena cava obstruction (4), lead malfunction (4), and pain (2). METHODS: A prospective analysis of the use of the Excimer laser sheath in extracting chronically implanted pacemaker leads. Laser sheath extraction was undertaken if conventional extraction techniques with simple traction or traction with a locking stylet had failed. If laser sheath extraction was unsuccessful, basket retrieval of the lead from the groin was performed. RESULTS: Complete lead removal was achieved in 16 leads (94%). In one case the electrode tip was left behind without complication. Extraction was achieved with the laser sheath alone in 16 leads. Basket retrieval was required in one case after laser failure. There were no complications. CONCLUSIONS: The Excimer laser sheath appears to be an effective and safe technique for extracting chronically implanted pacemaker leads. It can be used in combination with the currently available techniques for successful lead extraction.

Adult↗
PubMed1999

Independent and combined effects of L-arginine and diazepam on ammonium chloride-induced convulsions in rats.

The independent and combined effects of L-arginine (840 mg/kg) and diazepam (0.75 mg/kg) pretreatment (30 min) were tested on ammonium chloride (400 mg/kg)-induced convulsions in rats. Ammonia concentrations were determined in blood and brain regions (cerebral cortex, brain stem and cerebellum) 30 min after L-arginine or diazepam treatment. Ammonia concentrations were measured at the time of induction of convulsions by ammonium chloride in L-arginine, diazepam or saline pretreated animals. L-arginine and not diazepam decreased ammonia concentrations in control as well as in ammonium chloride-treated animals. However, both the compounds suppressed convulsions elicited by ammonium chloride. Protection produced concurrently by these agents was much greater than that produced by them independently. It is concluded that convulsions caused by hyperammonemic condition can be suppressed either by preventing a rise in brain ammonia to toxic level or by anticonvulsant agents having a GABA potentiating action. A much greater protection can be achieved if agents having these properties are administered concurrently.

Ammonia↗
PubMed1999

[Simultaneous utilization of an implantable automatic defibrillator in a patient with previously implanted bi-ventricular pacemaker for end-stage heart failure].

We report a case of implantable cardioverter defibrillator (ICD) use after previous biventricular pacemaker insertion for end-stage heart failure. A 75-year-old man with inoperable three-vessel coronary artery disease, permanent atrial fibrillation and end-stage heart failure underwent bi-ventricular pacemaker insertion and His bundle ablation for symptomatic control. NYHA class decreased from class III to II after this procedure. Four months after implant the patient developed paroxysmal sustained, symptomatic ventricular tachycardia. ICD implantation was undertaken. No potentially serious ICD-pacemaker interaction was noted during subsequent follow-up. We conclude that ICD implantation is feasible after previous bi-ventricular pacemaker insertion, without the need to explant the bi-ventricular pacing device.

Aged↗
PubMed1999

Effects of L-arginine on picrotoxin-induced increase in brain ammonia concentrations and convulsions in rats.

The effect of L-arginine (840 mg/kg) pre- (30 min before challenge) and post-treatment (5 min after challenge) period was tested on picrotoxin-induced increase in ammonia concentrations in brain regions (cerebral cortex, brain stem and cerebellum) and the accompanying convulsive responses in adult male rats. The combined effect of L-arginine and diazepam was also tested against picrotoxin-induced convulsions. Picrotoxin-induced increase in ammonia was reverted partially by L-arginine pretreatment. However, L-arginine pretreatment did not show anticonvulsant effect independently or concurrently with diazepam. On the other hand, L-arginine post-treatment reverted ammonia to control level in all brain regions. A partial but significant inhibition of convulsion responses was found in these animals. The combined effect of diazepam and L-arginine post-treatment was much greater than that produced by these agents independently. These findings suggest that ammonia has a partial but significant participation in the convulsant action of picrotoxin. L-arginine has a potential to revert brain ammonia to control level in picrotoxin-treated animals and thereby it has produced a partial protection. The data further indicate that the duration of action of L-arginine is considerably short and has an additive anticonvulsant action with diazepam.

Ammonia↗
PubMed1998

Multisite pacing as a supplemental treatment of congestive heart failure: preliminary results of the Medtronic Inc. InSync Study.

This report describes the initial results of the "InSync" study, a European and Canadian multicenter trial that examines the safety and efficacy of a multisite pacemaker (Medtronic InSync) and of left ventricular pacing leads (Medtronic 2187 and 2188) implanted via a cardiac vein as a supplemental treatment of refractory congestive heart failure. Over a 10-month period, the system was implanted successfully in 68 of the 81 (84%) patients who had been enrolled in the study. The 68 patients were, on average, 66 +/- 10 years old, had a mean left ventricular ejection fraction (LVEF) = 21% +/- 9%, and 63% were in NYHA functional Class III and 37% were in Class IV. No system implant related complication occurred. During follow-up, 7 of 10 patients who exited the study had died, 4 suddenly. There was a clinical benefit among surviving patients, which was corroborated by a significant improvement in NYHA functional class and in the Minnesota Living with Heart Failure Quality of Life Questionnaire Score (MLS) and by a longer distance covered during a 6-minute walk test. This clinical improvement was associated with a significant narrowing of the paced QRS complex during biventricular pacing, a significant decrease in the interventricular mechanical delay, and a trend towards an increase in the duration of ventricular filling. These encouraging preliminary results confirm the feasibility and reliability of this new multisite pacing system in the management of dilated cardiomyopathy and support the continuation of further evaluations of this complementary treatment of refractory congestive heart failure.

Aged↗
PubMed1998

Radiofrequency ablation of a fascicular tachycardia after orthotopic cardiac transplantation.

A 51 year old male received an orthotopic transplant because of end stage ischaemic heart disease. The donor was a healthy male teenager with no history of arrhythmias or other cardiac conditions. The patient presented with haemodynamically stable tachycardia and dyspnoea five weeks post-transplant. The ECG showed a regular tachycardia of 140 beats/min with a right bundle branch block morphology, left axis deviation, and a QRS duration of 135 ms. There were independent P waves, capture, and fusion beats confirming the diagnosis of ventricular tachycardia. Endomyocardial biopsy showed moderate focal rejection that was thought to be responsible for the arrhythmia. During the following six months the patient had recurrent tachyarrhythmias; on each occasion the ECG morphology was the same and there was no cellular rejection. The patient continued to have frequent hospital admissions with ventricular tachycardia requiring DC cardioversion despite the empirical use of amiodarone, sotalol, disopyramide, and procainamide. Eighteen months after transplantation the diagnosis of fascicular tachycardia was suspected by ECG morphology and supported by successful termination with intravenous verapamil. The arrhythmia was successfully managed by radiofrequency ablation. This patient shows that arrhythmias following transplantation are not always related to rejection, and that other potentially reversible causes should be considered, particularly when the ECG during arrhythmia conforms to a classic configuration.

Catheter Ablation↗
PubMed1998

A new method of mechanical circulatory support with an implantable multichamber pump system (IMPS): presentation and first experimental results.

This paper presents a new cardiac support device for left ventricular failure which consists of two inflatable bellows positioned dorsally and ventrally to the left ventricle. The implantable multichamber pump system (IMPS) is driven by a pneumatic pump system and controlled by a microcomputer using ECG-trigger and pacemaker modules. It was implanted via thoracotomy in 8 pigs. The circulatory parameters were measured in the animals on beta-blockers, with cardiac failure and in ventricular fibrillation with an activated (IMPS on) and deactivated (IMPS off) system. IMPS significantly increased the left ventricular pressure (LVPsys IMPS off: 63 +/- 6 mmHg vs IMPS on: 96 +/- 8 mmHg) and the blood pressure in the common carotid artery (BPca, IMPS off: 69/38 mmHg vs IMPS on: 95/40 mmHg). The IMPS proved to be highly efficient in the therapy of animals with acute cardiac failure and in ventricular fibrillation in the experimental model. Apart from its efficiency the advantages with this system are the ease of handling and its high biocompatibility due to the lack of contact with circulating blood.

Adrenergic beta-Antagonists↗