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N J Linker

Publications and source records attributed to N J Linker.

At least 19 recordsLinked to original sources
PubMed2005

One year results of the Middlesbrough early revascularisation to limit infarction (MERLIN) trial.

OBJECTIVE: To report one year results of the MERLIN (Middlesbrough early revascularisation to limit infarction) trial, a prospective randomised trial comparing the strategy of coronary angiography and urgent revascularisation with conservative treatment in patients with failed fibrinolysis complicating ST segment elevation myocardial infarction (STEMI). The 30 day results have recently been published. At the planning stage of the trial, it was determined that follow up of trial patients would continue annually to three years to determine whether late benefit occurred. SUBJECTS: 307 patients who received a fibrinolytic for STEMI but failed to reperfuse early according to previously described ECG criteria and did not develop cardiogenic shock. METHODS: Patients were randomly assigned to receive either emergency coronary angiography with a view to proceeding to urgent revascularisation (rescue percutaneous coronary intervention (rPCI) arm) or continued medical treatment (conservative arm). The primary end point was all cause mortality at 30 days. The secondary end points included the composite end point of death, reinfarction, stroke, unplanned revascularisation, or heart failure at 30 days. The same end points were evaluated at one year and these results are presented. RESULTS: All cause mortality at one year was similar in the conservative arm and the rPCI arm (13.0% v 14.4%, p = 0.7, risk difference (RD) -1.4%, 95% confidence interval (CI) -9.3 to 6.4). The incidence of the composite secondary end point of death, reinfarction, stroke, unplanned revascularisation, or heart failure was significantly higher in the conservative arm (57.8% v 43.1%, p = 0.01, RD 14.7%, 95% CI 3.5% to 25.5%). This was driven almost exclusively by a significantly higher incidence of subsequent unplanned revascularisation in the conservative arm (29.9% v 12.4%, p < 0.001, RD 17.5%, 95% CI 8.5% to 26.4%). Reinfarction and clinical heart failure were numerically, but not statistically, more common in the conservative arm (14.3% v 10.5%, p = 0.3, RD 3.8%, 95% CI -3.7 to 11.4, and 31.2% v 26.1%, p = 0.3, RD 5.0%, 95% CI -5.1 to 15.1). There was a strong trend towards fewer strokes in the conservative arm (1.3% v 5.2%, p = 0.06, RD -3.9%, 95% CI -8.9 to 0.06). CONCLUSION: At one year of follow up, there was no survival advantage in the rPCI arm compared with the conservative arm. The incidence of the composite secondary end point was significantly lower in the rPCI arm, but this was driven almost entirely by a highly significant reduction in the incidence of further revascularisation.

Adult↗
PubMed2003

Early and late reactions following the use of iopamidol 340, iomeprol 350 and iodixanol 320 in cardiac catheterization.

GOAL: To investigate the incidence of early (< 24 hours) and late (> 24 hours to 7 days) reactions to 3 contrast agents commonly used in cardiac catheterization. METHODS AND RESULTS: A total of 2,108 patients undergoing cardiac catheterization in a Regional Cardiothoracic Unit were randomly assigned to receive 1 of 3 commonly used contrast agents in a prospective, double-blind study. The contrast agents were iopamidol 340 (Niopam ), a nonionic monomer; iomeprol 350 (Iomeron ), a nonionic dimer; and iodixanol 320 (Visipaque ), a nonionic dimer. The main outcome measures were the incidence of early (< 24 hours) reactions following catheterization and the incidence of late (24 hours to 7 days) reactions. Early reactions, excluding patients with heat on left ventriculography as the sole symptom, were relatively common (7.4%), but there was no significant difference between the 3 agents (p = 0.35). Late skin reactions, excluding reactions solely at the site of the arterial puncture and continuations of early urticarial reactions, were also relatively common (5.4%), but the incidence differed between the 3 agents. Such reactions occurred in 2.7% of those receiving iopamidol 340 (Niopam ), 3.5% of those receiving iomeprol 350 (Iomeron ) and 10.4% of those receiving iodixanol 320 (Visipaque ) (p < 0.01). CONCLUSION: The incidence of early adverse reactions is similar with these 3 contrast agents. However, late skin reactions are significantly more common with iodixanol 320 (Visipaque ) than with the other 2 agents. Although such reactions were rarely troublesome, patients should be advised accordingly.

Adolescent↗
PubMed2000

Coexistent atrioventricular and nodoventricular pathways in a patient with hypertrophic cardiomyopathy.

A 17-year-old girl with concentric hypertrophic cardiomyopathy presented with a wide complex tachycardia and underwent electrophysiological study. She was found to have an antidromic tachycardia utilizing a decremental atrioventricular fiber as the anterograde limb with retrograde conduction occurring through the septum. Ablation of a right free-wall pathway rendered tachycardia noninducible, yet ventricular preexcitation remained. After ablation there was evidence of a second nodoventricular connection. We believe this to be the first report of coexistent "Mahaim" fibers; one a decremental atrioventricular connection and the second nodoventricular.

Adolescent↗
PubMed1998

Subpectoral implantation of a cardioverter defibrillator under local anaesthesia.

OBJECTIVE: To evaluate patient acceptability of submuscular implantation of a cardioverter defibrillator (ICD) under local anaesthesia with conscious sedation. DESIGN: Retrospective review. Patient acceptability in the second half of the study was routinely assessed within 24 hours. SETTING: Regional cardiac centre. PATIENTS: 45 consecutive patients with either aborted sudden death or haemodynamically unstable ventricular tachycardia were referred for ICD implantation. INTERVENTIONS: A subpectoral implantation technique was employed. Twelve procedures were performed under general anaesthesia. Thirty three patients were sedated with midazolam and diamorphine, and local anaesthesia was achieved with bupivicaine. Ventricular fibrillation for defibrillation threshold testing was induced by alternating current, T wave shock, or ultrarapid burst pacing. Patients were contacted after the procedure to assess acceptability. RESULTS: 32 patients having implantation under local anaesthesia did not recall the surgical procedure. One patient described an awareness of "pushing" as the generator was positioned in the pocket. Seven patients said that the procedure was painless but recalled a test shock, four describing it as mildly uncomfortable. All 33 patients stated that they would be willing to have a second implant under local anaesthesia. Twelve patients who had the implant performed under general anaesthesia had no recollection of the procedure. Mean (SD) total procedure duration was significantly longer in those who had general anaesthesia (93 (16) v 67 (17) minutes; p = 0.0009). CONCLUSIONS: Subpectoral implantation of ICDs may be performed safely with patient acceptability under local anaesthesia with conscious sedation.

Anesthesia, Local↗
PubMed1998

The transseptal approach for ablation of cardiac arrhythmias: experience of 104 procedures.

OBJECTIVE: To report retrospectively on the training and subsequent experience of two operators in transseptal ablation of arrhythmias arising in the left atrium and left atrioventricular annulus, to show whether, with adequate training and careful attention to detail, this is a safe and effective technique. SETTING: Electrophysiological studies and transseptal procedures were performed in the electrophysiology laboratories of the Moffatt Hospital, University of California at San Francisco (39) and Manchester Royal Infirmary (65) from January 1993 to June 1997. Close supervision by a fully trained operator was provided for at least the first 20 procedures performed by each operator. PATIENTS: 94 consecutive patients underwent electrophysiological study and ablation for Wolff-Parkinson-White syndrome with left sided accessory connections (81 patients) or ectopic atrial tachycardia (13 patients); 104 transseptal procedures were done; eight patients required multiple procedures. RESULTS: 92 patients (98%) were initially successfully ablated. Five of 81 with accessory pathways (6%) and three of 13 with atrial tachycardia (23%) required further procedures. One patient with Wolff-Parkinson-White syndrome could not be ablated at a second procedure. Long term success rate for accessory pathway ablation was therefore 99%. Procedures were abandoned in three patients because of minor complications. All were subsequently ablated successfully by a transseptal approach on another day. CONCLUSIONS: The transseptal approach is safe and effective for ablation of left sided arrhythmias. The technique has similar success rates to the retrograde transaortic approach but without the risk of inadvertent damage to the coronary arteries or aortic valve.

Adolescent↗
PubMed1992

Cost implications of the British Pacing and Electrophysiology Group's recommendations for pacing.

OBJECTIVE: To compare present pacing practice with the recommendations recently published by the British Pacing and Electrophysiology Group and to assess the increase in annual budget required to implement these recommendations in a regional cardiothoracic unit. DESIGN: Retrospective analysis of pacemaker implantation for 1991 with calculation of the costs required to implement the group's recommendations based on average 1991 costs of the types of pacing generators and electrode leads used. SETTING: Regional cardiothoracic unit for South West Thames Health Authority. PATIENTS: 433 consecutive patients receiving permanent pacemaker generators: 76 (18%) with sinus node disease; 270 (62%) with atrioventricular block; 25 (6%) with both sinus node disease and atrioventricular block; 59 (14%) with chronic atrial fibrillation and atrioventricular block; and 3 (1%) with carotid sinus or malignant vasovagal syndromes. RESULTS: Only 102 (24%) patients received pacemaker generators recommended by the British Pacing and Electrophysiology Group; however, 355 (82%) patients were older than 65 years, and 264 (61%) were aged 75 or over. The cost of hardware for pacing was 462,885 pounds. Using generators as recommended would have cost 810,525 pounds for "optimal" systems (an increase of 75%) and 710,750 pounds for "alternative" systems (an increase of 54%). These increases would have been considerably reduced by limiting the use of sophisticated pacing to younger patients (aged under 75). Further savings could be made by using the least expensive pacing models available. CONCLUSIONS: Implementing these recommendations should reduce morbidity related to bradyarrhythmia but will lead to major increases in pacing costs. Age and patients' expected activity may be used to select simple pacing systems and thus to contain cost. More research is needed to determine which patient groups will benefit most from complex pacing systems.

Adult↗
PubMed1992

Assessment of QT dispersion in symptomatic patients with congenital long QT syndromes.

It has been suggested that QT dispersion recorded on the surface electrocardiogram may be a predictor of arrhythmic events in patients with congenital QT prolongation. To evaluate this, 9 patients (6 female, mean age 17.6 years) with congenital long QT syndromes, all of whom had syncope and documented torsades de pointes, were studied. Patients were studied off treatment and during therapy with beta-blocking agents. Three patients were also studied after left stellate ganglionectomy. An age-matched control group was also studied. Good quality 12-lead electrocardiograms were recorded from all patients. For each lead, QT and RR intervals were measured, and QTc value was calculated. QT and QTc dispersions were calculated for each patient. Patients had a significantly longer mean QT interval compared with that of the control group (450 +/- 100 vs 359 +/- 63 ms; p = 0.015) at similar mean RR intervals (736 +/- 231 vs 783 +/- 289 ms), with a longer mean QTc value (0.53 +/- 0.08 vs 0.41 +/- 0.02 s1/2; p = 0.004). Patients also had longer QT and QTc dispersions compared with those of the control group (110 +/- 45 vs 43 +/- 12 ms [p = 0.004], and 0.108 +/- 0.03 vs 0.05 +/- 0.02 s1/2 [p = 0.002], respectively). QT and QTc dispersions on and off beta-blocking agents were not significantly different. Comparing patients with frequent and those with infrequent symptoms, there was no difference in QT or QTc dispersion either off treatment or during therapy with beta-blocking agents.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1992

Difficulties in the use of electrocardiographic criteria for the differential diagnosis of left bundle branch block pattern tachycardia in patients with a structurally normal heart.

In patients with left bundle branch block pattern tachycardia, electrocardiographic criteria, based on leads V1, V2 and V6, have been shown to be effective for the diagnosis of ventricular tachycardia in patients with a previous myocardial infarct. To test these criteria on a wider population, we studied 53 consecutive patients with left bundle branch block pattern tachycardia. Seventeen patients had supraventricular tachycardia and 36 had ventricular tachycardia, 18 with a previous myocardial infarction, two with cardiomyopathy, and 16 with a normal heart. The sensitivity for the diagnosis of ventricular tachycardia in patients with a previous myocardial infarct of the combined criteria was 100% but was only 50% for the other patients, which was not significantly different from the patients with supraventricular tachycardia (29%). Two other criteria, right axis shift in tachycardia and ventricular ectopics during sinus rhythm with the same morphology as the tachycardia, were only seen in patients with ventricular tachycardia, and combined with the other criteria allowed the correct identification of 35/36 patients with ventricular tachycardia. To conclude, the electrocardiographic criteria based on leads V1, V2 and V6 are not sensitive for the diagnosis of a ventricular origin of left bundle branch block pattern tachycardia in patients with a normal heart and additional criteria are required for the diagnosis in these patients.

Adult↗
PubMed1992

Catheter ablation by low energy DC shocks for successful management of atrial flutter.

OBJECTIVE: To assess the effects of low energy ablation of the substrate for atrial flutter. DESIGN: Initial retrospective analysis of patients undergoing low energy ablation of the atrioventricular node for refractory atrial flutter (group 1) was followed by a prospective assessment of low energy ablation in the posterio-inferior right atrium for the same condition (group 2). SETTING: Tertiary referral centre for management of cardiac arrhythmias. PATIENTS: Seven men (aged 50-67 years) with refractory atrial flutter. INTERVENTIONS: Multiple (3-10) low energy DC shocks with a cumulative energy of 100-245 J in the region of the atrioventricular node in group 1 and 12-15 low energy DC shocks (cumulative energy 110-235 J) guided by the anatomical landmarks of the triangle of Koch and applied directly to the atrial wall. MAIN OUTCOME MEASURE: Freedom from recurrence of atrial flutter. RESULTS: In group 1 despite initial complete atrioventricular block in three patients, atrioventricular conduction had resumed in all by one month. All four, however, were in sinus rhythm at follow up six to 13 months later. Two of the three patients in group 2 were free of atrial flutter at follow up three to four months after ablation. CONCLUSION: Ablation of the atrial flutter substrate with low energy DC shocks is feasible. Precise electrophysiological mapping is not necessary.

Aged↗
PubMed1991

Transcoronary atrioventricular nodal modification using microvascular collagen.

Surgical and catheter based techniques for atrioventricular (AV) nodal modification have recently been described. Similarly, transcoronary embolization for the treatment of arrhythmias has recently emerged as a potentially useful approach. This report reviews our experience of a novel technique using embolization of the AV node with an inert agent, cross-linked collagen, for the treatment of AV nodal reentrant tachycardia. Three patients with refractory nodal tachycardia received 0.1-0.5 mL cross-linked collagen (2 mg/mL) delivered via a catheter placed within the nodal artery. All developed transient complete AV block with subsequent recovery of conduction. Two patients have had no further tachycardia and were noninducible at restudy. One patient required electrical modification because of recurrent symptoms. One patient sustained a limited posterior infarct due to back-spill of collagen into the distal right coronary artery. This novel technique provides an alternative approach to a cure for AV nodal tachycardia without producing long-term heart block.

Atrioventricular Node↗
PubMed1991

A comparison of intravenous propafenone and flecainide in the treatment of tachycardias associated with the Wolff-Parkinson-White syndrome.

UNLABELLED: We compared the electrophysiological effects of intravenous propafenone and flecainide on accessory pathway conduction by a randomized crossover study in 16 patients with Wolff-Parkinson-White syndrome. The antegrade refractory period of the pathway increased from 256 +/- 18 msec at baseline to 288 +/- 13 msec on propafenone (P less than 0.05) and to 296 +/- 27 msec on flecainide (P = 0.075). The minimum preexcited RR interval during atrial fibrillation or incremental atrial pacing was prolonged from 225 +/- 37 msec to 262 +/- 22 msec by propafenone (P less than 0.05) and to 301 +/- 31 msec by flecainide (P less than 0.005). The prolongation was significantly greater with flecainide than propafenone (P less than 0.05). Both drugs increased tachycardia cycle length (TCL) from 310 +/- 35 msec to 354 +/- 37 msec (propafenone P less than 0.005) and to 352 +/- 37 msec (flecainide P less than 0.01). Both propafenone and flecainide blocked antegrade conduction in the pathway in five patients. Both drugs rendered atrial fibrillation noninducible in seven patients and orthodromic tachycardia noninducible in five patients. CONCLUSIONS: (1) Flecainide causes a greater prolongation of minimum preexcited RR interval than propafenone; (2) There is no significant difference between propafenone and flecainide on the inducibility of arrhythmias, TCL, or incidence of antegrade conduction block.

Adult↗
PubMed1991

Alcohol ablation of atrioventricular conduction.

Transcoronary ablation of atrioventricular conduction by dehydrated alcohol was attempted in 14 patients with refractory atrial arrhythmias. Alcohol (0.5 or 1.0 ml) was delivered after selective catheterisation of the atrioventricular nodal artery in the 10 patients in whom the artery could be identified by cineangiography. The other four patients underwent electrical ablation when the nodal artery could not be catheterised. Temporary atrioventricular block induced by dilute contrast and cold saline (0.9%) confirmed that the catheter was in the correct position before the alcohol was delivered. In all 10 patients complete atrioventricular block developed after alcohol ablation. The block persisted in all four patients given 1.0 ml alcohol but not in four of the six given 0.5 ml. The mean (SD) creatine kinase (MB fraction) at four to six hours after ablation was 76.5 (49.5) IU after 1.0 ml and 75.5 (43.1) IU after 0.5 ml alcohol (normal less than 20 IU). The overall success rate of alcohol ablation in the whole group on an "intention to treat" basis was 43%. The procedure was a technical success in six of the 10 patients in whom the nodal artery was identified. Transcoronary alcohol ablation of atrioventricular conduction should be considered in patients in whom electrical techniques have been unsuccessful.

Aged↗
PubMed1991

Multivariate analysis to simplify the differential diagnosis of broad complex tachycardia.

Univariate analysis has identified several criteria that aid the differential diagnosis of broad complex tachycardia. In this study of 102 consecutive patients multivariate analysis was performed to identify which of 15 clinical and 11 electrocardiographic variables were independent predictors of ventricular tachycardia. These were shown to be a history of myocardial infarction, the QRS waveforms in leads aVF and V1, and a change in axis from sinus rhythm to tachycardia of more than 40 degrees. If none of the criteria was met, the diagnosis was almost certainly supraventricular tachycardia. If one criterion was met the diagnosis was probably supraventricular tachycardia. If two criteria were met then the diagnosis was probably ventricular tachycardia. If three or four criteria were met, the diagnosis was almost certainly ventricular tachycardia. The predictive accuracy was 93%. This was increased to 95% by including two other criteria--definite independent P wave activity and ventricular extrasystoles with the same QRS configuration as that in tachycardia. These criteria were not included in the multivariate analysis because though they were 100% specific they were seldom seen. These four criteria can be used as simple rules in determining the origin of a broad complex tachycardia.

Diagnosis, Differential↗
PubMed1991

Dynamics of ventricular repolarisation in the congenital long QT syndromes.

Patients with congenital QT interval prolongation are at risk of ventricular arrhythmias and sudden death. It has been suggested that the susceptibility to arrhythmias in these syndromes may be related to the abnormal dynamics of ventricular repolarisation. The dynamics of ventricular repolarisation, including assessment of the effect of changing heart rate on the QT interval and the duration of the right ventricular monophasic action potential, were studied in eight patients with congenital long QT syndromes. The effects of altered sympathetic tone on these dynamics were investigated with isoprenaline, propranolol, and left stellate ganglion block. The rate adaptation of the QT interval was abnormal in only a few patients and in some patients this feature may be related to the severity of the condition. These abnormalities may be exaggerated by isoprenaline and lessened by propranolol and left stellate ganglion block. Monophasic action potential dynamics were normal in all patients. The hypothesis that impaired QT rate adaptation may play a role in the genesis of ventricular arrhythmias in these syndromes is not, in general, supported by the present data. However, in patients with impaired adaptation the normalisation of QT dynamics after beta blockade and left stellate ganglion block was consistent with the efficacy of these forms of treatment.

Action Potentials↗
PubMed1990

Relative efficacy and safety of intravenous drugs for termination of sustained ventricular tachycardia.

The relative safety and efficacy of intravenous administration of adenosine, lignocaine, disopyramide, flecainide, and sotalol for termination of stable, induced ventricular tachycardia was assessed in serial trials. Ventricular tachycardia was terminated by pacing if it persisted 10-15 min after the end of drug administration. 24 patients with recurrent ventricular tachycardia were studied. Ventricular tachycardia was terminated by a drug in 35 of 105 trials. In 6 patients no drug terminated the arrhythmia. Adenosine did not terminate tachycardia or have any serious adverse effect in any patient; both flecainide and disopyramide were significantly more effective than lignocaine, but flecainide had significantly more severe adverse effects than lignocaine. Lignocaine was the safest drug and should continue to be used as first-line drug therapy for stable ventricular tachycardia. Disopyramide should be considered as second-line treatment. DC cardioversion is necessary for unstable ventricular tachycardia, and its availability must be ensured before attempted pharmacological intervention.

Adenosine↗
PubMed1990

Effect of activation sequence on ventricular refractoriness as determined by extrastimuli.

STUDY OBJECTIVE: The aim was to determine by the extrastimulus method the effect on the right and left ventricular effective refractory periods of moving the site of the pacing train away from the site of the extrastimulus. DESIGN: The ventricular effective refractory period was measured at the right and left ventricular apices using pacing trains at two heart rates, delivered to the ipsilateral ventricle, the contralateral ventricle, and the right atrium. SUBJECTS: Seven patients (six male), mean age 52 years (range 26-75 years), with either documented (six) or suspected (one) ventricular tachycardia were studied. Four had ischaemic heart disease and the remaining three had morphologically normal hearts. MEASUREMENTS AND MAIN RESULTS: The pacing train and extrastimulus delivered in the right ventricle produced the shortest effective refractory period at both heart rates: 220.8(SD 19) ms and 207.9(16) ms respectively. As the pacing train was moved to the right atrium, the effective refractory period lengthened to 246.4(22) ms and 219.3(20) ms at the two heart rates. There was further lengthening as the site of the pacing train was moved to the left ventricle, to 269.2(20) ms and 240.7(35) ms respectively. The same pattern was observed in the left ventricular effective refractory periods as the pacing train was moved from left ventricle to right ventricle and to right atrium. CONCLUSIONS: The ventricular effective refractory period lengthens as the site of the pacing train is moved away from the site of the extrastimulus. This may be explained by the effects of the distribution of the pacing energy within the myocardium and by intercellular electrotonic interactions. This has important clinical implications for the arrhythmogenic mechanisms of ventricular tachyarrhythmias.

Adult↗