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Biomedical subjects

Y Bashir

Publications and source records attributed to Y Bashir.

At least 19 recordsLinked to original sources
PubMed2001

A simplified approach to temporary DDD pacing using a single lead, balloon-tipped catheter with overlapping biphasic impulse stimulation.

Temporary DDD pacing offers significant hemodynamic benefits in emergency management of bradyarrhythmias but is underused because of its complexity (two leads) and unreliability. Single lead VDD pacing with atrial sensing via a floating dipole is feasible, but atrial pacing is limited by high thresholds and phrenic nerve stimulation (PNS). Overlapping biphasic impulse (OLBI) stimulation may avoid these problems. The authors designed a single lead balloon-tipped catheter for temporary transvenous DDD pacing, incorporating noncontact atrial dipoles for OLBI stimulation. This catheter was deployed using fluoroscopic guidance in 74 patients (43 men, 31 women) with mean age 56.9 +/- 17.0 years. Pacing parameters were assessed at implantation and follow-up. The median procedural time was 6.6 (range 1.2-25.0) minutes and fluoroscopy time 1.9 (range 0.2-7.8) minutes. Stable VDD pacing was achieved in all cases. Atrial capture was achieved in 73 of 74 cases with both modes at maximum output but was restricted by PNS at outputs below atrial capture threshold in 3 of 74 cases with OLBI and 10 of 74 cases with standard bipolar mode (P = 0.04). At outputs > or = 1.0 V above atrial threshold, reliable DDD pacing without PNS was achieved and maintained in 67 (91%) of 74 patients in OLBI compared to 53 (72%) of 74 patients in bipolar mode (P = 0.003). Pacing parameters were stable during follow-up (median 53 hours, range 6-168 hours). In conclusion, the single lead catheter with OLBI stimulation allows temporary VDD and DDD pacing without PNS to be achieved in > 90% of patients. This rapid and convenient approach should facilitate DDD pacing in emergency settings.

Cardiac Pacing, Artificial↗
PubMed1997

Effect of magnesium sulphate in patients with unstable angina. A double blind, randomized, placebo-controlled study.

AIMS: Administration of intravenous magnesium sulphate has been shown to be protective during acute myocardial ischaemia and it may therefore have beneficial effects in unstable angina. The purpose of this study was to assess the effects of a 24-h infusion of magnesium in patients with unstable angina. METHODS AND RESULTS: Patients who presented with unstable angina with electrocardiographic changes were randomized to receive a 24-h intravenous infusion of magnesium or placebo within 12 h of admission. The primary endpoint was myocardial ischaemia, as assessed by 48 h Holter monitoring. Resting 12-lead ECGs, creatine kinase-MB release and urinary catecholamines were also assessed. Patients were followed for 1 month. Thirty-one patients received magnesium sulphate and 31 placebo. Baseline characteristics and extent of coronary disease were similar in both groups. On 48 h Holter monitoring, 14 patients (50%) had transient ST segment shifts in the magnesium group vs 12 patients (46%) in the placebo group. However, there were fewer ischaemic episodes in the magnesium group (51 vs 101, P < 0.001) and there was a trend towards an increase in the total duration of ischaemia in the placebo group compared to the magnesium group in the second 24 h (2176 min vs 719 min respectively, P = 0.08). Regression of T wave changes on the 24 h ECG occurred more frequently in patients who received magnesium compared to those treated with placebo (11 patients vs 0 patients respectively, P < 0.005). Creatine kinase-MB release was significantly less at 6 and 24 h in patients who received magnesium compared to those treated with placebo. Catecholamine excretion was lower in patients treated with magnesium than in those treated with placebo (adrenaline: 1.05 +/- 0.16 vs 1.61 +/- 0.32 ng.mmol-1 creatinine; noradrenaline: 9.99 +/- 1.82 vs 18.48 +/- 2.41 ng.mmol-1 creatinine respectively in the first 12 h sample, P < 0.05). CONCLUSIONS: Intravenous magnesium reduces ischaemic ECG changes, creatine kinase-MB release and urinary catecholamine excretion in the acute phase of unstable angina. Thus, magnesium may be a beneficial additional therapy for these patients. Further studies are required to confirm these finding.

Adult↗
PubMed1997

Cardiac catheterisation performed by a clinical nurse specialist.

OBJECTIVE: To establish the feasibility and safety of an appropriately trained clinical nurse specialist performing diagnostic cardiac catheterisation. DESIGN: Non-randomised retrospective comparison between the first 100 and second 100 consecutive investigations by a clinical nurse specialist and 200 consecutive patients investigated by two cardiology registrars over a similar period. SETTING: Regional cardiac centre performing 3200 catheterisation procedures per annum. PATIENTS: 200 patients undergoing routine (non-emergency) cardiac catheterisation for investigation of ischaemic heart disease. MAIN OUTCOME MEASURES: Procedural complications, image quality, fluoroscopy times. RESULTS: Satisfactory diagnostic images in all nurse specialist cases with no deaths and two complications (coronary artery dissection and femoral pseudoaneurysm). Procedure duration and fluoroscopy times slightly shorter for clinical nurse specialist by 3 and 1.6 minutes, respectively (P < 0.05). CONCLUSIONS: Non-medical practitioners can be trained to perform straightforward cardiac angiography in low risk patients with consultant supervision, as for cardiology registrars. With important restrictions such posts may have a limited role in supporting future consultant based services.

Aged↗
PubMed1996

Effect of magnesium on the monophasic action potential during early ischemia in the in vivo human heart.

OBJECTIVES: This study sought to examine the effects of magnesium on epicardial action potential duration in patients during early myocardial ischemia. BACKGROUND: Magnesium has been shown to reduce arrhythmias in experimental models of myocardial ischemia. Experimental and clinical observations suggest an effect on repolarization. METHODS: Patients undergoing elective coronary artery bypass surgery were randomized (double blind) to receive intravenous magnesium (n = 10) or placebo (n = 10). Patients were placed on cardiopulmonary bypass and paced at 600 ms, and stable monophasic action potentials were obtained. Ischemia was achieved by aortic cross-clamping for 2 min while normothermia was maintained. RESULTS: Serum magnesium levels increased from 0.60 +/- 0.03 to 1.69 +/- 0.07 mmol/liter (mean +/- SEM) in the magnesium group, with no change in the placebo group. Epicardial temperature was identical in the two groups and did not alter during ischemia. At 90% repolarization, initial action potential prolongation was observed in the placebo group over the first minute of ischemia (282.0 +/- 6.0 to 294.0 +/- 4.8 ms) but not in the magnesium group (278.3 +/- 5.9 to 274.5 +/- 7.4 ms). At 2 min of ischemia, action potential duration was shorter in the magnesium group than in the placebo group (258.1 +/- 5.5 vs. 281.3 +/- 5.9 ms, respectively, p < 0.05). CONCLUSIONS: Intravenous magnesium infusion altered the epicardial action potential response to ischemia in patients. These findings may have important implications in the pathogenesis of arrhythmias in ischemic myocardium.

Action Potentials↗
PubMed1995

Electrophysiologic profile and efficacy of intravenous dofetilide (UK-68,798), a new class III antiarrhythmic drug, in patients with sustained monomorphic ventricular tachycardia. Dofetilide Arrhythmia Study Group.

There is increasing evidence that class III antiarrhythmic agents may be superior to class I agents for the long-term treatment of life-threatening ventricular tachyarrhythmias. This open study evaluated the acute electrophysiologic effects, antiarrhythmic efficacy, and safety of different doses of intravenous dofetilide, a new class III drug, in 50 patients with sustained monomorphic ventricular tachycardia inducible by programmed electrical stimulation who had previously been unsuccessfully treated with 0 to 7 (median 3) other drugs. Intravenous dofetilide was administered over 60 minutes at the following dose levels: 1.5, 3.0, 6.0, 9.0, and 15.0 micrograms/kg. Significant class III activity was apparent at doses of 3.0 to 15.0 micrograms/kg, as evidenced by dose-related prolongation of the QTc interval by 13.4% to 14.2%, ventricular effective refractory period by 7.9% to 20.6%, and ventricular functional refractory period by 7.3% to 25.0%. The corresponding mean +/- SD plasma dofetilide concentrations ranged from 1.45 +/- 0.52 to 6.48 +/- 1.31 ng/ml. There was no evidence of reverse use-dependence. At these electrophysiologically active dose levels, intravenous dofetilide suppressed (complete response) or slowed (partial response) inducible ventricular tachycardia in 17 of 41 patients (41%) compared with 0 of 9 patients receiving only 1.5 micrograms/kg. The response rate was fairly uniform among the groups receiving 3.0, 6.0, 9.0, and 15.0 micrograms/kg. Intravenous dofetilide was hemodynamically well tolerated. Torsades de pointes (which was self-limiting) developed in only 1 patient, who was allocated to receive 15.0 micrograms/kg. There were no other proarrhythmic episodes or serious adverse effects. Further evaluation of the therapeutic potential of dofetilide in the management of life-threatening ventricular arrhythmias is justified.

Aged↗
PubMed1995

Influence of the infarct site on the identification of patients with ventricular tachycardia after myocardial infarction based on the time-domain and spectral turbulence analysis of the signal-averaged electrocardiogram.

In a significant proportion of patients with sustained ventricular tachycardia (VT) following anterior myocardial infarction, the areas of slow conduction are activated early during cardiac depolarization. Therefore, they may not be detected by the standard time-domain analysis of the signal-averaged electrocardiogram (SAECG) which is limited to the terminal part of the QRS complex. Spectral turbulence analysis of the SAECG is a new frequency domain technique which examines the whole QRS complex and may improve identification of patients with sustained VT following anterior infarction. We compared the results of time-domain and spectral turbulence analyses of the SAECG in 53 postinfarction patients with sustained VT and in 53 age-, gender- and infarct site-matched patients without VT. The receiver operator characteristic curves have shown that the time-domain analysis resulted in better identification of patients with VT following inferior than following anterior infarction (e.g., at the sensitivity level of 90%, the corresponding values of specificity were 96 and 90%, respectively), whereas the spectral turbulence analysis performed better in the anterior site of infarction. When both time-domain and spectral turbulence analyses were combined, the accuracy of the SAECG for identification of patients with VT following anterior infarction improved, reaching a specificity of 97% at the sensitivity level of 90%. In conclusion (1) spectral turbulence analysis of the SAECG results in better identification of patients with VT following anterior than following inferior infarction, and (2) the combination of time-domain and spectral turbulence analyses of the SAECG may improve identification of patients with VT following anterior infarction.

Aged↗
PubMed1994

Localization of accessory pathways from the 12-lead electrocardiogram using a new algorithm.

A new algorithm (St. George's algorithm), based on the polarity and morphology of QRS complexes rather than delta waves, was developed for localizing accessory pathways to 1 of 9 sites on the atrioventricular annuli. This was compared with algorithms previously proposed by Skeberis et al (localizing to 1 of 7 sites) and Milstein et al (localizing to 1 of 4 sites). The preexcited 12-lead electrocardiograms recorded during sinus rhythm in 106 consecutive patients (including 60 retrospectively analyzed patients and 46 prospectively analyzed patients) who underwent successful radiofrequency catheter ablation of a single accessory pathway were analyzed by 3 blinded observers using all 3 algorithms. The results were compared with the actual localization of accessory pathways as derived from endocardial mapping during catheter ablation. In all 106 patients, the accuracy of the 3 algorithms for 4 sites on the atrioventricular annuli (as considered by Milstein's method) was 72%, 79%, and 92% for Milstein's, Skeberis', and St. George's algorithms, respectively. For 7 sites (as considered by Skeberis' method), the accuracy was 65% (Skeberis' algorithm) and 88% (St. George's algorithm), and for 9 sites (as considered by our method) the accuracy was 86% (St. George's algorithm). In 46 prospectively analyzed patients, the accuracy of the 3 algorithms for 4 sites was 70% (Milstein's), 67% (Skeberis'), and 87% (St. George's); for 7 sites the accuracy was 61% (Skeberis') and 85% (St. George's), and for 9 sites the accuracy was 85% (St. George's). The reproducibility of St. George's and Skeberis' methods was better than that of Milstein's method.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1994

Radiofrequency ablation of accessory pathways: implications of accumulated experience and time dedicated to procedures.

Previous reports on radiofrequency ablation of accessory pathways have shown that the experience of the operator is of crucial importance in reducing fluoroscopy time and achieving higher success rates. However, a detailed analysis of this important issue has not been previously attempted. We analysed 71 consecutive ablation procedures undertaken at St George's Hospital by the same electrophysiology group and always with the same first operator. Of all procedures, 66 (91.6%) were successful, as judged by abolition of accessory pathway conduction without recurrence within the next 24 h. Failures included two out of 38 left-sided pathway procedures (5.3%), one out of 11 intermediate septal (9.1%) and four out of 22 right-sided pathway procedures (18.2%). These differences were not statistically significant. Average procedure and screening times for all procedures were 162.9 +/- 86.0 min and 56.8 +/- 48.2 min respectively, whereas the median of the number of discharges was 12, ranging from one to 51. There was no significant difference between pathway groups or between concealed and non-concealed pathways in respect to procedure and screening time or number of discharges. There was a significant tendency towards decreased procedure and screening times with accumulating experience and this was similar for all pathway groups. There was also a tendency towards improved cumulative success rates with time dedicated to procedures. We conclude that a certain amount of ablation experience is required, even by experienced electrophysiologists, before a relatively high success rate without long radiation exposure can be achieved, regardless of the location or the mode of conduction of the pathway.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗