Biomedical subjects

Z A Syed

Publications and source records attributed to Z A Syed.

4 recordsLinked to original sources

PubMed2001

Conversion of atrial fibrillation by the experimental antiarrhythmic drug tedisamil in two canine models.

INTRODUCTION: Tedisamil is an experimental bradycardic agent possessing action potential-prolonging effects. It has been proven effective in terminating ventricular arrhythmias in several animal models and atrial flutter in a conscious dog model. There are no reports to date evaluating tedisamil's efficacy in terminating atrial fibrillation (AF). METHODS AND RESULTS: Two different canine models of AF were used. One group of dogs (n = 6) was subjected to 28 days of chronic fibrillatory pacing at 50 Hz using an implantable neural stimulator. Sustained AF was achieved in all dogs within 14 days of initiating pacing. A second set of dogs (n = 5) had AF induced via bilateral vagal stimulation. Tedisamil 1 mg/kg was 100% effective in terminating AF in both models. Cardioversion was associated with a statistically significant prolongation of the fibrillatory cycle length immediately before return to normal sinus rhythm in both models. A dose-response trial was performed in the vagal AF group as well as in a second group of three dogs that underwent chronic fibrillatory pacing. The efficacy of tedisamil was dose dependent, with limited efficacy at 0.1 and 0.3 mg/kg intravenously in both models. Tedisamil was able to prevent reinduction of sustained AF 30 minutes after administration of 1 mg/kg in the chronic pacing model in all dogs. Side effects included minor hypersalivation in most dogs receiving the 1 mg/kg dose. No ventricular ectopy or arrhythmias were observed. CONCLUSION: Tedisamil is effective for conversion of sustained AF to normal sinus rhythm in two different models of AF.

Animals↗

PubMed2001

Harmonic scalpel tonsillectomy versus electrocautery tonsillectomy: a comparative pilot study.

OBJECTIVE: Using quality of life criteria, this pilot study prospectively evaluates if the ultrasonic dissector coagulator's (Harmonic Scalpel [HS], Ethicon Endo-Surgery, Inc, Cincinnati, OH) unique properties offer advantages over traditional electrocautery (EC) tonsillectomies with respect to return to regular diet, activity, and complications such as bleeding and dehydration. METHODS: Over a 13-month period, 316 tonsillectomies (161 EC and 155 HS) were evaluated. Return to regular diet, regular activity, and the use of postoperative pain medications were monitored via a brief questionnaire. Complications, such as increased perioperative and postoperative bleeding, were monitored by chart review. Statistical analysis of the questionnaire data was performed. RESULTS: Seventy-five (46.6%) of the patients in the EC group responded versus 97 (62.6%) in the HS group. The ages ranged from 1 to 19 years old. Return to regular diet in 24 hours was statistically significant when comparing HS and EC questionnaire responders, 44.3% versus 22.7%, respectively; as was 72 hours, HS (74.2%) and EC (46.7%). Twenty-eight percent of the HS questionnaire responders versus 12% of EC resumed normal activity within 24 hours. The perioperative blood loss was equal in the 2 groups. There were 14 late bleeds; 9 were EC patients and 5 HS patients. Two HS patients and 4 EC patients had readmissions for dehydration. CONCLUSIONS: It appears from this early pilot study that the Harmonic Scalpel tonsillectomy offers advantages of early return to diet and activity over standard electrocautery tonsillectomies. We report no difference in perioperative or postoperative bleeding.

Adolescent↗

PubMed1998

Effect of isoproterenol on QRS complex morphology during ventricular pacing: implications for pace mapping.

Ventricular pace mapping may be used to identify the site of origin of idiopathic ventricular tachycardia. Isoproterenol is often required to induce this type of ventricular tachycardia, but its effect on QRS morphology during pace mapping is unknown. Therefore, this study was performed to evaluate the effect of isoproterenol on QRS morphology during ventricular pacing. The study population consisted of 20 patients (mean age 38 +/- 14 years) undergoing a clinically indicated electrophysiology procedure. Ventricular overdrive pacing was performed in trains of 12 stimuli at cycle lengths of 400, 350, 300, and 250 ms, first in the baseline state during an infusion of isoproterenol, and again after isoproterenol washout. Pacing was performed at the right ventricular apex in 10 patients, in the right ventricular outflow tract in 6 patients, and in the left ventricle in 4 patients. Visual evaluation revealed no apparent effects of isoproterenol on QRS morphology at any of the three pacing sites or at any of the pacing cycle lengths. It was concluded that QRS morphology during ventricular pacing is not affected by isoproterenol infusion. Therefore, in patients with idiopathic ventricular tachycardia, even if the induction of tachycardia requires infusion of isoproterenol, successful pace mapping may be performed in its absence.

Aged↗

PubMed1998

Changes in cardiac repolarization following short periods of ventricular pacing.

INTRODUCTION: "Cardiac memory" (primary T wave change) is thought to occur after 15 minutes to several hours of right ventricular (RV) pacing. The two components of the temporal change in repolarization are memory and accumulation. The purpose of this study was to examine quantitatively the effect of short periods of ventricular pacing on the human cardiac action potential, using monophasic action potential (MAP) recordings. METHODS AND RESULTS: Thirty-one patients (ages 43+/-14 years) with structurally normal hearts undergoing a clinically indicated electrophysiologic procedure were enrolled. Catheters were placed in the right atrium (RA) and RV, and a MAP catheter was positioned at the RV septum. APD90 was calculated from digitized MAP recordings. MAP morphology comparisons were performed using the root mean square (RMS) of the difference between complexes. All pacing was at 500-msec cycle length. There were four pacing protocols: (1) RA pacing was performed for approximately 15 minutes to evaluate temporal stability of the MAP recordings (5 pts); (2) to evaluate the memory phenomenon, four successive 1-minute episodes of RV pacing were interspersed with 2 minutes of RA pacing (5 pts); (3) the accumulation phenomenon was evaluated by assessing the effects of 1, 5, 10, and 15 minutes of RV pacing on the MAP during RA pacing (16 pts); and (4) 20 minutes of RV pacing was followed by 10 minutes of RA pacing to correlate visually apparent T wave changes with changes in MAP recordings (5 pts). In the control patients, no changes in APD90 or RMS analysis were noted during 14.9+/-1.4 minutes of RA pacing. In the second protocol, RMS of the difference between the baseline MAP complexes and the signal average of the first 50 beats following each of four 1-minute RV pacing trains demonstrated progressively greater differences in morphology after successive episodes of RV pacing. In protocol 3, RMS analysis identified a progressively greater difference between the baseline MAP recording and the average of the first 50 beats after 1, 5, 10, and 15 minutes of RV pacing. In protocol 4, visually apparent changes in T waves occurred in parallel with the RMS of the difference between the baseline MAP recordings and the average of the first 50 beats after 20 minutes of RV pacing. Similar changes also were demonstrated by APD90 analysis. CONCLUSION: This study is the first to demonstrate that episodes of abnormal ventricular activation as short as 1 minute in duration may exert lingering effects on the repolarization process once normal ventricular activation resumes.

Action Potentials↗