Duplex polymerase chain reaction-restriction fragment length polymorphism assay for rapid detection of HFE mutations-C282Y occurs with a low frequency in Tehran's population.
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Cysteine↗
Biomedical subjects
M Jazayeri
Publications and source records attributed to M Jazayeri.
HBV core sequence: definition of genotype-specific variability and correlation with geographical origin.
There are eight genotypes and nine subtypes of HBV. Small differences in geographical origin are associated with sequence changes in the surface gene. Here, we compared core gene sequences from different genotypes and geographical regions. Specific combinations of 24 amino acid substitutions at nine residues allowed allocation of a sequence to a subtype. Six of these nine residues were located in different T cell epitopes depending on HBV geographical area and/or genotype. Thirty-seven nucleotide changes were associated uniquely with specific genotypes and subtypes. Unique amino acid and nucleotide variants were found in a majority of sequences from specific countries as well as within subtype ayw2 and adr. Specific nucleotide motifs were defined for Korean, Indian, Chinese, Italian and Pacific region isolates. Finally, we observed amino acid motifs that were common to either South-east Asian or Western populations, irrespective of subtype. We believe that HBV strains spread within constrained ethnic groups, result in selection pressures that define sequence variability within each subtype. It suggests that particular T cell epitopes are specific for geographical regions, and thus ethnic groups; this may affect the design of immunomodulatory therapies.
Amino Acid Sequence↗
Antepartum and postpartum Papanicolaou smears. Are they both necessary?
OBJECTIVE: To determine if a Papanicolaou smear performed during pregnancy needs to be repeated at the postpartum visit. STUDY DESIGN: A retrospective chart review was performed on women who received prenatal care from our obstetric clinic and returned for a postpartum visit. All pregnant women who had both a Papanicolaou smear in pregnancy and another at the postpartum visit, about six weeks after delivery, were included. Six hundred one patients were studied who had complete records between 1995 and 1996. RESULTS: The average length of time between the two smears was 209 days. With the exception of a lower frequency of the presence of endocervical cells in the antepartum Papanicolaou smears, there were no differences between the distribution of Papanicolaou smear results. In patients without risk factors and a normal antepartum Papanicolaou smear, the prevalence of squamous intraepithelial lesion on the postpartum smear was very low (4 in 1,000). CONCLUSION: In patients without risk factors for cervical intraepithelial neoplasia and a normal Papanicolaou smear in pregnancy, a Papanicolaou smear should be repeated at the recommended yearly interval.
Adult↗
Urine protein dipstick measurements. A screen for a standard, 24-hour urine collection.
OBJECTIVE: To determine if the sum of urine protein dipstick values recorded during every void can be used to screen for patients who need a standard, 24-hour urine collection for determination of protein excretion. STUDY DESIGN: Thirty inpatient and 17 outpatient pregnant women undergoing 24-hour urine collection for protein concentration were enrolled. The volume, dipstick protein values and time of void were recorded. The 24-hour quantitative analysis of protein excretion performed by the laboratory was compared to the 24-hour sum of the products of each voided volume and dipstick value (dipstick factor). RESULTS: The dipstick factor significantly correlated with the total 24-hour protein excretion (correlation coefficient 0.84, P < 1 x 10(-7)). A dipstick factor of > or = 300 mg, indicated proteinuria with a sensitivity of 96%, specificity of 90%, positive predictive value of 92% and negative predictive value of 95%. Separately, we found differences in the amount of protein excretion when the 24-hour period was divided into six 4-hour periods, using analysis of variance. Paired t test analysis of the mean protein excretion from 16:00 to 04:00 showed significantly higher results than did the protein excretion from 04:01 to 16:00 (1,197 +/- 356 mg vs. 674 +/- 158 mg, P < .0001). CONCLUSION: The sum of dipstick factors in a 24-hour period is a reliable screening test for identifying patients who need the standard laboratory test for proteinuria.
Adult↗
Catheter-based internal atrial defibrillation: efficacy, safety and tolerance. Clinical experiences with implantable devices.
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Atrial Fibrillation↗
Unmasking the trifascicular left intraventricular conduction system by ablation of the right bundle branch.
Twenty-five patients underwent transcatheter right bundle ablation either for bundle branch reentrant tachycardias or inadvertent or deliberate right bundle ablation during atrioventricular junctional ablation for rate control. Electrophysiologic data and 12-lead electrocardiograms before and after right bundle ablation were available in all patients. Eleven of the patients had no significant intraventricular conduction abnormalities by surface electrocardiograms (group I), whereas 14 patients had underlying intraventricular conduction delays (group II). All group I patients had typical electrocardiographic changes of right bundle branch block after right bundle ablation, with minimal changes in initial or mean QRS axis. In group II, 5 patients had an initial 40 ms QRS axis shift of > 45 degrees, in 7 patients the mean QRS axis changed significantly (leftward in 4 and rightward in 3), and a qR pattern in V1 was seen in 12 of 14 patients including 2 with structurally normal hearts. These changes, namely new Q waves, and rightward and leftward axis shifts are most likely the result of septal fascicular, left posterior fascicular, and left anterior fascicular delay/block, which were exposed by exclusive conduction via a diseased left bundle and its fascicles. The trifascicular nature of left intraventricular conduction is more apparent when diseased and unmasked by concomitant block in the right bundle branch.
Aged↗
Distribution of atrial electrogram types during atrial fibrillation: effect of rapid atrial pacing and intercaval junction ablation.
OBJECTIVES: This study examined the anatomic distribution types and possible determinant of atrial electrogram types during atrial fibrillation. BACKGROUND: Different types of atrial electrograms during atrial fibrillation have been observed and classified, but their anatomic distribution patterns, determinants and potential usefulness in guiding future catheter ablation are unknown. METHODS: Two animal models of atrial fibrillation were used: the sterile pericarditis model (n = 10) and the rapid atrial pacing model (400 beats/min for 6 weeks, n = 6). The atrial electrogram of atrial fibrillation and the atrial effective refractory period were obtained from multiple sites of the right and left atrium. In addition, decremental rapid atrial stimulation was applied to the site of shortest and longest atrial effective refractory periods until atrial fibrillation induction in a subgroup of nine dogs. Ablation of the intercaval junction was performed using the radiofrequency catheter technique in dogs with atrial fibrillation duration > 1 min. RESULTS: In both models, organized atrial electrograms (type I) were predominantly observed at the left atrial sites and the right atrial appendage, whereas disorganized atrial electrograms (type III) were mainly observed at the right posterolateral atrium. The distribution of the atrial electrogram types closely followed that of the atrial effective refractory period, with the shortest atrial effective refractory period corresponding to organized atrial electrograms (type I) and the longest atrial effective refractory period corresponding to disorganized atrial electrograms (type III). The correlation of atrial electrogram type with the atrial effective refractory period was further demonstrated by the effect of rapid atrial stimulation. When rapid atrial stimulation was applied to the site with the shortest atrial effective refractory period, disorganized atrial electrograms were observed at sites with the longest atrial effective refractory period, whereas 1:1 atrial capture was still present at the stimulation site. Ablation of the intercaval junction made atrial fibrillation noninducible or tended to shorten the atrial fibrillation duration (from 26.4 +/- 24.2 to 8.8 +/- 22.6 min in the pericarditis group, p = 0.02, and from 33.7 +/- 29.2 to 12.1 +/- 23.8 min in the rapid pacing group, p = 0.09) but did not change the atrial electrogram types during atrial fibrillation. CONCLUSIONS: Various types of atrial electrograms are present at different locations during atrial fibrillation. The atrial electrogram characteristics of atrial fibrillation at a specific location are related to the atrial effective refractory period, with short effective refractory periods associated with organized atrial electrograms and long effective refractory periods associated with disorganized electrograms.
Animals↗
Sudden death in patients with implantable cardioverter-defibrillators.
UNLABELLED: Of the 733 patients with implantable cardioverter-defibrillators (ICDs) from 1982 to 1995 in our center, 20 died suddenly while the ICD was activated. This number included 16 men and four women with a mean age of 60 +/- 8 years and ejection fractions of 24.2% +/- 8.6%. ICDs were implanted for drug refractory ventricular tachycardia (VT) in 13 patients and for resucitated cardiac arrest in seven patients. The clinical VT was associated with syncope in 7 of 13 patients. VT was induced in 18 patients and was hemodynamically unstable in 12 patients. Shock therapies associated with syncope were delivered in 7 of 15 patients during the follow-up. This subgroup of patients survived a median of only 18 months after ICD implant. Ventricular fibrillation-defibrillation was found to surround death in nine patients. CONCLUSIONS: (1) Sudden death victims of the ICD population are characterized by poor left ventricular function and hemodynamically unstable ventricular tachyarrhythmias. (2) Ventricular tachyarrhythmias are the major cause of sudden death in ICD patients.
Aged↗
Relative efficacy of different tilts with biphasic defibrillation in humans.
OBJECTIVE: The goal of this study was to assess if tilt bears any impact on defibrillation efficacy of biphasic shocks. BACKGROUND: Although it has been shown that biphasic waveform may increase the defibrillation efficacy, this pulsing method has not been as extensively studied in patients, and information regarding the effect of different tilts is lacking. METHODS: This study consisted of two similar but distinct protocols including 33 patients undergoing transvenous defibrillator implant. In 17 patients (Part I) defibrillation threshold was obtained delivering biphasic waveforms with 50%, 65%, and 80% tilt in random fashion. Similarly, in 16 patients (Part II) testing of biphasic waveform with 40%, 50%, and 65% tilt was performed in random order. The electrode system used consisted of two transvenous leads and a subcutaneous patch in all 33 patients. RESULTS: In Part I, tilt of 50% demonstrated a defibrillation threshold significantly lower than 65% tilt (7.5 +/- 4.3 J vs 9.7 +/- 5.0 J; P = 0.04) and 80% tilt (7.5 +/- 4.3 J vs 11.7 +/- 5.9 J; P < 0.01). Similarly, 65% tilt provided a lower defibrillation threshold than 80% tilt (9.7 +/- 5.0 J vs 11.7 +/- 5.9 J; P = 0.02). In Part II, no significant difference was observed in terms of defibrillation threshold between 40% tilt and the two tilts of 50% and 65%. However, as in Part I, 50% tilt provided a significant reduction of the energy to defibrillate as compared to 65% tilt (6.3 +/- 3.6 J vs 9.0 +/- 4.8 J; P < 0.01). The 50% tilt resulted in better defibrillation efficacy than 65% tilt independent of the lead system used for testing (Medtronic Transvene and CPI Endotak-C). CONCLUSIONS: Biphasic shocks with 50% tilt required less energy for defibrillation than 40%, 65%, and 80% tilts. However, in the clinical setting a programmable tilt may be preferable to account for some patient-to-patient variability.
Adult↗
Facilitation of sustained bundle branch reentry by atrial fibrillation.
An electrophysiologic evaluation was performed in a patient with an idiopathic dilated cardiomyopathy and syncope. Ventricular tachycardia was not inducible despite the use of a variety of pacing maneuvers during sinus rhythm. Only after the electrical induction of atrial fibrillation did sustained bundle branch reentrant tachycardia (with both right and left bundle branch block QRS configurations) spontaneously occur and become reproducibly induced during right ventricular pacing. Ablation of the right bundle branch eliminated reproducibility of the tachycardia.
Aged↗
Provocation of hypotension during head-up tilt testing in subjects with no history of syncope or presyncope.
BACKGROUND: Head-up tilt test is increasingly being used to evaluate patients with syncope. This study was designed to evaluate the specificity of head-up tilt testing using different tilt angles and isoproterenol infusion doses in normal volunteers with no prior history of syncope or presyncope. METHODS AND RESULTS: One hundred fifty volunteers were randomized to two groups of 75 each. In group 1, subjects were further randomized to have head-up tilt testing at a 60, 70, or 80 degree angle at baseline followed by repeat tilt testing during a low-dose isoproterenol infusion that increased the heart rate by an average of 20%. In group 2, after having a baseline head-up tilt test at a 70 degree angle for a maximum of 20 minutes, subjects were randomized to have a repeat tilt table testing at a 70 degree angle during a low-dose, 3 micrograms/min, or 5 micrograms/min isoproterenol infusion. In group 1, syncope or presyncope along with hypotension developed in 2 subjects during the baseline test at 60 and 70 degrees of tilt and in 5 subjects during tilting at 80 degrees. The addition of low-dose isoproterenol reduced the specificity minimally from 92% to 88% at both 60 and 70 degrees of tilt but substantially to 60% at an 80 degrees angle. However, 6 of the 10 subjects with a positive test at an 80 degree angle had an abnormal response after 10 minutes of tilt testing. In group 2, using various isoproterenol doses with tilt table testing at a 70 degree angle, low-dose (mean infusion dose, 1.5 +/- 0.45 microgram/min), 3 micrograms/min, and 5 micrograms/min isoproterenol infusions elicited an abnormal response in 1 (4%), 5 (20%), and 14 (56%) of the subjects, respectively. Using multiple logistic regression analysis, head-up tilt testing at an 80 degree angle (P = .01) or during 3 micrograms/min (P = .02) and 5 micrograms/min isoproterenol infusion rates (P < .001) was the most significant predictor of an abnormal response. CONCLUSIONS: Head-up tilt testing at a 60 or 70 degree angle with or without low-dose isoproterenol infusion provides an adequate specificity. Caution is needed, however, in interpreting the results if the head-up tilt test at 80 degrees is extended beyond 10 minutes or if high doses of isoproterenol are used.
Adult↗
Termination of atrioventricular nodal reentrant tachycardia by premature stimulation from ablating catheter. A reliable guide to identify site for slow-pathway ablation.
BACKGROUND: Slow-pathway ablation is currently used more frequently to control atrioventricular nodal reentrant tachycardia (AVNRT). However, in patients with the common type of AVNRT, successful ablation of the slow pathway can be difficult and time-consuming. We tested a simple method to predict a site for slow-pathway ablation in patients with AVNRT of the common variety. METHODS AND RESULTS: Twenty patients with symptomatic common AVNRT (13 women and 7 men; mean age, 41 +/- 21 years) were included in the study. Once the AVNRT had a stable cycle length (+/- 10 ms) for at least 20 cycles, single extrastimuli were delivered from the ablating catheter tip beginning with 20 ms less than the tachycardia cycle length and decrementing by 10 ms until tachycardia terminated or loss of capture occurred at the pacing site. The pacing protcol was performed systematically in a stepwise fashion at four adjacent sites starting from the posterior/inferior interatrial septum near the tricuspid annulus and moving progressively more anteriorly. The pacing protocol was then repeated in the same sequence, followed by delivery of radiofrequency current at each site to determine its effect at sites where AVNRT could not be terminated with a pacing protocol. AVNRT could be terminated in the anterograde direction from at least one site in 19 patients. Tachycardia could be terminated at two or more adjacent sites in 5 patients. The longest atrial coupling interval at the site of tachycardia termination was 67 +/- 27 ms (range, 30 to 130 ms) less than the AVNRT cycle length. Resetting of subsequent His bundle depolarization (H2), producing an H-H2 interval prolongation of 26 +/- 24 ms (range, 10 to 80 ms), occurred in 17 patients before termination of the tachycardia. In 18 of the 19 patients, the slow pathway was successfully ablated at the site at which AVNRT was terminated at the longest atrial coupling interval. CONCLUSIONS: Termination of tachycardia in the anterograde direction at the longest atrial coupling interval by extrastimuli delivered from the ablating catheter can be helpful for identification of an optimal site for slow-pathway ablation in patients with the common variety of AVNRT.
Adult↗
Comparison of biphasic and monophasic pulses: does the advantage of biphasic shocks depend on the waveshape?
With present implantable defibrillators, the ability to vary the defibrillation technique has been shown to increase the number of patients suitable for transvenous system. As newer waveforms become available, the need for a flexible device may change. In addition, although it has been shown that the option of biphasic waveform may increase the defibrillation efficacy, this may depend upon the shape of the biphasic waveform used. Thirty patients undergoing transvenous defibrillator implant were included in the study. In 20 patients (group I), defibrillation efficacy of simultaneous monophasic, sequential monophasic, and biphasic waveform with 50% tilt was determined randomly. Similarly, in ten patients (group II) testing of simultaneous monophasic shocks and biphasic waveforms with 65% and 80% tilt was performed in random order. The electrode system used consisted of two transvenous leads and a subcutaneous patch in all 30 patients. In group I, 50% tilt biphasic waveform consistently provided similar or better defibrillation efficacy compared to monophasic waveforms (biphasic 7.5 +/- 5.1 joules vs simultaneous 17 +/- 7.8 joules, P < 0.01; and vs sequential 17 +/- 8.4 joules, P < 0.01). In group II, 65% tilt biphasic pulse required less energy for defibrillation as compared with simultaneous monophasic shocks (9.6 +/- 4.5 joules vs 15.6 +/- 5.1 joules, P = 0.04). No significant difference was observed in terms of defibrillation threshold between 80% tilt biphasic shocks and simultaneous monophasic pulses (11.8 +/- 6 joules vs 15.6 +/- 5.1 joules, P = NS). Biphasic shocks with smaller tilt delivered using a triple lead system more uniformly improved defibrillation threshold over standard monophasic waveforms.
Defibrillators, Implantable↗
Effects of initial polarity on defibrillation threshold with biphasic pulses.
BACKGROUND: Previous studies have shown that the polarity of epicardial patches significantly affects the defibrillation efficacy of monophasic shocks. However, whether this improvement can be extended to different pulsing methods and lead systems, such as biphasic shocks using endocardial defibrillating electrodes, is unknown. METHODS: Twenty consecutive patients undergoing testing and permanent implant using an Endotak lead system with a biphasic device were included in the study. In each patient the defibrillation threshold was determined delivering biphasic pulses with the distal coil as the cathode and the proximal coil as the anode during the positive phase and with the polarity reversed. The initial electrode polarity tested was chosen randomly. The defibrillation threshold was defined as the lowest pulse amplitude that effectively terminated ventricular fibrillation induced with 60-Hz alternating current. For each biphasic pulse peak voltage, pulse duration, resistance, and stored energy were recorded. RESULTS: Of the 20 patients, 12 (60%) had lower defibrillation threshold when the proximal coil was negative, whereas only 2 patients had a lower defibrillation threshold when the distal coil was negative. In four patients a subcutaneous patch would have been required if only the biphasic pulse with the distal coil as negative had been tested. The mean stored defibrillation threshold energy was lower with the configuration using the proximal coil as cathode (16.3 +/- 8.8 J vs 21.5 +/- 11 J; P < 0.01). CONCLUSION: Change in the initial polarity of biphasic shocks may influence defibrillation efficacy and should, therefore, be assessed in each patient to achieve a more satisfactory safety margin and minimize the use of more invasive lead configurations.
Defibrillators, Implantable↗
Efficacy of different treatment strategies for neurocardiogenic syncope.
OBJECTIVES: The purpose of this study was to evaluate the efficacy of different therapeutic approaches for patients with a history of syncope and positive head-up tilt testing. BACKGROUND: Head-up tilt testing has gained broad acceptance as a reliable diagnostic method for the assessment of patients with recurrent unexplained syncope. However, once the diagnosis is established, there is no consensus on the most appropriate treatment. In this respect, efficacy of drug therapy in preventing recurrence of symptoms in such patients is not entirely clear, and controversies exist regarding the need to confirm the effects of pharmacological interventions. METHODS: Clinical follow-up was obtained in 303 patients with a history of syncope and positive head-up tilt testing. After the diagnostic head-up tilt, patients were assigned to different therapeutic approaches according to their preference or logistic impediments. Of 303 patients, 44 received empiric therapy, 210 were treated with medications proven effective during repeated head-up tilt testing, and 49 refused or discontinued medical therapy. The three groups were similar with regard to age, sex, and clinical presentation. The mean follow-up was 2.8 +/- 1.8 years. Among the patients treated according to head-up tilt guided therapy, 130 were on beta blockers, 35 on theophylline, 10 on ephedrine, 31 on disopyramide, and 4 on miscellaneous regimens. Empiric treatment consisted of beta blockers in 37 of 44 patients and other drugs in the remaining patients. RESULTS: During the follow-up, recurrence of symptoms was experienced in 12 (6%) of the 210 patients receiving the head-up tilt guided therapy, 16 (36%) of 44 in the empiric therapy group, and 33 (67%) of 49 in the no therapy group. Recurrence of symptoms in patients on empiric or no therapy was significantly more frequent as compared to the head-up tilt guided therapy group (P < 0.01). CONCLUSIONS: In patients with unexplained syncope and positive upright tilt testing, therapeutic strategies identified on the basis of response during head-up tilt have a more positive impact on the recurrence of symptoms during follow-up.
Adolescent↗
Catheter ablation in supraventricular tachyarrhythmias.
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Biophysical Phenomena↗
Catheter ablation in supraventricular tachycardia.
The evolution of catheter ablation for the treatment of supraventricular tachycardias represents a major advance in the management of cardiac arrhythmias. Excellent results in the majority of patients undergoing the procedure, together with a low rate of early complications and a brief hospitalization, make catheter ablation a highly cost-effective permanent cure. At present, however, its place in relation to alternate therapies in the management of supraventricular tachycardias has not been clearly established owing to unresolved risk-benefit issues. Continuing technical advances will likely enable catheter ablation to be successfully applied to a broader range of cardiac arrhythmias.
Anti-Arrhythmia Agents↗
Catheter ablation of ventricular tachycardia.
The role and success rate of catheter ablation for monomorphic ventricular tachycardia (VT) depend on the mechanism and origin of the tachycardia (i.e., myocardial versus His-Purkinje system) and whether it occurs in the presence or absence of structural heart diseases. For sustained bundle-branch reentry, a form of VT associated with structural heart disease, radiofrequency catheter ablation of the right bundle-branch can be performed readily and is highly successful in eliminating this arrhythmia. Because of modest success rates of catheter ablation of VT associated with a prior infarction (between 17% and 75%), this treatment modality is usually considered for cases refractory to drug therapy and should be viewed as adjunctive therapy. The target for ablation is a critical area of slow conduction, which is selected based on earliest endocardial activation, mid-diastolic potentials, concealed entrainment, or pace mapping. Radiofrequency catheter ablation may be the treatment of choice in patients with VT and no apparent structural heart disease; this is especially true for young patients who would otherwise require long-life antiarrhythmic therapy. Success rates between 75% and 100% have been reported, especially when the origin is in the right ventricular outflow tract.
Bundle-Branch Block↗