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Biomedical subjects

Hakan Oral

Publications and source records attributed to Hakan Oral.

At least 55 records · Page 3Linked to original sources
PubMed2004

Catheter ablation guided by termination of postinfarction ventricular tachycardia by pacing with nonglobal capture.

OBJECTIVES: We prospectively investigated the prevalence and value of this criterion for identifying a target site for ablation in patients with postinfarction ventricular tachycardia (VT). BACKGROUND: Termination of postinfarction VT by pacing with nonglobal capture identifies a critical component of the reentrant circuit. METHODS: In a consecutive series of 34 patients with prior infarction (age 67 +/- 10 years, ejection fraction 0.26 +/- 0.1) referred for radiofrequency catheter ablation, mapping was performed in the left ventricle. At sites with abnormal electrograms, pacing was performed during VT. If VT terminated with nonglobal capture during the pacing train, radiofrequency energy was delivered. RESULTS: Sixty-two VTs (cycle length 450 +/- 84 ms) were mapped and targeted for radiofrequency ablation. Concealed entrainment was present at 101 endocardial sites. Among the 101 sites, VT terminated by pacing with nonglobal capture at 5 sites (5%). At 10 additional sites in 10 patients, VT terminated by pacing with nonglobal capture, and concealed entrainment could not be documented at these sites because of reproducible termination of the VT. An application of radiofrequency energy resulted in VT termination at all 15 sites where nonglobal capture was documented and the targeted VTs were no longer inducible after ablation. CONCLUSIONS: Termination of VT by pacing with nonglobal capture can be demonstrated in approximately one third of patients with postinfarction VT and is a specific criterion for identifying a critical component of the reentrant circuit, whether or not concealed entrainment can be documented at that site.

Aged↗
PubMed2004

Effects of left atrial ablation of atrial fibrillation on size of the left atrium and pulmonary veins.

OBJECTIVES: The purpose of this study was to determine the effect of left atrial circumferential ablation on the size of the left atrium and pulmonary veins (PVs). BACKGROUND: The long-term effects of left atrial circumferential ablation on left atrial and PV size and anatomy have not been analyzed in quantitative fashion. METHODS: PV and left atrial sizes were analyzed in 41 consecutive patients (mean age 54 +/- 12 years) with paroxysmal (n = 25) or chronic (n = 16) atrial fibrillation. Computed tomography of the chest with three-dimensional reconstruction was performed before and 4 +/- 2 months after left atrial circumferential ablation. Left atrial circumferential ablation was performed to encircle the PVs 1 to 2 cm from the ostia, using a power output of 70 W. Additional ablation lines were created in the posterior left atrium and mitral isthmus. Radiofrequency energy also was delivered within the circles and at the PV ostia in 51% of patients at a reduced power output of 35 W. RESULTS: At 6 months, 36 patients (88%) were in sinus rhythm without antiarrhythmic drug therapy, including 3 patients (7%) who developed persistent left atrial flutter and underwent subsequent successful ablation of atrial flutter. There was a 15 +/- 16% decrease in left atrial volume (P < .01) and 10 +/- 35% decrease in PV ostial area (P < .01), without focal narrowing, in patients with a successful outcome. Focal PV stenosis did not occur in any of the 41 patients. CONCLUSIONS: Maintenance of sinus rhythm after left atrial circumferential ablation is associated with reduced left atrial and PV ostial size. Left atrial circumferential ablation for atrial fibrillation does not cause PV stenosis.

Atrial Fibrillation↗
PubMed2004

Relative timing of isolated potentials during postinfarction ventricular tachycardia and sinus rhythm.

BACKGROUND: In postinfarction patients, isolated potentials separated by an isoelectric segment from the ventricular electrogram indicate areas of block. Isolated potentials can be recorded during both sinus rhythm and ventricular tachycardia (VT). In an attempt to differentiate bystander pathways from critical sites within a reentry circuit, we compared the relative timing of isolated potentials during VT and sinus rhythm. METHODS: In 19 patients (mean age 68 +/- 6 years) with postinfarction VT who were referred for VT ablation, mapping was performed in the presence and absence of VT. Forty-three sites at which there was concealed entrainment during 35 VT's (mean cycle length 469 +/- 74 ms) displayed an isolated potential separated from the main portion of the ventricular electrogram by an isoelectric segment of >/=30 msec in the presence and absence of VT. The interval between the ventricular electrogram and the isolated potential was measured during VT and baseline rhythm, and the absolute difference (DeltaIPI) was calculated. The DeltaIPI was significantly greater at effective ablation sites (119 +/- 69 ms) than at ineffective ablation sites (30 +/- 28 ms, p < 0.001). The positive predictive value of a DeltaIPI > 85 ms for an effective ablation site was 100%. CONCLUSION: At sites of concealed entrainment, an absolute difference >85 ms between the isolated potential intervals during sinus rhythm and VT is highly specific for a critical area of the VT reentry circuit in post-infarction patients.

Action Potentials↗
PubMed2004

Acute effects of left atrial radiofrequency ablation on atrial fibrillation.

INTRODUCTION: Acutely, when left atrial ablation is performed during atrial fibrillation (AF), the AF may persist and require cardioversion, or it may convert to sinus rhythm or to atrial tachycardia/flutter. The prevalence of these acute outcomes has not been described. METHODS AND RESULTS: Left atrial ablation, usually including encirclement of the pulmonary veins, was performed during AF in 144 patients with drug-refractory AF. Conversion to sinus rhythm occurred in 19 patients (13%), to left atrial tachycardia in 6 (4%), and to atrial flutter in 6 (4%). In the 6 patients with a focal atrial tachycardia, the mean cycle length was 294 +/- 45 ms. The tachycardia arose in the left atrial roof in 3 patients, the left atrial appendage in 2, and the anterior left atrium in 1. In 3 of 6 patients, the focal atrial tachycardia originated in an area that displayed a relatively short cycle length during AF. In 6 patients, AF converted to macroreentrant atrial flutter with a mean cycle length of 253 +/- 47 ms, involving the mitral isthmus in 5 patients and the septum in 1 patient. All atrial tachycardias and flutters were successfully ablated with 1 to 15 applications of radiofrequency energy. CONCLUSION: When left atrial ablation is performed during AF, the AF may convert to atrial tachycardia or flutter in approximately 10% of patients. Focal atrial tachycardias that occur during ablation of AF may be attributable to driving mechanisms that persist after AF has been eliminated, whereas atrial flutter results from incomplete ablation lines.

Acute Disease↗
PubMed2004

Pulmonary vein isolation for vagotonic, adrenergic, and random episodes of paroxysmal atrial fibrillation.

INTRODUCTION: Based on the clinical history, paroxysmal atrial fibrillation (PAF) may be classified as vagotonic, adrenergic, or random. It is unclear whether pulmonary vein (PV) isolation is equally effective for these types of PAF. METHODS AND RESULTS: Segmental ostial ablation to isolate the PVs was performed in 188 consecutive patients (mean age 53 +/- 12 years) with PAF. Based on the clinical history, PAF was classified as random in 136 patients (72%), adrenergic in 30 (16%), and vagotonic in 22 (12%). Three or four PVs were targeted for isolation in all patients, and successful isolation was achieved in 96% of targeted PVs. At 1-year follow-up, 69% of patients with random AF, 83% of patients with adrenergic AF, and 50% of patients with vagotonic AF were free from recurrent episodes of AF in the absence of any antiarrhythmic drug therapy. Vagotonic AF was an independent clinical predictor of recurrent AF (P = 0.03). CONCLUSION: PV isolation has a lower efficacy in patients with vagotonic PAF than in patients with adrenergic or random episodes of PAF, suggesting that the PVs less often play an important role in vagotonic PAF.

Atrial Fibrillation↗
PubMed2004

Detection of inadvertent catheter movement into a pulmonary vein during radiofrequency catheter ablation by real-time impedance monitoring.

INTRODUCTION: During radiofrequency ablation to encircle or isolate the pulmonary veins (PVs), applications of radiofrequency energy within a PV may result in stenosis. The aim of this study was to determine whether monitoring of real-time impedance facilitates detection of inadvertent catheter movement into a PV. METHODS AND RESULTS: In 30 consecutive patients (mean age 53 +/- 11 years) who underwent a left atrial ablation procedure, the three-dimensional geometry of the left atrium, the PVs, and their ostia were reconstructed using an electroanatomic mapping system. The PV ostia were identified based on venography, changes in electrogram morphology, and manual and fluoroscopic feedback as the catheter was withdrawn from the PV into the left atrium. Real-time impedance was measured at the ostium, inside the PV at approximately 1 and 3 cm from the ostium, in the left atrial appendage, and at the posterior left atrial wall. There was an impedance gradient from the distal PV (127 +/- 30 Omega) to the proximal PV (108 +/- 15 Omega) to the ostium (98 +/- 11 Omega) in each PV (P < 0.01). There was no significant impedance difference between the ostial and left atrial sites. During applications of radiofrequency energy, movement of the ablation catheter into a PV was accurately detected in 80% of the cases (20) when there was an abrupt increase of >/=4 Omega in real-time impedance. CONCLUSION: There is a significant impedance gradient from the distal PV to the left atrium. Continuous monitoring of the real-time impedance facilitates detection of inadvertent catheter movement into a PV during applications of radiofrequency energy.

Adult↗
PubMed2004

Prevalence of asymptomatic recurrences of atrial fibrillation after successful radiofrequency catheter ablation.

INTRODUCTION: The long-term efficacy of radiofrequency catheter ablation of atrial fibrillation (AF) has been based on patient-reported symptoms suggestive of AF. However, asymptomatic recurrences of AF may remain undetected. The aim of this study was to determine the prevalence of asymptomatic recurrences of AF after an apparently successful catheter ablation procedure for AF. METHODS AND RESULTS: Among 244 consecutive patients (mean age 53 +/- 11 years) who underwent a pulmonary vein isolation procedure for symptomatic paroxysmal AF and who reported no symptoms of recurrent AF at > or =6 months after the procedure, 60 patients with a history of > or =1 episode of AF per week were asked to participate in this study. Preablation, these patients had experienced 19 +/- 13 episodes of AF per month. The patients were provided with a patient-activated transtelephonic event recorder for 30 days, a mean of 642 +/- 195 days after the ablation procedure, and were asked to record and transmit recordings on a daily basis and whenever they felt palpitations. Seven patients (12%) felt palpitations during the study, although they had not experienced symptoms previously. Each of these 7 patients had an episode of AF documented with the event monitor during symptoms. In these 7 patients, the mean number of episodes per month decreased from 19 +/- 14 preablation to 3 +/- 1 postablation (P < 0.001). Among the 53 asymptomatic patients, an episode of AF was captured in 1 (2%) patient during the study period. CONCLUSION: Asymptomatic recurrences of AF after an apparently successful catheter ablation procedure for symptomatic paroxysmal AF are infrequent.

Atrial Fibrillation↗
PubMed2004

Mechanism of immediate recurrences of atrial fibrillation after restoration of sinus rhythm.

An immediate recurrence of AF may occur after restoration of sinus rhythm. Although pulmonary vein (PV) isolation has been shown to prevent immediate recurrence of AF, the specific trigger for immediate recurrence of AF has not been described. In 89 consecutive patients (mean age 53 +/- 11 years) who had sinus rhythm restored by spontaneous or transthoracic cardioversion in the course of a PV isolation procedure, electrograms recorded within a PV and in the adjacent left atrium were analyzed to determine the mechanism of initiation of immediate recurrence of AF. Immediate recurrence of AF was defined as a recurrence of AF within 90 seconds after restoration of sinus rhythm. There were 124 episodes of immediate recurrence of AF at a mean of 18 +/- 23 seconds after cardioversion. Recordings within the PV that triggered the immediate recurrence of AF were available in 23 (19%) of the 124 immediate recurrence of AF episodes. Among these 23 episodes of immediate recurrence of AF, all (100%) were triggered by a burst of PV tachycardia (P < 0.001). The coupling interval and prematurity index (coupling interval/preceding sinus cycle length) of the premature depolarizations that did and did not trigger immediate recurrence of AF were 246 +/- 67 ms and 0.30 +/- 0.11 vs 378 +/- 117 ms and 0.49 +/- 0.16, respectively (P < 0.01). Immediate recurrence of AF was abolished by PV isolation. The mechanism of immediate recurrence of AF is a burst of PV tachycardia, not a single premature depolarization. Immediate recurrence of AF identifies patients with AF in whom the PVs may play a major role in the initiation of AF.

Atrial Fibrillation↗
PubMed2004

Incremental value of isolating the right inferior pulmonary vein during pulmonary vein isolation procedures in patients with paroxysmal atrial fibrillation.

Electrical isolation of the left superior, left inferior, and right superior pulmonary veins (PVs) is often, but not always, effective in eliminating paroxysmal atrial fibrillation (PAF). The incremental clinical value of also isolating the right inferior PV has not been well defined. PV isolation by ostial applications of radiofrequency energy guided by PV potentials was performed in 176 consecutive patients (mean age 52 +/- 11 years) with PAF. The left superior, left inferior, and right superior PVs were targeted in 106 patients, and all four PVs were targeted 70 patients. Successful isolation was achieved in 96% of targeted PVs. The mean duration of follow-up was 15 +/- 7 months. At 1-year follow-up, 58% of patients in whom three PVs were isolated were free of recurrent PAF in the absence of antiarrhythmic drug therapy, compared to 73% of patients in whom all four PVs were isolated (P = 0.07). There is a trend towards a better outcome when all four PVs are isolated than when only the three major PVs are isolated. Whenever feasible, the right inferior PV should be isolated along with the other three PVs during the first ablation procedure in patients with PAF.

Adult↗
PubMed2003

Catheter ablation for paroxysmal atrial fibrillation: segmental pulmonary vein ostial ablation versus left atrial ablation.

BACKGROUND: Segmental ostial catheter ablation (SOCA) to isolate the pulmonary veins (PVs) and left atrial catheter ablation (LACA) to encircle the PVs both may eliminate paroxysmal atrial fibrillation (PAF). The relative efficacy of these 2 techniques has not been directly compared. METHODS AND RESULTS: Of 80 consecutive patients with symptomatic PAF (age, 52+/-10 years), 40 patients underwent PV isolation by SOCA and 40 patients underwent LACA to encircle the PVs. During SOCA, ostial PV potentials recorded with a ring catheter were targeted. LACA was performed by encircling the left- and right-sided PVs 1 to 2 cm from the ostia and was guided by an electroanatomic mapping system; ablation lines also were created in the mitral isthmus and posterior left atrium. The mean procedure and fluoroscopy times were 156+/-45 and 50+/-17 minutes for SOCA and 149+/-33 and 39+/-12 minutes for LACA, respectively. At 6 months, 67% of patients who underwent SOCA and 88% of patients who underwent LACA were free of symptomatic PAF when not taking antiarrhythmic drug therapy (P=0.02). Among the variables of age, sex, duration and frequency of PAF, ejection fraction, left atrial size, structural heart disease, and the ablation technique, only an increased left atrial size and the SOCA technique were independent predictors of recurrent PAF. The only complication was left atrial flutter in a patient who underwent LACA. CONCLUSIONS: In patients undergoing catheter ablation for PAF, LACA to encircle the PVs is more effective than SOCA.

Atrial Fibrillation↗
PubMed2003

Effects of operator experience on the outcome and duration of pulmonary vein isolation procedures for atrial fibrillation.

Segmental, ostial ablation to isolate the pulmonary veins has been shown to be effective for the treatment of atrial fibrillation (AF). The purpose of this study was to determine the effects of operator experience on the outcome and duration of pulmonary vein isolation procedures for AF. One hundred three consecutive patients with AF underwent segmental, ostial ablation to isolate pulmonary veins. The effect of operator experience on the outcome and duration of the procedure was measured. The mean procedure duration was 232 +/- 70 minutes (range 50 to 460). There was an indirect linear relation between the total procedure time and the number of procedures performed (r = -0.68; p <0.001), and between the total fluoroscopic time and the number of procedures performed (r = -0.71; p <0.001). The percentage of patients in whom complete isolation of the pulmonary veins was achieved and the total duration of radiofrequency energy delivered during the procedures remained stable as operator experience increased. Operator experience was not an independent predictor of recurrent AF. The primary effect of operator experience on pulmonary vein isolation procedures for AF was a marked reduction in the duration of the procedure and fluoroscopic time. Long procedure durations and large amounts of radiation exposure may currently limit the widespread application of this therapy. The results of this study suggest that after >75 cases, segmental ablation to isolate the pulmonary veins using fluoroscopy and conventional radiofrequency ablation usually is feasible in <3 hours.

Adult↗
PubMed2003

Myocardial proinflammatory cytokine expression and left ventricular remodeling in patients with chronic mitral regurgitation.

BACKGROUND: In an animal model, stretch was shown to induce myocardial tumor necrosis factor-alpha (TNF-alpha) expression. The purposes of this study were to determine whether the left ventricular (LV) volume overload that occurs in patients with chronic mitral regurgitation (MR) can induce myocardial and systemic TNF-alpha expression and whether there is a relationship between TNF-alpha expression and LV remodeling. METHODS AND RESULTS: Plasma TNF-alpha and its receptors were measured before mitral valve (MV) repair surgery in 26 MR patients and 23+/-12 months after MV repair surgery in 9 MR patients. Myocardial mRNA copies of TNF-alpha were determined in 11 MR and 10 donor hearts using quantitative RT-PCR. Compared with 15 control subjects, pre-MV repair plasma TNF-alpha (3.59+/-1.81 versus 2.03+/-1.02 pg/mL, P<0.005) and its receptor levels were elevated in MR patients. Myocardial TNF-alpha mRNA copies (corrected for beta-actin mRNA expression) in MR patients and donor hearts were 38.96+/-42.74x10(6) and 0.88+/-0.75x10(6), respectively (P=0.01). After MV surgery, there was a decrease in the plasma levels of TNF-alpha (2.79+/-1.14 versus 3.51+/-1.34 pg/mL, P=0.02) and its receptors. There was a correlation between myocardial TNF-alpha expression and preoperative LV end-diastolic and end-systolic volumes. Moreover, there was an inverse correlation between myocardial TNF-alpha expression and regression in LV end-diastolic (r=-0.76, P=0.007) and end-systolic (r=-0.73, P=0.01) volumes after MV surgery. CONCLUSIONS: TNF-alpha is expressed in the myocardium and plasma of MR patients. Correction of the LV volume overload with MV surgery results in reversal of TNF-alpha expression. There is a relationship between TNF-alpha expression and parameters of LV remodeling, suggesting that TNF-alpha may play a role in the pathogenesis of the LV remodeling that occurs in MR.

Adult↗
PubMed2003

Rate-dependent effect of verapamil on atrial refractoriness.

OBJECTIVES: The purpose of this study was to determine whether verapamil has rate-dependent effects on the atrial effective refractory period (AERP). BACKGROUND: Block of calcium current (I(Ca)) and rapid component of the delayed rectifier potassium current (I(Kr)) by verapamil is frequency-dependent. This may result in variable effects of verapamil on the AERP, depending on the rate. METHODS: The subjects of this study were 30 adults with a mean age of 45 +/- 13 years who did not have structural heart disease. In 20 subjects, the AERP was measured at basic drive cycle lengths (BDCLs) of 650 to 250 ms, in 50 ms decrements, before and after infusion of 0.1 mg/kg verapamil. The effective refractory periods (ERPs) were measured in the setting of autonomic blockade in 10 subjects and without autonomic blockade in 10 subjects. Ten subjects served as a control group and received a saline infusion instead of verapamil. RESULTS: Verapamil significantly prolonged the AERP at BDCLs of 650 to 500 ms (p < 0.01 or p < 0.05) and significantly shortened the ERP at BDCLs of 300 and 250 ms (p < 0.01). In the control group, there were no significant differences between the baseline and post-saline measurements of ERP. CONCLUSIONS: Verapamil prolongs AERP at slow rates and shortens AERP at rapid rates. These findings are consistent with a predominant effect on I(Ca) at rapid rates and a predominant effect on I(Kr) at slow rates.

Adult↗
PubMed2003

Compared with control subjects, the systemic sympathetic nervous system is activated in patients with mitral regurgitation.

BACKGROUND: Whether the systemic sympathetic nervous system is activated as a compensatory mechanism in response to mitral regurgitation (MR) in humans is unknown. We tested the hypotheses that the systemic sympathetic nervous system would be activated in patients with MR in comparison with control subjects and that this activation would occur early in the disease process as a compensatory mechanism for chronic left ventricular (LV) volume overload. METHODS: We studied 37 patients with MR who underwent right heart catheterization and biplane cineventriculography to obtain LV end-diastolic and end-systolic volumes, ejection fractions, and regurgitant volumes. In these 37 patients with MR and in 23 control subjects, an [(3)H]-norepinephrine ([(3)H]-NE) infusion and multiple arterial blood samples provided data for a 2-compartment modeling analysis to calculate extravascular NE release rates (NE(2)). RESULTS: The mean NE(2) (2.05 +/- 0.76 microg/min/m(2)) in the patients with MR was greater than that in the control subjects (1.48 +/- 0.75 microg/min/m(2), P =.007). Furthermore, the mean NE(2) values were also greater in the patients with MR who were in clinical class I (P =.05), with a pulmonary capillary wedge pressure <12 mm Hg (P =.05) or a LV ejection fraction >or=0.60 (P =.06) compared with the control subjects. The mean NE(2) values were increased further in patients with MR who had a LV ejection fraction <0.60 (P =.02). CONCLUSIONS: The systemic sympathetic nervous system is activated in patients with MR in comparison with control subjects, and this activation appears to occur early in the disease process as a compensatory mechanism for LV volume overload.

Adult↗
PubMed2003

Diagnostic value of single versus dual chamber electrograms recorded from an implantable defibrillator.

INTRODUCTION: The clinical utility of ventricular electrograms in comparison to atrial and ventricular electrograms in diagnosing the type of tachycardias recorded by an implantable defibrillator has not been addressed from the standpoint of a clinician's diagnostic accuracy and confidence in that diagnosis. METHODS: Fifty-two tachycardia episodes recorded from dual chamber defibrillators were divided into two tests. The initial test contained only information from the ventricular electrogram and the second test contained information from both the atrial and ventricular electrograms. For each test, the reviewers were asked to provide the specific diagnosis, the originating chamber of origin of the tachycardia, and the confidence of their responses for each question. McNemar's test for matched pairs was used to determine accuracy and an analysis of variance to determine reviewer confidence. RESULTS: The overall accuracy for both the specific diagnosis (61% vs. 79%; p < 0.001) and the chamber of origin (76% vs. 90%; p < 0.001) improved when both the atrial and ventricular electrograms were available for review. Reviewer confidence appeared to correlate with diagnostic accuracy. CONCLUSIONS: The data clearly show the favorable impact of dual chamber defibrillators on the diagnostic accuracy and confidence of clinicians faced with a clinical tachycardia recorded from an implantable defibrillator. Such improvements may translate into more focused and appropriate therapeutic interventions.

Aged↗
PubMed2003

Conducting randomized trials in the electrophysiology laboratory: lessons from a randomized comparison of recording methods during pulmonary vein isolation by segmental ostial ablation.

Accurate identification of pulmonary vein (PV) potentials during segmental ostial ablation for PV isolation is very important to completely isolate the PVs and also to avoid unnecessary applications of radiofrequency energy. A prior post hoc analysis of unipolar and bipolar electrograms recorded from successful and unsuccessful ablation sites demonstrated that unipolar electrograms recorded at successful sites were more likely to have a rapid intrinsic deflection, larger amplitude, and earlier activation than electrograms recorded at unsuccessful sites. Moreover, unipolar electrograms recorded from the ablation and circular ostial mapping catheters were almost identical at successful sites. Based on these observations, a prospective, randomized study was conducted to test whether unipolar and bipolar electrograms would facilitate the ablation procedure when compared to bipolar electrograms alone during PV isolation in patients with atrial fibrillation (AF). In 44 consecutive patients with paroxysmal AF, 114 PVs were randomized to segmental ostial ablation guided by unipolar and bipolar electrograms (61) or by bipolar electrograms only (53). Segmental ostial ablation guided by unipolar and bipolar electrograms was associated with a approximately 20-30% decrease in the procedure and fluoroscopy times necessary for isolation of a PV and also in the duration of radiofrequency energy application required for complete isolation of a PV. Although the sample size was not sufficient to detect a 5% change, the success rate for complete electrical isolation and the risk of symptomatic PV stenosis were similar between the 2 groups. Online analysis of unipolar electrograms facilitated the PV isolation procedure and was incremental to the analysis of bipolar electrograms alone. However, because segmental ostial ablation has only modest efficacy in achieving long-term freedom from recurrent AF, alternative ablation strategies that may or may not target PVs will eventually evolve. The role of unipolar electrograms in these new methods remains to be determined.

Action Potentials↗