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Lorne J Gula

Publications and source records attributed to Lorne J Gula.

At least 19 recordsLinked to original sources
PubMed2007

The expectation effect and cardiac pacing for refractory vasovagal syncope.

BACKGROUND: Clinical trials of pacing for vasovagal syncope have shown conflicting results. We performed a meta-analysis to determine whether permanent pacemaker therapy prevents refractory vasovagal syncope. METHODS: Randomized trials comparing pacemaker therapy with medical therapy, usual care, placebo, or different pacing algorithms in the prevention of recurrent vasovagal syncope were considered. The primary endpoint was first recurrence of syncope. RESULTS: Nine randomized trials (2 double blind, 7 open label or single blind) were included. There was significant heterogeneity when all 9 trials were pooled (P=.0009 and I(2)=69.6%), reflecting methodological diversity in blinding and the nature of the control therapy. When pooled by trial methodology, heterogeneity was no longer apparent. Permanent pacing reduced the risk of recurrent syncope in unblinded studies (odds ratio [OR] 0.09, 95% confidence interval [CI], 0.04 to 0.22) and in studies comparing pacemaker algorithms (OR 0.04, 95% CI, 0.0 to 0.23). No effect was seen in double-blinded trials (OR 0.83, 95% CI, 0.41 to 1.70). Awareness that a permanent pacemaker was implanted and functional was associated with a significant 'expectation' effect, which itself reduced the risk of recurrent syncope (OR 0.16, 95% CI, 0.06 to 0.40, P=.0001). Results were similar when restricted to patients with a marked cardioinhibitory response on baseline tilt table testing. CONCLUSION: The results of small, preliminary trials have overestimated the treatment effect of pacemakers due to a lack of blinding of physicians and patients. Blinded trials suggest that the apparent response is due to a strong expectation response to pacing.

Cardiac Pacing, Artificial↗
PubMed2006

A novel pacing maneuver to localize focal atrial tachycardia.

BACKGROUND: Although focal atrial tachycardias cannot be entrained, we hypothesized that atrial overdrive pacing (AOP) can be an effective adjunct to localize the focus of these tachycardias at the site where the post-pacing interval (PPI) is closest to the tachycardia cycle length (TCL). METHODS: Overdrive pacing was performed in nine patients during atrial tachycardia, and in a comparison group of 15 patients during sinus rhythm. Pacing at a rate slightly faster than atrial tachycardia in group 1 and sinus rhythm in group 2 was performed from five standardized sites in the right atrium and coronary sinus. The difference between the PPI and tachycardia or sinus cycle length (SCL) was recorded at each site. The tachycardia focus was then located and ablated in group 1, and the atrial site with earliest activation was mapped in group 2. RESULTS: In both groups the PPI-TCL at the five pacing sites reflected the distance from the AT focus or sinus node. In group 1, PPI-TCL at the successful ablation site was 11 +/- 8 msec. In group 2, PPI-SCL at the site of earliest atrial activation was 131 +/- 37 msec (P < 0.001 for comparison). In groups 1 and 2, calculated values at the five pacing sites were proportional to the distance from the AT focus or sinus node, respectively. CONCLUSIONS: The PPI-TCL after-AOP of focal atrial tachycardia has a direct relationship to proximity of the pacing site to the focus, and may be clinically useful in finding a successful ablation site.

Cardiac Pacing, Artificial↗
PubMed2006

Utility and cost effectiveness of temporary pacing using active fixation leads and an externally placed reusable permanent pacemaker.

Active-fixation leads and externally placed permanent pacemakers for temporary pacing may be beneficial because they allow for greater patient mobility and comfort and increased reliability of lead placement. The relative cost of this form of pacing may be prohibitive unless markedly prolonged pacing is required. Twenty patients (63 +/- 15 years of age, 15 men) underwent external "temporary permanent" pacing. Pacing duration and associated complications were recorded. Cost models were then constructed using data from the London Health Sciences Center business unit to compare the cost of traditional temporary pacing and this technique using a Medtronic KSR903 pacemaker and 5,076 leads. Direct costs were calculated based on the 2005 Ontario Health Insurance Plan fee schedule, combined with calculation of labor and materials. Pacing was undertaken for a median of 2 days (range 2 to 83). There were no complications during implantation or pacing or after system removal. Sensing was lost in only 1 instance, which was reprogrammed uneventfully. Cost comparison showed that, although active-fixation lead placement was initially more costly ($798.71 vs $471.91), the added reliability of the permanent system allowed ward telemetry instead of cardiac care unit monitoring. This resulted in cost equivalence after only 18 hours and conferred a cost savings of $456 per 24-hour period thereafter. As a result, a savings of $585.20 is projected for a modeled patient after 48 hours of temporary pacing. In conclusion, temporary pacing using this technique is a reliable and comfortable alternative to traditional temporary pacing and appears to be a cost-effective temporary pacing option after 18 hours.

Adult↗
PubMed2006

Effect of defibrillation testing on management during implantable cardioverter-defibrillator implantation.

BACKGROUND: Verification of defibrillation efficacy by defibrillation threshold (DFT) testing during implantable cardioverter-defibrillator implantation is the current standard. Generally, defibrillation of ventricular fibrillation at 10 J below the maximum output of a device is felt to establish an adequate safety margin. Nonetheless, DFT testing adds to cost and carries some potential for morbidity, whereas its impact on outcomes in the modern era of defibrillator technology is unclear. We aimed to determine the frequency that DFT testing resulted in a change at device implant and to identify clinical and echocardiographic predictors of the need for DFT testing. METHODS: We reviewed all implantable cardioverter-defibrillators that were implanted at the London Health Sciences Centre (Ontario, Canada) from June 1999 to August 2003 and used multivariate analysis to determine variables associated with DFT test failures and elevated DFT values. When a defibrillation failure was not observed, a lowest energy to defibrillate (LED) was recorded. RESULTS: Among 168 implants, DFT testing was successful with a minimum 10-J safety margin in 152 (90%), whereas the remaining 16 required changes at device implant. In a multivariate analysis, use of amiodarone was independently associated with DFT failure (odds ratio, 4.6; 95% confidence interval, 1.2-17.0). Significantly higher mean DFT/LED values were observed among patients on amiodarone (1.36 J; P = .0041). Those with nonischemic cardiomyopathy had a higher mean DFT/LED compared with those with ischemic cardiomyopathy (1.44 J; P = .028). CONCLUSIONS: Use of amiodarone is associated with a 4-fold increase in risk of DFT failure and subsequent need for changes at implant to achieve a safe threshold. Defibrillation threshold testing appears to be most useful for patients taking amiodarone.

Amiodarone↗
PubMed2006

Differentiating arrhythmogenic right ventricular cardiomyopathy from right ventricular outflow tract ventricular tachycardia using multilead QRS duration and axis.

BACKGROUND: Ventricular tachycardia (VT) resulting from arrhythmogenic right ventricular cardiomyopathy (ARVC) may be difficult to differentiate from idiopathic right ventricular outflow tract (RVOT) VT. OBJECTIVES: The purpose of this study was to investigate the hypothesis that QRS characteristics would be different in ARVC because of altered conduction through abnormal myocardium. METHODS: In 24 RVOT VT patients (18 women and 6 men; age 42 +/- 10 years) and 20 ARVC patients (12 women and 8 men; age 38 +/- 14 years), mean QRS duration, frontal plane axis, and precordial R-wave transition were measured in 12-lead ECGs recorded during VT. RESULTS: Mean QRS duration was longer in all 12 leads in ARVC patients. A significant difference was noted in leads I, III, aVL, aVF, V(1), V(2), and V(3) (P <.05). Leads I and aVL had the largest mean difference between ARVC and RVOT VT patients of 17.6 +/- 4.7 ms and 15.8 +/- 7.5 ms, respectively (P <.0001). Lead I QRS duration > or =120 ms had a sensitivity of 100%, specificity 46%, positive predictive value 61%, and negative predictive value 100% for ARVC. The area under the receiver operating characteristic (ROC) curve was 0.89. The addition of mean QRS axis <30 degrees (R<S in lead III) to the above criterion increased specificity for ARVC to 100%. QRS duration remained sensitive and specific in the subgroup of nine ARVC ECGs with an inferior axis (ROC area 0.82). R-wave transition was not different between groups. CONCLUSION: QRS duration is longer in ARVC compared with RVOT VT. An algorithm combining lead I QRS duration for sensitivity and axis for specificity is useful for differentiating the two tachycardia substrates.

Adult↗
PubMed2006

Investigating syncope: a review.

PURPOSE OF REVIEW: This review focuses on recent literature on the cardiovascular investigation of syncope. RECENT FINDINGS: Syncope is a common and complex clinical entity with many varied etiologies, the diagnosis of which can often be elusive. Recent advances in the area of investigation in syncope include improvements in technologies for arrhythmia event monitoring and an increase in applicability and efficacy of traditional investigations. These advances have increased our ability to manage syncope. SUMMARY: A better understanding of the etiology of syncope in certain cohorts has allowed tailoring of investigations and management of syncope. This is evident when syncope occurs in the presence of structural heart disease, which is associated with a higher incidence of arrhythmias and an increased 1-year mortality. Patients with left-ventricular dysfunction should be considered candidates for an implantable cardioverter defibrillator based on heart function and syncopal presentation. In the absence of significant heart disease, investigations need to be tailored to diagnose neurally mediated causes for syncope and detection of intermittent bradycardia. The improved understanding of syncope has arisen from studies using improved investigational tools for syncope, in particular loop recorders, which are able to monitor cardiac rhythm over long periods. In those without structural heart disease and undifferentiated syncope, neurally mediated causes should be pursed initially. Tilt testing and loop recorders are employed most often in this cohort. Electrophysiological studies have largely been supplanted by implantable cardioverter defibrillator use in structural heart disease, with a low yield in patients with preserved heart function.

Cardiac Pacing, Artificial↗
PubMed2006

The garden path.

Explore the source record for details and available documents.

Atrial Flutter↗
PubMed2006

Characteristics of slow pathway conduction after successful AVNRT ablation.

BACKGROUND: AV node slow pathway conduction can persist following successful ablation for AV node reentrant tachycardia (AVNRT). We hypothesized that careful examination of AV nodal conduction curves before and after effective AVNRT ablation in patients with persistent slow pathway conduction could shed light on this apparent paradox. METHODS AND RESULTS: Thirty patients (age 40.9 +/- 14.3; 8 male) were included. AV node function curves were created based on pre- and postablation atrial extrastimulus testing. Analysis of slow pathway function curves demonstrated significant decrease in AH for any given coupling interval after ablation (mean difference -68.1 [-94.5, -41.7] P < 0.001), graphically indicated by downward displacement of the curve. In addition, mean slow pathway effective refractory period (ERP) increased from 247.9 +/- 36.1 msec to 288.6 +/- 56.0 msec (P < 0.001); mean maximum AH interval decreased from 361.3 +/- 114.2 msec to 306.9 +/- 65.2 msec (P = 0.013); mean difference in minimum and maximum AH interval during slow pathway conduction decreased (from 94.5 +/- 75.8 msec to 59.6 +/- 46.2 msec (P = 0.016). Finally, mean difference between the fast and slow pathway effective refractory periods, the span of coupling intervals over which slow pathway conduction occurred, decreased (from 113.9 +/- 61.4 msec to 63.2 +/- 41.5 msec, P = 0.001). CONCLUSIONS: Ablation, which successfully eliminates inducible and spontaneous AVNRT in the presence of persistent slow pathway conduction, is associated with significantly altered slow pathway conduction characteristics, indicating the presence of a damaged or different slow pathway after ablation, incapable of sustaining tachycardia.

Adult↗
PubMed2006

Cavotricuspid isthmus conduction is dependent on underlying anatomic bundle architecture: observations using a maximum voltage-guided ablation technique.

OBJECTIVES: We hypothesized an ablation strategy directly targeting muscle bundles might demonstrate functionally distinct "routes" of conduction, potentially shortening ablation times. BACKGROUND: Pathological study demonstrated that the cavotricuspid isthmus is composed of distinct anatomically defined bundles, many with intervening gaps of connective tissue. METHODS: A line was mapped in the "6 o'clock" region and bipolar electrogram amplitude measured during pullback. Zones of peak voltage were ablated first regardless of position. RF was delivered using either a 5-mm externally irrigated catheter, or an 8-mm nonirrigated catheter. The zone of largest remaining voltage was then sequentially targeted until conduction. RESULTS: Eighteen patients were recruited and followed for 7.9 +/- 1.9 months block occurred (mean age 64 +/- 11.6 years, male:female ratio 14:4). Bi-directional block was achieved in all patients with recurrence of atrial flutter in 1 patient. Mean total RF times was 4.7 +/- 2.8 minutes with a mean of 6.1 +/- 3.3 applications, procedure time was 127.3 +/- 37.7 minutes, and fluoroscopy time was 25.5 +/- 12.0 minutes. Two patterns of block were observed in the study group. Pattern A described no change in conduction times until block, observed in 6 (33%); pattern B described a stepwise block with discrete "jumps," observed in 12 (67%). CONCLUSIONS: An ablation strategy targeting high-voltage isthmus electrograms obviates the need for a complete anatomic line. This finding together with discrete "jumps" during ablation is consistent with the concept of conduction over discrete bundles rather than a diffuse sheet of muscle.

Adult↗
PubMed2006

Mortality following defibrillator implantation in patients with renal insufficiency.

INTRODUCTION: Patients with renal insufficiency have an increased risk of atherosclerotic coronary artery disease, cardiovascular events, and sudden cardiac death. Due to under-representation of patients with renal disease in large clinical trials, outcomes of implantable cardioverter defibrillator (ICD) implantation in this group remain unclear. METHODS AND RESULTS: Inpatient and ambulatory records were reviewed for 741 consecutive patients undergoing 947 defibrillator implants or replacements at Department of Defense Medical Facilities. Demographics, medical history, and mortality were reviewed. The mean age of the cohort was 64 +/- 14 years and 599 (80.8%) were male. There were 173 patients (23.3%) with chronic renal insufficiency, 22 (3.0%) undergoing hemodialysis, and 546 (73.7%) without reported renal disease. The mean number of annual hospital admissions for heart failure among patients with and without renal failure was 3.8 +/- 4.0 versus 1.2 +/- 1.9 (P < 0.0001), respectively. The 1-year survival for those without renal insufficiency was 96.6%, compared to 87.8% for those with chronic renal insufficiency, and 88.7% for those undergoing hemodialysis. Multivariate analysis demonstrated a significant association between mortality among ICD patients and renal insufficiency, independent of coexisting congestive heart failure, ischemic cardiomyopathy, and diabetes mellitus (P < 0.0001). CONCLUSIONS: Among ICD recipients, those with renal insufficiency have a significantly higher mortality rate than those without renal insufficiency. Among a cohort of patients with ICDs, those with known renal insufficiency have higher rates of health care resource utilization and more heart failure admissions. Development of a national registry for ICDs should include data with regard to renal function.

Aged↗
PubMed2005

Physiologic pacing in patients with obstructive sleep apnea: a prospective, randomized crossover trial.

OBJECTIVES: This study was designed to assess the impact of prevention of bradycardia with physiologic pacing on the severity of obstructive sleep apnea. BACKGROUND: Apneic episodes during sleep are associated with slowing of the heart rate during apnea and tachycardia with subsequent arousal. Patients with permanent pacemakers may have reduced episodes of sleep apnea when their pacemaker rate is set faster than their spontaneous nocturnal heart rate. METHODS: We conducted a prospective, randomized, single-blind crossover trial of temporary atrial pacing in obstructive sleep apnea to reduce the apnea hypopnea index (AHI). Fifteen patients (age 60 +/- 13 years, 12 men) with moderate to severe obstructive sleep apnea (AHI 34 +/- 14) underwent insertion of an externalized atrial permanent pacing system via the left subclavian vein. Patients underwent overnight respiratory sleep studies in hospital, during atrial pacing at 75 beats/min, and with pacing turned off. The order of pacing mode was randomized, with crossover the subsequent night to the other mode. Patients were blinded to pacing mode, and the analysis of sleep recordings was blind to pacing mode. RESULTS: Pacing was tolerated without complications in all patients. Overnight physiologic pacing did not affect the AHI (pacing 39 +/- 21/h vs. control 42 +/- 21/h, p = 0.23, 95% confidence interval -9.3 to 2.5 for difference), desaturation time (pacing 3.8 +/- 6.0% vs. control 3.5 +/- 4.3%, p = 0.70), or the minimum SaO(2) (pacing 75 +/- 10% vs. control 77 +/- 11%, p = 0.38). There was a borderline significant reduction in circulatory time with pacing (pacing 23.4 +/- 3.2 s vs. control 25.5 +/- 4.4 s, p = 0.09). CONCLUSIONS: Temporary atrial pacing does not appear to improve respiratory manifestations of obstructive sleep apnea. Permanent atrial pacing in this patient population does not appear to be justified.

Aged↗
PubMed2005

Diagnosis of unexplained cardiac arrest: role of adrenaline and procainamide infusion.

BACKGROUND: Cardiac arrest with preserved left ventricular function may be caused by uncommon genetic conditions. Although these may be evident on the ECG, long-term monitoring or provocative testing is often necessary to unmask latent primary electrical disease. METHODS AND RESULTS: Patients with unexplained cardiac arrest and no evident cardiac disease (normal left ventricular function, coronary arteries, and resting corrected QT) underwent pharmacological challenge with adrenaline and procainamide infusions to unmask subclinical primary electrical disease. Family members underwent noninvasive screening and directed provocative testing on the basis of findings in the proband. Eighteen patients (mean+/-SD age, 41+/-17 years; 11 female) with unexplained cardiac arrest were assessed. The final diagnosis was catecholaminergic ventricular tachycardia (CPVT) in 10 patients (56%), Brugada syndrome in 2 patients (11%), and unexplained (idiopathic ventricular fibrillation) in 6 patients (33%). Of 55 family members (mean+/-SD age, 27+/-17 years; 33 female), 9 additional affected family members were detected from 2 families, with a single Brugada syndrome patient and 8 CPVT patients. CONCLUSIONS: Provocative testing with adrenaline and procainamide infusions is useful in unmasking the etiology of apparent unexplained cardiac arrest. This approach helps to diagnose primary electrical disease, such as CPVT and Brugada syndrome, and provides the opportunity for therapeutic intervention in identified, asymptomatic family members who harbor the same disease.

Anti-Arrhythmia Agents↗
PubMed2005

Feasibility of his bundle pacing as an alternative pacing site: measurement of his refractoriness.

BACKGROUND: Direct pacing of the His bundle has been proposed for permanent pacing to maintain physiological synchrony of ventricular activation. Measurement of His bundle refractoriness may be useful in predicting suitability of this technique in an individual. We sought to determine whether this could be measured consistently in patients, defining a normal range. METHODS: His bundle pacing was performed in 20 consecutive patients (mean age 44.6 +/- 19.5, 5 male) undergoing electrophysiology study. Incremental and extrastimulus testing were performed from the His region to determine effective and functional refractory periods of the His bundle. RESULTS: Consistent His capture was possible in 18 of 20 (90%) patients studied. Extrastimulus testing from the His region at a drive cycle length of 600 msec was successful in all of these patients. With loss of His capture, QRS duration prolonged 32%, and stimulus to atrial electrogram interval prolonged 49.6 +/-16.3 msec. The effective refractory periods at drive cycle lengths 600, 500, and 400 msec were 407 +/- 70 msec, 320 +/- 39 msec, and 336 +/- 54 msec, respectively. Corresponding functional refractory periods were 414 +/- 62, 371 +/- 52, and 329 +/- 32. Consistent capture with incremental His pacing was possible in 50% of patients, and 1:1 His capture was lost at mean cycle length 408 +/-93 msec. CONCLUSIONS: His refractory periods can be determined consistently in unselected individuals undergoing electrophysiological studies. Measurement of HERP and HFRP may prove useful in assessing the suitability of the His bundle for permanent pacing.

Adult↗
PubMed2005

Is ambulatory monitoring for "community-acquired" syncope economically attractive? A cost-effectiveness analysis of a randomized trial of external loop recorders versus Holter monitoring.

BACKGROUND: Out patient ambulatory monitoring is often performed in patients with syncope that present in the primary care setting to include or exclude an arrhythmia. The cost-effectiveness of 2 monitoring strategies was assessed in a prospective randomized trial. METHODS: One hundred patients referred for ambulatory monitoring with syncope or presyncope were randomized to a 1-month external loop recorder (n = 49) or 48-hour Holter monitor (n = 51). Patients were offered crossover if there was failed activation or no symptom recurrence. The primary end point was symptom-rhythm correlation during monitoring. Direct costs were calculated based on the 2003 Ontario Health Insurance Plan fee schedule, combined with calculation of labor, materials, service, and overhead for diagnostic testing and related equipment. RESULTS: Before enrollment, the cost of all previous health care resource use was USD 472 +/- USD 397 (range USD 21-USD 1965). In the loop recorder group, 63% of patients had symptom recurrence and successful activation, compared with 24% in the Holter group (P < .0001). The cost per Holter was USD 177.64, and per loop recorder, USD 533.56, with a similar cost per diagnosis with the 2 techniques. The incremental cost-effectiveness ratio of the loop recorder was USD 901.74 per extra successful diagnosis. A strategy of Holter followed by offered loop recorder trended toward lower cost than initial loop recorder followed by Holter (USD 481 +/- USD 267 vs USD 551 +/- USD 83, P = .08), but was associated with a lower overall diagnostic yield (49% vs 63%) and a resultant higher cost per diagnosis (USD 982 vs USD 871, P = .08). Bootstrapping suggested that 90% of incremental cost-effectiveness ratios were less than USD 1250. CONCLUSION: Despite the increased upfront cost of external loop recorders, the marked improvement in diagnostic yield offsets the cost. External loop recorders are an economically attractive alternative. First-line use of external loop recorders in patients with "community-acquired" syncope and presyncope should be considered to optimize diagnostic yield given its value.

Cost-Benefit Analysis↗
PubMed2005

Atrial response to ventricular antitachycardia pacing discriminates mechanism of 1:1 atrioventricular tachycardia.

BACKGROUND: Inappropriate shocks from implantable cardioverter defibrillators (ICD) remain a significant clinical problem despite device discrimination algorithms. The atrial response to antitachycardia pacing (ATP) may determine the mechanism of 1:1 A:V tachycardia. METHODS: For this study we refer to sinus tachycardia, atrial tachycardia (AT), atrial fibrillation, and flutter as atrial tachycardia (AT), and all other tachycardia as "non-AT." Three atrial response patterns during the burst of ATP were determined. The atrial cycle length (ACL) may be unchanged (type 1) indicating AT. The ACL may show variation during ATP (type 2) indicating variable VA block and does not discriminate between an AT and a non-AT mechanism, in which case a default diagnosis of non-AT is made. The ACL may accelerate to the ATP cycle length (type 3) indicating entrainment. A VAAV response at the end of ATP was considered diagnostic of AT (type 3A) whereas a VAV or VVA response was considered a non-AT mechanism (type 3B). This algorithm was applied to ICD tracings from 68 episodes of spontaneous 1:1 A:V tachycardia that had 136 sequences of ATP administered. The rhythm "truth" was determined by consensus of two experienced clinicians. RESULTS: The algorithm correctly identified AT with a sensitivity of 71.9% (95% CI: 67.1-73.6), and specificity of 95% (83.5-99.1). The PPV was 97.2% (90.9-99.5), and NPV 58.5% (51.4-61.0). Kappa was 0.57 (0.43-0.62). If used clinically the algorithm would have aborted 53.3% (8/15) of inappropriate shocks delivered into an AT-mechanism tachycardia and would not have withheld a shock for any episode of VT. CONCLUSION: Analysis of atrial response patterns during and after ventricular ATP can successfully discriminate tachycardia mechanism and may reduce inappropriate ICD shocks.

Algorithms↗