Baseline HV Research Articles

Effects of two dentifrices on the surface properties and staining susceptibility of polymer-based materials.

This study examined the effect of whitening and abrasive regular dentifrices on the surface characteristics and stain susceptibility of polymer-based CAD-CAM blocks subjected to artificial toothbrushing abrasion (TB). Two resin composite blocks [CeraSmart (CS) and Grandio Blocs (GB)], one polymer-infiltrated ceramic [Vita Enamic (VE)], and one direct resin composite [GrandioSO (RC)] were used to produce 60 specimens. The baseline mass, gloss, roughness, Vickers hardness (Hv), and color were measured after 7 days of water storage. The specimens were then separated into three TB treatment groups (n = 5): water control (C), regular daily dentifrice (R), and whitening dentifrice (W). Measurements were repeated post-TB (20,000 cycles). All specimens were immersed in coffee, and the CIE ΔE00 was measured after 1, 7, and 14 days. Two-way, one-way ANOVA, and Tukey's post hoc tests were performed to determine any significant differences between the materials and TB groups. To determine the stain resistance, repeated measures of ANOVA, one-way ANOVA, and Tukey's post hoc tests were used (α = 0.05). The R and W mass changes were minimal (-3.77 to 3.16g%). W reduced the gloss of all the materials by 12.6%-65%. All materials in W were slightly rougher (Ra, 0.107-0.144 μm) than those in R (Ra, 0.049-0.072 μm). The ΔE00 ranged from 0.6 to 1.6 in W and 0.4 to 1.4 in R. VE was the hardest material at baseline (Hv = 362), whereas brushing and staining lowered Hv in all TB groups (282.8-300.6). After brushing in W, VE, and RC were more susceptible to coffee stains than were CS and GB. The whitening dentifrice roughened CAD-CAM specimens, reducing gloss, yet lightened some materials. Polymer-infiltrated ceramic and direct resin composite specimens brushed with abrasive regular or whitening dentifrice resulted in more intense staining than the CAD-CAM resin composites.

Impact of Pulsed Electric Field Ablation on His Bundle Conduction: A Preclinical Canine Study.

BACKGROUND Pulsed field ablation (PFA), as a non-thermal ablation modality, has received increasing attention. The aim of this study was to evaluate the effect of PFA upon His bundle via its implementation with different voltages on the maximum His bundle potential in canines, providing scientific basis for clinical application. MATERIAL AND METHODS Pulsed electrical field energy was delivered from a ablation catheter to the maximum His potential of 7 dogs, followed by a series of electrogram and histology assessments. RESULTS The baseline AH and HV intervals were 55.3±3.7 ms (range, 53.0-59.0 ms), and 34.9±1.3 ms (range, 34.0-36.0 ms), respectively, which were elevated to 65.0±5.4 ms (range, 59.0-70.0 ms) and 35.7±2.7 ms (range, 34.0-37.0 ms) after PFA. Before ablation and immediately after the recovery of third-degree AVB, the AH interval was prolonged (P<0.05) while the HV interval remained unchanged (P>0.05). After ablation, all 7 canines experienced transient third-degree AVB, with a voltage-dependent duration. Masson staining results revealed no apparent damage in His bundle cells. CONCLUSIONS Within a certain voltage range of pulse electric field, ablation of the maximum His potential in canines can result in transient third-degree AVB, providing a new route for guiding safe ablation of para-Hisian arrhythmia.

RADT-01. BASELINE HIPPOCAMPAL VOLUME AS A PREDICTOR OF NEUROCOGNITIVE CHANGES AFTER WBRT OR HA-WBRT: SECONDARY ANALYSIS OF NRG ONCOLOGY CC001

Abstract PURPOSE Hippocampal volume (HV) is a predictor of neurocognitive function (NCF) in neurodegenerative disease. The role of patient-specific anatomic variables has not been well investigated in patients with brain metastases. This work aimed to evaluate HV at baseline and 6 months as a predictor of NCF and differential benefit from HA-WBRT for patients enrolled on CC001. MATERIALS HV was calculated at baseline and 6 months. HV at baseline and 6 months were correlated with baseline and 2, 4, and 6-month NCF scores (HVLT-R Total and Delayed Recall, Delayed Recognition, TMT Parts A and B, and COWA) using Pearson correlation. Correlation was defined as weak if ρ ≤0.35. A cox proportional hazards model was used to determine the impact of baseline HV on time to NCF failure. RESULTS Of 518 patients randomized on CC001, 277 had baseline imaging, and 135 had 6-month imaging. However, only 87 patients were analyzable at both baseline and 6-month periods. At baseline, HV was not significantly associated with NCF score for any measure (p-value range: 0.06-0.72). Additionally, there was no association between baseline HV and time to NCF failure (p = 0.16). Additionally, the impact of treatment arm allocation on HV was examined but found to be non-significant (p = 0.06). Lastly, baseline HV and NCF scores were noted to have weak correlation at 2, 4, 6, and 12 month timepoints (ρ: range, -0.17-0.15; P-value range, 0.04-0.98). At 6 months, the correlation between HV, baseline NCF change, and 6 month standardized NCF change were also noted to be weak (ρ: range, 0.05-0.16; P-value range, 0.06-0.76). CONCLUSIONS Radiotherapy is known to have deleterious effects on neurocognition. In neurodegenerative disease, HV and rate of HV change are known predictors for NCF. However, baseline HV is not an independent predictor of neurocognitive changes after WBRT or HA-WBRT for patients with brain metastases.

Abstract 17229: Atrioventricular Conduction System Changes During Transcatheter Aortic Valve Replacement (TAVR)

Introduction: Transcatheter aortic valve replacement (TAVR) is complicated by atrioventricular (AV) conduction disturbance in 8-15% of cases. Prior studies have not utilized complete electrophysiology studies (EPS) with continuous recording during TAVR. We sought to better understand the potential utility of intraprocedural electrophysiologic study to identify patients at risk for developing high-grade AV conduction disturbances after TAVR. Hypothesis: Intraprocedural EPS has the potential to identify patients at risk of developing AV conduction block after TAVR. Methods: We conducted a prospective study of TAVR patients at BIDMC between 5/2021-3/2023, excluding those with pre-existing pacemakers/defibrillators. We performed EPS in the cath lab prior to and after valve replacement: atrial pacing to AV block, recording His bundle electrogram (HBE) and RV pacing to assess VA conduction. When possible we recorded the HBE continuously during valve implant. Results: We studied 400 consecutive patients. Forty-three patients (10.8%) received permanent pacemakers (PPMs). Patients receiving PPM had significantly longer post-HV intervals, greater change in HV interval as well as longer AV Wenckebach cycle length after valve replacement. There were no differences in pre-TAVR AV Wenckebach cycle length or VA conduction. Twenty patients (46.5% of all PPMs) were implanted for AV block post discharge, and after adjustment for age, gender, and baseline HV interval, the only predictor of need for post-discharge PPM was peri-TAVR change in HV interval with an adjusted OR of 1.19 per each 10 ms increase. Conclusions: In contrast to prior studies, we have found that EPS at the time of TAVR may have utility in predicting AV conduction disturbances. Larger increases in HV interval and AV block CL were associated with need for PPM. Measuring the peri-TAVR change in HV interval may be useful in predicting late AV block.

Premature Ventricular Contractions From the Left Anterior Fascicle: Electrocardiographic and Electrophysiological Characteristics, Mapping Strategy, and Immediate and Long-Term Catheter Ablation Results

BackgroundLeft anterior fascicle (LAF) premature ventricular contractions (PVC) are rarely reported. We described the electrocardiographic and electrophysiological characteristics of PVCs originating from LAF and evaluated the results of catheter ablation.MethodsThe baseline AH and HV intervals were recorded during normal sinus rhythm (NSR), and the HV interval of LAF-PVC was measured during the procedure. During the index procedure, the conduction interval from the earliest Purkinje potential (PP) site to the His was labeled as time A, the conduction interval from the earliest site to the onset of the QRS as time B, then the HV interval during NSR (HVNSR) is A + B, and the HV interval during PVC (HVPVC) is B-A; a predicted PP time was calculated using HVNSR and HVPVC. The calculated formula is as follows: Predicted target PP = (HVNSR + HVPVC)/2. During the repeat procedure, the mapping strategy only focuses on the earliest retrograde PP due to the injury or block of LAF sustained at the index procedure.ResultsNotably, 24 patients with LAF-PVC were included. The ECG characteristics of PVC exhibited right bundle branch block (RBBB) morphology with right-axis deviation (RAD) in 18 patients and only RAD in 6 patients. The QRS durations of NSR and PVC were 78.8 ± 7.9 and 106.8 ± 12.3 ms, respectively. There was no significant difference between the predicted and mapped PP site (31.5 ± 8.1 vs. 30.6 ± 7.8 ms; P = 0.17). There was a significant difference between the mean axis deviation before and after ablation (46.3 ± 25.4° vs. 18.3 ± 44.1°; P = 0.001); however, only 10 patients had a complete LAF block. Eight patients had a recurrence, the QRS morphology of LAF-PVC became narrower (95.9 ± 17.2 vs. 105.3 ± 16.9 ms, P = 0.003), and 4 patients’s PVC QRS morphology was similar to NSR. During the repeat procedure, the earliest retrograde PP interval was longer than the index procedure in four patients (12.0 ± 1.9 vs. 37.8 ± 1.1 ms; P < 0.001).ConclusionThe target PP site for ablation of the LAF region can be calculated using the HV interval during NSR and PVC at the index procedure. The mapping strategy at repeat procedures focused on the earliest retrograde PP interval.

Association of Pretreatment Hippocampal Volume With Neurocognitive Function in Patients Treated With Hippocampal Avoidance Whole Brain Radiation Therapy for Brain Metastases: Secondary Analysis of NRG Oncology/RTOG 0933

PurposeHippocampal volume (HV) is an established predicting factor for neurocognitive function (NCF) in neurodegenerative disease. Whether the same phenomenon exists with hippocampal-avoidant whole brain radiation therapy is not known; therefore, we assessed the association of baseline HV with NCF among patients enrolled on RTOG 0933. Methods and MaterialsHippocampal volume and total brain volume were calculated from the radiation therapy plan. Hippocampal volume was correlated with baseline and 4-month NCF scores (Hopkins Verbal Learning Test–Revised [HVLT-R] Total Recall [TR], Immediate Recognition, and Delayed Recall [DR]) using Pearson correlation. Deterioration in NCF was defined per the primary endpoint of RTOG 0933(mean 4-month relative decline in HVLT-R DR). Comparisons between patients with deteriorated and nondeteriorated NCF were made using the Wilcoxon test. ResultsForty-two patients were evaluable. The median age was 56.5 years (range, 28-83 years), and 81% had a class II recursive partitioning analysis. The median total, right, and left HVs were 5.4 cm3 (range, 1.9-7.4 cm3), 2.8 cm3 (range, 0.9-4.0 cm3), and 2.7 cm3 (range, 1.0-3.7 cm3), respectively. The median total brain volume was 1343 cm3 (range, 1120.5-1738.8 cm3). For all measures of corrected HV, increasing HV was associated with higher baseline HVLT-R TR and DR scores (ρ: range, 0.35-0.40; P-value range, .009-.024) and 4-month TR and DR scores (ρ: range, 0.29-0.40; P-value range, .009-.04), with the exception of right HV and 4-month DR scores (ρ: 0.29; P = .059). There was no significant association between HV and NCF change between baseline and 4 months. Fourteen patients (33.3%) developed NCF deterioration per the primary endpoint of RTOG 0933. There was no significant difference in HV between patients with deteriorated and nondeteriorated NCF, although in all instances, patients with deteriorated NCF had numerically lower HV. ConclusionsLarger HV was positively associated with improved performance on baseline and 4-month HVLT-R TR and DR scores in patients with brain metastases undergoing hippocampal-avoidant whole brain radiation therapy but was not associated with a change in NCF.

LUM-201 Elicits Greater GH Response than Standard GH Secretagogues in Pediatric Growth Hormone Deficiency

Presentation Type: OralScience Type and Topic: Clinical Trial Introduction: LUM-201 (ibutamoren, formerly MK-0677) is an orally administered GH-secretagogue that stimulates the GH secretagogue receptor (GHSR1a) in the hypothalamus and pituitary. LUM-201 is in development for long-term use in a subset of PGHD patients with moderate growth deficiencies. A diagnosis of PGHD is confirmed by low GH responses to standard GH secretagogues (clonidine, arginine, L-dopa, glucagon, insulin) so it is somewhat counter-intuitive to suggest that children who cannot respond to one GH secretagogue might have favorable responses to LUM-201. Objective: To determine if LUM-201 stimulates GH responses differently than standard GH secretagogues. Methods: 68 naïve-to-treatment, prepubertal children with GHD received two standard GH stimulation tests and a test with a single 0.8 mg/kg dose of LUM-201. The 68 subjects included 20 girls and 48 boys. The median (interquartile range) age was 9.2 years (7.2,10.8), bone age 6.0 years (4.5, 7.9), height SDS -3.3 (-4.5, -2.5), pretreatment height velocity 4.0 cm/y (3.2, 4.6), and baseline IGF-1 51 ng/mL (24,111). Results: The median (interquartile range) of maximal GH response to single dose LUM-201 was 15.0 ng/mL (3.5, 49) and to various pairs of standard stimuli was 5.4 ng/mL (1.8-7.6) (p< 0.00001). The median (IQR) for the difference between GH responses to LUM-201 and standard stimuli was 9.6 ng/ml (1.9, 42). In a multivariate analysis (r2 =0.73) differential GH increased with higher values of baseline IGF-I (p < 0.00001) and standard GH stimulation test (p = 0.047) but was not influenced by age (p = 0.16), sex (p = 0.28), baseline HV (p = 0.24), age-bone age differences (p = 0.33) or height-SDS (p = 0.75). Conclusion: In GHD children, the GH response to single dose LUM-201 greatly exceeds that observed with standard GH testing agents. The difference is greatest among patients with higher baseline values of IGF-I and higher GH responses to standard stimuli. The synergistic actions of LUM-201 on the physiological mechanisms regulating GH release explain why GH responses are greater in response to LUM-201 compared to traditional tests used to diagnose PGHD. Key words: LUM-201, GH deficiency, GH secretagogues, pediatrics, stimulation tests, short stature, pituitary, hypothalamus

Clinical predictors of heart block during atrioventricular nodal reentrant tachycardia ablation: A multicenter 18-year experience.

Catheter ablation is considered the first-line treatment of symptomatic atrioventricular nodal reentrant tachycardia (AVNRT). It has been associated with a risk of heart block (HB) requiring a pacemaker. This study aims to determine potential clinical predictors of complete heart block as a result AVNRT ablation. Consecutive patients undergoing catheter ablation for AVNRT from January 2001 to June 2019 at two tertiary hospitals were included. We defined ablation-related HB as the unscheduled implantation of pacemaker within a month of the index procedure. Use of electroanatomic mapping (EAM), operator experience, inpatient status, age, sex, fluoroscopy time, baseline PR interval, and baseline HV interval was included in univariate and multivariate models to predict HB post ablation. In 1708 patients (56.4 ± 17.0 years, 61% females), acute procedural success was 97.1%. The overall incidence of HB was 1.3%. Multivariate analysis showed that age more than 70 (odds ratio [OR] 7.907, p ≤ .001, confidence interval [CI] 2.759-22.666), baseline PR ≥ 190 ms (OR 2.867, p = .026, CI 1.135-7.239) and no use of EAM (OR 0.306, p = .037, CI 0.101-0.032) were independent predictors of HB. Although the incidence of HB post AVNRT ablation is generally low, patients can be further stratified using three simple predictors.

Response to single ventricular extrastimuli during a wide complex tachycardia: What is the mechanism?

A 29-year-old woman with recurrent palpitations was referred for electrophysiological study of wide QRS complex tachycardia. She had no structural heart disease. Baseline ECG showed no ventricular pre-excitation, and baseline HV interval was 40 ms. Dual atrioventricular (AV) nodal physiology was demonstrated. This article is protected by copyright. All rights reserved.

Cognitive effects of dance-movement intervention in a mixed group of seniors are not dependent on hippocampal atrophy.

Dance-movement intervention (DMI) offers multi-component stimulation of cognitive functions, and it may ameliorate cognitive deficits in the elderly. We investigated the effects of intensive DMI on the cognitive performances of healthy seniors (HS) and patients with mild cognitive impairment (MCI). In addition, we evaluated whether the baseline MRI hippocampus-to-cortex volume (HV:CTV) ratio (i.e., a marker of a typical AD-specific brain atrophy and of distribution of neurofibrillary tangles in the brain) has any impact on the DMI-induced cognitive changes. The research cohort consisted of 99 subjects who were randomly assigned (in a 1:1 ratio) to a DMI group or to a control (life-as-usual) group. The DMI group consisted of 49 subjects with an average age of 69.16years (SD = 5.36), of which 34 were HS (69.4%) and 15 had MCI (30.6%). The control group consisted of 50 subjects aged 68.37years (SD = 6.10), of which 31 were HC (62%) and 19 (38%) had MCI. The DMI group underwent a 6-month intervention, which consisted of 60 lessons supervised by a qualified instructor. Statistical analysis yielded a significant improvement of the figural fluency task as measured by the five-point test in the DMI group as compared to the control group [t (97) = 2.72; p = 0.008]. The baseline HV:CTV ratio was not associated with cognitive changes on that task or with changes in any cognitive domain's Z scores. We observed DMI-induced effect on the test evaluating executive functions across the spectrum of HS and MCI, which was not dependent on the magnitude of AD-related brain pathology.

96-27: Dual decremental limbs in a reciprocating tachycardia- an electrophysiological problem or the lack of it?

Introduction: Characterization of multiple decremental accessory pathways (AP) can be challenging. Methods: N/A Results: A 29-year old male with minimal electrocardiographic preexcitation and normal heart was evaluated for palpitations without a known tachycardia. Baseline HV interval was 13ms and ventricular activation in the para-Hisian region preceded the delta wave. Programmed atrial stimulation subtly but progressively increased preexcitation, as evidenced by loss of physiologic septal activation (loss of r-wave in V1 and q-waves in I, aVL), with short AVERP (<220ms). AV prolongation associated with a negative HV interval during increased pre-excitation and presence of junctional preexcited beats established the diagnosis of a nodoventricular (NV) pathway. Retrograde conduction was evidently through a left lateral AP with slow decremental conduction and long VAERP (340ms). Depending on the decrement in retrograde AP conduction, reciprocating ventricular echo-beats were reproducible during fixed ventricular pacing. A non-sustained tachycardia (CL 310ms-345ms) was induced with ventricular pacing soon after recovery of VA block following adenosine. The QRS morphology of the echo- beats and tachycardia represented fused NV and AV-nodal conduction decided by preceding coupling interval. Catheter ablation of the concealed left AP was successfully performed with resultant VA dissociation. No further ventricular echo-beats or tachycardias were observed. Ablation of the NV pathway was not attempted.

0372: Outcomes of patients with unexplained syncope, bundle branch block and normal electrophysiological study

Little is known about predictors of high-degree atrioventricular block (AVB) in patients without evidence of advanced His-Purkinje conduction disturbances at electrophysiological study (EPS) performed for unexplained syncope associated with bundle branch block (BBB). Identify electrocardiographic predictors of high-degree AVB during follow-up of these patients. Methods. In this multicenter cohort, patients were included if they had: (1) unexplained syncope, (2) bundle branch block (>120ms), (3) no HPCD at EPS, i.e. baseline HV interval <70ms, and absence of 2nd- or 3rd-degree AVB induced with atrial pacing or ajmaline challenge. Among the 150 studied patients (72±14 years, 62% male, mean left ventricular ejection fraction 57±8%), index electrocardiograms showed right BBB (70%; n=105), left BBB (2.7%; n=41), and nonspecific intraventricular conduction disturbance (3%; n=4). A first-degree AVB was noted in 62 patients (44.3%). During a mean follow-up of 584±88 days, high-degree AVB was documented in 25 patients (17%). The presence of a first-degree AVB on the index electrocardiogram was associated with an increased risk of subsequent high-degree AVB [72% vs. 35%; p<0.01]. Conversely, no patients with isolated right BBB developed high-degree AVB after a normal EPS. In patients with unexplained syncope associated with BBB, 16% of patients subsequently developed high-degree AVB despite no evidence of advanced HPCD at EPS. This was more likely to occur in patients with first-degree AVB at presentation. Conversely, this finding never occurred in patients with isolated RBBB and normal PR interval.

Educational attainment and hippocampal atrophy in the Alzheimer's disease neuroimaging initiative cohort

Subjects with higher cognitive reserve (CR) may be at a lower risk for Alzheimer's disease (AD), but the neural mechanisms underlying this are not known. Hippocampal volume loss is an early event in AD that triggers cognitive decline. Regression analyses of the effects of education on MRI-measured baseline HV in 675 subjects (201 normal, 329 with mild cognitive impairment (MCI), and 146 subjects with mild AD), adjusting for age, gender, APOE ɛ4 status and intracranial volume (ICV). Subjects were derived from the Alzheimer's Disease Neuroimaging Initiative (ADNI), a large US national biomarker study. The association between higher education and larger HV was significant in AD (P=0.014) but not in cognitively normal or MCI subjects. In AD, HV was about 8% larger in a person with 20 years of education relative to someone with 6 years of education. There was also a trend for the interaction between education and APOE ɛ4 to be significant in AD (P=0.056). A potential protective association between higher education and lower hippocampal atrophy in patients with AD appears consistent with prior epidemiologic data linking higher education levels with lower rates of incident dementia. Longitudinal studies are warranted to confirm these findings.

The effect of intravenous procainamide on the HV interval at electrophysiologic study.

The His bundle electrogram recorded at electrophysiologic study clearly differentiates atrioventricular (AV) node disease from distal conduction system disease. The distal conduction system may be tested further by infusing procainamide (10-15 mg/kg) intravenously. High-grade distal AV block or prolongation of the HV interval <80 ms was defined as an abnormal response to this test. We retrospectively reviewed the medical records of 79 patients who underwent electrophysiologic study with intravenous procainamide. An abnormal response to procainamide was observed in only 3% of 37 patients with a normal baseline HV (</= ms), in 48% of 27 patients with mild HV prolongation (56 to 70 ms), and in all 15 patients with moderate HV prolongation (<70 ms) (P <0.0001 for the trend). Procainamide induced high-grade AV block in 4 of 28 patients (14%) studied for syncope and in 1 of 51 patients (2%) studied for ventricular tachycardia. Syncope as the indication for electrophysiologic study (P = 0.05) and left bundle branch block morphology (P = 0.03) were predictors of high-grade AV block; baseline HV and QTc intervals were significantly prolonged in patients who developed AV block with procainamide. We identified a strong linear correlation (R = 0.85) between post-drug and baseline HV intervals, with a regression slope of 1.17 +/- 0.09 and an intercept (+/- standard error) of 5.8 +/- 5.0 ms. This linear response to procainamide and published prospective studies support pacing syncope patients with baseline HV <70 ms. Therefore, procainamide infusion during the electrophysiologic study of patients with undifferentiated syncope should be reserved for those with mild HV prolongation from approximately 55 to 70 ms.

Antidromic tachycardia utilizing decremental, latent accessory atrioventricular fibers: Differentiation from adenosine-sensitive ventricular tachycardia

Objectives. We studied two patients with latent, decremental atrioventricular (AV) fibers in whom pre-excitation could be demonstrated only during wide complex tachycardia.Background. The presence of decremental AV fibers participating in antidromic AV reentrant tachycardia is usually suspected by the presence of pre-excitation either in sinus rhythm or during atrial pacing.Methods. Two patients were referred for evaluation and treatment of wide complex tachycardia whose configuration suggested ventricular tachycardia that could be terminated with adenosine infusion. They underwent standard electrophysiologic studies.Results. Baseline AH and HV intervals were normal. No pre-excitation was noted with atrial overdrive at multiple sites or during atrial extrastimulation. Retrograde conduction was present with a sequence compatible with AV node conduction. Sustained wide complex tachycardia was induced with ventricular overdrive pacing. Late atrial premature depolarizations during tachycardia pre-excited the subsequent ventricular activation. Earlier atrial premature depolarizations delayed the subsequent ventricular activation. In one patient, early atrial premature depolarizations terminated the tachycardia without activating the ventricle. In the other patient, spontaneous tachycardia termination was accompanied by ventriculoatrial block. The earliest ventricular activation was at the annulus in the posteroseptal region in one patient and at the left posterior region in the other. Atrioventricular node reentry and atrial tachycardia with by-stander AV fibers were also excluded. These findings establish the diagnosis of antidromic AV reentrant tachycardia utilizing a slow, decrementally conducting AV pathway.Conclusions. This is the first report describing the presence of latent, decremental accessory AV pathways in which conduction was manifest only during antidromic AV reentrant tachycardia. To differentiate these wide complex tachycardias from adenosine-sensitive ventricular tachycardia, we recommend that atrial premature depolarizations be applied during tachycardia to rule out the presence of a latent, decremental AV fiber even in patients who do not otherwise have pre-excitation with atrial pacing techniques.

Bundle branch reentry: A mechanism of ventricular tachycardia in the absence of myocardial or valvular dysfunction

Objective, The aim of this study was to present bundle branch recentry as the mechanism of sustained ventricular tachycardia in the absence of myocardial or valvular dysfunction.Background. Previous reports have documented the relation between structural heart disease and bundle branch reentrant ventricular tachycardia. Myocardial or valvular dysfunction has thus far been recognised as the only anatomic substrate for the development of this tachycardia.Methods. Three patients with a wide QRS complex tachycardia underwent noninvasive and invasive cardiac evaluation and electrophysiologic studies to identify the substrate and mechanism of tachycardia. Catheter ablation of the right bundle branch using radiofrequency current was performed in each patient.Results. The patients were ail men (aged 54, 34 and 72 years) who presented with presyncope, palpitation and cardiac arrest, respectively. Electrocardiography during sinus rhythm revealed nonspecific intraventricular conduction delay in all three patients. Cardiac evaluation revealed no evidence of myocardial or valvular dysfunction in any patient. The baseline HV interval was prolonged in each patient (90, 100 and 75 ms, respectively). Programmed right ventricular stimulation initiated bundle branch reentrant tachycardia with typical left (three patients) and right (one patient) bundle branch block pattern. Catheter ablation of the right bundle branch using radiofrequency current abolished bundle branch reentry in all three patients. After 26-, 13- and 8-month follow-up periods, complete right bundle branch block persisted, and all three patients remained asymptomatic without antiarrhythmic drugs.Conclusions. Sustained bundle branch reentry can be a clinical arrhythmia in patients with no identifiable myocardial or valvular dysfunction except for isolated conduction abnormalities in the His-Purkinje system. This mechanism of tachycardia should be recognized during electrophysiologic evaluation, given the seriousness of this arrhythmia and the availability of effective treatment.

Radiofrequency catheter ablation for treatment of bundle branch reentrant ventricular tachycardia: Results and long-term follow-up

Seven of 120 consecutive patients with inducible sustained ventricular tachycardia (from September 1, 1988 to January 1, 1991) had bundle branch reentrant tachycardia and underwent percutaneous radiofrequency ablation of the right bundle branch. The seven patients had been unsuccessfully treated with a mean of 3 ± 1 drugs. Four patients presented with syncope and three with aborted sudden death. The baseline electrocardiogram revealed a left bundle branch block pattern in three patients and an intraventricular conduction defect in four.The baseline HV interval was prolonged in each case (79 ± 2 ms). With use of programmed ventricular extrastimuli, sustained bundle branch reentrant tachycardia was inducible in all patients at a mean cycle length of 283 ± 17 ms (range 230 to 350). Bundle branch reentrant tachycardia characteristics included atrioventricular dissociation, a His deflection that preceded each QRS complex and spontaneous His to His variation that preceded changes in ventricular tachycardia cycle length.A quadripolar catheter was positioned across the tricuspid valve with the distal electrode tip of the catheter near the right bundle branch. One to three applications of continuous unmodulated radiofrequency current at 300 kHz between the distal electrode and a large posterior skin patch resulted in complete right bundle branch block in all patients, after which none had inducible bundle branch reentrant tachycardia on restudy. On restudy, three of the seven patients had ventricular tachycardia of myocardial origin (not bundle branch reentry). One patient required no therapy; drug or defibrillator therapy was used in the others. After a mean follow-up interval of 12 ± 3 months (range 6 to 29) complete right bundle branch block persisted, there were no spontaneous episodes of ventricular tachycardia and no patient required a permanent pacemaker.Radiofrequency catheter ablation of the right bundle branch is easily performed and is a safe and effective treatment for bundle branch reentrant tachycardia. It is probably the procedure of choice for these highly symptomatic patients.

Electrophysiologic and clinical factors influencing response to class IA antiarrhythmic agents in patients with inducible sustained monomorphic ventricular tachycardia

Clinical and electrophysiologic data from 51 consecutive patients with sustained monomorphic ventricular tachycardia inducible during programmed ventricular stimulation were evaluated to determine what variables predict the response to intravenous class IA antiarrhythmic agents. All patients received acute drug testing in the electrophysiologic laboratory with either intravenous procainamide or intravenous quinidine. Ventricular tachycardia suppression was achieved in 9 out of 51 patients (18%). The age, gender, left ventricular ejection fraction, baseline right ventricular effective refractory period, baseline HV interval, and baseline ventricular tachycardia cycle length were not predictive of ventricular tachycardia suppression with intravenous procainamide or quinidine during programmed ventricular stimulation. The degree of prolongation of the right ventricular effective refractory period after drug administration did not predict success or failure to suppress inducible ventricular tachycardia. The degree of prolongation of the HV interval was also not predictive. In addition, the degree of prolongation of the right ventricular effective refractory period or the HV interval did not predict the change in the ventricular tachycardia cycle length after drug administration in patients who remained inducible. These data indicate that the response to class IA antiarrhythmic agents in patients with inducible sustained monomorphic ventricular tachycardia cannot be predicted on the basis of various clinical and electrophysiologic parameters.

Amrinone: Acute electrophysiologic and hemodynamic effects in patients with congestive heart failure

Amrinone is an effective inotropic agent, but its electrophysiologic effects in humans have not been previously determined. Fifteen patients with congestive heart failure (CHF) New York Heart Association functional class II to IV, underwent an electrophysiologic study after withdrawal of all other cardioactive drugs before and after 10 to 20 μg/kg/min of intravenous amrinone (doses that increased cardiac index and decreased pulmonary capillary wedge pressure and systemic vascular resistance, p < 0.002). Amrinone caused no change in PR, QRS, QTc, AH or HV intervals or maximal corrected sinus node recovery time and had no significant effect on the ventricular effective refractory periods. Amrinone decreased the atrial effective refractory period from 256 ± 40 to 240 ± 38 ms (p = 0.015), and the atrioventricular (AV) nodal functional refractory period from 374 ± 65 to 356 ± 64 ms (p < 0.05), and enhanced maximal 1:1 AV nodal conduction from 371 ± 46 to 334 ± 47 ms (p = 0.006). Nine patients had baseline HV prolongation; this was not affected by amrinone. The frequency of inducible ventricular tachycardia was not significantly affected by amrinone. Holter recordings (24 to 48 hours) were obtained from 10 patients before and after acute oral amrinone dosing (75 to 150 mg every 8 hours). There was no change in the number of ventricular premature contractions per 24 hours (2,197 ± 3,305 vs 2,616 ± 2,436) or number of runs of ventricular tachycardia per 24 hours (10 ± 12 vs 12 ± 13); however, the number of ventricular couplets per 24 hours increased from 22 ± 34 to 52 ± 55 (p = 0.054). Thus, amrinone is safe to use in patients with intraventricular conduction disturbances. It shortens the atrial effective and AV nodal functional refractory period and enhances AV nodal conduction, and it has minimal effects on ventricular arrhythmogenesis during acute drug administration.