Association between proactive esophageal cooling and increased lab throughput.

INTRODUCTION: Proactive esophageal cooling has been FDA cleared to reduce the likelihood of ablation-related esophageal injury resulting from radiofrequency (RF) cardiac ablation procedures. Data suggest that procedure times for RF pulmonary vein isolation (PVI) also decrease when proactive esophageal cooling is employed instead of luminal esophageal temperature (LET) monitoring. Reduced procedure times may allow increased electrophysiology (EP) lab throughput. We aimed to quantify the change in EP lab throughput of PVI cases after the introduction of proactive esophageal cooling. METHODS: EP lab throughput data were obtained from three EP groups. We then compared EP lab throughput over equal time frames at each site before (pre-adoption) and after (post-adoption) the adoption of proactive esophageal cooling. RESULTS: Over the time frame of the study, a total of 2498 PVIs were performed over a combined 74 months, with cooling adopted in September 2021, November 2021, and March 2022 at each respective site. In the pre-adoption time frame, 1026 PVIs were performed using a combination of LET monitoring with the addition of esophageal deviation when deemed necessary by the operator. In the post-adoption time frame, 1472 PVIs were performed using exclusively proactive esophageal cooling, representing a mean 43% increase in throughput (p < .0001), despite the loss of two operators during the post-adoption time frame. CONCLUSION: Adoption of proactive esophageal cooling during PVI ablation procedures is associated with a significant increase in EP lab throughput, even after a reduction in total number of operating physicians in the post-adoption group.

Contemporary procedure characteristics and outcomes of accessory atrioventricular pathway ablations in an integrated community-based health care system using a tiered approach.

BACKGROUND: Since the early descriptions of large series of accessory atrioventricular pathway ablations in adults and adolescents over 20 years ago, there have been limited published reports based on more recent experiences of large referral centers. We aimed to characterize accessory pathway distribution and features in a large community-based population that influence ablation outcomes using a tiered approach to ablation. METHODS: Retrospective analysis of 289 patients (age 14-81) who underwent accessory ablation from 2015-2019 was performed. Pathways were categorized into anteroseptal, left freewall, posteroseptal, and right freewall locations. We analyzed patient and pathway features to identify factors associated with prolonged procedure time parameters. RESULTS: Initial ablation success rate was 94.7% with long-term success rate of 93.4% and median follow-up of 931 days. Accessory pathways were in left freewall (61.6%), posteroseptal (24.6%), right freewall (9.6%), and anteroseptal (4.3%) locations. Procedure outcome was dependent on pathway location. Acute success was highest for left freewall pathways (97.1%) with lowest case times (144 ± 68 min) and fluoroscopy times (15 ± 19 min). Longest procedure time parameters were seen with anteroseptal, left anterolateral, epicardial-coronary sinus, and right anterolateral pathway ablations. CONCLUSIONS: In this community-based adult and adolescent population, majority of the accessory pathways are in the left freewall and posteroseptal region and tend to be more easily ablated. A tiered approach with initial use of standard ablation equipment before the deployment of more advance tools, such as irrigated tips and 3D mapping, is cost effective without sacrificing overall efficacy.

High-resolution electrical mapping of depolarization and repolarization alternans in an ischemic dog model.

Cardiac electrical alternans have been associated with spontaneous ventricular arrhythmias during myocardial ischemia. The study aims were to use a new algorithm to measure depolarization and repolarization alternans from epicardial electrograms in an ischemia model and to evaluate which features are predictive of ventricular fibrillation (VF). The left anterior descending coronary artery was occluded in 21 dogs, of which 6 developed spontaneous VF. Four seconds of unipolar epicardial electrograms was recorded before and 5 min after occlusion from an 8 x 14-electrode plaque placed on the anterior left ventricle. Alternans amplitudes were estimated with a triangular wave-fitting algorithm and for each unipolar electrogram for various measurements of the QRS and ST-T wave amplitude. The root mean square error was computed for each fit. Receiver-operator characteristic curves were used to determine whether prevalence of alternans having estimated alternans amplitude-to-error ratio (A/E) above a given threshold could distinguish the dogs who had and did not have spontaneous VF. The prevalence of alternans after ischemia was highly predictive of VF when measured both during depolarization (sensitivity of 83% and specificity of 87%) and during repolarization (sensitivity of 100% and specificity of 73%). The optimal alternans A/E ranged from 1 to 4. There were no differences in the level of discordance or alternans amplitude between dogs who developed VF versus dogs who did not. The prevalence of alternans in the ventricles may be the key risk factor for developing VF during myocardial ischemia when short-term recordings are used.

Circadian and gender effects on repolarization in healthy adults: a study using harmonic regression analysis.

BACKGROUND: Sudden cardiac death and myocardial infarction have a circadian variation with a peak incidence in the early morning hours. Increased dispersion of repolarization facilitates the development of conduction delay necessary to induce sustained arrhythmia. Both QT-dispersion and T-wave peak to T-wave end (TpTe) have been proposed as markers of dispersion of myocardial repolarization. METHODS: Forty healthy adults (20 women), age 35-67 years old, with normal EKGs, echocardiograms, stress tests, and tilt-table tests were analyzed during a 27-hour hospital stay. EKGs were done at eight different time points. QT-intervals, QT-dispersion, and TpTe were measured at each time point. Harmonic regression was used to model circadian periodicity, P < 0.05 was considered significant. RESULTS: The composite QT-interval was longer in women than in men (416 + or - 17 msec vs 411 + or - 20 msec, respectively, P = 0.006). The QT-dispersion among all leads was greater in men than women (37 + or - 13 msec vs 30 + or - 11 msec, respectively, P < 0.0001); a similar difference was found in the precordial leads. Harmonic regression showed that QT-dispersion had a significant circadian variation, primarily in men. In men, the maximum QT-dispersion occurred at 6 AM (45 + or - 15 msec). TpTe also had a significant circadian variation that was not affected by gender in the majority of leads. CONCLUSIONS: A circadian variation exists in the dispersion of myocardial repolarization, as measured by both TpTe and QT-dispersion. Men and women have a different circadian variation pattern. Further studies regarding the mechanisms and clinical implications are needed.

Acute blood pressure effects at the onset of supraventricular and ventricular tachycardia.

This study was designed to assess the effects of tachycardia origin, the significance of atrial contribution, and the effects of left ventricular ejection fraction on hemodynamically tolerated ventricular tachycardia (VT) and supraventricular tachycardia (SVT). Forty-one subjects with inducible hemodynamically tolerated VT (n = 24) or SVT (n = 17) with mean ages of 60 +/- 13 and 40 +/- 16 years and mean ejection fractions of 32 +/- 15% and 59 +/- 5%, respectively, were studied. VT and SVT were induced by standard techniques, and femoral arterial blood pressure (BP) was recorded for 30 seconds. After tachycardia termination, with >/=3 minutes between conditions, ventricular overdrive pacing was performed from the right ventricular (RV) apex and then the RV outflow tract, followed by atrioventricular (AV) pacing at the tachycardia cycle length. Mean BP was measured every 5 seconds. Linear regression methods were used to model BP response for the 2 groups. There was a significant increase in BP over the 20-second interval after the induction of VT and SVT (0.55 +/- 0.21 and 1.0 +/- 0.20 mm Hg/s, respectively, p <0.05). In patients with hemodynamically tolerated VT, RV apex and RV outflow tract pacing at the tachycardia cycle length decreased BP by 6.7 +/- 2.0 (p <0.002) and 4.7 +/- 2.5 mm Hg (p = 0.06), respectively. AV pacing at the tachycardia cycle length did not improve BP compared with RV pacing alone. In patients with SVT, RV apex and RV outflow pacing at the tachycardia cycle length decreased BP by 5.6 +/- 2.9 (p = 0.05) and 4.1 +/- 2.7 mm Hg (p = 0.12), respectively. However, AV pacing at the tachycardia cycle length was associated with improved BP response over RV pacing alone. Increased age and lower ejection fraction adversely influenced BP response in the VT group and longer cycle length, and higher preinduction BP favorably influenced BP response in the SVT group. The determinants of BP response after tachycardia onset are complex and differ in patients with SVT and VT.

Age and gender difference in ST height at rest and after double autonomic blockade in normal adults.

BACKGROUND: ST elevation is commonly seen in young, healthy men. The exact mechanisms that cause ST height to be greater in young men are not yet completely understood. The purpose of the present study was to determine whether autonomic tone is responsible for age and gender differences in ST height. METHODS: Gender and age differences in ST height were studied at rest and after double autonomic blockade (DAB) with atropine and propranolol. Fifty healthy men and women were included (16 men, 14 women, age 23-32 years; 9 men, 11 women, age 65-79 years). Twelve-lead ECGs were registered at rest and after DAB. Leads II and V(1)-V(4) were chosen for analysis. ST height (in mm) was measured manually at the J-point, and 40 ms and 80 ms after the J-point. Values were corrected for QRS amplitude. RESULTS: Gender and age differences in ST height were seen in both rest and DAB data. Men had greater ST height compared to women at J-point, 40 and 80 ms after the J-point (P < or = 0.0001), and younger subjects had greater ST height than older subjects at J-point (P = 0.0140), 40 and 80 ms after the J-point (P < or = 0.0001). DAB did not change ST height at J-point or at 40 ms, but increased ST height at 80 ms. Women had less of an increase in ST height following DAB than men did. CONCLUSIONS: ST elevation in the absence of structural or electrical heart disease is mainly seen in young men. Age and gender difference persist after DAB and thus are not due to differences in autonomic tone.

Is there a correlation between ventricular fibrillation cycle length and electrophysiological and anatomic properties of the canine left ventricle?

We hypothesized that myocardial infarction-related alterations in ventricular fibrillation (VF) cycle length (VFCL) would correlate with changes in local cardiac electrophysiological and anatomic properties. An electrophysiological study was performed in normal, subacute, and chronic infarction mongrel dogs. VF was induced by programmed electrical stimulation and mean and minimum early and late VFCL was determined and correlated with local electrophysiological and anatomic properties. Effective refractory period (ERP), activation recovery time (ART), ERP/ART ratio, threshold, and ERP and ART dispersion were determined at 112 sites on the anterior left ventricle. Wave front progression was analyzed over a 2-s period. The extent of local tissue necrosis and of myocardial fiber disarray was also evaluated. The early mean VFCL was significantly longer in the subacute infarction (149 +/- 35 ms) and chronic infarction dogs (129 +/- 18 ms) compared with control dogs (102 +/- 15 ms; P < 0.0001 for both comparisons) as was the early minimum VFCL with similar trends seen during late VF. Complete epicardial reentrant circuits were significantly more common in normal dogs (4.3 +/- 2.4, 22.4% of cycles) than in subacute (0.75 +/- 0.96, 5.3% of cycles, P < 0.05 vs. normal) and chronic infarction dogs (1.3 +/- 1.3, 7.5% of cycles, P < 0.05 vs. normal). There was a poor correlation between the mean and minimum early and late VFCL and local electrophysiological and anatomic properties (R(2) < 0.2 for all comparisons) with a much better correlation between average mean and minimum VFCL (over the entire plaque) and global ERP and ART dispersion during early and late VF. In conclusion, VFCL in normal and infarcted myocardium shows a poor correlation with local ventricular electrophysiological and anatomic properties measured in sinus rhythm. However, there was a much better correlation between the average VFCL with global dispersion of repolarization. The lack of correlation between local VFCL and refractoriness and the infrequent occurrence of epicardial reentry suggests that intramural reentry may be the primary mechanism of VF in this model.

Menstrual cycle and ST height.

BACKGROUND: Sex hormones and menstrual cycle effects on ST height have not yet been clearly identified. METHODS: Twenty-two young, healthy women (aged 22-32 years) were included in this study. Twelve-lead ECGs were registered during menses, follicular and luteal phase of the menstrual cycle at baseline, and after double autonomic blockade (DAB). Chest leads V2-V4 and limb leads I and II were chosen for analysis. ST height was measured manually at J-Point and 40 ms after the J-Point, and values were corrected for QRS amplitude (J-Point/QRS, 40 ms/QRS). Repeated measure ANOVA was used to analyze differences in ST height among the three phases of the menstrual cycle. A P-value < 0.05 was considered as significant. RESULTS: At baseline, ST height, QTc, and T wave amplitude were not significantly different among the three phases of the menstrual cycle. After double autonomic blockade, ST height at 40 ms, J-Point/QRS, and 40 ms/QRS was significantly higher during follicular versus luteal phase (0.152 +/- 0.413 mm versus -0.007 +/- 0.427 mm, P = 0.0059 at 40 ms; -0.001 +/- 0.030 versus -0.015 +/- 0.032, P = 0.0039 at J-Point/QRS; 0.013 +/- 0.031 versus -0.004 +/- 0.032, P = 0.0005 at 40 ms/QRS) as was the QTc. ST height differences at J-Point were not significantly different (-0.046 +/- 0.395 mm follicular, -0.167 +/- 0.448 mm luteal, and -0.083 +/- 0.492 mm menses, P = 0.1014). CONCLUSION: ST height and QTc varied among the three phases of the menstrual cycle, predominantly after double autonomic blockade. Female sex hormones that vary throughout the menstrual cycle may modulate measures of repolarization.