Early Catheter Ablation Versus Initial Medical Therapy for Ventricular Tachycardia Storm.

BACKGROUND: Ventricular tachycardia (VT) storm is associated with significantly increased morbidity, mortality, and exponential healthcare utilization. Although catheter ablation (CA) may be curative, there are limited data directly comparing outcomes of early CA with initial medical therapy. METHODS: We compared outcomes of patients presenting with VT storm treated with initial CA versus those treated with initial medical therapy during their first storm presentation in an observational study. Retrospective data from the host institution from January 2014 to April 2020 of 129 patients with their first VT storm presentation were analyzed (58 underwent initial CA, 71 underwent treatment with initial medical therapy). Outcomes were compared in follow-up. RESULTS: Median time to initial CA was 6 days. Over a median follow-up of 702 days, patients who underwent initial CA compared with those treated with initial medical therapy had significantly less: (i) VA recurrence (43% versus 92%; P=0.002); (ii) VT storm recurrence (28% versus 73%; P<0.001); (iii) composite end point of death, heart transplant, VT storm recurrence, and VT-related hospitalization (47% versus 89%; P=0.002); (iv) iatrogenic complications (at 12 months: 17% versus 45%; P<0.001); (v) cardiovascular-related hospitalizations (50% versus 89%; P=0.01); (vi) total number of hospitalizations (median 1 versus 4; P<0.001); and (vi) cumulative days in hospital (median 0.5 versus 18; P<0.001). There were no intraprocedural deaths in patients treated with early CA. CONCLUSION: In an observational setting in which patients presenting with storm, early CA appears superior to initial medical therapy in terms of VT recurrence, storm recurrence, iatrogenic complications, cardiovascular hospitalizations, and cumulative days in hospital in follow-up.

Clinician-Created Educational Video Resources for Shared Decision-making in the Outpatient Management of Chronic Disease: Development and Evaluation Study.

BACKGROUND: The provision of reliable patient education is essential for shared decision-making. However, many clinicians are reluctant to use commonly available resources, as they are generic and may contain information of insufficient quality. Clinician-created educational materials, accessed during the waiting time prior to consultation, can potentially benefit clinical practice if developed in a time- and resource-efficient manner. OBJECTIVE: The aim of this study is to evaluate the utility of educational videos in improving patient decision-making, as well as consultation satisfaction and anxiety, within the outpatient management of chronic disease (represented by atrial fibrillation). The approach involves clinicians creating audiovisual patient education in a time- and resource-efficient manner for opportunistic delivery, using mobile smart devices with internet access, during waiting time before consultation. METHODS: We implemented this educational approach in outpatient clinics and collected patient responses through an electronic survey. The educational module was a web-based combination of 4 short videos viewed sequentially, followed by a patient experience survey using 5-point Likert scales and 0-100 visual analogue scales. The clinician developed the audiovisual module over a 2-day span while performing usual clinical tasks, using existing hardware and software resources (laptop and tablet). Patients presenting for the outpatient management of atrial fibrillation accessed the module during waiting time before their consultation using either a URL or Quick Response (QR) code on a provided tablet or their own mobile smart devices. The primary outcome of the study was the module's utility in improving patient decision-making ability, as measured on a 0-100 visual analogue scale. Secondary outcomes were the level of patient satisfaction with the videos, measured with 5-point Likert scales, in addition to the patient's value for clinician narration and the module's utility in improving anxiety and long-term treatment adherence, as represented on 0-100 visual analogue scales. RESULTS: This study enrolled 116 patients presenting for the outpatient management of atrial fibrillation. The proportion of responses that were "very satisfied" with the educational video content across the 4 videos ranged from 93% (86/92) to 96.3% (104/108) and this was between 98% (90/92) and 99.1% (107/108) for "satisfied" or "very satisfied." There were no reports of dissatisfaction for the first 3 videos, and only 1% (1/92) of responders reported dissatisfaction for the fourth video. The median reported scores (on 0-100 visual analogue scales) were 90 (IQR 82.5-97) for improving patient decision-making, 89 (IQR 81-95) for reducing consultation anxiety, 90 (IQR 81-97) for improving treatment adherence, and 82 (IQR 70-90) for the clinician's narration adding benefit to the patient experience. CONCLUSIONS: Clinician-created educational videos for chronic disease management resulted in improvements in patient-reported informed decision-making ability and expected long-term treatment adherence, as well as anxiety reduction. This form of patient education was also time efficient as it used the sunk time cost of waiting time to provide education without requiring additional clinician input.

Ablation of ventricular arrhythmia in patients with heart failure.

Ventricular arrhythmias (VAs) in patients with cardiomyopathy and advanced-symptom class heart failure (HF) are associated with significant morbidity and mortality. VAs are typically managed with antiarrhythmic drug therapy and implantable cardiac defibrillators (ICD). Although ICDs are highly effective in reducing sudden cardiac death by termination of VA, they do not prevent arrhythmia recurrences. Recurrent shocks are not only associated with poor quality of life but also progressive HF and increased mortality and morbidity. Radiofrequency catheter ablation has emerged as an important therapeutic option for patients with drug-refractory ventricular tachycardia to reduce or prevent ICD shocks.

Acoustic signal emission monitoring as a novel method to predict steam pops during radiofrequency ablation: preliminary observations.

UNLABELLED: Steam pop is an explosive rupture of cardiac tissue caused by tissue overheating above 100 °C, resulting in steam formation, predisposing to serious complications associated with radiofrequency (RF) ablations. However, there are currently no reliable techniques to predict the occurrence of steam pops. We propose the utility of acoustic signals emitted during RF ablation as a novel method to predict steam pop formation and potentially prevent serious complications. METHODS: Radiofrequency generator parameters (power, impedance, and temperature) were temporally recorded during ablations performed in an in vitro bovine myocardial model. The acoustic system consisted of HTI-96-min hydrophone, microphone preamplifier, and sound card connected to a laptop computer. The hydrophone has the frequency range of 2 Hz to 30 kHz and nominal sensitivity in the range -240 to -165 dB. The sound was sampled at 96 kHz with 24-bit resolution. Output signal from the hydrophone was fed into the camera audio input to synchronize the video stream. An automated system was developed for the detection and analysis of acoustic events. RESULTS: Nine steam pops were observed. Three distinct sounds were identified as warning signals, each indicating rapid steam formation and its release from tissue. These sounds had a broad frequency range up to 6 kHz with several spectral peaks around 2-3 kHz. Subjectively, these warning signals were perceived as separate loud clicks, a quick succession of clicks, or continuous squeaking noise. Characteristic acoustic signals were identified preceding 80% of pops occurrence. Six cardiologists were able to identify 65% of acoustic signals accurately preceding the pop. An automated system identified the characteristic warning signals in 85% of cases. The mean time from the first acoustic signal to pop occurrence was 46 ± 20 seconds. The automated system had 72.7% sensitivity and 88.9% specificity for predicting pops. CONCLUSIONS: Easily identifiable characteristic acoustic emissions predictably occur before imminent steam popping during RF ablations. Such acoustic emissions can be carefully monitored during an ablation and may be useful to prevent serious complications during RF delivery.

Electrogram-gated radiofrequency ablations with duty cycle power delivery negate effects of ablation catheter motion.

BACKGROUND: Cardiac and respiratory movements cause catheter instability. Lateral catheter sliding over target endocardial surface can lead to poor tissue contact and unpredictable lesion formation. We describe a novel method of overcoming the effects of lateral catheter sliding movements using an electrogram-gated pulsed power ablation. METHODS AND RESULTS: All ablations were performed on a thermochromic gel myocardial phantom. Ablation settings were randomized to conventional (nongated) 30 W versus electrogram-gated at 20% duty cycle (30 W average power) at 0-, 3-, 6-, and 9-mm lateral sliding distances. Forty-eight radiofrequency ablations were performed. Deeper lesions were created in electrogram-gated versus conventional ablations at 3 mm (4.36±0.08 versus 4.05±0.17 mm; P=0.009), 6 mm (4.39±0.10 versus 3.44±0.15 mm; P<0.001), and 9 mm (4.41±0.06 versus 2.94±0.16 mm; P<<0.001) sliding distances. Electrogram-gated ablations created consistent lesions at a quicker rate of growth in depth when compared with conventional ablations (P<0.001). CONCLUSIONS: (1) Lesion depth decreases and length increases in conventional ablations with greater degrees of lateral catheter movements; (2) electrogram-gated pulsed radiofrequency delivery negated the effects from lateral catheter movement by creating consistently deeper lesions irrespective of the degree of catheter movement; and (3) target lesion depths were reached significantly faster in electrogram-gated than in conventional ablations.

Atrial tachycardias utilizing the Ligament of Marshall region following single ring pulmonary vein isolation for atrial fibrillation.

BACKGROUND: Organized atrial tachycardias (OATs) after pulmonary vein isolation (PVI) procedure are common. Arrhythmia mechanisms include mitral annular, ring gap, or roof-dependent gap-related flutters. In this series, we describe a mechanism of arrhythmia utilizing the ridge between left pulmonary vein (PV) and left atrial appendage (LAA) in the Ligament of Marshall (LOM) region. METHODS AND RESULTS: Five tachycardias involving the LOM region were identified from a group of 240 patients who underwent a single ring PVI procedure for symptomatic atrial fibrillation. The common characteristics of these tachycardias were the endocardial breakout over a broad area adjacent to the LOM region, presence of presystolic or mid-diastolic potentials, and abolition by ablation of the presystolic or mid-diastolic potentials remote from the endocardial breakout site. In all five cases, tachycardias were present after isolation of the veins and posterior left atria. All demonstrated characteristic areas of very slow conduction in the LOM region highlighted by presence of either low voltage, long duration fractionated potentials, or mid-diastolic potentials with a fixed temporal relationship to the subsequent endocardial activation. The pattern of activation and termination of tachycardia during ablation was consistent with an arrhythmia utilizing an electrically insulated tract within LOM and the PV-LAA ridge region. CONCLUSIONS: We identified a pattern of arrhythmias involving a concealed presystolic component and a broad endocardial breakout site related to the LOM region. Successful ablation site involved careful identification of small diastolic potentials in the LAA/ridge region or adjacent to the coronary sinus.

Intramyocardial adiposity after myocardial infarction: new implications of a substrate for ventricular tachycardia.

BACKGROUND: Collagen has been attributed as the principal structural substrate of ventricular tachycardia (VT) after myocardial infarction (MI), even though adiposity of myocardium after MI is well recognized histologically. We investigated the effects of intramyocardial adiposity compared with collagen on electrophysiological properties, connexin43 expression, and VT induction after MI. METHODS AND RESULTS: Simultaneous left ventricular plunge-needle, noncontact mapping was performed in sheep without MI (MI-; n=5), with MI and inducible VT (MI+VT+; n=7), and with MI and no inducible VT (MI+VT-; n=8). Histological intramyocardial quantity of adipose and collagen and degree of discontinuity were coregistered with electrophysiological parameters (MI+; 290 specimens). Additional assessment of connexin43 expression was performed. Left ventricular scar contained a body mass-independent abundance of adipocytes (adipose:collagen=0.8). Increased adipose density and discontinuity contributed to a greater inverse correlation (r) with conduction velocity (r for adipose=0.39, r for discontinuity=0.45, r for collagen=0.26) and electrogram amplitude (r for adipose=0.73, r for contiguity=0.77, r for collagen=0.68) compared with collagen. Collagen density was similar between the MI+ groups (P>0.29). However, the MI+VT+ group demonstrated a significant (all P≤0.01) increase in adipose (8%) and discontinuity (qualitative) and decrease in conduction velocity (13%) and electrogram amplitude (21%) at MI borders compared with the MI+VT- group. In scar, myocytes adjacent to fibrofatty interfaces demonstrated increased connexin43 lateralization. A gradient increase in adipose was observed at sites that supported preferential presystolic VT activation and exhibited attenuation of excitation wavelength (P<0.001). CONCLUSIONS: Intramyocardial adiposity, in association with myocardial discontinuity within left ventricular scar borders, is a significant factor associated with altered electrophysiological properties, aberrant connexin43 expression, and increased propensity for VT after MI.

High spatial resolution thermal mapping of radiofrequency ablation lesions using a novel thermochromic liquid crystal myocardial phantom.

BACKGROUND: Radiofrequency (RF) ablation causes thermal mediated irreversible myocardial necrosis. This study aimed to (i) characterize the thermal characteristics of RF ablation lesions with high spatial resolution using a thermochromic liquid crystal (TLC) myocardial phantom; and (ii) compare the thermochromic lesions with in vivo and in vitro ablation lesions. METHODS AND RESULTS: The myocardial phantom was constructed from a vertical sheet of TLC film, with color change between 50 °C (red) to 78 °C (black), embedded within a gel matrix, with impedance titrated to equal that of myocardium. Saline, with impedance titrated to blood values at 37 °C, was used as supernatant. A total of 51 RF ablations were performed. This comprised 17 ablations in the thermochromic gel phantom, bovine myocardial in vitro targets and ovine in vivo ablations, respectively. There was no difference in lesion dimensions between the thermochromic gel and in vivo ablations (lesion width 10.2 ± 0.2 vs 10.2 ± 2.4, P = 0.93; and depth 6.3 ± 0.1 vs 6.5 ± 1.7, P = 0.74). The spatial resolution of the thermochromic film was tested using 2 thermal point-sources that were progressively opposed and was demonstrated to be <300 µm. CONCLUSIONS: High spatial resolution thermal mapping of in vitro RF lesions with spatial resolution of at least 300 µm is possible using a thermochromic liquid crystal myocardial phantom model, with a good correlation to in vivo RF ablations. This model may be useful for assessing the thermal characteristics of RF lesions created using different ablation parameters and catheter technologies.

In vivo evaluation of virtual electrode mapping and ablation utilizing a direct endocardial visualization ablation catheter.

BACKGROUND: Radiofrequency (RF) ablation utilizing direct endocardial visualization (DEV) requires a "virtual electrode" to deliver RF energy while preserving visualization. This study aimed to: (1) examine the virtual electrode RF ablation efficacy; (2) determine the optimal power and duration settings; and (3) evaluate the utility of virtual electrode unipolar electrograms. METHODS AND RESULTS: The DEV catheter lesions were compared to lesions formed using a 3.5 mm open irrigated tip catheter within the right atria of 12 sheep. Generator power settings for DEV were titrated from 12W, 14W and 16W for 20, 30 and 40 seconds duration with 25 mL/min saline irrigation. Standard irrigated tip catheter settings of 30W, 50°C for 30 seconds and 30 mL/min were used. The DEV lesions were significantly greater in surface area and both major and minor axes compared to irrigated tip lesions (surface area 19.43 ± 9.09 vs 10.88 ± 4.72 mm, P<0.01) with no difference in transmurality (93/94 vs 46/47) or depth (1.86 ± 0.75 vs 1.85 ± 0.57 mm). Absolute electrogram amplitude reduction was greater for DEV lesions (1.89 ± 1.31 vs 1.49 ± 0.78 mV, P = 0.04), but no difference in percentage reduction. Pre-ablation pacing thresholds were not different between DEV (0.79 ± 0.36 mA) and irrigated tip (0.73 ± 0.25 mA) lesions. There were no complications noted during ablation with either catheter. CONCLUSIONS: Virtual electrode ablation consistently created wider lesions at lower power compared to irrigated tip ablation. Virtual electrode electrograms showed a comparable pacing and sensing efficacy in detecting local myocardial electrophysiological changes.