Use of three-dimensional electroanatomic mapping for epicardial access: needle tracking, electrographic characteristics, and clinical application.

AIMS: Pericardiocentesis is usually completed under fluoroscopy. The electroanatomic mapping (EAM) system allows visualizing puncture needle tip (NT) while displaying the electrogram recorded from NT, making it possible to obtain epicardial access (EA) independent of fluoroscopy. This study was designed to establish and validate a technique by which EA is obtained under guidance of three-dimensional (3D) EAM combined with NT electrogram. METHODS AND RESULTS: 3D shell of the heart was generated, and the NT was made trackable in the EAM system. Unipolar NT electrogram was continuously monitored. Penetration into pericardial sac was determined by an increase in NT potential amplitude and an injury current. A long guidewire of which the tip was also visible in the EAM system was advanced to confirm EA. Epicardial access was successfully obtained without complication in 13 pigs and 22 patients. In the animals, NT potential amplitude was 3.2 ± 1.0 mV when it was located in mediastinum, 5.2 ± 1.6 mV when in contact with fibrous pericardium, and 9.8 ± 2.8 mV after penetrating into pericardial sac (all P ≤ 0.001). In human subjects, it measured 1.54 ± 0.40 mV, 3.61 ± 1.08 mV, and 7.15 ± 2.88 mV, respectively (all P < 0.001). Fluoroscopy time decreased in every 4-5 cases (64 ± 15, 23 ± 17, and 0 s for animals 1-4, 5-8, 9-13, respectively, P = 0.01; 44 ± 23, 31 ± 18, 4±7 s for patients 1-7, 8-14, 15-22, respectively, P < 0.001). In five pigs and seven patients, EA was obtained without X-ray exposure. CONCLUSION: By tracking NT in the 3D EAM system and continuously monitoring the NT electrogram, it is feasible and safe to obtain EA with minimum or no fluoroscopic guidance.

Initial clinical experience of atrial fibrillation ablation guided by a cryoballoon-compatible, magnetic-based circular catheter.

INTRODUCTION: The circular catheter compatible with current cryoballoon system for atrial fibrillation (AF) ablation is exclusively sensed by impedance-based electro-anatomical mapping (EAM) system, limiting the accuracy of maps. We aim to investigate the feasibility and safety of a magnetic-based circular mapping catheter for AF ablation with cryoballoon. METHODS: Nineteen consecutive patients who underwent pulmonary vein isolation (PVI) with cryoballoon for paroxysmal or persistent AF were included. EAMs of left atrium (LA) created by the LASSOSTAR™NAV catheter (Lassostar map) before and after PVI were compared to that generated by a high-density mapping catheter (Pentaray map) from different aspects including structural similarity, PV angle, LA posterior wall (LAPW) and low voltage areas (LVAs), and the amplitude of far field electrograms (FFEs) recorded by catheters. RESULTS: All patients had successful PVI without major complications. With similar mapping time and density, the LA volume calculated from the Pentaray map and Lassostar map were comparable. There were no significant differences in PV angle of all PVs and PW area (16.8 ± 3.2 vs. 17.1 ± 2.8, p = .516) between Pentaray map and Lassostar map. High structural similarity score was observed between two maps (0.783 in RAO/LAO view and 0.791 in PA view). Lassostar map detected lesser but not statistically significant extension of LVA (13.9% vs. 18.3%, p = .07). Amplitude of FFE was larger at the right superior PV on Lassostar map (0.21 ± 0.16 vs. 0.14 ± 0.11 mV, p = .041) compared to that on the Pentaray map. CONCLUSION: In our initial experience, PVI with cryoballoon and magnetic-based circular LASSOSTAR™NAV catheter was safe and effective based on the accurate LA geometry it created.

Incidence of cryoballoon expansion dislodgement during pulmonary vein isolation-An underappreciated frequent cause of incomplete isolation.

BACKGROUND: Cryoballoon ablation for atrial fibrillation (AF) requires adequate contact between the pulmonary vein (PV) antrum and cryoballoon. The surge of intraballoon pressure during the initial phase of ablation may change the balloon's shape and compliance, resulting in balloon dislodgement and loss of PV occlusion. Without continuous monitoring, this phenomenon is often undetected but can be associated with incomplete PV isolation (PVI). METHODS: Primary cryoablation of AF was performed in 15 patients. PV occlusion status pre- and post-freezing were analyzed with intracardiac echocardiography (ICE) and dielectric imaging-based occlusion tool (DIOT) to calculate the incidence of expansion dislodgement of cryoballoon. RESULTS: A total of 105 cryoablation applications were performed on 57 veins, including three common ostiums of left pulmonary veins. In the evaluation of PV occlusion, both modalities reported consistent results in 86.7% of the assessments. Despite complete PV occlusion before ablation, peri-balloon leak after initiation of freezing was detected by ICE in 5/22 (22.7%) applications and by DIOT in 8/25 (32%) applications. CONCLUSION: Incidence of expansion dislodgement of the cryoballoon was detected in one-fourth to one-third of cryoablation applications depending on the imaging modality used, which was clinically frequent and significant.

Vasovagal Responses to Human Monomorphic Ventricular Tachycardia: Hemodynamic Implications From Sinus Rate Analysis.

BACKGROUND: Factors determining hemodynamic stability during human ventricular tachycardia (VT) are incompletely understood. OBJECTIVES: The purposes of this study were to characterize sinus rate (SR) responses during monomorphic VT in association with hemodynamic stability and to prospectively assess the effects of vagolytic therapy on VT tolerance. METHODS: This is a retrospective analysis of patients undergoing scar-related VT ablation. Vasovagal responses were evaluated by analyzing sinus cycle length before VT induction and during VT. SR responses were classified into 3 groups: increasing (≥5 beats/min, sympathetic), decreasing (≥5 beats/min, vagal), and unchanged, with the latter 2 categorized as inappropriate SR. In a prospective cohort (n = 30) that exhibited a failure to increase SR, atropine was administered to improve hemodynamic tolerance to VT. RESULTS: In 150 patients, 261 VT episodes were analyzed (29% untolerated, 71% tolerated) with median VT duration 1.6 minutes. A total of 52% of VT episodes were associated with a sympathetic response, 31% had unchanged SR, and 17% of VTs exhibited a vagal response. A significantly higher prevalence of inappropriate SR responses was observed during untolerated VT (sustained VT requiring cardioversion within 150 seconds) compared with tolerated VT (84% vs 34%; P < 0.001). Untolerated VT was significantly different between groups: 9% (sympathetic), 82% (vagal), and 32% (unchanged) (P < 0.001). Atropine administration improved hemodynamic tolerance to VT in 70%. CONCLUSIONS: Nearly one-half of VT episodes are associated with failure to augment SR, indicative of an under-recognized pathophysiological vasovagal response to VT. Inappropriate SR responses were more predictive of hemodynamic instability than VT rate and ejection fraction. Vagolytic therapy may be a novel method to augment blood pressure during VT.

Identification of Human Ventricular Tachycardia Demarcated by Fixed Lines of Conduction Block in a 3-Dimensional Hyperboloid Circuit.

BACKGROUND: The circuit boundaries for reentrant ventricular tachycardia (VT) have been historically conceptualized within a 2-dimensional (2D) construct, with their fixed or functional nature unresolved. This study aimed to examine the correlation between localized lines of conduction block (LOB) evident during baseline rhythm with lateral isthmus boundaries that 3-dimensionally constrain the VT isthmus as a hyperboloid structure. METHODS: A total of 175 VT activation maps were correlated with isochronal late activation maps during baseline rhythm in 106 patients who underwent catheter ablation for scar-related VT from 3 centers (42% nonischemic cardiomyopathy). An overt LOB was defined by a deceleration zone with split potentials (≥20 ms isoelectric segment) during baseline rhythm. A novel application of pacing within deceleration zone (≥600 ms) was implemented to unmask a concealed LOB not evident during baseline rhythm. LOB identified during baseline rhythm or pacing were correlated with isthmus boundaries during VT. RESULTS: Among 202 deceleration zones analyzed during baseline rhythm, an overt LOB was evident in 47%. When differential pacing was performed in 38 deceleration zones without overt LOB, an underlying concealed LOB was exposed in 84%. In 152 VT activation maps (2D=53, 3-dimensional [3D]=99), 69% of lateral boundaries colocalized with an LOB in 2D activation patterns, and the depth boundary during 3D VT colocalized with an LOB in 79%. In VT circuits with isthmus regions that colocalized with a U-shaped LOB (n=28), the boundary invariably served as both lateral boundaries in 2D and 3D. Overall, 74% of isthmus boundaries were identifiable as fixed LOB during baseline rhythm or differential pacing. CONCLUSIONS: The majority of VT circuit boundaries can be identified as fixed LOB from intrinsic or paced activation during sinus rhythm. Analysis of activation while pacing within the scar substrate is a novel technique that may unmask concealed LOB, previously interpreted to be functional in nature. An LOB from the perspective of a myocardial surface is frequently associated with intramural conduction, supporting the existence of a 3D hyperboloid VT circuit structure. Catheter ablation may be simplified to targeting both sides around an identified LOB during sinus rhythm.

Massive Device-Related Thrombus After LAA Occlusion: Intraoperative Insights Into Mechanism.

In patients with a contraindication to oral anticoagulation, the left atrial appendage occlusion devices are an approved alternative. Device-related thrombus is a recognized complication, but underlying mechanisms are incompletely understood. In this case series, the authors describe potentially the same mechanism of thrombosis with intraoperative images of incomplete endothelialization. (Level of Difficulty: Intermediate.).

Strangulation: A Cause or Mimicker of Global Myocardial Hypoxia on ECG.

ST segment changes are often associated with myocardial ischemia but may be mimickers. We present a 21-year-old male who suffered a cardiac arrest following a suicide attempt by strangulation. Initial ECG revealed diffuse ST depressions and ST elevation in augmented vector right (aVR), concerning myocardial ischemia. However, repeat ECG revealed normal ST segments and an echocardiogram revealed no wall motion abnormalities. This case highlights the effects of systemic hypoxia on cardiac muscle and the need for a broad differential diagnosis when interpreting an ECG. This is invaluable when ST segment changes mimic acute myocardial infarction, but the clinical scenario suggests global hypoxia.

Exclusion of left atrial appendage: effects beyond thromboembolic prevention.

PURPOSE OF REVIEW: This review aims to summarize the nonthromboembolic prevention effects of left atrial appendage exclusion (LAAE). RECENT FINDINGS: Left atrial appendage (LAA) secretes multiple hormones; regulates blood volume and pressure; and generates trigger activities. Exclusion of the LAA by different techniques may lead to downstream effects including changes in blood pressure and cardiac performance, improvement of outcome of atrial fibrillation (AF) ablation, and alteration of metabolism. SUMMARY: LAAE procedures not only prevent thromboembolic events in patients with AF, but rather may bring additional benefits or side-effect to patients undergoing LAAE.

Cybersecurity threats to cardiac implantable devices: room for improvement.

PURPOSE OF REVIEW: For over a decade, vulnerabilities in the healthcare industry have been identified. Medical devices such as cardiovascular implantable electronic devices (CIEDs) are particularly concerning because of direct threats to patient safety and protected health information (PHI). Although these vulnerabilities have been identified and changes have been made, there is significant room for improvement. We identify changes and improvements to be made in the industry, by providers, and by patients. RECENT FINDINGS: Cybersecurity threats in cardiac implantable devices are legitimate concerns for patient safety and PHI. Changes to cybersecurity in these devices have been made, but are far from sufficient. SUMMARY: The number of CIEDs implanted worldwide are expected to increase over the next decade. As computer technology advances, cybersecurity threats will only continue to evolve and become more complex. The healthcare industry should seriously consider improvements to protect patients and providers.

Chronic Suppression of Ventricular Tachyarrhythmias in Patients with ICDs.

In this review, we examine the data evaluating the role of adjuvant therapy with antiarrthymic drugs (AADs) in chronic suppression of ventricular tachyarrhythmias in the patient with an ICD. It must be noted that all uses of AADs for this indication represent "off-label" prescription. No AAD is approved by the Food and Drug Administration (FDA) specifically as a therapy to reduce ICD shocks.

Mouse strain-specific differences in cardiac metabolic enzyme activities observed in a model of isoproterenol-induced cardiac hypertrophy.

1. Alterations in myocardial energy metabolism accompany pressure overload-induced hypertrophy. We previously described a novel model of catecholamine-induced hypertrophy in which A/J mice exhibit more robust cardiac hypertrophy than B6 mice. Accordingly, we assessed the influence of mouse strain on the activities of key myocardial metabolic enzymes and whether there are strain-related metabolic adaptations to short-term, high-dose isoproterenol (ISO) administration. 2. Thirty-nine male mice (19 A/J mice, 20 B6 mice), aged 12-15 weeks, were randomly assigned to receive either ISO (100 mg/kg, s.c.) or vehicle (sterile water) daily for 5 days. On Day 6, all hearts were excised, weighed, freeze clamped and assayed for pyruvate dehydrogenase (PDH), medium chain acyl-CoA dehydrogenase, carnitine palmitoyl transferase I and citrate synthase activities. Plasma fatty acids (FA) were also measured. 3. The ISO-treated A/J mice demonstrated greater percentage increases in gravimetric heart weight/bodyweight ratio than ISO-treated B6 mice (24 vs 3%, respectively; P < 0.001). All enzyme activities were significantly greater in vehicle-treated B6 mice than in A/J mice, illustrating a greater capacity for aerobic metabolism in B6 mice. Administration of ISO reduced PDHa (active form) activity in B6 mice by 47% (P < 0.001), with no significant change seen in A/J mice. Free FA levels were not significantly different between groups; thus, the differences in PDHa were not due to changes in FA. 4. The basal activity of myocardial metabolic enzymes is greater in B6 mice than in A/J mice and ISO alters myocardial PDH activity in a mouse strain-dependent manner. Compared with A/J mice, B6 mice demonstrate less ISO-induced cardiac hypertrophy, but greater activity of key enzymes regulating FA and carbohydrate oxidation, which may protect against the development of hypertrophy. The metabolic adaptations associated with ISO-induced hypertrophy differ from those reported with pressure overload hypertrophy.

Validation of echocardiographic methods for assessing left ventricular dysfunction in rats with myocardial infarction.

The rat infarct model is widely used in heart failure research, but few echocardiographic indexes of left ventricular (LV) function are validated in this model. Accordingly, the objective of this study was to validate a 13-segment LV wall motion score index (WMSI) and the myocardial performance index (MPI) in infarcted rats. Twenty-nine male Wistar rats underwent left coronary artery ligation or sham operation and were evaluated with two-dimensional and Doppler flow echocardiography 8 wk later. After echocardiography, invasive indexes were obtained using a high-fidelity catheter. WMSI and MPI were correlated with the invasive and noninvasive measurements of LV function. WMSI and MPI significantly correlated directly with end-diastolic pressure (r=0.72 and 0.42 for WMSI and MPI, respectively) and the time constant of isovolumic relaxation (r=0.68 and 0.48) and inversely with peak rate of rise of LV pressure (+dP/dt; r=-0.68 and -0.50), peak rate of decline in LV pressure (r=-0.57 and -0.44), LV developed pressure (r=-0.58 and -0.42), area fractional shortening (r=-0.85 and -0.53), and cardiac index (r=-0.74 and -0.74). Stepwise linear regression analyses revealed that LV end-diastolic pressure, +dP/dt, area fractional shortening, and cardiac index were independent determinants of WMSI (r=0.994) and that cardiac index and +dP/dt were independent determinants of MPI (r=0.781). We conclude that the 13-segment WMSI and MPI are reproducible and correlate strongly with established echocardiographic and invasive indexes of systolic and diastolic function. These findings support the use of WMSI and MPI as indexes of global LV function in the rat infarction model of heart failure.