Wide Complex Tachycardia in a Right-Sided Heart: Diagnostic and Therapeutic Challenges.

Dextroposition is a rare cardiac malformation defined as heart shift to right of midline. ECG findings vary with degree of displacement within the chest cavity. We report the second known case of dextroposition with accessory pathway (posteroseptal in our patient), presenting as pre-excited atrial tachycardia. Abnormal anatomy complicates pathway localization/ablation. (Level of Difficulty: Intermediate.).

Low left atrial appendage emptying velocity is a predictor of atrial fibrillation recurrence after catheter ablation.

BACKGROUND: Recurrence of atrial fibrillation (AF) after catheter ablation (CA) remains common and studies have shown about 5%-9% annual recurrence rate after CA. We sought to assess the echocardiogram derived left atrial appendage (LAA) emptying velocity as a predictor of AF recurrence after CA. OBJECTIVE: To determine if LAA emptying is a marker of recurrence of AF post-CA METHODS: A total of 303 consecutive patients who underwent CA for AF between 2014 and 2020 were included. Baseline clinical characteristics and echocardiographic data of the patients were obtained by chart review. LAA emptying velocities were obtained from transesophageal echocardiogram (TEE). LA voltage was obtained during the mapping for CA. Chi-square test and nominal logistic regression were used for statistical analysis. An receiver operator characteristic curve was used to determine LAA velocity cut-off. RESULTS: Mean patient age was 61.7 ± 10.5; 32% were female. Mean LAA emptying velocity was 47.5 ± 20.2. A total of 103 (40%) patients had recurrence after CA. In the multivariable model, after adjusting for potential confounders, LAA emptying velocity of ≥52.3 was associated with decreased AF recurrence postablation (odds ratio [OR]: 0.55; 95% confidence interval  [CI]: 0.31-0.97; p = .03*). There were 190 (73%) patients in normal sinus rhythm during TEE and CA, and sensitivity analysis of these patients showed that LAA velocity ≥52.3 remained associated with decreased AF recurrence (OR: 0.35; 95% CI: 0.15-0.82; p = .01*). CONCLUSION: LAA emptying velocity measured during preprocedural TEE can serve as a predictor of AF recurrence in patients undergoing CA.

Swallow Syncope Associated With Intermittent Sinus Pause and High-Degree Atrioventricular Block: A Case Report.

Swallow syncope, also known as deglutition syncope, is a relatively rare neurogenic disorder that is triggered by oral intake. When diagnosed, swallow syncope is treatable, but it is challenging to identify without proper history and prior knowledge of this disorder. Here, we describe the case of a 68-year-old female with a complex history who presented to the emergency room with complaints of worsening long-term intermittent lightheadedness and dizziness associated with swallowing. During her hospital stay, the patient was noted to have a high-degree atrioventricular block on telemetry during dinner time. A repeat electrocardiogram (ECG) demonstrated a prolonged P-R interval, and a temporal relationship between swallowing cold water and electrocardiogram (ECG) changes was demonstrated. A diagnosis of swallow syncope was confirmed. Electrophysiology was consulted and a pacemaker was placed. Symptoms of swallow-associated arrhythmias completely resolved after pacemaker implantation. This case illustrates the challenging problem of swallow syncope. While swallow syncope is highly treatable once identified, the challenge lies in identifying the disorder.

Correlation of scar in cardiac MRI and high-resolution contact mapping of left ventricle in a chronic infarct model.

BACKGROUND: Endocardial mapping for scars and abnormal electrograms forms the most essential component of ventricular tachycardia ablation. The utility of ultra-high resolution mapping of ventricular scar was assessed using a multielectrode contact mapping system in a chronic canine infarct model. METHODS: Chronic infarcts were created in five anesthetized dogs by ligating the left anterior descending coronary artery. Late gadolinium-enhanced magnetic resonance imaging (LGE MRI) was obtained 4.9 ± 0.9 months after infarction, with three-dimensional (3D) gadolinium enhancement signal intensity maps at 1-mm and 5-mm depths from the endocardium. Ultra-high resolution electroanatomical maps were created using a novel mapping system (Rhythmia Mapping System, Rhythmia Medical/Boston Scientific, Marlborough, MA, USA) Rhythmia Medical, Boston Scientific, Marlborough, MA, USA with an 8.5F catheter with mini-basket electrode array (64 tiny electrodes, 2.5-mm spacing, center-to-center). RESULTS: The maps contained 7,754 ± 1,960 electrograms per animal with a mean resolution of 2.8 ± 0.6 mm. Low bipolar voltage (<2 mV) correlated closely with scar on the LGE MRI and the 3D signal intensity map (1-mm depth). The scar areas between the MRI signal intensity map and electroanatomic map matched at 87.7% of sites. Bipolar and unipolar voltages, compared in 592 electrograms from four MRI-defined scar types (endocardial scar, epicardial scar, mottled transmural scar, and dense transmural scar) as well as normal tissue, were significantly different. A unipolar voltage of <13 mV correlated with transmural extension of scar in MRI. Electrograms exhibiting isolated late potentials (ILPs) were manually annotated and ILP maps were created showing ILP location and timing. ILPs were identified in 203 ± 159 electrograms per dog (within low-voltage areas) and ILP maps showed gradation in timing of ILPs at different locations in the scar. CONCLUSIONS: Ultra-high resolution contact electroanatomical mapping accurately localizes ventricular scar and abnormal myocardial tissue in this chronic canine infarct model. The high fidelity electrograms provided clear identification of the very low amplitude ILPs within the scar tissue and has the potential to quickly identify targets for ablation.

Iron deposition following chronic myocardial infarction as a substrate for cardiac electrical anomalies: initial findings in a canine model.

PURPOSE: Iron deposition has been shown to occur following myocardial infarction (MI). We investigated whether such focal iron deposition within chronic MI lead to electrical anomalies. METHODS: Two groups of dogs (ex-vivo (n = 12) and in-vivo (n = 10)) were studied at 16 weeks post MI. Hearts of animals from ex-vivo group were explanted and sectioned into infarcted and non-infarcted segments. Impedance spectroscopy was used to derive electrical permittivity ([Formula: see text]) and conductivity ([Formula: see text]). Mass spectrometry was used to classify and characterize tissue sections with (IRON+) and without (IRON-) iron. Animals from in-vivo group underwent cardiac magnetic resonance imaging (CMR) for estimation of scar volume (late-gadolinium enhancement, LGE) and iron deposition (T2*) relative to left-ventricular volume. 24-hour electrocardiogram recordings were obtained and used to examine Heart Rate (HR), QT interval (QT), QT corrected for HR (QTc) and QTc dispersion (QTcd). In a fraction of these animals (n = 5), ultra-high resolution electroanatomical mapping (EAM) was performed, co-registered with LGE and T2* CMR and were used to characterize the spatial locations of isolated late potentials (ILPs). RESULTS: Compared to IRON- sections, IRON+ sections had higher[Formula: see text], but no difference in[Formula: see text]. A linear relationship was found between iron content and [Formula: see text] (p<0.001), but not [Formula: see text] (p = 0.34). Among two groups of animals (Iron (<1.5%) and Iron (>1.5%)) with similar scar volumes (7.28% ± 1.02% (Iron (<1.5%)) vs 8.35% ± 2.98% (Iron (>1.5%)), p = 0.51) but markedly different iron volumes (1.12% ± 0.64% (Iron (<1.5%)) vs 2.47% ± 0.64% (Iron (>1.5%)), p = 0.02), QT and QTc were elevated and QTcd was decreased in the group with the higher iron volume during the day, night and 24-hour period (p<0.05). EAMs co-registered with CMR images showed a greater tendency for ILPs to emerge from scar regions with iron versus without iron. CONCLUSION: The electrical behavior of infarcted hearts with iron appears to be different from those without iron. Iron within infarcted zones may evolve as an arrhythmogenic substrate in the post MI period.

Prevention of esophageal thermal injury during radiofrequency ablation for atrial fibrillation.

Pulmonary vein isolation using radiofrequency ablation is an effective therapy in patients with atrial fibrillation. However, the esophagus descends in close proximity to the posterior wall of the left atrium and renders this structure susceptible to thermal injury. Esophageal ulceration has been hypothesized to be a precursor to left atrial-esophageal fistula, a procedural complication associated with poor prognosis. In this review, we have analyzed and summarized the published data regarding esophageal thermal injury during catheter ablation for atrial fibrillation and strategies to minimize risk of this complication. While esophageal temperature monitoring can be useful, multiple factors such as patient characteristics and specific strategies for radiofrequency energy delivery also merit consideration.

Approach to the difficult septal atrioventricular accessory pathway: the importance of regional anatomy.

Ablation of accessory tracts in the posteroseptal region can be challenging, as illustrated by these 2 cases. Familiarity of the anatomy of this region and recognition of the ECG patterns can help identify the AP origin and potentially improve success rates of ablation. The isoelectric initial preexcited QRS complex with rSR' pattern in lead V1 of the surface ECG but not the relatively earlier local ventricular activation at PSMA region may indicate a left-sided ablation approach for these APs.

Electrophysiological characteristics of focal atrial tachycardia surrounding the aortic coronary cusps.

BACKGROUND: Catheter ablation of atrial tachycardia (AT) arising near the coronary cusps has been reported in limited numbers of patients. We investigated the electrophysiological characteristics of these ATs in 22 consecutive patients. METHODS AND RESULTS: This study included 22 patients (mean age ± SD, 53 ± 11 years; 86% female) with ATs arising near the aortic coronary cusps who underwent successful ablation. Activation mapping was performed during tachycardia to identify the earliest activation site. All patients achieved successful ablation through either a retrograde aortic (n=19) or a transseptal (n=3) approach. The successful ablation sites were located in the noncoronary cusp (NCC) (n=16), including 3 near the junction between the NCC and right coronary cusp. The remaining 6 cases were ablated from the left coronary cusp (LCC) (n=3) or the left atrium posterior to the LCC (n=3). For most tachycardias, there were distinctive P-wave morphological features recorded for each cusp location. Furthermore, analysis of the electrogram morphological features recorded during tachycardia at successful ablation sites revealed an atrial/ventricular (A/V) ratio >1 in 14 of 16 NCC ATs; the remaining 2, from the NCC near the junction with the right coronary cusp, showed an A/V ratio ≤ 1. At ablation sites in the LCC, the A/V ratio was <1 (4 of 6 patients) or 1 (remaining 2 patients). During a follow-up duration of 30 ± 13 months, all patients were free of arrhythmias without antiarrhythmic drugs. CONCLUSIONS: ATs surrounding the aortic coronary cusps can be safely and effectively ablated, with good long-term outcomes. In addition to the P-wave morphological features, the A/V ratio of the local electrogram recording during tachycardia facilitated the localization of successful sites.

Spontaneously alternating forms of the atrioventricular node reentrant tachycardia.

We present a case of atrioventricular node reentrant tachycardia that displays spontaneously alternating antegrade and retrograde conduction via 1:2 manners.

Inducibility of atrial fibrillation in the absence of atrial fibrillation: what does it mean to be normal?

BACKGROUND: While inducibility of atrial fibrillation (AF) is often used as an endpoint for radiofrequency ablation of AF, little is known regarding inducibility among normals. We therefore evaluated the inducibility of AF with rapid atrial pacing in patients without a clinical history of AF after catheter ablation of supraventricular tachycardia (SVT). METHODS: We prospectively evaluated 86 patients with no history of AF who were referred for catheter ablation of SVT. After successful ablation, two different rapid atrial pacing protocols for induction of AF were tested. First, AF induction was attempted by 5-second bursts of atrial pacing from the coronary sinus ostium (CSO) at three different cycle lengths (CLs). Next, decremental pacing was performed from the CSO starting at a CL of 250 ms to the loss of 1:1 atrial capture. This protocol was repeated 3 times for each subject. RESULTS: Three of the subjects (3.5%) enrolled had inducible AF with the first pacing protocol. However, with the second protocol, AF was inducible in 22 patients (25.6%), including sustained AF in 16 patients (18.6%). There were significant differences in the inducibility of AF between the two atrial pacing protocols. Additionally, with the second pacing protocol, patients with a loss of 1:1 atrial capture at CL <180 ms were more easily inducible for AF (21/63 vs. 1/23; P = .006). CONCLUSION: Using a specific, decremental pacing protocol, 26% of patients without a history of AF had inducible AF. These findings suggest that significant further investigation is needed to optimize the specificity of using AF induction as an endpoint for AF ablation.

Natural antibodies and complement modulate intimal thickening after arterial injury.

Immune factors are involved in modulating neointimal response to arterial wall injury, but the role of individual immune effectors in this response remains unclear. Using a carotid cuff injury model in mice, we tested the role of immunoglobulin isotypes in modulating intimal thickening by using adoptive transfer of splenocytes from WT mice, or the direct administration of IgG or IgM into immune-deficient Rag-1-/- [Rag-1 knockout (Rag-1KO)] mice. The direct role of complement was also tested by depletion of complement. Splenocytes from WT mice were isolated and adoptively transferred to Rag-1KO mice subjected to carotid cuff arterial injury. Transfer of splenocytes to Rag-1KO mice resulted in increased serum IgM and IgG within 48 h and were comparable to WT levels by 21 days after injury. Splenocyte transfer in Rag-1KO decreased intimal area by 40% compared with Rag-1KO mice without cell transfer. To further differentiate the relative contribution of IgM or IgG in reducing intimal thickening, additional groups of Rag-1KO mice were subjected to injury and given intravenous injections of pooled mouse IgG or IgM. Both IgG and IgM treatment significantly reduced intimal thickening compared with untreated Rag-1KO mice. Immunoglobulin treatments modified serum complement C3 profile and decreased C3 presence in injured arteries. Depletion of C3 using cobra venom factor in Rag-1KO mice significantly decreased intimal thickening. Our results identify the direct role of natural IgG and IgM, and complement in the modulation of neointimal response to arterial injury.

Comparison of drug-eluting stents with bare metal stents in unselected patients with acute myocardial infarction.

OBJECTIVES: The aim of this study was to compare the procedural characteristics and outcomes of patients with acute myocardial infarction treated with drug-eluting stents (DES) vs. bare metal stents (BMS). BACKGROUND: DES have been shown to reduce the incidence of restenosis and target vessel revascularization (TVR) in clinical randomized studies when compared with BMS in patients undergoing elective percutaneous intervention. Limited data are available with the use of DES in patients with acute ST-segment elevation myocardial infarction. METHODS: Two hundred and sixty-one consecutive patients who presented with myocardial infarction between 7/2001 and 8/2005 were studied. The procedural characteristics, 30-day and 12-month outcomes of 131 patients treated with DES were compared with 130 patients treated with BMS. RESULTS: At 12-months follow-up DES therapy was associated with a substantial decrease in major adverse cardiovascular events (MACE) (HR 0.33; P =0.002), TVR (HR 0.19; P =0.002), and recurrent myocardial infarction (HR 0.23; P =0.051) vs. BMS therapy. Coronary interventions utilizing DES were characterized by a marked increase in the number of stent per target vessel (DES: 1.9 +/- 0.9 vs. BMS: 1.38 +/- 0.6, P < 0.0001), treatment of bifurcation (DES: 21% vs. BMS: 5%, P =0.0004), and multivessel intervention (DES: 22% vs. BMS: 8%, P =0.003). CONCLUSION: The routine use of DES in acute myocardial infarction is associated with reduced rates of MACE at 12 months vs BMS, despite a higher rate of complex procedures in the DES treated patients. In addition to its anti-restenosis effect, the improved outcome of patients treated with DES may be linked to a more complete revascularization in association with prolonged clopidogrel therapy.