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

BACKGROUND: 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. METHODS: 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. RESULTS: 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. CONCLUSION: Although the incidence of HB post AVNRT ablation is generally low, patients can be further stratified using three simple predictors.

Limitation of standard ECG criteria to localize an outflow tract PVC.

Multiple ECG algorithms exist to localize outflow tract PVCs. They can be invaluable in pre-procedure planning and patient counseling. We describe a case where the published algorithm for PVC localization did not predict the site of origin and successful ablation site. This case highlights the strengths and limitations of established ECG PVC localization algorithms.

Bradyarrhythmias in patients with COVID-19: Marker of poor prognosis?

BACKGROUND: Despite descriptions of various cardiovascular manifestations in patients with coronavirus disease 2019 (COVID-19), there is a paucity of reports of new onset bradyarrhythmias, and the clinical implications of these events are unknown. METHODS: Seven patients presented with or developed severe bradyarrhythmias requiring pacing support during the course of their COVID-19 illness over a 6-week period of peak COVID-19 incidence. A retrospective review of their presentations and clinical course was performed. RESULTS: Symptomatic high-degree heart block was present on initial presentation in three of seven patients (43%), and four patients developed sinus arrest or paroxysmal high-degree atrioventricular block. No patients in this series demonstrated left ventricular systolic dysfunction or acute cardiac injury, whereas all patients had elevated inflammatory markers. In some patients, bradyarrhythmias occurred prior to the onset of respiratory symptoms. Death from complications of COVID-19 infection occurred in 57% (4/7) patients during the initial hospitalization and in 71% (5/7) patients within 3 months of presentation. CONCLUSIONS: Despite management of bradycardia with temporary (3/7) or permanent leadless pacemakers (4/7), there was a high rate of short-term morbidity and death due to complications of COVID-19. The association between new-onset bradyarrhythmias and poor outcomes may influence management strategies for acutely ill patients with COVID-19.

The importance of bidirectional block during pulmonary vein isolation.

The definition of a successful ablation of atrial fibrillation can vary among electrophysiologists. A commonly described endpoint is bidirectional block of the four pulmonary veins. A case is described in which entrance block into a pulmonary vein was achieved early during pulmonary vein isolation. However, triggers from the pulmonary vein continued to conduct into the atrium, revealing the block was only unidirectional. Further ablation resulted in true electrical isolation and highlights the importance of achieving bidirectional block.

Pause dependent ventricular tachycardia resultant from carotid sinus massage.

In this report we describe a case of atrial flutter degenerating into ventricular fibrillation after carotid sinus pressure. Carotid sinus massage is an extremely valuable and widely used diagnostic and therapeutic modality. Although generally considered a rather benign maneuver, it is not without potential risk.

Occult paroxysmal atrial fibrillation in non-cryptogenic ischemic stroke.

OBJECTIVE: To determine the prevalence and risk factors for paroxysmal atrial fibrillation (PAF) diagnosis in non- cryptogenic ischemic stroke (CIS) patients. METHODS: In this pilot-prospective cohort study of non-CIS patients from September 2014 to September 2017, 53 patients were enrolled. 51/53 patients were implanted within 10 days of stroke onset with the Reveal LINQ insertable cardiac monitor and monitored until PAF detection or a minimum of 12 months. Inclusion required diagnosis of a non-AF stroke etiology, age ≥ 40, and either a virtual CHADS2 score ≥ 3 or ≥ 2 PAF-related comorbidities. RESULTS: Over a median monitoring period of 398 days, PAF was detected in 6/51 (11.8%) patients and anticoagulation was initiated in 5/6 (83.3%). Median time to PAF detection was 87 days (range 0-356 days). Median longest PAF episode was 96 min (range 1 to 1122 min), and 4/6 had multiple PAF recordings. Mean left atrial volume index was significantly higher in PAF patients (31.0 vs. 23.2 cc/m2; p = 0.04). CONCLUSION: Long-term monitoring of non-CIS patients detected PAF in a clinically relevant proportion of patients, resulting in stroke prevention therapy optimization. Further study to confirm these findings and refine the subset that would benefit from long-term cardiac monitoring is warranted.

Techniques for successful early retrieval of the Micra transcatheter pacing system: A worldwide experience.

BACKGROUND: Experience with retrieval of the Micra transcatheter pacing system (TPS) is limited because of its relatively newer technology. Although abandonment of the TPS at end of life is recommended, certain situations such as endovascular infection or device embolization warrant retrieval. OBJECTIVE: The purpose of this study was to report the worldwide experience with successful retrieval of the Micra TPS. METHODS: A list of all successful retrievals of the currently available leadless pacemakers (LPs) was obtained from the manufacturer of Micra TPS. Pertinent details of retrieval, such as indication, days postimplantation, equipment used, complications, and postretrieval management, were obtained from the database collected by the manufacturer. Other procedural details were obtained directly from the operators at each participating site. RESULTS: Data from the manufacturer consisted of 40 successful retrievals of the Micra TPS. Operators for 29 retrievals (73%) provided the consent and procedural details. Of the 29 retrievals, 11 patients underwent retrieval during the initial procedure (immediate retrieval); the other 18 patients underwent retrieval during a separate procedure (delayed retrieval). Median duration before delayed retrieval was 46 days (range 1-95 days). The most common reason for immediate retrieval was elevated pacing threshold after tether removal. The most common reasons for delayed retrieval included elevated pacing threshold at follow-up, endovascular infection, and need for transvenous device. Mean procedure duration was 63.11 ± 56 minutes. All retrievals involved snaring via a Micra TPS delivery catheter or steerable sheath. No serious complications occurred during the reported retrievals. CONCLUSION: Early retrieval of the Micra TPS is feasible and safe.

Pacemaker ventricular lead microdislodgement following a motor vehicle accident.

Pacemaker lead dislodgement can be defined as any lead position change, whether the functionality of the pacemaker is affected or not. Only dislodgements that provoke a malfunction in the pacing system, however, are clinically relevant. Lead dislodgement can be categorized as 'macro' or 'micro' dislodgement depending upon the presence of radiographic evidence. This case illustrates a case of lead microdislodgement after a low-impact motor vehicle accident. The lead tip was minimally displaced; enough to produce an increase in capture threshold and eventually loss of capture while keeping near normal lead impedance values. Review of the literature shows that ventricular lead dislodgement after a motor vehicle accident is a rare incidence and cause of pacemaker malfunction.

Histologic Sequelae of Apical Hypertrophic Cardiomyopathy: Dystrophic Calcification.

We present cardiac computed tomography (CT) findings demonstrating apical hypertrophic cardiomyopathy with dystrophic calcification of the left ventricular apex. The absence of significant epicardial coronary artery disease demonstrated by coronary CT angiography suggests that increased wall tension and decreased microvascular perfusion over time account for the dyskinetic apical myocardium, rather than myocardial infarction secondary to atherosclerotic plaque rupture. These observations support CT as the imaging modality of choice to visualize the deposition of calcium in injured myocardial tissue, a recognized occurrence in chronically infarcted myocardium.

Should the initiation of antiarrhythmic therapy for atrial fibrillation occur in the hospital or out of the hospital?: a review of the literature.

BACKGROUND: Initiation of antiarrhythmic therapy for atrial fibrillation is a key step in the treatment of this disorder. Much controversy remains as to the risks and benefits of initiating therapy as an inpatient versus an outpatient. OBJECTIVE: To explore the various issues of debate and to determine the importance and validity of these various issues when it comes to the evaluation of patients for in- versus out-of-hospital initiation of antiarrhythmic therapy for atrial fibrillation. METHODS: A MEDLINE search of English language journal articles since 1966 and a hand search of bibliographies included in pertinent retrieved articles was undertaken. Articles used included review articles, retrospective studies, and meta-analyses. RESULTS: The literature is full of articles for and against outpatient initiation of antiarrhythmic therapy. One side feels that the risks of antiarrhythmic therapy initiation are serious enough in all patients and easy enough to reverse or ameliorate if the patient is in the safety of the monitored hospital setting. The other side argues that these complications are infrequent enough except in certain commonly identifiable patients, that not all need hospitalization during antiarrhythmic initiation. The issues at the heart of the dispute include: the presence or absence of underlying heart disease; the period of monitoring after initiation of therapy; the choice of antiarrhythmic agent used; and even the seriousness and prevalence of the arrhythmia which can be induced. CONCLUSIONS: The issue of in versus out-of-hospital initiation of antiarrhythmic therapy for atrial fibrillation remains a widely disputed topic. Many factors come under consideration when this topic is studied. At present, we recommend that patients with significant structural heart disease, conduction disease, and/or QT prolongation be strongly considered for in-hospital initiation of antiarrhythmic medications. Further prospective studies are necessary to assess the magnitude of the difference of initiating antiarrhythmic therapy as an inpatient versus as an outpatient.

Planning and guidance of cardiac resynchronization therapy-lead implantation by evaluating coronary venous anatomy assessed with multidetector computed tomography.

OBJECTIVES: We sought to evaluate the utility of multidetector computed tomography (MDCT) in preoperative planning of cardiac resynchronization therapy (CRT) device implantation. BACKGROUND: Variation in coronary venous anatomy can affect optimal lead placement and may warrant preimplantation visualization prior to CRT lead placement. METHODS: Prospective randomized enrollment of 29 patients (17 males; mean age at implant 66.7 ± 12.8 years) was undertaken. Patients were randomized to preimplantation MDCT (GE(®) 64-detector Lightspeed, n = 16) or no MDCT. Implantation was planned based on three-dimensional coronary venous reconstruction as visualized in the CT group. Measurement of coronary sinus (CS) angulation, CS ostial (os) diameter, right atrial (RA) width, volume, and height was undertaken prior to implant. Intraoperative CS lead implantation times (introduction, cannulation, and left ventricular [LV] lead positioning), procedure time, fluoroscopy time, and venogram contrast volume were measured to determine if there was a difference between patients who underwent preimplant CT scan and those who did not. RESULTS: CS os diameter (mean = 13.8 ± 2.9 cm) was inversely correlated with total fluoroscopy time (r = -0.57, P = .008), and total procedure time, but this correlation was not statistically significant (r = -0.36, P = 0.12). RA width (mean = 52.8 ± 9.9 cm) was associated with a shorter total procedure time (r = -0.44, P = .047) and LV lead positioning time (r = -0.33, P = .012). There were no statistically significant differences between the CT group and the non-CT group with respect to total intraoperative and fluoroscopy times or venogram contrast volumes. Total procedure time was longer in the CT group but the difference was not statistically significant (94 ± 27.2 vs. 74.7 ± 26.6; P = .065). CONCLUSION: Noninvasive visualization of the coronary venous anatomy before CRT implantation can be used as a guide for lead placement. While no significant differences were noted between the two groups with respect to intraoperative variables, CS os diameter and RA width inversely correlated to a shorter procedure time and LV lead positioning time, respectively. Further clinical trials regarding the utility of MDCT to visualize coronary venous anatomy prior to CRT implantation for procedural planning and lead placement guidance are warranted.

Echocardiographic predictors of ventricular tachycardia.

BACKGROUND: Patients with structural heart disease are prone to ventricular tachycardia (VT) and ventricular fibrillation (VF), which account for the majority of sudden cardiac deaths (SCDs). We sought to examine echocardiographic parameters that can predict VT as documented by implantable cardioverter-defibrillator (ICD) appropriate discharge. We examine echocardiographic parameters other than ejection fraction that may predict VT as recorded via rates of ICD discharge. METHODS: Analysis of 586 patients (469 males; mean age = 68 ± 3 years; mean follow-up time of 11 ± 14 months) was undertaken. Echo parameters assessed included left ventricular (LV) internal end diastolic/systolic dimension (LVIDd, LVIDs), relative wall thickness (RWT), and left atrial (LA) size. RESULTS: The incidence of VT was 0.22 (114 VT episodes per 528 person-years of follow-up time). Median time-to-first VT was 3.8 years. VT was documented in 79 patients (59 first VT incidence, 20 multiple). The echocardiographic parameter associated with first VT was LVIDs >4 cm (P = 0.02). CONCLUSION: The main echocardiographic predictor associated with the first occurrence of VT was LVIDs >4 cm. Patients with an LVIDs >4 cm were 2.5 times more likely to have an episode of VT. Changes in these echocardiographic parameters may warrant aggressive pharmacologic therapy and implantation of an ICD.

Predictors of Recurrent Atrial Fibrillation Using Mode Switch Quantification.

BACKGROUND: The efficacy of mode switching to predict atrial fibrillation has been established in the literature. There have been few studies investigating the incidence and clinical implication of mode switch episodes quantified from implantable cardioverter defibrillator and pacemaker interrogation. We sought to investigate the incidence of mode switch recurrence in patients with implantable cardioverter defibrillators and permanent pacemakers. METHODS: Mode switch was defined as any occurrence documented during device interrogation after the date of implantation. Clinical predictors (age, gender, hypertension, diabetes, syncope, atrial fibrillation (AF)), and medications were analyzed to determine association with single and recurrent mode switch occurrences. RESULTS: There were 21 patients experiencing a mode switch event, identified from a group of 54 patients (42 males; mean age 70 ± 12 years; mean follow-up 29.1 ± 22 months (3.4 - 81.4 months)). All but two patients were receiving medical therapy including beta blockers, statins, ace-inhibitors, and anti-arrhythmics. There were 21 subjects who experienced at least one mode switch during their follow-up and 33 subjects who never experienced a mode switch during their follow-up time. The median time to first mode switch from device implantation was 39.3 months. Risk factors individually associated with any mode switch episode included: diabetes (DM) (P < 0.04) and use of digitalis (P = 0.02). Subjects who had a history of DM were 5 times more likely to have at least one mode switch occurrence. There was a significantly higher rate of mode switch among patients who were diabetic than patients who were not (3.7 per follow-up month ± 5.3 vs. 0.98 per follow-up month ± 2.02; P = 0.02). There was a significantly higher rate of mode switch among patients who were on digitalis than those who were not (3.1 per follow-up month ± 4.3 vs. 0.73 per follow-up month ± 1.9; P = 0.02). CONCLUSION: The main factors associated with any mode switch are having a history of diabetes and digitalis use. Those patients who are diabetics and those on digitalis may warrant closer observation and management for the development of atrial fibrillation.

Electrophysiologic study: its predictive value for ventricular arrhythmias.

Studies have shown the predictive value of inducible ventricular tachycardia and clinical arrhythmia in patients who have structural heart disease. We examined the possible predictive value of electrophysiologic study before the placement of an implantable cardioverter-defibrillator. Our retrospective study group comprised 315 patients who had ventricular tachycardia that was inducible during electrophysiologic study and who had undergone at least 1 month of follow-up (247 men; mean age, 66.9 +/- 13.5 yr; mean follow-up, 24.9 +/- 14.8 mo). Recorded characteristics included induced ventricular tachycardia cycle length, atrio-His and His-ventricular electrograms, PR and QT intervals, QRS duration, and drug therapy. Of the 315 patients, 97 experienced ventricular arrhythmia during the follow-up period, as registered by 184 of more than 400 interrogations. There were 187 episodes of ventricular arrhythmia (tachycardia, 178; fibrillation, 9) during 652.5 person-years of follow-up. Subjects with a cycle length > or =240 msec were more likely to have an earlier 1st arrhythmia than those with a cycle length <240 msec (P=0.032). A quarter of the subjects with a cycle length > or =240 msec had their 1st arrhythmia by 19.14 months, compared with 23.8 months for a quarter of the subjects with a cycle length <240 msec (P <0.032). Among the electrophysiologic characteristics examined, inducible ventricular tachycardia with a cycle length > or =240 msec is predictive of appropriate implantable cardioverter-defibrillator therapy at an earlier time. This may have prognostic implications that warrant implantable cardioverter-defibrillator programming to enable appropriate antitachycardia pacing in this group of patients.

Dual atrioventricular-nodal physiology, elicited by pacing and leading to a reversible cardiomyopathy.

Atrioventricular nodal re-entry tachycardia is the most common form of regular paroxysmal tachycardia in the adult population. This tachycardia is a re-entrant rhythm that uses the anatomic location of the atrioventricular node and its surrounding perinodal atrial tissue. The simplest concept regarding the atrioventricular nodal physiology that allows re-entry is founded upon the postulated existence of 2 atrioventricular nodal pathways with different conduction velocities and refractory periods. Herein, we present the case of a 64-year-old man who had a history of paroxysmal atrial fibrillation; he had a permanent pacemaker for sick-sinus syndrome. He developed a tachycardia-induced cardiomyopathy with a perpetual dual response to the pacemaker stimulus. The tachycardia displayed characteristic dual atrioventricular-nodal physiology that was suppressed by amiodarone therapy, leading to a reversal of the cardiomyopathy. We discuss the mechanisms that surround such phenomena.