Recovery of Transient High-Grade Atrioventricular Block Managed With Corticosteroid Therapy Without Device Implantation in Newly Diagnosed Cardiac Sarcoidosis: A Case Report

Atrioventricular blocks (AVBs) presenting in cardiac sarcoidosis (CS) remain an ongoing challenge for clinicians. While most initiate immunosuppressive therapy with the goal of pursuing device implantation, there is some ambiguity as to which patient cohorts actually benefit from device therapy. We present a case of a 39-year-old African American male with a past medical history of hypertension and no prior cardiac history who presented with substernal chest pain in the setting of a hypertensive emergency. He was later diagnosed with cardiac sarcoidosis by cardiac magnetic resonance imaging. His hospital course was complicated by transient Mobitz II atrioventricular block. He was started on prednisone, and while initially scheduled for an implantable cardioverter-defibrillator (ICD), his conduction block recovered. Through a multidisciplinary approach, the patient was discharged on medical management with outpatient follow-up. Since his initial hospitalization, the patient has not had any concerning cardiovascular events over the past year and has not been treated with device therapy. Our case illustrates the feasibility of effectively managing patients with cardiac sarcoidosis presenting with transient atrioventricular blocks only with corticosteroid therapy without needing device implantation.

High-Risk Apical Hypertrophic Cardiomyopathy Requiring an Implantable Cardioverter-Defibrillator: A Case Report of an Overlooked Etiology

Apical hypertrophic cardiomyopathy is a rare variant of hypertrophic cardiomyopathy characterized by abnormal heart muscle thickening, specifically affecting the left ventricle's apex. Classically revealing both giant T-wave inversions in the precordial leads of an electrocardiogram and a spade-like configuration of the left ventricular cavity on ventriculograms, the diagnosis of the apical variant has evolved with cardiac magnetic resonance imaging. Despite being well known among East Asian populations, the diagnosis of apical hypertrophic cardiomyopathy is often underestimated and overlooked among American patients due to the non-specific nature of echocardiography. In this case report, we present the diagnosis of apical hypertrophic cardiomyopathy in a middle-aged African American male with chronic palpitations. The diagnosis was confirmed using cardiac magnetic resonance imaging, which revealed extensive myocardial fibrosis. Ultimately, the patient was treated with an implantable cardioverter-defibrillator. Our case aims to enhance the understanding and facilitate the recognition and management of apical hypertrophic cardiomyopathy, particularly among non-Asian individuals. Current challenges revolve around robust risk stratification strategies for patients at high risk for sudden cardiac death that require device therapy.

A worldwide survey on incidence, management and prognosis of oesophageal fistula formation following atrial fibrillation catheter ablation: The POTTER-AF study

AIMS

Oesophageal fistula represents a rare but dreadful complication of atrial fibrillation catheter ablation. Data on its incidence, management and outcome are sparse.

METHODS AND RESULTS

This international multicenter registry investigates the characteristics of oesophageal fistulae after treatment of atrial fibrillation by catheter ablation. A total of 553,729 catheter ablation procedures (radiofrequency: 62.9%, cryoballoon: 36.2%, other modalities: 0.9%) were performed at 214 centers in 35 countries. In 78 centers 138 patients (0.025%, radiofrequency: 0.038%, cryoballoon: 0.0015% (p<0.0001)) were diagnosed with an oesophageal fistula. Periprocedural data were available for 118 patients (85.5%). Following catheter ablation, the median time to symptoms and the median time to diagnosis were 18 (7.75, 25; range: 0-60) days and 21 (15, 29.5; range: 2-63) days, respectively. The median time from symptom onset to oesophageal fistula diagnosis was 3 (1, 9; range: 0-42) days. The most common initial symptom was fever (59.3%). The diagnosis was established by chest computed tomography in 80.2% of patients. Oesophageal surgery was performed in 47.4% and direct endoscopic treatment in 19.8%, and conservative treatment in 32.8% of patients. The overall mortality was 65.8%. Mortality following surgical (51.9%) or endoscopic treatment (56.5%) was significantly lower as compared to conservative management (89.5%) (odds ratio 7.463 (2.414, 23.072) p<0.001).

CONCLUSIONS

Oesophageal fistula after catheter ablation of atrial fibrillation is rare and occurs mostly with the use of radiofrequency energy rather than cryoenergy. Mortality without surgical or endoscopic intervention is exceedingly high.

A Case of Sick Sinus Syndrome With Prolonged Asystole Masquerading as a Transient Ischemic Attack

Sick sinus syndrome (SSS) is a term used to describe dysfunction of the sinoatrial (SA) node that can lead to various cardiac arrhythmias that predominately manifest in the elderly. Commonly implicated arrhythmias vary from inappropriate bradycardia, tachycardia, sinus pauses, and rarely sinus arrest. Despite being a common reason for permanent pacemaker implantation, little is known regarding the incidence of SSS and there is even less reporting on SSS complicated by prolonged asystole. We present a case highlighting an infrequently observed manifestation of SSS with recurrent, prolonged ventricular asystolic episodes that were causing previously unexplained episodes of confusion and agonal breathing. Our patient was a 75-year-old male with a past medical history of hypertension, dyslipidemia, and prior transient ischemic attacks (TIAs) that presented after an acute mental status change. The initial leading differential diagnosis was believed to be a TIA and he was admitted to neurology service for further evaluation. The patient had recurring episodes of confusion associated with agonal breathing that upon closer review of the cardiac telemetry revealed sinus bradycardia to the 40s interrupted by several prolonged episodes of asystole, the longest lasting 20 seconds. Due to his symptoms and to avoid potential deterioration resulting in hemodynamic instability, the electrophysiology service urgently placed a temporary transvenous pacemaker and then later implanted a leadless pacemaker. On outpatient follow-up, he no longer had episodes of confusion, and no further asystolic episodes were noted on his device check.

COVID-19-associated Brugada pattern electrocardiogram: Systematic review of case reports

AIMS

To summarize published case reports of patients diagnosed with coronavirus disease 2019 (COVID-19) and Brugada pattern electrocardiogram (ECG).

METHODS

The Preferred Reporting Items for Systematic Reviews and Meta-Analyses checklist were followed. A literature search was conducted using PubMed, EMBASE, and Scopus up until September 2021. The incidence, clinical characteristics, and management outcomes of COVID-19 patients with a Brugada pattern ECG were identified.

RESULTS

A total of 18 cases were collected. The mean age was 47.1 years and 11.1% were women. No patients had prior confirmed diagnosis of Brugada syndrome. The most common presenting clinical symptoms were fever (83.3%), chest pain (38.8%), shortness of breath (38.8%), and syncope (16.6%). All 18 patients presented with type 1 Brugada pattern ECG. Four patients (22.2%) underwent left heart catheterization, and none demonstrated the presence of obstructive coronary disease. The most common reported therapies included antipyretics (55.5%), hydroxychloroquine (27.7%), and antibiotics (16.6%). One patient (5.5%) died during hospitalization. Three patients (16.6%) who presented with syncope received either an implantable cardioverter defibrillator or wearable cardioverter defibrillator at discharge. At follow-up, 13 patients (72.2%) had resolution of type 1 Brugada pattern ECG.

CONCLUSION

COVID-19-associated Brugada pattern ECG seems relatively rare. Most patients had resolution of the ECG pattern once their symptoms have improved. Increased awareness and timely use of antipyretics is warranted in this population.

Physician antibiotic hydration preferences for biologic antibacterial envelopes during cardiac implantable device procedures

Background

Cardiac implantable electronic device (CIED) infection is a potentially serious complication of CIED procedures. Infection risk mitigation includes using guideline-recommended pre-operative intravenous antibacterial prophylaxis (IV ABX). The use of antibiotic-eluting CIED envelopes has also been shown to reduce infection risk. The relationship between and potential benefits associated with guideline-recommended IV ABX in combination with antibacterial envelopes have not been characterized.

Methods

Biologic envelopes made from non-crosslinked extracellular matrix (ECM) were implanted into 1,102 patients receiving CIEDs. The implanting physician decided patient selection for using a biologic envelope and envelope hydration solution. Observational data was analyzed on IV ABX utilization rates, antibacterial envelope usage, and infection outcomes.

Results

Overall compliance with IV ABX was 96.6%, and most patients received a biologic envelope hydrated in antibiotics (77.1%). After a mean follow-up of 223 days, infection rates were higher for sites using IV ABX <80% of the time vs. sites using ≥80% (5.6% vs. 0.8%, p = 0.008). Physicians demonstrated preference for hydration solutions containing gentamicin in higher-risk patients, which was found by multivariate analysis to be associated with a threefold reduction in infection risk (OR 3.0, 95% CI, 1.0-10.0).

Conclusion

These findings suggest that use of antibiotics, particularly gentamicin, in biologic envelope hydration solution may reduce infection risk, and use of antibacterial envelopes without adjunct IV ABX may not be sufficient to reduce CIED infections.

Clinical trial registration

[https://clinicaltrials.gov/], identifier [NCT02530970].

A new window on subcutaneous ICD system performance: Z-lead impedance change over time in devices with and without extracellular matrix envelope use

Background

Device impedance for subcutaneous ICDs (S-ICDs) may rise over time reflecting changes in tissue electrical conduction due to fibrosis from the natural foreign body response, increasing the risk of defibrillation failure. A biologic envelope optimized for S-ICDs may mitigate fibrosis and encourages angiogenesis around the device possibly decreasing impedance rise over time. The S-ICD system performs routine low-voltage Z-lead (LVZ) impedance testing (impedance between shocking coil and can) that may provide insight into the impedance changes on device functionality and efficacy over time.

Purpose

Explore early and late impedance changes over time in S-ICDs implanted with and without envelopes using periodic LVZ measurements.

Methods

30 patients received S-ICDs (15 with envelope) between 1/2017 and 3/2021, after excluding those with device complications, uncontrolled comorbidities, or recent cardiac surgery. Impedance data was recorded at initial implantation. LVZ impedance data was extracted from the wireless remote monitoring system, trended over 0–4 years post implant, and analyzed blinded to patient information.

Results

24 patients (12 envelope) had evaluable implant and chronic data sets. Baseline clinical characteristics were similar between groups. Impedance in general was higher in the envelope group at initial implantation (LVZ mean 89 Ω vs 74 Ω) and throughout the first year. Comparing envelope to no envelope, the initial average shock impedance was 87.3±30.50 vs 66.7±10.40, followed by an average low-V impedance drop of 29 Ω vs 17 Ω during the first month, with a recovery to 109 Ω vs 91 Ω at 30 months post implant. After 30 months, impedance trends demonstrated a modest linear increase up to 48 months in the no envelope group in comparison with a modest decrease in the envelope group (sample sizes too small to determine significance) (Figure 1).

Conclusion

The results demonstrate periodic LVZ testing in the S-ICD monitoring system can reliably trend changes in system impedance over time. Impedance measurements within the first 6–7 months (and most markedly within the first 3 months) appear to be transiently lower than the values seen after this timepoint suggesting that early impedance measurements may not predict steady-state impedance. Further studies are needed to explore the impact of envelope use and the S-ICD impedance changes beyond 30 months.

Funding Acknowledgement

Type of funding sources: None.

Intermittent Epicardial Lead Failure Detected Using a Continuous Ambulatory Electrocardiogram Monitor

A 69-year-old man received epicardial pacing leads for complete atrioventricular block that occurred during a mechanical tricuspid valve replacement procedure. During follow-up, the patient reported intermittent episodes of dizziness and bradycardia. Remote transmissions and device interrogations failed to elucidate the cause of his symptoms. A continuous ambulatory electrocardiogram (ECG) monitor was used as an alternative diagnostic tool. Multiple pauses were detected by the monitor and, upon review, these events were deemed to be due to the intermittent loss of capture by the epicardial lead. Once this diagnosis was made and the malfunctioning lead was replaced, the patient’s symptoms resolved. This case highlights the novel use of a continuous ambulatory ECG monitor in diagnosing intermittent loss of capture, which was not detected by remote monitoring or device interrogations.

Antibiotic-Eluting Envelopes to Prevent Cardiac-Implantable Electronic Device Infection: Past, Present, and Future

Objective: Cardiac-implantable electronic device (CIED) infections are associated with significant morbidity and mortality. In this review, we describe the risk factors and pathogenesis of CIED infections and review the rationale and the evidence for the use of antibiotic-eluting envelopes (ABEs) in patients at increased risk for CIED infections.

Findings: The majority of CIED infections are caused by staphylococci that involve generator pocket and occur due to contamination of the device or the pocket tissues at the time of implantation. Clinical trials have shown that extending the duration of post-operative systemic antibacterial therapy is not beneficial in reducing CIED infection rate. However, ABEs that reduce device migration after implantation and provide sustained local delivery of prophylactic antibiotics at the pocket site, may provide benefit in reducing infection. Currently, there are two types of commercially available CIED envelope devices in the United States. The first ABE device (TYRX™, Medtronic Inc., Monmouth Junction, NJ) is composed of a synthetic absorbable mesh envelope that elutes minocycline and rifampin and has been shown to reduce CIED pocket infections in a large multi-center randomized clinical trial. The second ABE device (CanGaroo-G™, Aziyo Biologics, Silver Spring, MD) is composed of decellularized extracellular matrix (ECM) and was originally designed to stabilize the device within the pocket, limiting risk for migration or erosion, and providing a substrate for tissue ingrowth in a preclinical study. This device has shown promising results in a preclinical study with local delivery of gentamicin. Compared with artificial materials, such as synthetic surgical mesh, biologic ECM has been shown to foster greater tissue integration and vascular ingrowth, a reduced inflammatory response, and more rapid clearance of bacteria.

Conclusions and Relevance: ABE devices provide sustained local delivery of antibiotics at the generator pocket site and appear beneficial in reducing CIED pocket infections. Given the continued increase in the use of CIED therapy and resultant infectious complications, innovative approaches to infection prevention are critical.

Esophageal injury associated with catheter ablation for atrial fibrillation: Determinants of risk and protective strategies

Catheter ablation has become an important element in the management of atrial fibrillation. Several technical advances allowed for better safety profiles and lower recurrence rates, leading to an increasing number of ablations worldwide. Despite that, major complications are still reported, and esophageal thermal injury remains a significant concern as atrioesophageal fistula (AEF) is often fatal. Recognition of the mechanisms involved in the process of esophageal lesion formation and the identification of the main determinants of risk have set the grounds for the development and improvement of different esophageal protective strategies. More sensitive esophageal temperature monitoring, safer ablation parameters and catheters, and different energy sources appear to collectively reduce the risk of esophageal thermal injury. Adjunctive measures such as the prophylactic use of proton-pump inhibitors, as well as esophageal cooling or deviation devices, have emerged as complementary methods with variable but promising results. Nevertheless, as a multifactorial problem, no single esophageal protective measure has proven to be sufficiently effective to eliminate the risk, and further investigation is still warranted. Early screening in the patients at risk and prompt intervention in the cases of AEF are important risk modifiers and yield better outcomes.

Preclinical evaluation of efficacy and pharmacokinetics of gentamicin containing extracellular-matrix envelope

BACKGROUND

Using synthetic antibiotic-eluting envelope (ABE) is an effective intervention for prevention of cardiovascular implantable electronic device (CIED) infection. The biologic extracellular-matrix envelope (ECME), may offer potential advantages over the synthetic ABE. To further minimize the risk of infection, the ECME can be hydrated in gentamicin prior to CIED implantation. We aimed to evaluate the efficacy and pharmacokinetics (PK) of gentamicin containing ECME in an animal model.

METHODS

For all experiments, the ECME was hydrated in gentamicin (40 mg/Ml) (treatment) for 2 min. In vitro antimicrobial efficacy against six different bacterial species was assessed. In vivo experiments were conducted using a rabbit model of CIED pocket infection. Serum and ECM gentamicin concentrations were measured. Five different organisms were inoculated into the device pocket of control (ECME hydrated in 0.9% saline) and treatment groups. Macroscopic appearance and colony forming units from CIED, ECME, and tissue were determined.

RESULTS

No bacteria were recovered from any culture after 12 h of exposure to the gentamicin containing ECME. Serum gentamicin levels dropped below the limit of quantification at 15 h after implant. Gentamicin concentration in the ECME remained relatively stable for up to 7 days. Signs of clinical infection were observed in the control but not in the treatment group. In the presence of gentamicin, statistically significant reduction was demonstrated across all tested bacterial species.

CONCLUSIONS

In this preclinical animal infection model, gentamicin containing ECME was highly effective in reducing bacterial burden in the implant pocket, while systemic exposure after implantation remained low.

P1021Comparative efficacy of microfidelity technology vs standard ablation for atrioventricular nodal ablation

Background

Microfidelity Cateter Technology has proven efficacy in ablating atrial arrhythmias in multiple pilot studies. Closely spaced radial microelectrodes render a focused near-field electrogram. Case series suggest that this catheter design facilitates accurate ablations with fewer radiofrequency (RF) lesions. Atrioventricular junction (AVJ) ablation is regarded as a straightforward procedure, but case records show wide variance in procedure times and number of RF lesions required.

Methods

Twenty-four patients scheduled for AVJ ablation were randomized to treatment with either the Microfidelity technology or standard 8mm/8 French ablation catheter. Both groups located the AVJ by fluoroscopic landmarks and His electrograms, and the MiFi group used electroanatomical mapping to create the location of his electrograms. The primary endpoints were development of Junctional Rhythm (JR) or Complete Heart Block (CHB), and time from first RF lesion until rhythm change. Secondary endpoints included number of RF applications.

Results

Patients were randomized one-to-one to the MiFi arm or standard ablation arm. JR or CHB was achieved in all patients. Time from first RF lesion until JR/CHB was: (Median/IQR) 325 sec/250–1270 sec. vs 287 sec/101–406 sec. Number of RF applications was 5/3–15 applications vs 4.5/1–5 applications. Total procedure time in the lab was 134 min/73.5–172.5 min vs 58 min/52–146 min.

Microfidelity Technology vs Standard

Conclusion

Analysis suggests that the MiFi catheter is efficacious in ablating the AVJ, but requires greater RF duration and number of lesions, with wider case-by-case variability to achieve JR or CHB. Microfidelity technology and electroanatomical mapping did not result in faster time to completion than using fluoroscopic landmarks and His electrograms alone. Preoperative choice of sheath for catheter stability and contact may also play a role in a more efficient timely successful ablation of the AV node.

Acknowledgement/Funding

Boston Scientific

Abstract 163: Implementation of a Physician Order Set Improves Adherence to Cardiac Care Unit Policy: A Quality Improvement Initiative

Objective: To determine if using physician order sets within the electronic health record improves adherence with local policy in the Cardiac Care Unit (CCU) at University of Florida Health - Jacksonville (UFH-J)

Background: In 2015, CCU at UFH-J implemented a policy to guide the utilization of wearable cardioverter-defibrillators (WCD) in patients with heart failure and ejection fraction less or equal to 35%. Adherence to this policy was sparse and needed improvement.

Methods: We hypothesized that developing an electronic order set would improve adherence to existing CCU policy. The policy to be addressed was the CCU WCD policy. Pre-intervention data from January 1-June 30, 2016 was analyzed for compliance. We evaluated policy compliance in heart failure patients admitted to the CCU. On July 1, 2016, a CCU admission order set, including a section on the WCD policy, launched. The order set was developed with multi-disciplinary input from nursing, nutrition, pharmacy, and physicians. To ensure adequate time for adjustment to the order set, the post-intervention data set was collected from January 1 - June 30, 2017.

Results: Implementation of the CCU admission order set resulted in a 23% absolute increase in compliance with the CCU WCD policy. Additional benefits of the implementation of the order set that were not directly evaluated in this study include standardization of initial evaluation and patient care, improvement in the selection of the appropriate diet for cardiac patients with other dietary considerations including diabetes and renal disease, and an increase in the utilization of cardiac rehabilitation upon discharge.

Conclusion: Implementation of an order set is an effective way to improve adherence to patient care policy. Further studies to assess impact of physician order sets on morbidity and mortality, especially in patients with a WCD are warranted.

Failed Maximal Defibrillation Threshold Testing in the Subcutaneous Implantable Cardioverter Defibrillator

The subcutaneous implantable cardioverter defibrillator (S-ICD) registry included very few patients with a body mass index (BMI) greater than 40. We present a case of a 40-year-old male with a BMI of 44 and ejection fraction of 25% who underwent S-ICD implantation for primary prevention of sudden cardiac death in the setting of a nonischemic cardiomyopathy. Defibrillation threshold (DFT) testing failed at high output. A posterior to anterior radiograph demonstrated migration of the components despite positioning under fluoroscopy. After repositioning, repeat DFT testing showed an inconsistent efficacy. We discuss the probabilistic nature of DFT testing, clinical factors affecting the S-ICD implant in the obese population and offer a novel insight from this specific experience.

MRI Evaluation of Radiofrequency, Cryothermal, and Laser Left Atrial Lesion Formation in Patients with Atrial Fibrillation

BACKGROUND

 Catheter ablation utilizing radiofrequency (RF), Cryothermal (Cryo), or Laser energy is effective for treatment of atrial fibrillation (AF). Late gadolinium enhancement magnetic resonance imaging (LGE-MRI) has been used to estimate the burden of left atrial (LA) fibrosis, but no data exist regarding structural changes following each modality. We sought to compare the baseline to postprocedure change in LA scar burden following RF, Cryo, or Laser ablation for treatment of AF.

METHODS

Seventeen patients with AF underwent initial pulmonary vein (PV) isolation (PVI) using RF (n = 7), Cryo (n = 5), and Laser (n = 5). LGE-MRI was performed prior to and at 24 hours and 3 months after PVI.

RESULTS

In a linear mixed-effects model, accounting for intrapatient clustering of data and interpatient differences in baseline scar, LGE extent was significantly increased at 24 hours postablation (+14.6 ± 1.9% of LA myocardium, P < 0.001), and remained stable from 24 hours to 3 months (+0.12 ± 1.9%, P = 0.951). There was no statistically significant difference between the postablation scar extent among ablation modalities when compared to RF (Cryo +4.5 ± 3.0%, P = 0.123; Laser -3.2 ± 3.0%, P = 0.291). The PV antral LGE intensity was increased by 25.1 ± 3.8% (P<0.001) 24 hours after ablation and additionally increased by 8.1 ± 3.8 at 3 months (P = 0.033).

CONCLUSIONS

Radiofrequency, Cryo, and laser ablation result in increased LGE extent and intensity at 24 hours and 3 months postablation. No statistically significant difference was noted in the extent of fibrosis induced by any modality.

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.

An Approach to Catheter Ablation of Atrial Fibrillation in the Elderly

Atrial fibrillation (AF) is the most common sustained arrhythmia encountered in clinical practice with a prevalence that is increasing with age. During the past decade, catheter ablation of AF has rapidly evolved from a highly experimental unproved procedure, to its current status as a commonly performed procedure in many major hospitals throughout the world for symptomatic, drug refractory, paroxysmal, and persistent AF. With improved safety and advances in technique, catheter ablation has also been offered to the elderly. This article reviews the most current literature with respect to long-term clinical efficacy, risks, and benefits of catheter ablation of AF in the elderly.

Novel oscillatory mechanisms in the cholinergic control of Guinea pig sino-atrial node discharge

Oscillatory Mechanisms in Sinus Node Cholinergic Control. 

INTRODUCTION

The role of the oscillatory after-potential V(os) and pre-potential ThV(os) in cholinergic control of discharge was studied in sino-atrial node (SAN).

METHODS AND RESULTS

A microelectrode technique was used in isolated guinea-pig SAN superfused in vitro in high [K(+) ](o) to visualize V(os) and ThV(os) . The cholinergic agonist carbachol (CCh) decreased the amplitude and slope of V(os) and ThV(os) at a time when there was no increase in maximum diastolic potential. The slowing in SAN rate was due to slower and smaller ThV(os) that missed intermittently the threshold and occurred gradually later in diastole, but not to a decrease in the intrinsic rate of ThV(os) . Eventually, quiescence followed. Larger CCh concentrations quickly induced a hyperpolarization that altogether prevented the occurrence of oscillatory potentials. During CCh washout, ThV(os) reappeared and consistently reinitiated discharge. Lower [Ca(2+) ](o) also decreased slopes and amplitude of V(os) and ThV(os) , thereby slowing and stopping SAN discharge, as CCh did. Overdrive temporarily offset the negative chronotropic effects of CCh and of low [Ca(2+) ](o.) Cesium (a blocker of hyperpolarization-activated current I(f) ) did not abolish CCh inhibitory effects on oscillatory potentials.

CONCLUSIONS

The cholinergic agonist CCh: (1) slows SAN discharge by decreasing the amplitude of V(os) and ThV(os) , but not the rate of ThV(os) ; (2) can cause hyperpolarization that altogether suppresses the oscillatory potentials; (3) is mimicked in its effects by low [Ca(2+) ](o) ; (4) is antagonized by procedures that increase cellular calcium; and (5) modifies the oscillatory potentials independently of I(f) .

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.

Essential role of diastolic oscillatory potentials in adrenergic control of guinea pig sino-atrial node discharge

Background

The diastolic oscillatory after-potential V_os and pre-potential ThV_os play an essential role in the pacemaker mechanism of sino-atrial node (SAN). The aim of this study was to investigate whether these oscillatory potentials are also involved in adrenergic control of SAN discharge.

Methods

V_os and ThV_os were visualized by superfusing guinea pig SAN in high [K⁺]_o. The actions of adrenergic agonists on oscillatory potentials were studied by means of a microelectrode technique. Statistical significance was determined by means of Student's paired t-test.

Results

In non-spontaneous SAN, norepinephrine (NE) decreased the resting potential into a voltage range ("oscillatory zone") where increasingly larger ThV_os appeared and initiated spontaneous discharge. In slowly discharging SAN, NE gradually increased the rate by increasing the amplitude and slope of earlier-occurring ThV_os and of V_os until these oscillations fused with initial diastolic depolarization (DD₁). In the presence of NE, sudden fast rhythms were initiated by large V_os that entered a more negative oscillatory zone and initiated a large ThV_os. Recovery from NE exposure involved the converse changes. The β-adrenergic agonist isoproterenol had similar actions. Increasing calcium load by decreasing high [K⁺]_o, by fast drive or by recovery in Tyrode solution led to growth of V_os and ThV_os which abruptly fused when a fast sudden rhythm was induced. Low [Ca²⁺]_o antagonized the adrenergic actions. Cesium (a blocker of I_f) induced spontaneous discharge in quiescent SAN through ThV_os. In spontaneous SAN, Cs⁺increased V_os and ThV_os, thereby increasing the rate. Cs⁺ did not hinder the positive chronotropic action of NE. Barium increased the rate, as Cs⁺ did.

Conclusion

Adrenergic agonists: (i) initiate SAN discharge by decreasing the resting potential and inducing ThV_os; (ii) gradually accelerate SAN rate by predominantly increasing size and slope of earlier and more negative ThV_os; (iii) can induce sudden fast rhythms through the abrupt fusion of large V_os with large ThV_os; (iv) increase V_os and ThV_osby increasing cellular calcium; and (v) do not modify the oscillatory potentials by means of the hyperpolarization-activated current I_f. The results provide evidence for novel mechanisms by which the SAN dominant pacemaker activity is initiated and enhanced by adrenergic agonists.

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.

Rapid progression of atrioventricular nodal blockade in a patient with systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is a multisystem disorder with numerous potential adverse effects on the cardiovascular system. These complications likely develop in most patients with SLE at some time during the course of their disease, in part due to the decreased mortality associated with SLE as a result of modem medical management. Conduction disturbances have been reported in the literature to occur primarily from the progression of SLE and secondarily from pharmacotherapy used to treat SLE and may first be evident on the electrocardiogram in the emergency department (ED) setting. Electrocardiogram abnormalities such as borderline first-degree heart block may be clues to more significant cardiac disease brought upon by years of chronic inflammation, myocarditis, vasculitis, and fibrosis that are often the result of longstanding autoimmune disease. It is essential that patients with autoimmune disease be screened carefully in the ED setting for underlying myocardial disease, particularly given the increased potential for atherosclerosis, ischemia, arrhythmias, and myocardial conduction defects in these patients.

Electrocardiographic T-wave changes underlying acute cardiac and cerebral events

T-wave inversions produced by myocardial infarction (MI) are classically narrow and symmetric. Electrocardiography T-wave changes including low-amplitude and abnormally inverted T waves may be the result of noncardiac path physiology. We present a series of cases that presented with different electrocardiography T-wave changes. The first case involved a 64-year-old woman who presented to the emergency department with diffuse splayed T-wave inversions and was found to have an MI in the context of an acute cerebrovascular accident. We contrasted this case with that of a 76-year-old man with hypercholesterolemia who presented with T-wave widening and a prolonged QT interval and was found to have a subarachnoid hemorrhage secondary to a basilar aneurysm and no MI. Several mechanisms have been suggested to explain the cardiac and cerebral injury, including microvascular spasm and increased levels of circulating catecholamines. Accurate interpretation of T-wave changes can assist the clinician toward a timely therapeutic intervention and accurate diagnosis.

Exertional rhabdomyolysis and renal failure in patients with sickle cell trait: is it time to change our approach?

Based upon numerous reported cases and despite widespread beliefs to the contrary, sickle cell trait (SCT) may be deemed a quantifiable risk factor in certain subsets of patients. As a result of common misconceptions regarding SCT, most individuals with the condition are generally not informed regarding the possible consequences of certain activities such as venturing to high altitudes or participating in overly exertional physical activities. Acute exertional rhabdomyolysis is a potentially serious clinical illness and is caused by skeletal muscle injury resulting in the release of myoglobin and other cellular contents, including creatine kinase, into the circulatory system. Mild to moderate cases of acute exertional rhabdomyolysis can cause metabolic disorders including hypernatremia, hyperkalemia, hyperphosphatemia, hypocalcemia, lactic acidosis and hyperuricemia. Severe cases may result in renal failure and even death. Several case reports have been published since the early 1970s describing significant morbidity and mortality of acute exertional rhabdomyolysis in patients with SCT. We present the case of a 27-year-old male with a past medical history significant only for SCT who presented after a 1.5 mile run with severe exertional rhabdomyolysis and subsequent acute renal failure requiring hemodialysis (HD). In presenting this case, we hope to raise awareness of a possible underlying cause to many cases of exertional rhabdomyolysis and encourage physicians to counsel their patients with SCT in order to avoid the significant morbidity and mortality that may be associated with the condition.

Clinical investigation: Utility of left ventricular end diastolic diameter in the prediction of susceptibility to ventricular tachyarrhythmias

BACKGROUND

Prior studies have shown the utility of using both QRS duration and QT dispersion (QTd) as predictors of risk for ventricular tachyarrhythmias (VA). Lengthening of the QRS duration represents dyssynchrony of regional myocardial wall contraction, and increased QTd similarly represents variations in myocardial repolarization. We sought to examine the left ventricular end diastolic diameter (LVEDD) as a predictor of VA susceptibility.

METHODS

Eighty-eight patients referred for electrophysiologic (EP) studies were evaluated. EP testing was performed using a standard protocol of up to three extrastimuli. QTd and QRS duration analyses were performed in a blinded manner. Values were defined as abnormal if QRS duration>120 ms, QTd>60 ms, and LVEDD>6 cm.

RESULTS

Of 88 patients (65 males; 23 females; mean age 67+/-15 years), 33 were inducible by EP testing. Patients with either increased QRS duration or QTd are shown to be at greater risk for VA inducibility. LVEDD is a strong predictor of inducibility for VA (p<0.02 between inducible and non-inducible patients). LVEDD in combination with QRS duration and QTd, further strengthens predictability for VA (p<0.03 for QRS duration and p<0.02 for QTd) with a trend towards inducibility as each value increases. Combination of the three parameters of QRS duration, QTd, and LVEDD was 91% sensitive for the identification of those patients inducible for VA.

CONCLUSION

The LVEDD is an echocardiographic value that strongly predicts VA inducibility, and when combined with QRS duration and QTd, identifies patients at higher risk for these tachyarrhythmias.

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.

Clinical Predictors of Appropriate Implantable-Cardioverter Defibrillator Discharge

BACKGROUND

The implantable cardioverter-defibrillator (ICD) is the mainstay of treatment for ventricular tachyarrhythmias due to its impact on mortality. ICD discharges may be appropriate or inappropriate, and identification of patients at risk for ICD discharge is essential. We sought to determine the predictors of appropriate ICD discharge.

METHODS

We analyzed data from 591 ICD recipients (mean age 67.9 +/- 13.0 years; 474 men; mean follow-up 10.9 +/- 13.8 months). The association between ICD discharges and multiple clinical variables, including age, gender, hypertension, diabetes, coronary artery bypass graft (CABG) surgery, syncope, atrial fibrillation (AF), prior coronary intervention, left ventricular ejection fraction (LVEF), left ventricular end diastolic dimension, left ventricular end systolic dimension (LVESD), and ambient drug therapy was examined.

RESULTS

The rates of appropriate or inappropriate discharges, delivered to 155 patients, were 0.49 per follow-up year (F/Y). The median time-to-first appropriate discharge was 3.4 years. Among the discharges delivered, 97(63%) were appropriate and 58(37%) were inappropriate. Risk factors associated with a trend toward earlier appropriate discharges included age </= 65 years, and diuretic and digitalis use. By multiple variable analysis, no history of CABG and an enlarged LVESD were independent predictors of earlier appropriate ICD discharge.

CONCLUSIONS

Patients who did not have CABG revascularization were 2.8-fold more likely than those who underwent CABG, and patients with enlarged LVESD were 2.5-fold more likely than those with normal LVESD to receive appropriate ICD discharges. These patients deserve special vigilance and management in order to prevent the occurrence of ventricular tachyarrhythmias triggering ICD discharges.

On the mechanisms underlying diastolic voltage oscillations in the sinoatrial node

AIM

The study of the mechanisms underlying the oscillatory afterpotential (V(os)) and prepotential (ThV(os)).

BACKGROUND

It has been recently shown that V(os) and ThV(os) play an obligatory role in the dominant sinoatrial node (SAN) discharge.

METHODS

Guinea pig isolated SAN was studied in vitro by means of a microelectrode technique.

RESULTS

High [K(+)](o) and premature stimuli unmask V(os) superimposed on early diastolic depolarization and ThV(os) within a less negative voltage range ("oscillatory zone"). Subthreshold stimuli elicit ThV(os) in the oscillatory zone, but not at more negative values. Drive and caffeine shift the oscillatory zone in a negative direction. Low caffeine concentrations increase the size of V(os) and of ThV(os), rate, and force. High caffeine concentrations suppress V(os) but increase the size of ThV(os) and shift them to more negative values until they eventually miss the threshold. In quiescent SAN in high caffeine, a fast drive enhances ThV(os) size, thereby initiating a transient spontaneous rhythm ("overdrive excitation"). Adrenergic agonists potentiate caffeine-induced overdrive excitation through an increase in ThV(os). In high caffeine, the first twitch after quiescence is not larger, twitch relaxation is slower, V(os) is abolished, and the prolonged nonoscillatory afterdepolarization V(ex) is induced, consistent with an impairment of Ca2+ handling by the sarcoplasmic reticulum. The effects of caffeine in Tyrode's solution are accounted for by the caffeine-induced changes in the oscillatory potentials. Tetrodotoxin decreases force and size of both V(os) and ThV(os).

CONCLUSIONS

The mechanism underlying V(os) is related to a diastolic release of Ca2+ from a Ca2+-overloaded sarcoplasmic reticulum, whereas that of ThV(os) appears to be related to ionic currents in the resting potential range that can initiate and sustain spontaneous discharge.