Conduction abnormalities and role of cardiac pacing in cardiac amyloidosis: A systematic review.

Cardiac amyloidosis (CA) is an increasingly recognized cause of heart failure, characterized by extracellular deposition of insoluble protein fibrils leading to progressive myocardial dysfunction. The most common types of cardiac amyloidosis are immunoglobin light-chain (AL) and transthyretin (ATTR). Conduction abnormalities are commonly encountered among patients with cardiac amyloidosis and are an important cause of morbidity and mortality. Abnormalities range from infra-Hisian intraventricular conduction delay and bundle branch block to complete atrioventricular block. Pacemaker placement in CA patients follows established guidelines, similar to those for patients without CA, with generally good efficacy. The role and appropriate timing of pacemakers for primary prevention of brady-arrhythmias in CA remains uncertain. While biventricular (BiV) pacing has been shown to improve clinical outcomes in patients with systolic heart failure without CA, there are few data examining the utility of BiV pacing in patients with CA. With the advent of effective treatments for AL and ATTR, appropriate application of pacing is important to support patients with CA and conduction disease through therapeutic trials. This systematic review summarizes the current literature examining the utility of pacing in CA.

Heterogeneity in Conduction Underlies Obesity-Related Atrial Fibrillation Vulnerability.

BACKGROUND: Obese patients are more vulnerable to development of atrial fibrillation but pathophysiology underlying this relation is only partly understood. The aim of this study is to compare the severity and extensiveness of conduction disorders between obese patients and nonobese patients measured at a high-resolution scale. METHODS: Patients (N=212) undergoing cardiac surgery (male:161, 63±11 years) underwent epicardial mapping of the right atrium, Bachmann bundle, and left atrium during sinus rhythm. Conduction delay (CD) was defined as interelectrode conduction time of 7 to 11 ms and conduction block (CB) as conduction time ≥12 ms. Prevalence of CD/CB, continuous CDCB (cCDCB), length of CD/CB/cCDCB lines, and severity of CB were analyzed. RESULTS: In obese patients, the overall incidence of CD (3.1% versus 2.6%; P=0.002), CB (1.8% versus 1.2%; P<0.001), and cCDCB (2.6% versus 1.9%; P<0.001) was higher and CD (P=0.012) and cCDCB (P<0.001) lines are longer. There were more conduction disorders at Bachmann bundle and this area has a higher incidence of CD (4.4% versus 3.3%, P=0.002), CB (3.1% versus 1.6%, P<0.001), cCDCB (4.6% versus 2.7%, P<0.001) and longer CD (P<0.001) or cCDCB (P=0.017) lines. The severity of CB is also higher, particularly in the Bachmann bundle (P=0.008) and pulmonary vein (P=0.020) areas. In addition, obese patients have a higher incidence of early de-novo postoperative atrial fibrillation (P=0.003). Body mass index (P=0.037) and the overall amount of CB (P=0.012) were independent predictors for incidence of early postoperative atrial fibrillation. CONCLUSIONS: Compared with nonobese patients, obese patients have higher incidences of conduction disorders, which are also more extensive and more severe. These differences in heterogeneity in conduction are already present during sinus rhythm and may explain the higher vulnerability to atrial fibrillation of obese patients.

Visualization and quantification of the atrioventricular conduction axis in hearts with ventricular septal defect using phase contrast computed tomography.

OBJECTIVE: To visualize and quantify the atrioventricular conduction axis in the setting of ventricular septal defect using phase contrast computed tomography. METHODS: We used the SPring-8 synchrotron radiation facility in Hyogo prefecture in Japan, processing and reconstructing the data with 3-dimensional software. RESULTS: We studied 8 hearts obtained from patients known to have had ventricular septal defects, aged from 6 to 150 days, with a median of 24.5 days. None of the individuals, however, had undergone corrective surgery. The penetrating bundle was found at a median of 1.43 mm from the septal crest, with a range of 0.99 to 1.54 mm. The distance to the nonbranching bundle to the right ventricular endocardium was 1.10 mm, with a range from 0.49 to 2.49 mm, to the origin of the left bundle branch was 2.46 mm, with a range from 1.7 to 3.18 mm, and to the origin of the right bundle branch was 2.34 mm, with a range from 0.50 to 2.59 mm. The median distance from the edge of the caudal limb of the septomarginal trabeculation to the right bundle branch was 1.04 mm, with a range from 0.81 to 1.16 mm. CONCLUSIONS: We were able to show the precise location of the axis, with our findings suggesting that longitudinal sutures placed along the posteroinferior rim should be effective in avoiding iatrogenic injury, but sutures should not be placed in the valley between the limbs of the septomarginal trabeculation.

Long-term Follow-up of Epicardial Pacing and Left Ventricular Dysfunction in Children With Congenital Heart Block.

BACKGROUND: Patients with congenital complete atrioventricular block often require lifelong pacemaker therapy, which has a risk of left ventricular (LV) dysfunction. The aim of our study was to determine the long-term effects of epicardial pacing on LV function and dyssynchrony in children with congenital heart block. METHODS: We conducted a retrospective study at a single tertiary center in which 34 pediatric patients with isolated congenital complete heart block who underwent epicardial pacemaker implantation from 1987 to 2016 were enrolled. RESULTS: Median age during pacemaker insertion was 2.5 years (range, 0-16.7 years) and the median follow-up duration was 12.3 years. The initial pacing sites were the right ventricle (RV) free wall for 10 patients, RV apex for 16, and LV apex for eight. LV dysfunction developed in 7 patients, of whom 4 underwent lead relocation to the RV apex (n = 2) and cardiac resynchronization therapy upgrade (n = 2). RV free-wall pacing had a significantly higher risk of LV dysfunction than either LV or RV apical pacing (odds ratio 52.5; P = .003; 95% confidence interval 3.9-700). All 4 patients who underwent lead repositioning showed improvement of LV function (median ejection fraction, 24%-62.7%). CONCLUSIONS: Our study suggests that RV free-wall pacing may be a significant risk factor for LV dysfunction. Pacemaker-induced LV dysfunction was improved via lead relocation to the RV apex or cardiac resynchronization therapy upgrade. Future studies with a larger sample size and longer-term follow-up are required to confirm our results.

Permanent pacing and conduction recovery in patients undergoing cardiac surgery for active infective endocarditis in an Australian Tertiary Center.

BACKGROUND: Postoperative heart block is common among patients undergoing surgery for infective endocarditis (IE). Limited data exists allowing cardiologists to predict who will require permanent pacemaker (PPM) implantation postoperatively. We aimed to determine the rate of postoperative PPM insertion, predictors for postoperative PPM, and describe PPM utilization and rates of device-related infection during follow-up. MATERIALS AND METHODS: A retrospective analysis was performed of 191 consecutive patients from a single institution who underwent cardiac surgery for IE between 2001 and 2017. Preoperative and operative predictors for postoperative PPM were evaluated using univariate and multivariate logistic regression. RESULTS: The rate of postoperative PPM implantation was 11% (17/154). The PPM group had more preoperative prolonged PR interval alone (33% vs 12%; P = .03), coexistent prolonged PR and QRS durations (13% vs 2%; P = .01), infection beyond the valve leaflets (82% vs 41%; P = .001), aortic root debridement (65% vs 23%; P = <.001), patch repair (47% vs 20%; P = .01), postoperative prolonged PR interval (50% vs 24%; P = .01), and prolonged QRS duration (47% vs 15%; P = .001). On multivariate analysis, infection beyond the valve leaflets emerged as an independent predictor for postoperative PPM (odds ratio, 1.94, 95% confidence interval, 1.14-3.28; P = .014). A reduction in PPM utilization was observed in five patients while eight patients continued to show significant ventricular pacing with no underlying rhythm at 12 months. There were no device-related infections. CONCLUSION: Postoperative PPM was required in 11% of patients undergoing surgery for IE over a 16-year period. Infection beyond the valve leaflet was an independent predictor for postoperative PPM insertion.

Interesting case of narrow QRS tachycardia. What is the mechanism?

A 67-year-old female presented with history of recurrent palpitations. During one of the episodes of palpitation, a narrow QRS tachycardia was recorded and it was reported to be terminated with intravenous adenosine. The 12-lead electrocardiogram (ECG) showed no manifest ventricular preexcitation. ECG was within normal limits. The patient underwent an electrophysiology study after informed consent. She was taking calcium channel blockers and that was stopped five half-lives prior to the procedure. As catheters were being placed, a narrow QRS tachycardia got induced. During the study, there was development of right bundle branch block during the tachycardia. What is the mechanism of the tachycardia?

Mitral Annulus Calcium Score.

BACKGROUND: The risk of conduction system abnormalities (CSA) after transcatheter aortic valve implantation remains high. We aimed to evaluate the impact of mitral annular calcium (MAC) score on the development of CSA after transcatheter aortic valve implantation. METHODS: Consecutive patients (n=168), with severe AoV stenosis, without prior CSA, underwent computed tomography transcatheter AoV implantation followed by device implantation; CoreValve (n=72) and SAPIEN (n=96). MAC, AoV, and left ventricular outflow tract calcium (Ca++) scores were quantitated from noncontrast ECG-gated computed tomography using Agatston method. The primary end point was a combination of complete left bundle branch block or high-degree atrioventricular block. Logistic regression was used to analyze the predictive value of Ca++ scores of different locations. RESULTS: The primary end point was documented in 62% of the fourth quartile MAC score (>2700) patients as compared with 31% of the first quartile (<140); P=0.03. Logistic regression analysis documented MAC score as an independent predictor either of primary end point as a continuous variable (odds ratio: 1.02, 95% [CI]: 1.00 - 1.03, p = 0.021) or as quartile cutoffs, whereas Q4 was a strong and independent predictor (odds ratio: 3.69, 95% [CI]: 1.37 - 9.95, p = 0.010). CONCLUSIONS: MAC score was found to be an independent predictor of CSA in patients undergoing transcatheter aortic valve implantation without preexisting CSA. Therefore, the current study suggests that patients with high MAC score category (fourth MAC score quartile) should be considered at high risk for CSA, warranting closer monitoring. CLINICAL TRIAL REGISTRATION: URL: https://www.clinicaltrials.gov. Unique identifier: NCT02023060.

Traumatic Fracture of Pacemaker Lead by Suture Transfixation to Pectoral Muscle.

We report acute lead fracture during pacemaker implantation. Suturing the lead without the sleeve might damage the lead. To avoid this result, we suggest tying knots tightly, but not too vigorously.

Cardiac voltage-gated sodium channel mutations associated with left atrial dysfunction and stroke in children.

Aims: Cardiac atrial arrhythmias are the most common type of heart rhythm disorders. Its genetic elucidation remains challenging with poor understanding of cellular and molecular processes. These arrhythmias usually affect elderly population but in rare cases, young children may also suffer from such electrical diseases. Severe complications, including stroke, are commonly age related. This study aims to identify a genetic link between electro-mechanic atrial dysfunction and stroke in children. Methods and results: In two unrelated boys of 11 and 14 years with both stroke and atrial arrhythmias, the clinical phenotype was determined through a complete physical examination, electrocardiogram (ECG), Holter ECG, and computed tomography. The genetic testing was performed on a large 95 genes panel implicated in myocardial electrical imbalance, using the next generation sequencing method. The panel also includes the genes usually associated with the development of cardiomyopathies. In one child, a left atrial dilation was observed. The 2nd boy suffered from atrial standstill. Both suffered from atrial bradycardia, flutter, and fibrillation. The complete genetic testing revealed the SCN5A c.3823G>A (p.D1275N) mutation in the first family, c.1141-2A>G and c.3157G>A (p.E1053K) mutations in the second family. Conclusion: Our results strengthen the association between Nav1.5 mutations and the occurrence of stroke in young patients. It emphasizes the need to look for atrial myopathy in the decision process for anticoagulation in young patients with atrial arrhythmic events.

Single-site ventricular pacing via the coronary sinus in patients with tricuspid valve disease.

Aims: To evaluate coronary sinus single-site (CSSS) left ventricular pacing in adult patients with normal left ventricular ejection fraction (LVEF) when traditional right ventricular lead implantation is not feasible or is contraindicated. Methods and results: We performed a retrospective analysis of 23 patients with tricuspid valve surgery/disease who received a CSSS ventricular pacing lead to avoid crossing the tricuspid valve. Two matched control populations were obtained from patients receiving (i) conventional right ventricular single-site (RVSS) leads and (ii) coronary sinus leads for cardiac resynchronization therapy (CSCRT). Main outcomes of interest were lead stability, electrical lead parameters and change in LVEF during long-term follow-up. Successful CSSS pacing was accomplished in all 23 patients without any procedural complications. During the 5.3 ± 2.8-year follow-up 22/23 (95.7%) leads were functional with stable pacing and sensing parameters, and 1/23 (4.3%) was extracted for unrelated reasons. Compared to CSSS leads, the lead revision/abandonment was similar with RVSS leads (Hazard ratio (HR) 0.87, 95% confidence interval (CI) 0.03, 22.0), but was higher with CSCRT leads (HR 7.41, 95% CI 1.30, 139.0). There was no difference in change in LVEF between CSSS and RVSS groups (-2.4 ± 11.0 vs. 1.5 ± 12.8, P = 0.76), but LVEF improved in CSCRT group (11.2 ± 16.5%, P = 0.002). Fluoroscopy times were longer during implantation of CSSS compared to RVSS leads (25.6 ± 24.6 min vs. 12.3 ± 18.6 min, P = 0.049). Conclusion: In patients with normal LVEF, single-site ventricular pacing via the coronary sinus is a feasible, safe and reliable alternative to right ventricular pacing.

Tackling the Issue of High Postoperative Pacemaker Implantation Rates in Sutureless Aortic Valve Replacement: Should Balloon Inflation be Removed from the Implantation Method of the Perceval Prosthesis?

BACKGROUND: Sutureless aortic valve replacement (AVR) is an emerging alternative to standard AVR in elderly and high-risk patients. This procedure is associated with a high rate of postoperative permanent pacemaker implantation (PPI). The study aim was to assess the impact on the rate of PPI of implanting the Perceval prosthesis without using balloon inflation. METHODS: A total of 159 patients who underwent sutureless AVR using the Perceval prosthesis was included. Balloon inflation was used in 132 patients (Balloon group) and not used in the remaining 27 (No-Balloon group). Clinical, echocardiographic and electrocardiographic outcomes were assessed. RESULTS: There was no significant difference in PPI rate between the two groups (26% for Balloon group versus 22% in No-Balloon group; p = 0.700). Balloon inflation had no significant impact on the incidence of paravalvular leaks (p = 0.839), or on the need to return to cardiopulmonary bypass (CPB) intraoperatively due to paravalvular leak or unsatisfactory deployment (p >0.999). Mean and peak transaortic pressure gradients were similar between the two groups (p = 0.417 and p = 0.522, respectively). Cross-clamp and CPB times were shorter in the No-Balloon group (49.6 ± 15.9 min versus 61.1 ± 25.6 min and 64.1 ± 26.3 min versus 79.6 ± 35.4 min, respectively; p = 0.027 and p = 0.012, respectively). CONCLUSIONS: The two groups had similar postoperative PPI rates. Implanting the Perceval prosthesis without balloon inflation is safe and had no impact on paravalvular leaks, intraoperative complications or hemodynamic results. Reductions in aortic cross-clamp time and CPB time were observed when the balloon was not used.

Swine Atrioventricular Node Ablation Using Stereotactic Radiosurgery: Methods and In Vivo Feasibility Investigation for Catheter-Free Ablation of Cardiac Arrhythmias.

BACKGROUND: Linear accelerator-based stereotactic radiosurgery delivered to cardiac arrhythmogenic foci could be a promising catheter-free ablation modality. We tested the feasibility of in vivo atrioventricular (AV) node ablation in swine using stereotactic radiosurgery. METHODS AND RESULTS: Five Large White breed swine (weight 40-75 kg; 4 females) were studied. Single-chamber St Jude pacemakers were implanted in each pig. The pigs were placed under general anesthesia, and coronary/cardiac computed tomography simulation scans were performed to localize the AV node. Cone beam computed tomography was used for target positioning. Stereotactic radiosurgery doses ranging from 35 to 40 Gy were delivered by a linear accelerator to the AV node, and the pigs were followed up with weekly pacemaker interrogations to observe for potential electrocardiographic changes. Once changes were observed, the pigs were euthanized, and pathology specimens of various tissues, including the AV node and tissues surrounding the AV node, were taken to study the effects of radiation. All 5 pigs had disturbances of AV conduction with progressive transition into complete heart block. Macroscopic inspection did not reveal damage to the myocardium, and pigs had preserved systolic function on echocardiography. Immunostaining revealed fibrosis in the target region of the AV node, whereas no fibrosis was detected in the nontargeted regions. CONCLUSIONS: Catheter-free radioablation using linear accelerator-based stereotactic radiosurgery is feasible in an intact swine model.

AAV-mediated conversion of human pluripotent stem cell-derived pacemaker.

Malfunction of nodal pacemaker (Pm) cardiomyocytes (CMs) due to diseases or aging leads to rhythm generation disorders, necessitating electronic Pm implantation. We functionally reprogrammed human pluripotent stem cell (hPSC) derived-ventricular (V) CMs into -PmCMs via recombinant adeno-associated virus serotype 9 (rAAV9)-mediated overexpression of engineered HCN1 channel (HCN1ΔΔΔ) whose S3-S4 linker has been strategically deleted by design to promote cardiac pacemaking. rAAV9-HCN1ΔΔΔ-reprogrammed hPSC-PmCMs converted from -VCMs showed automaticity and action potential parameters typical of native nodal PmCMs. Implantation of rAAV9-HCN1ΔΔΔ-based BPm in a preclinical porcine model of complete heart block significantly reduced the dependence on device-supported pacing and generated spontaneous heart rhythms from the BPm. Collectively, these results have further laid the groundwork on BPm for future translation.

Use of adenosine to shorten the post ablation waiting period for cavotricuspid isthmus-dependent atrial flutter.

BACKGROUND: Dormant conduction unmasked by adenosine predicts clinical recurrences of cavotricuspid isthmus (CTI) dependent atrial flutter following catheter ablation. Conventional practice involves a waiting period of 20 to 30 minutes after achievement of a bidirectional line of block (BDB) to monitor for recovery of conduction. OBJECTIVE: Assess whether abolition of dormant conduction with adenosine immediately after CTI ablation and BDB can predict the lack of CTI conduction recovery during the following 30 minutes. METHODS: Consecutive patients undergoing catheter ablation for CTI-dependent atrial flutter were studied. Following the completion of CTI ablation and documentation of BDB, adenosine (≥12 mg IV) was administered immediately. In cases of dormant conduction, the CTI was ablated again until its abolition. After the achievement of BDB without dormant conduction, spontaneous CTI reconnection during the following 30 minutes and dormant conduction with adenosine at 30 minutes were evaluated. RESULTS: A CTI block was achieved in 171 patients. Nine patients (5.3%) had dormant conduction across the CTI immediately after ablation and BDB, and required further ablation. Two patients (1.2%) had subsequent spontaneous time-dependent reconnection within 30 minutes. Two other patients (1.2%) developed late dormant conduction with adenosine at 30 minutes. All 4 patients underwent further ablation. CONCLUSION: A negative adenosine challenge immediately after CTI ablation with bidirectional block, or after abolition of dormant conduction with further ablation, strongly predicted the absence of subsequent spontaneous reconnection within 30 minutes. Based on these results, the conventional waiting period is unnecessary in 97.6% patients without dormant conduction after CTI-dependent flutter ablation.

A single center's experience with pacemaker implantation after the Cox maze procedure for atrial fibrillation.

OBJECTIVE: The Cox maze procedure (CM) is safe and effective for all atrial fibrillation (AF) types. A recent randomized trial found alarming rates of pacemaker implantation (PMI) during hospitalization after CM. The purpose of this study was to assess the rate of PMI and its impact on outcomes after CM. METHODS: Incidence of PMI was captured for all CM patients (2005-2015; N = 739). Data were collected prospectively. Multivariable logistic regression was conducted to determine risk factors for PMI. Propensity score matching was conducted between concomitant CM patients and patients without surgical ablation since 2011. RESULTS: Fifty-two patients (7.0%) had in-hospital PMI after CM. Most common primary indication for PMI was sick sinus syndrome (67%), followed by complete heart block (23%) and sinus bradycardia (10%). The only risk factor for in-hospital PMI was type of procedure (P = .020). Patients with multiple valve procedures were at greatest risk (P = .004-.035). STS-defined perioperative outcomes were similar for patients with and without in-hospital PMI. Sinus rhythm off antiarrhythmic drugs were similar by PMI. After propensity score matching (n = 180 per group), in-hospital PMI was similar in CM patients and those without surgical ablation (5% vs 4%, P = .609). CONCLUSIONS: This study demonstrated lower incidence of PMI after CM procedures than recently reported. When indicated, PMI was not associated with increased short- or long-term morbidity or inferior freedom from atrial arrhythmia. Efforts to increase surgeon training with the CM procedure and postoperative management awareness are warranted to improve rhythm outcome and minimize adverse events and PMI.

A complete heart block in a young male: a case report and review of literature of cardiac sarcoidosis.

Cardiac sarcoidosis is one of the uncommon causes of heart failure. Generally, it presents in the form of varying clinical manifestations ranging from asymptomatic to fatal arrhythmias such as ventricular tachycardia and complete heart block. It is difficult to make a diagnosis strictly based on clinical grounds. However, in the setting of extracardiac sarcoidosis and patients presenting with advanced heart block or ventricular arrhythmia, direct cardiac involvement should be suspected. The definitive diagnosis of cardiac sarcoidosis can be made from endomyocardial biopsy, but it is falling out of favor due to patchy myocardial involvement, considerable procedure-related risks, and advancement in additional imaging modalities. Once cardiac sarcoidosis has been diagnosed, management of the disease remains challenging. Steroids are considered the mainstay of therapy, and implantable cardioverter defibrillator therapy can be considered in a selected group of patients at greater risk for malignant ventricular arrhythmias.

Possible complication of bee stings and a review of the cardiac effects of bee stings.

We report the case of a patient who, ∼3 weeks after multiple bee stings, developed a prolonged heart block, syncope and cardiac arrest. This required a temporary pacemaker to be implanted, which was later replaced with a permanent pacemaker. An ECG taken following surgery for a fractured humerus 6 years earlier was reportedly normal. The patient had been a rubber tapper who walked ∼1.5 km/day, but after the bee attack he was no longer able to walk or get up from the bed without experiencing syncope. We presume that the bee venom caused these signs, as well as the resulting heart block, which persisted long after the bee sting had subsided. Since his coronary angiogram was normal we believe he had a Kounis type involvement of the cardiovascular system, namely profound coronary spasm that caused complete heart block that did not recover. Another probable reason for the complete heart block could have been that the bees had consumed the pollen of a rhododendron flower, causing 'grayanotoxin' poisoning and severe heart block. The other effects of bee sting are discussed briefly.