Safety and feasibility of left bundle branch area pacing following valvular interventions: Multicenter study.

OBJECTIVES: To evaluate the safety and feasibility of left bundle branch area pacing (LBBAP) in patients with valvular interventions. METHODS: Eighty-four patients were included in this study. All patients underwent recent surgical or percutaneous valvular interventions. LBBAP was attempted in all patients. Implant success rates, peri- and postprocedure electrocardiogram, pacing parameters, and complications were assessed at implant, and during follow-up. RESULTS: LBBAP implantation was successful in 80/84 (95%) patients. Mean age was 74.1 ± 13.8 years and 56% patients were male. Prior valvular replacements included: percutaneous aortic (26), surgical aortic (36), combined surgical aortic plus mitral (6), MVR (10), tricuspid (1), and pulmonic (1). Average LVEF was 52.6 ± 11%. Majority of patients underwent LBBAP due to atrioventricular block (76%) and sinus node disease (13%). Total procedure duration was 74.1 ± 12.5 min and fluoroscopic duration was 9.7 ± 6.8 min. Pacing parameters were stable during follow-up period of 10.0 ± 6.3 months. Pacing QRS duration was significantly narrower than baseline QRS duration (131.5 ± 31.4 ms vs. 114.3 ± 13.7 ms, p < .001, respectively). No acute complications were observed. Mean follow-up was 10.0 ± 6.3 months (median: 8.4 months, min: 1 and max: 24 months). During follow-up, there were three device infections and two patients had loss of LBBA capture within 1 month of implant. CONCLUSIONS: LBBAP is a feasible and safe pacing modality in patients with prior interventions for valvular heart disease.

Electrocardiographic characteristics and ablation of ventricular arrhythmias originating from the basal inferoseptal area.

AIMS: Ventricular arrhythmias (VAs) from the basal inferoseptal (BIS) area are rare and can pose unique challenges during catheter ablation (CA) due to the anatomic complexity. The study sought to describe the electrocardiographic and clinical characteristics of VAs originating from the BIS area. METHODS AND RESULTS: Patients with VAs and successful ablation at the BIS area from 2016 to 2020 were included. The 12-lead electrocardiogram (ECG), intracardiac findings, and outcomes were analysed. Of 482 patients with VAs referred for CA, 17 (3.5%) had successful ablation at BIS area. There were 12 males, mean age was 66.7 ± 9 years, 82% had ejection fraction <50%. Mean baseline premature ventricular complex burden was 28.6 ± 9%. All patients had a leftward superior axis. Left bundle branch block (LBBB) with early transition in V2 was noted in eight patients and right bundle branch block (RBBB) in nine patients. Detailed mapping of the right ventricle (RV) was performed in 15 patients (88%), coronary sinus (CS)/middle cardiac vein (MCV) in 13 (76%), right atrium (RA) adjacent to the inferoseptal process (ISP) of left ventricle (LV) in 5 (29%), ISP-LV in 13 (76%), and epicardium in 2 (12%). Successful ablation site was in LV in 10 (59%), RV in 2 (12%), CS/MCV in 1 (6%), RA in 1 (6%), and epicardium in 2 (12%). Fifteen patients (88%) required mapping in at least two chambers (range 2-5) and seven patients (41%) required ablation in at least two chambers (range 2-3). CONCLUSIONS: Ventricular arrhythmias originating in the BIS are uncommon. The most common ECG patterns were leftward superior axis, LBBB with transition in V2 or RBBB. The VA foci can be endocardial or epicardial and meticulous mapping/ablation from multiple chambers is often required to eliminate these foci successfully.

Anatomy of the cardiac conduction system.

The specialized cardiomyocytes that constitute the conduction system in the human heart, initiate the electric impulse and result in rhythmic and synchronized contraction of the atria and ventricles. Although the atrioventricular (AV) conduction axis was described more than a century ago by Sunao Tawara, the anatomic pathway for propagation of impulse from atria to the ventricles has been a topic of debate for years. Over the past 2 decades, there has been a resurgence of conduction system pacing (CSP) by implanting pacing leads in the His bundle region in lieu of chronic right ventricular pacing that is associated with worse clinical outcomes. The inherent limitations of implanting the leads in the His bundle region has led to the emergence of left bundle branch area pacing in the past 3 years as an alternative strategy for CSP. The clinical experience from performing CSP has helped electrophysiologists gain deeper insight into the anatomy and physiology of cardiac conduction system. This review details the anatomy of the cardiac conduction system, and highlights some of the recently published articles that aid in better understanding of the AV conduction axis and its variations, the knowledge of which is critical for CSP. The remarkable evolution in technology has led to visualization of the cardiac conduction system using noninvasive, nondestructive high-resolution contrast-enhanced micro-computed tomography imaging that may aid in future CSP. We also discuss from anatomical perspective, the differences seen clinically with His bundle pacing and left bundle branch area pacing.

Spectrum of arrhythmogenic substrate post minimally invasive maze surgery in patients with recurrent.

BACKGROUND: Advancements in minimally invasive surgical ablation (MISA) have focused on improving pulmonary vein isolation. Additional ablation targets have been developed (such as posterior wall isolation). The mid- and long-term effects of current techniques (including electrophysiologic findings and recurrent arrhythmia mechanisms) have not previously been reported. METHODS: Twenty eight patients with recurrent atrial arrhythmias after bipolar clamp ablation of the pulmonary vein antrum, ganglionated plexi, posterior wall isolation (roof and floor lines to create a posterior box), and ligament of Marshall ligation/cauterization and left atrial appendage clipping underwent follow up electrophysiology study including left atrial mapping an average of 2.3 years postoperatively. RESULTS: Atrial fibrillation was the most common recurrent arrhythmia (n = 18) followed by micro-reentrant atrial tachycardia (n = 5), macro-reentry left atrial flutter (n = 3), and typical cavo-tricuspid isthmus atrial flutter (n = 2). Eighty six of 112 (77%) PVs mapped were electrically isolated, 16 (57%) patients had all four pulmonary veins (PVs) isolated. The posterior wall (PW) was completely isolated in only four (14%) patients, seven (25%) patients had normal PW voltage, while 17 (61%) patients had abnormal delayed or fractionated electrograms in the posterior wall (incomplete isolation). Abnormal PW electrograms were more frequently found in patients with complex recurrent left atrial arrhythmia (micro-reentry or left atrial macro-reentry flutter). CONCLUSION: With current surgical techniques PV isolation has improved, but PW isolation remains challenging. Incomplete PW isolation may produce arrhythmogenic substrate.

Impact of His bundle pacing on right ventricular performance in patients undergoing permanent pacemaker implantation.

BACKGROUND: His-Bundle pacing (HBP) is an emerging technique for physiological pacing. However, its effects on right ventricle (RV) performance are still unknown. METHODS: We enrolled consecutive patients with an indication for pacemaker (PM) implantation to compare HBP versus RV pacing (RVP) effects on RV performance. Patients were evaluated before implantation and after 6 months by a transthoracic echocardiogram. RESULTS: A total of 84 patients (age 75.1±7.9 years, 64% male) were enrolled, 42 patients (50%) underwent successful HBP, and 42 patients (50%) apical RVP. At follow up, we found a significant improvement in RV-FAC (Fractional Area Change)% [baseline: HBP 34 IQR (31-37) vs. RVP 33 IQR (29.7-37.2),p = .602; 6-months: HBP 37 IQR (33-39) vs. RVP 30 IQR (27.7-35), p < .0001] and RV-GLS (Global Longitudinal Strain)% [baseline: HBP -18 IQR (-20.2 to -15) vs. RVP -16 IQR (-18.7 to -14), p = .150; 6-months: HBP -20 IQR(-23 to -17) vs. RVP -13.5 IQR (-16 to -11), p < .0001] with HBP whereas RVP was associated with a significant decline in both parameters. RVP was also associated with a significant worsening of tricuspid annular plane systolic excursion (TAPSE) (p < .0001) and S wave velocity (p < .0001) at follow up. Conversely from RVP, HBP significantly improved pulmonary artery systolic pressure (PASP) [baseline: HBP 38 IQR (32-42) mmHg vs. RVP 34 IQR (31.5-37) mmHg,p = .060; 6-months: HBP 32 IQR (26-38) mmHg vs. RVP 39 IQR (36-41) mmHg, p < .0001] and tricuspid regurgitation (p = .005) irrespectively from lead position above or below the tricuspid valve. CONCLUSIONS: In patients undergoing PM implantation, HBP ensues a beneficial and protective impact on RV performance compared with RVP.

Electrocardiographic changes in loperamide toxicity: Case report and review of literature.

INTRODUCTION: Loperamide, an antidiarrheal agent, is a µ-opioid receptor agonist increasingly abused to prevent opioid withdrawal or to produce euphoric effects. At supra-therapeutic doses, loperamide can cause cardiac toxicity due to blockade of Na and IKr channels, resulting in wide QRS rhythms, severe bradycardia, prolonged QTc, polymorphic ventricular tachycardia, cardiac arrest, and death. There are limited data on the cardiotoxic effects of high dose loperamide. METHODS AND RESULTS: A case report of loperamide toxicity is presented and then added to a contemporary review of the literature. In total, the presentation and management of 36 cases of loperamide cardiotoxicity are summarized. The overall median daily dose (interquartile range) of loperamide was 200 (134-400) mg. The median QRS duration was 160 (125-170) ms. The median QTc duration was 620 (565-701) ms. Ventricular tachycardia was experienced by 24/36 (67%) of patients, 20 of which were specified to be polymorphic. Treatment was supportive, providing advanced cardiopulmonary life support and aggressive electrolyte repletion. Isoproterenol infusion or overdrive pacing was employed in 19/36 (53%) of cases. The median time to electrocardiogram normalization or hospital discharge, whichever came first, was 5 (3.5-10) days. CONCLUSION: Loperamide overdose is a toxidrome that remains underrecognized, and in patients with unexplained cardiac arrhythmias, loperamide toxicity should be suspected. Prompt recognition is critical due to the delayed recovery and high risk for life-threatening arrhythmias.

A risk score model for predicting intraprocedural cardiac injury during implantable cardioverter defibrillator implantation: Insights from the National Cardiovascular Data Registry.

BACKGROUND: Individual risk factors of intraprocedural cardiac injury (cardiac perforation and tamponade) during implantable cardioverter defibrillator (ICD) placement have been documented. However, the prognostic impact of their coexistence has not been explored. OBJECTIVE: To develop a risk score model to identify patients at risk for intraprocedural cardiac injury. METHODS: We identified 438 679 patients from National Cardiovascular Data Registry (NCDR)-ICD who underwent de novo ICD implantation between 2010 and 2015, split randomly into a derivation cohort (n = 220 000) and a validation cohort (n = 218 679). The generalized estimating equations (GEEs) analysis with quasilikelihood under the independence model criterion goodness-of-fit statistics were used to identify the predictors of intraprocedural cardiac injury and a risk scoring model was developed. Model discrimination was assessed by receiver-operator characteristic curve and C-statistic. RESULTS: The risk of intraprocedural cardiac injury in the overall cohort was 0.13%. GEE analysis yielded seven variables (points in parentheses) that were strongly associated with intraprocedural cardiac injury: age, greater than 75 years (1), female gender (1), body mass index, less than 18.5 kg/m 2 (1), hypertension (1), chronic lung disease (1), left bundle branch block (1), and continued warfarin use (1). Only prior history of coronary artery bypass grafting (CABG) (-1) was associated with reduced risk. A risk scoring system was developed that had good discrimination with a C-statistic of 0.72. The risk of intraprocedural cardiac injury increased with the increase in risk score from low risk (0.03%) to high risk (1.37%). CONCLUSION: A practical risk score model can stratify patients into high- and low-risk groups for cardiac perforation or tamponade before undergoing ICD implantation.

Risk score model for predicting complications in patients undergoing ventricular tachycardia ablation: insights from the National Inpatient Sample database.

AIMS: Outcome data on ventricular tachycardia (VT) ablation has been limited to few experienced centres. We sought to identify complication rates, predictors, and create a risk score model for predicting complications in patients from real-world data. METHODS AND RESULTS: A total of 25 451 patients undergoing VT ablation from year 2006 to 2013 were identified from the National Inpatient Sample (NIS) database. The whole cohort was randomly divided into derivation cohort to derive the model and validation cohort to validate the model. Multivariate predictors of any complication were identified using regression model. Each predictor was assigned a risk score and each patient was assigned to one of the four groups (risk score in parenthesis) based on total combined risk score: Group 0 (0), Group 1 (1-5), Group 2 (6-10), and Group 3 (>11). The rate of 'any complication' and 'in-hospital mortality' in whole cohort was 14.7% and 2.8%, respectively. The predictors of any complication include chronic kidney disease, coagulopathy, chronic liver disease, stroke (cerebrovascular accident), emergency procedure, age ≥ 65 years, coronary artery disease, peripheral vascular disease, and female gender. There was a significant increase in complication rate in a linear fashion as the risk score increased. The incidence of any complications increased from 2.7% in Group 0 to 31% in Group 3. The risk score model performed well in predicting complications associated with VT ablation. CONCLUSION: Patients with higher risk scores have significant increase in any complication and in-hospital mortality from VT ablation. The simple risk score model can help to risk stratify patients prior to VT ablation.

Stellate ganglion blockade and bilateral cardiac sympathetic denervation in patients with life-threatening ventricular arrhythmias.

Autonomic modulation is being increasingly employed as a strategy to treat ventricular arrhythmias refractory to beta-blockers, antiarrhythmic drugs, and catheter-based ablation procedures. We report 6 patients with refractory ventricular tachycardia (VT) or ventricular fibrillation (VF) treated with stellate ganglion blockade (SGB) and/or bilateral cardiac sympathetic denervation (CSD). Our case series emphasizes the concept that the cardiac sympathetic nerves are important targets in the management of ventricular arrhythmias. SGB and CSD can be effective in suppressing VT/VF and can be offered to patients with refractory ventricular arrhythmias as an adjunct to conventional therapy.

Vascular Complications During Catheter Ablation of Cardiac Arrhythmias: A Comparison Between Vascular Ultrasound Guided Access and Conventional Vascular Access.

INTRODUCTION: Vascular access related complications are the most common complications from catheter based EP procedures and have been reported to occur in 1-13% of cases. We prospectively assessed vascular complications in a large series of consecutive patients undergoing catheter based electrophysiologic (EP) procedures with ultrasound (US) guided vascular access versus conventional access. METHODS AND RESULTS: Consecutive patients undergoing catheter ablation procedures at VCU medical center were included. US guided access was obtained in all cases starting June 2015 (US group) while modified Seldinger technique without US guidance (non-US group) was used in cases prior to this date. All vascular complications were recorded for a 30-day period after the procedure. A total of 689 patients underwent 720 procedures. Ablations for ventricular tachyarrhythmias (ventricular tachycardia: VT, premature ventricular contractions: PVCs) accounted for 89 (12%) cases; atrial fibrillation (AF) ablations accounted for 328 procedures (46%) and other catheter based procedures accounted for 42% of cases. A significantly higher incidence of complications was noted in the non-US group compared with the US group (19 [5.3%] vs. 4 [1.1%], respectively, P = 0.002). Major complications were also higher among the non-US group (9 [2.5%] vs. 2 [0.6%], P = 0.03). Increasing age (P = 0.04) and non-US guided vascular access (P = 0.002) were associated with a higher risk of vascular access complications. CONCLUSION: In a large series of patients undergoing catheter based EP procedures for cardiac arrhythmias, US guided vascular access was associated with a significantly decreased 30-day risk of vascular complications.

Factors Influencing Diaphragmatic Compound Motor Action Potentials During Cryoballoon Ablation for Atrial Fibrillation.

INTRODUCTION: The diaphragmatic compound motor action potentials (CMAPs) have been used to predict and prevent phrenic nerve injury (PNI) during cryoballoon ablation of right pulmonary veins. We sought to assess factors that influence the amplitude of the surface CMAP recordings. METHODS AND RESULTS: We analyzed CMAPs from consecutive patients undergoing cryoballoon ablation for paroxysmal atrial fibrillation. CMAP recordings were obtained using electrocardiography electrodes positioned in the "modified lead I" method while stimulating the right PN, until loss of capture (ascertained by palpation and fluoroscopy of the right hemi-diaphragm). A total of 55 patients (age 63 ± 11 years; 60% men; body mass index [BMI] 31 ± 6) had adequate CMAP recordings and were included for evaluation of CMAP signals. CMAPs demonstrated 2 distinct components, an early higher amplitude signal (pacing artifact) and a later lower amplitude signal (true diaphragmatic CMAP). There was no significant change in the true CMAP recording amplitude with decrease in stimulus strength (P = 0.1). There was no impact of BMI on CMAP amplitude (P = 0.93). There was a significant phasic respiratory variation in CMAP amplitude with a mean decrease in CMAP amplitude of 10.8% (range: 8-12%) with inspiration lasting an average of 2 beats (P < 0.001). A decrease in CMAP amplitude of >30% was noted in 6 cases (11%) and termination of cryoablation prevented PNI. CONCLUSION: Diaphragmatic CMAP amplitude is not affected by stimulus strength or BMI. There is a significant respirophasic decrease in CMAP signal amplitude with inspiration. It is important to be aware of this variation to avoid premature termination of cryoablation.

Non-sustained wide complex tachycardia: an underappreciated sign to aid in diagnosis.

AIMS: The electrocardiographic (ECG) signs used to differentiate ventricular tachycardia (VT) from supraventricular tachycardia (SVT) with aberrancy are specific but not highly sensitive. The purpose of this study was to define the utility of an underappreciated form of atrioventricular (AV) dissociation at the onset of tachycardia, a single dissociated P wave, in the differentiation of non-sustained monomorphic wide complex tachycardia (WCT) in hospitalized patients. METHODS AND RESULTS: We prospectively analysed tracings from 102 consecutive hospitalized patients who had an episode of non-sustained (≥5 beats, <30 s), monomorphic, WCT (≥100 b.p.m.) on telemetry. WCT was classified as VT, SVT with aberrancy, or undifferentiated WCT based on predefined criteria. Of 102 patients with WCT, 3 (3%) had SVT with aberrancy, 43 (42%) had an undifferentiated WCT, and 56 (55%) had VT. ECG evidence of a single dissociated P wave at the onset of tachycardia (i.e. AV dissociation at the onset) was identified in 29 patients (28%) compared with less frequent traditional signs of VT including second-degree ventriculoatrial (VA) block in 18 patients (18%), AV dissociation during tachycardia in 17 patients (17%), fusion beats in 10 patients (10%), and capture beats in 3 patients (3%). On multivariate analysis, only the prematurity index predicted the occurrence of AV dissociation at the onset of the tachycardia (odds ratio 1.239, 95% confidence interval 1.033-1.486, P = 0.021). CONCLUSION: When evaluating WCT in hospitalized patients, a single dissociated P wave at the onset of tachycardia is an easily recognizable diagnostic sign of VT, and is observed more frequently than the other accepted criteria for VT.

Lyme Carditis in the Fast Lane: From Alternating Bundle Branch Block to Asystole in 12 Hours.

Lyme borreliosis is a multisystem infectious disease with well-known cardiac involvement, including potential carditis as well as conduction abnormalities. We report a case of Lyme disease in a previously healthy 24-year-old male presenting with alternating right- and left-bundle branch block, indicating infra-Hisian atrioventricular (infra-His) block with an accelerated fascicular escape rhythm. Inless than 12 hours, the conduction abnormalities progressed to asystole requiring the urgent placement of a temporary transvenous pacemaker. Subsequently, with appropriate antibiotic treatment, the patient's conduction abnormalities resolved in a week without the need for a permanent pacemaker.

Cardiovascular risk stratification in diabetic patients following stress single-photon emission-computed tomography myocardial perfusion imaging: the impact of achieved exercise level.

BACKGROUND: Previous studies have demonstrated that diabetic patients undergoing exercise stress single-photon emission-computed tomography (SPECT) myocardial perfusion imaging (MPI) have significantly lower cardiac events when compared to the diabetic patients undergoing pharmacologic stress SPECT MPI across all perfusion categories. However, there are limited data on the level of exercise achieved during exercise SPECT MPI among diabetic patients and its impact on cardiovascular outcomes. METHODS: We retrospectively analyzed 14,849 consecutive patients (3,654 diabetics and 11,195 non-diabetics) undergoing exercise stress, combined exercise and pharmacologic stress, and pharmacologic stress SPECT MPI from 1996 to 2005 at a single tertiary care center. Diabetic and non-diabetic patients were categorized into 3 groups based on the metabolic equivalents (METs) achieved: ≥5 METs, <5 METs, and pharmacologic stress groups. All studies were interpreted using the 17-segment ASNC model. The presence, extent, severity of perfusion defects were calculated using the summed stress score (SSS), and patients were classified into normal (SSS < 4), mildly abnormal (SSS 4-8), and moderate-severely abnormal (SSS > 8) categories. Annualized event rates (AER) for the composite end point of non-fatal myocardial infarction and cardiac death were calculated over a mean follow-up period of 2.4 ± 1.4 years with a maximum of 6 years. RESULTS: In moderate-severe perfusion abnormality (SSS > 8) category, diabetic patients who were able to achieve ≥5 METs had significantly lower AER compared to diabetic patients who were unable to achieve ≥5 METs (3% vs 5.5%, P = .04), and non-diabetic patients unable to achieve ≥5 METs (3% vs 4.8%, P < .001). Diabetic patients who achieved a high workload of ≥10 METs had a very low AER of 0.9%. Diabetic patients, who attempted exercise but were unable to achieve ≥5 METs, still had significantly lower AER than diabetics undergoing pharmacologic stress MPI across all perfusion categories [1.5% vs 3.2%, P = .006 (SSS < 4); 2.5% vs 4.9%, P = .032 (SSS 4-8); 5.5% vs 10.3%, P = .003 (SSS > 8)]. After adjustment for cardiovascular risk factors, the percentage decrease in cardiac event rate for every 1-MET increment in exercise capacity was 10% in the overall cohort, 12% in diabetic group, and 8% in non-diabetic group. CONCLUSIONS: Despite significant perfusion defects, diabetic patients who achieve ≥5 METs during stress SPECT MPI have significantly reduced risk for future cardiac events. Diabetic patients who achieve ≥10 METs have a very low annualized event rate. These findings support that exercise capacity obtained during SPECT MPI is a surrogate for outcomes among diabetic patients undergoing nuclear stress testing.

Transient high-grade atrioventricular block in an orthotopic cardiac transplant recipient.

A 56-year-old male with a history of orthotopic cardiac transplantation secondary to cardiac sarcoidosis presented with recurrent episodes of syncope preceded by dizziness. While on telemetry, he had transient episodes of high-grade atrioventricular (AV) block that reproduced his prodrome. After excluding allograft rejection, ischemia, recurrent cardiac sarcoidosis, and vagally mediated block as a cause of high-grade AV block, adenosine testing was done which reproduced the spontaneous high-grade AV block. We concluded that hypersensitivity to endogenously released adenosine was the likely mechanism of AV block in our patient. This is the first reported case of adenosine testing in a cardiac transplant patient for diagnosing episodic high-degree AV block of unclear etiology.