Conduction system pacing: how far are we from the "electrical" bypass?

Conduction system pacing is an alternative practice to conventional right ventricular apical pacing. It is a method that maintains physiologic ventricular activation, based on a correct pathophysiological basis, in which the pacing lead bypasses the lesion of the electrical fibers and the electrical impulse transmits through the intact adjacent conduction system. For this reason, it might be reasonably characterized by the term "electrical bypass" compared to the coronary artery bypass in revascularization therapy. In this review, reference is made to the sequence of events in which conventional right ventricular pacing may cause adverse outcomes. Furthermore, there is a reference to alternative strategies and pacing sites. Interest focuses on the modalities for which there are data from the literature, namely for the right ventricular (RV) septal pacing, the His bundle pacing (HBP), and the left bundle branch pacing (LBBP). A more extensive reference is about the HBP, for which there are the most updated data. We analyze the considerations that limit HBP-wide application in three axes, and we also present the data for the implantation and follow-up of these patients. The indications with their most important studies to date are then described in detail, not only in their undoubtedly positive findings but also in their weak aspects, because of which this pacing mode has not yet received a strong recommendation for implementation. Finally, there is a report on LBBP, focusing mainly on its points of differentiation from HBP.

Analysis of the effect of cortisone on the QT interval.

BACKGROUND: Cardiac death caused by malignant arrhythmias is very prevalent. Prolongation of the QT interval is a relevant aspect in arrhythmia mechanisms. Prior studies have revealed that the QTc interval could be shortened by cortisone. Moreover, in an animal model of long QT syndrome, cortisone treatment shortens the ventricular action potential duration. The present study investigated the effect of methylprednisolone (MPS) on the QTc interval in cardiovascularly healthy humans. METHODS: Patients who had just been diagnosed with multiple sclerosis receiving MPS therapy were analysed prospectively. Demographic data, laboratory values, anti-arrhythmic medication and baseline and follow-up ECGs were extracted from the patients' medical records. RESULTS: Seventy-eight patients were included. The mean ± standard deviation age was 47 ± 15 years. The values of the electrolytes were normal. All patients were treated with MPS for 3 or 5 days. The heart rate increased at the beginning of MPS therapy and decreased during the subsequent period. ECG measurements showed that the QTc interval was prolonged at the beginning of MPS therapy and shortened over the course of treatment. The longest QTc intervals were obtained by calculation with Bazett's formula. CONCLUSIONS: In humans, cortisone shortens the QTc interval over time. The analysis indicates a cumulative effect of cortisone that lasts longer. The results of our pilot study reveal that cortisone might be added to therapeutic strategies in patients with long QT syndromes. Further clinical studies have to be carried out to analyze potential clinical options.

Electrocardiogram in patients with pulmonary hypertension.

INTRODUCTION: Pulmonary hypertension (PH) is a potentially life-threatening cardiovascular disease defined by a mean pulmonary arterial pressure (mPAP) > 20 mmHg. Due to non-specific symptoms, PH is often diagnosed late and at advanced stage. In addition to other diagnostic modalities, the electrocardiogram (ECG) can help in establishing the diagnosis. Knowledge of typical ECG signs could help to detect PH earlier. METHODS: A non-systematic literature review on the typical electrocardiographic patterns of PH was performed. RESULTS: Characteristic signs of PH include right axis deviation, SIQIIITIII and SISIISIII patterns, P pulmonale, right bundle branch block, deep R waves in V1 and V2, deep S waves in V5 and V6, and right ventricular hypertrophy (R in V1 + S in V5, V6 > 1,05 mV). Repolarisation abnormalities such as ST segment depressions or T wave inversions in leads II, III, aVF, and V1 to V3 are common as well. Furthermore, a prolonged QT/QTc interval, an increased heart rate, or supraventricular tachyarrhythmias can be observed. Some parameters may even provide information about the patient's prognosis. CONCLUSION: Not every PH patient shows electrocardiographic PH signs, especially in mild PH. Thus, the ECG is not useful to completely rule out PH, but provides important clues to PH when symptoms are present. The combination of typical ECG signs and the co-occurrence of electrocardiographic signs with clinical symptoms and elevated BNP levels are particularly suspicious. Diagnosing PH earlier could prevent further right heart strain and improve patient prognosis.

Preventive or Deferred Ablation of Ventricular Tachycardia in Patients With Ischemic Cardiomyopathy and Implantable Defibrillator (BERLIN VT): A Multicenter Randomized Trial.

BACKGROUND: Catheter ablation for ventricular tachycardia (VT) reduces the recurrence of VT in patients with implantable cardioverter-defibrillators (ICDs). The appropriate timing of VT ablation and its effects on mortality and heart failure progression remain a matter of debate. In patients with life-threatening arrhythmias necessitating ICD implantation, we compared outcomes of preventive VT ablation (undertaken before ICD implantation to prevent ICD shocks for VT) and deferred ablation after 3 ICD shocks for VT. METHODS: The BERLIN VT study (Preventive Ablation of Ventricular Tachycardia in Patients With Myocardial Infarction) was a prospective, open, parallel, randomized trial performed at 26 centers. Patients with stable ischemic cardiomyopathy, a left ventricular ejection fraction between 30% and 50%, and documented VT were randomly assigned 1:1 to a preventive or deferred ablation strategy. The primary outcome was a composite of all-cause death and unplanned hospitalization for either symptomatic ventricular arrhythmia or worsening heart failure. Secondary outcomes included sustained ventricular tachyarrhythmia and appropriate ICD therapy. We hypothesized that preventive ablation strategy would be superior to deferred ablation strategy in the intention-to-treat population. RESULTS: During a mean follow-up of 396±284 days, the primary end point occurred in 25 (32.9%) of 76 patients in the preventive ablation group and 23 (27.7%) of 83 patients in the deferred ablation group (hazard ratio, 1.09 [95% CI, 0.62-1.92]; P=0.77). On the basis of prespecified criteria for interim analyses, the study was terminated early for futility. In the preventive versus deferred ablation group, 6 versus 2 patients died (7.9% versus 2.4%; P=0.18), 8 versus 2 patients were admitted for worsening heart failure (10.4% versus 2.3%; P=0.062), and 15 versus 21 patients were hospitalized for symptomatic ventricular arrhythmia (19.5% versus 25.3%; P=0.27). Among secondary outcomes, the proportions of patients with sustained ventricular tachyarrhythmia (39.7% versus 48.2%; P=0.050) and appropriate ICD therapy (34.2% versus 47.0%; P=0.020) were numerically reduced in the preventive ablation group. CONCLUSIONS: Preventive VT ablation before ICD implantation did not reduce mortality or hospitalization for arrhythmia or worsening heart failure during 1 year of follow-up compared with the deferred ablation strategy. Registration: URL: https://www.clinicaltrials.gov; Unique identifier: NCT02501005.

Improvement of electrical synchrony in cardiac resynchronization therapy using dynamic atrioventricular delay programming and multipoint pacing.

BACKGROUND: Optimization of cardiac resynchronization therapy (CRT) is often time-consuming and therefore underused in a clinical setting. Novel device-based algorithms aiming to simplify optimization include a dynamic atrioventricular delay (AVD) algorithm (SyncAV, Abbott) and multipoint pacing (MPP, Abbott). This study examines the acute effect of SyncAV and MPP on electrical synchrony in patients with newly and chronically implanted CRT devices. METHODS: Patients with SyncAV and MPP enabled devices were prospectively enrolled during implant or scheduled follow-up. Blinded 12-lead electrocardiographic acute measurements of QRS duration (QRSd) were performed for intrinsic QRSd (Intrinsic), bi-ventricular pacing (BiV), MPP, BiV with SyncAV at default offset 50 ms (BiVSyncAVdef ), BiV with SyncAV at patient-specific optimised offset (BiVSyncAVopt ), MPP with SyncAV at default offset 50 ms (MPPSyncAVdef ), and MPP with SyncAV at patient-specific optimised offset (MPPSyncAVopt ). RESULTS: Thirty-three patients were enrolled. QRSd for Intrinsic, BiV, MPP, BiVSyncAVdef , BiVSyncAVopt , MPPSyncAVdef , MPPSyncAVopt were 160.4 ± 20.6 ms, 141.0 ± 20.5 ms, 130.2 ± 17.2 ms, 121.7 ± 20.9 ms, 117.0 ± 19.0 ms, 121.2 ± 17.1 ms, 108.7 ± 16.5 ms respectively. MPPSyncAVopt led to greatest reduction of QRSd relative to Intrinsic (-31.6 ± 11.1%; p < .001), showed significantly shorter QRSd compared to all other pacing configurations (p < .001) and shortest QRSd in every patient. Shortening of QRSd was not significantly different between newly and chronically implanted devices (-51.6 ± 14.7 ms vs. -52.7 ± 21.9 ms; p = .99). CONCLUSION: SyncAV and MPP improved acute electrical synchrony in CRT. Combining both technologies with patient-specific optimization resulted in greatest improvement, regardless of time since implantation. Whats new Novel device-based algorithms like a dynamic AVD algorithm (SyncAV, Abbott) and multipoint pacing (MPP, Abbott) aim to simplify CRT optimization. Our data show that a combination of patient tailored SyncAV optimization and MPP results in greatest improvement of electrical synchrony in CRT measured by QRS duration, regardless if programmed in newly or chronically implanted devices. This is the first study to our knowledge to examine a combination of these device-based algorithms. The results help understanding the ideal ventricular excitation in heart failure.

[Perioprocedural mortality after ICD implantation]. / Peripoperative Mortalität nach ICD-Implantation.

BACKGROUND: Implantable cardioverter defibrillators (ICD) represent an established treatment in preventing sudden cardiac death in patients with indications for primary or secondary prophylaxis. As for all complex surgical procedures there remains a risk for the occurrence of complications including death also for ICD implantation. The aim of the present study was to analyze the procedure-related mortality in patients after ICD implantation using the data from the obligatory quality assurance program in North-Rhine/Westphalia. METHODS: Data of all 18,625 patients from the quality assurance datasets who underwent ICD implantation in the years 2010-2012 were analyzed. RESULTS: During the in-hospital stay 118 patients (0.6%) died after ICD implantation. Patients > 80 years old had a higher mortality (1.9% vs. 0.5% in patients < 80 years old, p < 0.001) as well as women (0.95% vs. 0.54% in men, p = 0.004) and patients with higher New York Heart Association (NYHA) class (0.3% for NYHA II, 0.7% for NYHA III, 3.4% for NYHA IV, p < 0.001 for all comparisons). The presence of diabetes mellitus (23% of the collective) did not influence the perioperative mortality, whereas renal failure requiring dialysis showed a significantly increased mortality (p < 0.001 compared to patients with creatinine ≤ 1.5 mg/dl and p = 0.002 for patients with creatinine > 1.5 mg/dl not requiring dialysis). Patients with indications for ICD secondary prophylaxis had a significantly higher mortality (1.2% vs. 0.4%, p < 0.001), which increased from 0.6% to 3.7% (p < 0.001) with the occurrence of complications. CONCLUSION: The procedure-related mortality after ICD implantation is increased in patients over 80 years of age, higher NYHA class, patients requiring dialysis, in secondary prevention indications and after the occurrence of perioperative complications.

Antiarrhythmic effect of vernakalant in an experimental model of Long-QT-syndrome.

AIMS: The antiarrhythmic drug vernakalant exerts antiarrhythmic effects in atrial fibrillation. Recent experimental data suggest interactions with the late sodium current and antiarrhythmic effects in ventricular arrhythmias. We aimed at investigating whether treatment with vernakalant reduces polymorphic ventricular tachycardia (VT) in an experimental model of Long-QT-syndrome (LQTS). METHODS AND RESULTS: Twenty-nine isolated rabbit hearts were assigned to two groups and treated with erythromycin (300 µM, n = 15) or veratridine (0.5 µM, n = 14) after obtaining baseline data. Thereafter, vernakalant (10 µM) was additionally infused. Infusion of erythromycin or veratridine significantly increased action potential duration (APD90) and QT interval. Erythromycin and veratridine also significantly augmented spatial dispersion of repolarization (erythromycin: +43 ms; veratridine: +55 ms, P < 0.01, respectively) and temporal dispersion of repolarization. After lowering extracellular [K+] in bradycardic hearts, 11 of 15 erythromycin-treated hearts and 4 of 14 veratridine-treated hearts showed early afterdepolarizations and subsequent polymorphic VT. Additional treatment with vernakalant resulted in a significant reduction of spatial dispersion of spatial dispersion in both groups (erythromycin: -32 ms; veratridine: -35 ms, P < 0.05 each) and a stabilization of temporal dispersion. After additional treatment with vernakalant, only 5 of 15 erythromycin-treated hearts (P = 0.07) and 1 of 14 veratridine-treated hearts (P = 0.32) presented polymorphic VT. CONCLUSION: Vernakalant has antiarrhythmic effects in this experimental model of acquired LQTS. A reduction of spatial dispersion of repolarization and a stabilization of temporal dispersion in hearts showing polymorphic VT represent the major underlying electrophysiological mechanisms.

Applicability of a Novel Formula (Bogossian formula) for Evaluation of the QT-Interval in Heart Failure and Left Bundle Branch Block Due to Right Ventricular Pacing.

BACKGROUND: The presence of left bundle branch block (LBBB) due to right ventricular pacing represents a particular challenge in properly measuring the QTc interval. In 2014, a new formula for the evaluation of QT interval in patients with LBBB was reported. METHODS: 145 patients with implantable cardioverter defibrillator were included in this prospective multicenter observational study. Inclusion criteria were: no permanent right ventricular stimulation, an intrinsic QRS interval of <120 ms, and reduced left ventricular function. 12-lead electrocardiogram recordings during intrinsic rhythm and during right ventricular threshold testing were performed. After LBBB correction using the reported Bogossian formula, the QTc interval was evaluated with Bazett's formula. The corrected QTc interval was compared in each patient with the QTc interval during intrinsic rhythm. All measurements were performed by an experienced electrophysiologist and a trainee who worked independently and in a blinded manner. RESULTS: 74 patients (65 ± 13 years; male n = 42) with apical and 71 patients (68 ± 11 years; male n = 42) with nonapical right ventricular pacing were included in this study. The mean left ventricular ejection fraction was 40 ± 13%. The QTc interval was determined to be 461 ± 34 ms (modified by Bogossian's formula) in paced and 436 ± 34 ms in intrinsic rhythm. The QTc interval was overestimated by ΔQTc of 25 ± 21 ms (mean deviation 5.7%) when using the Bogossian formula. CONCLUSION: The novel Bogossian formula seems to be a reliable tool for QTc interval evaluation in patients with heart failure and right ventricular pacing. However, a slight overestimation of the QT-interval must be respected.

A new experimentally validated formula to calculate the QT interval in the presence of left bundle branch block holds true in the clinical setting.

BACKGROUND: The evaluation of the QT interval in the presence of left bundle branch block (LBBB) is associated with the challenge to discriminate native QT interval from the prolongation due to the increase in QRS duration. The newest formula to evaluate QT interval in the presence of LBBB suggests: modified QT during LBBB = measured QT interval minus 50% of LBBB duration. The purpose of this study is therefore to validate the abovementioned formula in the clinical setting. METHODS: Validation in two separate groups of patients: Patients who alternated between narrow QRS and intermittent LBBB and patients with narrow QRS who developed LBBB after transcatheter aortic valve implantation (TAVI). RESULTS: The acquired mean native QTc intervals and those calculated by the presented formula displayed no significant differences (p > .99 and p > .75). CONCLUSIONS: In this study we proved for the first time the validity and applicability of the experimentally acquired formula for the evaluation of the QT interval in the presence of LBBB in a clinical setting.

Insulation failure and externalized conductor of a single-coil Kentrox lead: an ongoing story?

Conductor externalization is a frequent complication with the St. Jude Medical Riata lead. Single case reports also reported externalization of conductors for dual-coil Biotronik leads. Up to now, conductor externalization has not yet been reported for any single coil leads. We report for the first time an externalization of conductors in a Biotronik Kentrox single-coil implantable cardioverter defibrillator (ICD) lead.

Q Wave in the Inferior Leads: There Is More Than Scar.

Q waves can regularly be observed in the 12-lead electrocardiogram either due to heart axis underlying pathology such as subacute myocardial infarction, myocardial scar, or accessory pathways. Rarely, other entities such as circumscribed hypertrophy can induce significant Q wave and represent an important differential diagnosis especially in younger patients. In the setting of atypical chest pain determination of the correct diagnosis can be challenging. Therefore, circumscribed hypertrophy should be taken into account to avoid unnecessary invasive procedures.

U wave during supraventricular tachycardia: simulation of a long RP tachycardia and hiding the common type AVNRT.

The main tool for the differentiation of supraventricular tachycardia is the 12-lead electrocardiogram (ECG). Especially differentiating the atrioventricular nodal reentrant tachycardia (AVNRT) from the atrioventricular reentrant tachycardia (AVRT) due to concealed accessory pathway or from an atrial tachycardia (AT) is very important for catheter setting and ablation approach in an electrophysiological study. In our case we saw the occurrence of a U wave during tachycardia-simulating a pseudo P wave. This mimicked a long RP-tachycardia, although it was a common type AVNRT.

Vernakalant in an experimental model of pacing-induced heart failure: lack of proarrhythmia despite prolongation of repolarization.

BACKGROUND: The present ESC guidelines on atrial fibrillation have introduced vernakalant (VER) for pharmacologic cardioversion of atrial fibrillation. The aim of the present study was to investigate possible proarrhythmic effects of vernakalant in an experimental model of heart failure (HF). METHODS AND RESULTS: In 12 female rabbits, HF was induced with the use of 4 weeks of rapid ventricular pacing. Twelve rabbits were sham operated. Isolated hearts demonstrated a significant prolongation of myocardial repolarization after induction of HF. Vernakalant caused a concentration-dependent (10 µmol/L and 30 µmol/L) increase of action potential duration (APD90) and QT interval without affecting spatial and temporal dispersion of repolarization. The increase in APD90 was accompanied by a greater increase in refractory period resulting in a significant increase in post-repolarization refractoriness. In control conditions, programmed ventricular stimulation and burst pacing led to ventricular fibrillation (VF) in 2 of the 12 sham (4 episodes) and in 3 of the 12 HF (24 episodes) subjects. In the presence of 30 µmol/L vernakalant, VF was no longer inducible in both groups (0 episodes). In the presence of low K+ concentration, neither sham nor HF vernakalant-treated subjects developed early after-depolarizations or ventricular tachyarrhythmias. CONCLUSION: In the present study, application of vernakalant led to a significant prolongation of myocardial repolarization and increased post-repolarization refractoriness but did not induce early after-depolarization and therefore did not cause proarrhythmia in failing hearts.

Evaluation of troponin I serum levels in patients with arrhythmias with and without coronary artery disease.

BACKGROUND: Elevated levels of cardiac enzymes in the blood are an indicator of ongoing cardiac ischemia. Persistent tachycardia may lead to myocardial ischemia due to oxygen supply-demand mismatch. OBJECTIVES: We sought to evaluate the probability of underlying coronary artery disease (CAD) in patients with symptomatic supraventricular (SVT) or ventricular tachyarrhythmias (VT) based on cardiac enzyme level fluctuation. MATERIALS AND METHODS: Troponin I (TNI) levels were measured twice and coronary angiography was also performed in patients without a history of cardiovascular disease and symptomatic SVT or VT. RESULTS: Of the 114 (group A: CAD (n = 40), group B: no CAD (n = 74)) patients eligible for the study, 34 patients in group A and 64 patients in group B had SVT, while 6 patients in group A and 10 patients in group B had VT. All patients with underlying CAD developed a significantly elevated TNI level compared to baseline, irrespective of arrhythmia type (2.02 ± 7.98 ng/ml vs. 5.64 ± 13.38, p = 0.031). In patients without CAD, TNI level was not significantly elevated compared to the baseline level, irrespective of arrhythmia type (0.34 ± 1.38 ng/ml vs. 0.48 ± 1.48 ng/ml, p = 0.158). Most patients with normal TNI levels (46 of 47 patients; 98 %) had SVT. CAD was present in 13 of 47 patients (27 %) with tachycardia, despite normal TNI levels. CONCLUSIONS: Elevated TNI levels are not helpful to discriminate between SVT and VT. An increase in TNI level in repeated blood sampling can help identify patients with higher probability of underlying CAD. Patients with VT demonstrated higher increases in TNI levels, compared to patients with SVT.

Cephalic Vein Cutdown Is Superior to Subclavian Puncture as Venous Access for Patients with Cardiac Implantable Devices after Long-Term Follow-Up.

BACKGROUND: Cephalic vein cutdown (CVC) and subclavian vein puncture (SVP) are the most commonly used access sites for transvenous lead placement of cardiac implantable electronic devices (CIEDs). Limited knowledge exists about the long-term patency of the vascular lumen housing the leads. METHODS: Among the 2703 patients who underwent CIED procedures between 2005 and 2013, we evaluated the phlebographies of 162 patients scheduled for an elective CIED replacement (median of 6.4 years after the first operation). The phlebographies were divided into four stenosis types: Type I = 0%, Type II = 1-69%, Type III = 70-99%, and Type IV = occlusion. Due to the fact that no standardized stenosis categorization exists, experienced physicians in consensus with the involved team made the applied distribution. The primary endpoint was the occurrence of stenosis Type III or IV in the CVC group and in the SVP group. RESULTS: In total, 162 patients with venography were enrolled in this study. The prevalence of high-degree stenosis was significantly lower in the CVC group (7/89, 7.8%) than in the SVP group (15/73, 20.5%, p = 0.023). In the CVC group, venographies showed a lower median stenosis (33%) than in the SVP group (median 42%). CONCLUSIONS: The present study showed that the long-term patency of the subclavian vein is higher after CVC than after SVP for venous access in patients with CIED.

Prognostic Implications of Coronary Artery Sclerosis in Troponin-Positive Patients with Non-Obstructive Coronary Arteries.

INTRODUCTION: Coronary sclerosis is a risk factor for the progression to obstructive coronary artery disease (CAD). However, understanding its impact on the outcomes of patients with myocardial infarction and non-obstructive coronary arteries is limited. This study aimed to explore the prognostic influence of coronary sclerosis on in- and out-of-hospital events in troponin-positive patients with non-obstructive coronary arteries. METHODS: This study was a retrospective cohort analysis based on prospectively collected data. A total of 24,775 patients who underwent coronary angiography from 2010 to 2021 in a German university hospital were screened, resulting in a final study cohort of 373 troponin-positive patients with non-obstructive coronary arteries and a follow-up period of 6.2 ± 3.1 years. Coronary sclerosis was defined as coronary plaques without angiographically detectable stenotic lesions of 50% or more in the large epicardial coronary arteries. The primary study endpoint was the occurrence of in-hospital events. Secondary endpoints included events during follow-up. RESULTS: Patients with coronary sclerosis were significantly older (70 ± 12 vs. 58 ± 16 years, p < 0.001), had ST-segment elevation less frequently on electrocardiogram (9.4% vs. 18.7%, p = 0.013), and suffered more often from diabetes mellitus (23.3% vs. 13.1%, p = 0.009), arterial hypertension (79.6% vs. 59.8%, p < 0.001), chronic obstructive pulmonary disease (17.1% vs. 9.4%, p = 0.028), chronic kidney disease (22.2% vs. 8.4%, p < 0.001), atrial fibrillation (19.8% vs. 12.2%, p = 0.045), and valvular diseases than patients without CAD. Patients with coronary sclerosis were more likely to receive medication for primary/secondary prevention on admission and at discharge. The incidence of in- and out-of-hospital events was significantly higher in patients with coronary sclerosis (in-hospital: 42.8% vs. 29.9%, p = 0.010; out-of-hospital: 46.0% vs. 26.1%, p < 0.001). Mortality rates tended to be higher in the coronary sclerosis group (29.4% vs. 20.0%, p = 0.066). CONCLUSION: Patients diagnosed with coronary sclerosis presented a higher incidence of comorbidities and increased medication use, and experienced higher rates of both in-hospital and out-of-hospital events, primarily due to the clustering of cardiovascular risk factors.