Predictors of procedural failure of left bundle branch pacing in scarred left ventricle.

INTRODUCTION: Presence of scar at the implantation-site is considered as a major factor in determining the success of left bundle branch pacing (LBBP). We aimed at analyzing the predictors of procedural failure in patients with scarred-left ventricle (LV) as demonstrated by cardiac-magnetic resonance-imaging (CMR). METHODS: This was a retrospective, observational single-center-study that included consecutive cardiomyopathy patients with LV-scar as demonstrated by late-gadolinium-enhancement (LGE) in CMR requiring LBBP. Procedural-failure was defined as the inability to penetrate the septum to reach the LV subendocardium RESULTS: A total of 25 cardiomyopathy patients demonstrated LGE in CMR and were included in the study. LBBP was successful in 16 patients (group-I; 64% acute-procedural-success). In the remaining 9 patients (group-II) lead could not be penetrated and hence biventricular-pacing was done. LBBP resulted in reduction in QRS-duration and improvement in LV ejection fraction in group-I patients during a mean follow-up of 11.2 ± 3.7 months. Computed-tomography-angiography after LBBP showed the successful lead deployment site (LBBP-Zone) as the overlapping areas of inferior aspect of antero-septum and superior aspect of infero-septum (segment 2/3; AHA-model) in short-axis view(figure-1C). CMR showed LGE in significantly more number of LV-segments and high scar-burden in group-II as compared to group-I (figure-1). A total scar score value of >1.0 predicted failure with 100%-sensitivity and 75%-specificity. CMR revealed transmural-scar in the LBBP-Zone in all patients in group-II (n = 9; 100%). Transmural scar in LBBP-Zone by CMR had 100%-sensitivity and 100%-specificity for predicting the procedural-failure. CONCLUSION: CMR helps in predicting the procedural failure of LBBP in patients with scarred LV. Presence of transmural-LGE in the LBBP-Zone predicts failure with high sensitivity and specificity.

Lack of evidence for longitudinal dissociation of the atrioventricular conduction axis.

Longitudinal dissociation of the aggregated specialized cardiomyocytes within the non-branching portion of atrioventricular conduction axis has proved a controversial topic for both morphologists and electrophysiologists. We have now used morphological methods, including three-dimensional assessment, to revisit, in human, canine, and bovine hearts, the presence or absence of interconnections between the aggregated cardiomyocytes making up the non-branching bundle. We analyzed three datasets from human and canine hearts, and two from bovine hearts, using longitudinal and orthogonal serial histological sections. In addition, we assessed three hearts using translucent India ink injected specimens, permitting assessment of the three-dimensional arrangement of the cardiomyocytes. Using the longitudinal sections, we found numerous oblique interconnections between the groups of specialized cardiomyocytes. When assessing orthogonal sections, we noted marked variation in the grouping of the cardiomyocytes. We interpreted this finding as evidence of bifurcation and convergence of the groups seen in the longitudinal sections. The three-dimensional assessment of the bovine material confirmed the presence of the numerous interconnections. The presence of multiple connections between the cardiomyocytes in the non-branching bundle rules out the potential for longitudinal dissociation.

Hisian extrasystole mimicking second degree atrioventricular block. a case report.

Hisian extrasystoles originate from the His bundle. They are rare and usually misdiagnosed. In fact, they manifest on the EKG, with a p' wave located before, in or after the QRS complex. More rarely, the extrasystole blocks the propagation of the influx to the ventricles simulating a Mobitz II atrioventricular (AV) block. We report the case of a 36-Year-old woman with no medical History, suffering from presyncope and palpitations at rest. Her physical examination and EKG were normal. The 24-hour Holter monitoring showed some long periods with unexpected blocked p waves but with no significant pause. Considering her young age and the absence of causes of AV block, we performed an intracardiac electrophysiological study which showed hisian extrasystoles with normal conduction tissue properties at baseline and under flecainide. The diagnosis of hisian extrasystoles simulating Mobitz II AV block was made. A simple monitoring with beta-blockers therapy was recommended. Hisian extrasystoles may simulate first or second degree AV block with different therapeutic and prognostic implications. Nevertheless, these hisian extrasystoles may be the marker of a vulnerable AV conduction, long-term follow up should be considered.

The Complexity of the His Bundle: Understanding Its Anatomy and Physiology through the Lens of the Past and the Present.

In this paper, we describe the anatomy and physiology of the His bundle and describe the mechanisms by which permanent His-bundle pacing can be accomplished.

[Dilated cardiomyopathy: the role of left branch of atrioventricular bundle block in left ventricular walls longitudinal strain indices change].

Activity of the heart is assured by the myocardium motion with a composite path, which can be described with various quantitative indices, in particular the strain ones. The invention and implementation into clinical practice the "Speckle Tracking" ultrasonic technology, based on the two-dimensional echocardiography, allows to study of normal myocardium function as well as its functioning in various hart lesions, in particular, dilated cardiomyopathy (DCMP). Peculiarities of the features of longitudinal strain parameters of left ventricular (LV) walls in patients with DCMP, according to the occurrence of the total left branch of atrioventricular bundle block were studied. In DCMP the indices of longitudinal myocardial strain of the LV were strongly decreasing with the augmenting of heart failure signs. The appearance of the total left branch of atrioventricular bundle block, manifested by the total decrease of amplitude of longitudinal strain of the lateral and posterior walls of the LV, led to the augmenting of mitral regurgitation (up to 2+) and increase of the pulmonary hypertension, augmenting of circulatory deficiency signs.

Counterclockwise heart rotation affects variation in successful ablation line position in common atrial flutter.

BACKGROUND: Linear ablation of atrial flutter usually targets a 6 o'clock position on the cavotricuspid isthmus on left anterior oblique view, but the difficulty of the ablation often requires a variation in successful ablation line position from 5 to 7 o'clock. METHODS AND RESULTS: This study included 94 patients without structural heart disease. A linear lesion was created in turn at the 6, 7, and 5 o'clock positions until bidirectional block of the isthmus was completed; the final lesion was defined as the successful ablation line. The degree of counterclockwise heart rotation (CCW-HR) was evaluated in a blinded fashion according to the angle between the vertical line crossing the His bundle catheter and the line connecting the His bundle catheter and coronary sinus ostium. Successful ablation lines were obtained at the 6 o'clock position in 59 patients (63%); the 7 o'clock position in 19 patients (20%; the oldest group with a moderate radiofrequency burden); and the 5 o'clock position in the remaining 16 (17%; the youngest group with the largest radiofrequency burden). Age-related increase in CCW-HR was the only independent predictor of a more septal successful ablation line (OR, 7.1; 95% CI: 3.3-14.3; P<0.01). CONCLUSIONS: Variation in successful ablation line position was affected by age-related CCW-HR; its evaluation might reduce radiofrequency burden, especially in the young and elderly.

A new method of building permanent A-V block model: ablating his-bundle potential through femoral artery with pre-implanted biventricular pacemaker.

BACKGROUND: To explore the feasibility of a new method of achieving a permanent A-V block animal model. METHODS: 16 beagles were randomly divided into two groups based on the method of their pre-implanted biventricular pacemakers. (1) In the first group (8 beagles), the A-V block model was achieved by ablating his-bundle potential at the site of the left ventricular superior-septum, under the aortic sinus, through femoral artery. (2) In the second group (8 beagles), the A-V block model was achieved by ablating his-bundle potential at the triangle of Koch, through femoral vein. A complete A-V block model was achieved as a standard in this study. The success rates, intraoperative arrhythmias, operative and X-ray exposure time, intraoperative bleeding amount were assessed in this two groups, both animal models were followed up for four weeks and then fasted to monitor myocardial pathological changes. RESULTS: The success rate of the first group, which with fewer intraoperative arrhythmias, and less operative and X-ray exposure time, was significantly higher than the second group. CONCLUSIONS: Compared with traditional animal method, our new method of ablating his-bundle potential at the left ventricle from the femoral artery has a higher success rate, fewer occurrence of malignant arrhythmias, and less operation and X-ray time. Thus, our new method should be preferred in the building of Permanent A-V Block Model.

Electroanatomically estimated length of slow pathway in atrioventricular nodal reentrant tachycardia.

The length of the slow pathway (SP-L) in atrioventricular (AV) nodal reentrant tachycardia (NRT) has never been measured clinically. We studied the relationship among (a) SP-L, i.e., the distance between the most proximal His bundle (H) recording and the most posterior site of radiofrequency (RF) delivery associated with a junctional rhythm, (b) the length of Koch's triangle (Koch-L), (c) the conduction time over the slow pathway (SP-T), measured by the AH interval during AVNRT at baseline, and (d) the distance between H and the site of successful ablation (SucABL-L) in 26 women and 20 men (mean age 64.6 ± 11.6 years), using a stepwise approach and an electroanatomic mapping system (EAMS). SP-L (15.0 ± 5.8 mm) was correlated with Koch-L (18.6 ± 5.6 mm; R 2 = 0.1665, P < 0.005), SP-T (415 ± 100 ms; R 2 = 0.3425, P = 0.036), and SucABL-L (11.6 ± 4.7 mm; R 2 = 0.5243, P < 0.0001). The site of successful ablation was located within 10 mm of the posterior end of the SP in 38 patients (82.6 %). EAMS-guided RF ablation, using a stepwise approach, revealed individual variations in SP-L related to the size of Koch's triangle and AH interval during AVNRT. Since the site of successful ablation was also correlated with SP-L and was usually located near the posterior end of the SP, ablating anteriorly, away from the posterior end, is not a prerequisite for the success of ablation procedures.

Atrio-hisian fibers anatomy and electrophysiology.

INTRODUCTION: In this case, electrophysiology and histology could be studied in the same heart. Clinical investigation, clinical electrophysiology, and postmortem serial histological sections of the septum were analyzed. METHODS: A patient with repeated seizures and a short PR interval with narrow QRS complex underwent electrophysiologic studies. RESULTS: The patient died while experiencing a very rapid supraventricular tachycardia and histologic examination showed a atrio-hisian bypass tract. CONCLUSION: In our study, the lack of lengthening of the PR interval in spite of progressively premature atrial stimulation connected with the presence of atrio-hisian bypass tract.

The anatomical basis of third-degree atrioventricular block in dogs with atrioventricular valve endocardiosis.

The cardiac conduction system was examined histologically in 13 canine cases of atrioventricular (AV) valve endocardiosis with third-degree AV block. In all cases, gross examination revealed marked thickening and distortion of the base of the central fibrous body (CFB) and varying degrees of endocardial thickening of the upper portion of the ventricular septum (VS) as well as marked thickening of the mitral and tricuspid valve leaflets due to myxomatous degeneration. Microscopically, the thickened and distorted CFB had encased or trapped, either partly or totally, the underlying penetrating and branching portions of the AV bundle. The myxomatous and/or fibrofatty tissue, which had proliferated at the base of the extensive CFB, protruded into or encroached on the AV bundle, causing severe (51-75%) to very severe (76% or more) reduction of the conduction fibres. The upper portions of the left and right bundle branches were involved in the endocardial thickening due to degenerative and fibrotic changes at the uppermost VS; however, both bundle branches were much less severely affected than the AV bundle, the degree of reduction of the conduction fibres ranging from mild (25% or less) to moderate (26-50%). These observations suggest that the sites most vulnerable to lesions in the AV conduction system are the penetrating and branching portions of the AV bundle, which would represent the anatomical basis for third-degree AV block in canine cases of AV valve endocardiosis.

Development of an ovine model of pediatric complete heart block.

BACKGROUND: Complete heart block is a significant clinical problem that can limit the quality of life in affected children. To understand the pathophysiology of this condition and provide for development of novel therapies, we sought to establish a large animal model of permanent, pacemaker-dependent atrioventricular block (AVB) that mimics the size and growth characteristics of pediatric patients. MATERIALS AND METHODS: We utilized nine immature lambs weighing 10.5 ± 1.4 kg. After implantation of dual-chamber pacemaker devices with fixed leads, AVB was produced by interrupting His-bundle conduction using radio-frequency ablation at the base of the non-coronary cusp of the aortic valve. Ablations (30 to 60 s in duration) were performed under fluoroscopic guidance with electrophysiological monitoring. Interrogation of pacemakers and electrocardiography (ECG) determined the persistence of heart block. Ovine hearts were also examined immunohistochemically for localization of conduction tissue. RESULTS: AVB was produced in eight animals using an atypical approach from the left side of the heart. One animal died due to ventricular fibrillation during ablation proximal to the tricuspid annulus and one lamb was sacrificed postoperatively due to stroke. Four sheep were kept for long-term follow-up (109.8 ± 32.9 d) and required continuous ventricular pacing attributable to lasting AVB, despite significant increases in body weight and size. CONCLUSIONS: We have created a large animal model of pediatric complete heart block that is stable and technically practicable. We anticipate that this lamb model will allow for advancement of cell-based and other innovative treatments to repair complete heart block in children.

Successful RF ablation of atrial tachycardia from the non-coronary aortic cusp.

A 51-year-old lady presented with recurrent episodes of supraventricular tachycardia since 1 year. EP study revealed easily inducible atrial tachycardia. Endocardially, the earliest activation site was found in the His bundle region (-18 ms). The aorta was therefore mapped, and a site in the non-coronary cusp was found with an activation time of -30 ms. RF energy at this site successfully eliminated tachycardia. She is asymptomatic at 8 months of follow-up, without any anti-arrhythmic drug.

A histological study of the cardiac conduction system in canine cases of mitral valve endocardiosis with complete atrioventricular block.

The cardiac conduction system was examined histologically in four canine cases of endocardiosis of the mitral valve (MV) with complete atrioventricular (AV) block. In all cases, moderate to severe reduction of the conduction fibres due to fibrous or fibro-fatty replacement was observed in the penetrating and branching portions of the AV bundle. In addition, degenerative and fibrotic lesions were commonly seen at the upper portions of the left and right bundle branches. These changes in the AV conduction system were associated with marked degeneration and fibrosis of the base of the central fibrous body and the upper part of the ventricular septum. The degenerative and sclerotic changes of the AV junctional region, affecting the AV bundle and bundle branches, were qualitatively similar to those in age-matched control dogs, but were more severe. It is possible that the pathological process occurred as a result of ageing and may have been exaggerated or accelerated by the abnormal mechanical forces created by excessive motion of the prolapsed MV and the long-term haemodynamic stresses of mitral regurgitation, resulting in interruption of the AV conduction system to produce complete AV block. Conduction abnormalities represent a possible complication in some canine cases of MV endocardiosis.

An Unexpected Finding in SUDEP Involving a Child: Focal Myocardial Infarct Adjacent to Bundle of His.

Sudden unexpected death in epilepsy (SUDEP) is a nontraumatic, nondrowning death of an individual with epilepsy in which an autopsy with appropriate ancillary studies does not identify a cause of death. The mechanism of death in SUDEP is unknown, but is thought to involve cardiac and/or respiratory mechanisms. Research in SUDEP is hindered by a lack of consensus regarding required components of a death investigation before a cause of death may be certified as SUDEP. Histopathologic examination of the cardiac conduction system is not routinely performed in SUDEP death investigations. We present a case of SUDEP where histopathologic examination of the cardiac conduction system revealed a focal myocardial infarct of the summit of the ventricular septum abutting the bundle of His, which potentially provides insight into the mechanism of SUDEP for this particular case, and suggests that routine examination of the cardiac conduction system in SUDEP may be beneficial.

Experimental, Pathologic, and Clinical Findings of Radiofrequency Catheter Ablation of Para-Hisian Region From the Right Ventricle in Dogs and Humans.

BACKGROUND: Ablation of para-Hisian accessory pathway (AP) poses high risks of atrioventricular block. We developed a pacing technique to differentiate the near-field (NF) from far-field His activations to avoid the complication. METHODS AND RESULTS: Three-dimensional mapping of the right ventricle was performed in 15 mongrel dogs and 23 patients with para-Hisian AP. Using different pacing outputs, the NF- and far-field His activation was identified on the ventricular aspect. Radiofrequency application was delivered at the NF His site in 8 (group 1) and the far-field His site in 7 dogs (group 2), followed by pathologic examination after 14 days. NF His activation was captured with 5 mA/1 ms in 10 and 10 mA/1 ms in 5 dogs. In group 1, radiofrequency delivery resulted in complete atrioventricular block in 3, right bundle branch block with HV (His-to-ventricular) interval prolongation in 1, and only right bundle branch block in 2 dogs, whereas no changes occurred in group 2. Pathologic examination in group-1 dogs showed complete or partial necrosis of the His bundle in 4 and complete necrosis of the right bundle branch in 5 dogs. In group 2, partial necrosis in the right bundle branch was found only in 1 dog. Using this pacing technique, the APs were 5.7±1.2 mm away from the His bundle located superiorly in 20 or inferiorly in 3 patients. All APs were successfully eliminated with 1 to 3 radiofrequency applications. No complications and recurrence occurred during a follow-up of 11.8±1.4 months. CONCLUSIONS: Differentiating the NF His from far-field His activations led to a high ablation success without atrioventricular block in para-Hisian AP patients.

Relevance of inflammatory cell infiltrates for complete atrioventricular block in experimental murine myocarditis.

BACKGROUND: There are few systemic pathologic studies on myocarditis. This study aimed to clarify the pathologic characteristics of murine myocarditis. METHODS: We recorded serial electrocardiograms in experimental viral myocarditis in mice and then examined their cardiac pathology. After taking baseline electrocardiograms, we inoculated the mice intraperitoneally with the encephalomyocarditis virus. Electrocardiograms were serially recorded until 220 days after the virus inoculation. RESULTS: Serial electrocardiograms revealed ectopic beats, low voltage of the QRS complex, and the appearance of complete atrioventricular (AV) block. Corresponding myocardial lesions were found in the hearts of mice with these ectopic beats. Mononuclear cell infiltrations into the His bundle were most frequently found in mice with complete AV block. CONCLUSIONS: Inflammatory change with cellular infiltrations was the most common pathologic finding in mice with complete AV block. In clinical settings, anti-inflammatory therapy might be recommended for patients with myocarditis complicated with conduction disturbances.

Cardiomyocyte apoptosis in cocaine-induced myocarditis with involvement of bundle of His and left bundle branch.

Cocaine abuse can cause degenerative and inflammatory alterations of the myocardium. Cocaine-induced myocarditis has been previously described, but mostly in chronic cocaine addicts. Among several pathogenetic mechanisms of cocaine-related myocardial damage, the myocardial adrenergic stress and cardiomyocytes apoptosis have been recently proposed. We report an unusual case of myocarditis involving the bundle of His and left bundle branch and cardiac myocytes apoptosis in otherwise healthy occasional cocaine abuser.