Electrophysiological characteristics and clinical values of left bundle branch current of injury in left bundle branch pacing.

BACKGROUND: Left bundle branch pacing (LBBP) is emerging as a novel option for physiological ventricular pacing. The impact of current of injury (COI) at left bundle branch (LBB) has not been previously evaluated. METHODS: Consecutive patients with QRS duration less than 120 milliseconds referred for LBBP in whom LBB potentials were recorded were included from August 2018 to March 2019. We recorded LBB COI during LBBP and assessed its impact on the pacing parameters and complications during implantation and at short term follow-up. RESULTS: A total of 115 patients with an identifiable LBB potential at implant were included. LBB COI was confirmed in 77 (67.0%) of these patients. Three types of LBB COI were observed. LBB was captured in all patients at a pacing threshold less than 1.5 V/0.5 ms in COI(+) patients, while present in only 29 patients without an LBB COI(-) (100% vs 76.3%; P < .001). There was no significant difference between COI(+) and COI(-) patients in LBB bundle capture threshold (0.64 ± 0.24 vs 0.74 ± 0.26 V/0.5 ms). Selective LBBP was more common in COI(+) group than COI(-) group (54.5% vs 0%; P < .001). Pacing parameters were stable and no lead perforation or dislodgements were observed during follow-up. CONCLUSIONS: LBB COI is commonly observed during LBBP in cases with an identifiable LBB potential and can be associated with a low LBB capture threshold and demonstrable selective capture of the LBB acutely and during follow-up. A COI does not preclude safe and stable LBBP pacing.

Risk factors for atrioventricular block after transcatheter aortic valve implantation: a single-centre analysis including assessment of aortic calcifications and follow-up.

AIMS: To assess the contribution of aortic valve calcification to the occurrence of transient or permanent atrioventricular block (AVB) and the need for permanent pacemaker implantation (PPI) after transcatheter aortic valve implantation (TAVI) in a large single-centre cohort. METHODS AND RESULTS: We retrospectively analysed pre-operative contrast-enhanced multidetector computed tomography scans of patients who underwent TAVI in our centre between 2012 and 2016. Calcium volume was calculated for each aortic cusp above (aortic valve), and below [left ventricular outflow tract (LVOT)] the basal plane. Clinical and procedural data as well as pre-operative electrocardiograms were evaluated. Multivariate analysis was performed to evaluate risk factors for transient and permanent AVB. A total of 342 patients receiving a balloon-expandable prosthesis were included in the study. Overall incidence of transient and permanent AVB was 4% (n = 14) and 7.6% (n = 26), respectively. On logistic regression analysis, baseline right bundle branch block [odds ratio (OR) 7.36, 95% confidence interval (CI) 2.6-20.6; P < 0.01], degree of oversizing (OR 1.04, 95% CI 1.01-1.07 P = 0.02), prior percutaneous coronary intervention (OR 2.8, 95% CI 1.1-7.3), and LVOT calcification beneath the non-coronary cusp (OR for an increase of 10 mm3 = 1.06, 95% CI 1-1.1; P = 0.03) were found to be independently associated with permanent AVB and PPI, whereas calcification of LVOT beneath the right coronary cusp (OR for an increase of 10 mm3 = 1.16, 95% CI 1.02-1.3; P = 0.02) and balloon post-dilation (OR 3.8, 95% CI 1.2-11.8; P = 0.02) were associated with reversible AVB. CONCLUSION: Left ventricular outflow tract calcifications are associated with transient and non-reversible AVB after TAVI, and its evaluation could help in predicting onset and reversibility of AVB.

Histological topography of the atrioventricular node and its extensions in relation to the cardiothoracic surgical landmarks in normal human hearts.

BACKGROUND: Atrioventricular (AV) nodal injury which results in cardiac conduction disorders is one of the potential complications of heart valve surgeries and radiofrequency catheter ablations. Understanding the topography of the AV conduction system in relation to the tricuspid and mitral valves will help in reducing these complications. METHODS: A tissue block of 3cmx4cm, which contain the AV node, bundle of His and the AV nodal extensions, was excised at the AV septal junction in 20 apparently normal human hearts. The block was divided into three equal segments through vertical incisions perpendicular to the insertion of the septal leaflet of the tricuspid valve. Each segment was processed and stained with H&E and Gomori to study the different parts of the AV conduction system. RESULTS: The lower pole of the AV node was located vertically above the tricuspid septal leaflet (TSL) in 100% (20/20) of cases and at the level of the muscular interventricular septum in 65% (13/20) of cases. The upper pole of the compact AV node was located at the level of the mitral valve leaflet (MVL) in 50% (10/20) of cases. The penetrating bundle of His was seen at the level of the TSL, while the branching bundle of His was situated 1.9±1.5 mm inferior to the TSL. The right and left posterior extensions of the AV node spanned from the MVL to 2.9±1.3 mm above the TSL. CONCLUSIONS: A rectangular area (2.5 mm × 12 mm) in the Koch's triangle was devoid of AV nodal tissue and could be labeled as a safe area with no risk of conduction defects during valve surgeries. Information on the separation of AV nodal extensions from the TSL, MVL and muscular interventricular septum may play a crucial role in guiding and improving the safety of radiofrequency ablations.

Aortoventricular annulus shape as a predictor of pacemaker implantation following transcatheter aortic valve replacement.

AIMS: Conduction abnormalities following transcatheter aortic valve replacement (TAVR) are caused by damage of the aortoventricular conduction tissue during positioning of the valve. Therefore, our aim was to assess whether a higher difference between the long and short diameters of the elliptic aortoventricular annulus will possess higher forces on the annulus, and thus will be a predictor of pacemaker need following TAVR. METHODS: We retrospectively analyzed 123 patients who had the aortoventricular annulus measured by computed tomography angiography. The difference between maximal (Dmax) and minimal (Dmin) diameters of the annulus was considered the elliptic factor (ELFA), which was analyzed using t test to evaluate whether it differs between the group who received a pacemaker and the group without the need for a pacemaker. Then, using univariate and multivariate models adjusted for other confounders predicting the need for a pacemaker, we sought to evaluate whether a higher ELFA is a predictor of pacemaker implantation. RESULTS: Mean age was 82.2 ±â€Š6.4 years, and 62.6% were women. Average Dmax, Dmin and ELFA were 25.8, 20.8 and 5 mm, respectively. Fourteen patients (11.4%) underwent pacemaker implantation. Those patients had an ELFA of 5.9 mm compared with 4.9 mm in those who did not receive a pacemaker (P < 0.01). In multivariate analysis, a higher ELFA remained a statistically significant and independent predictor for the need of a pacemaker (P = 0.046). CONCLUSION: A high ELFA is an independent and significant predictor of the need for pacemaker implantation after TAVR and suggests further investigation whether it should be considered as a factor in managing TAVR patients.

Incidence, predictors, and outcome of conduction disorders after transcatheter self-expandable aortic valve implantation.

The aims of the present study were to investigate the incidence and characteristics of conduction disorders (CDs) after transcatheter aortic valve implantation (TAVI), to analyze the predictors of permanent pacemaker (PPM) implantation, and to evaluate the outcomes of CDs over time. In particular, we sought to investigate whether the depth of deployment and other technical aspects of valve implantation might predict the need for PPM implantation after TAVI. TAVI has been reported to favor the onset or worsening of CDs often requiring PPM implantation. A total of 70 patients with aortic stenosis due to dystrophic calcification underwent TAVI with third-generation CoreValve Revalving System from May 2007 to April 2009. We collected electrocardiograms at baseline, during TAVI, during hospitalization and at the 1-, 3-, 6-, and 12-month follow-up visits thereafter. The clinical, anatomic, and procedural variables were tested to identify the predictors of PPM implantation. The PPM dependency at follow-up was analyzed. Six patients were excluded from the analysis because of a pre-existing PPM. Of the 64 patients, 32 (50%) had one or more atrioventricular-intraventricular CDs at baseline. TAVI induced a worsening in the CDs in 49 (77%) of the 64 patients, with 25 (39%) requiring in-hospital PPM implantation. On multivariate analysis, the independent predictors of PPM implantation were the depth of the prosthesis implantation (p = 0.039) and the pre-existing right bundle branch block (p = 0.046). A trend in the recovery of the CDs over time was recorded, although 2 patients required PPM implantation 1 month after discharge for late complete atrioventricular block. In conclusion, TAVI often induces or worsens CDs, requiring PPM in more than one third of patients, although a trend in the recovery of CDs during the midterm was recorded. The independent predictors of PPM implantation were the depth of prosthesis implantation and pre-existing right bundle branch block.

The surface electrocardiogram predicts risk of heart block during right heart catheterization in patients with preexisting left bundle branch block: implications for the definition of complete left bundle branch block.

BACKGROUND: Patients with left bundle branch block (LBBB) undergoing right heart catheterization can develop complete heart block (CHB) or right bundle branch block (RBBB) in response to right bundle branch (RBB) trauma. We hypothesized that LBBB patients with an initial r wave (>or=1 mm) in lead V1 have intact left to right ventricular septal (VS) activation suggesting persistent conduction over the left bundle branch. Trauma to the RBB should result in RBBB pattern rather than CHB in such patients. METHODS: Between January 2002 and February 2007, we prospectively evaluated 27 consecutive patients with LBBB developing either CHB or RBBB during right heart catheterization. The prevalence of an r wave >or=1 mm in lead V1 was determined using 118 serial LBBB electrocardiographs (ECGs) from our hospital database. RESULTS: Catheter trauma to the RBB resulted in CHB in 18 patients and RBBB in 9 patients. All 6 patients with >or=1 mm r wave in V1 developed RBBB. Among these 6 patients q wave in lead I, V5, or V6 were present in 3. Four patients (3 in CHB group and 1 in RBBB group) developed spontaneous CHB during a median follow-up of 61 months. V1 q wave >or=1 mm was present in 28% of hospitalized complete LBBB patients. CONCLUSIONS: An initial r wave of >or=1 mm in lead V1 suggests intact left to right VS activation and identifies LBBB patients at low risk of CHB during right heart catheterization. These preliminary findings indicate that an initial r wave of >or=1 mm in lead V1, present in approximately 28% of ECGs with classically defined LBBB, may constitute a new exclusion criterion when defining complete LBBB.

Is complete heart block after surgical closure of ventricular septum defects still an issue?

BACKGROUND: A serious complication after surgical closure of ventricular septal defect (VSD) is complete heart block. In this retrospective study, we reviewed the incidence of complete heart block after surgical closure of a VSD at Great Ormond Street Hospital from 1976 to 2001 to identify any particular anatomic features that still predisposed patients to surgically-induced complete heart block and to provide anatomic guidelines to avoid this in future. METHODS: Data were extracted from our local database for patients having (1) isolated VSD or VSD in the setting of (2) tetralogy of Fallot with pulmonary stenosis or (3) tetralogy of Fallot with pulmonary atresia; (4) absent pulmonary valve syndrome; (5 and 6) coarctation or interruption of the aortic arch; and (7) subaortic fibrous shelf. We carefully reviewed the operative notes from all patients with postoperative complete heart block to discover any predisposing anatomical reasons to explain the complication. RESULTS: Two thousand seventy-nine patients had a VSD closure. Permanent complete heart block developed in 7 of 996 patients (0.7%) with an isolated defect and in 1 of 847 patients (0.1%) with tetralogy of Fallot. Four more patients had postoperative complete heart block. CONCLUSIONS: Instances of iatrogenic complete heart block continue to occur after surgical VSD closure, either because of unexpected biological variations or because of unawareness of the disposition of the atrioventricular conduction axis in particular circumstances. This report emphasizes the latter aspect in details and suggests a risk of iatrogenic complete heart block of less than 1%.

Complete atrioventricular block induced during left heart catheterization.

Complete atrioventricular block (CAVB) during cardiac catheterization is a rare complication. We describe a patient with preexisting complete right bundle branch block who developed CAVB during left-sided cardiac catheterization. CAVB was induced when a left-sided catheter was passed through the aortic valve. We speculate that the patient's His bundle was injured by mechanical compression. Physicians should always pay attention to the possibility of the development of CAVB during cardiac catheterization, particularly in patients with preexisting heart block.

Sequelae of atriotomy and ventriculotomy on the endocardium, conduction system and coronary arteries.

The endocardium was analyzed in all four chambers of 99 hearts with various types of congenital heart defects in which surgical repair was performed more than 6 weeks before death. The findings were compared with those of normal hearts in similar age groups. In some cases the endocardium was microscopically examined. This study revealed that in many cases all four chambers had fibroelastosis of the endocardium (diffuse regardless of the type of surgery done previously). These data suggest that diffuse fibroelastosis can occur as a result of surgical intervention and may be related to blocked lymphatic drainage. Sudden death in some patients long after surgery for congenital heart disease and the failure of the chambers to regress to normal size in some cases after total surgical repair may be related to fibroelastosis of the chambers. The sinoatrial node may be injured in atriotomy and in the performance of the Mustard procedure. Ventriculotomy may injure the right bundle branch. Ventriculotomy may also injure the coronary supply to the right ventricle or rarely the anterior descending coronary artery.

Echocardiographic assessment of right bundle branch injury after repair of tetralogy of Fallot.

Nineteen patients, ages 3 1/2-18 years, with electrocardiographic evidence of right bundle branch injury after intracardiac repair of tetralogy of Fallot, underwent invasive intracardiac electrophysiologic evaluation 1-13 years (mean 4.4 years) postoperatively. Categorization of the site of right bundle branch injury as proximal or distal was made by determining the V-RVA interval. In 11 of the patients, the V RVA interval was prolonged (> 35 msec), indicating proximal right bundle branch injury and in the other eight it was normal (< 35 msec), indicating distal bundle branch injury. Within 24 hours of the study, all patients were studied by M-mode echocardiography. Measurements were made of the tricuspid valve closure, mitral valve closure and the difference between the two, or the delta value. All but one patient with distal bundle branch injury had delta values of less than 40 msec (range 8-38 msec), while 10 or 11 patients with proximal bundle branch injury had delta values greater than 40 msec (range 41-116 msec). there was a significant positive correlation (r = 0.74, p < 0.001) between V-RVA and the delta value. We conclude that the delta value is an indicator of relative activation delay of the right ventricle, and therefore, in most cases, proximal vs distal bundle branch injury can be diagnosed noninvasively.

The significance of dissociation of conduction in the canine His bundle. Electrophysiological studies in vivo and in vitro.

Fractionated His bundle potentials were induced by ischemia or trauma in 30 anesthetized dogs, in vivo. Functional dissociation, i.e., alteration of the activation sequence of portions of these His bundle potentials was demonstrated in vivo as well as in 10 in vitro preparations of the His-Purkinje system. In vivo, plunge wire and electrode catheters were utilized to record from portions of the His bundle. During vagal-induced slowing of the heart rate, atrial pacing or His bundle pacing, His-Purkinje conduction as measured by the H-V interval was constant over a wide range of heart rates, 50-300/min. One or two hours after anterior septal artery ligation, His bundle damage manifested as split His bundle potentials (H, H'). Atrial pacing or proximal His bundle pacing induced H-H' delays with concomitant right or left bundle branch block patterns in ECG leads. However, distal His bundle pacing at comparable or even higher rates produced normal QRS complexes. In other cases, during atrial pacing or with progressive ischemia at a constant rate, H' progressively delayed during the H-V interval or even disappeared into the QRS complex with a concomitant occurrence of right or left bundle branch block. In vitro, a dissected septal preparation was studied containing the His bundle, proximal and distal right bundle and left bundle branches. Normal conduction throughout the His-Purkinje system was observed at pacing rates of 30-220/min. Punctate lesions, anatomically placed above the branching His bundle caused tachycardia-dependent, complete bundle branch blocked with concurrent temporal reversal of proximal and distal His bundle action potentials. These data suggest that ischemic or traumatic lesions in the His bundle may manifest on the electrocardiogram as bundle branch block patterns. From a clinical point of view, a critical site of lesion would markedly increase the liability for A-V blocked although the electrocardiogram alone would not indicate the actual site of lesion. Predestination of fiber tracts and alternative proposals to the pedestination theory are considered to explain QRS aberration due to exclusive His bundle lesions.

[New open heart technic of locating the bundle of His]. / Nouvelle technique de repérage à coeur ouvert du faisceau de His

The use of a system of electronic potentials for locating the bundle of His during open heart operations has provided a means for localising the conducting pathways so that they are not damaged during surgery. The designing of a special apparatus for this purpose has made it especially suitable for use in man, and it increases the ECC time by only a few minutes. The apparatus consists essentially of electrodes designed specially for the purpose, a cardiac stimulator and a calibrated oscilloscope with an electrostatic memory. The effectiveness of this technique has been confirmed in a preliminary series of 15 cases.

[Closure of ventricular septal defects. Comparison of 2 technics]. / La fermeture des défauts septaux interventriculaires.Comparaison de deux techniques

To be correctly done, closure of a ventricular septal defect must be sound, and must also avoid damage to the conducting tissue. These two essentials are somewhat contradictory, since in order to avoid the bundle of His in its position along the postero-inferior edge of the ventricular septal defect (VSD) in the membranous septum, the sutures inserted into this region must be superficial, and therefore weak. It is for this reason that the published series continue to show evidence of a significant number of post-operative shunts and atrio-ventricular blocks, as much in the closure of isolated VSDs as in the treatment of Fallot's tetralogy. This paper compares two techniques of suturing the prosthetic material which is used to close the VSD: the classical technique, in which it is intended to avoid the bundle of His by working below it, on the right side of the interventricular septum, and a different technique in which the sutures are applied directly to the free edge of the interventricular communication.

Pathologic correlations in a case of complete heart block with split His potentials resulting from a stab wound of the heart.

A 23 year old previously healthy man was stabbed in the anterior chest. This resulted in a ventricular septal defect and complete atrioventricular (A-V) block. The electrocardiogram revealed complete A-V block with a QRS pattern of right bundle branch block. His bundle recordings 26 days later revealed A-V dissociation with split His potentials (P-H1 interval of 100 msec and H2-V interval of 40 msec). During the study the escape QRS shifted from right to left bundle branch block with H2 potentials still preceding each QRS interval with H2-V intervals of 40 msec. A permanent pacemaker was implanted because of persistent congestive heart failure and bradycardia due to A-V block. The patient subsequently became asymptomatic. He died suddenly 3 1/2 years later. Pathologically there were sizable openings in both the tricuspid and mitral valve substance and a ventricular septal defect involving the pars membranacea and part of the adjacent muscular septum. Serial sections of the conduction system revealed total destruction and fibrous replacement of the bifurcation and beginning of the right and left bundle branches and subtotal fibrous replacement of the branching bundle. Thus, the bifurcation of the bundle of His was totally absent at autopsy despite apparent electrophysiologic evidence of its existence 26 days after the stab wound. A possible explanation for this discrepancy is the subsequent fibrosis of the bifurcation produced by hemodynamic changes at the lower margin of the ventricular septal defect.

[Atrioventricular conduction by a bundle of Kent discovered after a surgical A.V.B]. / Conduction atrio-ventriculaire par un faisceau de Kent démasqué après un B.A.V. chirurgical

The case is reported of an 8 year old child who had a 1/1 atrio-ventricular conduction by the bundle of Kent after accidental surgical division of the bundle of His; this "accessory" pathway conducted satisfactorily over a period of 12 years. At the age of 20, the patient had a complete conduction block of the bundle of Kent, causing a complete atrio-ventricular block; this indicated the definitive insertion of a pacemaker.