A Comparison of the Electrophysiological and Anatomic Characteristics of Pacing Different Branches of the Left Bundle Conduction System

Introduction: Left bundle branch pacing (LBBP) is a rapidly growing conduction system pacing technique. However, little is known regarding the electrophysiological characteristics of different types of LBBP. We aimed to evaluate the electrophysiological characteristics and anatomic lead location with pacing different branches of the left bundle branch.Methods: Consecutive bradycardia patients with successful LBBP were enrolled and classified into groups according to the paced electrocardiogram and the lead location. Electrocardiogram, pacing properties, vectorcardiogram, and lead tip location were analyzed.Results: Ninety-one patients were enrolled, including 48 with the left bundle trunk pacing (LBTP) and 43 with the left bundle fascicular pacing (LBFP). The paced QRS duration in the LBTP group was significantly shorter than that in the LBFP group (108.1 ± 9.9 vs. 112.9 ± 11.2 ms, p = 0.03), with a more rightward QRS transition zone (p = 0.01). The paced QRS area in the LBTP group was similar to that during intrinsic rhythm (35.1 ± 15.8 vs. 34.7 ± 16.6 μVs, p = 0.98), whereas in the LBFP group, the paced QRS area was significantly larger compared to intrinsic rhythm (43.4 ± 15.8 vs. 35.7 ± 18.0 μVs, p = 0.01). The lead tip site for LBTP was located in a small fan-shaped area with the tricuspid valve annulus summit as the origin, whereas fascicular pacing sites were more likely in a larger and more distal area.Conclusions: Pacing the proximal left bundle main trunk produced better electrical synchrony compared with pacing the distal left bundle fascicles. A visualization technique can facilitate achieving LBTP.

Dynamical behavior of cardiac conduction system under external disturbances: simulation based on microcontroller technology

The heart rhythm is one of the most interesting aspects of the dynamic behavior of biological systems. Understanding heart rhythms is essential in the dynamic analysis of the heart. Each type of dynamic behaviour can describe normal or pathological physiology. The heart is made up of nodes ranging from SA node (natural pacemaker) to Purkinje fibers. The electric current originates in the sinus node and travels through the heart until it reaches the Purkinje fibers, causing after its passage through each of the nodes a heartbeat thus constituting the electrocardiogram (ECG). Since the origin of the electric current is the sinus node, in this article we study numerically and experimentally by microcontroller the influence of the sinus node on the propagation of electric current through the heart. A study of the sinus node in its autonomous state shows us that in their coupled state, the nodes of the heart qualitatively reproduce the time series of the action potential of this latter, which leads to the recording of the ECG. A study when the sinus node is subjected to periodic pulsed excitation E 1(t) = kP(t), assumed to come from blood pressure, with P(t) the blood pressure, shows that for some selected frequencies, it is found that the nodes of the heart and the ECG exhibit responses having the same shape and the same frequencies as those of the pulsatile blood pressure. This suggests the possibility of using such a conversion and excitation mechanism to replicate the functioning of cardiac conduction system. The chaotic analysis of the sinus node subjected to a sinusoidal type disturbance (E 0sin(ωt)) is also presented, it shows that in its chaotic state, the nodes of the heart, as well as the ECG, provide very high frequency signals. This requires the control of the sinus node (natural pacemaker) in such a situation

Hydraulic architecture of seedlings and adults of Rhizophora mangle L. in fringe and scrub mangrove

Background: Mangrove plant species have distinctive anatomical and physiological responses to cope with a wide range of salinities and inundations. These strategies pertain a safe and efficient water use and transport, essential for survival. Questions: How are the anatomical and physiological attributes of the hydraulic architecture of seedlings and adults of Rhizophora mangle? what are the changes in hydraulic architecture of seedlings and adults of R. mangle in contrasting microenvironments? Studied species: Rhizophora mangle L. (Rhizophoraceae). Study site and dates: Scrub and fringe mangroves in Ria Celestún Biosphere Reserve, during the rainy season of 2013 (July to October). Methods: Hydraulic conductivity and leaf water potential, as well as xylem vessel density, length, transversal and radial diameter, and area were measured for seedlings and adults from both sites. The prevailing environmental conditions (soil water potential, salinity, photon flux density, air temperature and relative humidity) were also characterized. Results: A safer hydraulic conduction system, with narrow and more grouped vessels, was observed in seedlings than in adults of R. mangle in both sites. Adult individuals from the scrub mangrove, in the hyper saline microenvironment, had a safer hydraulic conduction system than adults in the fringe mangrove. Conclusions: The seedling stage of R. mangle showed a safer hydraulic system than adults in both types of mangroves. However, over time this hydraulic conduction system could become more efficient or remain safe depending on the microenvironment in which individuals are growing.

83 The predictive role of neutrophil-to-lymphocyte ratio in post-operative cardiopulmonary bypass surgery

Aims Postoperative arrhythmias (POA) are a common complication after cardiac surgical repairs for congenital heart disease (CHD), representing a substantial source of morbidity, mortality, and prolonged total in-hospital stay, with an incidence of 7.5–48% in postoperative pediatric cardiac patients. The etiology is multifactorial, and it has been related to the direct surgical manipulation of the cardiac conduction system, to the local tissue inflammation in the myocardium adjacent to the conduction system and to the arrhythmogenic effects of cardiopulmonary bypass (CPB), inotropes, and electrolyte disturbances. Recently, the prognostic role of neutrophil-to-lymphocyte ratio (NLR), a novel inflammation marker, has been evaluated in pediatric patients after CPB surgery. To evaluate the predictive role of NLR in POA in a population of pediatric CHD patients after CPB. Methods and results We retrospectively collected perioperative clinical and laboratory data of 146 patients (age 8.27 ± 10.79 years; male gender: 60.8%) consecutively admitted to the cardiac surgery intensive care unit (ICU) of our institute after elective cardiac surgery with CPB in 2018. We grouped and analyzed our population over NLR tertiles evaluated at 24 h from CPB and types of POA: supraventricular (SVT) and junctional (JET). The prognostic value of NLR and its association with POA was analyzed. Diagnoses of 146 patients included atrial septal defect (n = 36), ventricular septal defect (n = 20), pulmonary atresia/stenosis (n = 10), tetralogy of Fallot (n = 20), endocardial cushion defect (n = 8), left ventricular outflow tract obstruction (n = 14), anomalous origin of coronary artery (n = 6), complex CHD (n = 13), interrupted/hypoplastic aortic arch (n = 12), anomalous pulmonary venous return (n = 3). The mean CPB time was 121.6 ± 84.6 min. The median ICU hospitalization was 48 h [Q1, Q3: 24, 96]. Twelve patients experienced POA: 6 SVT and 6 JET. The frequency of POA incremented over NLR-tertiles (P-Trend 0.017), while SVT onset was associated with higher values of NLR and C-reactive protein (P = 0.034 and P = 0.011, respectively). Patients in the second and third tertiles of NLR had a prolonged hospitalization (log-rank, P = 0.029), especially when associated with POA (log-rank, P = 0.012). At the multivariable analysis, higher age and NLR values were independently associated with SVT [OR per year 1.22; 95% CI (1.02, 1.25), P = 0.043 and OR per point 1.91; 95% CI (1.29, 2.82), P = 0.012, respectively], but not with JET. Conclusions 24-h post-CPB NLR can predict postoperative SVT in a population of pediatric CHD patients. Our data suggest that the NLR could be a useful, easy-to-obtain marker for postoperative outcome in pediatric patients who had undergone elective CPB.