Electrocardiographic Morphology Research Articles

Left bundle branch area pacing in the setting of cardiac amyloidosis: a case series

Abstract Background Cardiac amyloidosis (CA) is a highly prevalent cause of congestive heart failure. It often requires cardiac pacing due atrioventricular conduction (AV) system disorders, often with cardiac resynchronization (CRT) to prevent development/deterioration of left ventricular (LV) dysfunction. Left bundle branch area pacing (LBBAP) is an emerging alternative to CRT, offering a strict physiological LV activation and very limited use of iodinated contrast. The feasibility of LBBAP in CA is considered limited due to the presence of septal pseudohypertrophy which theoretically limits left-sided conduction system engagement. Purpose To evaluate the feasibility and effectiveness of LBBAP in cardiac amyloidosis. Methods Consecutive patients with CA (both light-chain -AL- or wild-type transtiretin -wtATTr) with a pacing indication for AV conduction disorders were enrolled. Patients underwent baseline echocardiographic examination. LBBAP was achieved by means of stylet-driven leads advanced transeptally (right ventricle (RV) to LV) via dedicated delivery systems, with continuous monitoring of 12-lead electrocardiographic morphology and impedance until a typical QRS morphology in V1 was obtained (usually rSr’ or Sr’). Standard measures for left bundle (LB) capture were used (stimulus to peak R in V6 – S-RV6, V6-V1 interpeak interval, presence of transition in these measures during threshold testing, presence of fascicular signal during spontaneous QRS). Results Between January 2022 and June 2023, among 63 patients undergoing LBBAP, 7 patients (11%) had CA, 2 AL (28%) and 5 (72%) wtATTR. Patients were prevalently old (78±7 y) males (6, 85%); LV mean septal thickness was 17±2 mm (min 16, max 20 mm) and mean LV ejection fraction (LVEF) was 45±6%. Indications were PR prolongation in 3, bradycardic atrial fibrillation and LB branch block (LBBB) in 2, primary LBBB in 1 and chronic RV pacing in 1. Baseline QRS duration was 145±47 ms (QRS<120 ms: 97±15 ms, QRS>120 ms: 182±13 ms). LBBAP success was 100%. Fascicular electrograms were observed in ¾ of patients without LBBB; S-RV6 interval was 74 ±11 ms (³70 ms in 3), RV6-RV1 interpeak interval was 47±9 ms (³ 30 ms in 6 patients). DQRS in baseline broad QRS was -52 ms and +32 ms in narrow. No complications were observed. Over a short follow up of 6 months, an increase in average LVEF was observed (LVEF at 6 months: 51±3%, p<0.05). Conclusions In patients with CA, LBBAP is easily achievable with stylet-driven systems with frequent selective engagement of conduction system. QRS narrowing in baseline broad QRS is significant while QRS broadening in baseline narrow QRS is limited. Early results regarding follow-up of surrogate endpoint such as LVEF are promising.

A CASE REPORT OF AN ASYMPTOMATIC PATIENT WITH TYPE 2 WELLENS’ SYNDROME AND RENAL CARCINOMA

Abstract A 65–year–old male with renal cell carcinoma, previously treated with nephrectomy and recently diagnosed with lung metastases, presented to the cardiology clinic for investigations before starting chemotherapy. He reported a history of ischemic heart disease, a non–ST–elevation myocardial infarction for which he refused coronary angiography in 2005, and a negative maximal stress test for ischemia in 2017. Additionally, the patient reported insulin–dependent type 2 diabetes mellitus and well–controlled arterial hypertension. The patient was referred for a cardiological evaluation due to a reported short–term rhythmic heartbeat without other cardiological symptoms. Cardiological parameters were stable (blood pressure: 140/95 mmHg; heart rate: 42 bpm, and oxygen saturation without oxygen supplementation: 98%). Physical examination was normal. Laboratory investigations did not show elevated levels of high–sensitivity troponin I, and only signs of mild chronic kidney disease were observed. The initial ECG showed sinus bradycardia with deeply inverted T–waves in the extended anterior area (Fig. 1), which were not present in an ECG performed one month earlier. There was no reported chest pain. An echocardiogram examination demonstrated hypertensive heart disease with marked hypokinesia of the mid–apical portion of the anterior wall and anterior interventricular septum, together with a moderate reduction in global systolic function (LV ejection fraction: 40%). The patient was hospitalized, and underwent coronary angiography the following day. He had a low–risk score (GRACE: 95 pts) As shown in Fig. 2, there was evidence of long sub–occlusive stenosis of the proximal part of the anterior descending coronary artery that was treated with angioplasty and a single drug–eluted stent placement, resulting in a good angiographic result. After the procedure, there was a rapid recovery of regional kinetics but a slower normalization of the electrocardiographic morphology (Fig. 3). Comment Wellens‘ syndrome identifies a particular subtype of unstable angina characterized by the appearance of ischemic changes on the ECG,. The clinical risk assessment of this subgroup of patients with ACS, apparently having a more benign prognosis due to their definition as unstable angina with a low GRACE risk score, potentially has an evolution toward a large myocardial infarction if not promptly diagnosed.

Are ECG findings overlooked in Lyme disease, which is the cause of AV complete block?

Objective: Lyme disease-associated carditis and conduction disturbances are well known, but there is insufficient data in the literature on the effects of Lyme disease on global electrocardiography (ECG) morphology. This study aims to evaluate the effects of Lyme disease on ECG morphology. Method: The study included 48 consecutive patients who were hospitalised in our centre with a diagnosis of AV complete block between 01 January 2020 and 01 August 2023. Patients were divided into two groups as Lyme positive (Group 1) and negative (Group 2). Afterwards, demographic and laboratory data of the patients were recorded. All ECG data including ventricular rate, atrial rate, QRS duration, P wave dispersion (Pd), QTc dispersion (QTcd), and fragmented QRS were analysed from routine electrocardiograms obtained using standard extremity and chest leads at 25 mm/s and 10 mm/mV. The data obtained were compared between the groups. Results: The mean age was 72.5(51.7-82.2) in group 1 and 74(68-79.7) in group 2, respectively. There was no significant difference between them (P= 0.593). In the study population, the ratio of males and females was similar between the groups. In ECG evaluation of the study population, no significant difference was found between atrial rate, ventricular rate, QRS duration, QTc duration and frequency of fragmented QRS (p

Registered nurses' knowledge and interpretation of ECG rhythms: A cross-sectional study.

Electrocardiographic (ECG) monitoring and recording are seen as the most commonly used non-invasive diagnostic tool to identify cardiac arrhythmia and myocardial damage in the clinical setting. There is an expectation that critical care nurses are ideally trained to interpret abnormalities and morphology in the ECG more proficiently than nurses from general ward areas. However, the ability to interpret and recognise ECG abnormalities is dependent on which critical care area nurses are currently working in and their level of experience. The aim of this study was to investigate registered nurses' knowledge in being able to identify and interpret select electrocardiographic rhythms. This was a cross-sectional study that evaluated registered nurses' knowledge of electrocardiogram rhythm identification and interpretation. A convenience sample of 105 registered nurses currently enrolled in a 2-year Master's programme leading to critical care specialism and advanced practice nurse award were recruited. A 20-item multiple choice questionnaire that provided examples of electrocardiogram rhythm (n=14) abnormalities and rhythm abnormalities caused by electrolyte disturbances (n=6) RESULTS: The study included registered nurses from critical care and general ward areas. The overall results were poor with only 55% of questions answered correctly. Coronary care nurses scored the highest in identifying ECG rhythms (12/20 ± 1.58; p < .001). When ECG abnormalities associated with electrolyte imbalances were analysed, both groups were unable to identify the effects of hypokalaemia and hypomagnesaemia effectively (p = .748). Length of time as a registered nurse (r = -0.304, p = .002) and length of time in current work environment were weakly correlated (r = -0.328, p = .001). Having a critical care background showed a positive relationship with nursing knowledge of ECG rhythm identification (r = 0.614, p < .001). The results of this study demonstrate that nurses have a poor knowledge of ECG rhythm identification and interpretation, a consistent finding from other work. A possible solution is a revamp of education and training associated with ECG recognition and morphology. Monitoring and assessing ECG morphology provide important details about cardio-electroconductive stability, especially with fluctuations in serum electrolyte levels seen in critical illness or trauma. For this, critical nurses must improve their proficiency through education/training or internal quality improvement activities in detecting abnormalities associated with ECG changes beyond those most easily recognizable rhythms such as atrial fibrillation or ventricular tachycardia.

Ventricular Tachycardia.

This scenario was developed to educate emergency medicine residents on the diagnosis and management of ventricular tachycardia (VT) that is refractory to single dose anti-arrhythmic management. Electrical storm, defined as three or more episodes of sustained VT, ventricular fibrillation, or appropriate shocks from an implantable cardioverter defibrillator within 24 hours,1 has a mortality rate up to 14% in the first 48 hours.2 Ventricular tachycardia may present in a heterogenous fashion, not only with stable versus unstable clinical presentations, but also with different electrocardiographic morphologies and etiologies.1 Understanding how to rapidly diagnose, treat, and utilize second or third-line treatments is vital in the setting of refractory ventricular tachycardia rather than relying on the success of first-line agents. Appreciation for what medications are readily available in your crash cart and medication dispensing cabinet is critical for timely management for refractory ventricular tachycardia. At the conclusion of the simulation session, learners will be able to: 1) identify the different etiologies of VT, including structural heart disease, acute ischemia, and acquired or congenital QT syndrome; 2) describe confounding factors of VT, such as electrolyte abnormalities and sympathetic surge; 3) describe how to troubleshoot an unsuccessful synchronized cardioversion, including checking equipment connections, increasing delivered energy, and changing pad placement; 4) compare and contrast treatments of VT based on suspected underlying etiology; 5) describe reasons to activate the cardiac catheterization lab other than occlusive myocardial infarction; and 6) identify appropriate disposition of the patient to the cardiac catheterization lab. This session was conducted using high-fidelity simulation, followed by a debriefing session and lecture on the diagnosis, differential diagnosis, and management of VT. Debriefing methods may be left to the discretion of participants, but the authors have utilized advocacy-inquiry techniques. This scenario may also be run as an oral board case. Our residents are provided a survey at the completion of the debriefing session so they may rate different aspects of the simulation, as well as provide qualitative feedback on the scenario. The local institution's simulation center's electronic feedback form is based on the Center of Medical Simulation's Debriefing Assessment for Simulation in Healthcare (DASH) Student Version Short Form3 with the inclusion of required qualitative feedback if an element was scored less than a 6 or 7. Twelve learners completed a feedback form. This session received 6 and 7 scores (consistently effective/very good and extremely effective/outstanding, respectively) other than three isolated 5 scores. The lowest average score was 6.67 for "Before the simulation, the instructor set the stage for an engaging learning experience." The highest average score was 7 for "The instructor helped me see how to improve or how to sustain good performance." The form also includes an area for general feedback about the case at the end. Illustrative examples of feedback include: "Excellent care and debrief." Specific scores are available upon request. This is a cost-effective method for reviewing VT diagnosis and management. The case may be modified for appropriate audiences, such as describing what medications may be readily available in a free-standing emergency department or pre-hospital setting. Medical simulation, ventricular tachycardia, cardiac emergencies, dysrhythmias, cardiology, emergency medicine.

Implications of the anatomy of papillary muscle connections for mapping and ablation of focal ventricular arrhythmias

Ventricular arrhythmias (VAs) originating from papillary muscles (PAPs) can be challenging when targeted with catheter ablation. Reasons may include premature ventricular complex pleomorphism, structurally abnormal PAPs, or unusual origins of VAs from PAP-myocardial connections (PAP-MYCs). The purpose of this study was to correlate PAP anatomy with mapping and ablation of PAP VAs. In a series of 43 consecutive patients with frequent PAP arrhythmias referred for ablation, the anatomy and structure of PAPs and VA origins were analyzed using multimodality imaging. Successful ablation sites were analyzed for location on the PAP body or a PAP-MYC. In a total of 17 of 43 patients (40%), VAs originated from a PAP-MYC (in 5 of 17 patients, the PAP inserted into the mitral valve anulus); and in 41 patients, VAs originated from a PAP body. VAs from a PAP-MYC more often had delayed R-wave transition than did other PAP VAs (69% vs 28%; P < .001). Patients with failed procedures had more PAP-MYCs (24.8 ± 8 PAP-MYCs per patient vs 16 ± 7 PAP-MYCs per patient; P < .001). Multimodality imaging identifies anatomic details of PAPs that facilitate mapping and ablation of VAs. In more than a third of patients with PAP VAs, VAs originate from connections between PAPs and the surrounding myocardium or between other PAPs. VA electrocardiographic morphologies are different when VAs originate from PAP-connection sites as compared with VAs originating from the PAP body.

Validation of left bundle branch pacing criteria: are we really doing it well?

Abstract Funding Acknowledgements Type of funding sources: None. Background Left bundle branch (LBB) area pacing (LBBAP) has been widely adopted for an increasing number of antibradycardia and CRT procedures worldwide. Two different types of capture have been described during LBBAP: left ventricular septal myocardial capture (LVSP) or direct LBB capture (LBBP). Nevertheless, electrocardiographic diagnosis of LBBAP remains one of the challenges of modern conduction system pacing because there is a big overlap between both electrocardiographic morphologies. Among the new ECG-based criteria, the R wave peak time in lead V6 (V6-RWPT) and V6-V1 interpeak interval seem to be the most practical ones and have been widely adopted. However, their performance have never been validated in an external population. Purpose We aim to validate the reported criteria V6-RWTP and the V6-V1 interpeak interval in an our population. Methods Single-center study involving all consecutive patients who received LBBAP. LBBP was defined according to the presence of QRS morphology transition criteria during decremental pacing. The performance of binary decision rules was described using sensitivity (SN) and specificity (SP). The performance of V6-RWPT and V6-V1 interpeak interval in discriminating between LBBP and LVSP was assessed using the receiver operating characteristic (ROC) curve. Results A total of 188 patients with intended LBBAP were screened. Successful LBBAP was achieved in 174 (92.5%). Only 71 patients with confirmed LBBP by the QRS morphology transition criteria were included to analyse the performance of V6-RWPT and V6-V1 interpeak interval. The V6-RWPT was 75.7±9.6 ms for LBBP tracings and 94.4±10.1 ms for LVS tracings (p&amp;lt;0.001), and V6-V1 interpeak interval was 41.9±12.1 ms for LBB capture and 25.6±8.7 ms for LVS capture (p&amp;lt;0.001). The average difference in V6-RWPT for the transition from LBBP to LVSP was 16.5±5.2 ms. The ROC curves for the differential diagnosis of LBBP and LVS capture (Figure 1, which compares them with those from the original articles) showed a diagnostically optimal V6-RWPT value for the differentiation of LBBP and LVS capture of 83 ms (SN of 80.3% and SP of 91.1%). A SP of 100% for the diagnosis of LBBP was achieved with a cut-off value of 79.5 ms (SN 69.0%). For the V6-V1 interpeak interval, the diagnostically optimal value for the differentiation of LBBP was 33.5 ms (SN of 77.1% and SP of 84.6%). A SP of 100% for the diagnosis of LBBP was obtained with a cut-off value &amp;gt;44 ms (SN 37.1%) (Figure 2). Conclusions Our study comprises an external validation of the proposed ECG-based criteria for LBB capture. We found a nearly absolute concordance with the originally reported V6-RWPT and V6-V1 interpeak interval cut-off values. Only the V6-RWPT cut-off value with 100% specificity differed from the initially reported in the general cohort. Thus, the V6-RWPT and V6-V1 interpeak interval criteria seem to be consistent and emerge as practical and easily reproducible surrogates of the QRS transition criteria.

Catheter ablation of ventricular premature depolarizations originating from the mid interventricular septum: Significance of electrocardiographic morphology for predicting origin

Ventricular premature depolarizations (VPDs) originating from the mid interventricular septum (IVS) adjacent to the atrioventricular annulus between the His bundle and the coronary sinus ostium (mid IVS VPDs) have not been characterized. The aim of this study was to investigate the electrophysiological characteristics of mid IVS VPDs. Thirty-eight patients with mid IVS VPDs were enrolled. VPDs were divided into different types according to precordial transition of the electrocardiogram (ECG) and QRS morphology in lead V1. Four types of VPDs were divided. The precordial transition zone appeared earlier and earlier from types 1 to 4. The notch in lead V1 moved gradually backward, and its amplitude gradually became higher, resulting in the transition from left to right bundle branch block morphology in lead V1 from types 1 to 4. Based on activation and pace mapping, ablation response, and 3830 electrode pacing morphology in the mid IVS, the 4 types of ECG morphology corresponded to an origin in the right endocardial side, right/mid intramural region, left intramural region, and left endocardial side of the mid IVS, respectively. An intramural origin was identified for 50% of VPDs. Eighty-nine percent of mid IVS VPDs could be eliminated. Bilateral ablation (waiting for delayed efficacy) or bipolar ablation was sometimes needed for intramural VPDs. Mid IVS VPDs were found to have unique electrophysiological characteristics. The ECG characteristics of mid IVS VPDs were important in terms of prediction of its exact origin, the choice of ablation method, and the likelihood of treatment being successful.

Electrocardiography and heart rate variability in Göttingen Minipigs: Impact of diurnal variation, lead placement, repeatability and streptozotocin-induced diabetes

BackgroundThe Göttingen Minipig is widely used in preclinical research and safety pharmacology, but standardisation of porcine electrocardiography (ECG) is lacking. The aim of this study was to investigate diurnal effects, change over time and choice of lead on ECG morphology and heart rate variability (HRV) in healthy and streptozotocin (STZ) induced diabetic Göttingen Minipigs. MethodsDiabetes was experimentally induced using STZ in 11 Göttingen Minipigs (DIA). Seven controls (CON) were included. 24-h ECG was recorded at baseline and four months. Morphological parameters (QRS and T wave duration, P- and T-wave amplitude, PR and QT (Bazett's (QTcb) or Fridericia (QTcf) correction) intervals and ST segment), presence of cardiac arrhythmias, heart rate (HR) and HRV (time and frequency domain) were analysed. ResultsFour months after induction, DIA had decreased P-wave amplitude (P < 0.0001) and T-wave duration (P = 0.017), compared to CON. QTcb was lower in DIA, but not in CON. Both groups had decreased HR (P < 0.0001) and QRS duration (lead II, P = 0.04) and length of PR-segment increased (lead I and II, P < 0.01) while selected HRV parameters also increased (all P < 0.01). Time of day influenced HR, QRS duration, PR segment, ST segment, T- and P-wave amplitude and some parameters of HRV. Inter- and intra-observer variability of morphological measurements was low (<6%). ConclusionECG parameters were influenced by time setting, diurnal variation and lead. Some ECG and HRV changes were found in diabetic minipigs four months after STZ induction. The findings underline the need for standardisation of ECG and HRV in Göttingen Minipigs.

The History of Atrial Flutter Electrophysiology, from Entrainment to Ablation: A 100-Year Experience in the Precision Electrocardiology.

Atrial flutter (AFL) is a regular supraventricular reentrant tachycardia generating a continuous fluttering of the baseline electrocardiography (ECG) at a rate of 250 to 300 beats per minute. AFL is classified based on the involvement of the cavo-tricuspid isthmus in the circuit. The "isthmic" (or type 1) AFL develops entirely in the right atrium; this circuit is commonly activated in a counter-clockwise direction, generating the common sawtooth ECG morphology in the inferior leads (slow descendent-fast ascendent). AFL can be nonisthmus dependent (type 2), often presenting with faster atrial rate and most commonly a left atrial location.

Electrocardiographic Characteristics and Catheter Ablation of Ventricular Arrhythmias Originating From the Moderator Band in Children.

AimsTo investigate the electrocardiographic (ECG) characteristics and catheter ablation of ventricular arrhythmias (VAs) originating from the moderator band (MB) in children.MethodsA total of six children who had VAs originating from the MB—as confirmed by electrophysiological study—and who underwent catheter ablation between January 2016 and December 2020 were retrospectively reviewed. During the procedure, a three-dimensional electroanatomic mapping system was used to facilitate three-dimensional anatomical reconstruction, mapping and ablation. Patients' clinical characteristics, ECG features and procedural data were collected and analyzed.ResultsThe mean age was 8.4 ± 2.6 years (range: 5.3–11 years) and mean weight was 27.7 ± 11.4 kg (range: 17–47 kg). Four patients presented with frequent premature ventricular contraction (PVC), one patient presented with frequent PVC and non-sustained ventricular tachycardia, and one patient presented with sustained monomorphic ventricular tachycardia. The QRS duration averaged 126.3 ± 4.6 ms. In all patients, the VAs had left bundle branch block QRS with left superior frontal plane axes, rapid downstrokes of the QRS in the precordial leads, and late precordial transitions (>V4). During the same period, 10 cases of VAs originated from the posterior-lateral wall of the tricuspid annulus, with a mean QRS duration of 152.8 ± 6.4 ms. Compared to that, VAs of MB origin have narrower QRS widths, downstroke slopes in the inferior lead, sharper downstroke slopes in the precordial lead, and smaller R-wave amplitudes in the V6 lead. All patients experienced immediate ablation success with activations earlier than QRS by 26.0 ± 3.5 ms, and no procedural complications occurring. Only one case had recurrent PVC during a follow-up period ranging from 6 to 36 months.ConclusionMB VAs in children have distinctive ECG morphology and electrophysiological characteristics. Catheter ablation using a three-dimensional electroanatomic mapping system is safe and effective in these patients.

Rotors anchored by refractory islands drive torsades de pointes in an experimental model of electrical storm.

Electrical storm (ES) is a life-threatening emergency in patients at high risk of ventricular tachycardia/ventricular fibrillation (VF), but the pathophysiology and molecular basis are poorly understood. The purpose of this study was to explore the electrophysiological substrate for experimental ES. A model was created by inducing chronic complete atrioventricular block in defibrillator-implanted rabbits, which recapitulates QT prolongation, torsades des pointes (TdP), and VF episodes. Optical mapping revealed island-like regions with action potential duration (APD) prolongation in the left ventricle, leading to increased spatial APD dispersion, in rabbits with ES (defined as ≥3 VF episodes/24 h). The maximum APD and its dispersion correlated with the total number of VF episodes invivo. TdP was initiated by an ectopic beat that failed to enter the island and formed a reentrant wave and perpetuated by rotors whose centers swirled in the periphery of the island. Epinephrine exacerbated the island by prolonging APD and enhancing APD dispersion, which was less evident after late Na+ current blockade with 10 μM ranolazine. Nonsustained ventricular tachycardia in a non-ES rabbit heart with homogeneous APD prolongation resulted from multiple foci with an electrocardiographic morphology different from TdP driven by drifting rotors in ES rabbit hearts. The neuronal Na+-channel subunit NaV1.8 was upregulated in ES rabbit left ventricular tissues and expressed within the myocardium corresponding to the island location in optically mapped ES rabbit hearts. The NaV1.8 blocker A-803467 (10 mg/kg, intravenously) attenuated QT prolongation and suppressed epinephrine-evoked TdP. A tissue island with enhanced refractoriness contributes to the generation of drifting rotors that underlies ES in this model. NaV1.8-mediated late Na+ current merits further investigation as a contributor to the substrate for ES.

ELECTROCARDIOGRAPHIC CHARACTERISTICS WITH LEFT BUNDLE BRANCH AREA PACING: A SINGLE CENTER PROSPECTIVE STUDY

<h3>BACKGROUND</h3> Pure left bundle branch (LBB) capture should result in typical RBBB (rsR') morphology. However, numerous paced QRS morphologies are observed during LBB area pacing (LBBAP). There are limited papers describing the various electrocardiographic (ECG) morphologies seen with LBBAP. Objective: To evaluate the various ECG characteristics encountered in LBBAP. <h3>METHODS AND RESULTS</h3> Patients referred for pacemaker implantation between 08/2019-01/2021 were considered for LBBAP. LBBAP was performed by implantation of a Medtronic 3830 lead 2 cms distal to His and confirmed by previously published criteria. Paced QRS morphology and QRS axis was analyzed. Baseline, ECG, and implantation characteristics are summarized in table 1. Of 264 LBBAP ECGs, the most common morphology seen during unipolar tip pacing was an incomplete RBBB pattern (qR) in V1 in 165 (69.9%) patients. rSR' pattern was seen in 9 (3.2%) and a narrow QS pattern in 60 (21.5%) patients. <h3>CONCLUSION</h3> Various ECG morphologies may be encountered during successful LBB area capture and are associated with similar QRSd, pacing characteristics and short-term lead performance. These morphologies are due to capture of various structures (RV or LV septum, capture of LBB, LPF +/- RBB) and are likely due to virtual-electrode effect.

B-PO05-037 ELECTROCARDIOGRAPHIC CHARACTERISTICS WITH LEFT BUNDLE BRANCH AREA PACING: A SINGLE CENTER PROSPECTIVE STUDY

Pure left bundle branch (LBB) capture should result in typical RBBB (rsR’) morphology. However, numerous paced QRS morphologies are observed during LBB area pacing (LBBAP). There are limited papers describing the various electrocardiographic (ECG) morphologies seen with LBBAP. To evaluate the various ECG characteristics encountered in LBBAP. Patients referred for pacemaker implantation between 02/2019-02/2021 were considered for LBBAP. LBBAP was performed by implantation of a Medtronic 3830 lead 2 cms distal to His and confirmed by previously published criteria. If unsuccessful, lead was repositioned distally and inferiorly on the septum to capture the left posterior fascicle (LPF). Paced QRS morphology and QRS axis was analyzed. Baseline, ECG, and implantation characteristics are summarized in table 1. Of 274 LBBAP ECGs, the most common morphology seen during unipolar tip pacing was an incomplete RBBB pattern (qR) in V1 in 131 (48%) patients. rSR’ pattern was seen in 38 (14%) and a narrow QS pattern in 34 (12.5%) patients. qR or rsR’ with left axis deviation, i.e., LPF capture was noted in 69 (25%) patients. One patient exhibited monophasic R in lead V1. Unipolar ring pacing resulted in wide QS in all patients due to RV septal capture only. Various ECG morphologies may be encountered during successful LBB area capture and are associated with similar QRSd, pacing characteristics and short-term lead performance. These morphologies are due to capture of various structures (RV or LV septum, capture of LBB, LPF +/- RBB) and are likely due to virtual-electrode effect.

Relationship of paced left bundle branch pacing morphology with anatomic location and physiological outcomes

Left bundle branch pacing (LBBP) is an emerging physiological pacing modality. However, little is known about pacing at different locations on the left bundle branch (LBB). The purpose of this study was to explore pacing and physiological characteristics associated with different LBBP locations. The study included 68 consecutive patients with normal unpaced QRS duration and successful LBBP implantation. Patients were divided into 3 groups according to the paced QRS complex as left bundle branch trunk pacing (LBTP), left posterior fascicular pacing (LPFP), or left anterior fascicular pacing (LAFP). Electrocardiographic (ECG) characteristics, pacing parameters, and fluoroscopic localization were collected and analyzed. There were 17 (25.0%), 35 (51.5%), and 16 (23.5%) patients in the LBTP, LPFP, and LAFP groups, respectively. All subgroups had relatively narrow paced QRS complex (128.6 ± 9.1 ms vs 133.7 ± 11.2 ms vs 134.8 ± 9.6 ms; P = .170), fast left ventricular activation (70.4 ± 9.0 ms vs 70.6 ± 10.2 ms vs 71.0 ± 9.0 ms; P = .986), as well as low and stable pacing thresholds. Delayed right ventricular activation and interventricular dyssynchrony were similar between groups. Fluoroscopic imaging indicated that the lead tip was located most commonly in the basal-middle region of the septum (67.7%), and this was independent of paced QRS morphology group (88.2% vs 57.1% vs 68.8%; P = .106). Pacing at different sites of the LBB resulted in similar intraventricular and interventricular electrical synchrony in patients with an intact conduction system. Fluoroscopic imaging alone could not predict specific LBBP paced ECG morphology.

Practical Approaches to Catheter Ablation of Idiopathic Ventricular Arrhythmias

In this review, we provide a practical approach to the catheter ablation of idiopathic focal ventricular arrhythmias (VAs) by summarizing the electrocardiographic (ECG) characteristics, mapping strategies, and ablation techniques for each of the major types of idiopathic VAs. We identify special considerations to be taken when treating specific forms of idiopathic VAs with catheter ablation that can increase success rates and reduce complications. Insights on ECG morphologies of VAs have led to novel criteria that can aid in accurate identification and localization of VA sites of origin. Advancements in mapping catheters and software as well as the use of intracardiac echocardiography have allowed for more precise mapping and ablation of arrhythmias arising from complex cardiac structures. Idiopathic VAs occurring in patients without overt structural heart disease can be categorized into four groups on the basis of anatomic location: (1) outflow tract VAs (which include the right ventricular outflow tract, left ventricular outflow tract, and left ventricular summit; (2) fascicular VAs; (3) papillary muscle VAs; and (4) annular VAs. Knowledge of the ECG characteristics of idiopathic VAs and the three-dimensional anatomy surrounding their sites of origin can guide pre-procedure planning, prioritization of cardiac regions for mapping, and approach for ablation.

Impact of electrocardiographic morphology on clinical outcomes in patients with non-ST elevation myocardial infarction receiving coronary angiography and intervention: a retrospective study.

BackgroundThe impact of electrocardiography (ECG) morphology on clinical outcomes in patients with non-ST segment elevation myocardial infarction (NSTEMI) receiving percutaneous coronary intervention (PCI) is unknown. This study investigated whether different ST morphologies had different clinical outcomes in patients with NSTEMI receiving PCI.MethodsThis retrospective study analyzed record-linked data of 362 patients who had received PCI for NSTEMI between January 2008 and December 2010. ECG revealed ST depression in 67 patients, inverted T wave in 91 patients, and no significant ST-T changes in 204 patients. The primary endpoint was long-term all-cause mortality. The secondary endpoint was long-term cardiac death and non-fatal major adverse cardiac events.ResultsCompared to those patients whose ECG showed an inverted T wave and non-specific ST-T changes, patients whose ECG showed ST depression had more diabetes mellitus, advanced chronic kidney disease (CKD) and left main artery disease, as well as more in-hospital mortality, cardiac death and pulmonary edema during hospitalization. Patients with ST depression had a significantly higher rate of long-term total mortality and cardiac death. Finally, multiple stepwise Cox regression analysis showed that an advanced Killip score, age, advanced CKD, prior percutaneous transluminal coronary angioplasty and ST depression were independent predictors of the primary endpoint.ConclusionsAmong NSTEMI patients undergoing coronary angiography, those with ST depression had more in-hospital mortality and cardiac death. Long-term follow-up of patients with ST depression consistently reveals poor outcomes.

Electrocardiographic morphology during left bundle branch area pacing: Characteristics, underlying mechanisms, and clinical implications.

In this study, we investigated the characteristics and underlying mechanisms of the electrocardiographic (ECG) morphology during left bundle branch area pacing (LBBAP), which have not been systematically described. Patients with indications for permanent cardiac pacing underwent LBBAP attempts. The ECGs of patients with confirmed left bundle branch (LBB) capture were compared with those of individuals with right bundle branch block (RBBB) on 12-lead ECG. Intracardiac electrograms recorded during implantation were analyzed in all patients who underwent pacing. LBBAP was successfully achieved in 87.5% (56/64) of patients. The QRS morphologies in lead V1 during LBBAP, which typically demonstrated Qr (60.7%), qR (19.6%), rSR' (7.1%), or QS (12.5%) patterns, differed from those of native RBBB, which featured rsR' (57.5%), M shape (23.7%), or monophasic R patterns (18.7%). The terminal R' wave duration in lead V1 was significantly shorter during LBBAP than during native RBBB (51 ± 12ms vs 85 ± 19ms, p<0.001). LBB potentials were recorded in 66.1% (37/56) of the LBBAP patients. No significant differences in ECG characteristics were found between LBBAP with and without recorded LBB potentials. The presence of bundle branch block during LBBAP significantly prolonged QRS duration, R wave peak time, and terminal R' wave duration in lead V1 . LBBAP-ECG patterns are characterized by a shorter terminal R' wave duration in lead V1 compared with that of native RBBB configurations. Bundle branch conduction integrity has an impact on ECG characteristics during LBBAP.

Electrocardiographic Comparison Between Artificial Cardiac Stimulation of Apex, Septum and Right Ventricular Outflow Tract

Background: Ventricular pacing is detrimental to cardiac function, with more deleterious effects when it is apical, widening the QRS complex, so the best cardiac pacing site is still being sought. Objective: To compare, by electrocardiographic measurements, the duration of QRS complexes at different cardiac stimulation sites, from the medical records of patients with pacemakers, who attended the external cardiac stimulation consultation at Monte Sinai Hospital in Cuenca-Ecuador. Methods: A total of 323 patients were retrospectively analyzed from January 2011 to November 2018, classifying them by electrocardiographic morphology as apical, low septal, middle septal and right ventricular outflow tract (RVOT) stimulation. The duration of stimulated QRS complexes was quantified using digital software that allows such measurement and stores all records. Subsequently, the comparison of the means of the different stimulation sites was performed using ANOVA. Results: The average age was 73.6 years; 56.03% corresponded to males; 49.84% had apical stimulation, 21.67% middle septal, 15.78% RVOT, 12.69% low septal. At the end of the QRS complex measurements, an average on apex of 179.94 ms, on low septum of 172.56 ms, an average on middle septum of 153.89 ms and on RVOT 171.66 ms were obtained. When comparing these values with the average ANOVA, the duration of the QRS stimulated in the middle septum was shorter than the other sites, being statistically significant (p &lt; 0.001). Conclusion: Cardiac pacing in the middle septum is a viable alternative, which results in shorter QRS complex duration, therefore, better synchronization of myocardial contraction, also avoiding the deleterious effects of apical stimulation.

Head orientation and electrode placement potentially influence fetal scalp ECG waveform.

BackgroundFetal monitoring based on electrocardiographic (ECG) morphology is obtained from a single unipolar fetal scalp electrode. Ideally, it should be obtained from multiple leads, as ECG waveform depends on alignment between electrode and electrical heart axis. This alignment is unknown in fetuses. Besides, fetuses are surrounded by conductive media, which may influence ECG waveform. We explored the influence of electrode position and head orientation on ECG waveforms of unipolar and bipolar scalp ECGs recorded in air and in conductive medium.MethodsWe recorded ECGs in one adult subject at five different scalp positions in five different head orientations both in dry and immersed conditions. The ratio between T-amplitude and QRS-amplitude (T/QRS ratio) of unipolar and bipolar scalp ECGs was determined and compared between all conditions.ResultsIn the dry condition, we observed in the unipolar leads little to no difference between different electrode positions (maximal T/QRS difference 0.00–0.01) and minor differences between head orientations (0.02–0.03), whereas bipolar leads showed no recognizable ECG signal at all. During the immersed condition, we found variation in the unipolar leads, both between electrode positions (maximal T/QRS difference 0.02–0.05) and between head orientations (0.03–0.06). Bipolar leads showed different ECG signals in contrasting head orientations.ConclusionsBoth unipolar and bipolar scalp lead-derived ECG waveforms are influenced by electrode position and head orientation when the subject is submerged in a conductive medium. Fetal monitoring based on single scalp lead ECG waveform might be suboptimal, as it lacks correction for fetal head orientation and electrode position.