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Importance: Sudden death and cardiac arrest frequently occur without explanation, even after a thorough clinical evaluation. Calcium release deficiency syndrome (CRDS), a life-threatening genetic arrhythmia syndrome, is undetectable with standard testing and leads to unexplained cardiac arrest., Objective: To explore the cardiac repolarization response on an electrocardiogram after brief tachycardia and a pause as a clinical diagnostic test for CRDS., Design, Setting, and Participants: An international, multicenter, case-control study including individual cases of CRDS, 3 patient control groups (individuals with suspected supraventricular tachycardia; survivors of unexplained cardiac arrest [UCA]; and individuals with genotype-positive catecholaminergic polymorphic ventricular tachycardia [CPVT]), and genetic mouse models (CRDS, wild type, and CPVT were used to define the cellular mechanism) conducted at 10 centers in 7 countries. Patient tracings were recorded between June 2005 and December 2023, and the analyses were performed from April 2023 to December 2023., Intervention: Brief tachycardia and a subsequent pause (either spontaneous or mediated through cardiac pacing)., Main Outcomes and Measures: Change in QT interval and change in T-wave amplitude (defined as the difference between their absolute values on the postpause sinus beat and the last beat prior to tachycardia)., Results: Among 10 case patients with CRDS, 45 control patients with suspected supraventricular tachycardia, 10 control patients who experienced UCA, and 3 control patients with genotype-positive CPVT, the median change in T-wave amplitude on the postpause sinus beat (after brief ventricular tachycardia at ≥150 beats/min) was higher in patients with CRDS (P < .001). The smallest change in T-wave amplitude was 0.250 mV for a CRDS case patient compared with the largest change in T-wave amplitude of 0.160 mV for a control patient, indicating 100% discrimination. Although the median change in QT interval was longer in CRDS cases (P = .002), an overlap between the cases and controls was present. The genetic mouse models recapitulated the findings observed in humans and suggested the repolarization response was secondary to a pathologically large systolic release of calcium from the sarcoplasmic reticulum., Conclusions and Relevance: There is a unique repolarization response on an electrocardiogram after provocation with brief tachycardia and a subsequent pause in CRDS cases and mouse models, which is absent from the controls. If these findings are confirmed in larger studies, this easy to perform maneuver may serve as an effective clinical diagnostic test for CRDS and become an important part of the evaluation of cardiac arrest.

Background: Continuous monitoring for atrial fibrillation (AF) using photoplethysmography (PPG) from smartwatches or other wearables is challenging due to periods of poor signal quality during motion or suboptimal wearing. As a result, many consumer wearables sample infrequently and only analyze when the user is at rest, which limits the ability to perform continuous monitoring or to quantify AF., Objectives: This study aimed to compare 2 methods of continuous monitoring for AF in free-living patients: a well-validated signal processing (SP) heuristic and a convolutional deep neural network (DNN) trained on raw signal., Methods: We collected 4 weeks of continuous PPG and electrocardiography signals in 204 free-living patients. Both SP and DNN models were developed and validated both on holdout patients and an external validation set., Results: The results show that the SP model demonstrated receiver-operating characteristic area under the curve (AUC) of 0.972 (sensitivity 99.6%, specificity: 94.4%), which was similar to the DNN receiver-operating characteristic AUC of 0.973 (sensitivity 92.2, specificity: 95.5%); however, the DNN classified significantly more data (95% vs 62%), revealing its superior tolerance of tracings prone to motion artifact. Explainability analysis revealed that the DNN automatically suppresses motion artifacts, evaluates irregularity, and learns natural AF interbeat variability. The DNN performed better and analyzed more signal in the external validation cohort using a different population and PPG sensor (AUC, 0.994; 97% analyzed vs AUC, 0.989; 88% analyzed)., Conclusions: DNNs perform at least as well as SP models, classify more data, and thus may be better for continuous PPG monitoring., Competing Interests: Funding Support and Author Disclosures Dr Olgin is supported by a grant from the Mark Cuban Foundation. Dr Tison is supported by National Institutes of Health grant K23HL135274. Dr Avram is supported by the Fonds de la recherche en santé du Québec (grant no. 312758–Montreal Heart Institute Research Centre, the Montreal Heart Institute Foundation). All other authors have reported that they have no relationships relevant to the contents of this paper to disclose., (Copyright © 2024 The Authors. Published by Elsevier Inc. All rights reserved.)

Background: Cardiac implantable electronic devices (CIEDs) are routinely implanted using intravenous drugs for sedation. However, some patients are poor candidates for intravenous sedation., Objective: We present a case series demonstrating the safety and efficacy of a novel, ultrasound-guided nerve block technique that allows for pre-pectoral CIED implantation. The targets are the supraclavicular nerve (SCN) and pectoral nerve (PECS1)., Methods: We enrolled 20 patients who were planned for new CIED implantation. Following US-localization of the SCN and PECS1, local anesthetic (LA) was instilled at least 30-60 min pre-procedure. Successful nerve block was determined if < 5 mL of intraprocedural LA was used, along with lack of sensation with skin and deep tissue pinprick. Optional sedation was offered to patients' pre-procedure if discomfort was reported., Results: Seventeen patients (85%) had a successful periprocedural nerve block, with only three patients exceeding 5 mL of LA. SCN and PECS1 success occurred in 19 (95%) and 18 (90%) patients, respectively. The overall success of nerve block by fulfilling all the criteria was demonstrated in 17 out of 20 patients (85%). Patients who reported no pain (VAS score = 0) were distributed as follows: 13 patients (65%) in the immediate post-procedure interval, 18 patients (90%) at the 1 h post-implant interval, and 14 patients (70%) at the 24 h post- implant interval. The median cumulative VAS score was 0 (IQR = 0 - 1). There were no reported significant adverse effects., Conclusion: SCN and PECS1 nerve blocks are safe and effective for patients undergoing CIED implantation to minimize or eliminate the use of intravenous sedation., (© 2023 The Authors. Pacing and Clinical Electrophysiology published by Wiley Periodicals LLC.)

Competing Interests: Competing interests: None declared.

A woman with type 1 myotonic dystrophy received an implantable cardioverter-defibrillator using a novel combination of ultrasound-guided supraclavicular nerve and pectoral nerve blocks. The entire procedure was completed without any procedural sedation or local anesthetic, and the patient did not experience any pain during or after the procedure. ( Level of Difficulty: Advanced. )., Competing Interests: The authors have reported that they have no relationships relevant to the contents of this paper to disclose., (© 2022 The Authors.)

Aims: Genetic testing is recommended in specific inherited heart diseases but its role remains unclear and it is not currently recommended in unexplained cardiac arrest (UCA). We sought to assess the yield and clinical utility of genetic testing in UCA using whole-exome sequencing (WES)., Methods and Results: Survivors of UCA requiring external defibrillation were included from the Cardiac Arrest Survivor with Preserved Ejection fraction Registry. Whole-exome sequencing was performed, followed by assessment of rare variants in previously reported cardiovascular disease genes. A total of 228 UCA survivors (mean age at arrest 39 ± 13 years) were included. The majority were males (66%) and of European ancestry (81%). Following advanced clinical testing at baseline, the likely aetiology of cardiac arrest was determined in 21/228 (9%) cases. Whole-exome sequencing identified a pathogenic or likely pathogenic (P/LP) variant in 23/228 (10%) of UCA survivors overall, increasing the proportion of 'explained' cases from 9% only following phenotyping to 18% when combining phenotyping with WES. Notably, 13 (57%) of the 23 P/LP variants identified were located in genes associated with cardiomyopathy, in the absence of a diagnosis of cardiomyopathy at the time of arrest., Conclusions: Genetic testing identifies a disease-causing variant in 10% of apparent UCA survivors. The majority of disease-causing variants was located in cardiomyopathy-associated genes, highlighting the arrhythmogenic potential of such variants in the absence of an overt cardiomyopathy diagnosis. The present study supports the use of genetic testing including assessment of arrhythmia and cardiomyopathy genes in survivors of UCA., Competing Interests: Conflict of interest: The authors declare that there is no conflict of interest relevant to this study., (© The Author(s) 2022. Published by Oxford University Press on behalf of European Society of Cardiology.)

Although electrocardiography (ECG) is a fundamental skill for most physicians, trainees have poor diagnostic performance when interpreting ECGs. In this study, we examine a strategy to improve learning ECG interpretation: self-generation of diagnoses during online practice. We randomly assigned medical students and residents to one of 2 ECG interpretation training formats: multiple-choice (MCQ) or self-generation (SG) format, where participants free-text type their diagnosis aided by an autocomplete feature. The training phase consisted of 30 ECGs, after which participants completed an immediate post test and delayed post test (3-4 weeks later). Forty-eight participants completed the training module, 45 completed the immediate post test, and 27 completed the delayed post test. Participants assigned to the SG format scored higher on the immediate post test compared with those who practiced with the MCQ format, with a large effect size (78% vs 57%; d = 0.94; P = 0.02). There was a trend favouring SG on the delayed post test, with a moderate effect size (67% vs 56%; d = 0.65; P = 0.09). However, only 60% of participants completed the delayed post test, which hindered the detection of a statistically significant difference. The SG group made the correct primary diagnosis at a faster rate (32 vs 56 seconds; P < 0.001) but had a lower detection of secondary diagnoses (22 vs 42%; P = 0.007). Practicing ECG interpretation using self-generation of diagnoses improved immediate post test performance and fluency. Replication in other contexts and with other populations is required to confirm our findings and to further study retention., (Copyright © 2021 Canadian Cardiovascular Society. Published by Elsevier Inc. All rights reserved.)

Background and Objectives: The CarePath-CRC electronic clinical decision-making application was designed to assist physicians with evaluation of patients with suspected colorectal cancer (CRC). The physician completes an interactive checklist of evidence-based clinical parameters, and a recommended referral urgency is generated based on the post-test probability of CRC. This study aimed toward validation of the tool in symptomatic patients presenting with rectal bleeding., Methods: The medical records of a sample of patients with histologically confirmed CRC from 2010 to 2014 were reviewed. The CarePath-CRC tool was applied retrospectively to all patients who initially presented with rectal bleeding, to determine its sensitivity for detecting CRC in this population. A generated recommendation of 'immediate referral' (referral ≤24 hours, expected endoscopy ≤2 weeks) or 'urgent referral' (expected consultation and endoscopy ≤4 and ≤8 weeks) was considered a positive test result. An a priori sensitivity of 90% was deemed adequate, based on test characteristics of the tool's individual clinical criteria., Results: The tool was applied to 281 patients. A total of 69 (24.6%) and 211 (75.1%) patients met criteria for immediate and urgent referral, respectively. The remaining patient (0.4%) met criteria for 'possible priority referral', while none met criteria for 'no specific action recommended'. This resulted in a calculated sensitivity of 99.6% (95% confidence interval 98.0 to 99.9%)., Conclusions: The CarePath-CRC tool is sensitive in the prediction of CRC in patients presenting with rectal bleeding. A prospective cohort study is being designed to allow for acquisition of comprehensive test performance characteristics and full validation of the instrument., (© The Author(s) 2019. Published by Oxford University Press on behalf of the Canadian Association of Gastroenterology.)

Cardiac repolarization of black athletes has a distinctive pattern. During an episode of pericarditis, this pattern may evolve into a "pseudonormalized" electrocardiography (ECG). On resolution of the pericardial inflammation, the ECG may return to the normal variant for a black athlete, sounding the alarms of extended disease to the myocardium. Recognizing the normal variant for a black athlete will reduce the need for unnecessary further testing or treatments. The case is discussed in detail.

As medical education evolves, some traditional teaching methods often get forgotten. For generations, the Lewis ladder diagram (LLD) has helped students understand the mechanisms of cardiac arrhythmias and conduction disorders. Similarly, clinicians have used LLDs to communicate their proposed mechanisms to their colleagues and trainees. In this article, we revisit this technique of constructing the LLD and demonstrate this process by describing the mechanisms of various bigeminal rhythms., (© 2019 Wiley Periodicals, Inc.)

Competing Interests: There are no conflicts of interest.

Despite its importance in everyday clinical practice, the ability of physicians to interpret electrocardiograms (ECGs) is highly variable. ECG patterns are often misdiagnosed, and electrocardiographic emergencies are frequently missed, leading to adverse patient outcomes. Currently, many medical education programs lack an organized curriculum and competency assessment to ensure trainees master this essential skill. ECG patterns that were previously mentioned in literature were organized into groups from A to D based on their clinical importance and distributed among levels of training. Incremental versions of this organization were circulated among members of the International Society of Electrocardiology and the International Society of Holter and Noninvasive Electrocardiology until complete consensus was reached. We present reasonably attainable ECG interpretation competencies for undergraduate and postgraduate trainees. Previous literature suggests that methods of teaching ECG interpretation are less important and can be selected based on the available resources of each education program and student preference. The evidence clearly favors summative trainee evaluation methods, which would facilitate learning and ensure that appropriate competencies are acquired. Resources should be allocated to ensure that every trainee reaches their training milestones and should ensure that no electrocardiographic emergency (class A condition) is ever missed. We hope that these guidelines will inform medical education programs and encourage them to allocate sufficient resources and develop organized curricula. Assessments must be in place to ensure trainees acquire the level-appropriate ECG interpretation skills that are required for safe clinical practice., (© 2017 Society of Hospital Medicine.)

Purpose: Cardiac resynchronization therapy (CRT) has been shown to improve left atrial function; however the effect on reverse electrical remodeling has been poorly evaluated. We hypothesized that CRT might induce reverse atrial electrical remodeling manifesting in the surface ECG as a shortening in P-wave duration., Methods: Patients with CRT and more than 92% biventricular pacing at minimum follow-up of 1 year were included in the analysis. Those with prior history of atrial fibrillation (AF) were excluded. Data were recorded for clinical, echocardiographic and ECG variables prior to implant and at least 12 months post implantation. Semiautomatic calipers and scanned ECGs at 300 DPI maximized × 8 were used to measure P-wave duration and diagnose advanced interatrial block (aIAB) during sinus rhythm. The occurrence of AF was assessed through analyses of intracardiac electrograms and clinical presentations., Results: 41 patients were included in the study with mean age of 67.4 ±9.6 years, 71% were male, left atrial diameter 41.1 ± 8.5 mm and LV EF 28.5 ± 6.5%. Over a mean follow up of 55 months, a significant reduction in P-wave duration (142.7 ms vs. 133.1 ms; p < 0.001) was noted. The presence of aIAB was significantly reduced (36% vs. 17%; p = 0.03). The incidence of new onset AF was 36%. Time to AF onset after CRT implantation was not influenced by a reduction in P-wave duration., Conclusion: CRT induces atrial reverse electrical remodeling manifested as a reduction in P-wave duration. Larger studies are needed to determine the impact on AF incidence after CRT implantation., (Copyright © 2017 Elsevier Inc. All rights reserved.)

Corrected carotid systolic flow time (CFTc) has been proposed as a measure of volume status in acutely ill patients. This study endeavors to determine whether the change in CFTc with passive leg raise (PLR) maneuver correlates with volume status changes. Dialysis patients at Kingston General Hospital (Kingston, Canada) underwent point-of-care carotid ultrasonography at the beginning and the end of dialysis. With each measurement, 2 values were recorded: the absolute CFTc, and the difference in CFTc before and after the PLR maneuver. A total of 49 measurements were collected during the study period. CFTc changed with PLR by 5±22milliseconds (2.0%) pre-dialysis and by 40±19milliseconds (13.0%) post-dialysis (P<.0001). Incorporating PLR to the CFTc measurement improved the area under the ROC from 0.64 to 0.91. Particularly, in our sample of patients, a 30milliseconds increase in CFTc with PLR predicted the post-dialysis volume state (LR+=11) whereas an increase of less than 20milliseconds argued against it (LR-=0.079). The assessment of CFTc pre- and post-PLR correlates with intravascular volume changes in patients undergoing dialysis. Alternative to the currently available bedside modalities, this technique is non-invasive, objective, simple to perform at the bedside, and reversible with respect to volume challenge., (Copyright © 2017 Elsevier Inc. All rights reserved.)