Longitudinal ECG changes in tetralogy of Fallot and association with surgical repair.

Background: ECG abnormalities have been linked to adverse changes in right ventricular (RV) morphology and poor clinical outcomes in repaired Tetralogy of Fallot (rTOF). Our aim was to describe how ECG changes progress in early and intermediate follow-up and whether types of surgical strategy at the time of primary repair affected these changes. Methods: We studied patients with rTOF born 2000-2018 operated at our institution. Seven time points in relation to primary repair, follow-up, and pulmonary valve replacement (PVR) were identified. Patients correct with valve sparing repair (VSR), trans-annular patch (TAP) including with a monocusp valve (TAP + M) and with at least 3 ECGs were included. PQ interval, QRS duration, dispersion, and fragmentation, QTc duration and dispersion, JTc as well as presence of a right bundle branch block (RBBB) were analyzed. Medical records were reviewed for demographic and surgical data. Results: Two hundred nineteen patients with 882 ECGs were analyzed with a median follow-up time of 12.3 years (8.4, 17) with 41 (19%) needing PVR during the study period. QRS duration increased at time of primary repair to discharge from 66 msec (IQR 12) to 129 msec (IQR 27) (p < 0.0001) and at 1- and 6- year follow-up but showed only a modest and temporary decrease after PVR. QTc increased at the time of primary repair as well as prior to PVR. PQ interval showed a small increase at the time of primary repair, was at its highest prior to PVR and decreased with PVR. Type of surgical repair affected mainly QTc and JTc and was consistently longer in the TAP + M group until PVR. In VSR, QTc and JTc were prolonged initially compared to TAP but were similar after 1 year. After PVR, there were no differences in adverse ECG changes between surgical groups. Conclusions: PQ interval and QRS duration best correspond to the assumed volume load whereas the relationship with QTc and JTc is more complex, suggesting that these represent more complex remodeling of the myocardium. Before PVR, QTc and JTc are longer in the TAP + M group which may be due to a longer surgical incision.

Echocardiographic and electrocardiographic findings in Irish Wolfhounds eating high-pulse or low-pulse diets.

BACKGROUND: Apparently healthy dogs of various breeds eating nontraditional, high-pulse diets can have larger left ventricular diameter, lower systolic function, and more ventricular premature complexes (VPCs) compared with dogs eating traditional, low-pulse diets. It is unknown whether Irish Wolfhounds eating high-pulse diets have similar cardiac abnormalities. HYPOTHESIS/OBJECTIVES: To compare electrocardiographic and echocardiographic findings between Irish Wolfhounds eating high- or low-pulse diets. ANIMALS: Ninety-seven Irish Wolfhounds. METHODS: Retrospective study of Irish Wolfhounds that had echocardiography performed at dog shows between October 2018 and May 2021. Demographic information, echocardiographic measurements, cardiac rhythm (1-minute lead II rhythm strip), and main diet were recorded retrospectively. Diets were classified as high-pulse or low-pulse based on the presence and location of pulses (peas, lentils, chickpeas, or dry beans) on the ingredient list. RESULTS: Thirty-five of 97 Irish Wolfhounds (36%) were eating high-pulse diets and 62 of 97 (64%) were eating low-pulse diets. There were no significant differences between diet groups in echocardiographic measurements. A significantly higher percentage of dogs in the high-pulse diet group (6/35 [17%]) had VPCs compared with those in the low-pulse diet group (1/62 [2%]; effect size = 0.15 [95% confidence interval: 0.004-0.31]; P = .005). CONCLUSIONS AND CLINICAL IMPORTANCE: In this retrospective study of apparently healthy Irish Wolfhounds, high-pulse diets were associated with a higher prevalence of VPCs which could represent early cardiac abnormalities.

Electrocardiographic predictors of response to sacubitril/valsartan therapy in heart failure with reduced ejection fraction.

BACKGROUND: Sacubitril/valsartan (SV) is currently recommended as a first-line therapy in patients with heart failure and reduced ejection fraction (HFrEF) due to its significant clinical and prognostic benefit; however, not all patients respond to therapy and predictors of clinical response to SV remain under-studied. AIMS: To identify electrocardiographic (ECG) predictors of response to SV therapy in HFrEF patients. METHODS: A retrospective analysis of a hospital heart failure registry was undertaken. Consecutive HFrEF patients (New York Heart Association class II-III) on maximal-dose SV were studied. Response to SV was defined as ≥10% relative improvement in left ventricular ejection fraction (LVEF) at 3-months post-maximal-dose therapy. Pre-therapy ECGs were retrospectively analyzed for axes and standard wave and interval durations. Logistic regression was used to estimate odds ratios and 95% confidence intervals for associations between predictors and therapeutic response. Backward stepwise regression was employed to develop a parsimonious model. RESULTS: P-wave duration (PWD) 100-120 ms, PWD >120 ms, and QTc >460 ms were associated with response to SV on univariate analysis: OR 18.00 (4.45-122.90), 5.00 (1.47-20.42), and 3.10 (1.18-9.22), respectively. The preferred model that included the former two predictors in combination with pre-therapy creatinine, mineralocorticoid receptor antagonist use, and LVEF was highly selective (area under the ROC curve = 0.868). CONCLUSIONS: Prolongation of both PWD and QTc interval on baseline ECG in HFrEF patients is predictive of therapeutic response to maximal-dose SV therapy and may indicate early cardiac remodeling that is highly amenable to reversal.

Forward problem of electrocardiography based on cardiac source vector orientations.

To localize the unusual cardiac activities non-invasively, one has to build a prior forward model that relates the heart, torso, and detectors. This model has to be constructed to mathematically relate the geometrical and functional activities of the heart. Several methods are available to model the prior sources in the forward problem, which results in the lead field matrix generation. In the conventional technique, the lead field assumed the fixed prior sources, and the source vector orientations were presumed to be parallel to the detector plane with the unit strength in all directions. However, the anomalies cannot always be expected to occur in the same location and orientation, leading to misinterpretation and misdiagnosis. To overcome this, the work proposes a new forward model constructed using the VCG signals of the same subject. Furthermore, three transformation methods were used to extract VCG in constructing the time-varying lead field to steer to the orientation of the source rather than just reconstructing its activities in the inverse problem. In addition, the unit VCG loop of the acute ischemia patient was extracted to observe the changes compared to the normal subject. The abnormality condition was achieved by reducing the depolarization time by 15ms. The results involving the unit vectors of VCG demonstrated the anisotropic nature of cardiac source orientations, providing information about the heart's electrical activity.

Study of Attenuation Correction Using a Cardiac Dynamic Phantom: Synchronized Time-Phase-Gated Attenuation Correction Method.

In cardiac nuclear medicine examinations, absorption in the body is the main factor in the degradation of the image quality. The Chang and external source methods were used to correct for absorption in the body. However, fundamental studies on attenuation correction for electrocardiogram (ECG)-synchronized CT imaging have not been performed. Therefore, we developed and improved an ECG-synchronized cardiac dynamic phantom and investigated the synchronized time-phase-gated attenuation correction (STPGAC) method using ECG-synchronized SPECT and CT images of the same time phase. Methods: As a basic study, SPECT was performed using synchronized time-phase-gated (STPG) SPECT and non-phase-gated (NPG) SPECT. The attenuation-corrected images were, first, CT images with the same time phase as the ECG waveform of the gated SPECT acquisition (with CT images with the ECG waveform of the CT acquisition as the reference); second, CT images with asynchronous ECG; third, CT images of the 75% region; and fourth, CT images of the 40% region. Results: In the analysis of cardiac function in the phantom experiment, left ventricle ejection fraction (heart rate, 11.5%-13.4%; myocardial wall, 49.8%-55.7%) in the CT images was compared with that in the STPGAC method (heart rate, 11.5%-13.3%; myocardial wall, 49.6%-55.5%), which was closer in value to that of the STPGAC method. In the phantom polar map segment analyses, none of the images showed variability (F (10,10) < 0.5, P = 0.05). All images were correlated (r = 0.824-1.00). Conclusion: In this study, we investigated the STPGAC method using a SPECT/CT system. The STPGAC method showed similar values of cardiac function analysis to the CT images, suggesting that the STPGAC method accurately reconstructed the distribution of blood flow in the myocardial region. However, the target area for attenuation correction of the heart region was smaller than that of the whole body, and changing the gated SPECT conditions and attenuation-corrected images did not affect myocardial blood flow analysis.

Different degrees of anterior displacement of QRS complex.

Electrocardiogram of a patient affected by hypertrophic cardiomyopathy showed normal PR and QRS intervals and signs of left ventricular hypertrophy. In leads I,V5 and V6 the initial q waves were absent. A subsequent electrocardiogram revealed the appearance of prominent anterior QRS forces expressed by a change from rS to R pattern in leads V2 and V3 with a tall R wave in V2. PR and QRS intervals and QRS axis remained substantially unchanged. Other electrocardiograms showed day-to-day variations of the anterior displacement of QRS complex. The different degrees of anterior displacement appear to be an expression of an underlying left septal fascicular block, but a diagnosis cannot be made with certainty.

Ventricular injury in acute left circumflex occlusion: Exploration using precordial bipolar leads and regional vectorcardiograms.

BACKGROUND: Precordial Bipolar Leads (PBLs) provide new electrocardiographic information derived from standard 12­lead ECG recordings. OBJECTIVES: To explore the usefulness of PBLs in patients with acute circumflex coronary artery (CxCA) occlusion. METHODS: Twelve patients undergoing elective percutaneous transluminal coronary angioplasty (PTCA) were studied before and after acute CxCA occlusion and their data were processed with new methods based on PBLs. RESULTS: The findings were: 1. In right PBL V2-V1, a strong systolic current of injury moving in the left-to-right direction coexists with a strong right-to-left current of injury displayed in left standard unipolar precordial leads (V4, V5 and V6). 2. Ischemic changes lead to a significant increase (approximately 10 ms) in the QRS duration in different leads, although changes in the QRS loop rotation and folding were absent. 3. In the transverse, sagittal, and frontal planes, superimposing two PBLs and the corresponding Regional VCG facilitates the location of the J-point. 4. In the Regional VCGs of this group of patients, J-point and ST segment shifts produced an image that reminds the Greek letter omega (Ω). 5. The currents of injury flowing in opposite directions could result in electrical cancellation that minimizes ECG changes in the standard 12­lead recordings. CONCLUSIONS: Computerized processing of digital, standard 12­lead ECG recordings, provides new valuable diagnostic data in patients with acute CxCA occlusion. The loops revealed important information related to systolic currents of injury. Because these methods use routine 12­lead ECG data, the procedure is based only in software applications. CONDENSED ABSTRACT: Twelve patients undergoing PTCA were studied before and after acute CxCA occlusion and their data were processed with the new methods based on Precordial Bipolar Leads (PBLs) to explore their usefulness. The results showed strong systolic currents of injury in different and sometimes opposite directions in the right-to-left axis and ischemic alterations in the time and amplitude of the QRS waves. The superimposition of two-dimensional coordinates planes (x-y, x-z or z-y) helped to locate the J-point and to display the Regional VCG omega sign (Ω) of myocardial injury. In conclusion, computerized processing of digital ECG data provides new diagnostic information in patients with acute CxCA occlusion.

Prognostic significance of beat-to-beat variability of spatial heterogeneity of repolarization analyzed from a 5-minute resting electrocardiogram in coronary artery disease.

BACKGROUND: Data on the prognostic significance of temporal variability of spatial heterogeneity of electrocardiographic repolarization in coronary artery disease (CAD) are limited. OBJECTIVE: The purpose of this study was to evaluate the prognostic value of temporal variability of T-wave morphology analyzed from a 5-minute resting electrocardiogram in CAD. METHODS: The standard deviation (SD) of T-wave morphology dispersion (TMD-SD) and the SD of total cosine R-to-T were analyzed on a beat-to-beat basis from a 5-minute period of the standard resting 12-lead electrocardiogram obtained before the clinical stress test in 1702 patients with angiographically verified CAD and well-preserved left ventricular function. RESULTS: During an average of 8.7 ± 2.2 years of follow-up, 60 patients experienced sudden cardiac death/arrest (SCD/SCA) (3.5%), 69 patients nonsudden cardiac death (NSCD) (4.1%), and 161 patients noncardiac death (9.5%). TMD-SD was significantly higher in patients who experienced SCD/SCA than in other patients (1.72 ± 2.00 vs 1.12 ± 1.75; P = .01) and higher in patients who succumbed to NSCD than in other patients (1.57 ± 1.74 vs 1.12 ± 1.76; P = .04), but it did not differ significantly between patients who experienced noncardiac death and those without such an event (1.16 ± 1.42 vs 1.14 ± 1.79; P = .86). In the Cox multivariable hazards model, TMD-SD retained its significant association with the risk of SCD/SCA (hazard ratio 1.119; 95% confidence interval 1.015-1.233; P = .024) but not with the risk of NSCD (hazard ratio 1.089; 95% confidence interval 0.983-1.206; P = .103). CONCLUSION: TMD-SD is independently associated with the long-term risk of SCD/SCA in patients with CAD.

Accurate diagnosis of apical hypertrophic cardiomyopathy using explainable advanced ECG analysis.

BACKGROUND AND AIMS: Typical electrocardiogram (ECG) features of apical hypertrophic cardiomyopathy (ApHCM) include tall R waves and deep or giant T-wave inversion in the precordial leads, but these features are not always present. The ECG is used as the gatekeeper to cardiac imaging for diagnosis. We tested whether explainable advanced ECG (A-ECG) could accurately diagnose ApHCM. METHODS: A-ECG analysis was performed on standard resting 12-lead ECGs in patients with ApHCM (n = 75 overt, n = 32 relative [<15mm hypertrophy]), a subgroup of which underwent cardiovascular magnetic resonance, n = 92), and comparator subjects (n = 2449), including healthy volunteers (n = 1672), patients with coronary artery disease (n = 372), left ventricular electrical remodelling (n = 108), ischemic (n = 114) or non-ischemic cardiomyopathy (n = 57), and asymmetrical septal hypertrophy (ASH) HCM (n = 126). RESULTS: Multivariable logistic regression identified four A-ECG measures that together discriminated ApHCM from other diseases with high accuracy (area under the receiver operating characteristics curve (AUC) [bootstrapped 95% confidence interval] 0.982 [0.965-0.993]. Linear discriminant analysis also diagnosed ApHCM with high accuracy (AUC 0.989 [0.986-0.991]). CONCLUSION: Explainable A-ECG has excellent diagnostic accuracy for ApHCM, even when the hypertrophy is relative, with A-ECG analysis providing incremental diagnostic value over imaging alone. The electrical (ECG) and anatomical (wall thickness) disease features do not completely align, suggesting future diagnostic and management strategies may incorporate both features.

Performance of ECG-Derived Digital Biomarker for Screening Coronary Occlusion in Resuscitated Out-of-Hospital Cardiac Arrest Patients: A Comparative Study between Artificial Intelligence and a Group of Experts.

Acute coronary syndrome is a significant part of cardiac etiology contributing to out-of-hospital cardiac arrest (OHCA), and immediate coronary angiography has been proposed to improve survival. This study evaluated the effectiveness of an AI algorithm in diagnosing near-total or total occlusion of coronary arteries in OHCA patients who regained spontaneous circulation. Conducted from 1 July 2019 to 30 June 2022 at a tertiary university hospital emergency department, it involved 82 OHCA patients, with 58 qualifying after exclusions. The AI used was the Quantitative ECG (QCG™) system, which provides a STEMI diagnostic score ranging from 0 to 100. The QCG score's diagnostic performance was compared to assessments by two emergency physicians and three cardiologists. Among the patients, coronary occlusion was identified in 24. The QCG score showed a significant difference between occlusion and non-occlusion groups, with the former scoring higher. The QCG biomarker had an area under the curve (AUC) of 0.770, outperforming the expert group's AUC of 0.676. It demonstrated 70.8% sensitivity and 79.4% specificity. These findings suggest that the AI-based ECG biomarker could predict coronary occlusion in resuscitated OHCA patients, and it was non-inferior to the consensus of the expert group.

Reference ranges for ambulatory heart rate measurements in a middle-aged population.

BACKGROUND: Elevated heart rate (HR) predicts cardiovascular disease and mortality, but there are no established normal limits for ambulatory HR. We used data from the Swedish CArdioPulmonary Imaging Study to determine reference ranges for ambulatory HR in a middle-aged population. We also studied clinical correlates of ambulatory HR. METHODS: A 24-hour ECG was registered in 5809 atrial fibrillation-free individuals, aged 50-65 years. A healthy subset (n=3942) was used to establish reference values (excluding persons with beta-blockers, cardiovascular disease, hypertension, heart failure, anaemia, diabetes, sleep apnoea or chronic obstructive pulmonary disease).Minimum HR was defined as the lowest 1-minute HR. Reference ranges are reported as means±SDs and 2.5th-97.5th percentiles. Clinical correlates of ambulatory HR were analysed with multivariable linear regression. RESULTS: The average mean and minimum HRs were 73±9 and 48±7 beats per minute (bpm) in men and 76±8 and 51±7 bpm in women; the reference range for mean ambulatory HR was 57-90 bpm in men and 61-92 bpm in women. Average daytime and night-time HRs are also reported. Clinical correlates, including age, sex, height, body mass index, physical activity, smoking, alcohol intake, diabetes, hypertension, haemoglobin level, use of beta-blockers, estimated glomerular filtration rate, per cent of predicted forced expiratory volume in 1 s and coronary artery calcium score, explained <15% of the interindividual differences in HR. CONCLUSION: Ambulatory HR varies widely in healthy middle-aged individuals, a finding with relevance for the management of patients with a perception of tachycardia. Differences in ambulatory HR between individuals are largely independent of common clinical correlates.

Brugada phenocopy vs. Brugada syndrome: Delineating the differences for optimal diagnosis and management.

Brugada syndrome (BrS) is a genetic disorder known for its characteristic electrocardiogram (ECG) patterns and increased risk of sudden cardiac death. Brugada phenocopy (BrP) presents similar ECG patterns but is distinguished by its reversible nature when the underlying conditions are resolved. This article delineates the intricacies of BrP, emphasizing its etiology, clinical presentation, diagnosis, treatment, and prognosis. The article categorizes BrP based on various underlying causes, including metabolic disturbances, myocardial infarction, and mechanical compression, among others. It also underscores the critical importance of differentiating BrP from BrS to avoid misdiagnosis and inappropriate treatment, such as unnecessary implantation of cardioverter-defibrillators. The reversible aspect of BrP underlines the necessity for an etiology-specific approach to treatment, which not only prevents cardiac death but also highlights the significance of understanding the dynamic nature of ECG patterns. Through an exploration of case studies and current research, this review advocates for increased awareness and further investigation into BrP. It aims to enhance the diagnostic accuracy and management strategies, thereby improving the prognosis for patients presenting with Brugada-like ECG patterns. The review culminates in a call for further research to close existing knowledge gaps and improve patient outcomes.

ECG signal quality in intermittent long-term dry electrode recordings with controlled motion artifacts.

Wearable long-term monitoring applications are becoming more and more popular in both the consumer and the medical market. In wearable ECG monitoring, the data quality depends on the properties of the electrodes and on how they interface with the skin. Dry electrodes do not require any action from the user. They usually do not irritate the skin, and they provide sufficiently high-quality data for ECG monitoring purposes during low-intensity user activity. We investigated prospective motion artifact-resistant dry electrode materials for wearable ECG monitoring. The tested materials were (1) porous: conductive polymer, conductive silver fabric; and (2) solid: stainless steel, silver, and platinum. ECG was acquired from test subjects in a 10-min continuous settling test and in a 48-h intermittent long-term test. In the settling test, the electrodes were stationary, whereas both stationary and controlled motion artifact tests were included in the long-term test. The signal-to-noise ratio (SNR) was used as the figure of merit to quantify the results. Skin-electrode interface impedance was measured to quantify its effect on the ECG, as well as to leverage the dry electrode ECG amplifier design. The SNR of all electrode types increased during the settling test. In the long-term test, the SNR was generally elevated further. The introduction of electrode movement reduced the SNR markedly. Solid electrodes had a higher SNR and lower skin-electrode impedance than porous electrodes. In the stationary testing, stainless steel showed the highest SNR, followed by platinum, silver, conductive polymer, and conductive fabric. In the movement testing, the order was platinum, stainless steel, silver, conductive polymer, and conductive fabric.

Implementing a clinical scientist-led screening clinic for hypertrophic and dilated cardiomyopathies.

BACKGROUND: The burden of screening for inherited cardiac conditions on health services grows ever larger, with each new diagnosis necessitating screening of additional family members. Screening these usually asymptomatic, low-risk individuals is currently performed by consultant cardiologists, consuming vital clinic resources that could otherwise be diverted to sicker patients requiring specialist consultant input. Clinical scientists now constitute a highly skilled and often underutilised group of individuals with training in areas such as clinical evaluation, 12-lead electrocardiography (ECG) interpretation, and echocardiography. These skills place them in a unique position to offer a full screening evaluation in a single consultation. The aim of this study was to implement and evaluate a novel clinical scientist-led screening clinic for first-degree relatives of patients with hypertrophic cardiomyopathy (HCM) and dilated cardiomyopathy (DCM). The clinical scientist-led screening clinic was established at a London tertiary centre to allow review of asymptomatic, first-degree relatives of patients with a confirmed diagnosis of HCM or DCM, independent of a cardiology consultant. Patients were evaluated with history, examination, ECG, and echocardiography, with further investigations if deemed necessary. A retrospective review was performed of the first 200 patients seen in the clinic. RESULTS: Of the 200 individuals reviewed between September 2019 and July 2022, 99 had a proband with HCM and 101 a proband with DCM. Overall, 169 individuals (85%) revealed normal screenings and were discharged. Thirty-one individuals (15.5%), all asymptomatic, revealed ECG changes and/or significant echocardiographic findings. Of these, 21 individuals (10.5% of the total cohort) were subsequently diagnosed with a cardiomyopathy or early phenotypic changes consistent with a cardiomyopathy (11 with HCM and 10 with DCM). These individuals were referred on to an inherited cardiac conditions consultant clinic for regular follow-up. Overall, 179 consultant clinic appointments were saved which could instead be allocated to patients requiring specialist consultant input. CONCLUSIONS: This is the first description of a clinical scientist-led screening clinic for first-degree relatives of patients with HCM and DCM. The findings demonstrate that implementation of such a service into routine clinical practice is feasible, effective, safe, and can free up capacity in consultant clinics for patients requiring specialist input.

Use of portable single-lead electrocardiogram device as an alternative for QTc monitoring in critically ill patients.

PURPOSE: Acquired QT prolongation is frequent and leads to a higher mortality rate in critically ill patients. KardiaMobile 1L® (KM1L) is a portable, user-friendly single lead, mobile alternative to conventional 12-lead electrocardiogram (12-L ECG) that could be more readily available, potentially facilitating more frequent QTc assessments in intensive care units (ICU); however, there is currently no evidence to validate this potential use. METHODS: We conducted a prospective diagnostic test study comparing QT interval measurement using KM1L with conventional 12-L ECG ordered for any reason in patients admitted to an ICU. We compared the mean difference using a paired t-test, agreement using Bland-Altman analysis, and Lin's concordance coefficient, numerical precision (proportion of QT measurements with <10 ms difference between KM1L and conventional 12-L ECG), and clinical precision (concordance for adequate discrimination of prolonged QTc). RESULTS: We included 114 patients (61.4% men, 60% cardiovascular etiology of hospitalization) with 131 12-L ECG traces. We found no statistical difference between corrected QT measurements (427 ms vs. 428 ms, p = .308). Lin's concordance coefficient was 0.848 (95% CI 0.801-0.894, p = .001). Clinical precision was excellent in males and substantial in females (Kappa 0.837 and 0.781, respectively). Numerical precision was lower in patients with vasoactive drugs (-13.99 ms), QT-prolonging drugs (13.84 ms), antiarrhythmic drugs (-12.87 ms), and a heart rate (HR) difference of ≥5 beats per minute (bpm) between devices (-11.26 ms). CONCLUSION: Our study validates the clinical viability of KM1L, a single-lead mobile ECG device, for identifying prolonged QT intervals in ICU patients. Caution is warranted in patients with certain medical conditions that may affect numerical precision.

Real-world validation of smartphone-based photoplethysmography for rate and rhythm monitoring in atrial fibrillation.

AIMS: Photoplethysmography- (PPG) based smartphone applications facilitate heart rate and rhythm monitoring in patients with paroxysmal and persistent atrial fibrillation (AF). Despite an endorsement from the European Heart Rhythm Association, validation studies in this setting are lacking. Therefore, we evaluated the accuracy of PPG-derived heart rate and rhythm classification in subjects with an established diagnosis of AF in unsupervised real-world conditions. METHODS AND RESULTS: Fifty consecutive patients were enrolled, 4 weeks before undergoing AF ablation. Patients used a handheld single-lead electrocardiography (ECG) device and a fingertip PPG smartphone application to record 3907 heart rhythm measurements twice daily during 8 weeks. The ECG was performed immediately before and after each PPG recording and was given a diagnosis by the majority of three blinded cardiologists. A consistent ECG diagnosis was exhibited along with PPG data of sufficient quality in 3407 measurements. A single measurement exhibited good quality more often with ECG (93.2%) compared to PPG (89.5%; P < 0.001). However, PPG signal quality improved to 96.6% with repeated measurements. Photoplethysmography-based detection of AF demonstrated excellent sensitivity [98.3%; confidence interval (CI): 96.7-99.9%], specificity (99.9%; CI: 99.8-100.0%), positive predictive value (99.6%; CI: 99.1-100.0%), and negative predictive value (99.6%; CI: 99.0-100.0%). Photoplethysmography underestimated the heart rate in AF with 6.6 b.p.m. (95% CI: 5.8 b.p.m. to 7.4 b.p.m.). Bland-Altman analysis revealed increased underestimation in high heart rates. The root mean square error was 11.8 b.p.m. CONCLUSION: Smartphone applications using PPG can be used to monitor patients with AF in unsupervised real-world conditions. The accuracy of AF detection algorithms in this setting is excellent, but PPG-derived heart rate may tend to underestimate higher heart rates.

Deep terminal negative of the P wave in V1 and incidence of ischemic stroke: The atherosclerosis risk in communities (ARIC) study.

BACKGROUND: Deep terminal negative of the P wave in V1 (DTNPV1) is a marker of left atrial remodeling. We aimed to evaluate the association of DTNPV1 with incident ischemic stroke. METHODS: The Atherosclerosis Risk in Communities study is a prospective community-based cohort study. All participants at visit 4 (1996-1998) except those with prevalent stroke, missing covariates, and missing or uninterpretable ECG were included. DTNPV1 was defined as the absolute value of the depth of the terminal negative phase >100 µV in the presence of biphasic P wave in V1. Association between DTNPV1 as a time-dependent exposure variable and incident ischemic stroke was evaluated. The accuracy of the prediction model consisting of DTNPV1 and CHA2DS2-VASc variables in predicting ischemic stroke was analyzed. RESULTS: Among 10,605 participants (63 ± 6 years, 56% women, 20% Black), 803 cases of ischemic stroke occurred over a median follow-up of 20.19 years. After adjusting for demographics, DTNPV1 was associated with an increased risk of stroke (HR 1.96, [95% CI 1.39-2.77]). After further adjusting for stroke risk factors, use of aspirin and anticoagulants, and time-dependent atrial fibrillation, DTNPV1 was associated with a 1.50-fold (95% CI 1.06-2.13) increased risk of stroke. When added to the CHA2DS2-VASc variables, DTNPV1 did not significantly improve stroke prediction as assessed by C-statistic. However, there was improvement in risk classification for participants who did not develop stroke. CONCLUSION: DTNPV1 is significantly associated with higher risk of ischemic stroke. Since DTNPV1 is a simplified electrocardiographic parameter, it may help stroke prediction, a subject for further research.

Evaluation of the introduction of a single-lead ECG device and digital cardiologist consultation platform among general practitioners in the Netherlands.

AIM: To evaluate the use of a single-lead electrocardiography (1L-ECG) device and digital cardiologist consultation platform in diagnosing arrhythmias among general practitioners (GPs). BACKGROUND: Handheld 1L-ECG offers a user-friendly alternative to conventional 12-lead ECG in primary care. While GPs can safely rule out arrhythmias on 1L-ECG recordings, expert consultation is required to confirm suspected arrhythmias. Little is known about GPs' experiences with both a 1L-ECG device and digital consultation platform for daily practice. METHODS: We used two distinct methods in this study. First, in an observational study, we collected and described all cases shared by GPs within a digital cardiologist consultation platform initiated by a local GP cooperative. This GP cooperative distributed KardiaMobile 1L-ECG devices among all affiliated GPs (n = 203) and invited them to this consultation platform. In the second part, we used an online questionnaire to evaluate the experiences of these GPs using the KardiaMobile and consultation platform. FINDINGS: In total, 98 (48%) GPs participated in this project, of whom 48 (49%) shared 156 cases. The expert panel was able to provide a definitive rhythm interpretation in 130 (83.3%) shared cases and answered in a median of 4 min (IQR: 2-18). GPs responding to the questionnaire (n = 43; 44%) thought the KardiaMobile was of added value for rhythm diagnostics in primary care (n = 42; 98%) and easy to use (n = 41; 95%). Most GPs (n = 36; 84%) valued the feedback from the cardiologists in the consultation platform. GPs experienced this project to have a positive impact on both the quality of care and diagnostic efficiency for patients with (suspected) cardiac arrhythmias. Although we lack a comprehensive picture of experienced impediments by GPs, solving technical issues was mentioned to be helpful for further implementation. More research is needed to explore reasons of GPs not motivated using these tools and to assess real-life clinical impact.

Tunable Q-factor wavelet transform based identification of diabetic patients using ECG signals.

Diabetes is a chronic health condition that is characterized by increased levels of glucose (sugar) in the blood. It can have harmful effects on different parts of the body, such as the retina of the eyes, skin, nervous system, kidneys, and heart. Diabetes affects the structure of electrocardiogram (ECG) impulses by causing cardiovascular autonomic dysfunction. Multi-resolution analysis of the input ECG signal is utilized in this paper to develop a machine learning-based system for the automated detection of diabetic patients. In the first step, the input ECG signal is decomposed into sub-bands utilizing the tunable Q-factor wavelet transform (TQWT) technique. In the second step, four entropy-based characteristics are evaluated from each SB and elected using the K-W test method. To develop an automatic diabetes detection system, selected features are given as input with 10-fold validation to a SVM classifier using various kernel functions. The 3rd sub-band of TQWT with the Coarse Gaussian kernel function kernel of the SVM classifier yields a classification accuracy of 91.5%. In the same dataset, the comparative analysis demonstrates that the proposed method outperforms other existing methods.