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Ballistocardiography (BCG) is a noninvasive modality for detecting cardiac activity. This study developed a robust atrial fibrillation (AF) detection algorithm using multiple BCG sensors at different locations and evaluated the improvement in accuracy by combining data from multiple sensors. We recorded the BCG using a piezoelectric rubber sheet sensor and an electrocardiogram in 84 participants (29 with AF and 55 without AF) in the supine position. Four BCGs (BCG1–4) were obtained using sensors placed from the head to the lumbar region (0, 25, 45, and 65 cm from the head). The BCG signals were divided into 32 s blocks and analyzed. After applying fast Fourier transform, we input the power spectrum, focusing on frequencies below 10 Hz, into machine learning (ML) classifiers to distinguish between AF and non-AF with parameter tuning. The AdaBoost classifier for BCG2 exhibited the highest accuracy (0.88) among the ML models for each sensor. When we applied the classifier to other BCGs, it achieved accuracies of 0.92, 0.73, and 0.78 for BCG1, 3, and 4, respectively. The combined model using multiple sensors exhibited an accuracy of 0.92. The optimized model for BCG2 was robust against shifts in the sensor toward the head and lumbar directions. A combined assessment using multiple sensors improved performance.

Magnetocardiography (MCG) provides a non-invasive, contactless technique for evaluating the magnetic fields generated by cardiac electrical activity, offering unique spatial insights into cardiac electrophysiology. However, conventional MCG systems depend on superconducting quantum interference devices that require cryogenic cooling and magnetic shielded environments, posing considerable impediments to widespread clinical adoption. In this study, we present a novel MCG system utilizing a high-sensitivity, wide-dynamic-range magnetoresistive sensor array operating at room temperature. To mitigate environmental interference, identical sensors were deployed as reference channels, enabling adaptive noise cancellation (ANC) without the need for traditional magnetic shielding. MCG recordings were obtained from 40 healthy participants, with signals processed using ANC, R-peak-synchronized averaging, and Bayesian spatial signal separation. This approach enabled the reliable detection of key cardiac components, including P, QRS, and T waves, from the unshielded MCG recordings. Our findings underscore the feasibility of a cost-effective, portable MCG system suitable for clinical settings, presenting new opportunities for noninvasive cardiac diagnostics and monitoring.

PurposeClinical implication of local impedance (LI) for radiofrequency (RF) ablation has not been fully established. This study aimed to investigate this point using IntellaNav MiFi OITM catheter.MethodsLI and generator impedance drops (ΔLI and ΔGI) were evaluated in excised porcine hearts (N = 16) during RF applications at a range of powers (30 and 50 W), contact forces (5–40 g), and durations (10–180 s) using perpendicular or parallel catheter orientation. Additionally, temporal LI changes were assessed.ResultsOf the 240 lesions without steam pops (92.3%), ΔLI showed better correlations with lesion surface area (ρ = 0.55 vs 0.36, P = 0.004), maximum depth (ρ = 0.53 vs 0.14, P < 0.001), and lesion volume (ρ = 0.64 vs 0.23, P < 0.001) than ΔGI. Furthermore, %LI-drop (ΔLI/initial LI) demonstrated stronger correlations with lesion surface area (ρ = 0.60 vs 0.55, P < 0.001), maximum depth (ρ = 0.57 vs 0.53, P < 0.001), and volume (ρ = 0.69 vs 0.64, P < 0.001) than ΔLI. Parallel catheter orientation improved correlation of ΔLI with lesion surface area (ρ = 0.63 vs 0.40, P = 0.015) and depth (ρ = 0.68 vs 0.45, P = 0.008) and created a larger surface lesion (36.3[29.2–42.7] mm2 vs 28.8[21.6–34.2] mm2, P < 0.001) than the perpendicular. LI of the lesions significantly differed between baseline, immediately after RF, and 5 min after (P < 0.01). LI reaching plateau, larger initial LI, ΔLI, and %LI-drop, and larger RF power and longer duration were observed in pop lesions (P < 0.05).Conclusions%LI-drop demonstrated a better correlation with lesion size than ΔLI. LI may be used as an additional parameter to predict lesion size and steam pops. Temporal variation and catheter orientation should be considered to interpret LI.

Background The innovative peak frequency mapping facilitates the quantification of electrogram sharpness. However, reference values for normal atrial tissue are currently undefined. In this study, we explored the distribution of peak frequency and omnipolar peak-to-peak voltage (V-max) in a normal heart. Methods Twenty-two patients with structurally normal heart were included. Either the right atrium (RA) and superior vena cava (SVC) or the left atrium (LA) and pulmonary veins (PVs) were mapped during sinus rhythm. Results In total, 13,654 points in the RA and 4143 points in the SVC from 15 patients and 4662 points in the LA and 2761 points in PVs from 7 patients were analyzed. The correlation between peak frequency and V-max was weak ( R  = 0.223). The median peak frequency was larger in the SVC than in the RA (441 [358–524] Hz vs. 358 [291–441] Hz, P  < 0.0001) and in PVs than in the LA (346 [253–441] Hz vs. 323 [262–397] Hz, P  < 0.0001). Conversely, the median V-max was smaller in the SVC than in the RA (1.96 [0.77–3.75] mV vs. 4.11 [2.10–6.83] mV, P  < 0.0001) and in PVs than in the LA (1.16 [0.33–3.17] mV vs. 4.42 [2.63–6.84] mV, P  < 0.0001). More than 95% of peak frequencies were > 174 Hz in the RA and > 185 Hz in the LA, and > 95% of V-maxes were > 0.52 and > 1.07 mV in the RA and LA, respectively. Conclusion Given the limited correlation between peak frequency and V-max, and recognizing their potential to provide distinct information, they can be used complementarily. Employing these parameters to extract varied insights can provide comprehensive understandings of tissue characteristics. Graphical abstract

Background Although artificial intelligence (AI) has been developed to identify patients with paroxysmal atrial fibrillation (PAF) during sinus rhythm, information on its variability remains limited. We evaluated the reproducibility and effect of recording condition on the estimation of AF risk using an electrocardiography (ECG) machine equipped with an AI‐based program. Methods We extracted two ECG data from a single ECG test in 149 patients to evaluate reproducibility within 4 min. We also recorded ECG signals under 12 conditions (standard, two conditions shifting precordial electrodes, five conditions moving limb electrodes to the torso, three conditions contaminating noise, and reproducibility over 15 min) in 30 participants to evaluate changes from the standard. The results of the AF risk estimation are expressed at four levels. Results The rate of participants within one level of error was 95% for reproducibility within 4 min and 87% for reproducibility over 15 min. Shifting the precordial electrodes upward or downward and replacing the left leg electrode with the torso electrode frequently caused a two‐ or three‐level change. In clinical information, increased brain natriuretic peptide tended to increase the variability. Conclusions The AF risk estimated by the AI‐based program exhibited temporal variability. Shifting the precordial electrodes influenced AI‐based AF risk estimation. The atrial fibrillation (AF) risk estimated by artificial intelligence‐based program installed in electrocardiography (ECG) machine exhibited temporal variability. Reproducibility within one level of error was 100% for the same ECG, 95% for reproducibility within 4 min interval, and 87% for reproducibility over 15 min interval.

BackgroundAlthough ablation energy (AE) and force-time integral (FTI) are well-known active predictors of lesion characteristics, these parameters do not reflect passive tissue reactions during ablation, which may instead be represented by drops in local impedance (LI). This study aimed to investigate if additional LI data improves predicting lesion characteristics and steam pops.MethodsRF applications at a range of powers (30 W, 40 W, and 50 W), contact forces (8 g, 15 g, 25 g, and 35 g), and durations (10–180 s) using perpendicular/parallel catheter orientations were performed in excised porcine hearts (N = 30). The correlation between AE, FTI, and lesion characteristics was examined, and the impact of LI (%LI drop (%LID) defined by the ΔLI divided by the initial LI) was additionally assessed.ResultsThree hundred seventy-five lesions without steam pops were examined. Ablation energy (W × s) and FTI (g × s) showed a positive correlation with lesion depth (ρ = 0.824:P < 0.0001 and ρ = 0.708:P < 0.0001), surface area (ρ = 0.507:P < 0.0001 and ρ = 0.562:P < 0.0001), and volume (ρ = 0.807:P < 0.0001 and ρ = 0.685:P < 0.0001). %LID also showed a positive correlation individually with lesion depth (ρ = 0.643:P < 0.0001), surface area (ρ = 0.547:P < 0.0001), and volume (ρ = 0.733:P < 0.0001). However, the combined indices of AE × %LID (AE multiplied by %LID) and FTI × %LID (FTI multiplied by %LID) provided significantly stronger correlation with lesion depth (ρ = 0.834:P < 0.0001 and ρ = 0.809:P < 0.0001), surface area (ρ = 0.529:P < 0.0001 and ρ = 0.656:P < 0.0001), and volume (ρ = 0.864:P < 0.0001 and ρ = 0.838:P < 0.0001). This tendency was observed regardless of the catheter placement (parallel/perpendicular). AE (P = 0.02) and %LID (P = 0.002) independently remained as significant predictors to predict steam pops (N = 27). However, the AE × %LID did not increase the predictive power of steam pops compared to the AE alone.ConclusionLI, when combined with conventional parameters (AE and FTI), may provide stronger correlation with lesion characteristics.

Abstract PurposeThe size of the distal electrode and the method of measuring local impedance (LI) are different between the IntellaNav MiFi-OI™ (MiFi-OI) and IntellaNav STABLE POINT™ (SP) catheters. We investigated the impact of these differences on LI, efficacy, and safety of radiofrequency (RF) applications.MethodsRF applications at a range of powers (30 W, 40 W, and 50 W), contact forces (10 g and 20 g), and durations (10–120 s) were performed in excised porcine hearts (N = 48). LI variation was defined by δLI-drop (= initial LI − post-RF LI) and %LI-drop (= δLI-drop/initial LI) × 100, and the relationship between lesion characteristics and LI variation was compared.Results A total of 576 lesions were examined. Although absolute δLI-drop during RF applications was significantly larger for the SP than MiFi-OI catheter (47[31–65]ohm for SP vs 37[24–51]ohm for MiFi-OI, p < 0.0001), %LI-drop was similar (23.3 [15.5–30.6]% in SP vs 24.9[17.3–32.5]% in MiFi-OI, p = 0.10). Although lesions produced by both catheters were similarly correlated with LI variation, the SP catheter produced generally larger lesions (depth; 5.0 [3.7–6.1]mm vs 4.7 [3.3–6.0]mm, p = 0.06; surface areas, 46.9 [36.8–58.8]mm2 vs 44.7 [34.3–55.5]mm2, p = 0.02; volume, 321 [165–533]mm3 vs 265[141–471]mm3, p = 0.02). Steam pops were similarly observed with both catheters. In both catheters, %LI-drop was superior to δLI-drop in correlation to lesion size (p < 0.0001) and in predicting steam pops (p < 0.01).ConclusionsAlthough no difference in safety profile is observed between MiFi-OI and SP catheters, the SP catheter produces larger lesions. %LI-drop is superior to δLI-drop in correlation to lesion size and in predicting steam pops as well as in normalizing the difference between catheters.

As situs ambiguus can cause sinus bradycardia in young patients, the best timing for pacemaker implantation is controversial when the patient is a fertile female.As situs ambiguus can cause sinus bradycardia in young patients, the best timing for pacemaker implantation is controversial when the patient is a fertile female.

Abstract PurposeLocal impedance (LI) measurement from an ablation catheter is useful in predicting lesion size and acute success of pulmonary vein isolation (PVI). The LI variation can be described by absolute LI drop (ΔLID) or ΔLID/initial LI (%LID). We evaluated the utility of these parameters in predicting acute lesion durability during PVI using a novel catheter capable of measuring both LI and contact force (CF).MethodsPVI with a targeted CF, power, and duration was performed in 23 consecutive patients with paroxysmal atrial fibrillation. LI was blinded to operators during ablation. Parameters for each RF application were collected and compared for acute successful lesions and gaps.ResultsA total of 1633 RF applications including 97 (5.9%) gap lesions were analyzed. Successful lesions were more frequently observed at non-carinal sites and those with higher contact force, FTI, initial LI, and larger variation of LI and generator impedance (GI). Multivariate analysis demonstrated that absolute GI drop (ΔGID) [OR 1.09 (1.04–1.15), p < 0.001], ΔLID [1.12 (1.09–1.16), p < 0.001], ΔGID/initial GI (%GID) [OR 1.04 (1.01–1.07), p = 0.01], and %LID [OR 1.15 (1.12–1.28), p < 0.001] were significantly associated with successful lesions, and carinal site [OR 0.15(0.09–0.24), p < 0.001] was significantly related to gaps. Both ΔLID and %LID equally predicted the acute durability of lesions during PVI. ΔLID ≥ 24Ω and %LID ≥ 15% at the carina, and ΔLID ≥ 21Ω and %LID ≥ 14% at non-carinal sites significantly predicted acute successful lesions with negative predictive values of 93–99%.ConclusionsBoth ΔLID and %LID were equally useful in predicting acute successful lesions during PVI. Larger cut-off values should be applied to carinal sites.

Background We explore an optimized approach for increasing lesion size using a novel ablation catheter with a surface thermocouple and efficient irrigation in a temperature‐control setting. Methods We conducted radiofrequency applications at various power levels (35 W, 40 W, and 45 W), contact forces (CFs, 10 g/20 g), and durations (60 s/120 s/180 s) in perpendicular/parallel catheter orientations, with normal saline irrigation (NS‐irrigation) and Half NS‐irrigation (HNS‐irrigation) in an ex‐vivo model (Step 1). In addition, we performed applications (35 W/40 W/45 W for 60 s/120 s/180 s in NS‐irrigation and 35 W/40 W for 60 s/120 s/180 s in HNS‐irrigation) in four swine (Step 2), evaluating lesion characteristics and the occurrence of steam pops. Results In Step 1, out of 288 lesions, we observed 47 (16.3%) steam pops, with 13 in NS‐irrigation and 34 in HNS‐irrigation (p = .001). Although steam pops were mostly observed with the most aggressive setting (45 W/180 s, 54%) with NS‐irrigation, they happened in less aggressive settings with HNS irrigation. Lesion size significantly increased with longer‐duration ablation but not with HNS‐irrigation. The optimal %impedance‐drop cutoff to predict steam pops was 20% with a negative‐predictive‐value (NPV) = 95.1% including NS‐ and HNS‐irrigation groups, and 22% with an NPV = 96.1% in NS‐irrigation group. In Step 2, similar to the ex‐vivo model, lesion size significantly increased with longer‐duration ablation but not with HNS‐irrigation. Steam pops were absent with NS‐irrigation (0/35) even with the largest %impedance‐drop reaching 31% at 45 W/180 s. All steam pops were observed with HNS‐irrigation (6/21, 29%). The optimal %impedance‐drop cutoff predicting steam pops was 24% with an NPV = 96.3% including both NS‐ and HNS‐irrigation groups. Conclusions Rather than using HNS‐irrigation, very long‐duration of radiofrequency applications up to 45 W/180 s may be recommended to safely and effectively increase lesion dimensions using this catheter with NS‐irrigation. In both ex‐vivo and in‐vivo studies, the radiofrequency application in a temperature‐controlled setting using a catheter equipped with a surface thermocouple and efficient irrigation demonstrates an increase in lesion size as the ablation duration extends up to 180 s. However, the utilization of half‐normal saline irrigation may not lead to a proportional increase in lesion size, but with more frequent steam‐pops.