Heart rhythm最新文献

Background: Ultra-high-frequency ECG (UHF-ECG) is a non-invasive tool visualizing the ventricular activation sequence. It was never compared to other methods of dyssynchrony assessment in bradycardia patients.

Objective: We aimed to compare UHF-ECG interventricular electrical dyssynchrony with interventricular mechanical dyssynchrony measured by echocardiography in patients with right ventricular (RVP) or conduction system pacing (CSP).

Methods: Fifty-three patients with advanced atrio-ventricular conduction disease and preserved ventricular systolic function were prospectively assigned to RVP (n=32) or CSP (n=21). Interventricular mechanical dyssynchrony (IVMD) was measured as a time difference between LV and RV pre-ejection periods. Interventricular e-DYS was software calculated as the time difference between activation in V1 and V7 chest electrodes using UHF-ECG.

Results: The median age of patients was 75 years, and both groups had similar clinical characteristics. Baseline IVMD and interventricular e-DYS were similar in the entire population (-2 [-8, 5] ms; resp. -1 [-6, 5] ms; p=0.52). Both methods showed the same dyssynchrony trends after the pacemaker implantation, i.e. while both IVMD and interventricular e-DYS increased in the RVP group (IVMD 28 [23, 33] ms vs. interventricular e-DYS 26 [19, 33] ms, p=0.99), they remained low in the CSP group (IVMD -7 [-16, 2] ms vs. interventricular e-DYS -5 [-12, 2] ms, p=0.91). There was a moderate overall correlation between IVMD and interventricular e-DYS for all studied ventricular rhythms (R=0.74).

Conclusion: UHF-ECG noninvasively expresses interventricular dyssynchrony from V7-V1 chest leads with similar results to echocardiography. RVP increases interventricular dyssynchrony, while CSP preserves synchronous ventricular activation.

The hyperpolarization-activated cyclic nucleotide-gated channel 4 (HCN4) drives the funny current (I_f) in cardiac pacemaker regions. Its involvement in sinoatrial node pacemaker generation is well-known, but its function in the atrioventricular (AV) node (AVN) has not intensively been studied. HCN4 is expressed in the AVN and its expression within the AVN seems similar across mammalian species with HCN4 presence in the inferior nodal extensions, compact node, and atrioventricular bundle. The main direct regulators of HCN4 are cAMP and PKA. In addition, indirect regulators may affect HCN4 via trafficking and localization. However, these effects are underexplored in the AVN. AVN-specific effects in knock-out and knock-in mouse include reduced I_f density and increased AV block. HCN4 expression in the AVN could be affected by aging, exercise, heart failure, and diabetes. This could underlie changes in PR-interval, Atria-His interval, Wenckebach Cycle length, and AVN effective refractory period. Clinical reports link the HCN4 variant G1097W to AV block. Other clinical data comes from studies assessing ivabradine, an HCN4 inhibitor. In animals, ivabradine resulted in prolonged PR- and atrial-his intervals. To date, uncertainty regarding the role of HCN4 in the AVN remains. However, AVN-focused studies suggest HCN4's importance for AVN function. This review summarizes recent findings and highlights the involvement of HCN4 in normal and pathological AVN function.

Substrate mapping is an important component of electrophysiology (EP) study for the treatment of reentrant ventricular tachycardia (VT). It is utilized to detect characteristics of the electrical circuit, and in particular the location and properties of the central common pathway, aka the isthmus, where multiple circuit loops can coincide. Typically, reentrant circuits are single- or double-loop, but as the common pathway size increases, four-loop patterns may emerge, consisting of two parallel isthmuses or a single isthmus with four loops. Arrhythmogenic substrate contains a mixture of scar, calcification, and fibrofatty regions blended with viable ventricular myocytes, which can slow conduction. It is identified in the EP laboratory in part by the presence of low amplitude electrograms and a zone of uniform slow conduction (USC) resulting from a sparsity of remaining viable myocytes and molecular-level remodeling. The electrograms recorded near isthmus boundaries frequently exhibit an abnormal morphology, such as fractionation and late or split deflections, due to the separation of muscle fiber bundles by fibroadipose tissue or calcification, and due to other conduction impediments such as source-sink mismatch, wherein topographic changes to the viable myocardial structure occur. Substrate mapping facilitates the identification of arrhythmogenic regions during sinus rhythm, whereas inducible VT with periods of ongoing reentry, when recordable, can be utilized for further assessment. Substrate modeling augments substrate mapping by seeking to predict electrogram morphology and mapped features and properties to be encountered during EP study based on an accurate depiction of arrhythmogenic tissue. Herein, we elaborate on the details of VT substrate mapping and modeling to the present time.

Background: Predicting phrenic nerve (PN) location based on right pulmonary vein (RPV) anatomy using pre-ablation imaging may help avoid PN injury.

Objective: To determine the relationship between RPV anatomical variations and PN trajectory.

Methods: 103 consecutive patients with pre-ablation CT or MRI had RPV anatomy identified as: typical with separate RSPV and RIPV with distal branching versus right middle PV (RMPV) or early branching of RSPV. PN location was identified using high-output pacing (50mA x 2ms) over three contiguous RPV ostial and paraseptal antral zones: right superior PV (RSPV), RPV carina, and right inferior PV (RIPV). The relationship between anatomic variations and PN trajectory with need to adjust planned ablation lines to more distal antral position (> additional 10 mm from ostium) was determined.

Results: RSPV early branching occurred in 24%, and RMPV in 21% with anatomic variations more frequent in women (65% vs. 38%, p=0.01). PN capture extending to RIPV antrum was significantly more common in patients with RMPV (59.1%, PR=10.3; 95% CI: 2.5-43.2) or early branching of RSPV (64%, PR=10.9; 95% CI: 2.7-44) compared to typical anatomy (3.6%). Antral ablation line adjustments to avoid PN injury were required in 28% of patients, more frequently in those with RMPV (50%, PR=5.6; 95% CI: 2-15.7) or early branching (56%, PR=5.2; 95% CI: 1.3-15.3) compared to typical anatomy (7.1%).

Conclusions: RMPV or early branching of RSPV increases likelihood of PN capture in the RIPV proximal antrum by tenfold and requires a more distal antral ablation line to avoid phrenic nerve injury.

Background: The association of thyroid hormone sensitivity with heart rate remains unclear.

Objective: This study aims to elucidate the relationship between impaired thyroid hormone sensitivity and lower heart rate in the euthyroid population.

Methods: A total of 550 participants were included. Heart rate and serum biochemicals were measured. Thyroid hormone sensitivity indices were calculated by TSH index (TSHI), thyrotropin thyroxine resistance index (TT4RI), thyroid feedback quantile-based index (TFQI), Chinese-referenced parametric TFQI (PTFQI) and the ratio of FT3 to FT4 (FT3/FT4). Logistic regression analyses were applied to explore the relationship between indices of thyroid hormone sensitivity and heart rate.

Results: TSHI, TT4RI, TFQI, PTFQI were higher, and FT3/FT4 was lower in participants with heart rates ≤ 60bmp (all P < 0.001). Subjects with increased TSHI, TT4RI, TFQI, PTFQI and reduced FT3/FT4 had lower heart rates (≤60bmp) (all P for trend < 0.001). Odds ratios (ORs) (95% confidence intervals [CIs]) for TSHI, TT4RI, TFQI, PTFQI and FT3/FT4 in the highest quartile were respectively 2.090 (1.092-4.000), 2.240 (1.151-4.361), 2.014 (1.043-3.887), 2.163 (1.123-4.166) and 0.498, (0.249-0.996) compared with the lowest quartile after adjusted for gender, age, body mass index (BMI), smoking, drinking, hypertension, diabetes, coronary artery disease, glycated hemoglobin, total cholesterol, low-density lipoprotein, triglycerides.

Conclusion: Impaired sensitivity to thyroid hormones was associated with lower heart rate in euthyroid subjects. Future large-scale studies are needed to confirm our findings.

Background: Deceleration zones (DZ) represent important ablation targets in scar-related ventricular tachycardias (VT). Novel Electrocardiographic Imaging (ECGI) techniques could identify DZs instantly and non-invasively.

Objective: Evaluate a novel ECGI last deflection detection algorithm for non-invasive isochronal late activation substrate mapping (iLAM) in scar-related VT procedures against electroanatomical mapping (EAM) METHODS: Prospectively recruited scar-related VT ablation patients underwent contact and ECGI mapping. SR or RV-paced baseline maps were acquired, temporal signal averaging performed and unipolar electrograms (EGM) reconstructed. Local activation time was annotated to the last negative deflection (LD) before T-wave. iLAMs were generated by dividing activation maps in 8 and 12 isochronal zones. Number and location of ECGI late activation areas (LAA) and ECGI-DZ were compared to EAM on a segmental basis.

Results: 47 patients (27.7% ischemic, 72.3% non-ischemic) were studied, epicardial data was acquired in 30 (63.8%). No significant difference in the absolute LAAs were identified on ECGI versus EAM (p=0.161), latest EGM was significantly later on EAM. ECGI late activation mapping yielded a sensitivity of 68% and specificity of 95%. EAM identified DZs in 91.5%, ECGI in 93.6% of patients (p 0.5). ECGI detected significant more DZs per map than EAM (2.5±1.2 vs 1.2±0.8, p <0.001) but less steep activation gradients (p 0.002). Sensitivity for ECGI-DZ mapping was 46.8%, specificity 90.6% in the context of a high number of total segments, and pre-emptive exclusion of interpolated/artificial DZ (identified in 95.7%).

Conclusion: ECGI with LD detects late activation zones in the majority of cases with a moderate sensitivity. Yet, detailed functional substrate mapping including accurate localisation of local DZs remains challenging with low sensitivity precluding its clinical use for this indication in its current form.

Background: Anatomic characterization of unidirectional accessory pathways (APs) is inherently limited to the localization of the downstream insertion site. The inability to define the full anatomic course of unidirectional pathways can limit the safety and effectiveness of ablation in the setting of complex pathways, slanted pathways, unstable catheter positioning at downstream insertions, or insertions near the conduction system.

Objective: We aimed to develop novel pacing maneuvers to localize upstream insertions of unidirectional APs.

Methods: Two methods were evaluated: localizing the shortest transit time from roving pacing sites to a fixed reference in the opposite chamber (upstream transit mapping); and identifying the site at which the latest atrial or ventricular extrastimulus reset atrioventricular reciprocating tachycardia (late reset mapping). Unidirectional APs were included to test utility and feasibility of the techniques, and bidirectional APs were included to test anatomic accuracy.

Results: A total of 13 patients were included, 8 unidirectional APs and 5 bidirectional APs. Blind side mapping was successfully performed in all cases and showed excellent spatial correlation to conventional mapping methods (mean, 4.2 mm; SD, 1.3 mm) as well as to the site of successful ablation (mean, 2.5 mm; SD, 2.9 mm). The upstream transit mapping method was critical for successful ablation after conventional techniques proved inadequate in 2 cases.

Conclusion: Two novel methods, upstream transit mapping and late reset mapping, were used to localize the previously unmappable upstream insertions of unidirectional pathways. These methods expand the diagnostic toolbox to facilitate successful ablation in challenging cases.