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A 72-year-old man presented for routine dual chamber pacemaker interrogation 13 years following insertion for sick sinus syndrome. Increased noise, impedance and threshold of the right ventricular (RV) lead were identified. RV capture was maintained with an overall RV pacing burden of 47%. A routine generator replacement was scheduled alongside RV lead replacement. Fluoroscopy at the start of the procedure revealed an unexpected striking fracture of the RV pacing lead with complete separation of the proximal and distal portions within the RV. The patient was asymptomatic and described no predisposing factors. He underwent implantation of a new ventricular lead and generator and has remained well. This case demonstrates clear RV lead fracture as a late complication of pacemaker implantation despite maintained capture. This emphasises the need for a chest X-ray when a change in device parameters is noted at device interrogation even in the absence of symptoms., Competing Interests: Competing interests: None declared., (© BMJ Publishing Group Limited 2021. No commercial re-use. See rights and permissions. Published by BMJ.)

Purpose: Volume indices and left ventricular ejection fraction (LVEF) are routinely used to assess cardiac function. Ventricular strain values may provide additional diagnostic information, but their reproducibility is unclear. This study therefore compares the repeatability and reproducibility of volumes, volume fraction, and regional ventricular strains, derived from cardiovascular magnetic resonance (CMR) imaging, across three software packages and between readers., Methods: Seven readers analysed 16 short-axis CMR stacks of a porcine heart. Endocardial contours were manually drawn using OsiriX and Simpleware ScanIP and repeated in both softwares. The images were also contoured automatically in Circle CVI42. Endocardial global, apical, mid-ventricular, and basal circumferential strains, as well as end-diastolic and end-systolic volume and LVEF were compared., Results: Bland-Altman analysis found systematic biases in contour length between software packages. Compared to OsiriX, contour lengths were shorter in both ScanIP (-1.9 cm) and CVI42 (-0.6 cm), causing statistically significant differences in end-diastolic and end-systolic volumes, and apical circumferential strain (all p<0.006). No differences were found for mid-ventricular, basal or global strains, or left ventricular ejection fraction (all p<0.007). All CVI42 results lay within the ranges of the OsiriX results. Intra-software differences were found to be lower than inter-software differences., Conclusion: OsiriX and CVI42 gave consistent results for all strain and volume metrics, with no statistical differences found between OsiriX and ScanIP for mid-ventricular, global or basal strains, or left ventricular ejection fraction. However, volumes were influenced by the choice of contouring software, suggesting care should be taken when comparing volumes across different software., Competing Interests: The authors have declared that no competing interests exist.

Ventricular volumetric ejection fraction (VV EF) is often normal in patients with single ventricle circulations despite them experiencing symptoms related to circulatory failure. We sought to determine if kinetic energy (KE) could be a better marker of ventricular performance. KE was prospectively quantified using four-dimensional flow MRI in 41 patients with a single ventricle circulation (aged 0.5-28 yr) and compared with 43 healthy volunteers (aged 1.5-62 yr) and 14 patients with left ventricular (LV) dysfunction (aged 28-79 yr). Intraventricular end-diastolic blood was tracked through systole and divided into ejected and residual blood components. Two ejection fraction (EF) metrics were devised based on the KE of the ejected component over the total of both the ejected and residual components using 1) instantaneous peak KE to assess KE EF or 2) summating individual peak particle energy (PE) to assess PE EF. KE EF and PE EF had a smaller range than VV EF in healthy subjects (97.9 ± 0.8 vs. 97.3 ± 0.8 vs. 60.1 ± 5.2%). LV dysfunction caused a fall in KE EF ( P = 0.01) and PE EF ( P = 0.0001). VV EF in healthy LVs and single ventricle hearts was equivalent; however, KE EF and PE EF were lower ( P < 0.001) with a wider range indicating a spectrum of severity. Those reporting the greatest symptomatic impairment (New York Heart Association II) had lower PE EF than asymptomatic subjects ( P = 0.0067). KE metrics are markers of healthy cardiac function. PE EF may be useful in grading dysfunction. NEW & NOTEWORTHY Kinetic energy (KE) represents the useful work of the heart in ejecting blood. This article details the utilization of KE indexes to assess cardiac function in health and a variety of pathophysiological conditions. KE ejection fraction and particle energy ejection fraction (PE EF) showed a narrow range in health and a lower wider range in disease representing a spectrum of severity. PE EF was altered by functional status potentially offering the opportunity to grade dysfunction.

Patient-specific modelling has emerged as a tool for studying heart function, demonstrating the potential to provide non-invasive estimates of tissue passive stiffness. However, reliable use of model-derived stiffness requires sufficient model accuracy and unique estimation of model parameters. In this paper we present personalised models of cardiac mechanics, focusing on improving model accuracy, while ensuring unique parametrisation. The influence of principal model uncertainties on accuracy and parameter identifiability was systematically assessed in a group of patients with dilated cardiomyopathy ([Formula: see text]) and healthy volunteers ([Formula: see text]). For all cases, we examined three circumferentially symmetric fibre distributions and two epicardial boundary conditions. Our results demonstrated the ability of data-derived boundary conditions to improve model accuracy and highlighted the influence of the assumed fibre distribution on both model fidelity and stiffness estimates. The model personalisation pipeline-based strictly on non-invasive data-produced unique parameter estimates and satisfactory model errors for all cases, supporting the selected model assumptions. The thorough analysis performed enabled the comparison of passive parameters between volunteers and dilated cardiomyopathy patients, illustrating elevated stiffness in diseased hearts.

Background: The high risk of ventricular arrhythmias in patients with heart failure remains despite the benefit of cardiac resynchronization therapy (CRT). An electromechanical interaction between regional myocardial strain patterns and the electrophysiological substrate is thought to be important., Objective: We investigated the in vivo relation between left ventricular activation recovery interval (ARI), as a surrogate measure of action potential duration (APD), and local myocardial strain patterns in responders and nonresponders to CRT., Methods: ARIs were recorded from the left ventricular epicardium in 20 patients with CRT 6 weeks and 6 months post implantation. Two-dimensional speckle tracking echocardiography was performed at the same time to assess myocardial strains. Patients with ≥15% reduction in end-systolic volume at 6 months were classified as responders., Results: ARI decreased in responders (263 ± 46 ms vs 246 ± 47 ms, P < .01) and increased in nonresponders (235 ± 23 ms vs 261 ± 20 ms; P < .01). Time-to-peak radial, circumferential, and longitudinal strains increased in responders (41 ± 27, 35 ± 25, 56 ± 37 ms; P < .01) and decreased in nonresponders (-58 ± 26, -47 ± 26, -64 ± 27 ms; P < .01). There was a nonlinear correlation between changes in time-to-peak strain and ARIs (Spearman correlation coefficient r ≥ 0.70; P < .01). Baseline QRS duration >145 ms and QRS duration shortening with biventricular pacing were associated with ARI shortening following CRT., Conclusion: Changes in ventricular wall mechanics predict local APD lengthening or shortening during CRT. Nonresponders have a worsening of myocardial strain and local APD. Baseline QRS duration >145 ms and QRS duration shortening with biventricular pacing identified patients who exhibited improvement in APD., (Copyright © 2016 Heart Rhythm Society. Published by Elsevier Inc. All rights reserved.)

Background: A consistent feature of electrophysiological remodeling in heart failure is ventricular action potential duration (APD) prolongation. However, the effect of reverse remodeling on APD during cardiac resynchronization therapy (CRT) has not been determined in these patients. We hypothesized (1) that CRT may alter APD and (2) that the effect of CRT on APD may be different in patients who exhibit a good hemodynamic response to CRT compared with those with a poor response., Methods and Results: Left ventricular (LV) activation recovery intervals, as a surrogate for APD, were measured from the LV epicardium in 13 patients at day 0, 6 weeks, and 6 months after CRT implant. Responders to CRT were defined as those demonstrating a ≥15% reduction in LV end-systolic volume at 6 months. The responder group had a significant reduction in LV activation recovery interval (mean, -13±12 ms; median, -16 ms; interquartile range, -2 to -19 ms) during right ventricular pacing at 6 months (P<0.05). Conversely, the nonresponders showed a significant increase in activation recovery interval (mean, +22 ms±16; median, 17 ms; interquartile range, 8 to 35 ms; P<0.05). One patient in each group was on amiodarone., Conclusions: In patients with heart failure, LV epicardial APD (activation recovery interval) altered during CRT. The effect on APD was opposite in patients showing a good hemodynamic response compared with nonresponders. The findings may provide an explanation for the persistent high incidence of arrhythmias in some patients with CRT and the additional mortality benefit observed in responders of CRT.

Background: Quantification of myocardial blood flow (MBF) and myocardial perfusion reserve (MPR) by cardiovascular magnetic resonance (CMR) perfusion requires sampling of the arterial input function (AIF). While variation in the AIF sampling location is known to impact quantification by CMR and positron emission tomography (PET) perfusion, there is no evidence to support the use of a specific location based on their diagnostic accuracy in the detection of coronary artery disease (CAD). This study aimed to evaluate the accuracy of stress MBF and MPR for different AIF sampling locations for the detection of abnormal myocardial perfusion with expert visual assessment as the reference. Methods: Twenty-five patients with suspected or known CAD underwent vasodilator stress-rest perfusion with a dual-sequence technique at 3T. A low-resolution slice was acquired in 3-chamber view to allow AIF sampling at five different locations: left atrium (LA), basal left ventricle (bLV), mid left ventricle (mLV), apical left ventricle (aLV) and aortic root (AoR). MBF and MPR were estimated at the segmental level using Fermi function-constrained deconvolution. Segments were scored as having normal or abnormal perfusion by visual assessment and the diagnostic accuracy of stress MBF and MPR for each location was evaluated using receiver operating characteristic curve analysis. Results: In both normal (300 out of 400, 75 %) and abnormal segments, rest MBF, stress MBF and MPR were significantly different across AIF sampling locations (p < 0.001). Stress MBF for the AoR (normal: 2.42 (2.15–2.84) mL/g/min; abnormal: 1.71 (1.28–1.98) mL/g/min) had the highest diagnostic accuracy (sensitivity 80 %, specificity 85 %, area under the curve 0.90; p < 0.001 versus stress MBF for all other locations including bLV: normal: 2.78 (2.39–3.14) mL/g/min; abnormal: 2.22 (1.83–2.48) mL/g/min; sensitivity 91 %, specificity 63 %, area under the curve 0.81) and performed better than MPR for the LV locations (p < 0.01). MPR for the AoR (normal: 2.43 (1.95–3.14); abnormal: 1.58 (1.34–1.90)) was not superior to MPR for the bLV (normal: 2.59 (2.04–3.20); abnormal: 1.69 (1.36–2.14); p = 0.717). Conclusions: The AIF sampling location has a significant impact on MBF and MPR estimates by CMR perfusion, with AoR-based stress MBF comparing favorably to that for the current clinical reference bLV. [ABSTRACT FROM AUTHOR]

Device Optimization for Acute and Chronic CRT Background Cardiac anatomy and function adapt in response to chronic cardiac resynchronization therapy (CRT). The effects of these changes on the optimal left ventricle (LV) lead location and timing delay settings have yet to be fully explored. Objective To predict the effects of chronic CRT on the optimal LV lead location and device timing settings over time. Methods Biophysical computational cardiac models were generated for 3 patients, immediately post-implant (ACUTE) and after at least 6 months of CRT (CHRONIC). Optimal LV pacing area and device settings were predicted by pacing the ACUTE and CHRONIC models across the LV epicardium (49 sites each) with a range of 9 pacing settings and simulating the acute hemodynamic response (AHR) of the heart. Results There were statistically significant differences between the distribution of the AHR in the ACUTE and CHRONIC models (P < 0.0005 in all cases). The site delivering the maximal AHR shifted location between the ACUTE and CHRONIC models but provided a negligible improvement (<2%). The majority of the acute optimal LV pacing regions (76-100%) and device settings (76-91%) remained optimal chronically. Conclusion Optimization of the LV pacing location and device settings were important at the time of implant, with a reduced benefit over time, where the majority of the acute optimal LV pacing region and device settings remained optimal with chronic CRT. [ABSTRACT FROM AUTHOR]