Introduction: Reliable automatic pacing threshold determination functions offer a reduced follow-up examination time and safe remote monitoring. Further, the success rate and accuracy of the automatic pacing threshold determination function have not been sufficiently clarified. Methods: We evaluated 456 patients (male/female: 269/187, age: 70.4±13.3 years, pacemakers/defibrillators: 341/115) with cardiac implantable devices that had an automatic pacing threshold measurement function (the atrium and ventricle/ ventricle only: 298/158). We measured their pacing thresholds with both the automatic and manual methods at periodic device examination visits. Patients who had a high threshold (>4.0V/0.4ms) or out-of-range lead impedance (>2000 or <200Ω) were excluded from the analysis. Results: An automatic pacing threshold was obtained successfully in 206/274 (75.2%) patients in the atrium and in 392/443 (88.5%) in the ventricle. The automatic pacing threshold differed from the manual threshold by more than 1.0mV at the same pulse width in 12 (4.0%) patients in the atrium and in 5 (1.1%) in the ventricle. The success rate of the automatic pacing threshold determination differed depending on which generator manufacturer was used. The success rate for each manufacturer (Medtronic, St. Jude Medical, Biotronik and Sorin) was 167/173 (96.5%), 9/64 (14.1%), 30/37 (81.1%), and 0/0 in the atrium, and 223/224 (99.6%), 79/102 (77.5%), 68/85 (80.0%), and 22/32 (68.8%) in the ventricle, respectively. Regarding the success rate, Medtronic devices were superior to the others in both the atrium and ventricle (P<0.001-P=0.039). St. Jude Medical devices were inferior to the others in the atrium (p<0.001). There were no other significant factors affecting the success rate. The correlation between the pacing threshold measured by the automatic method and that by the manual method was significant in the atrium (r=0.558, P<0.001) and ventricle (r=0.779, P<0.001). Conclusions: The success rate of the automatic pacing threshold determination depended on which generator manufacturer was used. The measurable threshold values using the automatic method were acceptably correlated with those measured by the manual method.
AimsFor successful ablation of ventricular outflow tract arrhythmia, estimation of its origin prior to the procedure can be useful. Morphology and lead placement in the right thoracic area may be useful for this purpose. Electrocardiography using synthesized right-sided chest leads (Syn-V3R, Syn-V4R, and Syn-V5R) is performed using standard leads without any additional leads. This study evaluated the usefulness of synthesized right-sided chest leads in estimating the origin of ventricular outflow tract arrhythmia.
Objective Although magnetic resonance imaging (MRI) is the gold standard for evaluating abnormal myocardial fibrosis and extracellular volume (ECV) of the left ventricular myocardium (LVM), a similar evaluation has recently become possible using computed tomography (CT). In this study, we investigated the diagnostic accuracy of a new 256-row multidetector CT with a low tube-voltage single energy scan and deep-learning-image reconstruction (DLIR) in detecting abnormal late enhancement (LE) in LVM. Methods We evaluated the diagnostic performance of CT for detecting LE in LVM and compared the results with those of MRI as a reference. We also measured the ECV of the LVM on CT and compared the results with those on MRI. Materials We analyzed 50 consecutive patients who underwent cardiac CT, including a late-phase scan and MRI, within three months of suspected cardiomyopathy. All patients underwent 256-slice CT (Revolution APEX; GE Healthcare, Waukesha, USA) with a low tube-voltage (70 kV) single energy scan and DLIR for a late-phase scan. Results In patient- and segment-based analyses, the sensitivity, specificity, and accuracy of detection of LE on CT were 94% and 85%, 100% and 95%, and 96% and 93%, respectively. The ECV of LVM per patient on CT and MRI was 33.0±6.2% and 35.9±6.1%, respectively. These findings were extremely strongly correlated, with a correlation coefficient of 0.87 (p<0.0001). The effective radiation dose on late-phase scanning was 2.4±0.9 mSv. Conclusion The diagnostic performance of 256-row multislice CT with a low tube voltage and DLIR for detecting LE and measuring ECV in LVM is credible.
Abstract Introduction Extra-cellular volume (ECV) fraction on magnetic resonance imaging (MRI) can evaluate the degree of myocardial fibrosis and has been reported to help diagnose and evaluate the prognosis of cardiomyopathy. In hypertrophic cardiomyopathy (HCM), ECV analysis on MRI is reported to help predict ventricular arrhythmias. However, the performance of cardiac MRI takes time, and there are also several contraindications. Cardiac computed tomography (CT) is more versatile than cardiac MRI and is also useful in screening coronary artery disease. ECV analysis on CT is now available, and a good correlation with ECV on MRI has been reported. We hypothesized that ECV on CT, a new fibrosis indicator, would be useful in predicting prognosis in HCM patients. Purpose To determine the utility of ECV analysis on CT to predict the prognosis in patients with HCM. Methods One hundred and three HCM patients (68 males, 66 ± 11 years old) who underwent cardiac CT using 320-row detector CT or 256-row detector CT, from 2008 to 2021 at our two hospitals were analyzed. We measured left ventricular (LV) ECV (LV-ECV) on CT and collected patient characteristics, transthoracic echocardiographic, and other CT findings. We investigated the relationship between these findings and the major adverse cardiac events (MACEs) (cardiac death, fatal arrhythmia, and heart failure hospitalization) after CT. Results All patients were followed for 64 ± 54 months after cardiac CT, and 15 patients (14.6%) had MACEs (ten heart failure hospitalization cases, two ventricular fibrillation cases, two sustained ventricular tachycardia cases, and one sudden cardiac death case). The patients with MACEs had a significantly higher LV-ECV, sudden cardiac death (SCD) risk score and lower LV ejection fraction (LVEF) than those without MACEs（42.0 ± 8.3% vs. 33.7 ± 6.1%, P < 0.001, 2.4 ± 0.39 vs 1.95 ± 0.16, P= 0.047, and 57.7 ± 11.9% vs. 66.7 ± 6.9%, P = 0.004). The percentage of dilated phase HCM was significantly higher in the patients with MACEs than those without MACEs (21% vs 0%, p=0.002). LV-ECV was the only significant predictor of MACEs based on the multivariate analysis by Cox proportional hazard model (hazard ratio 1.23, 95% confidence interval 1.09-1.41, P<0.001). The optimal threshold of LV-ECV to predict MACEs was 37.6% based on the receiver operating characteristic analysis. The sensitivity and specificity of LV-ECV to predict MACEs were 73% and 78% at the best cut-off, and the area under the curve was 0.79 (Figure A). The patients with LV-ECV ≥ 37.6% (30 patients) had significantly higher MACEs than those with LV-ECV < 37.6% during the follow-up periods (P < 0.001) (Figure B). Conclusion LV-ECV on CT of 37.6% is a good prognostic indicator in HCM cases. ECV analysis on CT helped predict MACEs in HCM cases.
Abstract Introduction Cardiac amyloidosis (CA) results in a restrictive cardiomyopathy caused by extracellular deposition of proteins in the myocardium, demanding early identification for effective management. Left ventricular (LV) strain, mainly evaluated by echocardiography or cardiac magnetic resonance, provides sensitive and specific indicators for detecting CA, particularly apical sparing. It represents a pattern where the longitudinal strain (LS) in the basal and middle segments of LV is more impaired compared to the apical segments.¹ Cardiac computed tomography (CT) is useful not only for coronary artery evaluation but also for myocardial assessment, including LV ejection fraction (LVEF). Advanced software made it possible to analyse LS on cardiac CT (Figures A,B). Hypothesis: LS analysis using four-dimensional cardiac CT is helpful for the differential diagnosis of LV hypertrophied myocardial diseases and for detecting CA. Methods We analyzed 60 patients with LV hypertrophied myocardial diseases who underwent cardiac CT using 256-detector row or 320-detector row CT since 2009. Twenty patients of them were diagnosed with CA ( 70 ± 10 years, 14 males), the other 20 patients were diagnosed with hypertrophic cardiomyopathy (HCM) ( 60 ± 14 years, 12 males), and the rest of the 20 patients were diagnosed with severe aortic valve stenosis (AS) ( 86 ± 6 years, nine males). We analyzed LV global LS (GLS) and segmental LS using specific software and four-dimensional CT data. We evaluated relative apical LS as the value dividing the average LS of apical segments by the sum of the average LS of basal segments and mid-ventricular segments (Figure C). If the value was ≥ 1, apical sparing was defined as present. We compared the LS data and the percentage of apical sparing among those three myocardial diseases. Results There was no significant difference in LVEF among the three groups (52 ± 14%, 55 ± 27%, and 50 ± 18%, respectively; P = 0.15). There was no significant difference in GLS among the three groups (-10.6 ± 3.6%, -10.2 ± 5.2%, and -11.6 ± 3.8%, respectively; P = 0.87). Apical sparing was observed in 13 cases (65%) of CA, which was significantly higher than 3 cases (15%) of HCM or 4 cases(20%) of AS (P = 0.0002). Conclusions LV strain analysis using cardiac CT is helpful for detecting apical sparing. Advanced image analysis software has enabled LV strain analysis by cardiac CT, which is useful for the differential diagnosis of CA among LV hypertrophied diseases.Figure A,B,C
