An in-silico analysis of the effect of heart position and orientation on the ECG morphology and vectorcardiogram parameters in patients with heart failure and intraventricular conduction defects.

AIM: The aim of this study was to investigate the influence of geometrical factors on the ECG morphology and vectorcardiogram (VCG) parameters. METHODS: Patient-tailored models based on five heart-failure patients with intraventricular conduction defects (IVCDs) were created. The heart was shifted up to 6 cm to the left, right, up, and down and rotated ±30° around the anteroposterior axis. Precordial electrodes were shifted 3 cm down. RESULTS: Geometry modifications strongly altered ECG notching/slurring and intrinsicoid deflection time. Maximum VCG parameter changes were small for QRS duration (-6% to +10%) and QRS-T angle (-6% to +3%), but considerable for QRS amplitude (-36% to +59%), QRS area (-37% to +42%), T-wave amplitude (-41% to +36%), and T-wave area (-42% to +33%). CONCLUSION: The position of the heart with respect to the electrodes is an important factor determining notching/slurring and voltage-dependent parameters and therefore must be considered for accurate diagnosis of IVCDs.

Patient-specific modelling of cardiac electrophysiology in heart-failure patients.

AIMS: Left-ventricular (LV) conduction disturbances are common in heart-failure patients and a left bundle-branch block (LBBB) electrocardiogram (ECG) type is often seen. The precise cause of this pattern is uncertain and is probably variable between patients, ranging from proximal interruption of the left bundle branch to diffuse distal conduction disease in the working myocardium. Using realistic numerical simulation methods and patient-tailored model anatomies, we investigated different hypotheses to explain the observed activation order on the LV endocardium, electrogram morphologies, and ECG features in two patients with heart failure and LBBB ECG. METHODS AND RESULTS: Ventricular electrical activity was simulated using reaction-diffusion models with patient-specific anatomies. From the simulated action potentials, ECGs and cardiac electrograms were computed by solving the bidomain equation. Model parameters such as earliest activation sites, tissue conductivity, and densities of ionic currents were tuned to reproduce the measured signals. Electrocardiogram morphology and activation order could be matched simultaneously. Local electrograms matched well at some sites, but overall the measured waveforms had deeper S-waves than the simulated waveforms. CONCLUSION: Tuning a reaction-diffusion model of the human heart to reproduce measured ECGs and electrograms is feasible and may provide insights in individual disease characteristics that cannot be obtained by other means.

Speckle-Tracking Layer-Specific Analysis of Myocardial Deformation and Evaluation of Scar Transmurality in Chronic Ischemic Heart Disease.

BACKGROUND: Identification of the extent of scar transmurality in chronic ischemic heart disease is important because it correlates with viability. The aim of this retrospective study was to evaluate whether layer-specific two-dimensional speckle-tracking echocardiography allows distinction of scar presence and transmurality. METHODS: A total of 70 subjects, 49 with chronic ischemic cardiomyopathy and 21 healthy subjects, underwent two-dimensional speckle-tracking echocardiography and late gadolinium-enhanced cardiac magnetic resonance. Scar extent was determined as the relative amount of hyperenhancement using late gadolinium-enhanced cardiac magnetic resonance in an 18-segment model (0% hyperenhancement = normal; 1%-50% = subendocardial scar; 51%-100% = transmural scar). In the same 18-segment model, peak systolic circumferential strain and longitudinal strain were calculated separately for the endocardial and epicardial layers as well as the full-wall myocardial thickness. RESULTS: All strain parameters showed cutoff values (area under the curve > 0.69) that allowed the discrimination of normal versus scar segments but not of transmural versus subendocardial scars. This was true for all strain parameters analyzed, without differences in efficacy between longitudinal and circumferential strain and subendocardial, subepicardial, and full-wall-thickness strain values. Circumferential and longitudinal strain in normal segments showed transmural and basoapical gradients (greatest values at the subendocardial layer and apex). In segments with scar, transmural gradient was maintained, whereas basoapical gradient was lost because the reduction of strain values in the presence of the scar was greater at the apex. CONCLUSIONS: The two-dimensional speckle-tracking echocardiographic values distinguish scar presence but not transmurality; thus, they are not useful predictors of scar segment viability. It remains unclear why there is a greater strain value reduction in the presence of a scar at the apical level.

Predictors of disagreement between prospectively ECG-triggered dual-source coronary computed tomography angiography and conventional coronary angiography.

AIMS: To identify causes of misinterpretation in second generation, dual-source coronary computed tomography angiography (CCTA). METHODS: A retrospective re-interpretation was performed on 100 consecutive CCTA studies, previously performed with a 2×128 slice dual-source CT. Results were compared with coronary angiography (CA). CCTA and CA images were interpreted by 2 independent readers. At CCTA vessel diameter, image quality, plaque characteristics and localization (bifurcation vs. non) were described for all segments. Finally, aortic contrast-to-noise ratio (CNR) and the total Agatston calcium score were quantified. Agreement between CCTA and CA was assessed with the Kappa statistic after categorizing the stenosis severity at significant (≥50%) and critical (≥70%) cut-offs, and independent predictors of disagreement were determined by multivariable logistic regression, including patient characteristics such as body mass index (BMI), heart rate (HR), age and gender. RESULTS: Per-segment sensitivity and specificity at ≥50% and ≥70% stenosis was of 83-95%, and 73-97%, respectively. There was a substantial agreement between CCTA and CA (kappa-50%=0.78, SE=0.03; kappa-70%=0.72, SE=0.03). Worse motion-related quality score, smaller vessel diameter, calcification within the segment of interest and LAD location were independent predictors of disagreement at 50% stenosis. The same factors, excluded LAD location, in addition to bifurcation-location of the coronary lesion predicted misdiagnosis at 70% stenosis. HR per se and BMI did not predict disagreement. CONCLUSION: According to the literature a substantial agreement between CCTA and CA was found. However, discrepancies exist and are mainly related with motion-related degradation of image quality, specific vessel anatomy and plaque characteristics. Awareness of such potential limitations may help guiding interpretation of CCTA.

[The emerging role of three-dimensional transesophageal echocardiography in guiding the MitraClip procedure]. / L'emergente ruolo dell'ecocardiografia transesofagea tridimensionale come guida durante la procedura di MitraClip.

Percutaneous edge-to-edge mitral valve repair with the MitraClip device has been shown to be a safe and effective procedure in selected patients with moderate-to-severe mitral regurgitation. Two-dimensional transesophageal echocardiography (2D TEE) is the primary imaging modality for guidance of the procedure. Real-time three-dimensional (3D) TEE has recently been used as additional imaging modality during the MitraClip procedure. In comparison with 2D TEE, 3D TEE provides additional information in several steps of the procedure, including precise positioning of the clip delivery system into the left atrium, correct alignment of the clip arms perpendicular to the coaptation line and confirmation of the correct grasping location. This review describes the relevant role of 3D TEE imaging during the procedure, but also its limitations.

Three-dimensional transesophageal echocardiography in degenerative mitral regurgitation.

The morphology of mitral valve (MV) prolapse and flail may be extremely variable, with dominant and secondary dynamic lesions. Any pathologic valve appears unique and different from any other. Three-dimensional (3D) transesophageal echocardiography is a powerful tool to evaluate the geometry, dynamics, and function of the MV apparatus and may be of enormous value in helping surgeons perform valve repair procedures. Indeed, in contrast to the surgical view, 3D transesophageal echocardiography can visualize MV prolapse and flail in motion and from different perspectives. The purpose of this special article is not to provide a comprehensive review of degenerative MV disease but rather to illustrate different types of mitral prolapse and flail as they appear from multiple 3D transesophageal echocardiographic perspectives using a series of clinical scenarios. Because in everyday practice, 3D transesophageal echocardiographic images of MV prolapse and flail are usually observed in motion, each scenario is accompanied by several videos. Finally, the authors provide for each scenario a brief description of the surgical techniques that are usually performed at their institution.

In vivo electromechanical assessment of heart failure patients with prolonged QRS duration.

BACKGROUND: Combined measurement of electrical activation and mechanical dyssynchrony in heart failure (HF) patients is scarce but may contain important mechanistic and diagnostic clues. OBJECTIVE: The purpose of this study was to characterize the electromechanical (EM) coupling in HF patients with prolonged QRS duration. METHODS: Ten patients with QRS width >120 ms underwent left ventricular (LV) electroanatomic contact mapping using the Noga® XP system (Biosense Webster). Recorded voltages during the cardiac cycle were converted to maps of depolarization time (TD). Electrode positions were tracked and converted into maps of time-to-peak shortening (TPS) using custom-made deformation analysis software. Correlation analysis was performed between the 2 maps to quantify EM coupling. Simulations with the CircAdapt cardiovascular system model were performed to mechanistically unravel the observed relation between TD and TPS. RESULTS: The delay between earliest LV electrical activation and peak shortening differed considerably between patients (TPSmin-TDmin = 360 ± 73 ms). On average, total mechanical dyssynchrony exceeded total electrical activation (ΔTPS = 177 ± 47 ms vs ΔTD = 93 ± 24 ms, P <.001), but a large interpatient variability was observed. The TD and TPS maps correlated strongly in all patients (median R = 0.87, P <.001). These correlations were similar for regions with unipolar voltages above and below 6mV (Mann-Whitney U test, P = .93). Computer simulations revealed that increased passive myocardial stiffness decreases ΔTPS relative to ΔTD and that lower contractility predominantly increases TPSmin-TDmin. CONCLUSION: EM coupling in HF patients is maintained, but the relationship between TD and TPS differs strongly between patients. Intra-individual and inter-individual differences may be explained by local and global differences in passive and contractile myocardial properties.

3D TEE during catheter-based interventions.

Guidance of catheter-based procedures is performed using fluoroscopy and 2-dimensional transesophageal echocardiography (TEE). Both of these imaging modalities have significant limitations. Because of its 3-dimensional (3D) nature, 3D TEE allows visualizing the entire scenario in which catheter-based procedures take place (including long segments of catheters, tips, and the devices) in a single 3D view. Despite these undeniable advantages, 3D TEE has not yet gained wide acceptance among most interventional cardiologists and echocardiographists. One reason for this reluctance is probably the absence of standardized approaches for obtaining 3D perspectives that provide the most comprehensive information for any single step of any specific procedure. Therefore, the purpose of this review is to describe what we believe to be the most useful 3D perspectives in the following catheter-based percutaneous interventions: transseptal puncture; patent foramen ovale/atrial septal defect closure; left atrial appendage occlusion; mitral valve repair; and closure of paravalvular leaks.

Imaging-based right-atrial anatomy by computed tomography, magnetic resonance imaging, and three-dimensional transoesophageal echocardiography: correlations with anatomic specimens.

Nowadays computed tomography, cardiac magnetic resonance imaging, and tridimensional transoesophageal echocardiography provide anatomic images of right-atrial structures with an impressive richness of anatomical details. It is therefore surprising that these techniques are not routinely used as complementary tools in teaching anatomy. This review aims to fill this gap showing the normal anatomy of right atrium as displayed by these sophisticated imaging techniques. A better understanding of right-atrial anatomy is crucial for the treatment of primary right-atrium electrical disorders as well as for catheter-based interventions for structural heart disease. The success of these procedures is, in fact, related to an accurate anatomical pre-procedural assessment. In this review, we describe the normal anatomy and variants of those right-atrial structures relevant for both ablationists and interventionalists.