Predicting Survival in Repaired Tetralogy of Fallot: A Lesion-Specific and Personalized Approach.

OBJECTIVES: This study sought to identify patients with repaired tetralogy of Fallot (rTOF) at high risk of death and malignant ventricular arrhythmia (VA). BACKGROUND: To date there is no robust risk stratification scheme to predict outcomes in adults with rTOF. METHODS: Consecutive patients were prospectively recruited for late gadolinium enhancement (LGE) cardiovascular magnetic resonance (CMR) to define right and left ventricular (RV, LV) fibrosis in addition to proven risk markers. RESULTS: The primary endpoint was all-cause mortality. Of the 550 patients (median age 32 years, 56% male), 27 died (mean follow-up 6.4 ± 5.8; total 3,512 years). Mortality was independently predicted by RVLGE extent, presence of LVLGE, RV ejection fraction ≤47%, LV ejection fraction ≤55%, B-type natriuretic peptide ≥127 ng/L, peak exercise oxygen uptake (V02) ≤17 mL/kg/min, prior sustained atrial arrhythmia, and age ≥50 years. The weighted scores for each of the preceding independent predictors differentiated a high-risk subgroup of patients with a 4.4%, annual risk of mortality (area under the curve [AUC]: 0.87; P < 0.001). The secondary endpoint (VA), a composite of life-threatening sustained ventricular tachycardia/resuscitated ventricular fibrillation/sudden cardiac death occurred in 29. Weighted scores that included several predictors of mortality and RV outflow tract akinetic length ≥55 mm and RV systolic pressure ≥47 mm Hg identified high-risk patients with a 3.7% annual risk of VA (AUC: 0.79; P < 0.001) RVLGE was heavily weighted in both risk scores caused by its strong relative prognostic value. CONCLUSIONS: We present a score integrating multiple appropriately weighted risk factors to identify the subgroup of patients with rTOF who are at high annual risk of death who may benefit from targeted therapy.

Myocardial Architecture, Mechanics, and Fibrosis in Congenital Heart Disease.

Congenital heart disease (CHD) is the most common category of birth defect, affecting 1% of the population and requiring cardiovascular surgery in the first months of life in many patients. Due to advances in congenital cardiovascular surgery and patient management, most children with CHD now survive into adulthood. However, residual and postoperative defects are common resulting in abnormal hemodynamics, which may interact further with scar formation related to surgical procedures. Cardiovascular magnetic resonance (CMR) has become an important diagnostic imaging modality in the long-term management of CHD patients. It is the gold standard technique to assess ventricular volumes and systolic function. Besides this, advanced CMR techniques allow the acquisition of more detailed information about myocardial architecture, ventricular mechanics, and fibrosis. The left ventricle (LV) and right ventricle have unique myocardial architecture that underpins their mechanics; however, this becomes disorganized under conditions of volume and pressure overload. CMR diffusion tensor imaging is able to interrogate non-invasively the principal alignments of microstructures in the left ventricular wall. Myocardial tissue tagging (displacement encoding using stimulated echoes) and feature tracking are CMR techniques that can be used to examine the deformation and strain of the myocardium in CHD, whereas 3D feature tracking can assess the twisting motion of the LV chamber. Late gadolinium enhancement imaging and more recently T1 mapping can help in detecting fibrotic myocardial changes and evolve our understanding of the pathophysiology of CHD patients. This review not only gives an overview about available or emerging CMR techniques for assessing myocardial mechanics and fibrosis but it also describes their clinical value and how they can be used to detect abnormalities in myocardial architecture and mechanics in CHD patients.

Inter-study reproducibility of interleaved spiral phase velocity mapping of renal artery haemodynamics.

BACKGROUND: Qualitative and quantitative assessment of renal blood flow is valuable in the evaluation of patients with renal and renovascular diseases as well as in patients with heart failure. The temporal pattern of renal flow velocity through the cardiac cycle provides important information about renal haemodynamics. High temporal resolution interleaved spiral phase velocity mapping could potentially be used to study temporal patterns of flow and measure resistive and pulsatility indices which are measures of downstream resistance. METHODS: A retrospectively gated breath-hold spiral phase velocity mapping sequence (TR 19 ms) was developed at 3 Tesla. Phase velocity maps were acquired in the proximal right and left arteries of 10 healthy subjects in each of two separate scanning sessions. Each acquisition was analysed by two independent observers who calculated the resistive index (RI), the pulsatility index (PI), the mean flow velocity and the renal artery blood flow (RABF). Inter-study and inter-observer reproducibility of each variable was determined as the mean +/- standard deviation of the differences between paired values. The effect of background phase errors on each parameter was investigated. RESULTS: RI, PI, mean velocity and RABF per kidney were 0.71+/- 0.06, 1.47 +/- 0.29, 253.5 +/- 65.2 mm/s and 413 +/- 122 ml/min respectively. The inter-study reproducibilities were: RI -0.00 +/- 0.04 , PI -0.03 +/- 0.17, mean velocity -6.7 +/- 31.1 mm/s and RABF per kidney 17.9 +/- 44.8 ml/min. The effect of background phase errors was negligible (<2% for each parameter). CONCLUSIONS: High temporal resolution breath-hold spiral phase velocity mapping allows reproducible assessment of renal pulsatility indices and RABF.

Remote-controlled magnetic navigation and ablation with 3D image integration as an alternative approach in patients with intra-atrial baffle anatomy.

BACKGROUND: Improvement in outcome of infants born with congenital heart defects has been accompanied by an increasing frequency of late arrhythmias. Ablation is difficult because of multiple tachycardias in the presence of complex anatomy with limited accessibility. We report on remote-controlled ablation using magnetic navigation in conjunction with 3D image integration in patients with previous intra-atrial baffle procedures. METHODS AND RESULTS: Thirteen patients (8 male; age, 30.5±8 years) with supraventricular tachycardia (SVT) underwent catheter ablation. Group A had a medical history of a Mustard or Senning operation, whereas group B had undergone total cavopulmonary connection. A total of 26 tachycardias were treated in 17 procedures (median cycle length of 280 ms). Group A patients had more inducible SVTs than group B, and all index SVTs were located in the remainder of the morphological right atrium in all but 1 patient. Retrograde access through the aorta was performed and led to successful ablation, using magnetic navigation with a very low total radiation exposure (median of 3.8 minutes in group A versus 5.9 minutes in group B). Only 1 of 13 patients continued to have short-lasting SVTs despite 3 ablation procedures during a median follow-up time of >200 days. CONCLUSIONS: Remote-controlled catheter ablation by magnetic navigation in combination with accurate 3D image integration allowed safe and successful elimination of SVTs, using an exclusively retrograde approach, resulting in low radiation exposure for patients after intra-atrial baffle procedures (Mustard, Senning, or total cavopulmonary connection).

A whole body statistical shape model for radio frequency simulation.

The development of ultra low power wireless sensors for customized wearable and implantable medical devices requires patient specific models for radio frequency simulation to understand wave propagation in the body. In practice, the creation of a patient specific whole-body model is difficult and time consuming to create. It is therefore necessary to establish a method for studying a population in a statistical manner. In this paper, we present a statistical shape model for the whole body for RF simulation. It is built from 10 male and 10 female subjects of varying size and height. This model has the ability to instantiate a new surface mesh with the parameters allowed by the training set. This model would provide shapes of varying sizes for studies, without the requirement of obtaining subject specific whole body models. Results from finite-differences time-domain simulation are presented on the extreme shapes from the model and demonstrate the need for a full understanding of the range in body shapes.

Black-blood T2* technique for myocardial iron measurement in thalassemia.

PURPOSE: To compare the effectiveness and reproducibility of a new black-blood sequence vs. a conventional bright-blood gradient-echo T2* sequence for myocardial iron overload measurement in thalassemia. MATERIALS AND METHODS: Twenty thalassemia patients were studied. Black-blood sequence images were acquired in diastole after a double inversion recovery (DIR) preparation pulse. Bright-blood sequence images were acquired in both early systole and late diastole. The data were randomized and the T2* analysis was performed blindly by two independent observers. RESULTS: The T2* values from the black-blood sequence were comparable to those of the conventional bright-blood sequence (25.7 +/- 12.9 msec vs. 26.4 +/- 14.2 msec in early systole, P = 0.44; and 25.2 +/- 13.1 msec in late diastole, P = 0.41). The coefficient of variation (CV) for black-blood image T2* analysis was 4.1% compared with 8.9% (early systole P = 0.03) and 7.8% (late diastole P = 0.05) for bright-blood image analysis. CONCLUSION: The black-blood T2* technique yields high-contrast myocardial images, provides clearly depicted myocardial borders, and avoids blood signal contamination of the myocardium while yielding improvements in interobserver variability.