Use of Cardiovascular Magnetic Resonance for Risk Stratification in Repaired Tetralogy of Fallot.

The risk of premature death in adult patients with repaired tetralogy of Fallot is real and not inconsiderable. From the third decade of life, the incidence of malignant ventricular arrhythmia (VA) is known to exponentially rise. Progressive adverse mechanoelectrical modelling because of years of volume and/or pressure overload from residual pulmonary valve dysfunction and ventricular scar creates the perfect catalyst for VA. Although potentially lifesaving, implantable cardiac defibrillators are associated with substantial psychological and physical morbidity. Better selection of patients most at risk of VA, so that implantable cardiac defibrillators are not inflicted on patients who will never need them, is therefore crucial and has inspired research on this topic for several decades. Cardiovascular magnetic resonance (CMR) enables noninvasive, radiation-free clinical assessment of anatomy and function, making it ideal for the lifelong surveillance of patients with congenital heart disease. Gold standard measurements of ventricular volumes and systolic function can be derived from CMR. Tissue characterization using CMR can identify a VA substrate and provides insight into myocardial disease. We detail risk factors for VA identified using currently available CMR techniques. We also discuss emerging and advanced CMR techniques that have not all yet translated into routine clinical practice. We review how CMR-defined predictors of VA in repaired tetralogy of Fallot can be incorporated into risk scores with other clinical factors to improve the accuracy of risk prediction and to allow for pragmatic clinical application. Finally, we discuss what the future may hold.

Le risque de décès prématuré chez les patients adultes présentant une tétralogie de Fallot réparée (TFr) est bien réel et doit être pris en considération. À partir de la trentaine, l'incidence de l'arythmie ventriculaire (AV) maligne augmente exponentiellement chez ces patients. Le remodelage mécanoélectrique défavorable causé sur de nombreuses années par une surcharge de volume ou de pression liée à la dysfonction de la valve pulmonaire et à la cicatrice ventriculaire constitue un catalyseur de l'AV. Les défibrillateurs implantables peuvent sauver la vie des patients, mais ils sont également associés à des taux de morbidité psychologique et physique importants. Il est donc crucial de mieux cerner les patients les plus susceptibles de présenter une AV pour éviter d'implanter un défibrillateur à ceux qui n'en auront jamais besoin. Plusieurs études ont d'ailleurs porté sur cette question au cours des dernières décennies. La résonance magnétique cardiovasculaire (RMC) permet une évaluation clinique non invasive et sans radiation de l'anatomie et la physiologie, ce qui en fait une technique idéale pour la surveillance à vie des patients atteints de cardiopathies congénitales. Des mesures de référence du volume ventriculaire et de la fonction systolique peuvent être obtenues par RMC. La caractérisation des tissus par RMC peut permettre de repérer le substrat de l'AV et de renseigner sur la maladie myocardique. Nous décrivons les facteurs de risque de l'AV pouvant être repérés par les techniques de RMC actuelles, et nous présentons des techniques de pointe et en émergence qui n'ont pas encore trouvé leur place dans la pratique clinique courante. Nous examinons la façon dont les facteurs de prédiction de l'AV définis par RMC chez les patients atteints de TFr peuvent être intégrés aux indices de risque et conjugués à d'autres facteurs cliniques pour améliorer l'exactitude des prédictions et connaître une application clinique pratique. Nous évoquons enfin les possibilités futures.

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.

Effect of Pregnancy on Ventricular and Aortic Dimensions in Repaired Tetralogy of Fallot.

BACKGROUND: The aim was to assess whether cardiovascular adaptation to pregnancy in women with repaired tetralogy of Fallot (TOF) adversely affects hemodynamic stability, in particular with respect to right ventricular (RV) dilatation, pulmonary regurgitation, or aortic root dilatation. METHODS AND RESULTS: This was a retrospective cohort study of women with repaired TOF with paired cardiovascular magnetic resonance scans before and after their first pregnancy (baseline RV end systolic volume index 49 mL/m2 and RV end diastolic volume index 118 mL/m2) matched with a comparison group of nulliparous women with TOF. Cases were matched for age at baseline cardiovascular magnetic resonance scan, time between follow-up of cardiovascular magnetic resonance scans, QRS duration, RV ejection fraction, and indexed RV end systolic and diastolic volume at baseline. Effect of pregnancy and time on parameters was assessed using mixed-effects modelling. Nineteen women with repaired TOF who had completed their first pregnancy were identified and matched with 38 nulliparous women. We observed no deleterious effects of pregnancy on RV volumes, aortic dimensions, or exercise data. There was an effect of pregnancy observed in both left ventricular end diastolic volume and left ventricular stroke volume, consistent with a sustained small increase in left ventricular stroke volume attributed to pregnancy (53-55 mL/m2). CONCLUSIONS: Women with repaired TOF and with mild-to-moderate RV dilatation considering pregnancy can be reassured that pregnancy is unlikely to cause deterioration in their cardiovascular status. We recommend that women are routinely assessed and followed up before and after pregnancy and that prepregnancy counseling is tailored to their individual clinical status.

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.

Carbon monoxide poisoning: an ancient and frequent cause of accidental death.

Carbon monoxide poisoning is both an ancient and current cause of inadvertent (accidental) death and more recently has emerged as a cause of suicide worldwide. This article describes the pathophysiology and epidemiology of this most toxic and frequently occult poison.