Bejal Pandya

Prognostic Significance of Cardiac Magnetic Resonance Imaging in Children with Pulmonary Hypertension

Background— There are very few validated prognostic markers in pediatric pulmonary hypertension. Cardiac MRI is a useful, noninvasive method for determining prognosis in adults. The present study is the first to assess its prognostic value in children. Methods and Results— A total of 100 children with pulmonary hypertension (median, 10.4 years; range, 0.5–17.6 years) were evaluated (idiopathic, n=60; repaired congenital heart disease, n=22; miscellaneous, n=18). In all patients, ventricular volumes and great vessel flow were measured. Volumetric data were obtained using retrospectively gated cine imaging (n=37) or real-time imaging (n=63), depending on the patient’s ability to hold his or her breath. During a median follow-up of 1.9 years, 11 patients died and 3 received lung transplantation. Of the cardiac MR parameters measured, right ventricular ejection fraction and left ventricular stroke volume index were most strongly predictive of survival on univariate analysis (2.6- and 2.5-fold increase in mortality for every 1-SD decrease, respectively; P<0.05). These results were reflected in good separation of tertile-based Kaplan-Meier survival curves for these variables. Conclusions— Cardiac MR measures correlate with clinical status and prognosis in children with pulmonary hypertension. Cardiac MR is feasible and may be useful in clinical decision making in pediatric pulmonary hypertension.

Abnormal Wave Reflections and Left Ventricular Hypertrophy Late After Coarctation of the Aorta Repair

Patients with repaired coarctation of the aorta are thought to have increased afterload due to abnormalities in vessel structure and function. We have developed a novel cardiovascular magnetic resonance protocol that allows assessment of central hemodynamics, including central aortic systolic blood pressure, resistance, total arterial compliance, pulse wave velocity, and wave reflections. The main study aims were to (1) characterize group differences in central aortic systolic blood pressure and peripheral systolic blood pressure, (2) comprehensively evaluate afterload (including wave reflections) in the 2 groups, and (3) identify possible biomarkers among covariates associated with elevated left ventricular mass (LVM). Fifty adult patients with repaired coarctation and 25 age- and sex-matched controls were recruited. Ascending aorta area and flow waveforms were obtained using a high temporal-resolution spiral phase-contrast cardiovascular magnetic resonance flow sequence. These data were used to derive central hemodynamics and to perform wave intensity analysis noninvasively. Covariates associated with LVM were assessed using multivariable linear regression analysis. There were no significant group differences (P≥0.1) in brachial systolic, mean, or diastolic BP. However central aortic systolic blood pressure was significantly higher in patients compared with controls (113 versus 107 mm Hg, P=0.002). Patients had reduced total arterial compliance, increased pulse wave velocity, and larger backward compression waves compared with controls. LVM index was significantly higher in patients than controls (72 versus 59 g/m2, P<0.0005). The magnitude of the backward compression waves was independently associated with variation in LVM (P=0.01). Using a novel, noninvasive hemodynamic assessment, we have shown abnormal conduit vessel function after coarctation of the aorta repair, including abnormal wave reflections that are associated with elevated LVM.

Magnetic Resonance–Augmented Cardiopulmonary Exercise TestingCLINICAL PERSPECTIVE: Comprehensively Assessing Exercise Intolerance in Children With Cardiovascular Disease

Background— Conventional cardiopulmonary exercise testing can objectively measure exercise intolerance but cannot provide comprehensive evaluation of physiology. This requires additional assessment of cardiac output and arteriovenous oxygen content difference. We developed magnetic resonance (MR)–augmented cardiopulmonary exercise testing to achieve this goal and assessed children with right heart disease. Methods and Results— Healthy controls (n=10) and children with pulmonary arterial hypertension (PAH; n=10) and repaired tetralogy of Fallot (n=10) underwent MR-augmented cardiopulmonary exercise testing. All exercises were performed on an MR-compatible ergometer, and oxygen uptake was continuously acquired using a modified metabolic cart. Simultaneous cardiac output was measured using a real-time MR flow sequence and combined with oxygen uptake to calculate arteriovenous oxygen content difference. Peak oxygen uptake was significantly lower in the PAH group (12.6±1.31 mL/kg per minute; P =0.01) and trended toward lower in the tetralogy of Fallot group (13.5±1.29 mL/kg per minute; P =0.06) compared with controls (16.7±1.37 mL/kg per minute). Although tetralogy of Fallot patients had the largest increase in cardiac output, they had lower resting (3±1.2 L/min per m2) and peak (5.3±1.2 L/min per m2) values compared with controls (resting 4.3±1.2 L/min per m2 and peak 6.6±1.2 L/min per m2) and PAH patients (resting 4.5±1.1 L/min per m2 and peak 5.9±1.1 L/min per m2). Both the PAH and tetralogy of Fallot patients had blunted exercise–induced increases in arteriovenous oxygen content difference. However, only the PAH patients had significantly reduced peak values (6.9±1.3 mlO2/100 mL) compared with controls (8.4±1.4 mlO2/100 mL; P =0.005). Conclusions— MR-augmented cardiopulmonary exercise testing is feasible in both healthy children and children with cardiac disease. Using this novel technique, we have demonstrated abnormal exercise patterns in oxygen uptake, cardiac output, and arteriovenous oxygen content difference.Background—Conventional cardiopulmonary exercise testing can objectively measure exercise intolerance but cannot provide comprehensive evaluation of physiology. This requires additional assessment of cardiac output and arteriovenous oxygen content difference. We developed magnetic resonance (MR)–augmented cardiopulmonary exercise testing to achieve this goal and assessed children with right heart disease. Methods and Results—Healthy controls (n=10) and children with pulmonary arterial hypertension (PAH; n=10) and repaired tetralogy of Fallot (n=10) underwent MR-augmented cardiopulmonary exercise testing. All exercises were performed on an MR-compatible ergometer, and oxygen uptake was continuously acquired using a modified metabolic cart. Simultaneous cardiac output was measured using a real-time MR flow sequence and combined with oxygen uptake to calculate arteriovenous oxygen content difference. Peak oxygen uptake was significantly lower in the PAH group (12.6±1.31 mL/kg per minute; P=0.01) and trended toward lower in the tetralogy of Fallot group (13.5±1.29 mL/kg per minute; P=0.06) compared with controls (16.7±1.37 mL/kg per minute). Although tetralogy of Fallot patients had the largest increase in cardiac output, they had lower resting (3±1.2 L/min per m2) and peak (5.3±1.2 L/min per m2) values compared with controls (resting 4.3±1.2 L/min per m2 and peak 6.6±1.2 L/min per m2) and PAH patients (resting 4.5±1.1 L/min per m2 and peak 5.9±1.1 L/min per m2). Both the PAH and tetralogy of Fallot patients had blunted exercise–induced increases in arteriovenous oxygen content difference. However, only the PAH patients had significantly reduced peak values (6.9±1.3 mlO2/100 mL) compared with controls (8.4±1.4 mlO2/100 mL; P=0.005). Conclusions—MR-augmented cardiopulmonary exercise testing is feasible in both healthy children and children with cardiac disease. Using this novel technique, we have demonstrated abnormal exercise patterns in oxygen uptake, cardiac output, and arteriovenous oxygen content difference.

Free breathing contrast-enhanced time-resolved magnetic resonance angiography in pediatric and adult congenital heart disease

BackgroundContrast enhanced magnetic resonance angiography (MRA) is generally performed during a long breath-hold (BH), limiting its utility in infants and small children. This study proposes a free-breathing (FB) time resolved MRA (TRA) technique for use in pediatric and adult congenital heart disease (CHD).MethodsA TRA sequence was developed by combining spiral trajectories with sensitivity encoding (SENSE, x4 kx-ky and x2 kz) and partial Fourier (75% in kz). As no temporal data sharing is used, an independent 3D data set was acquired every ~1.3s, with acceptable spatial resolution (~2.3x2.3x2.3mm). The technique was tested during FB over 50 consecutive volumes. Conventional BH-MRA and FB-TRA data was acquired in 45 adults and children with CHD. We calculated quantitative image quality for both sequences. Diagnostic accuracy was assessed in all patients from both sequences. Additionally, vessel measurements were made at the sinotubular junction (N = 43), proximal descending aorta (N = 43), descending aorta at the level of the diaphragm (N = 43), main pulmonary artery (N = 35), left pulmonary artery (N = 35) and the right pulmonary artery (N = 35). Intra and inter observer variability was assessed in a subset of 10 patients.ResultsBH-MRA had significantly higher homogeneity in non-contrast enhancing tissue (coefficient of variance, P <0.0001), signal-to-noise ratio (P <0.0001), contrast-to-noise ratio (P <0.0001) and relative contrast (P = 0.02) compared to the FB-TRA images. However, homogeneity in the vessels was similar in both techniques (P = 0.52) and edge sharpness was significantly (P <0.0001) higher in FB-TRA compared to BH-MRA. BH-MRA provided overall diagnostic accuracy of 82%, and FB-TRA of 87%, with no statistical difference between the two sequences (P = 0.77). Vessel diameter measurements showed excellent agreement between the two techniques (r = 0.98, P <0.05), with no bias (0.0mm, P = 0.71), and clinically acceptable limits of agreement (-2.7 to +2.8mm). Inter and intra observer reproducibility showed good agreement of vessel diameters (r>0.988, P<0.0001), with negligible biases (between -0.2 and +0.1mm) and small limits of agreement (between -2.4 and +2.5mm).ConclusionsWe have described a FB-TRA technique that is shown to enable accurate diagnosis and vessel measures compared to conventional BH-MRA. This simplifies the MRA technique and will enable angiography to be performed in children and adults whom find breath-holding difficult.

High-resolution slice-selective Fourier velocity encoding in congenital heart disease using spiral SENSE with velocity unwrap.

Quantification of peak velocity is important in the assessment of stenotic flow jets in patients with congenital heart disease. Phase‐contrast magnetic resonance underestimates peak velocities. Hence, clinically Doppler ultrasound is used as the reference standard for assessing stenoses. It is possible to accurately measure peak velocity in MR using Fourier velocity encoding (FVE). In this study, a fast, high‐resolution slice‐selective FVE sequence was developed with the use of spiral trajectories, parallel imaging, and partial Fourier in the velocity dimension and a novel velocity‐unwrap technique. The resulting sequence was acquired within a short breath‐hold (more than 15 heartbeats) making this FVE technique clinically achievable. Peak velocities were compared from Doppler ultrasound, phase‐contrast magnetic resonance, and FVE. Experiments were carried out in vitro and in vivo in 25 patients with congenital heart disease with stenoses. It was shown that in vitro and in vivo phase‐contrast magnetic resonance tended to underestimate peak velocity when compared with Doppler ultrasound, whereas FVE agreed well with Doppler ultrasound. Magn Reson Med, 2012.

Cardiovascular imaging in Turner syndrome: state-of-the-art practice across the lifespan

Cardiovascular imaging is essential to providing excellent clinical care for girls and women with Turner syndrome (TS). Congenital and acquired cardiovascular diseases are leading causes of the lifelong increased risk of premature death in TS. Non-invasive cardiovascular imaging is crucial for timely diagnosis and treatment planning, and a systematic and targeted imaging approach should combine echocardiography, cardiovascular magnetic resonance and, in select cases, cardiac CT. In recent decades, evidence has mounted for the need to perform cardiovascular imaging in all females with TS irrespective of karyotype and phenotype. This is due to the high incidence of outcome-determining lesions that often remain subclinical and occur in patterns specific to TS. This review provides an overview of state-of-the-art cardiovascular imaging practice in TS, by means of a review of the most recent literature, in the context of a recent consensus statement that has highlighted the role of cardiovascular diseases in these females.

Analysis of the septal curvature with CMR in the paediatric population with pulmonary hypertension is a useful tool

Background Paediatric pulmonary hypertension is often difficult to assess non-invasively. Early detection and treatment of mild disease in high-risk populations e.g. pulmonary disease is associated with improved outcome. In such cases, echocardiographic measurement of tricuspid regurgitation is unreliable for estimation of right heart pressure. Cardiac MR imaging offers an alternative, using deformation of the interventricular septum to assess the pressure differential between the ventricles. In this study, we hypothesised that this technique offers a useful tool for both detection of pulmonary hypertension and assessment of those with established disease. Methods Septal curvature ratio (SCR) at peak systole was analysed in twenty normal controls and twelve patients with diagnosed pulmonary hypertension. All patients underwent a joint cardiac catheterisation and MR procedure. Their pulmonary vascular resistance (PVR) was calculated using phase contrast measures and simultaneous pulmonary arterial (PAP) and capillary wedge pressures. SCR was measured at papillary muscle level in the mid ventricle from kt-SENSE short axis images, using regions of interest applied to the epicardial surfaces of the left ventricular free wall and right ventricular septal wall. [Fig 1] Pearson correlation coefficients of PVR and PAP with SCR were calculated. Sensitivity and specificity of the method were assessed using SCR measures from the control population. Results In PH patients, the median SCR was -0.05 (range: -0.390.35). PVR was strongly negatively correlated with SCR (r=-0.81, P= <0.05 [Fig 2]), as was the RV-LV pressure difference (r=-0.78, P=<0.05). Median SCR in normal controls was 1.02 (range: 0.9-1.09). Therefore for any threshold between 0.36 and 0.89, SCR had a sensitivity and specificity of 100% for the detection of any level of paediatric pulmonary hypertension. However, diagnostic power was less good for the differentiation of mild and severe PH (specificity 40%, sensitivity 75%). Conclusions This study shows that SCR is a sensitive tool for differentiating normal PVR from those with pulmonary hypertension in the paediatric population. Our approach took advantage of real-time kt-SENSE imaging of the ventricular short axis to reduce apnoea under anaesthesia in MR/catheter procedures. In routine MR, this sequence should make SCR measurement feasible in a wide age range of unsedated children, where scanning must often be rapid. SCR measurement in children is quick to perform and both sensitive and specific at identifying even mild disease. It was also noted that although there were strong correlations between SCR and measures of PAP and PVR, diagnostic differentiation was poor in established disease.

How to Image the Adult Patient With Fontan Circulation

A 32-year-old woman was seen for acute chest pain radiating to the neck and arms. The paramedical team witnessed her cardiac arrest on arrival and successfully defibrillated ventricular fibrillation by a single shock. After a stable transfer to the local hospital, she had a second witnessed arrest necessitating further defibrillation. History revealed good functional capacity and no other cardiac symptoms. Examination showed clear lungs, normal heart sounds, a normal abdomen, a blood pressure of 110/79 mm Hg, and an oxygen saturation of 100% (Figure I in the Data Supplement). The ECG showed signs of inferolateral infarction. Cardiac troponin I was 1.06 ng/mL. Telemetry confirmed intermittent nonsustained ventricular tachycardia and sinus bradycardia. Her medical therapy included bisoprolol 2.5 mg and warfarin (International Standardized Ratio, 1.7). Because of tricuspid atresia, transposition of the great arteries, pulmonary stenosis, and ventricular septum defect, she had undergone superior cavo-pulmonary shunt (Glenn) aged 4 years and atrio-pulmonary (Fontan) connection aged 7 years. Three years before, recurrent supraventricular tachycardia necessitated multiple electrophysiological studies, with ablation of focal right atrial tachycardias and cavo-tricuspid isthmus-dependent flutter. Echocardiography showed preserved ventricular function, mild flow acceleration across the subaortic ventricular septum defect, mild mitral regurgitation, as well as dilated systemic and hepatic veins (Movies V and VI in the Data Supplement). Computed tomography (CT) of the pulmonary arteries (PA; computed tomography pulmonary angiogram) was subsequently performed, reporting a large opacification defect in the proximal left PA, suggestive of pulmonary embolism (Figure 1). Cardiac magnetic resonance imaging (CMR) thereafter showed a patent Fontan pathway, no thrombi, and normal pulmonary arborization. The coronary sinus, the right atrial, the cardiac, hepatic, and the systemic veins were severely distended (inferior vena cava; Figures 2 and 3; Movies I-III in the Data Supplement), with diastolic flow reversal in the inferior vena cava. No systemic-to-pulmonary collaterals (SPC) …

CMR DERIVED CENTRAL AORTIC SYSTOLIC PRESSURE IS A SUPERIOR PREDICTOR OF AFTERLOAD IN REPAIRED COARCTATION

Background: Hypertension is one of the major causes of late mortality in patients with repaired coarctation of the aorta (CoA) even in the absence of significant recoarctation. However, brachial systolic pressure (BSP) may not accurately reflect central systolic pressure (CASP), which is the driver of pathology. Recently, it has been shown that it is possible to accurately estimate CASP using CMR data and a simple exponential model of the arterial pressure-area relationship. The aims of this study were i) To demonstrate that it is feasible to measure CASP in patients with CoA and ii) To demonstrate that CASP is a better indicator of afterload represented by increased LV mass (LVM); compared with conventional metrics, such as coarctation index (CI) and BSP.

Free breathing contrast-enhanced time-resolved magnetic resonance angiography in congenital heart disease.

Background Contrast enhanced magnetic resonance angiography (MRA) is generally performed during a long breath-hold (BH), limiting its use in infants and children. Time resolved MR angiography (TRA) often use data sharing techniques, making it is necessary to acquire data during a BH. This study proposes a high-resolution free breathing (FB) TRA sequence for use in adults and children with congenital heart disease (CHD).