Review of the role of cardiovascular magnetic resonance in congenital heart disease, with a focus on right ventricle assessment.

Adult patients with congenital heart disease (ACHD) represent a growing population due to progress in management. Surgical procedures generally fall short of restoring entirely normal anatomical and functional relations. Further procedures can be needed and lifelong follow-up is required. The right ventricle (RV) plays an important role in congenital heart disease and cardiac magnetic resonance (CMR) imaging has become the imaging method of choice for its assessment. CMR can provide relatively accurate measurements of RV volume and function, and arterial flow, with additional anatomical information provided by three-dimensional contrast angiography and late gadolinium imaging of fibrosis. Here we focus our review on three categories of ACHD in which evaluation of the RV is important: repaired tetralogy of Fallot, the systemic RV and Ebstein anomaly. We demonstrate how CMR contributes to decision-making regarding the types and timings of interventions. A dedicated CMR service should be regarded as a necessary facility of a centre specializing in the care of ACHD patients.

Integrated morphologic and functional assessment of the aortic root after different tissue valve root replacement procedures.

OBJECTIVES: This study was undertaken to explore aspects of the hemodynamic function of different biologic tissue aortic valve root replacements. We set out to image and display the spatiotemporal distributions of axially directed blood velocity through the aortic root. METHODS: The flow velocities through a plane transecting the aortic root were measured by 2-dimensional cine phase-contrast magnetic resonance velocity mapping in 44 subjects: 29 patients who had undergone aortic root replacement approximately 10 years previously (13 autografts, 10 stentless xenografts, and 6 homografts) and 15 healthy control subjects. With cine as well as velocity images, aortic sinus dimensions, effective orifice area, and several velocity parameters were measured. Color-coded plots of velocity relative to the sinus cross sections and velocity-time plots were used to compare spatiotemporal distributions of velocity. RESULTS: Peak flow velocity was similar between the autografts (102 ± 28.0 cm/s) and control valves (119 ± 20.0 cm/s) but was higher in xenografts (167 ± 36.0 cm/s) and homografts (206 ± 91.0 cm/s). These measurements showed an inverse relationship with the effective orifice area (7.27 ± 0.20, 4.24 ± 0.81, 3.37 ± 0.32, and 3.28 ± 0.87 cm(2), respectively). Autograft peak flow velocity showed no significant difference from control valve peak flow velocity, despite larger root dimensions (P < .001). The graphic displays provided further spatiotemporal information. CONCLUSIONS: Peak velocities and spatiotemporal flow patterns depend on the type of valve substitute. In the parameters measured, autograft replacements differed least from normal aortic valves.

Cardiovascular magnetic resonance tagging of the right ventricular free wall for the assessment of long axis myocardial function in congenital heart disease.

BACKGROUND: Right ventricular ejection fraction (RV-EF) has traditionally been used to measure and compare RV function serially over time, but may be a relatively insensitive marker of change in RV myocardial contractile function. We developed a cardiovascular magnetic resonance (CMR) tagging-based technique with a view to rapid and reproducible measurement of RV long axis function and applied it in patients with congenital heart disease. METHODS: We studied 84 patients: 56 with repaired Tetralogy of Fallot (rTOF); 28 with atrial septal defect (ASD): 13 with and 15 without pulmonary hypertension (RV pressure > 40 mmHG by echocardiography). For comparison, 20 healthy controls were studied. CMR acquisitions included an anatomically defined four chamber cine followed by a cine gradient echo-planar sequence in the same plane with a labelling pre-pulse giving a tag line across the basal myocardium. RV tag displacement was measured with automated registration and tracking of the tag line together with standard measurement of RV-EF. RESULTS: Mean RV displacement was higher in the control (26 ± 3 mm) than in rTOF (16 ± 4 mm) and ASD with pulmonary hypertension (18 ± 3 mm) groups, but lower than in the ASD group without (30 ± 4 mm), P < 0.001. The technique was reproducible with inter-study bias ± 95% limits of agreement of 0.7 ± 2.7 mm. While RV-EF was lower in rTOF than in controls (49 ± 9% versus 57 ± 6%, P < 0.001), it did not differ between either ASD group and controls. CONCLUSIONS: Measurements of RV long axis displacement by CMR tagging showed more differences between the groups studied than did RV-EF, and was reproducible, quick and easy to apply. Further work is needed to assess its potential use for the detection of longitudinal changes in RV myocardial function.

A single, comprehensive non-invasive cardiovascular assessment in pulmonary arterial hypertension: combined computed tomography pulmonary and coronary angiography.

BACKGROUND: Comprehensive assessment of pulmonary arterial hypertension (PAH) should identify structural causes and subsequent cardiopulmonary consequences of PAH. This currently requires the use of several imaging modalities. Computed tomography (CT) is routinely used for pulmonary angiography (CTPA). Our aim was to assess whether combined pulmonary and coronary angiography (CTPCA) using ECG-gated, multi-detector CT (MDCT) would allow satisfactory pulmonary angiography, coronary angiography and ventriculography to be combined into a single acquisition using a single imaging modality. METHODS: We assessed CTPCA in 30 consecutive adult patients (mean age 41+/-11 years) with a diagnosis of PAH. In addition to the standard assessment of lung parenchyma and pulmonary vasculature, we assessed the ability of CT to satisfactorily visualise coronary vessels and biventricular function. Functional analysis included: end-diastolic volume (EDV), end-systolic volume (EDV), stroke volume (SV) and ejection fraction (EF) and mass and these parameters were correlated with same day cardiovascular magnetic resonance (CMR). RESULTS: Lung parenchyma, pulmonary and coronary vessels were fully visualised in all cases. Ventriculography correlated well with same day CMR (RVEDV r=0.94, +19.5+/-49.2 ml, RVESV r=0.93, +11.1+/-46.4 ml, RVSV r=0.60, +8.5+/-41.6 ml, RVEF r=0.77, -0.5+/-21.3% and RV mass r=0.73, -17.3+/-60.4 g, LVEDV r=0.68, +12.2+/-110 ml, LVESV r=0.69, +7.5+/-59.7 ml, LVSV r=0.54, +2.5+/-40.6 ml, LVEF r=0.73, -1.9+/-20.8% and LV mass r=0.87, -20.5+/-22.5 g (all p<0.001)). Associated congenital cardiovascular malformations were characterised in 22/30 cases. CONCLUSIONS: A CTPCA protocol allows safe, fast, comprehensive, non-invasive assessment of the possible anatomical causes and cardiopulmonary sequelae of PAH in adult patients, demonstrating congenital heart abnormalities, coronary artery disease and cardiac function.

Towards comprehensive assessment of mitral regurgitation using cardiovascular magnetic resonance.

Cardiovascular magnetic resonance (CMR) is increasingly used to assess patients with mitral regurgitation. Its advantages include quantitative determination of ventricular volumes and function and the mitral regurgitant fraction, and in ischemic mitral regurgitation, regional myocardial function and viability. In addition to these, identification of leaflet prolapse or restriction is necessary when valve repair is contemplated. We describe a systematic approach to the evaluation of mitral regurgitation using CMR which we have used in 149 patients with varying etiologies and severity of regurgitation over a 15 month period. Following standard ventricular cine acquisitions, including 2, 3 and 4 chamber long axis views and a short axis stack for biventricular function, we image movements of all parts of the mitral leaflets using a contiguous stack of oblique long axis cines aligned orthogonal to the central part of the line of coaptation. The 8-10 slices in the stack, orientated approximately parallel to a 3-chamber view, are acquired sequentially from the superior (antero-lateral) mitral commissure to the inferior (postero-medial) commissure, visualising each apposing pair of anterior and posterior leaflet scallops in turn (A1-P1, A2-P2 and A3-P3). We use balanced steady state free precession imaging at 1.5 Tesla, slice thickness 5 mm, with no inter-slice gaps. Where the para-commissural coaptation lines curve relative to the central region, two further oblique cines are acquired orthogonal to the line of coaptation adjacent to each commissure. To quantify mitral regurgitation, we use phase contrast velocity mapping to measure aortic outflow, subtracting this from the left ventricular stroke volume to calculate the mitral regurgitant volume which, when divided by the left ventricular stroke volume, gives the mitral regurgitant fraction. In patients with ischemic mitral regurgitation, we further assess regional left ventricular function and, with late gadolinium enhancement, myocardial viability. Comprehensive assessment of mitral regurgitation using CMR is feasible and enables determination of mitral regurgitation severity, associated leaflet prolapse or restriction, ventricular function and viability in a single examination and is now routinely performed at our centre. The mitral valve stack of images is particularly useful and easy to acquire.

Doppler-echocardiographic assessment of pulmonary regurgitation in adults with repaired tetralogy of Fallot: comparison with cardiovascular magnetic resonance imaging.

AIMS: The purpose of this study was to compare the noninvasive assessment of severity of pulmonary regurgitation with Doppler echocardiography versus cardiovascular magnetic resonance imaging (CMR) in adult patients with repaired tetralogy of Fallot (rTOF). METHODS: We studied 52 (22 females) consecutive patients (aged 32 +/- 2 years, 23 +/- 5 years after rTOF) using Doppler echocardiography and compared these findings with CMR. From the continuous-wave Doppler trace, the duration of pulmonary regurgitation and of total diastole was measured and the ratio between the 2 was defined as pulmonary regurgitation index (PRi). Pulmonary regurgitant fraction (PRF) was assessed with flow phase velocity mapping with CMR. RESULTS: Patients were divided into 2 groups according to the median value (24.5%) of PRF measured by CMR: Group I (26 patients) with PRF < or =24.5% and Group II with PRF >24.5%. There was no difference between patients' age, sex, or age at repair between the 2 groups. More patients from Group II had a right ventricular outflow or transannular patch repair compared to Group I (12/26 [46%] vs 6/26 [23%], P <.01). Mean pulmonary regurgitation time was shorter (340 +/- 60 vs 440 +/- 135 ms, P =.001) and PRi was lower (0.61 +/- 0.11 vs 0.91 +/- 0.11, P <.001) in Group II compared to Group I. Color Doppler regurgitant jet was also broader in Group II (1.4 +/- 0.4 vs 0.7 +/- 0.5 cm, P <.001), signifying more severe pulmonary regurgitation. Doppler-measured PRi correlated closely with CMR regurgitant fraction (r = -0.82, P <.001) and with color Doppler pulmonary regurgitant jet width (r = -0.66, P <.001); the latter correlated with PRF assessed with CMR (r = 0.72, P <.001). A PRi <0.77 had 100% sensitivity and 84.6% specificity for identifying patients with pulmonary regurgitant fraction >24.5%, with a predictive accuracy of 95%. Furthermore, echocardiographically-assessed right ventricular end-diastolic dimensions correlated with CMR end-diastolic volume index (r = 0.49, P <.001 ). CONCLUSIONS: Pulmonary regurgitation is common in asymptomatic adults with rTOF. Severity of pulmonary regurgitation and its effects on right ventricular dimensions in these patients can be assessed noninvasively by Doppler echocardiography and CMR, with reasonable agreement between the 2 techniques.