Mieke M. P. Driessen

Advances in cardiac magnetic resonance imaging of congenital heart disease

Due to advances in cardiac surgery, survival of patients with congenital heart disease has increased considerably during the past decades. Many of these patients require repeated cardiovascular magnetic resonance imaging to assess cardiac anatomy and function. In the past decade, technological advances have enabled faster and more robust cardiovascular magnetic resonance with improved image quality and spatial as well as temporal resolution. This review aims to provide an overview of advances in cardiovascular magnetic resonance hardware and acquisition techniques relevant to both pediatric and adult patients with congenital heart disease and discusses the techniques used to assess function, anatomy, flow and tissue characterization.

Adverse ventricular–ventricular interactions in right ventricular pressure load: Insights from pediatric pulmonary hypertension versus pulmonary stenosis

Right ventricular (RV) pressure overload has a vastly different clinical course in children with idiopathic pulmonary arterial hypertension (iPAH) than in children with pulmonary stenosis (PS). While RV function is well recognized as a key prognostic factor in iPAH, adverse ventricular–ventricular interactions and LV dysfunction are less well characterized and the pathophysiology is incompletely understood. We compared ventricular–ventricular interactions as hypothesized drivers of biventricular dysfunction in pediatric iPAH versus PS. Eighteen iPAH, 16 PS patients and 18 age‐ and size‐matched controls were retrospectively studied. Cardiac cycle events were measured by M‐mode and Doppler echocardiography. Measurements were compared between groups using ANOVA with post hoc Dunnets or ANCOVA including RV systolic pressure (RVSP; iPAH 96.8 ± 25.4 mmHg vs. PS 75.4 ± 18.9 mmHg; P = 0.011) as a covariate. RV‐free wall thickening was prolonged in iPAH versus PS, extending beyond pulmonary valve closure (638 ± 76 msec vs. 562 ± 76 msec vs. 473 ± 59 msec controls). LV and RV isovolumetric relaxation were prolonged in iPAH (P < 0.001; LV 102.8 ± 24.1 msec vs. 63.1 ± 13.7 msec; RV 95 [61–165] vs. 28 [0–43]), associated with adverse septal kinetics; characterized by rightward displacement in early systole and leftward displacement in late RV systole (i.e., early LV diastole). Early LV diastolic filling was decreased in iPAH (73 ± 15.9 vs. PS 87.4 ± 14.4 vs. controls 95.8 ± 12.5 cm/sec; P = 0.004). Prolonged RVFW thickening, prolonged RVFW isovolumetric times, and profound septal dyskinesia are associated with interventricular mechanical discoordination and decreased early LV filling in pediatric iPAH much more than PS. These adverse mechanics affect systolic and diastolic biventricular efficiency in iPAH and may form the basis for worse clinical outcomes. We used clinically derived data to study the pathophysiology of ventricular–ventricular interactions in right ventricular pressure overload, demonstrating distinct differences between pediatric pulmonary arterial hypertension (iPAH) and pulmonary stenosis (PS). Altered timing of right ventricular free wall contraction and profound septal dyskinesia are associated with interventricular mechanical discoordination and decreased early LV filling in iPAH much more than PS. These adverse mechanics affect systolic and diastolic biventricular efficiency, independent of right ventricular systolic pressure.

Main pulmonary artery area limits exercise capacity in patients long-term after arterial switch operation

OBJECTIVES Despite excellent survival in patients after the arterial switch operation, reintervention is frequently required and exercise capacity is decreased in a substantial number of patients. This study relates right-sided imaging features in patients long-term after the arterial switch operation to exercise capacity and ventilatory efficiency to investigate which lesions are functionally important. METHODS Patients operated in the UMC Utrecht, the Netherlands (1976-2001) and healthy controls underwent cardiac magnetic resonance imaging and cardiopulmonary exercise testing within 1 week. We measured main, left, and right pulmonary artery cross-sectional areas, pulmonary blood flow distribution, peak oxygen uptake, and minute ventilation relative to carbon dioxide elimination. RESULTS A total of 71 patients (median age, 20 [12-35] years, 73% were male) and 21 healthy controls (median age, 26 [21-35] years, 48% were male) were included. Main, left, and right pulmonary artery areas were decreased compared with controls (190 vs 269 mm(2)/m(2), 59 vs 157 mm(2)/m(2), 98 vs 139 mm(2)/m(2), respectively, all P < .001); however, pulmonary blood flow distribution was comparable (P = .722). Peak oxygen uptake and minute ventilation relative to carbon dioxide elimination were 88% ± 20% and 23.7 ± 3.8, respectively, with 42% and 1% of patients demonstrating abnormal results (≤ 84% and ≥ 34, respectively). The main pulmonary artery area significantly correlated with peak oxygen uptake (r = 0.401, P = .001) and pulmonary blood flow distribution with minute ventilation relative to carbon dioxide elimination (r = -0.329, P = .008). Subanalysis (<18, 18-25, >25 years) showed that the main pulmonary artery area was smaller in older age groups. In multivariable analysis, the main pulmonary artery area was independently associated with peak oxygen uptake (P = .032). CONCLUSIONS In adult patients after the arterial switch operation, narrowing of the main pulmonary artery is a common finding and is the main determinant of limitation in functional capacity, rather than pulmonary branch stenosis.

Knowledge based 3D reconstruction of the right ventricle: comparison with cardiac magnetic resonance in adults with congenital heart disease

Aim Assessment of right ventricular (RV) function is a challenge, especially in patients with congenital heart disease (CHD). The aim of the present study is to assess whether knowledge-based RV reconstruction, used in the everyday practice of an echo-lab for adult CHD in a tertiary referral center, is accurate when compared to cardiac magnetic resonance (CMR) examination. Subjects and methods Adult patients who would undergo CMR for assessment of the RV were asked to undergo an echo of the heart for further knowledge-based reconstruction (KBR). Echocardiographic images were acquired in standard views using a predefined imaging protocol. RV volumes and ejection fraction (EF) calculated using knowledge-based technology were compared with the CMR data of the same patient. Results Nineteen consecutive patients with congenital right heart disease were studied. Median age of the patients was 28 years (range 46 years). Reconstruction was possible in 16 out of 19 patients (85%). RV volumes assessed with this new method were smaller than with CMR. Indexed end diastolic volumes were 114±17 ml vs 121±19 ml, P<0.05 and EFs were 45±8% vs 47±9%, P<0.05 respectively. The correlation between the methods was good with an intraclass correlation of 0.84 for EDV and 0.89 for EF, P value <0.001 in both cases. Conclusion KBR enables reliable measurement of RVs in patients with CHDs and can be used in clinical practice for analysis of volumes and EFs.

RV adaptation to increased afterload in congenital heart disease and pulmonary hypertension

Background The various conditions causing a chronic increase of RV pressure greatly differ in the occurrence of RV failure, and in clinical outcome. To get a better understanding of the differences in outcome, RV remodeling, longitudinal function, and transverse function are compared between patients with pulmonary stenosis (PS), those with a systemic RV and those with pulmonary hypertension (PH). Materials and methods This cross-sectional study prospectively enrolled subjects for cardiac magnetic resonance imaging (CMR), functional echocardiography and cardiopulmonary exercise testing. The study included: controls (n = 37), patients with PS (n = 15), systemic RV (n = 19) and PH (n = 20). Statistical analysis was performed using Analysis of Variance (ANOVA) with posthoc Bonferroni. Results PS patients had smaller RV volumes with higher RV ejection fraction (61.1±9.6%; p<0.05) compared to controls (53.8±4.8%). PH and systemic RV patients exhibited dilated RVs with lower RV ejection fraction (36.9±9.6% and 46.3±10.1%; p<0.01 versus controls). PH patients had lower RV stroke volume (p = 0.02), RV ejection fractions (p<0.01) and VO2 peak/kg% (p<0.001) compared to systemic RV patients. Mean apical transverse RV free wall motion was lower and RV free wall shortening (p<0.001) was prolonged in PH patients–resulting in post-systolic shortening and intra-ventricular dyssynchrony. Apical transverse shortening and global longitudinal RV deformation showed the best correlation to RV ejection fraction (respectively r = 0.853, p<0.001 and r = 0.812, p<0.001). Conclusions RV remodeling and function differed depending on the etiology of RV pressure overload. In contrast to the RV of patients with PS or a systemic RV, in whom sufficient stroke volumes are maintained, the RV of patients with PH seems unable to compensate for its increase in afterload completely. Key mediators of RV dysfunction observed in PH patients, were: prolonged RV free wall shortening, resulting in post-systolic shortening and intra-ventricular dyssynchrony, and decreased transverse function.

Pressure overloaded right ventricles: importance of trabeculae in evaluation of RV function by CMR

Background Cardiac magnetic resonance imaging (CMR) is the preferred method to evaluate right ventricular (RV) volumes and ejection fraction. In CMR-volumetry, trabeculae and papillary muscles can be either in- or excluded from the blood volume and both methods are used throughout literature. This study aimed to determine the impact of trabeculae and papillary muscles on right ventricular (RV) volumes and function assessed by CMR in different patient groups with pressure overloaded RVs using semi-automatic software and to determine the reproducibility of this method. Methods Four groups of 20 patients (pulmonary hypertension, arterial switch operation (ASO), Tetralogy of Fallot (TOF), systemic RV) and 20 healthy subjects underwent shortaxis multislice cine CMR. End diastolic volume (EDV), end systolic volume (ESV), RV mass and ejection fraction (EF) were measured using 2 methods. First, only manual contour tracing of the endo and epicardial borders was performed thus including trabeculae in the blood volume (method 1). With method 2, trabeculae were excluded from the blood volume using semi-automatic pixel-intensity based software. Differences in EDV, ESV volumes, RVEF and RV mass after excluding trabeculae were tested using paired samples T-test. For intra- and interobserver agreement 25 datasets were re-analyzed.