Usefulness of MRI in the follow-up of patients with repaired aortic coarctation and bicuspid aortic valve

4D flow MRI derived aortic hemodynamics multi-year follow-up in repaired coarctation with bicuspid aortic valve

PURPOSE

The purpose of this study was to investigate the relationships between hemodynamic parameters and longitudinal changes in aortic dimensions on four-dimensional (4D) flow magnetic resonance imaging (MRI) in patients with bicuspid aortic valve (BAV) and repaired coarctation.

MATERIALS AND METHODS

The study retrospectively included patients with BAV and childhood coarctation repair who had at least two cardiothoracic MRI examinations including 4D flow MRI at baseline and follow-up. Analysis included the calculation of aortic peak velocities, wall shear stress (WSS), pulse wave velocity (PWV), aortic dimensions and annual growth rates. Differences between examinations were assessed using paired t-test or Wilcoxon signed rank test. Relationships between growth rate and 4D flow metrics were assessed using Pearson or Spearman correlation tests.

RESULTS

The cohort included 15 patients (mean age 35 ± 8 [SD] years, 9 men) with a median follow-up time of 3.98 years (Q1: 2.10; Q3: 4.96). There were no significant differences in aortic mean WSS, peak velocities, and PWV between baseline and follow-up values. Greater baseline peak velocities at the site of the coarctation were strongly associated with aortic narrowing (follow-up vs. baseline diameter) at coarctation zone (r = -0.64; P = 0.010) and moderately in descending aorta (r = -0.53; P = 0.042). In addition, increased baseline WSS in the aortic arch was strongly related with narrowing of the coarctation zone at follow-up (r = -0.64, P = 0.011).

CONCLUSION

Measures of aortic hemodynamics and aortic WSS are stable over time in patients with BAV with coarctation repair. Increased peak velocity was associated with a progressive narrowing at the site of the coarctation repair.

Clinical and pathophysiological aspects of bicuspid aortic valve disease

A bicuspid aortic valve is not only a common congenital heart defect but also an enigmatic condition that can cause a large spectrum of diseases, such as aortic valve stenosis and severe heart failure in newborns whereas aortic dissection in adults. On the contrary, a bicuspid aortic valve can also occur with normal function throughout life and never need treatment. Numerous genetic mechanisms are involved in the abnormal cellular functions that may cause abnormal development of the aortic valve during early foetal life. As several chromosomal disorders are also associated with a bicuspid valve, there does not appear to be an apparent common trigger to the abnormal development of the aortic valve. The clinical care of the bicuspid aortic valve patient has been changed by a significant body of evidence that has improved the understanding of the natural history of the disease, including when to best intervene with valve replacement and when to provide prophylactic aortic root surgery. Moreover, as bicuspid valve disease is also part of various syndromes, we can identify high-risk patients in whom a bicuspid valve is much more unfavourable than in the normal population. This review provides an overview of all aspects of the bicuspid aortic valve condition and gives an updated perspective on issues from pathophysiology to clinical care of bicuspid aortic valve disease and associated aortic disease in asymptomatic, symptomatic, and pregnant patients, as well as our viewpoint on population screening.

Ascending aortic size in aortic coarctation depends on aortic valve morphology: Understanding the bicuspid valve phenotype

BACKGROUND

In roughly half of patients with coarctation of the aorta (CoA), the aorta may be enlarged. It is uncertain whether enlargement is independent of aortic valve morphology. We sought to compare aortic size in CoA with a tricuspid valve (TAV) to those with bicuspid aortic valve (BAV).

METHODS

Sixty-eight CoA patients and 20 healthy controls with prior cardiac magnetic resonance (CMR) imaging were included. CMR was retrospectively reanalyzed to measure aortic root and mid-ascending aorta. The maximum aortic diameter was compared between CoA with TAV, CoA with BAV, and control groups.

RESULTS

CoA with TAV patients (n=27) had smaller aortic root diameters than CoA with BAV (n=41) (32±4.9 vs. 37±5.8mm, p=0.001), despite being older (40 vs. 32years, p=0.01). Similarly, TAV CoA patients had a smaller mid-ascending aortic diameter (28±4.5 vs. 33±6.9mm, p=0.019) than BAV patients. TAV CoA was similar to controls in all metrics. Twenty-four patients (35%) with CoA had dilated aortas (>37mm), of which 79% had BAV. A history of hypertension did not predict larger aortic root or mid-ascending aortic dimensions.

CONCLUSIONS

In patients with CoA, TAV is associated with smaller aortic size compared to those with BAV, and similar to healthy controls. Aortic size in CoA is independent of hypertension. Therefore, aortopathy associated with BAV is likely a reflection of the BAV phenotype rather than CoA or its physiologic effects. This distinction may have implications for the frequency and types of monitoring and treatment of CoA patients.

Cardiovascular magnetic resonance: applications in daily practice

Over the last 10 years, the development of newer pulse sequences and applications in new clinical areas has enabled cardiovascular magnetic resonance to emerge as a powerful tool for the physicians to both diagnose and guide treatments of various cardiac pathologies. The greatest strengths of cardiovascular magnetic resonance include the assessment of ischemia and viability, evaluation of nonischemic cardiomyopathies, including myocarditis, pericardial disease, congenital heart disease, and tissue characterization of cardiac masses.

Late magnetic resonance surveillance of repaired coarctation of the aorta

OBJECTIVE

Coarctation of the aorta has often been described as a simple form of congenital heart disease. However, rates of re-coarctation reported in the literature vary from 7% to 60%. Re-coarctation of the aorta may lead to worsening systemic hypertension, coronary artery disease and/or congestive cardiac failure. We aimed to describe the rates of re-coarctation in subjects who had undergone early coarctation repair (<2 years of age) and referred for clinically indicated or routine magnetic resonance (MR) surveillance.

METHODS

We retrospectively identified 50 consecutive subjects (20.2+/-6.9 years post-repair) imaged between 2004 and 2008. Patient characteristics, rates of re-coarctation and LV/aortic dimensions were examined.

RESULTS

Forty percent of subjects had bicuspid aortic valves (BAV). There were 40 cases of end-to-end repair and 10 cases of subclavian flap repair. Re-intervention with balloon angioplasty or repeat surgery had been performed in 32% of subjects. The MRI referrals were clinically indicated in 34% and routine in 66% of patients. Re-coarctation was considered moderate or severe in 34%, mild in 34% and no re-coarctation was identified in 32% of patients. There was no significant difference in the number of cases of re-coarctation identified in the clinically indicated versus routine referrals for MR imaging (p=0.20). There were no cases of aortic dissection or aneurysm formation identified amongst the subjects. The mean indexed left ventricular mass and ejection fraction was 72+/-16g/m(2) and 66+/-6%, respectively. Amongst those subjects with BAV there were larger aortic sinus (30+/-1mm vs 27+/-1mm, p=0.03) and ascending aortic (27+/-1mm vs 23+/-1mm, p=0.01) dimensions when compared to subjects with morphologically tricuspid aortic valves.

CONCLUSIONS

We demonstrate that many years after early repair of coarctation of the aorta, MR surveillance detects significant rates of re-coarctation. These findings were independent of whether or not there was a clinical indication for imaging. Those patients with BAV disease had larger ascending aortic dimensions and may require more frequent non-invasive surveillance.

Approach to the patient with bicuspid aortic valve and ascending aorta aneurysm

Bicuspid aortic valve (BAV) disease is a common congenital heart valve abnormality accounting for a large number of valve replacements in the United States. Although still incompletely understood, the natural history of BAV disease is severe aortic stenosis and associated ascending aortic dilatation. In addition to the increased risk of endocarditis, aortic dissection and severe aortic valve dysfunction are responsible for most fatal complications. Thus, early and precise recognition of this condition is mandatory. The new American College of Cardiology/American Heart Association recommendations highlight the role of MRI and CT as complimentary tools to echocardiography for the diagnosis and surveillance of the morphology of the aortic valve and ascending aorta. Moreover, better understanding of the cellular mechanisms, including inflammation, bone formation, atherosclerotic-like processes, and aortic wall abnormalities, as well as the heritability and genetic predisposition for the disease, will define the potential for targeted medical therapies in the future. Currently, the treatment of this condition is primarily surgical. Although combined valve and ascending aorta replacement has been the most common surgical approach in the past, the increased cumulative risk of thrombotic and embolic events among these young patients has led to more conservative approaches. Several valve-sparing approaches with comparable mid-term results compared with the classic procedures have recently been reported. However, longer follow-up studies will be helpful to better define the advantages of these new surgical options. After a quick overview of the natural history of the BAV, this article provides an updated approximation of the current knowledge of the pathophysiology as well as the recommendations for the management and treatment of this disease.