Main pulmonary artery dilation in association with congenital bicuspid aortic valve in the absence of pulmonary valve abnormality

Understanding Pulmonary Autograft Remodeling After the Ross Procedure: Stick to the Facts

The Ross, or pulmonary autograft, procedure presents a fascinating mechanobiological scenario. Due to the common embryological origin of the aortic and pulmonary root, the conotruncus, several authors have hypothesized that a pulmonary autograft has the innate potential to remodel into an aortic phenotype once exposed to systemic conditions. Most of our understanding of pulmonary autograft mechanobiology stems from the remodeling observed in the arterial wall, rather than the valve, simply because there have been many opportunities to study the walls of dilated autografts explanted at reoperation. While previous histological studies provided important clues on autograft adaptation, a comprehensive understanding of its determinants and underlying mechanisms is needed so that the Ross procedure can become a widely accepted aortic valve substitute in select patients. It is clear that protecting the autograft during the early adaptation phase is crucial to avoid initiating a sequence of pathological remodeling. External support in the freestanding Ross procedure should aim to prevent dilatation while simultaneously promoting remodeling, rather than preventing dilatation at the cost of vascular atrophy. To define the optimal mechanical properties and geometry for external support, the ideal conditions for autograft remodeling and the timeline of mechanical adaptation must be determined. We aimed to rigorously review pulmonary autograft remodeling after the Ross procedure. Starting from the developmental, microstructural and biomechanical differences between the pulmonary artery and aorta, we review autograft mechanobiology in relation to distinct clinical failure mechanisms while aiming to identify unmet clinical needs, gaps in current knowledge and areas for further research. By correlating clinical and experimental observations of autograft remodeling with established principles in cardiovascular mechanobiology, we aim to present an up-to-date overview of all factors involved in extracellular matrix remodeling, their interactions and potential underlying molecular mechanisms.

Three cusps are better than two: bicuspid aortic valve and implications for military service

Bicuspid aortic valve (BAV) is the most common congenital cardiac malformation. It is an aortopathy and is associated with other congenital heart disease. Although there is no mortality increase with BAV, the natural history increases the risk of aortic valve disease, aortic dilatation and infective endocarditis over the time frame of a full military career. Military service theoretically increases the risk of aortic dilatation and endocarditis in BAV. Conversely, there are some who have BAV who would not suffer any complications during their military career. Currently, potential UK Army recruits undergo personal/family history and physical examination plus an ECG and, although this goes beyond American Heart Association guidelines, it does not screen specifically for BAV. This would necessitate a transthoracic echo for each potential recruit but would be a considerable increase in resources-both time and financial. In addition to the recruitment medical, military personnel undergo frequent medicals, which could identify those who develop significant valvular disease. Those with mild valve disease are at lowest risk of complication. Those with aortic dilatation only remain a concern.

On the prospect of serum exosomal miRNA profiling and protein biomarkers for the diagnosis of ascending aortic dilatation in patients with bicuspid and tricuspid aortic valve

BACKGROUND

To determine the impact of circulating miRNA and protein activity on the severity of ascending aortic dilatation in patients with bicuspid (BAV) and tricuspid aortic valve (TAV).

METHODS

By reverse transcription polymerase chain reaction, exosomal circulating expression levels (versus healthy aorta) of miRNAs and absolute levels of transforming growth factor β (TGF-β), matrix metalloproteinases (MMP-2, -3 and -9), tissue inhibitors (TIMP-1, -2, -3 and -4), and soluble receptors for advanced glycation end products AGEs (sRAGE) were evaluated in ascending dilated aortas of 71 patients with different valve morphotype.

RESULTS

Less-dilated ascending aorta exhibited a specific miRNA signature (i.e., miR-126 miR-15b, miR-195, miR-221, miR24, miR-30b and miR-320a), which was statistically different from that of severely-dilated ascending aorta. Among these analytes, miR-15b was the most significant (p < 0.001) and resulted as an independent predictor of aortic dilatation (β = -1.099, p = 0.041). When patients were grouped according to aortic valve morphology, miRNAs and protein proteolytic activity were different between BAV and TAV in the expression level of miR-133a, miR-155, miR-320a, miR-34a_(#000425), miR-34a_(#000426), miR-494 and measurements of TGF-β and MMP-3, MMP-9, TIMP-4. The circulating level of miR-34a_(#000426) was negatively correlated to the aortic wall elasticity of bicuspid patients (R = -0.653 and p = 0.011), suggesting an apparent different mechanism of aortic wall degeneration specific for BAV.

CONCLUSIONS

Taken these biomarkers together, we demonstrated that the severity of aortic size and valve morphology differently modulates miRNA analytes and protein proteolytic activity in patients with ascending aortic dilatation, and this may be useful to design new therapies that inhibit miRNAs.

Prevalence and prognostic significance of pulmonary artery aneurysms in adults with congenital heart disease

BACKGROUND

Prevalence and prognostic significance of pulmonary artery (PA) dilatation in congenital heart disease (CHD) have never been studied systematically.

METHODS

Chest X-rays of 1192 consecutive adults with CHD were reviewed. Major diameter of the PA was determined by imaging techniques in those with PA dilatation. A value >29 mm was considered abnormal. Data on anatomy, hemodynamics, residual lesions and outcomes were retrospectively collected.

RESULTS

Overall prevalence of PA dilatation was 18%. A minority of patients (5.5%) reached 40 mm (aneurysm; PAA) and 1.8% exceeded 50 mm. The most common PAA underlying malformations were pulmonary stenosis (21%), and shunts (55%). Significantly larger diameters were observed in hypertensive shunts (40 mm; IQR 36.7-45 mm vs. 34 mm; IQR 32-36 mm) (p < 0.0001). However, the largest diameters were found in cono-truncal anomalies. There was no significant correlation between PA dimensions and systolic pulmonary pressure (r = -0.196), trans-pulmonary gradient (r = -0.203), pulmonary regurgitation (PR) (r = 0.071) or magnitude of shunt (r = 0.137) (p > 0.05 for all). Over follow-up, 1 sudden death (SD) occurred in one Eisenmenger patient. Complications included coronary (3), recurrent laryngeal nerve (1) and airway (1) compressions, progressive PR (1), and PA thrombosis (1). Coronary compression and SD were strongly associated (univariate analysis) with pulmonary hypertension (120 vs. 55 mm Hg; p = 0.002) but not with extreme PA dilatation (range: 40-65 mm).

CONCLUSIONS

PA dilatation in CHD is common but only a small percentage of patients have PAA. Clinical impact on outcomes is low. Complications occurred almost exclusively in patients with pulmonary hypertension whereas PA diameter alone was not associated with adverse outcomes.

Abnormal Haemodynamic Flow Patterns in Bicuspid Pulmonary Valve Disease

Abnormal flow patterns in the aortas of those with bicuspid aortic valves (BAVs) are increasingly recognized as important in the pathogenesis of aortic dilatation but pulmonary flow patterns in bicuspid pulmonary valves have not been studied. Bicuspid pulmonary valve disease is rare and a small numbers of case reports describe concomitant pulmonary artery dilation similar to the dilation of the ascending aorta, which is often seen in BAVs disease. We examined three cases of bicuspid pulmonary valve disease, 10 healthy volunteers and 10 patients with BAV disease but a tricuspid pulmonary valve. All participants underwent anatomical and functional imaging of the pulmonary valve, pulmonary artery, and right ventricle as well as advanced time-resolved 3-dimensional cardiac magnetic resonance imaging (4D flow) to assess the flow pattern in the pulmonary artery. All patients with a bicuspid pulmonary valve had pulmonary artery dilation and showed distinct helical flow abnormalities with increased rotational flow and increased flow displacement compared to a mild left-handed flow pattern in the healthy volunteers. Additionally, there was marked asymmetry seen in the systolic wall shear stress (WSS) pattern, with the highest values in the anterior wall of the pulmonary artery. In comparison, patients with a BAV but a tricuspid pulmonary valve had normal flow patterns in the pulmonary artery. These haemodynamic findings are similar to recent studies in bicuspid aortic disease, and suggest the importance of flow patterns in the pathophysiology of vessel dilation in both aortic and pulmonary bicuspid valve disease.

Significance of main pulmonary artery dilation on imaging studies

Proper and early identification of patients who harbor serious occult illness is the first step in developing a disease-management strategy. Identification of illnesses through the use of noninvasive techniques provides assurance of patient safety and is ideal. PA dilation is easily measured noninvasively and is due to a variety of conditions, including pulmonary hypertension (PH). The clinician should be able to thoroughly assess the significance of PA dilation in each individual patient. This involves knowledge of the ability of PA dilation to accurately predict PH, understand the wide differential diagnosis of causes of PA dilation, and reverse its life-threatening complications. We found that although PA dilation is suggestive of PH, data remain inconclusive regarding its ability to accurately predict PH. At this point, data are insufficient to place PA dilation into a PH risk-score equation. Here we review the causes and complications of PA dilation, define normal and abnormal PA measurements, and summarize the data linking its association to PH, while suggesting an algorithm designed to assist clinicians in patient work-up after recognizing PA dilation.

The main pulmonary artery in adults: a controlled multicenter study with assessment of echocardiographic reference values, and the frequency of dilatation and aneurysm in Marfan syndrome

BACKGROUND

Echocardiographic upper normal limits of both main pulmonary artery (MPA) diameters (MPA-d) and ratio of MPA to aortic root diameter (MPA-r) are not defined in healthy adults. Accordingly, frequency of MPA dilatation based on echocardiography remains to be assessed in adults with Marfan syndrome (MFS).

METHODS

We enrolled 123 normal adults (72 men, 52 women aged 42 ± 14 years) and 98 patients with MFS (42 men, 56 women aged 39 ± 14 years) in a retrospective cross-sectional observational controlled study in four tertiary care centers. We defined outcome measures including upper normal limits of MPA-d and MPA-r as 95 quantile of normal persons, MPA dilatation as diameters > upper normal limits, MPA aneurysm as diameters >4 cm, and indication for surgery as MPA diameters >6 cm.

RESULTS

MPA diameters revealed normal distribution without correlation to age, sex, body weight, body height, body mass index and body surface area. The upper normal limit was 2.6 cm (95% confidence interval (CI) =2.44-2.76 cm) for MPA-d, and 1.05 (95% CI = .86-1.24) for MPA-r. MPA dilatation presented in 6 normal persons (4.9%) and in 68 MFS patients (69.4%; P < .001), MPA aneurysm presented only in MFS (15 patients; 15.3%; P < .001), and no patient required surgery. Mean MPA-r were increased in MFS (P < .001), but ratios >1.05 were equally frequent in 7 normal persons (5%) and in 8 MFS patients (10.5%; P = .161). MPA-r related to aortic root diameters (P = .042), reduced left ventricular ejection fraction (P = .006), and increased pulmonary artery systolic pressures (P = .040). No clinical manifestations of MFS and no FBN1 mutation characteristics related to MPA diameters.

CONCLUSIONS

We established 2.6 cm for MPA-d and 1.05 for MPA-r as upper normal limits. MFS exhibits a high prevalence of MPA dilatation and aneurysm. However, patients may require MPA surgery only in scarce circumstances, most likely because formation of marked MPA aneurysm may require LV dysfunction and increased PASP.

Fused aortic valve without an elliptical-shaped systolic orifice in patients with severe aortic stenosis: cardiac computed tomography is useful for differentiation between bicuspid aortic valve with raphe and tricuspid aortic valve with commissural fusion

OBJECTIVE

The objective is to determine cardiac computed tomography (CCT) features capable of differentiating between bicuspid aortic valve (BAV) and tricuspid aortic valve (TAV) in severe aortic stenosis (AS) patients with fused cusp and without elliptical-shaped systolic orifices.

METHODS

We retrospectively enrolled 53 patients who had severe AS with fused cusps and without an elliptical-shaped systolic orifice on CCT and who had undergone surgery. CCT features were analyzed using: 1) aortic valve findings including cusp size, cusp area, opening shape, midline calcification, fusion length, calcium volume score, and calcium grade; 2) diameters of ascending and descending aorta, and main pulmonary artery; and 3) rheumatic mitral valve findings. The variables were evaluated using univariate and multivariate logistic regression analyses.

RESULTS

At surgery, 19 patients had BAV and 34 had TAV. CCT features including uneven cusp size, uneven cusp area, round-shaped systolic orifice, longer cusp fusion, and dilatation of ascending aorta were significantly associated with BAV (P < 0.05). In particular, fusion length (OR, 1.76; P = 0.001), uneven cusp area (OR, 10.46; P = 0.012), and midline calcification (OR, 0.08; P = 0.013) were strongly associated with BAV.

CONCLUSION

CCT provides diagnostic clues that helps differentiate between BAV with raphe and TAV with commissural fusion in patients with severe AS.

KEY POINTS

• Accurate morphologic assessment of the aortic valve is important for treatment planning. • It is difficult to differentiate BAV from TAV with a fused cusp. • CCT provides diagnostic clues for the differentiation of BAV and TAV.

Estimated in vivo postnatal surface growth patterns of the ovine main pulmonary artery and ascending aorta

Delineating the normal postnatal development of the pulmonary artery (PA) and ascending aorta (AA) can inform our understanding of congenital abnormalities, as well as pulmonary and systolic hypertension. We thus conducted the following study to delineate the PA and AA postnatal growth deformation characteristics in an ovine model. MR images were obtained from endoluminal surfaces of 11 animals whose ages ranged from 1.5 months/15.3 kg mass (very young) to 12 months/56.6 kg mass (adult). A bicubic Hermite finite element surface representation was developed for the each artery from each animal. Under the assumption that the relative locations of surface points were retained during growth, the individual animal surface fits were subsequently used to develop a method to estimate the time-evolving local effective surface growth (relative to the youngest measured animal) in the end-diastolic state. Results indicated that the spatial and temporal surface growth deformation patterns of both arteries, especially in the circumferential direction, were heterogeneous, leading to an increase in taper and increase in cross-sectional ellipticity of the PA. The longitudinal PA growth stretch of a large segment on the posterior wall reached 2.57 ± 0.078 (mean ± SD) at the adult stage. In contrast, the longitudinal growth of the AA was smaller and more uniform (1.80 ± 0.047). Interestingly, a region of the medial wall of both arteries where both arteries are in contact showed smaller circumferential growth stretches-specifically 1.12 ± 0.012 in the PA and 1.43 ± 0.071 in the AA at the adult stage. Overall, our results indicated that contact between the PA and AA resulted in increasing spatial heterogeneity in postnatal growth, with the PA demonstrating the greatest changes. Parametric studies using simplified geometric models of curved arteries during growth suggest that heterogeneous effective surface growth deformations must occur to account for the changes in measured arterial shapes during the postnatal growth period. This result suggests that these first results are a reasonable first-approximation to the actual effective growth patterns. Moreover, this study clearly underscores how functional growth of the PA and AA during postnatal maturation involves complex, local adaptations in tissue formation. Moreover, the present results will help to lay the basis for functional replacement by defining critical geometric metrics.

Nonstenotic bicuspid aortic valve is associated with elevated plasma asymmetric dimethylarginine

BACKGROUND

Recently, it has been reported that nonstenotic bicuspid aortic valve (BAV) with dilated proximal aorta is linked with increased matrix metalloproteinase-2 (MMP-2) and endothelial dysfunction.

OBJECTIVE

We wondered whether asymmetric dimethylarginine (ADMA), a nitric oxide synthase inhibitor, might be altered and associated with MMP-2 in BAV patients. We assessed the relation between ADMA levels and aortic diameters and hypothesized that elevated ADMA might be an independent predictor of progressive aortic dilatation in BAV patients.

METHODS

We studied 20 patients with nonstenotic BAV (17 men and 3 women, median age 27, range 24-33 years). Twenty age-matched patients with tricuspid aortic valves served as controls. Plasma levels of ADMA, symmetric dimethylarginine (SDMA), L-arginine, serum MMP-2, MMP-9, and plasma total homocysteine (tHcy), together with parameters of aortic elasticity, were measured.

RESULTS

ADMA and MMP-2 levels were higher in the BAV group compared with controls (medians, 0.55 vs. 0.43 μmol/l, P < 0.001 and 1.25 vs. 1.00 μmol/l, P < 0.001, respectively). The BAV patients also had higher SDMA and tHcy levels than controls (0.39 vs. 0.35 μmol/l, P < 0.001 and 11.5 vs. 9.7 μmol/l, P = 0.006). ADMA levels in BAV patients correlated with aortic annulus (r = 0.4, P = 0.043), peak aortic velocity (r = 0.6, P = 0.001), aortic distensibility (r = 0.6, P = 0.004), aortic stiffness index (r = 0.7, P < 0.001), and aortic strain (r = 0.7, P < 0.001) as well as with MMP-2 (r = 0.6, P = 0.002) and tHcy (r = 0.4, P = 0.042).

CONCLUSIONS

This study is the first to show that circulating ADMA together with MMP-2 is a marker of proximal ascending aortic dilatation and impaired aortic elastic properties in nonstenotic BAV patients. It might be speculated that plasma ADMA could be helpful in identifying BAV patients at a higher risk of aortic aneurysm.

Screening of families of patients with left-sided cardiovascular anomalies

BACKGROUND

There is increasing evidence of clustering of certain cardiac anomalies in some families. The frequency and echocardiographic features of such anomalies among the relatives of patients with bicuspid aortic valve (BAV) or other left-sided cardiovascular anomalies (LSCA) were evaluated.

METHODS

The patients with BAV or any other LSCA and their relatives were enrolled in the study. They underwent an echocardiographic examination. The probands were assessed in three groups: BAV, BAV + coarctation of aorta (CoA), and other LSCA. Their relatives were also grouped and evaluated accordingly. The echocardiographic measurements were standardized by Z-scores.

RESULTS

Eighty-six probands and 261 relatives were evaluated. The numbers of the patients in the BAV, BAV + CoA, and other LSCA group were 52, 14, and 20, respectively. Any LSCA was determined in 17 (6.5%) of the relatives. Thirteen (5%) had aortic dilatation and the remainder (1.5%) had BAV. Accordingly, BAV incidence among relatives of patients with BAV was found to be 1.9%. A second individual with an LSCA was observed in 12.8% of 86 families investigated. The frequencies of aortic stenosis, aortic regurgitation, aortic stenosis + aortic regurgitation, and aortic dilatation in the patients with BAV were found to be 37.9%, 53%, 25.8% and 48.5%, respectively. In contrast to previous reports, no enlargement was observed in the pulmonary arteries of BAV patients.

CONCLUSIONS

BAV and other LSCA are of clinical significance. Because the clustering of LSCA in some families is observed, we recommend echocardiographic screening of those relatives. If this is not possible, at least it should be achieved for BAV patients.

Regional structural and biomechanical alterations of the ovine main pulmonary artery during postnatal growth

The engineering foundation for novel approaches for the repair of congenital defects that involve the main pulmonary artery (PA) must rest on an understanding of changes in the structure-function relationship that occur during postnatal maturation. In the present study, we quantified the postnatal growth patterns in structural and biomechanical behavior in the ovine PA in the juvenile and adult stages. The biaxial mechanical properties and collagen and elastin fiber architecture were studied in four regions of the PA wall, with the collagen recruitment of the medial region analyzed using a custom biaxial mechanical-multiphoton microscopy system. Circumferential residual strain was also quantified at the sinotubular junction and bifurcation locations, which delimit the PA. The PA wall demonstrated significant mechanical anisotropy, except in the posterior region where it was nearly isotropic. Overall, we observed only moderate changes in regional mechanical properties with growth. We did observe that the medial and lateral locations experience a moderate increase in anisotropy. There was an average of about 24% circumferential residual stain present at the luminal surface in the juvenile stage that decreased to 16% in the adult stage with a significant decrease at the bifurcation, implying that the PA wall remodels toward the bifurcation with growth. There were no measurable changes in collagen and elastin content of the tunica media with growth. On average, the collagen fiber recruited more rapidly with strain in the adult compared to the juvenile. Interestingly, the PA thickness remained constant with growth. When this fact is combined with the observed stable overall mechanical behavior and increase in vessel diameter with growth, a simple Laplace Law wall stress estimate suggests an increase in effective PA wall stress with postnatal maturation. This observation is contrary to the accepted theory of maintenance of homeostatic stress levels in the regulation of vascular function and suggests alternative mechanisms regulate postnatal somatic growth. Understanding the underlying mechanisms, incorporating important structural features during growth, will help to improve our understanding of congenital defects of the PA and lay the basis for functional duplication in their repair and replacement.

[Giant aneurysm of the pulmonary artery: a case report]

Pulmonary artery aneurysm is a rare condition accounting for less than 1% of all intra thoracic aneurysms. This paper reports a case of giant aneurysm of the trunk and branches of the pulmonary artery, which was discovered incidentally on a computed tomography angiogram in a 48-year-old man with a past history of pulmonary tuberculosis. Besides the aneurysm there was dilation of the pulmonary annulus with massive pulmonary regurgitation, a tight mitral stenosis and sequelae of pleural and pulmonary tuberculosis. The patient is being followed-up with medical treatment and has been stable clinically for the last ten months.

Quantitative assessment of asymmetric aortic dilation with valve-related aortic disease

RATIONALE AND OBJECTIVES

Previous work suggests that ascending aortic (AsAo) dilation can be asymmetric and is potentially related to valve-related blood flow abnormalities. The aim of this study was to investigate the relationship between the aortic valve and AsAo dilation using a quantitative, three-dimensional assessment of aortic shapes.

MATERIALS AND METHODS

Computed tomographic and magnetic resonance images of the thorax were retrospectively reviewed. Four groups with aortic dilation were studied: those with tricuspid aortic valves (TAVs) with and without stenosis and those with bicuspid aortic valves (BAVs) with and without stenosis. Controls had either TAVs or BAVs but no aortic stenosis or dilation. In additional to standard orthogonal diameters, a unique measurement of AsAo asymmetry was used: the ratio of the greater to lesser curvatures measured using three-dimensional reformats in a "candy-cane" orientation.

RESULTS

A total of 105 patients were identified. Ratios of greater to lesser curvature in patients with aortic dilation and nonstenotic TAVs were not significantly different from those in controls (1.69 vs 1.55, P > .20), but the asymmetry reflected by this ratio was markedly increased in patients with aortic dilation and stenotic TAVs (1.94, P < .001). Patients with aortic dilation and BAVs had significantly elevated ratios regardless of the status of the aortic valve (1.96 for nonstenotic and 2.05 for stenotic vs 1.53 for controls, P < .001).

CONCLUSIONS

Asymmetric AsAo dilation with relative bulging of the greater curvature is linked to aortic stenosis, but it is also seen with nonstenotic BAVs. This suggests that the hemodynamic forces that contribute to aortic dilation are not fully revealed by conventional assessment of the aortic valve.