Features and predictors of ascending aortic dilatation in association with a congenital bicuspid aortic valve

Bicuspid aortic valve disease

Bicuspid aortic valve (BAV) disease is the most common congenital cardiac defect. While the BAV can be found in isolation, it is often associated with other congenital cardiac lesions. The most frequent associated finding is dilation of the proximal ascending aorta secondary to abnormalities of the aortic media. Changes in the aortic media are present independent of whether the valve is functionally normal, stenotic, or incompetent. Although symptoms often manifest in adulthood, there is a wide spectrum of presentations ranging from severe disease detected in utero to asymptomatic disease in old age. Complications can include aortic valve stenosis or incompetence, endocarditis, aortic aneurysm formation, and aortic dissection. Despite the potential complications, 2 large contemporary series have demonstrated that life expectancy in adults with BAV disease is not shortened when compared with the general population. Because BAV is a disease of both the valve and the aorta, surgical decision making is more complicated, and many undergoing aortic valve replacement will also need aortic root surgery. With or without surgery, patients with BAV require continued surveillance. Recent studies have improved our understanding of the genetics, the pathobiology, and the clinical course of the disease, but questions are still unanswered. In the future, medical treatment strategies and timing of interventions will likely be refined. This review summarizes our current understanding of the pathology, genetics, and clinical aspects of BAV disease with a focus on BAV disease in adulthood.

Standardizing the method of measuring by echocardiogram the diameter of the ascending aorta in patients with a bicuspid aortic valve

Serial echocardiographic follow-up of patients with a bicuspid aortic valve (BAV), in addition to providing assessment of valve dysfunction, can help identify those at risk of aortic complications. However, currently there is no standardized echocardiographic method for measuring the ascending aorta. We examined the echocardiograms of 45 patients with a BAV and 45 matched controls to understand the effects of the measurement location (1, 2, and 3 cm above the sinotubular junction) and the point in the cardiac cycle (end-diastole, mid-systole, and end-systole) at which the ascending aortic measurements are made. A greater length of aorta could be measured in end-systole than in end-diastole, presumably because of aortic recoil. Using the control data for comparison, we found that more dilated ascending aortas were detected by measuring 3 cm above the sinotubular junction in the patients with a BAV (56%) than at 1 cm (42%). The increases in size between 1 and 2 cm were greater than those between 2 and 3 cm. In conclusion, we propose that all transthoracic echocardiograms should include the proximal aorta at least 2 cm and preferably 3 cm above the sinotubular junction and suggest that for standardization and optimal visualization the measurements be done at end-systole in all patients.

A measured approach to managing the aortic root in patients with bicuspid aortic valve disease

Bicuspid (or bicommissural) aortic valve (BAV) is the most common cardiovascular malformation in humans, with a prevalence of 1% to 2% in the general population and a 2:1 male:female ratio. BAV is frequently associated with other cardiovascular malformations, including aortic root dilatation, which affects about 40% of individuals with BAVs and is thought to be associated with increased risk of dissection and/or rupture. Currently, no agreement exists about the optimal management of these patients. We review the pathophysiology and possible determinants of aortic disease associated with BAV, the natural history of aortic wall size progression, and suggest management strategies to prevent acute aortic events.

Valve replacement options in the setting of an ascending aortic aneurysm

Aortic valve disease is frequently associated with proximal aortic aneurysmal disease. While, there are clear indications for aortic valve replacement, the ideal type of valve prosthesis, mechanical versus biologic remains controversial. This controversy becomes even more complex when the proximal aorta requires replacement as root replacement is more challenging and reoperative surgery following root replacement is even more so. In addition, not all proximal aortic aneurysms behave the same way; Marfan's aneurysms behave more aggressively than non-Marfan's aneurysms. The variance in aneurysm behavior mandates a clear understanding of the biology and consequent natural history of each patient's aortic aneurysm. In this review, we discuss valve replacement options for patients requiring aortic valve replacement and concomitant proximal aortic replacement.

Severe aortic stenosis and its association with hypertension: Analysis of clinical and echocardiographic parameters

BACKGROUND/AIMS

Aortic stenosis (AS) and hypertension are associated with cardiac hypertrophy and aortic dilatation. The effect of their coincidence on the ascending aortic dimensions has not yet been evaluated, and therefore was the aim of our study.

METHODS

We performed cross-sectional analysis of history, clinical, angiographic and echocardiographic data of consecutive patients evaluated before surgery for non-rheumatic AS.

RESULTS

The study sample included 225 patients (age 68+/-9 years, 60% males), with mean transaortic gradient of 55+/-17 mmHg. Hypertension was present in 153 (68%) patients. The hypertensives had more severe dyspnea (NYHA class 2.2+/-0.9 vs 1.9+/-0.9, p = 0.05) and higher prevalence of coronary artery disease (57% vs 33%, p = 0.001), but did not differ from the normotensives in the ascending aortic dimensions, the left ventricular mass, ejection fraction and remodeling patterns. Wider ascending aortic dimensions were independently associated with bicuspid aortic valve (p<0.001), and with maximal gradient in those with tricuspid aortic valve. Vasodilators were used in 84 (54%) hypertensives.

CONCLUSION

We found hypertension in 68% of patients with severe AS. Bicuspid aortic valve and stenosis severity were independent predictors of ascending aortic dimensions, but not the history of hypertension and blood pressure.

Is aortic wall degeneration related to bicuspid aortic valve anatomy in patients with valvular disease?

OBJECTIVE

Patients with bicuspid aortic valve are at increased risk for aortic complications.

METHODS

A total of 115 consecutive patients with bicuspid aortic valve disease underwent surgery of the ascending aorta. We classified the cusp configuration by 3 types: fusion of left coronary and right coronary cusps (type A), fusion of right coronary and noncoronary cusps (type B), and fusion of left coronary and noncoronary cusps (type C). Histopathologic changes in the ascending aortic wall were graded (aortic wall score).

RESULTS

We observed type A fusion in 85 patients (73.9%), type B fusion in 28 patients (24.3%), and type C fusion in 2 patients (1.8%). Patients with type A fusion were younger at operation than patients with type B fusion (51.3 +/- 15.5 years vs 58.7 +/- 7.6 years, respectively; P = .034). The mean ascending aorta diameter was 48.9 +/- 5.0 mm and 48.7 +/- 5.7 mm in type A and type B fusion groups, respectively (P = .34). The mean aortic root diameter was significantly larger in type A fusion (4.9 +/- 6.7 mm vs 32.7 +/- 2.8 mm; P < .0001). The aortic wall score was significantly higher in type A fusion than in type B fusion (P = .02). The prevalence of aortic wall histopathologic changes was significantly higher in type A fusion. Moreover, there were no statistically significant differences between type A and type B fusion in terms of prevalence of bicuspid aortic valve stenosis, regurgitation, or mixed disease.

CONCLUSION

In diseased bicuspid aortic valves, there was a statistically significant association between type A valve anatomy and a more severe degree of wall degeneration in the ascending aorta and dilatation of the aortic root at younger age compared with type B valve anatomy.

Unicuspid aortic valve mimicking quadricuspid valve

Unicuspid aortic valve is a rare congenital cardiac abnormality, leading to aortic stenosis or regurgitation. We report the case of a 55-year-old man with severe aortic regurgitation caused by a unicuspid valve mimicking quadricuspid valve.

Progressive dilation of the ascending aorta in children with isolated bicuspid aortic valve

Although patients with bicuspid aortic valves (BAVs) are predisposed to ascending aortic (AA) dilation, stenosis, and dissection, the development of aortic disease in children with BAVs is poorly described. The purposes of this study were to determine the rate of change of AA diameter in children with BAVs and to identify risk factors for the development of aortic dilation. The echocardiograms of 276 children aged<19 years (mean 8.5+/-5.3) with isolated BAVs were reviewed. Aortic measurements were normalized to z scores on the basis of body surface area. In a subset of 112 patients with serial examinations, aortic growth rates were calculated and risk factors for more rapid aortic growth determined. At presentation, 33 patients (12%) demonstrated marked AA dilation (z>4), and 70 (25%) were moderately abnormal (z between 2 and 4). The mean+/-SD AA diameter increased more than expected, at a rate of 0.18+/-0.30 z score per year (p<0.0001). In 61 patients with normal AA diameters on initial study, 22 (36%) had abnormal diameters, with z scores>2, at follow-up. Univariate analysis demonstrated right-noncoronary commissural fusion (p<0.02) and aortic valve gradient on initial examination (p<0.02) as significant predictors of AA growth. In multivariate analysis, however, the significance of gradient and valve morphology was diminished (p = 0.06 for both). In conclusion, the progression of AA diameter in patients with normal z scores on initial examination suggests that serial echocardiograms are required to screen for the development of significant aortic dilation.

Aortic Stenosis Severity is not a Risk Factor for Poststenotic Dilatation of the Ascending Aorta

BACKGROUND

Dilatation of the ascending aorta in aortic stenosis may be partly explained by intrinsic wall structure changes, but the relative contribution of altered hemodynamics is unclear. The aim of this study was to assess the association between ascending aortic dimensions and valve stenosis severity.

METHODS AND RESULTS

An analysis of echocardiographic examinations was conducted in 296 patients with aortic stenosis (179 males, mean age 71 years), 57 with bicuspid and 239 with tricuspid aortic valve, mean transaortic gradient 43+/-20 mmHg, and not more than moderate aortic regurgitation. Aortic dimensions at the level of annulus, sinuses of Valsalva, sinotubular junction and proximal ascending aorta were measured. Only height (p<0.001), degree of aortic regurgitation (p<0.01) and presence of bicuspid aortic valve (p<0.001) were independent predictors of ascending aortic dimensions.

CONCLUSIONS

An independent association between aortic pressure gradients and proximal ascending aortic dimensions was not observed in patients with bicuspid or tricuspid aortic valve stenosis. Therefore, the poststenotic dilatation of the ascending aorta is not explained by aortic stenosis severity itself. Possible nonhemodynamic causes deserve detailed study at the time of diagnosis.

Morphology and function of the bicuspid aortic valve with and without coarctation of the aorta in the young

This study sought to determine the morphology and function of bicuspid aortic valves (BAVs) with and without coarctation of the aorta (CoA) in a young population. The transthoracic echocardiograms of 117 patients with BAVs and 62 patients with CoA were retrospectively reviewed and compared with normal transthoracic echocardiographic results. In each patient, the area subtended by the aortic cusps and valve and the diameters of the aortic root at different levels were measured, and additionally in each BAV, the type of cusp fusion and the presence and degree of aortic stenosis and/or regurgitation were evaluated. The median age of patients with BAVs was 4 years (range 0 days to 34 years), and the median age of patients with CoA was 1.9 years (range 0 days to 16.5 years). BAVs with right and left coronary cusp fusion were significantly associated with CoA (p <0.0001) and cardiac anomalies (p <0.0001), whereas BAVs with noncoronary and right coronary cusp fusion were affected by valvar dysfunction (p <0.001). Compared with normal tricuspid aortic valves, BAVs had aortic root dilation, even in patients with no hemodynamic disturbance, particularly at the level of the ascending aorta (p <0.0001); the difference was still significant comparing BAVs and CoA with tricuspid aortic valves and CoA (p <0.0001). In conclusion, different morphologies of BAVs are associated with different cardiac abnormalities, valvar function, and aortic root dilation. Although detectable early in life, valvar dysfunction and aortic root dilation progress with age.

Repair of Bicuspid Aortic Valves in Patients With Aortic Regurgitation

Background— Bicuspid aortic valve regurgitation can be caused by a defect in the valve itself or by dysfunction of one or more components of the aortic root complex. A successful repair thus requires correction of all aspects of the problem simultaneously. We review our experience addressing both the valve and the aortic root when correcting bicuspid valve regurgitation.

Methods and Results— Between 1996 and 2004, we treated 68 patients for aortic regurgitation. Thirty patients had isolated aortic regurgitation, and 38 had an associated ascending aortic aneurysm. All patients were treated using a standardized and integrated surgical technique, which included resection of the median raphe or leaflet plication, subcommissural annuloplasty, reinforcement of the leaflet free edge, and sinotubular junction plication. In the 38 patients with proximal aortic dilatation, reimplantation or remodeling of the aortic root was performed. Immediate postoperative echocardiography showed grade ≤1 aortic regurgitation in all patients. Three patients nonetheless needed an early re-operation because of recurrent regurgitation. No hospital mortality was observed. At a mean follow-up of 34 months after surgery, all patients were in New York Heart Association (NYHA) class 1 or 2. Two patients needed a re-operation (23 and 92 months, respectively). Echocardiographic follow-up showed no progression of the regurgitation in 58 surviving patients. Four patients progressed to grade 2 regurgitation.

Conclusion— Our data indicate that regurgitant bicuspid aortic valves, whether alone or in association with a proximal aortic dilatation, can be repaired successfully provided that both the valve and the aortic root problems are treated simultaneously.

Aortic dilatation in patients with bicuspid aortic valve

The association of a bicuspid aortic valve (BAV) with abnormalities of the proximal thoracic aorta, including dilatation, aneurysm and dissection, has been previously described, leading to the hypothesis of a common underlying developmental defect involving the aortic valve and the aortic wall. Consequently, any patient with BAV should receive a careful assessment not only of the valve function, but also of the aortic root and the ascending aorta. Dilatation of the proximal thoracic aorta is a common finding in patients with BAV and is believed to be related to aortic rupture and dissection. Because progressive dilatation can occur, careful long-term surveillance of the aortic dimensions is required. Prophylactic surgical repair of the dilated aorta should be recommended more aggressively for patients with BAV than for those with a tricuspid aortic valve. However, the optimal timing of aortic surgery in BAV patients remains uncertain because of the limited data available on the natural history of asymptomatic aortic dilatation.

Different patterns of extracellular matrix protein expression in the convexity and the concavity of the dilated aorta with bicuspid aortic valve: preliminary results

OBJECTIVE

This study aimed to assess extracellular matrix protein expression patterns at the convexity (right anterolateral wall) and the concavity of the dilated ascending aorta in patients with bicuspid aortic valve disease.

METHODS

Aortic wall specimens were retrieved from the convexity and the concavity in 27 bicuspid aortic valve patients (12 with stenosis and 15 with regurgitation) and 6 heart donors (controls). Morphometry, immunohistochemistry, Western blot, and polymerase chain reaction were performed, focusing on matrix proteins involved in vascular remodeling.

RESULTS

Type I and III collagens were significantly decreased in bicuspid-associated dilated aortas versus controls (P < .001), particularly at the convexity (P < .05 vs concavity). Expression of messenger RNA for collagens was lower than normal only in the regurgitant subgroup. At immunohistochemistry, proteins whose overproduction has been demonstrated in response to abnormal wall stress, such as tenascin and fibronectin, were more expressed in the convexity than in the concavity, especially in the stenosis subgroup. Tenascin, which is produced by smooth muscle cells in the synthetic phenotype, was nearly undetectable in controls. Fewer smooth muscle cells (stenosis, P = .017; regurgitation, P = .008) and more severe elastic fiber fragmentation (P = .029 and P < .001) were observed in the convexity versus the concavity.

CONCLUSIONS

In bicuspid-associated aortic dilations, an asymmetric pattern of matrix protein expression was found that was consistent with the asymmetry in wall-stress distribution reported previously. Differences exist between patients with stenosis and those with regurgitation in terms of protein expression and content in the aortic wall. Further studies could clarify the relations between these findings and the pathogenesis of aortic dilatation in bicuspid aortic valve patients.

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

BACKGROUND

The long-term outcome of repaired aortic coarctation may be complicated by dilatation of the ascending aorta notably in patients with bicuspid aortic valve. Magnetic resonance imaging was used to compare the size of the ascending aorta in patients with bicuspid or tricuspid aortic valve.

METHODS

In 50 patients with a repair of aortic coarctation, the size of the ascending aorta was measured in a bicuspid aortic valve group (n=11) and a tricuspid aortic valve group (n=39). The aortic diameter was measured at the level of the sinus of Valsalva and at the widest part of the ascending aorta using magnetic resonance imaging.

RESULTS

The mean age of patients at surgical repair was respectively 2.2+/-3.3 years for the bicuspid aortic valve group and 2.5+/-3.5 years for the tricuspid aortic valve group (p=NS) and the mean age at the time of the magnetic resonance imaging was 10.2+/-4.7 years and 9.3+/-5.9 years (p=NS) respectively. A significant difference in the aortic diameter was found between the bicuspid aortic valve group and the tricuspid aortic group both at the level of sinus of Valsalva (34.8+/-8.2 mm, 19.5+/-4.4 mm, respectively, p<0.01) and at the level of the ascending aorta (36.8+/-7.2 mm, 16.9+/-3.4 mm, respectively, p<0.01).

CONCLUSIONS

The occurrence of ascending aortic dilatation is significantly associated with the presence of a bicuspid aortic valve. This requires long-term follow-up, which can be effectively performed by magnetic resonance imaging.

Aortic dimensions in patients with bicuspid aortic valve without significant valve dysfunction

The dimensions of the entire aorta at different anatomic levels were measured by transthoracic 2-dimensional echocardiography in 162 consecutive patients with isolated bicuspid aortic valves (BAVs) without significant aortic valve dysfunction. Aortic dilation involved the aortic root and the ascending aorta but was not present in the descending and abdominal aorta. A significant increase in the dimensions of the aortic arch was found in patients with BAVs aged >40 years. Ascending aortic diameter and the extension of aortic dilation were significantly correlated with age, but no correlation was found between aortic dimensions and aortic valve morphology.

Aortic Valve Repair Using a Differentiated Surgical Strategy

BACKGROUND

Reconstruction of the aortic valve for aortic regurgitation (AR) remains challenging, in part because of not only cusp or root pathology but also a combination of both can be responsible for this valve dysfunction. We have systematically tailored the repair to the individual pathology of cusps and root.

METHODS

Between October 1995 and August 2003, aortic valve repair was performed in 282 of 493 patients undergoing surgery for AR and concomitant disease. Root dilatation was corrected by subcommissural plication (n=59), supracommissural aortic replacement (n=27), root remodeling (n=175), or valve reimplantation within a graft (n=24). Cusp prolapse was corrected by plication of the free margin (n=157) or triangular resection (n =36), cusp defects were closed with a pericardial patch (n=16). Additional procedures were arch replacement (n=114), coronary artery bypass graft (n=60) or mitral repair (n=24). All patients were followed-up (follow-up 99.6% complete), and cumulative follow-up was 8425 patient-months (mean, 33+/-27 months).Results- Eleven patients died in hospital (3.9%). Nine patients underwent reoperation for recurrent AR (3.3%). Actuarial freedom from AR grade > or =II at 5 years was 81% for isolated valve repair, 84% for isolated root replacement, and 94% for combination of both; actuarial freedom from reoperation at 5 years was 93%, 95%, and 98%, respectively. No thromboembolic events occurred, and there was 1 episode of endocarditis 4.5 years postoperatively.

CONCLUSIONS

Aortic valve repair is feasible even for complex mechanisms of AR with a systematic and individually tailored approach. Operative mortality is low and mid-term durability is encouraging. The incidence of valve-related morbidity is low compared with valve replacement.

Effect of electrical stimulus parameters on the development and propagation of action potentials in short excitable fibres

Intracellular action potentials (IAPs) produced by short fibres in response to their electrical stimulation were analysed. IAPs were calculated on the basis of the Hodgkin-Huxley (1952) model by the method described by Joyner et al. (1978). Principal differences were found in processes of activation of short (semilength L less than 5 lambda) and long fibres under near-threshold stimulation. The shorter the fibre, the lower was the threshold value (Ithr). Dependence of the latency on the stimulus strength (Ist) was substantially non-linear and was affected by the fibre length. Both fibre length and stimulus strength influenced the IAP amplitude, the instantaneous propagation velocity (IPV) and the site of the first origin of the IAP (and, consequently, excitability of the short fibre membrane). With L less than or equal to 2 lambda and Ithr less than or equal to Ist less than or equal to 1.1Ithr, IPV could reach either very high values (so that all the fibre membrane fired practically simultaneously) or even negative values. The latter corresponded to the first origin of the propagated IAP, not at the site of stimulation but at the fibre termination or at a midpoint. The characters of all the above dependencies were unchanged irrespective of the manner of approaching threshold (variation of stimulus duration or its strength). Reasons for differences in processes of activation of short and long fibres are discussed in terms of electrical load and latency. Applications of the results to explain an increased jitter, velocity recovery function and velocity-diameter relationship are also discussed.