The Association between Morphological and Functional Characteristics of the Bicuspid Aortic Valve and Bicuspid Aortopathy

Abstract

Objective: To identify the association between morphological and functional characteristics of the bicuspid aortic valve (BAV) and bicuspid aortopathy and to identify the determinants of aortic dilatation using transthoracic echocardiography (TTE) and cardiac computed tomography (CCT).

Materials and methods: This study included 312 subjects (mean [SD] age, 52.7 [14.3] years; 227 males [72.8%]) who underwent TTE and CCT. The BAVs were classified by anterior-posterior (BAV-AP) or right-left (BAV-RL) orientation of the cusps and divided according to the presence (raphe+) or absence of a raphe (raphe-) based on the CCT and intraoperative findings. The dimensions of the sinus of Valsalva and the proximal ascending aorta were measured by CCT. We assessed the determinants of aortic root and proximal ascending aortic dilatation (size index > 2.1 cm/m²) by Univariable and multivariable logistic regression analyses.

Results: Of the 312 patients, BAV-AP was present in 188 patients (60.3%), and 185 patients (59.3%) were raphe+. Moderate-to-severe aortic stenosis (AS) was the most common hemodynamic abnormality (54.8%). The most common type of aortopathy was the combined dilated root and mid-ascending aortic phenotype (62.5%). On multivariable analysis, age and AS severity were significantly associated with aortic root dilatation (p < 0.05), and age, sex, and AS severity were significantly associated with ascending aortic dilatation (p < 005). However, the orientation of the cusps, presence of a raphe, and severity of aortic regurgitation were not associated with aortic root and ascending aortic dilatation.

Conclusion: BAV morphological characteristics were not determinants of aortic dilatation. Age, sex, and AS severity were predictors of bicuspid aortopathy. Therefore, age, sex, and AS severity, rather than valve morphology, need to be considered when planning treatment for BAV patients.

Keywords: Ascending aorta; Bicuspid aortic valve; Multidetector computed tomography; Transthoracic echocardiography.

Fig. 1. BAV classification.

BAV-AP is defined as an AP orientation of the cusps (A) or a raphe (B, arrow). BAV-RL is defined as a RL orientation of the cusps (C) or a raphe (D, arrow). BAV is divided according to the presence (B, D) or absence (A, C) of a raphe. AP = anterior-posterior, BAV = bicuspid aortic valve, RL = right-left

Fig. 2. Example of measurement of the aortic dimensions at different locations.

Oblique sagittal reformatted CT image shows sinus of Valsalva and tubular portion of ascending aorta at early-to-mid-systole (A). The maximum dimension of the tubular portion of ascending aorta was measured in a double oblique transverse view (B) obtained perpendicular to the aortic lumen (C). The maximum dimension of the sinus of Valsalva was measured sinus to commissure in BAV with raphe (D) and sinus to sinus in BAV without raphe (E) in a double oblique transverse view. The ascending aorta was assigned to one of four main anatomical phenotypes according to the vessel segment exclusively or predominantly involved in the dilatation. BAV = bicuspid aortic valve

Fig. 3. BAV with anterior-posterior orientation of the free edge of the cusps with a raphe in a 47-year-old male.

He had normal valvular function. A. Double oblique CT reconstruction parallel to the aortic valve during systole demonstrates BAV with a fusion of the right and left coronary cusps. B. Double oblique coronal CT reconstruction through the left ventricular outflow tract during systole shows dimensions of the sinus of Valsalva (41.7 mm, 1.91 cm/m² of body surface area) and the tubular portion (40.2 mm, 1.84 cm/m² of body surface area). A normal aortic phenotype was considered because the two aortic dimensions were less than 2.1 cm/m² of the body surface area. BAV = bicuspid aortic valve

Fig. 4. BAV with right-left orientation of the free edge of the cusps without raphe in a 61-year-old female.

A. Double oblique CT reconstruction parallel to the aortic valve during systole demonstrates thickened, calcified cusps of the BAV with a fusion of the right and noncoronary cusps. B. Double oblique coronal CT reconstruction through the left ventricular outflow tract during systole shows dimensions of the sinus of Valsalva (43.1 mm, 2.51 cm/m² of body surface area) and the tubular portion (51.4 mm, 2.99 cm/m² of body surface area). A combined dilated root and mid-ascending aortic phenotype (type 3) was considered because the two aortic dimensions exceeded 2.1 cm/m² of body surface area. C. Continuous-wave Doppler recording of the aortic stenosis jet from an apical approach shows a maximum velocity of 4.0 m/sec. The continuity equation of the aortic valve area was 1.41 cm², corresponding to moderate aortic stenosis. BAV = bicuspid aortic valve