Aortic distensibility in alkaptonuria

Alkaptonuria (AKU) is a rare inherited disorder of tyrosine metabolism resulting in an accumulation of homogentisic acid oxidation products in the joints and cardiovascular system. Aortic distensibility may be a non-invasive indicator of cardiovascular complications. Descending thoracic aortic distensibility in alkaptonuria has not been studied.

Patients diagnosed with alkaptonuria underwent Magnetic Resonance Imaging (MRI) and gated non-contrast and contrast-enhanced cardiovascular computed tomography. Using MRI cine images, aortic distensibility of the descending thoracic aorta was determined.

Seventy-six patients with alkaptonuria were imaged. When compared to literature normal values, aortic distensibility in AKU was impaired (5.2 vs 6.2 × 10^-3, p < .001). Aortic distensibility was inversely related to age (r = -0.6, p = .0001). Hypertensive patients with alkaptonuria had impaired distensibility compared to normotensive patients with alkaptonuria (4.6 vs 5.6 × 10^-3, p = .03), and hyperlipidemic patients with alkaptonuria had impaired distensibility compared to non-hyperlipidemic patients with alkaptonuria (4.1 vs 6.0 × 10^-3, p = .001). Male hypertensive patients with alkaptonuria had greater distensibility than their female counterparts (5.3 vs 2.9 × 10^-3, p = .02). Similarly, male hyperlipidemic patients with alkaptonuria had greater distensibility than their female counterparts (4.8 vs 2.5 × 10^-3, p < .01). Of patients with alkaptonuria, those with a coronary artery calcium (CAC) score greater than 100 had more impaired distensibility than those with a CAC score less than 100 (3.5 vs 5.1 × 10^-3, p = .01) and those with aortic calcium score greater than 100 had impaired distensibility compared to those with an aortic calcium score less than 100 (3.2 vs 4.9 × 10^-3, p = .02). Univariate analysis revealed age, aortic calcification, and hyperlipidemia to be significant factors of distensibility, and multiple regression analysis showed age as the only significant risk factor of distensibility.

Patients with alkaptonuria have impaired aortic distensibility, which is likely an early marker for reduced cardiovascular health. Variables such as age, hypertension, hyperlipidemia, and aortic and coronary calcification were associated with impaired distensibility.