Health & Medical Kidney & Urinary System

Association of Pulse Wave Velocity With Vascular and Valvular Calcification

´╗┐Association of Pulse Wave Velocity With Vascular and Valvular Calcification

Abstract and Introduction

Abstract


The recent Kidney Disease: Improving Quality Outcomes (KDIGO) recommendations called for an investigation of the relationship between various radiological methods to assess cardiovascular calcification and measures of arterial stiffness. Accordingly, in 131 adult maintenance hemodialysis patients, we investigated the association of aortic pulse wave velocity (PWV) with calcification of cardiac valves on echocardiography, coronary artery, and thoracic aorta calcium on computed tomography and a calcification score of the abdominal aorta obtained on a plain abdominal X-ray. All tests were performed within a week. Mean PWV increased as the severity of coronary artery, thoracic, and abdominal aorta calcium scores increased (each P<0.05). No trend was present for number of valves with calcification. After multivariable adjustment, abdominal aorta X-ray calcium scores remained associated with PWV (P=0.004), whereas the association of PWV with thoracic aorta and coronary artery calcium scores became marginal (P=0.308 and P=0.083, respectively). No association was found between number of calcified valves and PWV. This study demonstrates a strong association between abdominal aorta calcification on plain X-ray and PWV and a borderline association with thoracic aorta and coronary artery calcification. Sudden death and congestive heart failure, two frequent causes of death in hemodialysis, are likely caused by increased arterial stiffness that can be closely predicted by the presence of aortic calcification on plain X-rays.

Introduction


Patients with all stage of chronic kidney disease (CKD), but especially those with end-stage renal disease (CKD-5), suffer a very high rate of cardiovascular events. As a consequence, both the National Kidney Foundation and the American Heart Association have stated that CKD-5 patients should be considered at the highest risk for cardiovascular disease. Although many traditional risk factors play an important role, several nontraditional factors, such as alteration of bone and mineral metabolism and a heightened oxidative and inflammatory state, appear to contribute substantially to the increased risk.

It has also been suggested that extensive cardiovascular calcification develops as one of the consequences of bone and mineral metabolism derangement. The severity of vascular and valvular calcification has been assessed by plain radiography, ultrasonography, echocardiography and, most recently, cardiac computed tomography (CT). Regardless of modality, cardiovascular calcification has been associated with an increased risk of death in CKD-5 patients. Although cardiac CT is very accurate and the only true quantitative method currently available to assess the extent of cardiovascular calcification, this technique is costly and involves exposing patients to radiation.

Other noninvasive techniques to assess cardiovascular risk have therefore gained considerable popularity. One of the most helpful is pulse wave velocity (PWV), which is used to evaluate vascular stiffness. Vascular stiffness translates into higher conduction velocity of an impulse along the vessel length. Decreased elasticity is the result of many contributing factors, such as atherosclerosis, vascular wall calcification, and changes in collagen and elastin content in the vessel wall. Of note, an increased PWV has been associated with an excess morbidity and mortality risk in CKD-5 and in the general population. Because cardiovascular research is actively employing radiological techniques and PWV measurements in CKD-5, it is important to know how these tools relate to each other. Indeed, the recent Kidney Disease: Improving Global Outcome (KDIGO) recommendations called for further investigation into the relationship between radiological tools for assessment of cardiovascular calcification and methods to assess vascular stiffness. Therefore, we addressed this important question by performing simultaneously four tests in a cross-sectional cohort of hemodialysis patients: PWV for vascular stiffness, echocardiography to assess presence of valvular calcification, chest CT to measure coronary artery and thoracic aorta calcification, and a lateral lumbar X-ray to assess the presence of abdominal aorta calcification.

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