Comparison between three supportive treatments for prevention of contrast-induced nephropathy in high-risk patients undergoing coronary angiography.

Contrast-induced nephropathy is the third most common cause of acute renal failure in hospitalized patients. The purpose of this study was to compare three supportive treatments for prevention of contrast-induced nephropathy in high-risk patients undergoing coronary angiography. In this randomized clinical trial study, 150 patients with at least one risk factor, such as, congestive heart failure, history of diabetes mellitus, age>65 years or renal failure were randomly assigned to three equal groups: First group (Sodium (Na) bicarbonate infusion), second group [(N-Acetylcysteine (NAC)+Sodium Chloride (Nacl)], third group (Nacl). Angiography was performed with 350 mgI/mL of Iohexol (Omnipaque). Serum creatinine (Cr), blood blood urea nitrogen (BUN), and urine pH were measured at the start of angiography and 48 hours later. The three groups had no significant difference in demographic characteristics or other risk factors before intervention (P>0.05). Forty eight hours after exposure, the Cr level increased significantly in the Nacl group (P=0.039), while these changes were not significant in the other groups (P>0.05). The incidence of contrast-induced nephropathy was not statistically significant between all the groups (P=0.944). Although the Cr clearance had no statistically significant difference, it was lower in the NaCl group. Therefore, Na bicarbonate may be the treatment of choice in the prevention of contrast-induced nephropathy, because of less prescribed fluid volume and a lesser time required for infusion of the fluid.

The architecture of the left ventricular myocytes relative to left ventricular systolic function.

OBJECTIVE: Mural thickening, combined with longitudinal and circumferential shortening, and apical along with basal twisting are critical components of the left ventricular systolic deformation that contribute to ventricular ejection. It is axiomatic that the spatial alignment of the actively contracting aggregates of myocytes must play a major role in the resulting ventricular deformation. The need to conserve functional global myocytic architecture, therefore, is an important aspect of the surgical manoeuvres affecting ventricular mass and geometry. To investigate the influence of the global alignment of the myocytes on ventricular contraction, we used a mathematical model simulating the large deformations produced by systolic contraction of the left ventricle of a human heart. METHODS: The alignment and meshing of the myocytes within their supporting fibrous matrix cause mechanical anisotropy, which was included in the mathematical model in the form of a unit vector field, constructed from the measured trajectories of aggregated myocytes in an autopsied human heart. The relationship between ventricular structure and ventricular dynamics was assessed by analysing the influence of systematic deviations of the orientation of the myocytes from their original alignment, in longitudinal as well as radial directions, on the distribution of stress and strain within the myocardium, as well as on the ejection fraction. In addition, simplified idealised geometries were used to investigate the influence of the overall geometrical modifications. RESULTS: Left ventricular function proved to be robust with respect to small-to-moderate rotational variations in myocytic alignment, up to 14 degrees , a finding which we attribute to an equalising effect of the non-uniform anisotropic pattern found in a real heart involving substantial local irregularities in the architecture of the aggregated myocytes. Severe deterioration of function occurred only when deviations in alignment exceeded 30 degrees . CONCLUSIONS: Our findings substantiate the concept of the myocardial walls representing a continuous three-dimensional meshwork, with the absence of any intermediate structures such as discrete bands or tracts extending over the ventricles, which could be destroyed surgically, thereby adversely affecting systolic function. With appropriate indications, they also support the validity of the surgical procedures performed to reduce ventricular radius and therefore to reduce mural stress.

An analysis of the spatial arrangement of the myocardial aggregates making up the wall of the left ventricle.

OBJECTIVE: We used the technique of peeling of myocardial aggregates, usually described as 'fibres', to determine the spatial arrangement of the myocytes in the left ventricular wall of a healthy autopsied human heart. METHODS: We digitised the left ventricular outer and inner boundaries, as well as the pathways in space, of almost 3000 aggregates harvested from the left ventricular myocardium. During the process of gradual peeling, we sought to identify the myocardial aggregates as uniformly as possible. Despite this, interpolation was necessary to complete the pattern so as to construct a unit vector field that represented the preferred direction of the myocardial aggregates throughout the entirety of the walls of the left ventricle of this individual human heart. RESULTS: Apart from the overall systematic arrangement of the aggregates necessary to achieve physiologic ventricular contraction, we documented substantial local heterogeneities in the orientation of the myocardial aggregates. In particular, a significant proportion of aggregates was found to intrude obliquely with respect to the ventricular boundaries, with markedly heterogeneous distribution. Moreover, the distribution of the helical angle of the aggregates relative to the ventricular base varied notably throughout the left ventricular free walls and the septum. Within the generally quite uniform and continuous structure of the ventricular mass, we were, however, unable to identify any organised tracts or functional subunits such as a 'helical ventricular band', nor did we find radial fibrous lamellas coursing across the ventricular wall. CONCLUSION: We suggest that the impact of local anatomical inhomogeneities, associated with gradients in regional contractile function on global ventricular dynamics, has been systematically underestimated in the past. Our analysis confirms furthermore the continuous nature of the myocardium associated with an overall gross organisation of the fibre direction field; however, there is no evidence of substructures compartmentalising the ventricles.