Pulmonary atelectasis: signal patterns with MR imaging

To assess the signal characteristics of different types of pulmonary atelectasis on magnetic resonance (MR) images, the authors studied obstructive atelectasis (OA) in 17 patients and nonobstructive atelectasis (NOA) in 25 patients. All patients underwent electrocardiographically gated MR imaging studies of the thorax with standard spin-echo sequences. No signal differences were observed between either type of atelectasis on T1-weighted images. Conversely, OA and NOA appeared significantly different on spin-density-weighted images (P less than .001) and on T2-weighted studies (P less than .0001). On T2-weighted images, all 17 cases of OA appeared hyperintense, whereas 22 of 25 cases of NOA demonstrated a very low signal intensity. Differences in the pathophysiology of OA and NOA presumably account for this observation. In OA, alveolar air is totally resorbed and secretions accumulate in the obstructed lung. The resulting increase in free fluid prolongs the T2 relaxation times and leads to high signal intensity on T2-weighted images. In NOA, the short T2 relaxation time of lung tissue in the absence of secretions and potential magnetic susceptibility effects due to residual air are likely to be responsible for the low T2 signal pattern.     

Oxidative stress in patients with acute heart failure

Oxidative stress (OS) is a keystone in the pathology of the ischemia reperfusion sequence (acute coronary syndromes, cardiac surgery, transplantation). In heart failure, the implication of OS is less understood. This study was intended to evaluate OS in acute heart failure. Criteria for inclusion were consecutive patients hospitalized in our cardiology department for a first pulmonary edema that revealed a dilated cardiomyopathy (DCM). Exclusion criteria included known cardiomyopathy, smoker, acute coronary syndrome, and treatment with angiotensin converting enzyme inhibitors (ACEI) or angiotensin II receptor blockers (ARAII). OS was evaluated in blood samples: thiobarbituric acid-reactive substances (TBARS), total antioxidant status (TAS), plasma alpha-tocopherol, vitamin A, and beta-carotene. Standard biochemical parameters including CRP, fibrinogen, lipid, and creatinine were assayed. Ten patients (80% men, mean age 55.3 +/- 7.9 years) were included and followed during a 6 month period. The etiologies of DCM were alcohol (n = 3), anti-cancer drugs (n = 2), valvulopathies (n = 2), or idiopathic (n = 3). In acute heart failure, TBARS were elevated (1.69 micromol/L; normal value 0.6-4.2 micromol/L) and TAS status was decreased (0.96 mmol/L; normal value 1.3-1.9 pmol/L). OS was more important when patients had atrial or ventricular arrhythmia. Nevertheless, liposoluble antioxidant parameters (beta-carotene, vitamin A, alpha-tocopherol) had a usual value. At the term of the follow-up, patients returned to a stable condition, OS markers revealed normal values, and every Holter ECG showed no supraventricular or ventricular arrhythmias. In acute heart failure, oxygen-free radicals are increased. We thus hypothetized that a modification in OS could be responsible for arrhythmias and complications of acute heart failure.     

Solitary pulmonary nodules: CT assessment

Computed tomography (CT) was used to examine 634 solitary pulmonary nodules (SPNs). Each lesion was assessed as benign or indeterminate on the basis of CT criteria. Benign nodules made up 44% of all SPNs and 58% of the 431 that were 2 cm or less in diameter. All malignant SPNs were assessed as indeterminate, and adenocarcinoma (42%) was the most common primary malignancy. A total of 176 (63% of benign SPNs) were correctly assessed as benign by CT. Ninety SPNs assessed as diffusely calcified were not so identified by conventional tomography at outside institutions. An SPN can be reliably assessed by CT as benign if it exhibits high attenuation values, exceeding a critical level and distributed diffusely throughout a CT section through the center of the lesion and a well-defined edge. Although 38 of 283 (13.4%) primary lung cancers contained localized calcification, there was no significant overlap with the diffuse calcification of benign lesions. Central carcinoid tumors may contain focal ossification, but such lesions may be recognized by noting the proximity of larger bronchi. Assessment of SPNs by CT is most effective for lesions 2.0 cm or less in diameter. For larger lesions, the frequency of benign disease was decreased (14.3% of 203), as was the percentage of benign SPNs correctly assessed as benign by CT (37.9%).