The winter peak in the occurrence of acute aortic dissection is independent of climate.

We recently reported the existence of a higher risk of acute aortic dissection (AAD) during the winter months. However, it is not known whether this winter peak is affected by climate. To address this issue, we evaluated data from 969 AAD patients who were enrolled at various sites around the globe and who were participating in the International Registry of Acute Aortic Dissection (IRAD). We found a significant (p = 0.001; chi2 test) difference in the number of AAD events occurring during the different seasons of the year, with highest incidence in winter (28.4%) and lowest incidence in summer (19.9%). Furthermore, the winter peak was evident in both cold and temperate climate settings, suggesting that the relative change in temperature, rather than absolute temperature, and/or endogenous annual rhythms are critical mechanistic factors

Does circadian and seasonal variation in occurrence of acute aortic dissection influence in-hospital outcomes?

The risk of acute aortic dissection (AAD) exhibits chronobiological variations with peak onset in the morning and in winter. However, it is not known whether the time of day or season of the year of the AAD affects clinical outcomes. We studied 1,032 patients enrolled in the International Registry of Acute Aortic Dissection from January 1997 to December 2001. For circadian and seasonal analysis, the time and date of symptom onset were available for 741 and 1,007 patients, respectively, and were grouped into four 6h periods (morning, afternoon, evening, and night) and four seasons (winter, spring, summer, and autumn). The chi2 test for goodness of fit was used to evaluate non-uniformity of the time of day and time of year for critical in-hospital clinical events, including death. While highest incidence of AAD occurred in the morning and winter, clinical events (including mortality) were similar during the four different periods of the 24 h (chi2 = 1.9, p = 0.60) and seasonal (chi2 = 1.2, p = 0.75) periods

Changes in extracellular matrix in subcutaneous small resistance arteries of patients with primary aldosteronism

It has been previously demonstrated that aldosterone may possess a strong profibrotic action in vitro and in animal models of genetic or experimental hypertension. Our aim was to evaluate whether such a profibrotic action is present also in the human microcirculation. DESIGN AND PATIENTS: We investigated 13 patients with primary aldosteronism, seven patients with essential hypertension, and 10 normotensive controls. All subjects were submitted to a biopsy of gluteal sc fat tissue. Small resistance arteries were dissected and mounted on an isometric myograph, and the tunica media to internal lumen ratio was measured. MAIN OUTCOME MEASURES: The total collagen content within the tunica media was detected (Sirius red staining and image analysis), and collagen subtypes were evaluated using polarized light microscopy; under this condition thicker type I collagen fibers appear orange or red, whereas thinner type III collagen fibers are yellow or green. RESULTS: Tunica media to internal lumen ratio was significantly increased in primary aldosteronism and in essential hypertension compared with normotensive controls. Clinic blood pressure values were similar in primary aldosteronism and in essential hypertension, and greater than in normotensive controls. Normotensive controls had less total and type III collagen (3.23 +/- 0.58 and 1.60 +/- 0.22%, respectively) in respect to the two hypertensive groups (P < 0.001). Total collagen and type III vascular collagen were significantly greater in primary aldosteronism (total collagen, 8.17 +/- 1.38%; type III collagen, 6.06 +/- 0.74%; P < 0.05) than in essential hypertension (total collagen, 6.84 +/- 1.15%; type III collagen, 5.25 +/- 0.80%). CONCLUSIONS: Our results indicate that, in small resistance arteries of patients with primary aldosteronism, a pronounced fibrosis may be detected, even more evident than in blood-pressure-matched patients with essential hypertension