Occurrence Of Acute Aortic Dissection Research Articles

Short-term effects of air pollution and weather changes on the occurrence of acute aortic dissection in a cold region.

Air pollution and severe weather conditions can adversely affect cardiovascular disease emergencies. Nevertheless, it remains unclear whether air pollutants and low ambient temperature can trigger the occurrence of acute aortic dissection (AAD) in cold regions. We applied a retrospective analysis to assess the short-term effects of air pollution and ambient temperature on the occurrence of AAD in Harbin, China. A total of 564 AAD patients were enrolled from a major hospital in Harbin between January 1, 2017, and February 5, 2021. Weather condition data and air pollutant concentrations, including fine particulate matter smaller than 10 μm (PM10) and 2.5 μm in diameter (PM2.5), nitrogen dioxide (NO2), sulfur dioxide (SO2), carbon monoxide (CO), and ozone (O3), were collected every day. Conditional logistic regressions and correlation analysis were applied to analyze the relationship of environmental and atmospheric parameters with AAD occurrence at lags of 0 to 7 days. Specifically, we appraised the air quality index, CO, NO2, SO2, O3, PM10, PM2.5, temperature, dew point temperature, atmospheric pressure, and cloud amount. A total of 1,496 days at risk were assessed, of which 564 patients developed AAD. Specifically, AAD did not occur on 1,043 (69.72%) days, while 1 or more cases occurred on 453 (30.28%) days. Several pollution and weather predictors for AAD were confirmed by multilevel modeling. The air quality index (p = 0.0012), cloud amount (p = 0.0001), and concentrations of PM2.5 (p = 0.0004), PM10 (p = 0.0013), NO2 (p = 0.0007) and O3 (p = 0.0001) predicted AAD as early as 7 days before the incident (lag of 7 days) in the study period. However, only concentrations of the air pollutants NO2 (p = 0.0468) and O3 (p = 0.011) predicted the occurrence of AAD after the COVID-19 outbreak. Similar predictive effects were observed for temperature, dew point temperature, and atmospheric pressure (all p < 0.05) on all days. The risk of AAD is closely related to air pollution and weather characteristics in Harbin. While causation was not determined, the impact of air pollutants on the risk of AAD was reduced after the COVID-19 outbreak.

The Predictive Value of Inter Arm Blood Pressure Difference, Inter Leg Blood Pressure Difference and Ankle Brachial Index for Acute Aortic Dissection.

Abnormal inter arm systolic blood pressure, inter leg systolic blood pressure and ankle brachial index (ABI) are related to vascular diseases. Our aim was to evaluate the correlation of inter arm systolic blood pressure difference (IASBPD), inter leg systolic blood pressure difference (ILSBPD), and ABI with acute aortic dissection (AAD) and their role in predicting AAD. In this prospective case-control study, 180 patients with AAD admitted to the emergency department were prospectively and consecutively collected in Tongji Hospital from October 2019 to December 2020. 180 healthy people matched by sex, age and BMI served as control group. All participants were adults over 18 years of age who underwent four-limb blood pressure measurements. IASBPD, ILSBPD and ABI were compared between the two groups and their associations with AAD were analyzed. A total of 360 patients (180 cases and 180 controls) were analyzed. In case group IASBPD was larger [(15.23 16.15) mm Hg vs. (4.19 3.63) mm Hg] and ILSBPD was larger (13.00 mm Hg vs. 5.70 mm Hg). ABI was smaller [(0.98 0.24) vs. (1.12 0.09)], and the difference was statistically significant (all p 0.05). According to the receiver operating characteristic curve (ROC), IASBPD 10 mm Hg (Sen 61.7%, Spe 88.9%), ILSBPD 13 mm Hg (Sen 50.6%, Spe 80.6%) and ABI 0.9 (Sen 53.3%, Spe 87.2%), showed significant correlation with AAD (all p 0.001). Compared with healthy people, IASBPD and ILSBPD levels were higher and ABI levels were lower in patients with AAD. IASBPD 10 mm Hg and ILSBPD 13 mm Hg can be used as indicators for early screening of AAD, and IASBPD 10 mm Hg has better predictive value for the occurrence of AAD. In patients with typical chest pain, attention needs to be paid to measuring blood pressure in the extremities.

Association of Daily Mean Temperature and Temperature Variability With Onset Risks of Acute Aortic Dissection.

BackgroundThe association between ambient temperature and cardiovascular diseases has been well established, but evidence of temporal changes in the risk of acute aortic dissection (AAD) onset is lacking.Methods and ResultsWe conducted an 8‐year time‐series study based on data from 2120 patients diagnosed with AAD at Tongji Hospital (Wuhan, China). Daily meteorological parameters were measured in the study area. Spearman's rank correlation analysis was applied to measure the associations between daily meteorological data and air pollution indicators. A distributed lag nonlinear model following quasi‐Poisson regression was used to express the nonlinear exposure‐response relationships and lag effects of daily mean temperature and temperature variability on the occurrence of AAD. Considering a 25‐day lag effect, lower or higher temperatures with reference to 25°C did not alter the onset risk of AAD. The lag effect of daily mean temperature on the incidence of AAD is statistically significant within 2 days, and the impact of daily mean temperature on the risk is most influential on the day. The exposure‐response curve between daily mean temperature and onset risks of AAD at lag 0 showed that the extremely cold temperature (2.5th percentile, 0.5°C) significantly increased the AAD risk for the total (relative risk, 1.733; 95% CI, 1.130–2.658) and type A dissection (relative risk, 3.951; 95% CI, 1.657–9.418). Temperature variability within 1 week did not affect the onset risks of AAD for the total.ConclusionsWe confirmed that extremely cold temperatures significantly increased the AAD risk, which could contribute to early prevention and timely diagnosis of the disease.

Do meteorological factors influence the occurrence of acute aortic dissection? A 10-year retrospective institutional study.

This study aimed to clarify the relationship between meteorological factors and the occurrence of aortic dissection. The study included 282 consecutive patients who were admitted to our institute with acute aortic dissection over a 10-year period. The local meteorological data over the same period were analyzed. On the days with occurrences of acute aortic dissection, there were significant differences in the following factors: the minimum and maximum temperature (p < 0.0001), difference in the minimum and maximum temperature from the 10-year average, atmospheric pressure (p < 0.0001), and difference in atmospheric pressure between the day of occurrence and the previous day. Cut-off values were determined by ROC curve analysis. Univariate analyses identified the following factors as significant predictors of the occurrence of acute aortic dissection: minimum temperature < 4.0°C (OR 2.42, p < 0.0001), maximum temperature < 15.1°C (OR 2.23, p < 0.0001), atmospheric pressure > 1008.9hPa (OR 1.75, p < 0.0001), difference between the minimum temperature and 10-year average < 0.3°C, difference between the maximum temperature and 10-year average < 0.44°C; and the difference in atmospheric pressure between the day of occurrence and the previous day > 0.4hPa. However, the differences of the minimum and maximum temperatures from the 10-year average were the only factors that remained significant in the multivariate analysis. The minimum (R2 = 0.3055) and maximum temperatures (R2 = 0.4151) were weakly and moderately correlated, respectively, with the occurrence of acute aortic dissection. Meteorological factors influenced the occurrence of acute aortic dissection. In particular, a minimum temperature of < 4°C and maximum temperature difference from the 10-year average < 0.44°C was identified as strong risk factors for the occurrence of acute aortic dissection.

Evaluation of Common Carotid Stiffness via Echo Tracking in Hypertensive Patients Complicated by Acute Aortic Dissection.

ObjectivesTo evaluate the common carotid stiffness via echo tracking in patients with hypertension and acute aortic dissection (AD) and to investigate the independent predictors for the occurrence of AD in hypertensive (HP) patients.MethodsFifty HP patients complicated by acute AD (AD group), 50 HP patients without AD (HP group), and 50 age‐matched healthy volunteers (control group) were enrolled to assess the common carotid stiffness index (β), single‐point pulsed wave velocity (PWVβ), and arterial compliance (AC) via echo tracking.ResultsThe intima‐media thickness, diameter, β and PWVβ of the common carotid artery (CCA) in the AD group were significantly higher than those in the HP and control groups, whereas AC in the AD group was significantly lower (P < .05). In a multivariate logistic regression analysis, the systolic blood pressure (SBP; odds ratio [OR], 2.316; 95% confidence interval [CI], 2.033–2.563; P < .001), β (OR, 2.140; 95% CI, 1.931–2.367; P < .001), PWVβ (OR, 1.212; 95% CI, 1.004–1.397; P = .023), and AC (OR, 0.565; 95% CI, 0.339–0.654; P < .001) were significantly related to the occurrence of AD in HP patients. The area under the curve values for the AC, SBP, β, and PWVβ were 0.822, 0.806, 0.778, and 0.741, respectively, and the area under the curve was up to 0.943 when these parameters were combined.ConclusionsThe compliance of the CCA decreased, and the stiffness of the CCA increased significantly in HP patients complicated by AD. The AC, β, and PWVβ of the CCA, together with the SBP, were independent predictors of the occurrence of AD in HP patients.

Impact of meteorological factors on the occurrence of acute aortic dissection in Fujian Province, China: a single-center seven-year retrospective study

BackgroundThe aim of this study was to investigate the correlation between meteorological factors and the occurrence of acute aortic dissection (AAD) in Fujian Province, China.MethodsThe clinical data of 2004 patients diagnosed with AAD in our hospital and the relevant local meteorological data from January 2013 to November 2019 were retrospectively analyzed.ResultsThe incidence of AAD had a clear tendency toward concentration, and the corresponding peak in terms of the occurrence date was from January 13 to 14. The average minimum temperature, the average maximum temperature, and the average daily temperature differences on the “day with AAD” were significantly lower than those on the “day without AAD”. From 5 days to 3 days before AAD onset, the average daily temperature difference showed a downward trend, but statistical analysis showed that the average minimum, average maximum and average daily temperature differences were not significantly different from the values 5 days to 0 days before AAD onset.ConclusionsThe incidence of AAD is related to the season and month. The lowest average temperature may increase the incidence of AAD in patients with complicated cardiovascular diseases.

Meteorological and chronobiological factors and the occurrence of acute aortic dissection.

Although a number of studies have demonstrated seasonal variations in acute cardiovascular events, the association between winter and low temperatures and the incidence rate of acute aortic dissection has not been fully elucidated. In this study, we investigated the association between meteorological and chronobiological factors and the occurrence of acute aortic dissection classified by the Stanford type, sex and age. We retrospectively collected 131 patients who had been admitted consecutively to our institution with acute aortic dissection, including 58 type A patients and 73 type B patients, from January 2013 to December 2017. The meteorological data were downloaded from the homepage of the Japan Meteorological Agency. The daily incidence of aortic dissection was higher in winter (10.2%) than in fall (5.3%) (P = 0.04), and a significant winter peak was also observed in the sub-groups of males and type B, while there were no significant differences in the proportions of type A, female, and ≤ 70- and > 70-year-old patients. The maximum, mean and minimum temperatures on the days with aortic dissection were significantly lower than on the days without aortic dissection. Divided into four seasons, lower temperatures were found only in spring. The most significant and greatest difference was observed between the maximum temperature on the day of aortic dissection and that at 2days earlier. The multivariate logistic regression analysis showed that the difference in the maximum temperature between the day of and 2days before the incident (odds ratio 0.91; 95% confidence interval 0.87-0.96; P < 0.01) as well as the maximum temperature (odds ratio 0.97; 95% confidence interval 0.95-0.99; P = 0.02) were significantly associated with the incidence of aortic dissection. Cold weather and a sudden decrease in temperature might trigger aortic dissection, although the influence might differ among sub-groups.

P32 Do meteorological factors influence the occurrence of acute aortic dissection?A ten-year retrospective institutional review

Abstract Purpose Some studies have reported a relationship between meteorological factors and the occurrence of acute aortic dissection (AAD). Nevertheless, the results of the studies are heterogeneous. Furthermore, whether the absolute values or fluctuation of meteorological factors influence the occurrence of AAD remains controversial. The aim of this study was to determine the meteorological factors associated with the occurrence of AAD. Methods Two hundred eighty-two consecutive patients (male, n = 178; female, n = 104; average age, 68 years) admitted to our hospital for AAD in the 10 years from September 1st 2008 were included in this study. One hundred fifty-seven patients had type A dissection. The correlation between the clinical data and the local meteorological data over the same period (provided by the National Meteorological Agency) was analyzed. We compared the following factors on days of AAD occurrence and non-occurrence: minimum and maximum temperature, minimum and maximum temperature difference between day of occurrence and previous day, difference between maximum and minimum temperature, atmospheric pressure and atmospheric pressure difference between day of occurrence and previous day (Δatmospheric pressure), and minimum and maximum temperature difference from climatological standard normal (CSN). Cutoff values were determined by ROC curve analyses and odds ratios (ORs) were calculated by a logistic regression analysis of meteorological factors with statistically significant differences. Results ignificant differences between the days of AAD occurrence and non-occurrence were observed for minimum and maximum temperature (p &amp;lt; 0.0001), atmospheric pressure (p &amp;lt; 0.0001) and Δatmospheric pressure (p = 0.0286), minimum temperature difference from CSN (p &amp;lt; 0.0001), and maximum temperature difference from CSN (p = 0.0010). The cutoff values were as follows: minimum temperature, 4°C; maximum temperature, 15.1°C; atmospheric pressure, 1008.9hPa; Δatmospheric pressure, 0.4hPa; minimum temperature difference from CSN, 1°C; and maximum temperature difference from CSN, -0.2°C. The univariate logistic regression model showed revealed the following significant predictors of the occurrence of AAD; minimum temperature (OR2.42, p &amp;lt; 0.0001), maximum temperature (OR2.23, p &amp;lt; 0.0001), air pressure (OR1.75, p &amp;lt; 0.0001), Δatmospheric pressure (OR 1.44, p = 0.0030), minimum temperature difference from CSN (OR1.80, p &amp;lt; 0.0001) and maximum temperature difference from CSN (OR1.58, p = 0.0003). However, only minimum temperature (OR1.60, 95% CI 1.00-2.53, p = 0.0478) and maximum temperature difference from CSN (OR1.45, 95% CI 1.11-1.89, p = 0.0062) remained significant in the multivariate analysis. Conclusion Meteorological factors, especially a minimum temperature under 4°C strongly influenced the occurrence of AAD. A maximum temperature difference from CSN of over -0.2°C was also a significant predictor of AAD.

IL-5 overexpression attenuates aortic dissection by reducing inflammation and smooth muscle cell apoptosis

BackgroundAs an inflammation-related cytokine, interleukin (IL)-5 has been reported to be involved in the development of cardiovascular diseases, such as chronic heart failure and atherosclerosis. However, the role of IL-5 in acute aortic dissection (AAD) has barely been explored. MethodsAortic tissue samples from normal donors and patients with AAD were collected, and the expression and localization of IL-5 in aortic tissue were analyzed. In addition, a mouse AAD model was established by administering angiotensin II (Ang II) to β-aminopropionitrile (BAPN)-treated mice. Morphological examinations and histopathologic analyses were performed to evaluate the effects of IL-5 overexpression on the occurrence of AAD. ResultsIL-5 expression was significantly decreased in aorta samples from AAD patients compared to those from donors, and macrophages were the main source of IL-5. In addition, IL-5 expression was decreased in plasma and aortic tissue samples from AAD mice. IL-5 overexpression markedly attenuated the occurrence of AAD in mice and produced corresponding decreases in the inflammatory response and cell apoptosis. In cocultures of macrophages and smooth muscle cells (SMCs), IL-5 overexpression in the macrophages significantly reduced Ang II-induced SMC apoptosis. ConclusionIL-5 overexpression suppresses the development of AAD by reducing inflammation and SMC apoptosis. These results suggest that IL-5 is a potential therapeutic target in AAD.

Clinical Features of Patients With Acute Aortic Dissection After an Earthquake: Experience from the Kumamoto Earthquake 2016.

While there is a concern about the increase in the occurrence of acute aortic dissection (AAD) caused by the worsening of hypertension, mental stress, etc., there is a lack of data regarding the influence of disasters on this event. The aim of this study was to address this issue in the acute-subacute phase after the Kumamoto Earthquake occurred on 14 April 2016. We retrospectively investigated the impacts of the Kumamoto Earthquake on various cardiovascular diseases, including AAD, utilizing the medical records of patients in 16 hospitals in Kumamoto Prefecture during the period from 14 April to 30 June (78 days) in 2014, 2015, 2016, and 2017. The occurrence of heart failure and venous thromboembolism increased significantly in the acute-subacute phase after the earthquake. When comparing the earthquake year (2016) to the non-earthquake years (2014, 2015, and 2017), the difference in the occurrences and mortalities of AADs were not significant. When other characteristics of the patients were compared between the earthquake year and the non-earthquake years, there were no differences. It might be possible that the Kumamoto Earthquake did not affect the incidence of AAD or deaths from AAD, possibly because the climate was mild and the preventive efforts based on previous experience were successful. University Hospital Medical Information Network (UMIN)-CTR (http://www.umin.ac.jp/ctr/). UMIN000023864. Opt-out materials were available at the following website: http://www.kumadai-junnai.com/home/wp-content/uploads/shinsai.pdf.

Impact of meteorological conditions on the incidence of acute aortic dissection.

There is still much controversy about whether meteorological conditions influence the occurrence of acute aortic dissection (AAD). The aim of the present study was to investigate the possible correlation between atmospheric pressure, temperature, lunar cycle and the event of aortic dissection in our patient population. The clinical data for 348 patients with AAD (73% type Stanford A) were confronted with the meteorological data provided by the Cologne weather station over the same period. There were no statistically significant differences between meteorological parameters on days of AAD events compared with control days. A logistic regression model showed that air pressure (odds ratio [OR] 1.004, 95% confidence interval [CI] 0.991-1.017, p = 0.542), air temperature (OR 0.978, 95% CI 0.949-1.008, p = 0.145), season ( p = 0.918) and month of the event ( p = 0.175) as well as presence of full moon (OR 1.579, 95% CI 0.763-3.270, p = 0.219) were not able to predict AAD events. Also, no predictive power of meteorological data and season was found on analysing their impact on different types of AAD events. Our study did not reveal any dependence of atmospheric pressure, air temperature or the presence of full moon on the incidence of different types of AAD.

Meta-Analysis of Circadian Variation in the Onset of Acute Aortic Dissection

Circadian variation in the onset of acute aortic dissection (AAD) has been less investigated than other cardiovascular diseases. We performed a meta-analysis to assess the presence of an circadian rhythmic variability of AAD onset. Eligible studies were observational studies enrolling patients with AAD and reporting a circadian variation in AAD. Study-specific estimates, that is, 2-hour incidence of AAD, were combined using the random-effects model. Chronobiological analysis (analysis of circadian rhythmicity) was performed by applying a partial Fourier series to the pooled 2-hour incidence using the weighted least-squares method. We identified 7 eligible studies enrolling a total of 1,827 patients with AAD. Pooled 2-hour period incidence of AAD was 3.4% in 0:00 to 2:00, 4.8% in 2:00 to 4:00, 5.4% in 4:00 to 6:00, 9.6% in 6:00 to 8:00, 13.8% in 8:00 to 10:00, 11.1% in 10:00 to 12:00, 8.1% in 12:00 to 14:00, 8.9% in 14:00 to 16:00, 8.8% in 16:00 to 18:00, 7.0% in 18:00 to 20:00, 8.1% in 20:00 to 22:00), and 5.5% in 22:00 to 24:00. Chronobiological analysis (nonlinear Fourier rhythm analysis) identified a significant (p = 0.0082) circadian pattern in the occurrence of AAD with a peak in 8:00 to 10:00 and a nadir in 0:00 to 2:00. Pooled analysis demonstrated significantly more incidence in 8:00 to 10:00 than in 0:00 to 2:00 (risk ratio 3.59, 95% confidence interval 2.19 to 5.90, p<0.00001). The incidence of AAD was 8.8%, 15.5%, 25.0%, 17.7%, 16.1%, and 13.8% in 0:00 to 4:00, 4:00 to 8:00, 8:00 to 12:00, 12:00 to 16:00, 16:00 to 20:00, and 20:00 to 24:00, respectively. A significant circadian pattern was found in the occurrence of AAD with a peak in 8:00 to 10:00 and a nadir in 0:00 to 2:00.

JAK2-Centered Interactome Hotspot Identified by an Integrative Network Algorithm in Acute Stanford Type A Aortic Dissection

The precise mechanisms underlying dissections, especially those without connective tissue diseases or congenital vascular diseases, are incompletely understood. This study attempted to identify both the expression profile of the dissected ascending aorta and the interactome hotspots associated with the disease, using microarray technology and gene regulatory network analysis. There were 2,737 genes differentially expressed between patients with acute Stanford type A aortic dissection and controls. Eight interactome hotspots significantly associated with aortic dissection were identified by an integrative network algorithm. In particular, we identified a JAK2-centered expression module, which was validated in an independent gene expression microarray data set, and which was characterized by over-expressed cytokines and receptors in acute aortic dissection cases, indicating that JAK2 may play a key role in the inflammatory process, which potentially contributes to the occurrence of acute aortic dissection. Overall, the analytical strategy used in this study offered the possibility to identify functional relevant network modules and subsequently facilitated the biological interpretation in the complicated disease.

Stanford type A aortic dissection after urgent prosthetic valve replacement: case reports

Occurrence of acute aortic dissection after aortic valve replacement is rare, however, it is associated with high mortality and morbidity rates. We report two Asian cases in which acute aortic dissection occurred after urgent aortic valve replacement for infective endocarditis. Successful graft replacement was carried out with preservation of the prosthetic valves in both cases. Our experience with these cases suggests that, even in urgent or emergent situations, surgical intervention for associated aortic dilatation should be considered when aortic valve replacement is performed.

Sleep disorders and aortic dissection in a working population

The aim of the present study was to assess the relationship between acute aortic dissection (AAD) and sleep disorders in a working population. Seventy (50.4%) of 139 younger subjects with AAD suffered from sleep disorders. Insomnia was reported by 35 patients (50%), sleep deprivation by 31 patients (44.3%), and sleep apnea syndrome was present in 43 patients (61.4%). The average apnea-hypopnea index was 22.0±7.5 points, requiring appropriate treatment. Most of these patients had irregular daily schedules due to job pressure. Sixty-six (94.3%) complained of severe mental and physical stress in daily life. Sleep disorders are considered one of the risk factors for the occurrence of AAD at younger active ages. In primary care for patients with mental or physical stress due to their daily life, it is important to assess these individuals for the presence of sleep disorders.

Does Acute Aortic Dissection Display Seasonal Variation?

The relation between cardiovascular diseases and the seasons is well known; however, only a few reports have addressed the seasonal aspects of acute aortic dissections. We investigated whether presentation of acute aortic dissection has monthly/seasonal variations. From February 1985 to January 2006, 165 consecutive patients with aortic dissection admitted to our institution were reviewed. During this period, regional monthly atmospheric pressure data were supplied by the state's meteorological service. The mean and SD of atmospheric pressure data were analyzed statistically. The frequency of acute aortic dissection was found to be significantly higher during winter versus other seasons (P = .041). A relatively high positive correlation was found between the incidence of acute aortic dissection and the mean atmospheric pressure (P = .037). The study confirmed monthly variation with a peak in January. In winter, the frequency of acute aortic dissection was higher in male than in female patients. This study demonstrates that the occurrence of acute aortic dissection has significant seasonal/monthly variations. Thus, these observations may be a guide for prevention of acute aortic dissections by structuring treatment approaches with consideration given to the times of the year that patients are most vulnerable.

Temporal Variations at the Onset of Spontaneous Acute Aortic Dissection

There have only been a few studies of the chronobiological occurrence of acute aortic dissection (AAD), and most were international and multicentered. The aim of the present study, conducted at only one center, was to determine the most frequent daily, monthly, and seasonal occurrences of AAD. The study population included 204 patients (66.5% male) treated at our institute between January 1, 1998 and January 1, 2004. A significantly higher frequency of AAD occurred from 6:00 AM to 12:00 noon, compared with other time periods (P < 0.001). The results showed a significant circadian variation in AAD (P < 0.001) with a peak between 9:00 AM and 10:00 AM. No significant variation was found for the day of the week; however, AAD occurred most frequently on Wednesday and Monday. The frequency of AAD was found to be significantly higher during winter versus other seasons (P < 0.001). The analysis of monthly variations of the onset of AAD confirmed a peak in February (12.9%) and in January (12.3%). Similar to other cardiovascular diseases, AAD exhibits significant circadian and seasonal/monthly variations. Our findings indicate that the prevention of AAD, especially during the aforementioned vulnerable periods, is possible by adequate tailoring of the treatment of hypertension, which is the main AAD predisposing factor.

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; χ2 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.

Triggers and circadian distribution of the onset of acute aortic dissection.

The purpose of this study was to clarify the activities that trigger the onset of acute aortic dissection (AAD) and their relation to the occurrence of AAD. The study group comprised 444 consecutive patients referred for spontaneous AAD. From the hospital medical records, the activities that triggered AAD could be identified in 307 of these: most (86.6%) AAD episodes occurred in relation to physical (73.6%) or mental (13%) activities. In the older (> or =61 years) population, AAD occurred significantly more frequent during sleep or rest than in the younger (< or =60 years) population (16.9% vs 7.6%, p=0.020). The relationship between the time of onset and the triggering activity of AAD could be assessed in 267 patients. The onset of AAD was predominantly during the day: 63.3% of the episodes occurred between 06.00h and 18.00h, and were significantly more related to physical or mental activities than the nighttime events (95.3% vs 70.4%, p<0.0001). Most (86.6%) of the AAD episodes were related to physical or mental stress, particularly those that occurred during the day.

Collagen and elastin degradation by matrix metalloproteinases and tissue inhibitors of matrix metalloproteinase in aortic dissection

The degradation of collagen fibrils and elastic fibers in 21 casesof acute aortic dissection (AD) was ultrastructurally and immunohistochemicall investigated; and the expression of the catabolic matrix metalloproteinases (MMPs)-1, -2, -3, and -9 and their inhibitors, the tissue inhibitors of matrix metalloproteinase (TIIMPs)-1 and -2, was studied. The features of the entry site of the dissection (ES; 21 ascending aortas) were compared with those of fully remote sites (RS; 19 nondissected abdominal aortas) and the ascending aortas from 10 control cases. By electron microscopy, the medial layer at the ES and adjacent intact aortic wall demonstrated spirally thickened collagen fibrils with a typical banding pattern that were almost always colocalized with elastic lamellae, which often exhibited attenuation, fragmentation, or disruption. In addition, the basement membrane surrounding the smooth muscle cells (SMCs) comprising the media was frequently thinned or lost at the ES. These findings were rarely seen at the RS or in the aortas of controls. Immunohistochemically, the expression of MW-1 was significantly in the cytoplasm of SMCs of both the intima and media at the ES and adjacent intact wall, and significant expression of MMP-2 and -9 was found in SMCs of the intima compared with the RS and controls. Significant expression of TIMP-1 and -2 was demonstrated in the cytoplasm of SMCs at the ES and adjacent intact wall compared with that at the RS and the control specimens. These findings suggest that the degradation of proteins associated with fibrosis and the occurrence of AD are not merely coincident, but rather that AD is induced by alterations of the extracellular matrix caused by changes of SMCs at a segment of the ascending aorta made vulnerable through hemodynamic stress, especially that caused by hypertension.