Impact of meteorological conditions on the occurrence of acute type A aortic dissections

Interactive CardioVascular and Thoracic Surgery, Mar 2010

The impact of meteorological conditions on the occurrence of various cardiovascular events has been reported. The aim of this work was to study the correlations between weather conditions and the occurrence of type A acute aortic dissections (AADs). Between 1997 and 2007, all the medical records of patients who underwent surgery for type A AADs in Toulouse University Hospital (France) were reviewed. The clinical data were confronted with the meteorological data provided by the French national meteorological office (MétéoFrance) over the same period. Two hundred and six patients with spontaneous type A AADs underwent surgery during this period. The incidence of aortic dissection was higher in winter time than in summer (P=0.018). The days with aortic dissections were colder than those without aortic dissections (P=0.017). Statistical analysis highlighted a decrease of atmospheric temperature during the three days preceding the upset of the symptoms (P=0.0009). This work demonstrates a correlation between spontaneous type A AADs and low atmospheric temperature.

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Impact of meteorological conditions on the occurrence of acute type A aortic dissections

Vincent Benouaich 0 3 Pauline Soler 0 1 Pierre Antoine Gourraud 0 1 Stephane Lopez 0 3 Herve Rousseau 0 2 Bertrand Marcheix 0 3 0 The medical records of the patients operated on for Stanford's type A AAD in our department (Department of Cardiovascular Surgery, Rangueil University Hospital , Tou- louse, France ) between January 1997 and December 2007 were reviewed retrospectively. The date of the first symp- toms and the place where the patients were at that moment were precisely specified. This study was approved by the French National Institute for Medical Research (INSERM) Ethics Committee 1 Department of Epidemiology and Biostatistics, University Hospital , Toulouse, France 2 Department of Interventional Radiology, Toulouse Aortic Centre, Rangueil University Hospital , 1, Avenue Jean Poulhes, TSA 50032, 31059 Toulouse, Cedex 9, France 3 Department of Thoracic and Cardiovascular Surgery, Toulouse Aortic Centre, Rangueil University Hospital , 1, Avenue Jean Poulhes, TSA 50032, 31059 Toulouse, Cedex 9, France The impact of meteorological conditions on the occurrence of various cardiovascular events has been reported. The aim of this work was to study the correlations between weather conditions and the occurrence of type A acute aortic dissections (AADs). Between 1997 and 2007, all the medical records of patients who underwent surgery for type A AADs in Toulouse University Hospital (France) were reviewed. The clinical data were confronted with the meteorological data provided by the French national meteorological office (MeteoFrance) over the same period. Two hundred and six patients with spontaneous type A AADs underwent surgery during this period. The incidence of aortic dissection was higher in winter time than in summer (Ps0.018). The days with aortic dissections were colder than those without aortic dissections (Ps0.017). Statistical analysis highlighted a decrease of atmospheric temperature during the three days preceding the upset of the symptoms (Ps0.0009). This work demonstrates a correlation between spontaneous type A AADs and low atmospheric temperature. 2010 Published by European Association for Cardio-Thoracic Surgery. All rights reserved. 1. Introduction Acute aortic dissection (AAD) is the most common clinical catastrophe involving the aorta. The exact incidence of aortic dissection has been difficult to determine since many patients die without the correct diagnosis being made ante mortem. It was recently estimated that the incidence of AAD in an urban population in the south-eastern USA might be as high as 1020 cases per million population per year. Two-thirds of aortic dissections involve the ascending aorta. It is important to realize that the prevalence figures undoubtedly underestimate the real prevalence, since they do not consider patients who die suddenly from a complication of aortic dissection who are presumed to have succumbed to coronary disease or an arrhythmic event in the absence of post mortem examination. Some predisposing factors for AADs are well known, such as arterial hypertension, bicuspid aortic valve, coarctation of the aorta or Turners syndrome w1x. Patients with Marfans syndrome or other connective tissue disorders and pregnant women are other predisposing factors for AAD. *Corresponding author. Tel.: q33 561-322-652; fax: q33 561-322-315. E-mail address: (V. Benouaich). 2010 Published by European Association for Cardio-Thoracic Surgery Some studies highlighted the influence of environmental factors on the incidence of cardiovascular events, such as rupture of abdominal aorta, acute myocardial infarction, intracranial aneurysm rupture and sudden death. The influence of meteorological conditions on the occurrence of AAD has not specifically been reported. A winter increase of AADs onset has been reported by several authors w2, 3x, but no direct correlation between AAD and weather conditions has been proved so far in the English literature w4x. The aim of this work was to seek correlations between weather conditions and the occurrence of AAD. 2. Patients and methods 2.1. Patients V. Benouaich et al. / Interactive CardioVascular and Thoracic Surgery 10 (2010) 403407 2.2. Meteorological data The study was carried on the all Midi Pyrenees area (south-western of France). The climate of this area is an oceanic mesothermal mild climate. The mean daily temperatures range between 2 8C and 10 8C in winter, and between 16 8C and 26 8C in summer, accompanied with precipitations all the year round. The wind blows between 230 and 280 daysyyear and Foehns wind blows about 40 daysyyear. The weather data were provided by the French national weather office (MeteoFrance). For each day, the following parameters were assessed: daily precipitation, minimal, mean and maximal temperatures, minimal, mean and maximal atmospheric pressure, mean and maximum wind speed and wind direction, presence or absence of Foehns wind, minimal, mean and maximal relative humidity. These parameters were retrieved daily from 14 local weather stations, so that every patient could be matched precisely with the local weather conditions of the place where the first clinical symptoms appeared. 2.3. Statistical analysis All statistical studies were carried out in the Department of Epidemiology and Biostatistics of our University Hospital using the STATA-PC program version 10.0 for Windows PC (Stata Corporation, Texas, USA). The continuous variables were expressed as mean"standard deviation (S.D.). Nonparametric methods were used for all comparisons of meteorological parameters. Data were compared by the Wilcoxon signed-rank test. As 30 tests were performed, the Bonferroni correction was applied so that a value of P-0.05 was considered significant in all tests. 3. Results 3.1. Population From January 1997 to December 2007, 206 consecutive patients were operated on for type A AAD in our department. There were 153 men (74.3%) and 53 women with a mean age at operation of 62.5"11.7 years. 3.2. Seasonal, monthly and weekly variation in symptom onset The seasonal, monthly and daily variations of onsets of AAD symptoms are presented in Figs. 1, 2 and 3, respectively. A significant variation of AADs symptoms onset was observed: the frequency of AAD was 1.58 times higher in winter than summer (Ps0.018). Furthermore, AAD onset was twice higher in January and February than in July and August (Ps0.029). The percentage of initial pain occurrence was 1.60 times higher in January and February than the rest of the year (Ps0.002). In contrast, AAD onset was likely to be 1.45 times lower in July and August than the rest of the year (Ps0.06). The daily distribution of AADs was not inhomogeneous in this study. Fig. 1. Seasonal distribution of AADs. The onset of AADs was higher in winter than in summer (Ps0.018). AAD, acute aortic dissection. *P-0.05. The statistical analysis did not show any significant sexratio variation between the different seasons. 3.3. Weather conditions on the day of AAD The differences of meteorological conditions between the days of AAD and the days without AAD are resumed in Table 1. The minimum, mean and maximal atmospheric temperatures were lower on the days of AAD than the days without AAD (respectively, Ps0.02, Ps0.002 and P-0.001). No precipitation, wind, atmospheric pressure nor relative humidity variation was highlighted between the days with AAD and the days without AAD. 3.4. Weather variations during the days preceding AADs The variations of atmospheric temperatures during the five days preceding AADs are resumed in Table 2. For each patient, the minimal, mean and maximal atmospheric temperatures were retrieved from the local meteorological station on AAD day and compared with the data from the same meteorological station during the five preceding days. Statistical analysis highlighted a highly significant decrease Fig. 2. Monthly distribution of AADs. AADs onset in January and February was higher than in July and August (Ps0.029). AAD, acute aortic dissection. *P-0.05. V. Benouaich et al. / Interactive CardioVascular and Thoracic Surgery 10 (2010) 403407 Fig. 3. Daily distribution of AADs. AAD, acute aortic dissection. Atmospheric parameters Days with AAD Days without AAD P-value Precipitation (mm) 1.69 (3.84) Minimal temperature (8C) 7.20 (6.62) Mean temperature (8C) 11.47 (7.00) Maximal temperature (8C) 16.46 (8.00) Atmospheric pressure (hPa) 1018.8 (7.7) Wind presence 70.4% Foehns wind presence 13.5% Maximal wind speed (m.s1) 10.4 (4.4) Minimal relative humidity (%) 54.0 (15.8) Mean relative humidity (%) 77.7 (11.1) Maximal relative humidity (%) 93.8 (6.0) Results are presented as mean (S.D.) or %. AAD, acute aortic dissection; S.D., standard deviation. Bold values: P-0.05. of minimal, mean and maximal temperature between the third day before AAD and the AAD day. 4. Discussion Many studies highlighted correlations between environmental conditions and adverse cardiovascular events especially concerning the onset of myocardial infarction, sudden death and intracranial aneurysm rupture. Weather conditions are also correlated to variations of the incidence of some cardiovascular events: the onset of myocardial infarction is higher when the weather is cold and abdominal aortic aneurysm rupture is associated with low atmospheric pressure. The aim of this work was to seek a correlation between meteorological conditions and the onset of AAD. Various studies recently highlighted that the incidence of AAD has chronobiological variations. In 1997, Gallerani et al. w2x reported that AADs incidence is higher in the morning hours around 10:00 h, with a second peak around 20:00 h. In 2002, Mehta et al. w3x proved that AADs incidence is significantly higher in the morning and in winter, using data from the International Registry of Acute Dissection (IRAD). In 2005, Mehta et al. w5x reported that the outcome of AADs seems to be similar during the different periods of the day and during the four seasons. Our results confirm that AADs incidence has monthly and seasonal variations in south-western France. In 1999, Ohara et al. w6x suggested that the higher incidence of AADs in winter may be influenced by weather conditions. Those chronobiological patterns were confirmed by authors from other parts of the world with various climates, such as Japan w7x, Turkey w8x or Serbia and Montenegro w9x. In 2005, using data from patients enrolled around the globe in the IRAD, Mehta et al. w10x reported that the winter peak was evident in both cold and temperate climate settings, suggesting that the relative change in temperature, rather than absolute temperature may be a mechanistic factor. To our knowledge, only one report studying the direct influence of meteorological factors on AADs incidence has been published so far in the English literature w4x. This study did not show any link between weather conditions and AADs incidence, but very few patients were included in this case series. In the present work, we demonstrated for the first time a correlation between AADs incidence and decreased atmospheric temperatures, regardless of the time of the year. The decrease of temperature during the days preceding AADs suggests that relative change in temperature is a mechanistic factor rather than absolute temperature, which is consistent with Mehtas study from the IRAD w10x. No significant correlation was found between AADs and the other studied weather parameters. In this retrospective single-centre case series, the patients included were matched with the local weather condition, so that the results were relevant. Another limit of this study was that because of the social organization of France, a large proportion of people are on leave for holidays during the months of July and August. However, southwestern France is a popular touristic destination and the Atmospheric temperature V. Benouaich et al. / Interactive CardioVascular and Thoracic Surgery 10 (2010) 403407 global number of people in the studied area was almost constant throughout the year. The influence of atmospheric temperature on the AADs incidence may be explained by an increase in sympathetic activity, which is responsible for higher blood pressure, and heart rate. AADs result from the association of various factors, among which hypertension plays a key role as a predisposing factor, and as a trigger factor. In 1961, Rose reported that arterial blood pressure is higher in winter than in summer w11x. In 1982, Brennan et al. showed that the winter blood pressure increase could be observed in large samples of patients with high blood pressure, as well in treated as in untreated subgroups w12x. In 1978, Heller et al. proved that this winter increase of blood pressure was correlated with low atmospheric temperature w13x. In experimental patterns, when subjects are exposed to cold, their blood pressure and their heart rate increase via a sympathetic adrenergic pathway w14, 15x. Taken together with these data, the present study suggests a link between cold, high blood pressure and AADs winter peak of incidence, by the mean of sympathetic stimulation. Various studies demonstrated daily variations of AADs onset with a peak in the morning hours w3, 9x. Blood pressure is also higher in morning hours. Morning hours are also the coldest hours of days, suggesting a link between high blood pressure, adverse cardiovascular events and cold atmospheric temperature. Moreover, during summer months, many people are on holidays and their psychological and physical stress is reduced. This could perhaps be an additional factor to the meteorological changes associated with the prevalence of AADs. 5. Conclusion Environmental factors play a trigger role in the onset of AAD. Among these factors, cold weather and temperature decrease are correlated to an increase of the incidence of AAD. These correlations may result from an adrenergicmediated increase of blood pressure due to cold. Further experimental studies would be necessary to assess this hypothesis. Acknowledgments To Mr. Pierre Larrey and MeteoFrance for weather data supply and friendly advice. eComment: Meteorological conditions and acute cardiovascular events; is there any correlation? Authors: Nikolaos G. Baikoussis, Department of Cardiothoracic Surgery, University of Patras, School of Medicine, Patras, Greece; Efstratios E. Apostolakis, Ioanna Koniari, Dimitrios Dougenis doi:10.1510/icvts.2009.219873A We read with great interest the recent report by Dr. Benouaich and colleagues and we would like to congratulate them for their interesting results w1x. We think also that the study of Dr. Benouaich et al. offers useful information on this topic and we would like to comment on this article. The authors aim was to study the correlations between weather conditions and the occurrence of type A acute aortic dissections (AAD); the most common catastrophic disease of the aorta. Many authors have studied the impact of the temperature on the cardiovascular system (coronary arteries, aorta, bioprosthetic heart valve hemorrhage/thrombosis, etc.), because they are of the opinion that events are more frequent in certain seasons. Bhaskaran et al. who have studied the influence of the meteorological conditions on the coronary arteries suggested that both hot and cold weather had detrimental effects on the risk of myocardial infarction. However, further studies are necessary to determine the magnitude of these effects and to demonstrate which patients are vulnerable w2x. Not well known is the pathogenetic mechanism through which the temperature and the weather in general affect the cardiovascular system. Thrombogenicity of blood is known to have seasonal variations. Narang et al. w3x conducted a study on the hemorrhage or thrombosis in patients with mechanical heart valves in various seasons. They found that the number of patients with prolonged international normalized ratio (INR) and the incidence of hemorrhagic events peaked in hottest months of the year. The number of patients with rapid clotting and the incidence of embolic events peaked in coldest seasons of the year. They found also a significant correlation between temperature and thrombogenicity in patients with prosthetic heart valves on long-term anticoagulation w3x. Other authors w4x investigated whether presentation of AAD has seasonal variations. The frequency of AAD was found to be significantly higher during winter vs. other seasons. A relatively high positive correlation was found between the incidence of AAD and the mean atmospheric pressure w4x, while another study conducted in the UK for six years found no correlation between temperature or atmospheric pressure and the incidence of AAD w5x. In our opinion, the abrupt changes of the temperature and atmospheric pressure or the extreme cold or hot conditions have an impact on the vessels wall and on the blood viscosity. New, documented studies are needed to determine the precise mechanism of seasonal variation on the cardiovascular system. References eComment: Influence of meteorological conditions on the onset of acute type A aortic dissection Author: Frank Edwin, Walter Sisulu Pediatric Cardiac Center for Africa, Sunninghill Hospital, Johannesburg, South Africa doi:10.1510/icvts.2009.219873B The report of Benouaich et al. w1x highlights the factors responsible for the onset of acute aortic dissections (AAD). The pathogenesis of AAD is a result of the interplay of three factors: a predisposition provided by an abnormality or weakening of the aortic media, an agent of intimal injury or tear resulting in the intimomedial flap, and hemodynamic factors that propagate the dissection once it has been initiated. Predisposing factors must be differentiated from precipitating factors of AAD w2x. Precipitating factors act on the basis of a transient hypertensive reaction to trigger the onset of AAD in the predisposed aorta. From the report of Benouaich et al. w1x, a relative decrease in environmental temperature is clearly a precipitating factor of AAD. Another significant point in their study deserves attention. The mean age of the patients studied was 62.5"11.7 years. It is the opinion of this author that age is significant in this context as meteorological conditions induce a more pronounced effect on the cardiovascular system of the aged than the young. Hess and colleagues w3x studied the pressor responses to superficial skin cooling in young (25 years old) and elderly (65 years old) subjects. They found that superficial skin cooling elicited an increase in blood pressure from resting levels (P-0.05) in both groups. However, the magnitude of this pressor response (systolic and mean blood pressure) was more than two-fold higher in older adults (P-0.05 vs. younger adults). The aortic pulse wave velocity, a measure of central arterial stiffness obtained before cooling, was found to be the best predictor of the increased pressor response to superficial skin cooling in older adults. Older adults are therefore more susceptible to the influence of the meteorological changes on the onset of AAD. References


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Vincent Benouaich, Pauline Soler, Pierre Antoine Gourraud, Stéphane Lopez, Hervé Rousseau, Bertrand Marcheix. Impact of meteorological conditions on the occurrence of acute type A aortic dissections, Interactive CardioVascular and Thoracic Surgery, 2010, 403-406, DOI: 10.1510/icvts.2009.219873