Blood groups and acute aortic dissection type III.

INTRODUCTION: Acute aortic type III dissection is one of the most catastrophic events, with in-hospital mortality ranging between 10% and 12%. The majority of patients are treated medically, but complicated dissections, which represent 15% to 20% of cases, require surgical or thoracic endovascular aortic repair (TEVAR). For the best outcomes adequate blood transfusion support is required. Interest in the relationship between blood type and vascular disease has been established. The aim of our study is to evaluate distribution of blood groups among patients with acute aortic type III dissection and to identify any kind of relationship between blood type and patient's survival.
MATERIAL AND METHODS: From January 2005 to December 2014, 115 patients with acute aortic type III dissection were enrolled at the Clinic of Vascular and Endovascular Surgery in Belgrade, Serbia and retrospectively analyzed. Patients were separated into two groups. The examination group consisted of patients with a lethal outcome, and the control group consisted of patients who survived.
RESULTS: The analysis of the blood groups and RhD typing between groups did not reveal a statistically significant difference (p = 0.220).
CONCLUSIONS: Our results indicated no difference between different blood groups and RhD typing with respect to in-hospital mortality of patients with acute aortic dissection type III.

Introduction

Acute aortic dissection is defined as the rapid development of a false, blood-filled channel within the tunica media of the aorta [1]. Approximately 2.9–3 out of 100,000 people per year are afflicted with acute aortic dissection [2, 3]. Aortic dissection type III accounts for 25% to 40% of all aortic dissections [4]. Acute aortic type III dissection (within 14 days of onset) is one of the most catastrophic events, with in-hospital mortality ranging between 10% and 12%. The majority of patients are treated medically, but complicated dissections, which represent 15% to 20% of cases, require surgical or thoracic endovascular aortic repair (TEVAR) [5]. For the best outcomes of these procedures, the surgical team requires adequate blood transfusion support. The IRAD study defined some of the factors influencing in-hospital mortality: increasing age, hypotension/shock, peri-aortic hematoma, descending aortic diameter > 55 mm, acute renal failure, and limb ischemia [6]. In order to improve our results and to lower in-hospital mortality, more parameters beyond those of clinical symptomatology need to be investigated. Interest in the relationship between blood type and vascular disease has been established [7-10].

Therefore, the purpose of this study was to evaluate the distribution of blood groups among patients with acute aortic type III dissection and to identify any kind of relationship between blood type and patient survival.

Material and methods

The design of our study is a retrospective case-control study. From January 2005 to the end of December 2014, 115 patients with acute aortic type III dissection were enrolled at the Clinic of Vascular and Endovascular Surgery in Belgrade, Serbia. The diagnosis was established based on the findings of multi-slice computed tomography (MSCT). Patients were classified in two groups. The examination group consisted of the patients with a lethal outcome, and the control group consisted of the patients who survived. ABO blood group with RhD typing was performed for each patient in both groups as a routine laboratory examination. Complete statistical data analysis was performed in a statistical computer program (PASW Statistics version 18).

Statistical analysis

All attribute variables were presented in the form of the frequency of certain categories, and statistical significance between the individual categories was tested by the χ2 test. All continuous variables are presented as mean values ± standard deviation. Student’s t-test was used for differences in continuous variables for independent samples.

Results

The study population included 86 men and 29 women with an average age of 63.1 ±9.9 years (range: 45–72 years). The overall mortality rate was 20.9% (24 patients). The examination group consisted of 24 patients with a lethal outcome, and the control group consisted of 91 patients who survived. The analysis of the subjects by gender concluded that both groups consisted mostly of male subjects (91.7% for the examination group and 70.3% for the controls). Comparing the groups by gender, the χ2 test did not reveal a significant difference (p = 0.054). The age distribution of the examination group was 55.65 ±9.75, and the age distribution of the control group was 60.26 ±11.81. The patients with a lethal outcome were slightly younger, but the Student t-test did not reveal a significant difference between groups (p = 0.123). Comparing the distribution of blood types among the groups (Table I), blood group A with positive RhD typing was the most frequent in the examination group (45.8%), while blood group O with positive RhD typing was the most frequent among the controls (39.5%). The χ2 test did not reveal a significant difference between the distributions of blood types among the groups (p = 0.220).

Table I

Demographic characteristics, blood groups and RhD typing distribution

Variable	Outcome		P-value
	Lethal	Survival
Number of patients (%)	24 (20.9%)	91 (79.1%)
Gender:
Male	22 (91.7%)	64 (70.3%)	0.032*
Female	2 (8.3%)	27 (29.7%)
Age, mean ± SD [years]	55.65 ±9.75	60.26 ±11.81	0.123**
Blood group:
O–	3 (12.5%)	7 (7.7%)	0.220*
O+	7 (29.2%)	36 (39.5%)
A–	–	5 (5.5%)
A+	11 (45.8%)	22 (24.2%)
B–	2 (8.3%)	4 (4.4%)
B+	–	9 (9.9%)
AB–	–	4 (4.4%)
AB+	1 (4.2%)	4 (4.4%)

Discussion

The purpose of this study was to evaluate the distribution of blood groups among the patients with acute aortic type III dissection, to identify any kind of relationship between blood type and patient survival, and to obtain information that can be useful for the transfusion department in case they encounter patients with acute aortic type III dissection. The association of blood groups with vascular disease has been proposed for a long time [11-13]. In the Serbian population, the most frequent blood group is A with 42% followed by blood group O with 38% [13]. Our study demonstrated that blood group O was the most frequent among the study population (46.07%). ABO blood groups and AAA have also been related in some studies. Viklander et al. [14] investigated 504 patients who required an operation because of AAA. They did not find any difference in the distribution of the ABO blood types in the operated patients and the common population based control group. Furthermore, there was no significant difference in distribution of ABO blood groups between patients. The number of patients who required an operation for ruptured AAA was 174 and for non-ruptured AAA 330. This study failed to demonstrate an association between ABO blood groups and AAA. Frequencies of blood groups (ABO, RhD, MNSs, P, Kell, Lewis and Duffy) and HLA antigens were studied in a series of patients from northern Sweden with AAA. Significant differences from the controls were found: a decreased frequency of the Rh-negative blood group and an increased frequency of the Kell-positive and MN blood groups [15-17]. Some previous examinations also demonstrated that blood type O can be an indicator for AAA [18]. Further study should determine whether blood type O is an indicator for acute aortic dissection type III. Despite advances in the management of acute aortic type III dissection, the in-hospital mortality rate remains considerable (about 13%) [5]. The overall mortality rate in our study was 20.9%. A definitive list of predictors for in-hospital mortality has not yet been established [6]. Acute aortic dissection almost never developed on the preserved aortic wall. The main reason for the destruction of the aortic wall is an atherosclerotic process in older patients. A previous study demonstrated that patients with non-O blood types are more likely to suffer from arteriosclerosis [19]. In order to improve our results and to lower in-hospital mortality, more parameters need to be investigated. Comparing the distribution of blood types among the groups (Table I), blood group A with positive RhD typing was the most frequent in the examination group (45.8%), while blood group O with positive RhD typing was the most frequent among the controls (39.5%). The χ2 test did not demonstrate a significant difference between the distributions of blood types among the groups (p = 0.208). This led us to conclude that the blood group and the RhD typing cannot be an indicator for in-hospital mortality in patients with acute aortic dissection type III. Complicated dissections represent 10% to 20% of all cases [5, 20]. Since the risk factors for developing a complication are not currently well described, all of these patients should be considered as potentially complicated cases that can require surgical or TEVAR [5, 20]. In these cases transfusion support plays an important role. Previous studies primarily investigated the influence of bleeding complications and acute aortic dissection type I and II as the leading causes of death for these patients [20-24]. Furthermore, blood transfusion is associated with increased morbidity and mortality [25-30]. Our study demonstrated that blood groups O and A with positive RhD typing are the most frequent in the cohort population (Table I). This information showed that the existing strategy of preparing transfusion units and blood products for blood groups A and O with positive RhD typing for every patient accessing the ER is quite adequate even for these patients.

In conclusion, in the Serbian population, the most frequent blood group is A with 42% followed by blood group O with 38% [13]. Our study demonstrated that blood group O was the most frequent among the study population. Blood group A with positive RhD typing was the most frequent in the examination group (45.8%), while blood group O with positive RhD typing was the most frequent among the controls (39.5%). The χ2 test did not demonstrate a significant difference between the distributions of blood types among the groups (p = 0.208). Our results indicated no difference between different blood groups and RhD typing with respect to in-hospital mortality of patients with acute aortic dissection type III.