Distribution of ABO Blood Groups among Patients with Congenital Heart Defects

With major advances in medical care during the past decades, the number of patients with congenital heart disease (CHD) who survive into adulthood is increasing [1, 2]. Moreover, CHD patients suffer from cardiovascular complications due to structural defects as they live longer than ever before [3, 4]. As a mainstay of treatment, most patients with CHD undergo surgical correction by their early adulthood [1]. Identifying predictors of more desirable outcomes and stratifying risk factors for poorer prognosis would help in better management of treatment options [5]. Several factors have contributed to the clinical progress and outcomes of patients with CHD [1, 3, 4]. ABO blood groups have recently been reported to play a role in some cardiovascular diseases [6-9]. Several studies have investigated the relationship between CHD and blood types, but the results are yet inconclusive [10-12]. Our study, therefore, aimed to examine the distribution of ABO blood groups among patients with CHD who were admitted for surgical repair and to investigate ABO blood group association with patients’ in-hospital outcomes such as renal failure, cerebrovascular accidents (CVA), myocardial infarction and mortality.

This study was approved by the ethics committee of our hospital and conducted in accordance with the tenets of the Declaration of Helsinki. In a retrospective study of data registry of our hospital, medical profiles of 34,239 admitted patients between January 2003 and December 2012 were reviewed to identify cases with CHD that had undergone surgical repair. Medical history, laboratory test results including ABO blood groups, and early in-hospital outcomes such as renal failure, cerebrovascular accidents (CVA), myocardial infarction and mortality were collected for each patient. Distribution of ABO blood groups was determined according to the CHD types and then clinical and laboratory variables were compared between different ABO blood groups. Data were analyzed using Statistical Package for Social Sciences (SPSS, version 16, Chicago, Inc, US). One-way analysis of variance (ANOVA) was used for comparison of continuous variables between ABO blood groups and chi square or Fisher’s exact test for cross-tabulation of categorical variables. Data was presented as mean ± SD and number (%) where appropriate and values were considered statistically significant at p <0.05.

During the study period, 1,155 patients, 554 males (48%), mean ± SD age was 42.2 ± 19.9 years, underwent surgical repair for CHD. The study population consisted of 379 patients with blood group A (32.8%), 269 patients with blood group B (23.3%), 79 with blood group AB (6.8%), and 428 blood group O (37.1%). Moreover, 1019 patients (88.2%) were Rh⁺ and 136 patients (11.8%) Rh^–. There was no significant difference between 4 blood ABO and 2 RH blood groups for primary characteristics (Table 1; p>0.05) Isolated atrial septal defect (ASD) constituted the most frequent type of CHD with 699 cases (60.5%), followed by isolated patent foramen ovale (PFO) (N= 154; 13.3%), isolated ventricular septal defect (VSD) (N=109; 9.4%), 34 (3.9%) isolated patent ductus arteriosus (PDA), 18 (1.6%) isolated tetralogy of Fallot (TOF), 17 (1.5%) isolated Coarctation of aorta, and 6 (0.5%) isolated transposition of great arteries (TGA), etc. However, the different distribution pattern of ABO and RH blood groups among CHD types did not reveal a statistically significant difference (p=0.25 and p=0.54, respectively). There was no statistical significant difference in terms of major clinical incidents or final outcomes in favor of any blood subgroup after adjusting for multiple comparisons. Ten patients (0.9%) in blood group A, 7 patients (0.6%) in blood group B, 2 patients (0.17%) in blood group AB, and 9 patients (0.8%) in blood group O died in hospital (Table 1).

 Although a relationship between blood group type and CHD has been proposed, we did not find such a relationship in a large dataset from our hospital. The possible role of blood groups in congenital heart diseases was first proposed by Lev et al. in 1967 [11]. They studied 130 African children free of CHD and 68 patients with CHD and compared them with normal population from the standpoint of ABO, RH, and MN system. They proposed that the incidence of type B of ABO blood group and CC Dee subtype of Rh⁺ blood group may be higher in patients with CHD. Moreover, the authors excluded any relationship between maternal-fetal blood group incompatibility and CHD. In contrast, we determined the distribution of blood groups among different CHD types and investigated patients clinical and final outcomes across these blood groups. In regard to our findings, blood group O had a higher prevalence among patients with ASD, VSD and PFO.  According to our country blood transfusion organization report, blood group O predominates in the general population of the country with a prevalence of 37.6%, followed by blood group A (30.2%), blood group B (24.4%), and blood group AB (7.8%) [6]. A similar distribution pattern was also seen in our study population with blood group O as the most predominant one (37.1%), followed by blood group A (32.8%), group B (23.3%), and group AB (6.8%). This suggests that there is likely no relationship between blood groups and CHD incidence. However, a definite conclusion can be made only when the prevalence of ABO blood groups types is compared with a sample of normal population. Although the retrospective design is a limitation of the current study, its large sample size is strength.

In conclusion, our study did not reveal any significant association between ABO and Rh blood groups and different types of congenital heart diseases and patients’ outcome.

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