Sumario Vol.43 - Nº 3 Julio-Septiembre 2014 Imprimir sólo la columna central

Screening of Abdominal Aortic Aneurysm
in the Department of Cardiology

Delicia I. Gentille Lorente, Teresa Salvadó Usach

Servicio de Cardiología, Hospital de Tortosa Verge de la Cinta. IISPV
(43500) Tortosa, Tarragona, España.
E-mail
 
Recibido 17-MAR-2014 – ACEPTADO después de revisión el 02-MAYO-2014.
The authors declare not having conflicts of interest
 
Rev Fed Arg Cardiol. 2014; 43(3): 130-140
ABSTRACT

The growing incidence of abdominal aortic aneurysm and the related mortality of 85-90% in the case of rupture justify early diagnosis and repair.
Methods: A total of 668 consecutive patients were evaluated by transthoracic echocardiography in the Department of Cardiology, independently from the indication.
Results: An abdominal aortic aneurysm was detected in 28 patients (4.2%), with a mean age of 71.8 ± 8.0 years, 92.9% of whom were males with a mean aneurysm diameter of 37.6 ± 10.5 mm. The detected risk factors of aneurysm were being a smoker or ex-smoker, age, presence of femoral murmur and greater dimensions of the suprarenal aorta and aortic arch.
Conclusions: The use of conventional echocardiography for the study of infrarenal aorta (paraumbilical access) is feasible and useful for the screening of the abdominal aortic aneurysm in patients attended in the Department of Cardiology. This screening should mainly be performed in patients with a high risk of developing an aneurysm such as in patients ³55 years of age or with ≥1 risk factors.
Key words: Abdominal aortic aneurysm. Aorta. Aneurysm. Echocardiography. Screening.

 

INTRODUCTION
Abdominal aortic aneurysm (AAA) is the dilatation of the infrarenal aorta, which is affected in 95% of cases, ≥3 cm of diameter [1-3]. Its incidence is mainly increased by the population aging [1,3,4], being 1.5-2% in adults [3] (6-7% in people older than 60 years).

Its pathogenesis is uncertain, but most AAA are related to arteriosclerotic heart disease [5]. Most constitute an incidental finding in imaging tests but, among its complications, rupture leads to a total mortality of 85-90% [1,2,6,7], representing 1-2% of total mortality in the Western world [6-8]. The main vascular scientific societies recommend performing AAA screening by abdominal echo in the risk populations, although in clinical practice it is not made.

Different previous studies showed the usefulness of transthoracic echo (TTE) to detect AAA; however; the only access advised by the main societies of echocardiography [9-11] to assess the abdominal aorta is the subcostal access, which allows visualizing its proximal or suprarenal segment and not the infrarenal one, which is the one affected in nearly all cases.

Some years ago, a cardiology study was started to evaluate the validity of TTE as a screening method for AAA in our patients, the initial results of which were reported to this journal [12]; next, we present the results after enhancing the series.

 

METHODS

1. Design of the study
A cross-sectional, observational, descriptive study was designed, with an analytic component. There were 687 consecutive patients studied (410 males and 277 females) were referred to the cardiology service to undergo TTE, independently from the indication of the test and with no known history of AAA.

2. Recorded variables
The variables in the study were collected by the only cardiologist in the study from the clinical, in-hospital and ambulatory story of the patient, the anamnesis and the vascular exploration made before the TTE.

3. Echocardiographic study
The TTE were made by a single cardiologist to prevent the interobserver variations reported, using a Vivid Five ultrasound machine of General Electrics, with cardiological software, 2.5 MHz transducer and second harmonic.
The aorta was measured by online electronic calipers and the image stopped in systole, from the anterior border to the anterior border following a plane perpendicular to the longitudinal axis of the artery, recording the maximal diameter obtained. The infrarenal aorta was visualized in its maximal extension possible with 2D image and from a left paraumbilical plane (patient in a supine position), or else, right paraumbilical plane (patient in left lateral semi-decubitus); after determining its antero-posterior and transversaldiameters, the maximum obtained was recorded.
It was considered that there was AAA if the infrarenal diameter was ≥30 mm. Also, the presence of infrarenal atherosclerosis was recorded, considering it as severe if the atheromatous plaques were ≥5 mm of thickness, mural thrombosis and infrarenal aortic dissection. To confirm the finding of AAA in TTE, an abdominal echo was scheduled, or else, abdominal CT within 6 months.

4. Statistical analysis
A descriptive study was made initially by the statistical package SPSS 16.0. The quantitative variables are expressed as mean and standard deviation (±SD); the relation between a quantitative and a qualitative variable with equal variances was studied by student’s t-test, and in the case of different variances, by Mann-Whitney U test. The results of the qualitative variables were expressed in number and percentage and compared by the χ2 test, or according to the sample size, by Fisher’s exact test. Subsequently, an univariate and multivariate analysis was performed by logistic regression. The statistical significance was established as P<0.05.

 

RESULTS

1. Visualization of infrarenal aorta
When determining the intraobserver variability of the cardiologists participating in the study when measuring infrarenal aorta, an intraclass correlation coefficient of 0.99 was obtained.
There were 687 patients studied, with the infrarenal aorta not being visible in 19 cases, so that eventually 668 patients were included (97.2%), 399 males (59.7%) and 269 women (40.3%), with an age range of 16 to 89 years. There was no relation detected between body mass index (BMI) or gender with the success in visualization (P=0.83 and P=1.000, respectively). In general, this infrarenal study lasted ≤3 minutes.

2. Characteristics and history of the patients
Table 1 shows the characteristics and main history of patients, overall and whether AAA was detected or not.

Table 1. Basic characteristics, cardiovascular risk factors and history of arteriosclerotic disease

 

Total No AAA With AAA P*
  Gender        
  • Males
  • Females
399 (59.7)
269 (40.3)
373 (58.3)
267 (41.7)
26 (92.9)
2 (7.1)
<0.0001
   Age (years) 64.6 ± 13.1 64.2 ± 13.3 71.8 ± 8.0 0.003
  HTN 464 (69.3) 442 (69.3) 22 (78.6) 0.295
  Dyslipidemia 433 (65.0) 413 (64.7) 20 (71.4) 0.467
  Diabetes Mellitus 185 (27.8) 174 (27.3) 11 (39.3) 0.167
  BMI (kg/m2) 28.7 ± 4.8 28.7 ± 4.8 27.5 ± 3.6 0.218
  Chronic renal failure 97 (14.6) 91 (14.3) 6 (21.4) 0.279
  Tobacco        
  • Non smokers
  • Smokers
  • Former smokers
382 (57.2)
113 (16.9)
173 (25.9)
376 (58.8)
105 (16.4)
159 (24.8)
6 (21.4)
8 (28.6)
14 (50.0)
<0.0001
  ECG: Cardiac rhythm        
  • Sinus
  • Atrial fibrillation
  • Others
551 (82.7)
110 (16.5)
5 (0.8)
530 (83.1)
103 (16.1)
5 (0.8)
21 (75.0)
7 (25.0)
0 (0.0)
0.168
  Ischemic heart disease        
  • No
  • Asymptomatic
  • Angor
  • MI

458 (68.9)
14 (2.1)
81 (12.1)
113 (17.0)

444 (69.7)
13 (2.0)
77 (12.1)
104 (16.3)

14 (50.0)
1 (3.1)
4 (14.3)
9 (32.1)

0.028
0.455
0.765
0.039

  Coronary angiography        
  • Normal
  • Non-significant lesions
  • Significant lesions
13 (7.5)
35 (20.2)
125 (72.3)
13 (8.0)
35 (21.6)
114 (70.4)
0 (0.0)
0 (0.0)
11 (100)
n.a.
  Cerebrovascular disease        
  • No
  • TIA
  • Ictus
598 (89.7)
18 (2.7)
51 (7.6)
571 (89.4)
18 (2.8)
50 (7.8)
27 (96.4)
0 (0.0)
1 (3.6)
0.346
1.000
0.715
  Peripheral vascular disease        
  • No
  • Femoral murmur
  • Intermittent claudication
  • Absence of distal pulses or anomalous ankle-brachial index
489 (74.9)
89 (13.6)
23 (3.4)
113 (17.3)
478 (76.5)
77 (12.3)
20 (3.1)
99 (15.8)
11 (39.3)
12 (42.9)
3 (10.7)
14 (50.0)
<0.0001
<0.0001
0.067
<0.0001
  Abdominal exploration        
  • Abdominal mass or murmur
24 (3.7) 18 (2.9) 6 (21.4) <0.0001
  Blood analysis        
  • Basal glucose (mg/dl)
  • Hemoglobin (g/dl)
  • Hb A1C
  • Creatinine (mg/dl)
  • LDL-c (mg/dl)
  • HDL-c (mg/dl)
  • TG (mg/dl)
  • Renal function (MDRD-4)  
110.1 ± 33.5
13.9 ± 1.8
6.0 ± 1.8
1.0 ± 0.7
119.2 ± 35.7
42.8 ± 16.4
119.5 ± 79.5
82.7 ± 41.6
109.7 ± 33.8
13.9 ± 1.7
6.0 ± 1.9
1.0 ± 0.7
119.0 ± 35.7
42.9 ± 16.6
120.4 ± 81.1
83.9 ± 42.4
110.6 ± 20.9
14.3 ± 1.5
5.7 ± 1.3
1.1 ± 0.4
130.3 ± 31.2
39.8 ± 12.4
107.9 ± 52.7
79.4 ± 26.8
0.884
0.166
0.632
0.528
0.115
0.348
0.421
0.646
Results of the quantitative variables in ± SD and the qualitative variables in frequency and percentage

*Differences between the patients that present and do not present AAA. n.a.: not applicable and/or conditions are not met; AAA: abdominal aortic aneurysm; P: degree of significance; HTN: hypertension; BMI: body mass index; ECG: electrocardiogram; MI: myocardial infarction; TIA: transient ischemic accident; HbA1C: glycosylated hemoglobin; LDL-c: cholesterol bound to low-density lipoproteins; HDL-c: cholesterol bound to high-density lipoproteins; TG: Triglycerides.

 

3. Echocardiographic study
To the conventional echocardiographic study (Table 2), a final aorta study was added, with AAA being detected in 28 patients (prevalence of 4.2%). The mean age of the affected patients was 71.8±8.0 years. By gender, 26 cases (92.9%) were males from 55 to 82 years of age and 2 (7.1%) were females between 73 and 89 years, with a ratio of prevalence male:female of 9.3:1 (P<0.0001). Twenty seven cases (96.4%) were asymptomatic.

Table 2. Echocardiographic study

 

Total

No AAA

With AAA

P*

  LVEF 58.9 ± 11.9 59.1 ± 11.8 55.8 ± 13.4 0.169
  LVH 67 (10.3) 63 (10.1) 4 (15.4) 0.332
  E/A 1.0 ± 0.5 1.0 ± 0.5 0.8 ± 0.2 0.074
  Mitral DT (ms) 192.9 ± 50.7 192.3 ± 50.5 202.1 ± 48.2 0.393
  LVRT (ms) 89.1 ± 19.2 89.2 ± 18.7 95.5 ± 23.3 0.256
  E/e’ 11.3 ± 6.9 11.3 ± 7.0 9.6 ± 3.7 0.365
  Diastolic dysfunction      
0.336
  • Degrees 0 and I
  • Degrees II, III and IV
486 (85.4)
83 (14.6)
467 (85.1)
82 (14.9)
19 (95.0)
1 (5.0)
  LA dilatation      
0.557
  • No
  • Yes
369 (56.8)
281 (43.2)
352 (56.5)
271 (43.5)
17 (63.0)
10 (37.0)
  Aortic valve      
1.000
  • Normal tricuspid
  • Congenital anomaly
612 (98.1)
12 (1.9)
587 (98.0)
12 (2.0)
25 (100.0)
0 (0.0)

  Aortic valve sclerosis

     
1.000
  • No and not severe
  • Severe
613 (98.4)
10 (1.6)
587 (98.3)
10 (1.7)
26 (100.0)
0 (0.0)
  Mitral annulus calcification      
1.000
  • No and not severe
  • Severe
637 (98.6)
9 (1.4)
611 (98.5)
9 (1.5)
26 (100.0)
0 (0.0)
Results of the quantitative variables in ± SD and of qualitative variables in frequency and percentage

*Differences between the patients that present and do not present AAA. AAA: abdominal aortic aneurysm; P: significance degree; LVEF: left ventricular ejection fraction; LVH: left ventricular hypertrophy; DT: mitral deceleration time; LVRT: left ventricular relaxation time; LA: left atrium.

The average diameter of aneurysms was 37.6±10.5 mm, with a range of 30 to 69 mm in males and 31 to 67 mm in women (Table 3) (Figure 1).

Table 3. Prevalence and dimensions of total AAA and by subsets

 

Total

Males

Females

M:F

P*

  All patients          
  • Nº of cases
  • Age (years)
  • AAA diameter (mm)
28 (4.2)
71.8± 8.0
37.6±10.5
26 (6.5)
71.1 ± 7.5
36.7± 9.1
2 (0.7)
81.0 ± 1.3
49.0± 25.4
9.3:1

 

<0.0001
 
0.113
  Patients ≥ 55 years old          
  • Nº of cases
  • Age (years)
  • AAA diameter (mm)
28 (5.2)
71.8± 8.0
37.6±10.5
26 (8.1)
71.1 ± 7.5
36.7± 9.1
2 (0.9)
81.0 ± 1.3
49.0± 25.4
9:1 <0.0001
 
0.113
  Patients from 55 to 75   years          
  • Nº of cases
  • Age (years)
  • AAA diameter (mm)
18 (4.5)
67.4 ± 6.1
34.5 ± 6.8
17 (6.9)
67.1 ± 6.2
34.7 ± 6.9
1 (0.6)
73.0
31.0
11.5:1

 

<0.0001
 
0.611
  Patients > 60 years old          
  • Nº of cases
  • Age (years)
  • AAA diameter (mm)
25 (5.5)
73.5 ± 6.5
38.4 ± 0.9
23 (9.1)
72.9 ± 5.9
37.5 ± 9.4
2 (1.0)
81.0 ± 11.3
49.0 ± 25.4
9.1:1 <0.0001
 
0.733
  Patients from 65 to 75   years          
  • Nº of cases
  • Age (years)
  • AAA diameter (mm)
12 (5.2)
71.1 ± 3.1
34.9 ± 8.0
11 (8.2)
70.9 ± 3.2
35.3 ± 8.3
1 (1.1)
73.0
31.0
7.5:1 <0.0001
 
0.632
  Males from 65 to 75 years   old, smokers or former   smokers          
  • Nº of cases
  • Age (years)
  7 (9.5)
70.7 ± 3.6
 

 

 

Results of quantitative variables in ± SD and of qualitative variables in frequency and percentage

*Differences between males and females that present AAA. M:F: male:female ratio;
P:
degree of significance.

 

Figure 1. Correlation between age and infrarenal aorta dimensions in TTE


As to size, 23 (82.1%) were small (30-39 mm), 2 (7.1%) were average (40-54 mm) and 3 (10.7%) were large (≥55 mm); 25% of AAA presented severe infrarenal atherosclerosis, 17.9% mural thrombosis and 3.6% infrarenal dissection (Table 4).

Next, the prevalence of aneurysm and its dimensions in different subsets of patients evaluated in literature were analyzed (Table 3).

Table 4. Echocardiographic aortic study

 

Total

No  AAA

With AAA

P*

   Aortic dimensions        
  • Root (mm)
34.0 ± 4.7
(21-50)
34.0 ± 4.7
(21-50)
35.4 ± 4.1
(29-45)
0.111
  • Ascending aorta (mm)
34.0 ± 5.3
(20-58)
33.9 ± 5.3
(20-50)
35.2 ± 3.7
(28-45)
0.224
  • Arch (mm)
25.4 ± 3.8
(14-42)
25.2 ± 3.6
(14-41)
28.6 ± 5.1
(21-42)
0.001
  • Thoracic descending aorta (mm)
23.5 ± 3.1
(13-37)
23.4 ± 3.1
(13-37)
25.9 ± 2.9
(21-33)
<0.0001
  • Suprarenal aorta (mm)
20.2 ± 3.1
(10-31)
20.1 ± 3.0
(10-31)
23.3 ± 3.3
(17-29)
<0.0001
  • Infrarenal aorta (mm)
18.4 ± 5.6
(9-69)
17.5 ± 3.4
(9-28)
37.6 ± 10.5
(30-69)
 
  Infrarenal arteriosclerosis       <0.0001
  • No andnot severe
  • Severe
636 (96.2)
25 (3.8)
615 (97.2)
18 (2.8)
21 (75.0)
7 (25.0)
  Infrarenal thrombosis      

<0.0001

  • No
  • Yes
650 (98.8)
8 (1.2)
627 (99.5)
3 (0.5)
23 (82.1)
5 (17.9)
  Infrarenal dissection       <0.043
  • No
  • Yes
652 (99.8)
1 (0.2)
625 (100.0)
0 (0.0)
27 (96.4)
1 (3.6)
Results of the quantitative variables in ± SD (range) and of discrete variables in number and percentage

*Differences between males and females that present AAA. P: degree of significance


4. AAA risk factors
To detect the risk factors and situations associated to AAA initially, their relation to the variables in Tables 1, 2 and 4 were analyzed by bivariate analysis. In the aortic study, the datum that stood out was that aneurysm was related only, and with a positive correlation, with the dimension of the aortic arch, of the descending thoracic and suprarenal aorta (P<0.0001). There was no evidence of its association with the coronary angiography findings, but yes that 100% of the patients with AAA that had this exploration available presented significant coronary lesions (obstruction ≥50% of the left coronary trunk lumen or ≥60% of the lumen in the rest of the arteries), with the difference between the ratio of patients with and without AAA with such alterations being significant (P=0.036).

Later, univariate analysis was performed with all the variables (Tables 1, 2 and 4) and a multivariate analysis with those significantly associated to AAA (Tables 5 and 6).

Table 5. Univariate analysis. Odds ratio of significant variables in AAA

Variable

Reference

OR

CI 95%

P

  Age  (years) - 1.06 1.02-1.11 0.003
  Gender Female 9.30 2.19-39.54 0.003
  Smoker Non smoker 4.77 1.62-14.06 0.005
  Former smoker Non smoker 5.52 2.08-14.62 0.001
  MI No 2.42 1.07-5.51 0.034
  Femoral murmur No 5.37 2.44-11.77 <0.0001
  Absence of distal pulses or
  abnormal ankle-brachial   index
No 5.33 2.47-11.53 <0.0001
  Intermittent claudication No 3.72 1.04-13.35 0.044
  Peripheral vascular disease No 5.03 2.30-10.97 <0.0001
  Abdominal murmur or mass No 9.24 3.34-25.56 <0.0001
  Arch (mm) - 1.23 1.12-1.35 <0.0001
  Thoracic descending aorta   (mm) - 1.25 1.10-1.41 <0.0001
  Suprarenal aorta (mm) - 1.38 1.21-1.58 <0.0001
  Infrarenal arteriosclerosis No and
not severe
11.39 4.29-30.20 <0.0001
  Infrarenal thrombosis No 45.43 10.23-201.72 <0.0001
OR: odds ratio; CI: confidence interval; P: degree of significance; MI: myocardial infarction

 

Table 6. Multivariate analysis. Odds ratio of significant variables in AAA, adjusted by other variables

  Variable

Reference

OR

CI 95%

P

  Age  (years) - 1.10 1.03-1.17 0.003
  Smoker Non smoker 15.06 3.22-70.41 0.001
  Former smoker Non smoker 5.98 1.69-21.15 0.005
  Femoral murmur No 3.52 1.18-10.53 0.024
  Arch (mm) - 1.20 1.04-1.36 0.010
  Suprarenal aorta (mm) - 1.30 1.10-1.55 0.002
OR: odds ratio; CI: confidence interval; P: degree of significance

 

5. AAA risk index
From the multivariate analysis, a risk score for AAA was prepared, with the following considerations (Table 7):
a) The variables “age” and “suprarenal aorta dimensions” were included as categorical; the suprarenal aorta was considered dilated if it exceeded 20 mm.
b) The variable “dimensions of the arch” was not included because it was a segment hard to visualize and with less reproducibility.
c) The variables are assigned arbitrarily, and with practical purposes, a score of 0, 1 or 2, according to their OR.

Thus, the AAA-T risk index was prepared (Age, femoral murmur Auscultation, suprarenal Aorta, Tobacco smoking). Subsequently, a second index including only the clinical variables was prepared, so that physicians may estimate it during the medical visit of the patient: the AA-T index (Age, femoral murmur Auscultation, Tobacco smoking).

Table 7. AAA-T risk index

Variables

Categories

Score

 Age 55 - 65 years 1
> 65 years 2
 Tobacco Former smoker 1
Smoker 2
Femoral murmur Yes 1
Suprarenal aorta >20 mm 1
AAA RISK INDEX Maximal score 6

 

6. Correlation between TTE results and radiology explorations.
From the 28 AAA detected, 21 cases (75%) were confirmed by radiological tests (Figure 2); however, 4 AAA not confirmed by abdominal echo, did not have posterior abdominal CT that would confirm one result or the other, and 3 AAA, for different reasons, did not have any radiological exploration before 6 months.

Figure 2. Radiological studies performed in patients with AAA

From the 19 AAA studied by abdominal echo, this confirmed the aneurysm in 15 cases (78.9%) and with a positive correlation between the dimensions (rs =0.760; P=0.001); the correlation between the dimensions of AAA in TTE and those determined in the radiological explorations (echo or abdominal CT) was also good (rs =0.920; P<0.001).

 

DISCUSSION
These results show the feasibility and usefulness of supplementing the TTE with the infrarenal aorta study to make an AAA screening in the patients visited in cardiology; the prevalence in those of ≥55 years is of 5.2%. Additionally, the detection of an AAA leads us to suspect the existence of underlying coronary and peripheral arteriosclerotic disease that may condition the management of the patient.

1. Success in visualizing infrarenal aorta
Previous studies describe a visualization of the aorta even up to 95.7% of cases; in the current series it is discretely greater by using the left or right paraumbilical access (by the abdominal content interfering less); some authors consider that the obesity and abdominal distension [3,8,13] prevent studying it, but in the series, there is no proof that BMI or gender may condition such visualization [1,7,8].

2. Prevalence of AAA
Its true prevalence is underestimated, since its natural history consists of a progressive, slow and asymptomatic expansion during even 10 years. In the series, the minimal age at diagnosis is 55 years, with prevalence being 5.2% at ≥55 years; this is still 4.5% in the 55 to 75 years group, who are those considered as those most benefitted from the screening, since they are potentially the most apt to undergo surgery. In all ages, AAA affects males more and earlier, with the male:female ratio being 7.5-11.5:1, exceeding that reported in literature [5,14] (Table 3); however, there are no significant differences in size in regard to gender. It highlights that multivariate analysis does not show gender as a risk factor for aneurysm, which could be explained by the scant number of women with AAA, or because the scenario is different, more frequent in males, which in fact entails a risk factor for aneurysm, as it occurs for instance, with smoking. The main vascular societies involved in the management of AAA recommend screening by abdominal echo, in 65 to 75-year-old males that smoke or have smoked by estimating that such strategy may result cost-effective [15-17]. They are based on the main screening studies made, especially four randomized studies and on meta-analyses on them, which in general advise making a screening in males at such age, thus achieving a 43% decrease in mortality by AAA[18-24]. Recent guidelines from the European Society for Vascular Surgery advise performing screening in men older than 65 years old of populations with AAA prevalence of ≥4%, since it reduces mortality by aneurysm to a half in 4 years [17]; in turn, such guidelines question the convenience and cost-effectiveness of not performing screening in women and in males older than 75-80 years old, as well as the environment in which such study should be conducted [17].
When evaluating the potential impact of the current screening recommendations in the series, it is observed that they are very restrictive, since by studying males from 65 to 75 years of age that smoke or former smokers, only 7 aneurysms would have been diagnosed (11 if we include all males) (Table 3); i.e. only 26% of AAA in our population of patients. For this reason, based on the social reality of our environment, where smoking has increased in women, and there is a greater and better hope of life, we should pose enhancing the age range of aneurysm screening and extend it to the female gender. Additionally, in the case of the population visited in cardiology (in whom the prevalence of aneurysm exceeds 4%) and according to recent European guidelines [17], AAA screening would be proper. 

3. AAA risk factors
Numerous discrepancies are detected in regard to literature where, on the other hand, often determining the history is based on a set of questions asked to the patient, and in general, no multivariate analysis was made. A recent review and meta-analysis of 14 screening studies, performed by abdominal echo in people older than 60 years [24], concludes that the male gender, smoking and having a peripheral vascular or coronary disease are the main AAA risk factors, such results partially coincide with those from the current series where multivariate analysis does not show gender or ischemic heart disease as risk factors for aneurysm. As already described by other authors [5,6,19,24], no analysis has shown a relation between aneurysm and diabetes mellitus. Other classically described associations, although controversial, are AAA and HTN, dyslipidemia [5] and lipid levels (especially LDL cholesterol); in this paper such relations are not verified either, in any analysis modality. As to chronic renal failure, although it is an important cardiovascular risk factor and although AAA may be considered another manifestation of arteriosclerotic disease, an association between both is not shown (not considering creatinine levels in blood or glomerular filtration (MDRD-4)), a fact that Forsdahl et al [3], had already suggested.

4. AAA and other echocardiographic variables
The different composition and properties of the aortic wall, according to the segment, explains that the etiology of the aneurysms varies according to location. In fact, in the series, neither the aortic root or the ascending aorta dimensions, which are usually measured during TTE, nor the rest of the echocardiographic variables allow suspecting the existence of AAA, results that are in contrast with Bekkers et al [4], and Grosso et al [13].

5. AAA and arteriosclerotic disease
Often AAA and arteriosclerotic disease coexist in different vascular territories, and in fact, the American Heart Association considers AAA as an equivalent to ischemic heart disease. In this series, a certain relation between AAA and ischemic heart disease or peripheral vascular disease is detected, which is supported by some authors [5], and not by others [25], but is not associated to cerebral vascular disease as some describe in literature. Anyway, the prevalence of systemic arteriosclerosis in AAA is less than that reported; although there is a greater percentage of patients with AAA, who having undergone coronary angiography, present significant lesions (100% against the 36-46% described) [26]. As to infrarenal arteriosclerosis, in this study AAA does not appear as risk factor, so in agreement with other authors, there would be no dose-response relation between both, and other factors would be necessarily implied in its pathogenesis; the same thing occurs with infrarenal thrombosis.

6. Screening of AAA in cardiology
According to other authors [1,3], the abdominal physical examination does not allow detecting AAA, since 79% of the patients affected was normal. However, the presence of femoral murmur does entail the risk of suffering aneurysm.
In spite of the abdominal echography being the technique of choice for AAA screening, since this in a town general hospital, predominantly of social assistance, performing it was only considered feasible in patients diagnosed with AAA (in spite of which, 3 patients did not have a radiological test before 6 months). Anyway, 75% of the 28 AAA detected by TTE were subsequently confirmed by a radiological test (Figure 2), being a good correlation between the AAA dimensions determined by both explorations.
In spite of the prevalence of AAA being relatively low, in comparison to the other diseases under screening programs, their high mortality potential justifies an early diagnosis and in fact, its screening in cardiology by TTE meets the rest of the criteria by Frame and Carlson to follow a disease: a) the aneurysm has a long asymptomatic period; b) TTE is feasible as a method, accepted by patients, harmless, fast, economic and with good test features; c) the elective aneurysm repair in the pre-symptomatic phase considerably reduces its morbi-mortality in regard to urgent surgery; and d) the mortality of elective surgery in specialized centers is low (2-3%).
Additionally, it is reasonable to consider that in the patients visited in cardiology, this strategy would be more cost-effective than performing an abdominal echo exclusively for this.

7.1. AAA risk indices
The AAA risk index prepared from multivariate analysis attempts to be a useful diagnostic tool to make decisions; as a mnemotechnic device, it was called AAA-T (Age, femoral murmur Auscultation, suprarenal Aorta, Tobacco smoking). The second index prepared, the AA-T index (Age, femoral murmur Auscultation, Tobacco smoking), only covers the 3 clinical variables and it may be estimated during the office visit of the patient.
As a single previous experience about this, Spencer et al, selected a population susceptible of screening by a risk score developed after inviting males from 65 to 83 years old to participate in their study; such score was based on 10 variables determined after the patients answered a set of questions, underwent a physical examination (weight, height, waist and blood pressure) and abdominal echo; however, the authors themselves acknowledged that their method could underdiagnose a high percentage of cases [27].
However, the diagnostic ability of the two risk indices prepared will have to be validated in a new series of patients.

7.2. Recommendations of AAA screening in patients visited in cardiology
Based on the multivariate analysis, it is recommended to perform AAA screening during TTE in patients ≥55 years of age, who smoke or were smokers, in whom femoral murmur is detected, and in those that present larger arch and suprarenal aorta dimensions. Additionally, based on the descriptive, bivariate and univariate analysis, and the information in literature, male gender or the presence of coronary arteriosclerotic or peripheral vascular disease would further justify the study of these patients.
These recommendations are quite different from those by vascular societies, which likely is due to multiple factors; we should highlight that the present paper has developed in a population different than the general one, in whom TTE being indicated, it was supplemented with the study on the whole abdominal aorta. Additionally, if the AAA risk indices prepared are validated, they may help in selecting the population susceptible to screening.
The main goal of detecting AAA in a pre-symptomatic phase is performing an elective repair or a follow-up to prevent rupture. In the series, 27 from the 28 AAA were asymptomatic, and in regard to size, 23 AAA were small, 2 were middle sized, and 3 were large, so that most patients were referred to vascular surgery as management. And so based on the best scientific evidence available, AAA ≥5-5.5 cm, and in given cases >4.5 cm are especially tributaries of an elective repair surgery; otherwise, the follow-up of patients usually consists on performing a periodical abdominal echo according to its size.

 

LIMITATIONS
The design of the study does not allow establishing a causality relation between the variables. The small number of AAA in women, does not allow drawing definitive conclusions about the influence of gender on aneurysm; likewise, the small number of patients with ischemic heart disease may have been insufficient to detect a greater association with aneurysm.

Finally, due to care reasons, only the patients with AAA detected in TTE were studied by a radiological test.

 

CONCLUSIONS
Supplementing conventional TTE with the final study of infrarenal aorta (paraumbilical access) is feasible and useful to perform AAA screening in the patients studied by TTE for any cause, finding an overall prevalence of 4.2% and 5.2% in ≥55 years. The risk factors of AAA are age (since 55 years), smoking or having been a smoker, the existence of femoral murmur, and greater dimensions of the aortic arch and the suprarenal aorta. Thus, AAA screening is advised in patients with 1 or more risk factors; this finding should be later confirmed by a standard radiological test.

The final study of the infrarenal aorta should be included within the clinical practice standards and protocols to perform TTE in cardiology.

 

ACKNOWLEDGEMENTS
To Dr. A. Bardají.

 

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Publication: September 2014



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