Key Words
Aortic dissection - Painless
Introduction
The classical presentation of a patient with acute aortic dissection (AAD) is characterized
by severe chest, back, or abdominal pain. However, previous reports showed that between
5 and 17% of all dissection patients present with painless acute aortic dissections[1]
[2]. As expected, atypical presentation can lead to a delay in diagnosis, which is associated
with higher mortality[3]
[4]. Painless Type B acute aortic dissection (TBAAD) does not mean that these patients
have uncomplicated dissections, as they still can develop malperfusion and aortic
rupture[1]
[2]. Immediate adequate medical treatment is essential and has to include optimal blood
pressure control in order to reduce shear stress and limit the propagation of the
dissection. Therefore, it is important to recognize these patients at the earliest
possible stage. The aim of the current study was to assess the clinical characteristics,
diagnostics, treatment, and outcomes of patients with painless TBAAD.
Methods
Patient Selection
The International Registry of Acute Aortic Dissection (IRAD) is an ongoing multinational
registry designed to provide a representative population of patients with acute aortic
dissection. The rationale, design, and methods of IRAD have been previously published[5]. The diagnosis of TBAAD was based on clinical symptoms, diagnostic imaging, direct
visualization during surgery, and/or postmortem examination. Patients were enrolled
at diagnosis or retrospectively. We analyzed all TBAAD patients enrolled in IRAD from
January 1996 to July 2012 and selected those patients presenting without any pain
symptoms. Demographics, medical history, presenting symptoms, management, and outcomes
were compared between patients presenting with and without pain.
Statistical Analysis
Categorical variables were compared for both groups utilizing the chi-squared tests
and Fisher's exact tests. Student's t-test was used to analyze continuous variables
and the nonparametric test of medians to analyze non-normally distributed variables.
A p-value <0.05 was considered significant. Kaplan-Meier survival curves were plotted
to estimate survival. Data analysis was performed with the use of SPSS statistical
analysis software (SPSS Inc, Chicago, Ill).
Results
Among the 1162 TBAAD patients enrolled in IRAD, 43 patients presented with painless
TBAAD (3.7%). The mean age of patients with painless TBAAD was significantly higher
than normal TBAAD patients (69.2 versus 63.3 y; p-value = 0.020, [Tables 1]–[3]). Painless patients presented more often with a history of diabetes, (17.9% versus
7.5%; P = 0.018), atherosclerosis (46.4% versus 30.1%; P = 0.022), and were more often diagnosed with a known prior aortic aneurysm (31% versus
18.8%; P = 0.049) Painless patients presented less frequently with hypertension (45.9% versus
68.8%; P = 0.003) and with a lower mean systolic blood pressure (mean 147.28 mm/Hg versus
166.8.2 mm/Hg; P = 0.003). Syncope was more represented in the painless group (10.3% versus 2.5%;
P = 0.020).
Table 1.
Demographics and Patient History
|
Category
|
Type B
|
|
|
Demographics
|
Not Painless (%)
|
Painless (%)
|
p-value
|
|
Patients (n)
|
1119
|
43
|
|
|
Age (mean±SD)
|
63.3±14.1
|
69.2±10.8
|
0.020
|
|
Gender – male
|
773 (66.9)
|
25 (58.1)
|
0.234
|
|
Race – non-white
|
913 (82.7)
|
35 (85.4)
|
0.657
|
|
Hypertension
|
918 (80.2)
|
37 (86.0)
|
0.348
|
|
Diabetes
|
85 (7.5)
|
7 (17.9)
|
0.018
|
|
Marfan syndrome
|
41 (3.6)
|
0 (0.0)
|
0.396
|
|
Atherosclerosis
|
339 (30.1)
|
20 (46.5)
|
0.022
|
|
Known aortic aneurysm
|
212 (18.8)
|
13 (31.0)
|
0.049
|
|
Prior AAD
|
90 (8.0)
|
3 (7.3)
|
1.000
|
|
Aortic valve disease
|
69 (6.1)
|
4 (10.3)
|
0.302
|
|
Other aortic disease
|
23 (2.3)
|
3 (8.6)
|
0.051
|
|
Family history of aortic disease
|
48 (11.6)
|
1 (10.0)
|
1.000
|
|
Prior cath/angiography
|
98 (10.3)
|
6 (21.4)
|
0.061
|
|
Prior CABG
|
49 (4.4)
|
1 (2.6)
|
1.000
|
|
Prior surgery for aortic aneurysm/dissection
|
145 (13.1)
|
6 (14.6)
|
0.775
|
|
Intramural hematoma
|
131 (11.7)
|
6 (14.0)
|
0.654
|
|
Iatrogenic AAD
|
14 (1.3)
|
8 (19.5)
|
<0.001
|
|
Hours presentation to diagnosis (median)
|
19.0 (12.7–25.3)
|
34.0 (22.8–72)
|
0.006
|
AAD indicates acute aortic dissection; CABG, coronary artery bypass grafting.
Table 2.
Presenting Symptoms/Signs of Aortic Dissection
|
Type B
|
|
|
Category
|
Not Painless (%)
|
Painless (%)
|
p-value
|
|
Presenting hypertensive
|
763 (68.8)
|
17 (45.9)
|
0.003
|
|
Presenting hypotensive
|
80 (7.3)
|
4 (10.0)
|
0.532
|
|
Mean systolic blood pressure
|
166.8
|
147.2
|
0.003
|
|
Mean systolic blood pressure
|
91.44
|
85.0
|
0.095
|
|
Presented with pulse deficits
|
173 (18.6)
|
2 (8.3)
|
0.286
|
|
Shock
|
11 (1.0)
|
1 (2.7)
|
0.327
|
|
Syncope
|
28 (2.5)
|
4 (10.3)
|
0.020
|
|
Cerebrovascular accident
|
14 (1.3)
|
2 (5.1)
|
0.100
|
|
Ischemic peripheral neuropathy
|
31 (2.8)
|
0 (0)
|
0.622
|
|
Spinal cord ischemia
|
31 (2.8)
|
0 (0)
|
0.622
|
|
Limb ischemia
|
101 (9.3)
|
0 (0)
|
0.043
|
|
Acute renal failure
|
161 (14.8)
|
8 (20.0)
|
0.364
|
Table 3.
Imaging
|
Type B
|
|
|
Category
|
Not Painless (%)
|
Painless (%)
|
p-value
|
|
CXR done
|
1002 (86.7)
|
37 (86.0)
|
0.905
|
|
CXR normal
|
275 (28.1)
|
8 (21.6)
|
0.389
|
|
CXR showed abnormal aortic contour
|
397 (43.9)
|
16 (47.1)
|
0.713
|
|
CXR showed abnormal cardiac contour
|
141 (15.8)
|
2 (6.2)
|
0.211
|
|
ECG done
|
1087 (94.0)
|
36 (83.7)
|
0.006
|
|
ECG normal
|
409 (38.2)
|
10 (28.6)
|
0.250
|
|
TEE done
|
574 (50.4)
|
20 (47.6)
|
0.724
|
|
CT done
|
1110 (96.2)
|
34 (82.9)
|
<0.001
|
|
CT Normal
|
6 (0.6)
|
1 (3.2)
|
0.184
|
|
Angiography
|
207 (18.2)
|
9 (24.3)
|
0.345
|
|
MRI done
|
185 (16.7)
|
10 (27.8)
|
0.081
|
|
Periaortic hematoma identified on any imaging study
|
150 (14.5)
|
6 (16.7)
|
0.718
|
|
Most proximal extension:
|
|
|
|
|
Aortic arch
|
263 (22.8)
|
7 (16.3)
|
0.318
|
|
Left subclavian artery
|
577 (49.9)
|
19 (44.2)
|
0.461
|
|
Descending
|
280 (24.2)
|
13 (30.2)
|
0.368
|
|
Largest diameter of descending aorta (median)
|
4.0 (3.5–5.0)
|
3.6 (3.0–4.7)
|
0.137
|
CXR indicates chest X-ray; ECG, electrocardiograph; TEE, transesophageal echocardiography;
CT, computed tomography; MRI, magnetic resonance imaging.
Diagnostics
As might be expected, the mean time interval between admission and diagnosis of aortic
dissection was 34.0 hours among painless patients, as compared to 19.0 hours in the
control group (P = 0.006). Computed Tomographic Angiography (CTA) was more often used as the primary
diagnostic modality in the painful group (96.2 versus 82.9%, < 0.001). Previous angiography
was more frequently performed in the painless group and these patients also had significantly
more iatrogenic dissections (19.5 versus 1.3%; P < 0.001). The iatrogenic cause in the painless group was: Percutaneous transluminal
coronary angioplasty (PCTA) in three patients (37.5%), cardiac surgery in three patients
(37.5%), and unknown cause in two patients (25%).
Management and Outcome
Almost two-thirds of the patients were treated medically, which did not differ between
groups. (65.2 versus 65.1%; P = 0.988; [Table 4].) Surgical and endovascular therapies were equally used in approximately 35% of
each group. In-hospital mortality was 18.6% in the painless group, compared with an
in-hospital mortality of 9.9% in the control group (P = 0.063). There were no statistically significant differences in complications between
both groups. Kaplan-Meier survival curves did not demonstrate a significant difference
in mortality during five-year follow-up (P = 0.960; [Fig. 1]).
Table 4.
Management
|
Type B
|
|
|
Category
|
Not Painless (%)
|
Painless (%)
|
p-value
|
|
Medical management
|
754 (65.2)
|
28 (65.1)
|
0.988
|
|
Surgical management
|
137 (11.9)
|
6 (14.0)
|
0.676
|
|
Endovascular management
|
251 (21.7)
|
9 (20.9)
|
0.903
|
|
In-hospital mortality
|
114 (9.9)
|
8 (18.6)
|
0.063
|
|
Medical management
|
57 (7.8)
|
3 (10.7)
|
0.468
|
|
Surgery
|
25 (18.2)
|
3 (50.0)
|
0.089
|
|
Endovascular
|
31 (12.4)
|
2 (22.2)
|
0.320
|
Figure 1. Kaplan Meier survival curve.
Discussion
The most common characteristic of TBAAD presentation is acute pain localized to the
chest, abdomen, and back. Previous IRAD reports showed that 95.5% of all AAD patients
presented with pain[5]. However, in rare instances the presentation of dissection can be atypical and our
study showed that 3.7% of all TBAAD patients were painless, in contrast with previous
experiences which reported an incidence up to 17% in AAD[1]
[2]. The lower incidence that we observed could be explained by the fact that, while
this study focused only on TBAAD, previous studies focused on painless dissections
in general, including a majority of patients with ascending aorta involvement (Type
A acute aortic dissection), which makes up for more than 75% of the patient population[1]
[2]. In addition, IRAD consists of cardiovascular referral centers, specialized in the
treatment of aortic dissection, where patients are referred for surgical/endovascular
treatment, whereas patients who are thought to be unfit for invasive management will
not be transferred to these centers. Typically, transferred patients have more complications,
resulting in a relative low incidence in the IRAD database. The true incidence in
the population is probably even higher, as an atypical presentation will likely result
in a higher risk of death prior to the diagnosis.
The clinical presentation of dissection patients may be diverse, and sudden collapse
or an altered state of consciousness have been reported to be the presenting symptom
in up to 30% of all patients[6]. This report also included TAAAD patients, which are more prone to develop complications
like syncope or alteration in consciousness[7]. Painless AAD, especially concerning the ascending aorta, presents more often with
neurological deficits, syncope, and disturbances in consciousness. These complications
influence the perception of pain, resulting in a relative high prevalence of Type
A dissection in this patient category. As expected, painless Type B dissection patients
did not show this clinical pattern since involvement of the head and neck vessels
did not occur.
Our study showed that TBAAD painless patients are older at presentation and more often
had a history of atherosclerosis. With increasing age, the incidence of painless dissections
might rise, as previously reported[1]. In that study, patients who presented at significantly older age, more frequently
had a history of cerebrovascular accidents, and some patients had only atypical symptoms
such as dyspnea, nausea, and abdominal fullness. These three atypical clinical signs
were not recorded within the IRAD registry, so we can't make any comparison.
The pathological mechanism of painless TBAAD is not well understood and multiple explanations
for this phenomenon have been proposed. Our study showed that painless patients present
with less hypertension. Due to low blood pressure, the propagation of the dissection
might develop relatively slow, thereby reducing the wall stress, which could result
in reduction of pain. Alternatively, pain will act as an acute stressor, determining
an increased blood pressure. Furthermore, the perception of pain can be modulated
as the adventitial layer, the site for aortic innervation, is involved by the dissection
or affected by previous interventions. In addition, it is thought that other pathologies,
like aneurysmatic enlargement, may influence the ability to sense pain. This possibility
is supported by the higher incidence of other aortic disease and previous aortic aneurysms
in our study population. Most interestingly, significantly more painless patients
had a dissection of iatrogenic origin. Iatrogenic dissections are thought to occur
very rarely, with Type A dissections reported in 0.04% of the patients during percutaneous
coronary interventions and in 0.12 to 0.16% after cardiac surgery procedures[8]
[9]
[10]
[11]. The incidence of TBAAD in these patients is thought to be even lower. During such
procedures, analgesics and sedation may alter the patient's perception of pain, increasing
the incidence of painless TBAAD in this subset of patients[12].
The in-hospital mortality was 18.9% in the painless group, compared with an in-hospital
mortality of 10.3% in the control group (P = 0.096). The explanation for this trend is probably 2-fold. First, the painless
group tended to present at older age, which is a condition associated with a higher
mortality[13]. Second, the extended delay to diagnosis and treatment, due to the difficulty in
diagnosis, may have resulted in a higher mortality.
Although this study represents the first report focusing specifically on TBAAD with
absence of pain at presentation, it has some limitations. Previous studies reported
a higher incidence and registry data might not reflect the true incidence, since the
centers are specialized in aortic dissection and therefore receive many referred patients.
Furthermore, many patients may have died from a painless dissection before they were
diagnosed and therefore are not registered.
Conclusion
Painless TBAAD is a relatively rare presentation of aortic dissection and is associated
with a history of atherosclerosis, diabetes, iatrogenic origin, and aortic disease
like aneurysm. We observed a trend in increased in-hospital mortality rate among painless
TBAAD patients, which may be the result of a delay in diagnosis and any type of management
due to the absence of classical symptoms. Therefore, physicians should be aware of
this relatively rare presentation of TBAAD.
