Introduction
Aortic dissection (AD) is a rare but life-threatening medical emergency associated with a high mortality and morbidity rate. The primary event is a separation of the layers of the aortic wall by an inciting intimal injury, after which the blood rushes through the tear, causing the inner and middle layers of the aorta to dissect. The estimated incidence ranges from 2.6 to 3.5 per 100,000 person-years. (1)
Acute aortic syndromes (AASs) include a spectrum of life-threatening aortic conditions. By convention, acute disease is distinguished from chronic disease at an arbitrary time point of two weeks from initial clinical presentation (hyperacute: <24 hours, acute: 1 to 14 days, subacute: >14 to 90 days, chronic: >90 days) and typically manifests with symptoms. (2)
AD is categorized into the following two main types by Stanford: type A involving the aortic root, ascending aorta, and/or arch of the aorta, and type B in which the dissection begins in the descending part of the aorta, distal of the left subclavian artery. Stanford dissection type A is more common and has a high mortality rate compared with Stanford type B. (3)
AD usually presents with sudden tearing chest pain that often radiates to the back, and is a medical emergency. Other common symptoms include abdominal pain, diaphoresis, loss of consciousness, shortness of breath, stroke-like symptoms, or leg pain. (4)
Computed tomographic angiography (CTA) is the diagnostic imaging modality of choice in hemodynamically stable patients. It is highly sensitive and specific for imaging aortic pathology. The study should include the entire aorta, including the iliac and femoral vessels. Other imaging modalities such as transthoracic echocardiography (TTE) or transesophageal echocardiography (TEE) may be useful in hemodynamically unstable patients as first line diagnostic tools. Both TTE and TEE can identify aortic valve disruption leading to regurgitation, hemorrhagic pericardial effusion, and tamponade, as well as regional wall motion abnormalities from coronary artery involvement. However, complete imaging of the distal arch and descending aorta are limited with TTE, and these may not be diagnostic for intramural hematoma. (5)
Herein, we present a case of an incidental finding of AD on computed tomography coronary angiography (CTCA) in a patient who did not have any corresponding medical history and was without typical symptoms both before and on hospital admission, as well as also during the hospital stay.
Case report
The patient, a 82-year-old man, was referred to the Emergency Medicine Clinic from the corresponding primary level outpatient clinic due to symptoms in the form of shortness of breath, swelling of the lower extremities, and dry cough, which had lasted for the past 5-6 weeks and intensified ten days before referral. The patient was otherwise without any prescribed chronic therapy, and was a long-time smoker who had not attended regular medical check-ups, with no previous cardiac diagnoses and hospitalizations. The patient claimed that he had allegedly had a stroke 7 years ago, but did not provide any medical documentation.
Upon admission, the auscultatory findings on the heart and lungs were without peculiarities on physical examination, and discrete pretibial bilateral edema was present, whereas the patient was normotensive and properly saturated. The patient complained of shortness of breath and swelling in both legs, denied that he ever had any form chest pain, whether sudden or gradually increasing, also he denied any loss of consciousness. An electrocardiogram (ECG) was performed on admission – a favorable sinus rhythm with two single premature ventricular contractions and no signs of ischemia was noted; mild normocytic anemia was present in laboratory findings; high-sensitivity troponin I results were hsTnI 48 ng/L (reference values up to 14 ng/L), while the rest of the laboratory results were within reference ranges. Chest X-ray showed signs of enlarged mediastinum at the expense of vascular structures, the right hilum was less differentiated, the left phrenicocostal sinus was inhomogeneously shadowed, and there were signs of inhomogeneous opacity in the left paracardial space (Figure 1). The patient was hospitalized at the Department of Cardiology under a diagnosis of congestive heart failure. Parenteral diuretic and other supportive therapies were prescribed, after which the patient’s condition subjectively and clinically improved. TTE was performed, which showed a dilated ascending aorta (tubular section 4.9 cm); there was no evident intimal flap on the left parasternal long axis (PLAX) view (Figure 2), and signs of moderate aortic regurgitation were present (Figure 3), while estimated systolic pulmonary artery pressure was at approximately 38 mmHg. Left atrial volume index was mildly above the normal limits (LAVI 38 mL/m2), left ventricular systolic function was preserved (LV EF above 55%), no regional wall motion abnormalities were found, the mitral and tricuspid valves showed signs of mild, first-degree regurgitation, and there were no signs of pericardial effusion. We emphasize that no right parasternal, suprasternal, or subcostal aortic imaging was performed during the first TTE exam.
CTCA was performed on the twelfth day of hospitalization due to suspected ischemic changes on a control ECG: biphasic and negative T waves in precordial leads that were not observed on admission (patient did not report any type of chest pain, he complained only of fatigue). Multivessel coronary disease was verified: right coronary artery – proximal stenosis up to 50%; left anterior descending artery – proximal stenosis approximately 60%; left circumflex artery – proximal stenosis approximately 60%; first obtuse marginal artery proximal stenosis of 55%, but an aneurysmatic, enlarged ascending aorta with a diameter of 5.2 cm in the tubular section was also observed, on which a dissection flap (Figure 4) was observed ventrally and along the upper contour of the right coronary sinus, followed cranially in favor of dissection type A according to the Stanford classification. After CTCA, CTA of the whole aorta was performed, and dilatations of the aortic sinus (3.9 cm) and ascending aorta (4,9 cm) were confirmed, with a visible dissection flap on the right lateral wall continuing to the final part of the ascending aorta (Figure 5) – confirming the Stanford type A dissection. In the descending part of the thoracic aorta the diameter was up to 31 mm, without signs of dissection.
The patient’s case was presented to cardiac surgeons, but the patient was not willing to accept the recommended treatment. He left the hospital at his own request in a clinically compensated state, and medication therapy with regular follow-up clinical examinations were recommended, which the patient refused to attend.
Discussion
Aortic dissection and other aortic syndromes are described in terms of the anatomic location of the intimal tear, the duration of time from its occurrence, and clinical features, including the absence or presence of symptoms and whether disease complications occur. The nature of the complications differs for each variant, but each has the potential to cause life or limb-threatening complications. (6)
Although many patients report symptoms such as chest, back, or abdominal pain, there is significant overlap with other acute syndromes and signs, making a precise diagnosis particularly difficult. In fact, most patients with AD do not present these classic symptoms, but only some of the well-known indicators. This has led to AD being referred to as “the great masquerader”. (7)
In the presented case, there were no typical clinical signs and symptoms of dissection in the patient (pulse deficit, signs of threatening tamponade, newly-occurring murmur, excruciating sudden chest pain, syncope), and the intimal flap was first confirmed as an incidental finding on CTCA. In contrast to this, AASs are rarely identified as incidental findings with minimal symptoms on advanced imaging studies, although this has been reported. (8)
TTE allows adequate assessment of several aortic segments, particularly the aortic root and proximal ascending aorta. All scanning planes should be used to obtain information on most aortic segments. The right parasternal view is recommended for estimating the true size of the ascending aorta. The suprasternal modified view is of paramount importance for evaluation of the thoracic aorta, whereas in some cases (more frequently in children) the modified subcostal view may be helpful, but here the ascending aorta is far from the transducer. However, if inconclusive information or abnormalities are present, another imaging modality is required to either complete or add diagnostic information. (9)
Multimodality imaging, such as an aortic CTA, TTE, and TEE, as well as magnetic resonance imaging, have been shown to play an important role in the diagnosis, treatment of complications, and clinical management of AD. (10) Deep learning algorithms are being developed with automatic triage systems that could potentially accelerate clinical workflow by enabling rapid and precise diagnosis, which is crucial for conditions that require urgent surgical intervention such as type A AD. (11)
Consensus is lacking on what should reproducibly define a clinical suspicion of AASs. The differences between physicians and centers can therefore be profound. In a North American retrospective series of patients undergoing CTA for suspected AAS, the prevalence of AASs was ~3%. In a large out-of-hospital study evaluating the AD detection risk score (ADD-RS) in nontraumatic emergencies, the prevalence of AASs was 0.9%. (12)
In the present case, no right parasternal, suprasternal, or subcostal views of the ascending aorta were performed during the TTE exam, while no intimal flap was present on the left PLAX. The question remains whether AD would have been discovered earlier in this case if the dilated aorta was viewed from atypical windows during the initial TTE examination, according to the guidelines (which might have raised suspicion for further assessment).
After the diagnosis of AD was confirmed, TTE was repeated and no clear signs of intimate flap were observed in atypical windows, although they were not suitable for a more detailed analysis. Given the atypical clinical presentation and nonspecific findings on TTE, the question arises whether TTE-determined dilatation of the ascending aorta in any scenario should by default be referred to CT angiography regardless of the size of the aortic dilatation and whether symptoms and clinical suspicion for AASs are present.
Even though there were no severe outcomes, cases such as this confirm that regardless of one’s expertise and what has been done as part of patient’s diagnostic assessment and treatment, the deceptiveness of clinical presentation is always a possibility, and the outcome for the patient always carries an element of chance.
Conclusion
Aortic dissection is a rare but potentially lethal medical emergency, in which prompt diagnosis remains a challenge in clinical practice because of its rarity and possible deceptiveness of presentation that complicates the differential diagnosis; therefore, its atypical forms in terms of clinical presentation and imaging tests should be taken into account.