Patients with aortic enlargement are recommended to undergo serial imaging and clinical follow-up until they reach surgical thresholds. This study aimed to identify aortic diameter and care of patients with aortic imaging before aortic dissection (AD). In a retrospective cohort of AD patients, we evaluated previous imaging results in addition to ordering providers and indications. Imaging was stratified as >1 or <1 year: 62 patients (53% men) had aortic imaging before AD (most recent test: 82% echo, 11% computed tomography, 6% magnetic resonance imaging). Imaging was ordered most frequently by primary care physicians (35%) and cardiologists (39%). The most frequent imaging indications were arrhythmia (11%), dyspnea (10%), before or after aortic valve surgery (8%), chest pain (6%), and aneurysm surveillance in 13%. Of all patients, 94% had aortic diameters below the surgical threshold before the AD. Imaging was performed <1 year before AD in 47% and aortic size was 4.4 ± 0.8 cm in ascending aorta and 4.0 ± 0.8 cm in sinus. In patients whose most recent imaging was >1 year before AD (1,317 ± 1,017 days), the mean ascending aortic diameter was 4.2 ± 0.4 cm. In conclusion, in a series of patients with aortic imaging before AD, the aortic size was far short of surgical thresholds in 94% of the group. In >50%, imaging was last performed >1 year before dissection.
An acute type A aortic dissection (AD) is a rare, life-threatening condition associated with a high acute mortality rate. Aortic dilation is an important risk factor for AD, and current guidelines recommend consideration of elective aortic repair in asymptomatic patients when the diameter of the ascending aorta reaches a threshold of 5.5 cm although the threshold is lower (4.5 to 5 cm) for those with syndromic/heritable conditions and those undergoing cardiac surgery. Once identified with aortic enlargement, patients are recommended to undergo serial clinical and imaging follow-up until the size threshold is reached. , In this retrospective case series of patients with imaging before subsequent type A AD, we sought to understand the clinical care pathway of these patients by evaluating the specialist and indication for the imaging, the imaging modality, as well as the aortic size and time interval of the imaging before an AD event. Furthermore, we evaluated the change in aortic size at the time of AD.
Methods
Using electronic medical records from the Minneapolis Heart Institute at Abbott Northwestern Hospital, we retrospectively identified patients who had a type A AD between January 2003 to March 2020. Inclusion criteria for this study were an age of 18 years or older, the patient’s first type A AD, at least 1 imaging examination (echocardiogram, computed tomography [CT], or magnetic resonance imaging [MRI]) in which the diameter of the sinus of Valsalva and/or ascending aorta was measured before AD. We excluded patients with previous ascending aorta (including AD) repair and those with iatrogenic and arch dissections. Aortic size was identified at the sinus of Valsalva and ascending aorta using established standards. The Allina Institutional Review Board approved this study.
Electronic medical records were reviewed for baseline patient demographics and aortic/cardiovascular risk factors, clinical indications, and ordering physicians. The dates and aortic diameters from the most recent imaging tests before AD were recorded in addition to the aortic measures and the time of AD. Aortic diameters were remeasured by experienced imaging physicians on the available imaging examinations before AD, using standard techniques. Aortic diameters were reported using the remeasured value when available or last clinical measurement, as well as restricted to those with remeasured values. As normal aorta size varies based on body size, we also indexed to body size, where the threshold of 2.75 cm/m 2 indicates a moderate risk for AD.
Baseline characteristics, cardiovascular risk factors, and previous clinical care characteristics were evaluated for the entire cohort and each subset. Continuous variables are displayed as means and SDs (and ranges in parentheses, if relevant) for normal distributions or medians and interquartile ranges (IQRs) for skewed distributions. Categorical variables are displayed as the number and percentage of patients with the characteristic. A Student t test was used to determine significant differences in aortic diameters.
Results
A total of 62 patients (27% of 227 patients with type A over this time interval) had imaging before the type A AD event at our facility. The median (IQR) age was 73 (64 to 78 years); 53% were men. Risk factors for AD included hypertension (77%), previous cardiac surgery (24%), and aortic valve disease (34%). ( Table 1 ).
| Variable | Patients with type A dissections and previous imaging (n = 62) |
|---|---|
| Age, median (Q1, Q3) years | 72.5 (64.25, 78) |
| Men | 33 (53%) |
| White | 56 (90%) |
| Black | 2 (3%) |
| Asian | 2 (3%) |
| American Indian | 1 (2%) |
| Hypertension | 48 (77%) |
| Marfan syndrome | 3 (5%) |
| Atherosclerosis | 14 (23%) |
| Bicuspid aortic valve | 3 (5%) |
| Aortic valve disease * | 21 (34%) |
| Diabetes mellitus | 6 (10%) |
| Previous cardiac surgery | 15 (24%) |
| Turner syndrome | 1 (2%) |
⁎ Aortic insufficiency (9 mild, 2 moderate, 4 severe), aortic stenosis (1 mild, 1 moderate, 1 severe) or combined aortic insufficiency/stenosis.
The imaging modality that was performed in closest proximity preceding the AD event was most commonly echocardiogram (82%), and less commonly CT (11%), and MRI (6%). Previous testing included an echo in 90%, CT in 31%, and MRI in 23%. The median (IQR) number of days between the most recent previous imaging and AD was 411 (175 to 1,034). Most recent testing was ordered by cardiologists (39%), internal medicine (19%), family medicine (16%), hospital medicine (11%) and other (15%) (surgical and sub-specialist) physicians. Cardiologists had previously evaluated 48 (77%) of the cohort. The indications for the most recent imaging before AD are listed in Table 2 . In 13% of patients, the test was done solely for monitoring of thoracic aortic aneurysm. Aortic enlargement was identified on the problem list in 27 (43%) of the group and only 4 (6%) were scheduled for follow-up imaging at the time of their AD.
| Variable | Frequency (%) (n = 62) |
|---|---|
| Aortic dilation or aneurysm | 8 (13%) |
| Arrhythmia | 7 (11%) |
| Dyspnea | 6 (10%) |
| Aortic valve surgery | 5 (8%) |
| Coronary artery disease | 5 (8%) |
| Chest pain | 4 (6%) |
| Aortic insufficiency | 3 (5%) |
| Myocardial infarction | 3 (5%) |
| Stroke | 3 (5%) |
| End stage renal disease | 2 (3%) |
| Precordial murmur | 2 (3%) |
| Hypertrophic cardiomyopathy | 2 (3%) |
| Marfan syndrome | 2 (3%) |
| Mitral valve replacement | 3 (5%) |
| Other * | 8 (13%) |
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