Early acute ischaemic stroke in two patients with acute type B aortic dissection: an unusual complication

Abstract

Aortic thoracic dissection (AD) is a serious cardiovascular disease. According to the Stanford classification; type A involves the ascending aorta and type B the descending distal to the left subclavian artery. Neurological complications secondary to AD are devastating. Ischaemic stroke and hypoxic encephalopathy are early-recognised complications of type A as the arch vessels can be involved AD. Although, late ischaemic stroke had been reported in 1.4–5% of patients with type B dissection, early stroke is very unusual as it cannot be simply explained by AD anatomical pathogenesis. We report two patients who presented with type B AD complicated by early ischaemic strokes. Work-up revealed significant cardiomyopathies in both patients but with left ventricle thrombus in one. In both patients the strokes were felt to be of cardioembolic origin.

Background

Acute aortic dissection (AD) incidence is estimated to range from 2.6 to 3.5 per 100 000 person-years.^{1 2} While, hypertension is considered the most important risk factor,³ pre-existing aortic aneurysm, inflammatory vasculitis and collagen vascular disease are strongly associated with AD in the younger population.^{4 5}

Aortic intimal tear followed by further separation in layers of the vessel walls creating a false lumen/s is thought to be the initial inciting event. Complications are mostly related to the location and progression of the tear. This led to establishing Stanford and DeBakey Aortic Dissection Classification Systems.⁶

Aortic dissection distal to the left subclavian artery (type B) is considered to be a more benign form. Patients generally exhibit a fewer neurological complications and are usually managed medically. They rarely require surgical or endovascular interventions unless complications arise. Most of neurological complications secondary to type B AD are related to spinal cord ischaemia or ischaemic neuropathy; however, two large case series of AD outcomes reported late ischaemic strokes in 1.4–5% of patients but did not clearly indicate if the strokes were related to the dissection process itself or were independent complications.^{7 8}

Early-onset ischaemic strokes include acute neurological deficits on presentation or during the admission; however, delayed-onset strokes are defined as neurological deficits, which develop during medical or surgical treatment within 2 months after discharge.⁷ Any ischaemic stroke associated with type B AD warrants extensive work-up to ascertain that no other comorbid conditions are overlooked.

One of our patients had an left ventricle (LV) thrombus but both patients had cardiomyopathies suggesting alternative diagnoses. Managing patients with acute stoke secondary to an LV thrombus in the settings of AD presents a dilemma. The administration of anticoagulation in the setting of an acute dissection is not without risk.

Case presentation

Case reports

Case 1: A 39-year-old hypertensive Hispanic man presented with severe sudden onset chest and abdominal pain. In the emergency room, his systolic blood pressure was 250/150 mm Hg. His electrocardiogram (EKG) showed normal sinus rhythm but with T wave inversion. Cardiac enzymes were normal. A rapid chest and abdominal CT angiography (CTA) showed acute type B AD distal to the left subclavian artery origin (video 1). He was transferred to the intensive care unit (ICU) for blood pressure control on Nicardapine infusion. His blood pressure on arrival to the ICU was 140/80 mm Hg but he reported to have left-sided numbness and was unable to move his left extremities. Neurological examination was remarkable for left eye ptosis, right horizontal gaze palsy, left facial droop, left-sided hemiparesis and hemi sensory deficit. CTA of the head, neck and chest showed no evidence of intracranial bleeding, acute stroke, critical vascular stenosis or extension of the dissection to the extracranial or intracranial vasculature. He was not a candidate for acute thrombolytic therapy given his acute AD. Cardiothoracic surgical team recommended low dose aspirin (81 mg daily) and conservative management with no surgical intervention, however; a subsequent brain MRI (figure 1) demonstrated multiple areas of increase diffusion-weighted imaging signal seen in the right half of the pons and bilateral cerebral hemispheric white matter representing acute infarcts as well as acute ischaemic stroke in the left external capsule. He underwent a transesophageal echocardiogram (TEE), which showed a thrombus in the left ventricular apex as well as low estimated ejection fraction (EF) of 30–35% (video 2). There was no patent foramen ovale (PFO). Lipid profile, HgbA1c, urine toxicology screen, HIV test, syphilis test, blood culture, autoimmune work up, iron level and Trypanosoma Cruzi test were unrevealing. After discussing the risks and benefits of anticoagulation with him and his family, he was started on intravenous heparin and aspirin discontinued. The patient remained clinically stable and was discharged to an acute rehabilitation unit a few weeks later. His neurological deficits improved dramatically over the subsequent few months. He was discharged on several medications for heart failure. A repeat echocardiogram 3 months after discharge showed an improvement in the EF to 45%.

Figure 1.

Brain MRI demonstrates focus of acute infarct in the left external capsule, which is flare positive indicating at least 6 h of age.

Video 1.

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DOI: 10.1136/bcr-2015-210021.video01

Chest and abdominal CT angiography (CTA) shows acute type B AD distal to the left subclavian artery origin.

Video 2.

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DOI: 10.1136/bcr-2015-210021.video02

Transesophageal echocardiogram (TEE), which showed a thrombus in the left ventricular apex as well as low estimated ejection fraction (EF) of 30–35%.

Case 2: A 58-year-old African-American woman with uncontrolled hypertension, presented with severe sudden onset abdominal pain that radiated to her back. The blood pressure was 170/66 mm Hg. A chest and abdominal CT angiogram demonstrated a type B AD that was distal to the left subclavian artery and ended at the right common iliac artery (video 3). She was started on esmolol infusion to keep her systolic blood pressure below 120 mm Hg. On return from ICU, she reported new onset of chest pain with ST segment elevation in the anterior leads on ECG. Immediate coronary angiography revealed normal coronaries with no evidence of aortic root dissection. The cardiothoracic team recommended medical management of her blood pressure, low dose aspirin and no surgical intervention. Two days later, she developed a sudden onset voice change and had a right facial droop. Neurological examination showed no aphasia, but she had a right lower facial weakness, right upper extremity pronator drift and right Babinski response. Urgent head (CTA) scan was unrevealing. She was not eligible for thrombolytic therapy given her newly diagnosed acute AD. MRI showed Small acute infarcts in bilateral parietal and occipital lobes, right precentral gyrus, the left precentral gyrus, and the right cerebellar hemisphere. Patient underwent a transthoracic echocardiogram (video 4; TTE), which showed severe concentric left ventricular hypertrophy and low estimated EF of 40%, but there was no thrombus, valvulopathy or PFO. A few days later, her neurological deficit rapidly improved and she was transferred out of the ICU. Approximately a week later, she developed another intermittent episode of difficulty finding words that lasted for a few minutes but completely resolved spontaneously. A repeated brain MRI showed new ischaemic stroke in the bilateral corona radiata compared to the previous image as well as small acute infarcts in bilateral parietal and occipital lobes likely embolic (figure 2). Patient continued to improve and was discharged home later with no neurological deficit. Although, cardioembolic stroke was a consideration, anticoagulation was not initiated since the patient and her family did not accept the associated risks it in the setting of acute AD and no compelling evidence of LV thrombus.

Figure 2.

MRI brain demonstrates small acute infarcts in bilateral parietal and occipital lobes likely embolic.

Video 3.

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DOI: 10.1136/bcr-2015-210021.video03

Chest and abdominal CT angiography (CTA) showing type B AD that was distal to the left subclavian artery and ended at right common iliac artery.

Video 4.

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DOI: 10.1136/bcr-2015-210021.video04

Transthoracic echocardiogram (video 4; TTE), which showed severe concentric left ventricular hypertrophy and low estimated ejection fraction of 40%, but there was no thrombus, valvulopathy or patent formaen ovale (PFO).

Discussion

Acute ischaemic strokes occurring in the setting of acute type B AD are very infrequent and determination of the exact cause can be extremely difficult. As the tear is almost always distal to the left subclavian artery there is no malperfusion of the arch vessels unless an aberrant right subclavian artery is present. We propose the following mechanisms as possible scenarios for acute strokes in patients with type B AD:

1. Causes related to AD:

   1. Retrograde flow from descending aorta associated with turbulence.
   2. Retrograde extension of the dissection or the false lumen thrombus.
   3. Iatrogenic hypotension during medical management of the dissection.
   4. Reversible posterior leuckoencephalopathy secondary to severe hypertension management of the dissection.
   5. Hypotension resulting from blood loss or as a result of malperfusion of other organs causing shock.
2. Causes unrelated to AD:

   1. Cardioembolic sources secondary to cardiomyopathies with or without an LV thrombus.
   2. Dysrhythmias causing dislodgment or formation of a new LV clot.
   3. Paradoxical embolus through a PFO in patients with deep vein thrombosis (DVT) secondary to prolonged immobilisation and limited DVT prophylaxis options.

All patients with acute stroke in the setting of type B AD should receive extensive workup that includes but not limited to brain CT and MRI, TEE with bubble study and extremities US Doppler.

Once ischaemic stroke is identified, the management should be individualised. Although, lytic therapy in the setting of an acute dissection is absolutely contraindicated, anticoagulation should be cautiously considered in patients with cardioembolic source.

Unfractionated heparin is probably the only option in such settings and should be used judiciously with stringent attention to ensure that the direct complications related to the dissection do not extend. Repeating MRI and or CT of the head after a few days of heparin therapy is advisable to ensure haemorrhagic transformation of the brain lesion does not develop. Although long-term oral anticoagulation is needed in those patients with cardioembolic strokes, switching to oral therapy should await clinical stability for a few days.

Learning points.

• All patients with acute stroke in the setting of type B aortic dissection (AD) should receive extensive workup. One should not assume that the stroke is related to the dissection process itself.

• Cardioembolic stroke or treatment side effects are potential complications of type B AD.

• Retrograde turbulent flow, retrograde extension of the dissection and false lumen thrombus are serious consequences that could directly cause acute ischaemic strokes in the settings of type B AD.