Severe obstructive sleep apnoea, aortic dissection and aortopulmonary fistula in a 56-year-old patient with syncope

Abstract

We present a case of a 56-year-old patient with obstructive sleep apnoea (OSA) presenting with acute decompensated heart failure and signs of cardiogenic shock. Echocardiography and CT imaging led to the diagnosis of acute type A aortic dissection (AD) complicated by aortopulmonary fistula (APF). The patient underwent successful surgical repair with complicated postoperative course including pulseless electrical activity arrest. This case highlights the underappreciated role of untreated OSA as a risk factor for AD. Furthermore, it presents an opportunity to review APFs as a rare complication of AD. We discuss the available evidence linking OSA and AD, review currently reported cases of APF, briefly outline the haemodynamics of this acute left-to-right shunt and discuss management of this rare but deadly complication.

Background

Obstructive sleep apnoea (OSA) is the most common pathology of sleep-disordered breathing, characterised by repeated collapse of the upper airway during sleep, leading to cyclic occurrences of hypopnoea and apnoea. The prevalence of OSA has been estimated at 22% in men and 17% in women.¹ As obesity rates increase around the world, an increase in OSA prevalence over time has also been recognised, with some countries estimating a prevalence greater than 50%.² Recent data suggest that worldwide, 425 million individuals suffer from moderate to severe disease. These figures stress the increasing importance of understanding the complications of OSA and instituting patients on appropriate therapy.

Aortic dissection (AD) can be a fatal and dramatic complication of cardiovascular disease. This can be further complicated by the occurrence of an aortopulmonary fistula (APF), which has a very bleak prognosis in the absence of prompt surgical repair.³ If the condition is successfully recognised and managed, the chance of survival is good; however, diagnosis is made postmortem in over 50% of cases of AD. It can occur through a variety of mechanisms; as a complication of aortic surgery, as a result of degenerative aortic disease in the setting of sepsis or trauma, or of inherited aortopathies like Marfan’s syndrome and other connective tissue diseases.^{3 4} However, it can also occur spontaneously as a complication of an AD as in the case presented. The diagnosis can be made on targeted echocardiography or CT imaging; however, in few cases, the diagnosis may elude imaging and only be made at surgery or at postmortem.⁵

Case presentation

A 56-year-old man with a history of untreated OSA, hypertension, persistent atrial fibrillation and morbid obesity presented to the emergency room with a primary complaint of dyspnoea. He had experienced a syncopal episode 3 days prior to his presentation associated with some chest pain. The patient initially attempted to manage at home but experienced progressive worsening of his shortness of breath. Additionally, he noted no urine output during that time. His initial vitals were noted for an irregularly irregular pulse of 130, respiratory rate of 30, blood pressure of 121/82 mm Hg on the right arm and oxygen saturations of 84% on room air. He was placed on BiPAP (Bi-level positive airway pressure) with an FiO₂ of 45% resulting in an increase in his saturations to 92%. Physical examination noted increased work of breathing, with difficulty completing full sentences. Cardiovascular examination was remarkable for a rapid irregular pulse and pitting oedema to the knees. Very soft S1 and normal S2 were appreciated on auscultation with no added heart sounds or murmurs. Lung fields had crackles bilaterally. The patient was in rapid atrial fibrillation.

His medications on presentation included digoxin 0.125 mg, diltiazem 240 mg, furosemide 40 mg, rivaroxaban 20 mg and tamsulosin 0.4 mg. He had previously refused continuous positive airway pressure (CPAP) therapy for his OSA, citing facial discomfort.

He had no family history or aortic aneurysm, AD or aortic rupture. He had never been screened previously for aortic aneurysm.

Investigations

Initial laboratory work revealed a troponin of 0.93 ng/mL, peaking at 1.09 ng/mL (normal <0.4 ng/mL), an elevated white cell count at 21.5×10⁹/L with neutrophilic predominance and markedly elevated creatinine of 490 μmol/L. Venous blood gas demonstrated respiratory acidosis with type 2 respiratory failure, with a pH of 7.14, pCO₂ 56 mm Hg and bicarbonate 20 mmol/L. Lactate was also elevated at 4.7 mmol/L. Liver function test demonstrated hepatocellular pattern of injury with alanine transaminase (ALT) 1659 u/L, aspartate aminotransferase (AST) 1954 u/L, alkaline phosphatase (ALP) 141 u/L and gamma glutamyl transferase (GGT) 146 u/L.

ECG revealed atrial fibrillation with rapid ventricular response in the 130–140 s range. There were no ST-T changes to suggest acute ischaemia.

Chest radiograph showed cardiomegaly and pulmonary oedema. The width of the mediastinum could not be commented on as it was a portable film.

A limited transthoracic echocardiogram was performed; it was remarkable for a dilated right ventricle (RV) with moderate systolic dysfunction and flattened interventricular septum suggestive of RV overload. Pulmonary artery systolic pressure was estimated at 74 mm Hg. Left ventricular systolic function was reported as grossly preserved. Subsequently, a bubble study was requested in view of presumed pulmonary hypertension; although no shunt was identified, this study did reveal a dilated proximal aorta with a linear hyperdensity concerning for a dissection flap.

CT angiogram

This showed a dilated (52 mm in diameter) ascending aorta with moderate anterior/anteromedial supravalvular dissection flap beginning at the sinotubular junction, associated with 1.3 cm diameter rupture into a large 7.7×5.0×4.4 cm (aortopulmonary (AP) by craniocaudal by transverse) pseudoaneurysm that moderately compressed the main pulmonary artery. Additionally, there was a 1.2 cm diameter fistula communicating with the origin of the right main pulmonary artery, representing an acquired APF, thought to be secondary to AD (figures 1 and 2). Moderately dilated the right atrium (RA) and RV, and mildly dilated the left atrium and left ventricle (LV). A small 7 mm diameter pericardial effusion was seen to overlay the LV lateral wall.

Figure 1.

CT angiogram showing rupture (yellow arrow) of the aorta into the pseudoaneurysm (red arrow), compressing the main pulmonary artery (purple arrow).

Figure 2.

CT angiogram showing fistulisation of the right main pulmonary artery (yellow arrow), contained rupture of aorta (purple arrow) into pseudoaneurysm compressing the main pulmonary artery (red arrow).

The patient was referred for emergent surgical repair of AD and fistula.

Transoesophageal echocardiogram

Emergent pre-op transoesophageal echocardiogram (TOE) showed normal LV size and function. The RV was dilated with mild hypokinesis. It confirmed the origin of the dissection at the sinotubular junction with associated fistula to the pulmonary artery. The ascending aorta was 52 mm (figures 3 and 4, videos 1 and 2). No haemodynamically significant valvulopathy was noted. Perioperative TOE confirmed the above findings (figures 3 and 4, videos 1 and 2).

Figure 3.

Transoesophageal echocardiogram showing fistula (red arrow) from the aorta (yellow arrow) to the right main pulmonary artery (purple arrow) on the left. Abnormal flow from the aorta to the pulmonary artery shown on the right.

Figure 4.

Transoesophageal echocardiogram showing a dissection plane starting at the sinotubular junction (red arrow), a true aortic lumen (purple arrow), the false lumen (blue arrow) and the aortic valve (yellow arrow).

Video 1.

Download video file ^{(511KB, mp4)}

DOI: 10.1136/bcr-2021-244029.video01

Video 2.

Download video file ^{(419.5KB, mp4)}

DOI: 10.1136/bcr-2021-244029.video02

Immediate postoperative TOE confirmed closure of the fistula (video 3).

Video 3.

Download video file ^{(469.2KB, mp4)}

DOI: 10.1136/bcr-2021-244029.video03

Differential diagnosis

Based on the imaging findings, cardiogenic shock/congestive heart failure secondary to type A AD complicated by APF was diagnosed. Acute left-to-right shunt causing pressure and volume overload of the RV was the haemodynamic consequence of the same. The presence of a small pericardial effusion on the lateral wall was concerning for the dissection extending into the pericardium. However, the patient did not show any signs of cardiac tamponade as his haemodynamic status was preserved on presentation.

Treatment

The patient was treated for his congestion with intravenous furosemide. However, he remained anuric and required a short course of haemodialysis for ultrafiltration. After identification of the dissection on imaging, the patient was referred for emergent repair. His condition rapidly deteriorated from a respiratory and haemodynamic perspective, necessitating intubation and inotropic support with epinephrine and norepinephrine infusions. After careful consideration and discussion of management approach with several colleagues, he was taken to the operating room for sternotomy and repair of the dissection of the hemiarch and ascending aorta, with pericardial patch repair of the main pulmonary artery.

Outcome and follow-up

Postoperatively, the patient was transferred to the intensive care unit in stable condition; but unfortunately, his course was complicated by catastrophic postoperative complications. He suffered an upper gastrointestinal (GI) bleed, with no identified source on upper endoscopy. He was also treated for a Staphylococcus epidermidis graft infection with vancomycin. On post-op day 10, he suffered a pulseless electrical activity (PEA) arrest with return of spontaneous circulation after 15 min of resuscitative effort. CT pulmonary angiogram was negative for pulmonary embolism, and the arrest was attributed to hypovolaemia. Post-op bleeding and myocardial infarction were ruled out. He eventually improved, being weaned off pressors and successfully extubated. His renal function recovered. He was started on overnight CPAP for OSA. He was in atrial fibrillation but responded well to low-dose metoprolol. He was also on apixaban to prevent thromboembolic events. He is awaiting discharge after optimal physiotherapy and rehabilitation.

Surgical pathology

Surgical pathology of the specimen showed an intimomedial tear in the aortic wall, entering a false lumen which stemmed from one edge of the specimen to the other. Focal moderate atherosclerosis of the intima and mild-moderate patchy fatty streaking were present. There was fine wrinkling of the intimal surface. The adventitial soft tissues were haemorrhagic and oedematous. There was no thrombus in the false lumen. Elastin staining showed grade 3 cystic medial degeneration (CMD) with marked collagen degeneration in the specimen indicative of aortopathy. Genetic testing for inherited aortopathies has been offered to the patient.

Discussion

APF is a very rare but life-threatening complication of acute AD (less than 14 days); it is even rarer in chronic AD. Review of the pertinent literature documents only 12 cases of APFs in acute AD and 4 in chronic AD (table 1). Diagnosis is often made postmortem. We report the 13th case of APF in the setting of acute AD.

Table 1.

Summary of reported cases in the literature of aortic dissection complicated by aortopulmonary fistula

Author, year	Age	Gender	Acute or chronic	Diagnosis of fistula	Outcome
Bory et al, 197017	28	Male	Acute	Aortography	Died
McCarthy et al, 197218	54	Male	Acute	Aortography	Survived
Morris and Barwinsky, 197812	63	Female	Acute	Aortography	Died
Glanz et al, 198213	55	Male	Acute	Aortography	Died
Keenan et al, 198414	64	Male	Chronic	Aortography	Died
Large and English, 198815	73	Male	Acute	Aortography	Died
Veerbeek et al, 199219	41	Male	Acute	Doppler echocardiography and aortography	Survived
Tale et al, 199320	67	Male	Acute	Aortography	Survived
Spier et al, 199521	75	Female	Acute	Aortography	Survived
Coseli et al, 199522	62	Male	Chronic	Doppler echocardiography and aortography	Survived
Massetti et al, 199523	32	Male	Chronic	Aortography	Survived
Atay et al, 199824	73	Male	Chronic	At surgery	Survived
Piciché et al, 19985	60	Male	Acute	At surgery	Survived
Thistlethwaite et al, 200125	69	Male	Acute	Doppler echocardiography and aortography	Survived
Wellikoff et al, 201026	84	Female	Acute	Aortography	Died
Lempel et al, 201227	73	Male	Acute	Aortography	Survived
Current report, 2021	56	Male	Acute	Doppler echocardiography and aortography	Survived

APFs were initially thought to be a consequence of chronic degenerative aortic disease like atherosclerotic disease, infectious aneurysms, chronic aneurysms in various aortopathies as well as giant cell arteritis. One would imagine that the indolent nature of these pathological processes would predispose to fistulisation into adjacent anatomic structures but this is not supported by the limited literature on the subject. It is now reported increasingly in acute aortic syndromes, namely, acute AD. Fistulisation has been reported into the pulmonary artery, the RA, the RV and the pericardial cavity.^{6 7} Aortocameral fistulas refer to fistulisation of the cardiac chambers and are extremely rare.

We reflect on the pathogenesis of acute AD complicated by APF in our patient.

Untreated OSA has now been recognised as a potential risk factor in the development of AD. It has been hypothesised that OSA can lead to the development of AD and other aortic diseases by a number of mechanisms. First, OSA has been established as a cause of resistant hypertension, by blunting the nocturnal blood pressure dip, a well-recognised independent risk factor for AD.⁸ Additionally, the cyclic changes that result due to inspiratory effort against an obstructed airway led to increased intrathoracic pressures, causing additional shear stress as well as acceleration of atherosclerotic disease and inelasticity of the aortic lumen.⁹ Intrinsic positive end-expiratory pressure, also known as auto-PEEP, may result in peak airway pressure to increase to levels that may cause acute AD and death during sleep. In our patient, identified risk factors leading to this catastrophic scenario were increased body mass index (BMI), untreated OSA, suboptimally treated hypertension and aortopathy with an ascending aortic aneurysm, 52 mm.

Furthermore, frequent arousals during sleep as well as periods of intermittent hypoxia can result in frequent sympathetic nervous system activation, causing increasing levels of circulating catecholamines and potentiating oxidative stress.⁹ It should be emphasised that the consequences of activating the neurohormonal cascade have been observed to persist even 24 hours beyond the initial stimulus.¹⁰

Aortopathies are risk factors for accelerated CMD, a pathological degenerative process affecting the larger arteries and the aorta in particular. It is characterised by the accumulation of basophilic material in the media with formation of cyst-like lesions. This leads to degenerative disruptions of collagen, elastin and smooth muscles leading to weakening and fragility of the arterial wall.¹¹ Poorly controlled hypertension, untreated severe OSA and increased BMI set the stage for AD and attendant complications.

Acute fistulisation of the pulmonary artery from the dissected aorta results in an acute left-to-right shunt with pressure and volume overload of a non-compliant RV. This causes a rapid rise in pulmonary artery systolic pressure (74 mm Hg in our patient) and acute right heart failure. The RV dilates to accommodate the pressure and volume overload. This acute maladaptation compromises left ventricular filling and function and may cause further deterioration in an already compromised scenario. An acute left-to-right shunt of this magnitude would be expected to cause a continuous systolic–diastolic murmur over the precordium, very similar to that of a patent ductus arteriosus. We were not able to auscultate such a murmur in our patient for several reasons; the morbid obesity of the patient (BMI 50), as well as the fact that he was in congestive heart failure with widespread crackles causing any murmur to be inaudible. Additionally, with the rapidly rising pulmonary artery pressures, the shunt fraction may have decreased, decreasing flow turbulence and murmur intensity.

We also hypothesise that ‘contained rupture’ of the dissection into the pseudoaneurysm of the aorta, prior to fistulisation of the right main pulmonary artery, may have acted as a pressure release valve. Thus, the pulmonary artery may not have felt the full brunt of aortic haemodynamics, at least initially.

Piciché et al reported spontaneous closure of an APF in their case report.⁵ In fact, many clots had formed and filled the false lumen in their patient, resulting in fistula obliteration and shunt occlusion. This somewhat fortuitous thrombotic complication of APFs has not been reported in other case reports and may have been life-saving in this particular patient. Imaging in such a scenario may fail to demonstrate such a shunt.

Multimodality imaging has facilitated the diagnosis of APFs; curbing the need for the former gold standard, cardiac catheterisation and aortography, a challenging procedure in a haemodynamically unstable patient with the added risk of entering the false lumen and extending the dissection with fatal consequences. Aortography reveals both the AD and the left-to-right shunt and the catheter may in fact pass from the aorta to the pulmonary artery. A step-up in oxygen saturation from the RV to the pulmonary artery should raise suspicion of APF in this scenario. Swan-Ganz catheterisation, a much less daunting procedure, would yield the same information and has been reported in two cases.^12–15

In 1924, a review by Boyd indicated an occurrence of approximately 4% in postmortem autopsy of patients with aortic aneurysm of the thoracic aorta.¹⁶ Furthermore, a review published in 1999 by Piciché et al⁵ identified only 13 cases of APF in the setting of AD, of which 9 were in association with an acute AD. Remarkably, only four of these acute cases survived to discharge. They underline the fact that surgery was unsuccessful in four cases, almost 50%, of acute AD cases, emphasising the high lethality of this disease with or without surgery.12 13 15 17

In conclusion, APFs complicating acute AD pose a double jeopardy scenario with high lethality (55.5% in the series by Piciché et al). Acute fistulisation of the pulmonary artery causes a large left-to-right shunt, resulting in acute right heart failure from severe pulmonary hypertension. Management is surgical if the patient survives in the operating room. It is noteworthy that the patient discussed survived despite life-threatening complications, including APF, acute GI bleed, graft infection and PEA arrest.

Learning points.

• It is important to have a high index of suspicion for aortic dissection (AD) in a patient with severe untreated obstructive sleep apnoea (OSA), presenting with chest pain syndrome and syncope.

• This case emphasises the importance of counselling patients on treatment of severe OSA to avoid potentially life-threatening complications. Hypertension, a common and reversible risk factor for AD, in these patients should be managed aggressively as per guidelines.

• Aortopulmonary fistula (APF) results in an acute left-to-right shunt causing pressure and volume overload of the right ventricle resulting in right heart failure.

• APF must be recognised promptly in order to facilitate emergent surgical repair; failure to do so is associated with high mortality. Multi-imaging modalities may be necessary so as not to miss the diagnosis.

• Emergent surgery, a daunting undertaking in such scenarios, offers the only hope of survival. Mortality remains high.

Ethics statements

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