High-output cardiac failure secondary to high-output arteriovenous fistula: investigations, management and definitive treatment

Abstract

A 32 year-old woman was admitted to our institution with progressive dyspnoea. Her medical history was notable for end-stage renal failure secondary to chronic pyelonephritis, and she had undergone a cadaveric renal transplant in 2010. This had been preceded by haemodialysis treatment via a radiocephalic arteriovenous fistula. Her diagnostic evaluation was remarkable for pulmonary hypertension. A subsequent doppler ultrasound of her arteriovenous fistula revealed a blood flow of 3 L/min. This is consistent with a high output fistula. Echocardiography demonstrated an improvement in pulmonary artery pressure with occlusion of the fistula. After multidisciplinary discussion, a decision was made to surgically tie off her fistula. The patient experienced immediate improvement in her shortness of breath along with resolution of pulmonary hypertension on echocardiography. This case highlights the rare complication of high output cardiac failure from a dialysis fistula and its successful surgical management.

Background

This case highlights a rare, but clinically significant, complication of high output arteriovenous fistulas. It illustrates a strategy for diagnosing and managing fistula-related high output cardiac failure.

Case presentation

A 32 year-old woman was admitted to our institution with a 2-week history of progressive shortness of breath.

She had a significant medical history of end-stage renal failure secondary to chronic pyelonephritis and had undergone a cadaveric renal transplant in 2010. Prior to transplantation, she had undergone haemodialysis through a proximal left radiocephalic arteriovenous fistula. Her renal transplant surgery was complicated by flash pulmonary oedema requiring a stay on intensive care. In 2012, she was investigated for reduced graft function, which was attributed to chronic urinary tract infections. Following this episode, her creatinine stabilised at a baseline of 190–200 µmol/L.

No other significant medical history was reported, and the patient’s medication list on admission was as follows; Prograf 4 mg two times per day, mycophenolate 1 g two times per day, amlodipine 5 mg/day, Aranesp 30 ug/week, bisoprolol 5 mg/day, calcium acetate 1 g three times a day with meals, ranitidine 150 mg/day, sodium bicarbonate 2 g two times per day, prednisolone 30 mg/day (reducing regime from general practitioner for wheeze and dyspnoea).

The patient presented with shortness of breath, which had started 1 month prior to admission, having initially begun after her general practitioner prescribed a course of flucloxacillin for a paronychia. Her dyspnoea was worse on exertion with an associated wheeze and tightness in the chest. She denied pleuritic chest pain, palpitations, orthopnoea or paroxysmal nocturnal dyspnoea. There were no reports of cough, sputum production, fever or night sweats to suggest an infective or neoplastic cause for her symptoms.

Observations on admission demonstrated a respiratory rate within normal limits at 16/min with oxygen saturations of 98% on room air. Blood pressure was raised at 186/105 mm Hg with a heart rate of 115 beats/min. Tympanic temperature was 36.7°C. On auscultation of the praecordium, she was found to have a pansystolic murmur, loudest over the left lower sternal edge, and there was evidence of a raised jugular venous pressure. The combination of these clinical signs was suggestive of tricuspid regurgitation. Respiratory examination was unremarkable and abdominal examination revealed only a mass in the right iliac fossa consistent with the known renal transplant. There was a proximal left radiocephalic arteriovenous fistula in situ.

Investigations

A number of investigations were requested to investigate the dyspnoea. Preliminary investigations were undertaken including an ECG which demonstrated sinus tachycardia with a normal cardiac axis and no evidence of ischaemia. A chest radiograph was reported as showing minor pulmonary vascular congestion.

Routine blood tests revealed a microcytic anaemia with a haemoglobin of 94 g/L (70 g/L at its lowest during admission) with a mean corpuscular volume of 82.5 fL. Her platelet count and white cell count were normal. C-reactive protein was less than 5. Haematinics revealed slightly raised B₁₂ levels at 865 ng/L with a normal folate of 7.5 µg/L. Iron studies revealed a ferritin of 613 µg/L, with iron 10.0 µmol/L, transferrin 1.87 g/L, total iron binding capacity 43 µmol/L and saturation of iron 23%. Renal function was impaired with a sodium of 138 mmol/L, potassium 5.0 mmol/L, bicarbonate 16 mmol/L, urea 21.7 mmol/L, creatinine 381 mmol/L (baseline 201 mmol/L) and estimated glomerular filtration rate 12 mL/min/1.73 m² (baseline 25 mL/min/1.73 m²). Taken together, these results suggested an anaemia of chronic disease, most likely renal anaemia. Clotting screen was normal. Liver function tests were normal apart from a slightly raised alanine aminotransferase of 44 U/L. Thyroid function tests revealed a euthyroid state. Alpha 1 antitrypsin level was normal, along with normal blood borne virus serology. Rheumatoid factor, antinuclear antibody, anti-liver-kidney microsomal antibody, antimitochondrial antibody, anti-smooth muscle antibody, antineutrophil cytoplasmic antibody and anti-glomerular basement membrane antibody were all negative.

Given the history of exertional dyspnoea with radiographic evidence of pulmonary oedema, the patient underwent a series of cardiac investigations. A transthoracic echocardiogram was performed which showed a normal left ventricle with normal left ventricular systolic function, moderate biatrial enlargement, mild mitral regurgitation and mild to moderate tricuspid regurgitation. There was evidence of an elevated right ventricular systolic pressure of 50–60 mm Hg suggestive of pulmonary hypertension. A trivial pericardial effusion was also noted.

Differential diagnosis

The finding of pulmonary hypertension was unexpected. A low-dose ventilation/perfusion scan was performed to rule out chronic thromboembolic disease, the results of which were normal. Spirometry and later full pulmonary function testing (PFTs) were performed to investigate for pulmonary causes of secondary pulmonary hypertension. They revealed a pattern in keeping with a mild restrictive defect with minimal small airways obstruction on flow volume loops. After discussion with a respiratory physician, the findings on spirometry and PFTs were deemed most likely due to pulmonary oedema. The patient proceeded to have a CT scan of the thorax with intravenous contrast which did not show any evidence of chronic lung disease. As above, her full autoantibody and connective tissue disease screen was unremarkable.

Treatment

In light of the right-sided cardiac findings on echocardiography, the patient underwent a doppler ultrasound of her left radiocephalic arteriovenous fistula. The fistula study revealed an anastomosis of 9.2 mm, with an inflow of approximately 2.7 L/min and a reversed outflow of 700 mL/min. Flow within the fistula itself was estimated at 3 L/min, with the upper limit of normal considered to be 2 L/min in our institution. Based on this information, the patient was deemed to have a high output fistula.

With the exclusion of other causes of pulmonary hypertension, a diagnosis of high-output cardiac failure secondary to a high-output arteriovenous fistula was hypothesised. A strategy was designed to further investigate our hypothesis with repeat transthoracic echocardiography performed first with a patent fistula and then repeated while the fistula was temporarily occluded. The left-sided radiocephalic fistula was occluded using a simple disposable tourniquet.

The preocclusion echocardiogram showed a normal left ventricle with good left ventricular systolic function. There was at least moderate biatrial dilatation. Moderate tricuspid regurgitation was observed with at least moderate pulmonary regurgitation (however this was not reproducible on colour doppler). The right ventricle was reported as normal with evidence of good systolic function. Prior to occlusion of the fistula, the inferior vena cava was dilated at 2 cm with less than 50% collapse on inspiration. The estimated right atrial pressure (RAP) was 10–15 mm Hg and the estimated pulmonary arterial systolic pressure (PASP) was 58–63 mm Hg consistent with moderate pulmonary hypertension. On temporary occlusion of the fistula, the inferior vena cava reduced to 1.7 cm with more than 50% collapse on inspiration, the estimated RAP decreased to 5–10 mm Hg and estimated PASP dropped to 53–58 mm Hg. This reduction in PASP demonstrates the improved haemodynamic status of the patient following fistula occlusion.

Our cardiology colleagues were consulted for review of the preocclusion and postocclusion echocardiography findings. They advised further investigation with cardiac MRI to review the cardiac anatomy and to further evaluate for right heart failure. Cardiac MR revealed an ejection fraction of 72% with an end diastolic volume of 97 mL/m² (reference range 62–98 mL/m²) and end systolic volume of 27 mL/m² (reference range 13–37 mL/m²). Stroke volume was calculated at 70 mL/m² (reference range 43–67 mL/m²). Cardiac output was 9.8 L/min. The left and right ventricles were non-dilated with normal systolic function. Moderate tricuspid regurgitation and mild mitral regurgitation were noted again, and there was evidence of biatrial dilatation. Only the left segmental pulmonary artery was visualised, but accounting for this, pulmonary artery distensibility was calculated as normal. There was an incidental finding of bilateral pleural effusions.

The case was discussed in the nephrology and renal transplant surgery multidisciplinary team meeting where a decision was made to ligate the left radiocephalic fistula to see if there would be any improvement in the patient’s cardiac function and symptoms. The patient underwent ligation of her left radiocephalic fistula under local anaesthetic without complication. Postoperative transthoracic echocardiography showed a normal left ventricle with normal systolic function, normal diastolic function and a right ventricle with normal size and function. Repeated doppler estimated PASP at 25 mm Hg. The improvements were sustained when transthoracic echocardiography was repeated further 4 months later.

Outcome and follow-up

The patient reported a marked improvement in her shortness of breath and exercise tolerance in the first few days postoperatively. She remains clinically well and returns regularly for routine nephrology follow-up. The emphasis in this case is on the immediate improvement in PASP from occluding the fistula. The echocardiography preocclusion and postocclusion allowed a definitive management decision to be made. This was justified as the patient had no pulmonary hypertension 6 months later on routine follow-up scans. If left unchecked, these patients go on to develop dilated right hearts and right ventricular failure.

Discussion

High output cardiac failure secondary to arteriovenous fistula (AVF) is a very rare complication.¹ On creation of AVF, the patient’s cardiac output increases immediately. This is mediated by a fall in total peripheral vascular resistance and an increase in the heart’s contractility secondary to sympathetic nervous system activation.² As a result, there is a rise in stroke volume which in time leads to an increase in the right atrial and ventricular pressures.³ Few case reports have documented the long-term adverse effects of high-flow AVF on cardiac function.⁴ In addition, there are studies which have revealed resolution of elevated pulmonary arterial pressure and cardiac output following ligation of the AVF.⁵

Most experts believe that symptomatic heart failure is more likely to occur in patients with underlying cardiac dysfunction in the context of high flow AVF.⁶ In patients with normal cardiac function, most of the studies demonstrated the mean cardiac outflow remains unchanged until the AVF blood flow exceeds 2 L/min.⁷ The presence of myocardial functional reserve and myocardial adaptation may protect against high output cardiac failure.⁸ However, given the prevalence of cardiac dysfunction among patients with end-stage renal disease (cardiovascular disease 40%, left ventricular hypertrophy 75%–80%), lower AVF flow rates can cause symptomatic dysfunction.⁹

Several factors have been linked with increased risk of high-output cardiac failure. This includes: upper arm AVF with brachial artery anastomosis, male sex, access flow greater than or equal to 2 L/min, presence of anaemia and volume expansion due to water and salt retention.¹⁰ The presence of a proximal radiocephalic fistula, high flow rate of 3 L/min and anaemia were the main risk factors for the high-output heart failure in our patient.

Regular surveillance of AVF through physical examination and imaging of the AVF will enable clinicians to identify risk factors and early signs of high-output cardiac failure.¹¹ Peritoneal dialysis may be a better option in patients with heart failure given the risk of worsening symptoms associated with AVF formation, although other factors will influence this complex decision.

The prevalence of pulmonary hypertension is much higher in the dialysis population and has been estimated at 17%–50%.¹² However, there are a range of pathophysiological mechanisms that may explain this phenomenon, and it does not always follow that surgical fistula ligation is the correct treatment approach.¹³ It is therefore important that patients undergo multidisciplinary assessment by nephrology, cardiology, respiratory and vascular access surgical colleagues prior to proceeding to surgical treatment. This report demonstrates the role of fistula ligation in selected patients to treat this condition.

Learning points.

• High-output cardiac failure due to arteriovenous fistula in dialysis patients is a rare but debilitating complication.

• Identification of at-risk patients with early diagnosis and management will prevent the development of irreversible cardiac dysfunction. If left unchecked, these patients go on to develop dilated right hearts and right ventricular failure.

• This case highlighted the various risk factors, the need for a high index of suspicion and the part played by real-time cardiac imaging in the diagnosis of this condition.

• The emphasis in this case is on the immediate improvement in pulmonary artery hypertension from occluding the fistula. The echocardiography preocclusion and postocclusion allowed a definitive management decision to be made.