A 63-year-old male with a known history of myocardial infarction, hypertension and peripheral vascular disease is admitted with breathlessness.

A 63-year-old male with a known history of myocardial infarction, hypertension and peripheral vascular disease is admitted with breathlessness. The blood pressure measured 158/96 mmHg. Blood results are shown.below:
Sodium 137 mmol/l, Potassium 4.5 mmol/l
Urea 11 mmol/l, Creatinine 130 mmol/l
Troponin T <0.1ng/l (NR <0.1 ng/l)
Arterial gases (room air): pH 7.31, PaCO2 6.4 kPa, PaO2 7.1 kPa, Bicarbonate 16 mmol/l
Chest X-ray Severe pulmonary oedema
ECG LBBB
Urinalysis Protein nil Blood nil

He was treated with diuretics and then commenced on an ACE inhibitor but after 72 hours the urea was 20 mmol/l and creatinine was 250 mmol/l. Echocardiography revealed mild impairment of left ventricular function.

What is the most probable cause for his presentation?
a. Myocardial infarction.
b. Hypertensive cardiomyopathy.
c. Renal artery stenosis.
d. Cardiac tachycarrhythmia.
e. Myocardial dysfunction secondary to acidosis.

Answer:
 c. Renal artery stenosis.

Discussion: The patient presents with acute pulmonary oedema. He has a background history of ischaemic heart disease, peripheral vascular disease and hypertension. The differential diagnosis is between heart failure secondary to hypertensive heart disease, myocardial infarction or flash pulmonary oedema secondary to renal artery stenosis. The possibility of renal artery stenosis should always be considered in a patient with peripheral vascular disease and impaired renal function.
The serum cardiac troponin is not raised, excluding myocardial infarction.
The left ventricular function is only mildly impaired and should not cause such severe pulmonary oedema unless the patient suffered an episode of myocardial stunning due to severe ischaemia resulting from major atheromatous disease in the proximal left coronary artery, or a very rapid tachyarrhythmia.
The diagnosis of renal artery stenosis is evident by the doubling of serum creatinine within three days of starting an ACE inhibitor.
Flash pulmonary oedema is a recognized complication of renal artery stenosis due to diastolic dysfunction from chronic hypertension. Presumably labile hypertension and salt and water retention through activation of the renin–angiotensin–aldosterone system are responsible. Flash
pulmonary oedema is usually a feature of bilateral renal rather than unilateral renal artery stenosis. The diagnosis can be made using low-contrast CT scan of the kidneys or magnetic resonance angiography of the renal arteries.

The causes of simultaneous cardiac and renal failure are given below.
• Chronic hypertension
• Diabetes mellitus
• Generalized atherosclerosis (coronary and reno-vascular disease)
• Polyarteritis nodosa and other vasculitides
• Systemic sclerosis
• Antiphospholipid syndrome
• Infective endocarditis
• Amyloidosis
• Ethylene glycol poisoning