Acute leg pain in a 73-year-old man

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Problem 24 Acute leg pain in a 73-year-old man

Robert Fitridge

You are relaxing in a comfortable chair in the doctors’ mess, looking at the clock ticking towards the end of your shift when your thoughts are interrupted by a call from the ward.
The nurse would like you to see a 73-year-old man who is complaining of sudden-onset acute severe pain in his left leg. Two days earlier he had been admitted to hospital with an anterior myocardial infarction.

Q.1

What diagnoses go through your head as you head for the ward?

When you see the patient, you find him distressed with pain. He tells you the pain in his left leg came on abruptly about 40 minutes ago. The leg now feels numb and he cannot move it. He gives no prior history of claudication.

His blood pressure is 130/80 mmHg and his pulse rate 100 (irregularly irregular). Examination of the chest is unremarkable. There are no abnormalities in his abdomen. His femoral pulses are of good volume, the pulses in his right leg can all be felt. There are no pulses to be felt below the groin on the left side. The left leg is not swollen, but pale and cool to the touch.

Q.2

What do you think has happened? What further information would you like?

You are handed his in-patient notes. He had presented with 7 hours of chest pain. Work-up showed an acute anterior myocardial infarction. As his pain had subsided and he had developed Q waves in the anterior leads, he was not given any thrombolytic therapy.

He was immediately given oral aspirin and betablockers before being transferred for close monitoring in the coronary care unit. He remained there for 2 days before moving to the general ward. Now, 4 days since his admission, he has been slowly mobilizing. He was initially prescribed subcutaneous low molecular weight heparin, but you note on the drug chart that this was not continued on the ward since returning from coronary care.

His myocardial infarction was complicated by atrial fibrillation, with a rapid ventricular response rate on day 1. He had no ventricular arrhythmias and was treated with digoxin resulting in good rate control. He does not have any other significant past medical history.

Q.3

What would you like to do now?

An investigation is performed. One of the results is shown in Figure 24.1.

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Figure 24.1

Q.4

What is this investigation? What does it show?

Q.5

What would you like to do now?

The patient underwent thrombolysis of the embolus radiologically using the ‘pulse-spray’ technique that often results in rapid clot lysis. Standard thrombolytic techniques would take 4–20 hours to achieve clot dissolution, and it was thought this patient’s leg was unlikely to be viable if revascularization took this length of time. The ‘pulse-spray’ technique is much more rapid. After 1 hour of urokinase pulsing, the angiogram was repeated (Figures 24.2 and 24.3).

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Figure 24.2

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Figure 24.3

Q.6

What do these new angiograms show?

The patient was anticoagulated with heparin and plans were made to continue anticoagulation on oral warfarin for at least 6 months, or possibly indefinitely depending on his atrial rhythm.

Answers

A.1 There are few possible causes of an acute severely painful leg. The most likely diagnosis is one of arterial embolus to the left leg. Other less likely possibilities include thrombosis of a pre-existing arterial atherosclerotic plaque, an extensive deep vein thrombosis of the left leg or an aortic dissection extending into the left leg arteries. A muscle haematoma if on thrombolytic or anticoagulant therapy is also a possibility.

A.2 He has acute ischaemic limb. His leg is pale, pulseless, painful and ‘perishing’ with cold. In addition he may have paraesthesia and paralysis of the affected limb – the classic six Ps.

The presence of a femoral pulse on the left indicates that the occlusion is likely to be in the superficial femoral or popliteal artery.

The sudden onset, lack of previous history and recent myocardial infarction all suggest that this is an embolic phenomenon. He has most probably thrown off an embolus from the heart which has lodged in the femoral artery. Such an embolus would have arisen from a mural thrombus at the site of infarction (in the left ventricle) or dislodged from clot in an atrium that is fibrillating. A less likely cause in this instance would be acute thrombosis of an atherosclerotic lesion in the femoral or popliteal artery.

After your initial assessment you will want to examine the notes looking for information about his post-myocardial infarction course, the timing and duration of arrhythmias and whether or not he has been anticoagulated.

A.3 You should contact the vascular surgeons immediately. Emergency arteriography or CT angiography will be required to define the site and extent of obstruction.

Unless angiography can be performed without delay, you should consider anticoagulating the patient with unfractionated intravenous heparin. Baseline coagulation studies (APTT) must be performed before starting the heparin. Heparin is dosed by weight and must be adjusted to maintain the APTT in the therapeutic range. A standard loading dose for an adult would be 5000 units, followed by an infusion of 1000 units/hour. Blood should also be collected for a complete blood picture, electrolytes and type and cross-matching. This patient is not a good candidate for general anaesthesia, but embolectomy or radiological intervention can be performed under local anaesthetic.

A.4 This is a digital subtraction angiogram, which demonstrates a filling defect in the left popliteal artery above the knee. At the level of the obstruction, there is a large collateral seen filling the distal popliteal vessel. This is consistent with a popliteal embolus. The proximal vessels are normal.

A.5 This patient has a threatened ischaemic leg requiring revascularization within 4 hours (see Revision points at end of chapter).

Management options include:

• Surgical removal of the embolus which could be done under local anaesthetic in some cases.
• Thrombolytic therapy. Possibilities include a rapid clot thrombolysis technique (‘pulse-spray’) or suction thrombectomy as a percutaneous radiological procedure. Urokinase and heparin can be ‘pulsed’ directly into the clot via a catheter traversing the thrombus.

A.6 The angiograms performed after 1 hour of thrombolysis demonstrated a good radiological result. The clot had lysed and there is satisfactory revascularization of the distal vessels. The filling defect was no longer visible.

Revision Points

Acute Lower Limb Ischaemia

Incidence

Approximately 2 : 10 000 population per year.

Aetiology

• Embolus – almost always due to mural thrombus post myocardial infarction or secondary to arrhythmia (occasionally can be from valvular heart disease or proximal aortic disease, e.g. aneurysm).
• Acute thrombosis of diseased artery.
• Bypass graft thrombosis.
• Trauma (e.g. knee dislocation, tibial plateau fracture).

Classification

Table 24.1 outlines classification criteria.

Table 24.1 Classification of severity in limb ischaemia

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Investigations

• Following examination for pulses and assessment of severity of ischaemia, vascular surgeons should be consulted, and ECG, bloods, group and match performed. Doppler pressures (ankle–brachial index) may be performed. Anticoagulation should be commenced unless angiogram can be performed promptly.
• Also search for other sites of embolization (common sites include other leg, arms, brain and gut).
• Vascular imaging (ultrasound, CT angiography or angiography) will demonstrate the level of occlusion and may clarify the aetiology of acute ischaemia.

Management

Therapy will depend on aetiology, severity of ischaemia and patient co-morbidities.

Options:

• Surgical thrombectomy under local, spinal or general anaesthetic (usually performed under local anaesthetic in the situation discussed).
• Thrombolysis performed radiologically (using urokinase or ± tissue plasminogen activator: TPA). Advanced catheter techniques such as suction thrombectomy or pulse-spray thrombolysis may be used in selected cases and decrease time taken to re-perfuse the lower limb (particularly in cases of profound ischaemia – category IIb).
• Bypass graft thrombectomy, thrombolysis or replacement for occluded (usually prosthetic) grafts.
• Surgical repair of artery ± bone fixation (for trauma).
• Immediate amputation for unsalvageable limb may be required.
• Occasionally palliative care is appropriate in selected cases.

Note: fasciotomy of lower limb muscle compartments may need to be considered if ischaemia is profound and of lengthy duration prior to revascularization.

Outcomes

• Depend on severity and duration of ischaemia, and co-morbidities.
• Mortality rates are still 15–30%.
• Amputation rates in survivors 20–30%.

Issues to Consider

• What are the risks of surgery after a myocardial infarction?
• What are the other short- and long-term vascular complications of myocardial infarction? How may this patient’s risk have been minimized?

Further Information

Norgen L., Hiatt W.R., Dormandy J.A., et alTASC II Working Group. Inter-Society Consensus for the Management of Peripheral Arterial Disease (TASC II). Journal of Vascular Surgery. 2007;45:S1-S67.

Ouriel K. Thrombolytic therapy for acute arterial occlusion. Journal of the American College of Surgeons. 2002;194:S32-S39.

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