Usefulness of Thermography in Diagnosis of Complex Regional Pain Syndrome Type I After Transradial Coronary Intervention

ABSTRACT: Complex regional pain syndrome (CRPS) is a very rare complication of transradial coronary intervention (TRI). We present the case of a 51-year-old man who suffered severe pain of the right forearm after TRI and progressed to  type I CRPS. The patient had effort angina and underwent successful coronary artery stent deployment on the right coronary artery. After removing the hemostatic device, the patient had swelling and severe pain that was not relieved by analgesics. Continued pain progressed to allodynia, hyperalgesia, and hyperesthesia, which met the diagnostic criteria for CRPS. Electromyography showed no abnormalities in nerve conduction and thermography of the forearm showed temperature discrepancy between both forearms, which confirmed the diagnosis of CRPS. We treated the patient with sympathetic nerve block, but he still suffers from minor pain in the right forearm. This case demonstrates that unalleviated pain after TRI can progress to CRPS, and that thermography is a useful method to diagnose CRPS.

J INVASIVE CARDIOL 2013;25(9):E183-E185

Key words: complex regional pain syndrome, transradial coronary intervention, thermography

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Transradial coronary intervention (TRI) is now a widely utilized technique and is considered a relatively safe procedure compared to the transfemoral approach.¹ Distinguishing anatomical features of the radial artery puncture site, namely, its placement over the radius bone and the absence of any major veins or nerves located near the artery, provide advantages to hemostasis after the procedure.² Nonetheless, radial artery occlusion does occur, with a reported incidence of 4.4% at an early stage and 3.2% after 1 month. The incidence of radial artery hematoma has also been reported, with an incidence of approximately 5%.³ The dual vascular supply of the palmar region prevents vascular complications from resulting in pain or ischemic changes. The incidence of complex regional pain syndrome (CRPS) from vascular interventions is extremely rare; only 3 cases of CRPS after TRI have been reported in the literature.^4-6 The case presented here, which demonstrated the typical thermographic findings of CRPS, is the first report of CRPS after TRI diagnosed by thermography.

Case Report. A 51-year-old man with chronic stable angina was referred to our hospital for management of 70% tubular stenosis at the mid-portion of the right coronary artery (RCA) revealed by computerized tomographic coronary angiography at another hospital. He had a smoking history of 35 pack years and was diagnosed with diabetes and hypertension 10 years ago, which had been treated with antiglycemic (metformin 1000 mg) and antihypertensive (amlodipine 5 mg) agents. The patient’s initial electrocardiography, chest x-ray, and routine laboratory studies were all within normal limits. A TRI was scheduled for confirmative diagnosis and treatment. Allen's test of the right hand, performed before the procedure, was normal. The right radial artery was punctured and a 6 Fr radial sheath was accessed. An everolimus-eluting stent was successfully deployed at the RCA lesion without event (Figure 1). A hemostatic device (TR band; Terumo Corporation) was applied. Fifteen mL of air were inflated after removing the radial sheath and 3 mL of air were deflated every 2 hours thereafter. The TR band was removed 6 hours later without any complications. However, 4 hours after TR band removal, the patient complained of mild, dull pain and swelling at the puncture site; tramadol (150 mg) was prescribed. Three days after TRI, the patient was discharged from the hospital. One week after discharge, the patient visited an outpatient clinic with complaint of severe continuous stabbing pain at the puncture site that radiated to the right upper arm and shoulder. Swelling of the puncture site extended to the upper arm, though the right radial pulse was intact. We treated the pain with acetaminophen (975 mg) and gabapentin (1500 mg). Swelling of the arm spontaneously resolved after 1 week, but medication did not alleviate the pain. One month later, the patient complained of continuous pain in the right hand, arm, and shoulder, hyperesthesia in the right fingers, and difficulties in performing normal daily activities, such as driving and using chopsticks.

An electromyography was performed to determine nerve damage, and showed no abnormalities on either motor or sensory nerve conduction studies. An F-response was performed and showed normal latency range in all tested nerves, while a needle electromyography did not reveal evidence of abnormal resting denervation potentials for any of the tested muscles. Right brachial arteriography was performed to evaluate vascular complications and radial arterial occlusion was noted (Figure 2). Thermography was then performed to evaluate the chronic pain, which demonstrated that the temperature at the pain site was 2 °C higher than the unaffected left arm (Figure 3). Findings from thermography suggested that the chronic pain was due to reflex sympathetic tone abnormality⁷ because ischemia may lower the temperature at the pain site.⁸

Based on the diagnostic criteria established by the International Association of the Study of Pain,⁹ type I CRPS was a possible diagnosis, and thermographic findings were confirmative. The patient was treated with cervical epidural block and repeated right stellate ganglion blocks, and prescribed 1800 mg of gabapentin, 10 mg of nortriptyline, 200 mg of revaprazan, and 10 mg of hydromorphone. Twelve months after treatment, the patient was still suffering from mild pain, but improvement was noted in the patient’s ability to perform daily activities. 

Discussion. By definition, CRPS results from neuropathic pain derived from abnormalities of the sympathetic nervous system. CRPS is diagnosed by a constellation of subjective symptoms, including immobilization, continuous pain, allodynia, hyperalgesia, hyperesthesia, and vasomotor symptoms.⁹ All other conditions that would otherwise explain the degree of pain and/or dysfunction must be excluded. There are two subtypes of CRPS: type I is with no identifiable nerve injury and type II is with a history of an identifiable nerve injury.^9,10 A diagnosis of CRPS is further supported by the relatively higher temperature of the pain-affected area; increased sympathetic activity is the reason for the higher temperature.⁷ If the forearm pain was the  result of limb ischemia, thermography of the forearm should demonstrate a lower temperature.⁸ The thermographic findings of this case suggested that right radial artery occlusion did not affect the development of the intractable pain. Thermography is an effective modality for assessing increases in reflex sympathetic tone and was recently proven to have a high sensitivity and specificity in diagnosing CRPS. Two degrees Celsius higher temperature in the pain-affected area demonstrated a diagnostic sensitivity of 73% and specificity of 94%.11 

Papadimos et al⁴ reported a case of type I CRPS secondary to radial artery occlusion, after 20 hours of compression by hemostatic device (Hemaband; TZ Medical). Sasano et al⁵ also reported a case of type II CRPS that was associated with a post-TRI median nerve injury resulting from excessive compression. Lai et al⁶ reported a case of type II CRPS due to a median nerve injury after TRI, diagnosed by plethysmography, electromyography, and nerve conduction studies. There was only 1 previously reported case of type I CRPS; in that case, pain developed from prolonged and excessive compression of the puncture site and was diagnosed by the pain criteria of the International Association for the Study of Pain. None of the previous cases described remarkable arm swelling, which was a suggestive finding of hematoma. However, in this case, radial artery hematoma was the main cause of pain. Puncture site swelling after removal of the hemostatic device and extension to the upper arm suggests there was hematoma. This may result in prolonged compression of the radial artery and increased pressure in the carpal tunnel. Acute pain developed from ischemia secondary to radial artery occlusion and compression of nerves, lasted more than a week and progressed to chronic pain, which eventually aggravated to CRPS. Acute severe pain and arm swelling after TRI should be considered for compartment syndrome, but in this case, arm swelling was not so severe and resolved spontaneously. Thermography demonstrated meaningful information for confirmative diagnosis of type I CRPS in this case. 

Conclusion. We presented the first thermographically diagnosed case of post-TRI type 1 CRPS. The patient suffered intractable pain and arm swelling immediately after TRI, and was treated with analgesics. Arm swelling resolved spontaneously, but unalleviated pain lasted for a considerable time period. Allodynia, immobilization, and hyperesthesia developed in the right arm, and type I CRPS was confirmed by normal electromyography findings and abnormal thermography findings. The clinical course of the patient suggests that pain after TRI should be treated thoroughly and swelling of the puncture site should not be neglected, because it can progress to serious complications such as CRPS. Moreover, this case demonstrates that reflex sympathetic tone dysfunction can be effectively examined by thermography, a modality also helpful in diagnosing CRPS.

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