Letter to the editor: Diagnostic procedures and case related information in ICM-induced hypersensitivity

The Editor,

We have read with interest the comments of Böhm and wish to clarify the clinical aspects requested.

Our patient suffered a Type I hypersensitivity reaction during the first coronary angiography, since he developed generalised erythematous rash, areas of angio-oedema on the upper body, milder on the face and more evident on limbs (particularly hands and feet) and hypotension [1]. Nevertheless, as the patient also complained of feeling hot, chills, tremor and malaise, the reaction was not classified as an immunological Type I hypersensitivity reaction at that time and, the more common, anaphylactoid non-immunological histamine release reaction was considered more probable [2]. As diagnostic coronary angiography showed significant disease in the circumflex artery, a therapeutic coronary angiography was scheduled 4 days later for stent placement. The same iodinated contrast medium was used with the usual preventive treatment recommended for mild and moderate anaphylactoid reactions [2] and close observation of the patient. No other changes were made to the drug treatment between the first and second coronary angiographies. Magnetic resonance angiography was not considered because it is not an accurate technique to diagnose coronary artery disease owing to its low spatial resolution and motion artefacts [3].

In the second procedure, after only 20 ml of iodixanol had been infused, the patient complained of feeling hot, followed by tremor and generalised pruritic erythematous rash. The procedure was therefore stopped and, at that time, Type I iodixanol hypersensitivity was suspected and the patient was referred for allergological study.

Until recently, iodinated contrast media were believed to induce mainly non-specific immediate reactions described as erythema or flushing, feeling hot, malaise, tremor and/or nausea; only in recent years has the immune nature of many of these immediate reactions, particularly anaphylactic events, been recognised, as emphasised by Böhm [4] and other authors [5]. Where non-specific histamine-release agents, such as iodinated contrast media are concerned, true immune hypersensitivity reactions may easily be mistaken, as occurred in the first coronary angiography in our patient. In this respect, the skin and laboratory tests performed in our patient were useful to confirm the immunological nature of such events and identify the culprit drug as well as other theoretically safer iodinated contrast media for future use, if required.