The cold pressor test (CPT) has been used as a functional endothelial test of the coronary arteries and also for assessing pain threshold and tolerance. Approximately 4,500 CPTs were performed in 31 studies published in 2008. In a CPT, the subject’s hand or foot is placed in ice water, producing a pain sensation. Nociception induces the sympathetic stimulation and release of noradrenalin and adrenalin from the adrenal medulla, which increase heart rate, arterial blood pressure, and myocardial oxygen demand. Secondarily, coronary flow and epicardial diameter are affected, and this change, depicting the integrity of the coronary circulation, can be assessed with various methods.
CPTs are generally well tolerated. Nevertheless, in rare situations, we have detected a paradoxical vasovagal reaction, which leads to orthostatic syndrome, bradycardia, and asystole. However, the incidence of these events is unknown.
To study the incidence and severity of such adverse effects of CPT, we collected retrospectively all CPT data from 3 academic research facilities (Turku University Hospital, the University Hospital of Geneva, and Verve) and studied all adverse events ( Table 1 ). Of 316 subjects studied and 763 tests performed, we found 5 vasovagal reactions, yielding an incidence of 1.6%. However, only 1 of these events was so serious that the test had to be interrupted. This subject had 60-second asystole that began after 50 seconds of hand immersion. Asystole resolved spontaneously while receiving cardiopulmonary resuscitation. Later, this subject experienced the same kind of asystole in daily life, and consequently, a pacemaker was implanted for sick sinus syndrome. In the other patients, milder reactions consisted of orthostatic syndrome, bradycardia, and diaphoresis after the examination. Thus, the incidence of serious vasovagal reactions with asystole was 0.3%. In those patients with no adverse events in the first CPT, the repeated tests (n = 11) occurred without vasovagal reactions. We found no difference between the different patient groups of healthy volunteers in the incidence of events.
