Two patients admitted to hospital because syncope and chest pain are presented. In both patients, hyperventilation test caused severe myocardial ischaemia (ST segment elevation) and sudden development of presyncopal sustained ventricular tachycardia which immediately responded to intravenous nitroglycerin. The relationship between coronary vasospasm and sudden death secondary to polymorphic ventricular tachycardia is discussed. Also, the usefulness of the hyperventilation test to detect this problem and to monitor its therapeutic response is addressed.