Recent caffeine ingestion reduces adenosine efficacy in the treatment of paroxysmal supraventricular tachycardia.

OBJECTIVES: Caffeine, an adenosine receptor blocker, should theoretically reduce adenosine efficacy in the treatment of paroxysmal supraventricular tachycardia (SVT). We aimed to determine the effect of recent caffeine ingestion on the likelihood of reversion of SVT with adenosine. METHODS: This was a multicenter, case-control study of adult patients with SVT treated with adenosine between September 2007 and July 2008. The primary endpoint was reversion to sinus rhythm (SR) after a 6-mg adenosine bolus, as a function of recent (within 2, 4, 6, and 8 hours) caffeine ingestion. Caffeine ingestion data were collected using a self-administered questionnaire. RESULTS: Of 68 patients enrolled, 52 (76.5%, 95% confidence interval [CI] = 64.4% to 85.6%) reverted after a 6-mg adenosine bolus. There were no significant differences in age, sex, or daily caffeine ingestion between patients who did and did not revert (p > 0.05). However, as a group, patients who did not revert had recently ingested significantly more caffeine (p < 0.05). If caffeine had been ingested less than 2 or 4 hours before the adenosine bolus, the odds of reversion to SR were significantly reduced (odds ratio [OR] = 0.18, 95% CI = 0.04 to 0.93; and OR = 0.14, 95% CI = 0.04 to 0.49, respectively). If caffeine had been ingested less than 6 or 8 hours before the adenosine, the odds of reversion were not reduced (OR = 0.31, 95% CI = 0.09 to 1.02; and OR = 0.31, 95% CI = 0.09 to 1.08, respectively). CONCLUSIONS: Ingestion of caffeine less than 4 hours before a 6-mg adenosine bolus significantly reduces its effectiveness in the treatment of SVT. An increased initial adenosine dose may be indicated for these patients.

Initial experience with nifekalant hydrochloride (MS-551), a novel class III antiarrhythmic agent, in patients with acute extensive infarction and severe ventricular dysfunction.

Nifekalant hydrocholoride, a novel class III antiarrhythmic agent, was used as the treatment in 4 patients with extensive anterior infarction and severe ventricular dysfunction. The malignant ventricular tachyarrhythmia was effectively suppressed at a relatively low dose, without compromising the hemodynamics, indicating that this potent K+ channel blocker has therapeutic potential for acute myocardial infarction.

Innovative pharmacologic approaches to cardiopulmonary resuscitation.

The survival rate of patients undergoing cardiopulmonary resuscitation is 5 to 15%. New cardiopulmonary resuscitation treatment approaches under investigation include the use of vasopressin as a vasopressor, amiodarone for the treatment of ventricular tachyarrhythmias, and adenosine antagonists (i.e., theophylline) for bradyasystolic rhythms. More innovative approaches include the use of thyroid hormone and endothelin.