Electrophysiological effects of clentiazem, a new Ca2+ antagonist, on rabbit hearts

Drugs and Brugada syndrome patients: review of the literature, recommendations, and an up-to-date website (www.brugadadrugs.org)

BACKGROUND

Worldwide, the Brugada syndrome has been recognized as an important cause of sudden cardiac death in individuals at a relatively young age. Importantly, many drugs have been reported to induce the characteristic Brugada syndrome-linked ECG abnormalities and/or (fatal) ventricular tachyarrhythmias.

OBJECTIVE

The purpose of this study was to review the literature on the use of drugs in Brugada syndrome patients, to make recommendations based on the literature and on expert opinion regarding drug safety, and to ensure worldwide online and up-to-date availability of this information to all physicians who treat Brugada syndrome patients.

METHODS

We performed an extensive review of the literature, formed an international expert panel to produce a consensus recommendation to each drug, and initiated a website (www.brugadadrugs.org).

RESULTS

The literature search yielded 506 reports for consideration. Drugs were categorized into one of four categories: (1) drugs to be avoided (n = 18); (2) drugs preferably avoided (n = 23); (3) antiarrhythmic drugs (n = 4); and (4) diagnostic drugs (n = 4). Level of evidence for most associations was C (only consensus opinion of experts, case studies, or standard-of-care) as there are no randomized studies and few nonrandomized studies in Brugada syndrome patients.

CONCLUSION

Many drugs have been associated with adverse events in Brugada syndrome patients. We have initiated a website (www.brugadadrugs.org) to ensure worldwide availability of information on safe drug use in Brugada syndrome patients.

Effects of ajmaline on rate-dependent atrioventricular node properties. Potential role in experimental atrioventricular re-entrant tachycardia

Ajmaline is a well-known atrioventricular (AV) node depressant agent, but its effects on functional properties of the AV node and on experimental AV re-entrant tachycardia have not been explored. The aims of the present study were (1) to determine whether ajmaline administration modifies the rate-dependent properties of the AV node and (2) to correlate these changes with the actions of ajmaline on an in vitro model of AV re-entrant tachycardia. Selective stimulation protocols and mathematical formulations were used to quantify independently AV node recovery, facilitation, and fatigue in 10 isolated rabbit AV nodes. Ajmaline decreased facilitation and fatigue and had no significant effect on AV node recovery. The most important effect of ajmaline was rate-induced prolongation of AV node effective refractory period, resulting in a greater increase in tachycardia cycle length. AV re-entrant tachycardia was sustained when AV effective refractory period divided to tachycardia cycle length was less than 1, ajmaline suppressed AV re-entrant tachycardia by increasing the slope of the AV effective refractory period divided to tachycardia cycle length versus tachycardia rate relation, causing the critical ratio of 1 to be attained at a slower rate. A mathematical model incorporating quantitative descriptors of recovery, facilitation, and fatigue accounted for changes in nodal conduction time, AV effective refractory period, tachycardia cycle length, and AV effective refractory period divided to tachycardia cycle length under all conditions. It can be concluded that (1) ajmaline increases AV conduction time, decreases AV node fatigue, and facilitation, without altering AV node recovery. (2) Ajmaline significantly prolongs AV effective refractory period in a rate-dependent manner. (3) These changes play a role in ajmaline's actions on experimental AV re-entrant tachycardia. Ajmaline's ability to terminate re-entrant supraventricular tachycardia may be due, at least in part, to its ability to amplify the rate-induced prolongation of the nodal refractory period.