Arnar DO, Xing D, Martins JB. Alpha-2 adrenergic antagonism enhances risk of ventricular tachycardia during acute ischemia.
SCAND CARDIOVASC J 2008;
41:378-85. [PMID:
17852790 DOI:
10.1080/14017430701487713]
[Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
Abstract
OBJECTIVE
In this study we tested the hypothesis that alpha-2 adrenergic antagonism could facilitate induction of previously non-inducible ventricular tachycardia (VT) during acute ischemia. Previous reports suggest that VT during ischemia may be modulated by (alpha-2 adrenergic agonists.
DESIGN
The left anterior descending artery was occluded after instrumentation of the ischemic risk zone with 21 multipolar plunge needles, each recording 6 bipolar electrograms. Three dimensional mapping characterized the mechanism of VT induced with extrastimuli.
RESULTS
Of 16 non-inducible dogs included, eight which were given the alpha-2 adrenergic antagonist yohimbine all had inducible VT, while all eight in the control group remained non-inducible (p < 0.05). Six of the VTs were of focal Purkinje origin. The cycle length of the VTwas 119 +/- 4 ms. Mean arterial pressure (81+/- 8 to 82 +/- 8 mmHg, p = ns), ventricular effective refractory period (146 +/- 6 to 144 +/- 5 ms, p = ns) and ischemic zone size (55 +/-6% vs. 61 +/- 4%, p = 0.45) were not altered by yohimbine indicating minimal central or pre-junctional effects of the drug.
CONCLUSIONS
Yohimbine facilitates induction of VT, especially those with focal Purkinje fiber origin, suggestive of an effect mediated through antagonism of post-junctional alpha-2 adrenoceptors on Purkinje fibers.
Collapse