Repolarization inhomogeneities in ventricular myocardium change dynamically with abrupt cycle length shortening.

• DOI: 10.1161/01.cir.84.3.1333
• Publication Date: 2012-06-12T00:01:09Z
• Authors: D S Rosenbaum; D T Kaplan; A Kanai; L Jackson; H Garan; R J Cohen; G Salama
• Keywords: Beat (acoustics); Optical mapping; Hypoxia; Ventricular Repolarization

BACKGROUND In single heart cells, abrupt changes in stimulation rate elicit complex alterations repolarization. The effects of change on dispersion repolarization, however, have not been well characterized. METHODS AND RESULTS To determine the cycle length (CL) shortening spatial inhomogeneity repolarization a syncytium ventricular 124 action potentials were simultaneously recorded from Langendorff-perfused guinea pig hearts using high-resolution optical mapping with voltage-sensitive dye. distribution potential durations (APDs) mapped during each cardiac was used to calculate mean APD and index (DI), defined as variance distribution. After abruptly CL 500 300 msec, declined exponentially normoxic controls (by 23 +/- 3 p less than 0.0001). This response characterized by beat-to-beat oscillations that synchronized at all sites. 30 minutes hypoxia, decreased 175.0 13.3 76 25.7 msec. However, lowered only an additional 6 no longer throughout ventricle. controls, DI significantly (-51.0 6.8%, 0.01) sixth post-CL beat then recovered 15-20 beats). contrast, failed decrease hypoxia (+7.1 23%). Two mechanisms for transient decline identified: synchronous diminution apical-to-basal gradient. CONCLUSIONS These data demonstrate measured DI, dynamically shortening. Furthermore, hypoxic ventricle does attenuate after thereby lacks physiological expected diminish vulnerability arrhythmias.