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| Publications [#175329] of Robert A Malkin
Papers Published
- De Jongh, Amy L. and Ramanathan, Vijaya and Hoffmeister, Brent K. and Malkin, Robert A., Left ventricular geometry immediately following defibrillation: shock-induced relaxation.,
Am J Physiol Heart Circ Physiol, vol. 284 no. 3
(March, 2003),
pp. H815--H819, ISSN 0363-6135 [12414439], [doi]
(last updated on 2010/05/26)
Abstract:
A previous two-dimensional (2D) ultrasound study suggested that there is relaxation of the myocardium after defibrillation. The 2D study could not measure activity occurring within the first 33 ms after the shock, a period that may be critical for discriminating between shock- and excitation-induced relaxation. The objective of our study was to determine the left ventricular (LV) geometry during the first 33 ms after defibrillation. Biphasic defibrillation shocks were delivered 5-50 s after the induction of ventricular fibrillation in each of the seven dogs. One-dimensional, short-axis ultrasound images of the LV cavity were acquired at a rate of 250 samples/s. The LV cavity diameter was computed from 32 ms before to 32 ms after the shock. Preshock and postshock percent changes in LV diameter were analyzed as a function of time with the use of regression analysis. The normalized mean pre- and postshock slopes (0.2 +/- 2.2 and 3.3 +/- 7.9\% per 10 ms) were significantly different (P < 0.01). The postshock slope was positive (P < 0.005). Our results confirm that the bulk of the myocardium is relaxing immediately after defibrillation.
Keywords:
Animals • Cardiac Volume • Dogs • Echocardiography • Electric Countershock • Electrocardiography • Electrophysiologic Techniques, Cardiac • Heart Ventricles • Time Factors • Ventricular Fibrillation
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