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| The "Heart Group" at IISc: (standing) Ashwin (left) and Sitabhra (right); (sitting) Rahul. |
Ventricular fibrillation (VF) is the implicating factor behind a majority of cases of `Sudden Cardiac Death' in which the heart goes into abnormal beating - with extremely rapid and spatio-temporally irregular oscillations. In the absence of coherent pumping action, the heart is not able to supply blood (and hence, oxygen and nutrients) to the brain. Unless prompt action is taken to alter this situation - death usually results in a matter of minutes. VF is usually treated through the injection of appropriate drugs and electrical defibrillation. Unfortunately, both methods leave much to be desired.
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Fig. 1. A spiral wave beginning to break up (T = 880 ms.). |
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Fig. 2. Evolution of spatio-temporal chaos from a broken spiral wave to a spiral turbulent state. The e field is shown at times T = 990 ms, 1100 ms, 1210 ms and 1320 ms. |
We have developed a defibrillation method where very small amplitude perturbations ( of the order of tens of mV) are applied along a geometric arrangement of control wires. A control pulse applied for a small duration ( of the order of 100 ms ) drives the spatio-temporally chaotic state of the fibrillating stage to a completely quiescent state.
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Fig. 3. Elimination of the spiral turbulent state through perturbation of the e field. The left column shows the e-field and the right column shows the g-field. The control is applied for 44 ms. starting at T= 891 ms. As seen in the figure, by T = 1540 ms. the spatiotemporally chaos has been removed - leading to a quiescent condition, where the pacemaker can once more take over with a regular rhythm. |
For a nifty movie of the control method in operation on a simulated heart tissue (of dimension 512 x 512 lattice points) click here: MPEG movie of defibrillation (507 Kbytes, created by Ashwin Pande)
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