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Principal Investigator: Dr. Robert F. Gilmour, Jr.
Contact Information: Email: rfg2@cornell.edu - Phone: 3-3856
Sponsor: American Heart Association-Northeast Affiliate
Title: Summer Fellowship: Sandeep Mannava
Annual Direct Cost: $3,000
Project Period: 7/1/04-8/31/04
Sudden cardiac death caused by ventricular fibrillation (VF) is the number one killer in the United States, as it leads to more than half of the 400,000 annual heart disease related deaths in this nation. VF is highly irregular electrical activity in the lower two chambers of the heart, which in its physical manifestation renders the ventricles "paralyzed." Although the exact electrophysiological mechanism is not fully understood, spiral wave reentry has been implicated as a mechanism for VF, whereby a planar electrical wave fragments and via constructive/destructive interference becomes a spiral wave that further fractionates into many smaller spiral wavelets. This particular electrophysiological phenomena has been linked to repeating long-short patterned cardiac action potentials known as alternans. Alternating electrical phenomena have been further linked to a steep restitution relation, a function that relates action potential duration (APD) to the intervening diastolic interval (DI). By manipulating this particular relationship, alternans and presumably VF can be suppressed.
The studies described above are now being extended into a new realm, where cardiac excitation is being considered within the context of a small-world network. In small world networks (which are described in more detail in the following section), elements ("cells") are connected locally via 1:1 connections and globally, via "shortcuts", much as a major airport is connected to local surrounding towns by commuter flights, but is also connected to other major airports thousands of miles away by transcontinental flights. In the heart, specialized conducting pathways, such as the His-Purkinje system may assume the role of shortcuts, while conduction through muscle may occur more locally (i.e., from cell to cell). Consequently, the properties of small-world networks may be particularly relevant to cardiac excitation, both during normal beating and during ventricular arrhythmias such as VF.
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