New Sensors Offer Better Diagnosis and Treatment of Abnormal Heart Rhythms
Boston University’s (BU) Nanotechnology Innovation Center researchers have developed and successfully tested new technology that uses light to assess the heart's electrical system, enabling effective diagnosis of abnormal heartbeats or arrhythmia and opening exciting new possibilities for cardiac research. This work is supported by the NSF-funded Engineering Research Center (ERC) in Cellular Metamaterials (CELL-MET), headquartered at BU with partners including the Michigan, Florida International, Harvard, and Columbia Universities, as well as Argonne National Lab, EPFL (Switzerland) and Centro Atomico-Bariloche (Argentina).
Cardiomyocytes are the contracting heart muscle cells that allow the heart to pump. Each cardiomyocyte needs to contract in coordination with its neighboring cells to efficiently pump blood from the heart; if this coordination breaks down, serious abnormal heart rhythms such as ventricular fibrillation can occur. Current understanding of this process is largely based on studies outside of the body that use voltage sensitive dyes for imaging electrophysiological activity. Genetically encoded voltage indicators have been developed to improve on voltage dyes, but they have had performance limitations. CELL-MET’s new technology is a genetically encoded sensor that uses cardiac optogenetics, or optical monitoring, of cardiac electrical function in three-dimensional (3D) microengineered tissue models. This technology allows tracking of voltage signals with higher spatial resolution and from multiple subcellular locations and can more easily record voltage from small subcellular areas. They also open the possibility of studies in living organisms.
Cardiac excitation-contraction coupling describes the series of events from the production of an electrical impulse (action potential) to the contraction of muscles in the heart. This process is of vital importance as it allows for the heart to beat in a controlled manner, without the need for conscious input. EC coupling results in the sequential contraction of the heart muscles that allows blood to be pumped, first to the lungs (pulmonary circulation) and then around the rest of the body (systemic circulation) at a rate between 60 and 100 beats every minute, when the body is at rest. This rate can be altered, however, by nerves that work to either increase heart rate (sympathetic nerves) or decrease it (parasympathetic nerves), as the body's oxygen demands change. Ultimately, muscle contraction revolves around a charged atom (ion), calcium (Ca2+), which is responsible for converting the electrical energy of the action potential into mechanical energy (contraction) of the muscle. This is achieved in a region of the muscle cell, called the transverse-tubule during a process known as calcium induced calcium release.
