Biosketch / Results /
Douglas HolmesAssistant Professor, Department of Medicine
Assistant Professor, Department of Pediatrics
NYU EKG Associates
560 First Avenue
New York, NY 10016
Education— New York University Medical Center|, Clinical Fellowships
— New York University Medical Center, Internship
1988-1992 — Columbia University College of Physicians and Surgeons, Medical Education
Atrial fibrillation (AF) is the most common clinical arrhythmia seen and results in significant morbidity and mortality. As a result, there is tremendous interest in understanding the mechanisms leading to and supporting AF. Clinically, AF starts with ectopic atrial activity originating from the pulmonary veins or the body of the left atrium. Should these atrial beats coincide with a vulnerable atrial substrate able to support multiple wavelet reentry, AF results. While there are currently no good animal models to study ectopic atrial activity, an atrial tachy-paced model is used to study the atrial changes resulting from high frequency electrical activity. While this model recapitulates many of the features of clinical AF, it also has numerous shortcomings. More recently, it has been observed that following congestive heart failure, atrial structures dilate and are thus susceptible to AF initiation. This model is more closely related to human pathophysiology. We are using a rabbit model of myocardial infarction to study the cellular changes induced by pressure overload atrial dilation.
At the cellular level, we are investigating the electrophysiologic alterations underlying abnormal automaticity and triggered activity. Failing cardiac tissues undergo remodeling of their ion handling proteins characterized by up or down regulation of protein expression. In general, these changes tend to amplify subthreshold electrical events into triggered activity. While the mechanisms behind ventricular ectopy have become well characterized, those of the atrium are less well understood. Among the differences between atrial and ventricular cells is the presence of IP3 receptors in atrial tissue. These calcium-releasing receptors are up regulated in failing atrium and may play a role in both triggered activity within the atrial free wall and abnormal automaticity from spontaneously firing cells within the pulmonary veins. Using confocal microscopy and patch clamp techniques, in a collaboration with the laboratory of Dr. William Coetzee and Michael Artman, we simultaneously measure subcellular calcium transients and sarcolemmal membrane currents. Interactions between excitation-contraction mechanisms and IP3 calcium release could form the basis of new atrial specific therapeutic targeting.