January 14, 2022 - Podcast

Episode 217— Preglacial topography, and heart attack treatment

What did North America look like before ice-sheets streamed through it, carving out lakes and flattening fields? For the first time, a research team including IU scientists have reconstructed a view of North America’s mid-continent, before glaciers changed the landscape forever. The researchers say their findings enable better understanding of how ice and land co-evolve underneath ice sheets and illuminate some key climate change questions, including what may happen as current continental ice sheets respond to climate warming and where subsurface water resources may be available. It’s very challenging to know what the initial topography looked like prior to any glaciation, because it’s covered by ice, buried by sediment or eroded away, says Doug Edmonds, Boyce Chair of Geological Sciences at IU Bloomington and co-author on the study. But, he says, knowing the starting condition is essential to defining how much erosion or deposition has occurred and where. Researchers used digital elevation models, data derived from millions of residential and municipal water well logs, and high-powered computer algorithms to reconstruct what the preglacial surface looked like 2.6 million years ago. They say the reconstructed topography of such a huge section of North America constitutes a big addition to earth science, but they also point to a benefit beyond the scientific impact of their work – understanding the long evolution of our landscape tells us something about the land we call home. Edmonds says glaciation is probably the most significant event that reshaped North America’s mid-continent, rerouting rivers and leaving behind flatlands in some places and rolling hills in others. And, he says, there is something intriguing about seeing our landscape prior to that transformation.

In other news, a study led by IU School of Medicine researchers is challenging standard treatment methods used to prevent muscle damage during a heart attack. IU’s Rohan Dharmakumar, executive director of the Krannert Cardiovascular Research Center, says that a common treatment given to patients experiencing a heart attack may not be as successful in halting muscle damage as once thought. Treating heart attacks focuses on opening up the coronary arteries as quickly as possible through a procedure called reperfusion, which often uses a stent. The common belief is that once the coronary arteries are opened, the damage to the heart muscle is stopped. Dharmakumar says that is not always the case. This research demonstrates that if reperfusion results in internal bleeding, or hemorrhage, within the heart muscle, the heart muscle can continue to die even after the coronary artery is opened, he says. Hemorrhage is known to occur in heart muscle of around half of all heart attack patients who undergo reperfusion, he says, and this work sought to determine what effect that internal bleeding has on progressive heart muscle damage after reperfusion. Dharmakumar says the study showed that infarction size, or death of tissue that results from a failure of blood supply, is not only determined by restricted blood supply to the heart, but also by the effects of the reperfusion therapy, and the introduction of hemorrhage within the at-risk area might, in some cases, nearly negate in total the benefits of reperfusion therapy. Dharmakumar says having an awareness of the role reperfusion can play on continued muscle death can help physicians provide better treatment to patients in the future. Although there may be little to be done when it comes to lost time before a patient arrives at the hospital, he says minimizing the effects of hemorrhage following reperfusion can give us a new opportunity to reduce the size of infarction, and downstream negative consequences, in nearly half a million heart attack patients in the United States alone.