Cardiac arrhythmia is a condition where the heart develops irregular heartbeats which are either too fast or too slow. Heart rate counts during this condition ranges from 50 to 100 per minute. It is harmless in people with healthy hearts but for those with weak hearts it may lead to heart attacks.
Are bottlenose dolphins and Weddel seals prone to arrhythmias while performing their vaunted dives? Scientists believe they do. They have detected too much irregular heartbeats akin to heart arrhythmia during these dives.
Despite being used to aquatic environment and highly adapted to it, marine mammals have yet to develop immunity to the physiological demands while holding their breath and performing very challenging physical activities.
“The heart is receiving conflicting signals when the animals exercise intensely at depth, which often happens when they are starting their ascent. We’re not seeing lethal arrhythmias, but it is putting the heart in an unsteady state that could make it vulnerable to problems,” said lead author Terrie Williams, professor of ecology and evolutionary biology at University of California-Santa Cruz.
It is common knowledge among marine life experts that animals while diving, experience abnormally fast heart rate. This differs according to how deep they are going and the how fast they are doing it. The heart rate alternately goes abnormally high then goes down to the resting stage which is below 60 beats per minute. Cardiac arrhythmias or irregular heartbeats are present in over 70 percent of these deep sea diving stunts.
By using a newly developed tracking system, researchers will record heart rate, number of swimming strokes, depth and time consumed during these dives. Researchers will track highly trained bottle nose dolphins while they dive in pools and in open water. The research will also include free-roaming Weddel seals while they swim under the icy surface of McMundo Sound in Antarctica.
The significance of this new research lies in obtaining additional data on stranding activities of deep-diving marine mammals such as beaked whales.
Researchers will observe conditions associated with cardiac arrhythmia. This will include physical activities during fast take off which is similar to stranding activities of beaked whales and blue whales when they are exposed to the noise coming from the ships and mid-frequency military sonars.
The results of the research have also important implications to humans. The response of mammals to diving or dive reflex also happens in humans and other land based mammals and this occurs when the face comes in contact with cold water, researchers explained.
Details of the study were published in Nature Communications.