Deep-diving marine mammals suffer from arrhythmias or irregular heartbeats

Scientists have found evidence that marine mammals like seals and dolphins may suffer from arrhythmias, a condition of having of irregular heartbeats. Arrhythmias are likely to occur in these animals mostly during their deep dives in search of food.

Scientists at the University of California, Santa Cruz, confirmed that complication with heartbeats happen in Weddell seals and bottlenose dolphins whenever they need to hold their breath during deep dives, reports HNCN.
It is known that for these animals, heart rate tends to go drastically down during diving, in order to conserve energy.

But once they start chasing underwater prey, to match up to the level of increased physical effort, heart rate also goes up.


Such different signals eventually give rise to erratic heart rhythms or arrhythmias.

“The heart is receiving conflicting signals when the animals exercise intensely at depth, which often happens when they are starting their ascent,” says lead author Terrie Williams, a professor of ecology and evolutionary biology. “We’re not seeing lethal arrhythmias, but it is putting the heart in an unsteady state that could make it vulnerable to problems.”

Based on the depth these animals need to dive or the amount of physical effort they need to exert while chasing a prey, the heart rate varies to a great extent. The reduced rate is a condition defined as bradycardia, and an increased rate is termed as tachycardia.

As far as the dive response and heart rate are concerned, marine mammals do not have the perfect system; even evolution has failed to provide them with one.

The research team used specialized devices to monitor the heart rate, frequency of swimming strokes, and the depth and duration of dives.

The devices were attached to the animals, and enough data were recorded from the trained dolphins in both the diving pools and in open sea, and also from the Weddell seals swimming under Antarctic ice.

In more than 70 percent of the animals’ dives, arrhythmias was detected by the researchers. The researchers then wanted to know the relevance of their findings to humans, also known to have dive response. And they found that in humans, the response appears when the face touches the cold water.