How does hypothermia affect the cardiac rhythm observed on an ECG?

Hypothermia affects cardiac rhythm primarily by causing bradycardia, which is a slowing of the heart rate. As the body temperature drops, the metabolic processes slow down, leading to changes in myocardial conduction and a decreased heart rate. This is a common response to significant hypothermia.

Additionally, Osborn waves, also known as J waves, can typically be observed on an ECG of a patient suffering from hypothermia. These waves appear as small, positive deflections following the QRS complex, associated with the lowering of body temperature, and signify the impact of hypothermia on cardiac depolarization.

This phenomenon reflects the electrical instability of the heart caused by colder temperatures affecting ion channel function and myocardial cell activity. Hence, when evaluating an ECG in the context of hypothermia, one would expect to see both bradycardia and the presence of Osborn waves, making this option the most accurate.