Bradycardia

Laboratory results can provide insight into the cause of a declining heart rate in an ICU patient. An ICU patient's heart rate declined progressively from the 80s bpm to the 50s bpm over the course of a single clinical encounter. The heart becomes more efficient through endurance training, pumping more blood and delivering more oxygen per beat. Endurance training progressively lowers resting heart rate from a normal ~72 bpm toward extreme values as low as ~30 bpm. A progressively declining heart rate pattern during clinical assessment raises clinical concern and suspicion of an underlying condition. A lower resting heart rate, while often interpreted as a sign of fitness, can become problematic at extreme levels.