1. Heart Failure: One of the signs of heart failure is a rapid heartbeat. Neglecting this condition can be life-threatening, as studies show that every 5 bpm increase in heart rate raises the risk of cardiovascular disease-related death by 15%.

2. Atrial Fibrillation: Atrial fibrillation heightens the chances of blood clot formation, which can lead to strokes.

Consequently, individuals with this condition face a higher risk compared to the general population. 

3. Diabetes: A research published in the International Journal of Epidemiology reveals that every 10 bpm increase in heart rate elevates the risk of developing diabetes by 23%. 

4. Thyroid Disorders: Thyroid issues have an impact on heart function. Hyperthyroidism can cause sinus arrhythmia and, in severe cases, thyrotoxic heart disease.