Yes, caffeine affects heart rate, why do you think people drink coffee in the morning? The coffee and caffeine gives them a adrenaline boost and makes the heart pump faster, bringing more oxygen and blood to your brain, essentially bringing you out the stupor that is early morning grogginess. Caffeine mildly stimulates the nervous and cardiovascular systems. It affects the brain and results in elevated mood, decreased fatigue, and increased attentiveness, so a person can think more clearly and work harder.
Caffeine is also a mildly addictive drug as well, since studies has shown people who have withdrew from caffeine for 18 to 24 hours, have felt symptoms such as headache, fatigue, irritability, depression, and poor concentration.
To avoid this, take the coffee slowly and in small amounts over a long period of time