A drug is considered chronotropic if it changes the heart rhythm in some way. Many drugs can alter the heart rhythm and may be administered specifically for this purpose, while in others, the change is a side effect and the patient has to be monitored to make sure the heart stays healthy. Drugs with a strong chronotropic effect are usually available by prescription only because they can be dangerous. Weaker drugs, like caffeine, known to increase the heart rate, are readily available.
Chronotropic drugs can work in a number of ways. One option is a dromotropic drug, one that works by influencing the electrical impulses used to control heart rhythm. Drugs to slow or speed impulses can be used to regulate the heartbeat in a patient and may also control the coordination of electrical impulses to make the heart more efficient. Inotropic drugs control the muscular contractions of the heart, influencing the strength of those contractions and the subsequent power of each heart beat.
Bathmotropic medications can increase excitability in the heart, making it more sensitive to signals, while lusitropic compounds influence relaxation, a phase in the heartbeat where the muscles release before preparing to tense up again. Calcium overload or increased uptake of calcium in the heart can make it harder for the heart to relax, interfering with the normal cycle of the heartbeat.
Chronotropic drugs can be used in emergency settings where a patient's heart is not beating normally and care providers want to stabilize it. The drug will be prescribed on the basis of the kind of abnormal rhythm, the cause, and any other symptoms being experienced. Doctors want to avoid pushing patients too far in the other direction and they are also concerned with the potential side effects of some chronotropic drugs. Often a patient with acute heart problems is having other medical issues and a cascading effect can be a cause for worry when people are providing treatment.
These drugs can also be used in the long term by people with heart problems who need help regulating the heartbeat. A pacemaker can be one option, but chronotropic drugs are less invasive and may be more suitable for the treatment of certain conditions. Beta blockers are an example of a class of chronotropic drugs designed for extended use in patients with cardiac problems. Usually, patients on such medications need regular follow-up appointments to monitor heart health, adjust drug dosages if needed, and to discuss any side effects and other symptoms the patient has developed.
