Cardiac rhythmicity leads to sudden cardiac death which poses a unique challenge to lessen heart diseases that can cause sudden cardiac death in older and younger individuals. In vivo cardiovascular rhythmic pacemaking activities of selected botanical extracts on cardiac channelopathy tachycardia arrhythmias-induced myogenic heart was employed using in vivo model of freshwater crustacean daphnia magna (Water flea). Daphnia magna were cultured, maintained photoperiod at 16 hours light and 8 hours darkness before using as test specimens in the experimentation. Selected botanical extracts were used as treatment concentrations (10%, 20%, 30%) for cardiotoxicity and cardio activity (heartbeats/min). A total of 250 test specimens or daphnids/neonates were collected and used in cardiotoxicity assessment of the selected botanical extracts after a 12 hr time exposure to each treatment concentration solutions (10%, 20%, 30%). Tachycardia arrhythmia was induced by a caffeine dilute solution concentration (30%) in the bathing medium. Three hundred daphnids/neonates were used as test specimens in measuring the arrhythmias-induced myogenic heart of daphnids/neonates in ten replicates determination. Results showed that the selected botanicals are dose-dependent which means that the higher dosage the greater effect to the heartbeat rates. It was revealed that the losses of DPPH absorbance at 540 nm of the selected botanical extracts were in agreement with its anti-tachycardia arrhythmia effect to the heart rate of Daphnia magna. Results showed that the increase in treatment concentrations and time exposure had positive response against cardiac tachycardia arrhythmias-induced myogenic heart of Daphnia magna which behaves similarly to the heartrate of humans.