Hello, Lisinopril as such cannot cause tachycardia or increase in heart rate. But it can cause increase in potassium levels that may lead to ventricular arrhythmias. Due to decreased dosing of atenolol, your heart rate is increased. If you have any other problems like palpitations, shortness of breath, excessive sweating,) dizziness, and swelling of feet Then you need to consult your cardiologist for further examination. But as if now no need to worry about increased heart rate. You will get adjusted eventually. Few side effects of Lisinopril are blurred vision, cloudy urine, confusion, reduction in urine output or urine-concentrating ability, dizziness, faintness, or lightheadedness when getting up suddenly from a lying or sitting position, sweating, unusual tiredness or weakness. Take care. Hope I have answered your question. Let me know if I can assist you further. Regards, Dr. Pallavi M., Anesthesiologist