Isoprenaline is predominantly beta stimulant, a synthetic sympathomimetic amine. Is the isopropyl derivative of norepinephrine. Main use in Cardiology is to enhance the heart rate. It is useful in severe bradycardia where its effect can be titrated by setting up an infusion. Sometimes it can produce hypotension due to systemic vasodilation. It has pulmonary vasodilatory effects as well. The drug can be used as an infusion in congenital and acquired complete heart blocks to increase the ventricular rate when pacing is not immediately feasible.
Isoprenaline challenge has been used during hemodynamic studies in cath lab to induce provocable gradient in dynamic left ventricular obstruction as in hypertrophic obstructive cardiomyopathy. In the electrophysiology lab, it is used to assess the efficacy of catheter ablation. If arrhythmia is not inducible even after an isoprenaline challenge, it is most likely that the arrhythmia has been cured by ablation.
Isoprenaline infusion can cause ventricular tachycardia if the rate of infusion is high. On the contrary, it can be used in the treatment of polymorphic ventricular tachycardia (torsades des pointes) where it acts by shortening the QT interval. Use of the drug in the setting of coronary artery disease has the potential to precipitate myocardial ischemia because of positive chronotropic and inotropic effects, which increase myocardial oxygen demand.