Comparison of cardiotropic drug effects on haemodynamic and myocardial energetics in patients with heart failure: a computer simulation

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Abstract
The purpose of our study is to compare haemodynamic responses and the ischaemic potential of commonly used inotropes (dopamine, dobutamine and milrinone) using a computer model of the cardiovascular system. Cardiotropic drugs interact with the model by changing ventricular elastance and resistance of the individual circulation. All three drugs increase cardiac index in a dose-dependent manner. Dopamine at medium and high infusion rates increases heart rate, systemic vascular resistance and arterial blood pressure. The associated increase in coronary blood flow, however, is not sufficient to account for increased oxygen demand. Both dobutamine and milrinone decrease vascular resistance and increase coronary blood flow. The more pronounced increase in heart rate associated with dobutamine, however, results in a higher ischaemic potential for this drug. Our simulation demonstrates that although all the drugs studied improve cardiac function in simulated patients with heart failure, milrinone accomplishes this at a lower energy cost. The computer simulation developed can be used to assess the complex effect of cardiotropic drugs and possibly suggest optimal drug therapy in specific clinical situations.