["Cardiac power output" an old tool, possibly a modern tool for assessing cardiac pumping capability, as well as for a short-term prognosis in cardiogenic shock due to acute myocardial infarction].
Hemodynamic monitoring has been used extensively during the last decades for risk stratification and guiding treatment of patients with cardiovascular destabilization, especially in the scenario of acute heart failure and cardiac shock. Every cardiac pump has its own maximum performance, which denotes its pumping capability. The heart is a muscular mechanical pump with an ability to generate both flow (cardiac output) and pressure. The product of flow output and systemic arterial pressure is the rate of useful work done, "or the cardiac power" (CP). Cardiac pumping capability can be defined as the cardiac power output achieved by the heart during maximal stimulation, and cardiac reserve is the increase in power output as the cardiac performance is increased from the resting to the maximally stimulated state (CPR). Resting CP for a hemodynamically stable average sized adult is approximately 1 W. However, during stress or exercise, CPR can be recruited to increase the heart's pumping ability up to 6 W. In acute heart failure, the patient becomes hemodynamically unstable, and most of the cardiac pumping potential is recruited in order to sustain life. Hence, cardiac power measurements in patients with acute heart failure or with cardiogenic shock at rest represent most of the recruitable reserve available during the acute event, and their measurement reflects the severity of the patient's condition. It has been found that a cutoff value for CP of 0.53 W accurately predict in-hospital mortality for cardiogenic shock patients. Others investigators observed cutoff for increased mortality of CP < 1 W, data that were obtained at doses of maximal pharmacologic support yielding the individual maximal CP. In our experience, the cutoff value for CP that accurately predicts in-hospital mortality for cardiogenic shock patients is 0.7 W, but its impact on short-term prognosis is clearer if the patient achieves a CP equal or higher than 1 W after an optimal myocardial revascularization with interventional cardiac procedures. According to the data collected from the literature, CP deserves a place in the evaluation of the patient with cardiogenic shock due to an acute myocardial infarction, but a more profound analysis of this parameter an further evaluation are required in order to better understand its prognostic meaning in this acute cardiac syndrome.