Determining the prognosis in each patient with idiopathic dilated cardiomyopathy (IDC) has been an important goal since the introduction of cardiac transplantation. Although heart transplants continue to be limited to critically ill patients, the triage of IDC patients will assume greater importance as the era of an implantable artificial heart nears. How successful are current approaches to identifying patients with high short-term mortality rates?
The New York Heart Association-rated class IV patient who experiences repeated hospitalizations and has a need for inotropic support is clearly at a high risk of death. Thus, the consideration for a heart replacement is straightforward. Most patients with IDC are not critically ill and do not require such an urgent intervention, yet perhaps 20% of such patients will die within 1 year. Early follow-up studies1–6 have identified a number of variables that are associated with an adverse outcome. Some of the better predictors were New York Heart Association class rating, increasing age, a low left ventricular ejection fraction (LVEF), high left ventricular filling pressures, a very dilated left ventricle, exercise peak oxygen uptake (V̇o2) of < 11 to 16 mL/kg/min, marked intraventricular conduction delay (including a permanent pacemaker), and complex ventricular arrhythmias. Later studies that included echocardiography confirmed the importance of these factors and identified additional variables associated with adverse outcomes, including a relatively low left ventricular mass,7 the presence of moderate or greater mitral regurgitation,8– an increased left atrial size, right ventricular enlargement,9– and a reduced right ventricular ejection fraction.10– Echocardiographic parameters of diastolic function that reflect a high left atrial pressure were also predictive of adverse outcomes and included a high early diastolic mitral inflow velocity, a short early diastolic mitral inflow velocity deceleration time,11–12 and a reduced pulmonary venous inflow velocity during ventricular systole.13– A “Doppler index,” which was defined using the formula (isovolumic contraction time + isovolumic relaxation time)/ejection time, was introduced to assess both right and left ventricular function and, as would be anticipated, the reduced function of either ventricle identified patients with unfavorable outcomes.14–15