[Assessment of cardiac contractile reserve]

Left ventricular (LV) function is usually measured by imaging modalities such as echocardiography under static conditions in patients with dilated cardiomyopathy (DCM). However, some studies have reported that LV contractile function at rest is not reliable for assessment of the reversibility of LV contraction. Therefore, it is important to evaluate LV functional response under dynamic conditions by use of pharmacological as well as exercise stress (contractile reserve). In our studies, LVdP/dtmax was measured at rest and under dobutamine stress using a pigtail catheter with a high-fidelity micromanometer placed into the left ventricle in DCM patients. deltaVdP/dtmax as an index of myocardial contractile reserve was defined as the percentage increase in LVdP/dtmax induced by dobutamine infusion. Firstly, deltaLVdP/dtmax was correlated with peak oxygen consumption by cardiopulmonary exercise testing. In addition, impaired deltaLVdP/dtmax was associated with unfavorable prognosis. Secondly, reduced deltaLVdP/dtmax was associated with an increased washout rate evaluated by myocardial 123I-MIBG and 99mTc-MIBI scintigraphy. Finally, this residual contractile reserve was related to molecular remodeling caused by overactivation of the sympathetic nerve system in DCM patients. This review focused on the current status of contractile reserve with our findings, including procedures for evaluating contractile reserve, clinical implications, and molecular biological significance.