**1. Introduction**

Dilated cardiomyopathy (DCM) is one of the most common types of cardiomyopathy worldwide. It is characterized by progressive chamber dilatation and myocardial systolic dysfunction and diagnosed by finding left ventricular (LV) enlargement and impaired systolic LV function (LV ejection fraction less than 50% or fractional shortening of less than 25-30%). Angiotensin-converting enzyme inhibitors and ß-blockers are the best and popular therapeutic interventions for DCM that promotes amelioration of systolic LV dysfunction among 20-45% DCM patients [1 - 5]; nonetheless, the 5-year mortality rate of DCM remains 10-35% under these medical therapy [6 - 8].

The predictive assessment of LV function is clinically important in medical manage‐ ment of DCM, particularly when considering the indication for heart transplantation. In most patients with heart failure, symptoms are not present at rest but become limiting with exercise. Nevertheless, the major measures for LV function of DCM, such as echocardiography, are generally performed under the static condition. In addition, LV contractile function at rest is not reliable for an assessment of the reversibility of LV contraction, that is contractile reserve [3, 4]. Therefore, it is important to evaluate LV functional response under dynamic conditions by use of pharmacological as well as exercise stress [9].

This article reviews the current status of myocardial contractile reserve with our findings, including procedures for evaluating contractile reserve, clinical implications, and molecular biological significance.

© 2013 Okumura and Murohara; licensee InTech. This is an open access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. © 2013 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
