Metabolic Syndrome and Myocardial Contractile Reserve

Metabolic syndrome (MetS) is a clustering of cardiovascular risk factors including hyperglycemia, dyslipidemia, and hy-pertension, which have been shown to increase cardiovascular (CV) morbidity and mortality. In addition, it is well known that the association between the presence of MetS and adverse CV outcomes is independent of diabetes mellitus (DM) and arterial hypertension. 3)4) Since the MetS is a strong predictor of future CV events, the changes of left ventricular (LV) structure and function in patients with MetS are considered one of mechanisms explaining the link between the MetS and CV morbidity and mortality. The previous studies have already reported the LV geometry and function by demonstrating increased LV mass and subclinical LV systolic and/or diastolic dysfunctionis impaired in the MetS patients. However, the most studies were conducted in the resting state, not during exercise. Considering that most patients with type 2 DM and/ or hypertension have symptoms during exercise, the study by Ha et al. 8) suggests that the patients with MetS might also have decreased LV functional reserve during dynamic exercise. A total of 112 hypertensive patients complaining of exertional dyspnea were included and divided into two groups according to the existence of MetS. Exercise stress echocardiography using supine bicycle was performed and a variety of Doppler parameters were measured at baseline, at each stage of exercise, and during recovery. There was a significant difference in E/E' parameter, that is an index of LV filling pressure, in MetS patients at resting state. The increased E/E' value was maintained during dynamic exercise test, which is similar to the result of a prior study. A unique result to this study is that LV longitudinal functional reserve, defined as the change in tissue Doppler imaging (TDI), S' (longitudinal tissue velocity) from baseline to peak exercise was significantly lower in MetS patients even though there was no significant difference in base-line TDI S' velocity between the two. After adjusting for known CV risk factors, an independent relationship between the presence of MetS and LV systolic functional reserve was observed. The recent use of TDI, strain, and strain rate at resting state allows detecting earlier subclinical dysfunction and providing essential mechanisms in understanding the development of heart failure. In addition, TDI parameters such as S', E', A', and E/E' have been known to have independent prognostic values in various cardiac diseases, 10) even in low risk population. 11) However, there is a study …