Preventive cardiology
Myocardial and Vascular Dysfunction and Exercise Capacity in the Metabolic Syndrome

https://doi.org/10.1016/j.amjcard.2005.07.091Get rights and content

The metabolic syndrome (MS) is associated with cardiovascular risk exceeding that expected from atherosclerotic risk factors, but the mechanism of this association is unclear. We sought to determine the effects of the MS on myocardial and vascular function and cardiorespiratory fitness in 393 subjects with significant risk factors but no cardiovascular disease and negative stress echocardiographic findings. Myocardial function was assessed by global strain rate, strain, and regional systolic velocity (sm) and diastolic velocity (em) using tissue Doppler imaging. Arterial compliance was assessed using the pulse pressure method, involving simultaneous radial applanation tonometry and echocardiographic measurement of stroke volume. Exercise capacity was measured by expired gas analysis. Significant and incremental variations in left ventricular systolic (sm, global strain, and strain rate) and diastolic (em) function were found according to the number of components of MS (p <0.001). MS contributed to reduced systolic and diastolic function even in those without left ventricular hypertrophy (p <0.01). A similar dose–response association was present between the number of components of the MS and exercise capacity (p <0.001) and arterial compliance. The global strain rate and em were independent predictors of exercise capacity. In conclusion, subclinical left ventricular dysfunction corresponded to the degree of metabolic burden, and these myocardial changes were associated with reduced cardiorespiratory fitness. Subjects with MS who also have subclinical myocardial abnormalities and reduced cardiorespiratory fitness may have a higher risk of cardiovascular disease events and heart failure.

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Patient population

We recruited 410 subjects, most with cardiovascular risk factors (hypertension, diabetes mellitus, obesity), but without a previous history or clinical evidence of heart failure or coronary artery disease, who were undergoing risk factor management at the hospital (n = 332) or in the community (n = 78). The exclusion of 17 patients suspected to have organic heart disease or coronary heart disease on echocardiography and stress testing left a study group of 393 patients. The study patients

Clinical characteristics

MS, as defined by the National Cholesterol Education Program Adult Treatment Panel III criteria, was highly prevalent (44%) in our study population, who had no overt coronary artery disease or heart failure. Table 1 lists a number of the significant differences in the anthropometric and metabolic characteristics between patients with and without MS. The wider use of angiotensin-converting enzyme inhibitors, statins, and calcium channel blockers likely reflected the greater prevalence of

Discussion

The results of this study suggest that MS is an important predictor of subclinical myocardial dysfunction in patients without overt cardiovascular disease. Not only was the MS independently associated with subclinical dysfunction, but also the number of features of the MS was associated with the degree of myocardial dysfunction, reduced arterial compliance, and the degree of reduced cardiorespiratory fitness. Above all, these myocardial changes were independent predictors for exercise capacity.

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    This study was supported in part by a Centers of Clinical Research Excellence Award from the National Health and Medical Research Council, Canberra, Australia.

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    Copyright © 2005 Elsevier Inc. All rights reserved.