Aldosterone Physiology and Cardiometabolic Risk (page 886)
Normal aldosterone regulation is dynamic and responsive. Therefore, single cross-sectional aldosterone measurements capture only a limited range of aldosterone physiology. Quantifying the dynamic nature of aldosterone physiology may improve the understanding of the relationship between aldosterone and cardiometabolic diseases. In this issue of Hypertension, Vaidya et al hypothesized that progressive cardiometabolic abnormalities would predict a blunted dynamic range of aldosterone. Novel indices of aldosterone responses to dietary sodium manipulation were developed, the Sodium-modulated Aldosterone Suppression-Stimulation Index (for serum and SAUSSI for urine), and tested with risk factors in 539 human participants. These indices were calculated as the ratio of aldosterone on a high dietary sodium balance (maximally suppressed aldosterone) to aldosterone on restricted dietary sodium balance (stimulated aldosterone), thereby reflecting the full dynamic range of aldosterone to dietary sodium modulation. Individual cardiometabolic risk factors and components of the metabolic syndrome strongly predicted higher Sodium-modulated Aldosterone Suppression-Stimulation Index and SAUSSI and captured more predictive power than cross-sectional aldosterone measurements alone. These results suggest that abnormal aldosterone physiology, an impaired ability to appropriately stimulate and suppress aldosterone, may contribute to, and result from, progressive cardiometabolic abnormalities.
Antihypertensive Therapy and Insulin Action (page 800)
Meta-analysis of studies in hypertensive patients using β-blockers and thiazide diuretics indicates that although lowering blood pressure is associated with significantly fewer coronary heart disease events, the benefit is less than that expected from prospective observational data. One explanation is that these older drugs adversely affect cardiovascular risk factors through deleterious effects on insulin action, thereby reducing the impact of blood pressure lowering. This has led to increasing use of newer antihypertensive agents such as angiotensin-converting enzyme inhibitors and calcium channel blockers known to have neutral metabolic effects. Despite this, the Antihypertensive and Lipid-Lowering Treatment to Prevent Heart Attack Trial (ALLHAT), the largest antihypertensive study to date, has shown diuretics to be superior to these newer agents in lowering some cardiovascular outcomes. In this issue of Hypertension, McHenry et al report results from a small study of carefully selected nondiabetic hypertensive patients. In a randomized double-blind crossover protocol, the authors find that sensitive measures of insulin action assessed by the euglycemic hyperinsulinemic clamp technique are no different after treatment with an angiotensin-converting enzyme inhibitor combined with low-dose thiazide compared with an angiotensin-converting enzyme inhibitor alone. These results contrast with the authors’ previous studies in diabetic hypertensive patients, where even low doses of thiazides had a negative impact on glucose metabolism. Overall, the current study is reassuring and should encourage physicians to include low-dose thiazide diuretics in treatment regimens for essential hypertension.
Left Ventricular Global Function Index: Predictive Value (page 770)
Current indices of left ventricular (LV) function are adequate at reflecting the heart’s actual functional state with respect to the vascular system and the body’s needs. However, they do not take into account how much structural remodeling has occurred and the lifetime evolution of the cardiovascular (CV) system for 1 specific individual. Our intent with proposing this novel approach was to integrate information on ventricular remodeling into the functional capacity of the heart for a given vascular system of an individual.
By assessing stroke volume with respect to size of LV cavity and myocardium, the LV global function index combines LV mass, volume, and stroke volume into 1 index. In a multiethnic population free of symptomatic CV disease at baseline, the LV global function index was strongly and consistently associated with adverse CV events during follow-up, whereas LV ejection fraction was not associated with hard CV events beyond heart failure. LV global function index’s predictive power was better and more consistent than LV mass-to-volume ratio and LV ejection fraction and was comparable with indexed LV mass.
By conventional indices, the impact of long-standing increased workload, such as hypertension, is manifested on LV structure before LV function. It is, therefore, essential to have a reliable and reproducible assessment of both LV structure as well as LV function in the risk stratification of cardiac patients. Therefore, LV global function index may provide unique information in the CV risk assessment and therapeutic follow-up of hypertensive patients.
- © 2013 American Heart Association, Inc.