Regression of left ventricular mass in systemic hypertension

Cardiomyocyte-restricted restoration of nitric oxide synthase 3 attenuates left ventricular remodeling after chronic pressure overload

Although nitric oxide synthase (NOS)3 is implicated as an important modulator of left ventricular (LV) remodeling, its role in the cardiac response to chronic pressure overload is controversial. We examined whether selective restoration of NOS3 to the hearts of NOS3-deficient mice would modulate the LV remodeling response to transverse aortic constriction (TAC). LV structure and function were compared at baseline and after TAC in NOS3-deficient (NOS3−/−) mice and NOS3−/− mice carrying a transgene directing NOS3 expression specifically in cardiomyocytes (NOS3−/−TG mice). At baseline, echocardiographic assessment of LV dimensions and function, invasive hemodynamic measurements, LV mass, and myocyte width did not differ between the two genotypes. Four weeks after TAC, echocardiographic and hemodynamic indexes of LV systolic function indicated that contractile performance was better preserved in NOS3−/−TG mice than in NOS3−/− mice. Echocardiographic LV wall thickness and cardiomyocyte width were greater in NOS3−/− mice than in NOS3−/−TG mice. TAC-induced cardiac fibrosis did not differ between these genotypes. TAC increased cardiac superoxide generation in NOS3−/−TG but not NOS3−/− mice. The ratio of NOS3 dimers to monomers did not differ before and after TAC in NOS3−/−TG mice. Restoration of NOS3 to the heart of NOS3-deficient mice attenuates LV hypertrophy and dysfunction after TAC, suggesting that NOS3 protects against the adverse LV remodeling induced by prolonged pressure overload.

Calcium channel blockers in veterinary medicine

Calcium channel blockers are becoming increasingly popular in veterinary medicine for the treatment of systemic hypertension, cardiac arrhythmias, and hypertrophic cardiomyopathy. Calcium is vital to many cellular functions and thus stringent regulation of intracellular calcium concentrations is required. Pharmacologic manipulation of the regulatory mechanisms has the potential to alter cellular function in all body systems. In human medicine, calcium channel blockers are being evaluated for, among other things, use in treating glaucoma, deep vein thrombosis, and pulmonary hypertension, in renal transplantation, and for prevention of reperfusion injury. The potentially beneficial effects of these drugs have often been overshadowed by adverse effects including hypotension, inappetence, bradycardia, conduction abnormalities, and decreased cardiac output. With the introduction of sustained-release formulations (diltiazem) and 2nd generation calcium channel blockers (amlodipine) many of these effects have been attenuated or eliminated. This paper will review the functions of calcium and the calcium channels as well as discussing the classes and current and potential uses of the various calcium channel blockers.

Comparison of five antihypertensive monotherapies and placebo for change in left ventricular mass in patients receiving nutritional-hygienic therapy in the Treatment of Mild Hypertension Study (TOMHS)

BACKGROUND

Increased left ventricular mass (LVM) by echocardiography is associated with increased risk of cardiovascular disease. Thus, it is of interest to compare the effects of both pharmacological and nonpharmacological approaches to the treatment of hypertension on reduction of LVM.

METHODS AND RESULTS

Changes in LV structure were assessed by M-mode echocardiograms in a double-blind, placebo-controlled clinical trial of 844 mild hypertensive participants randomized to nutritional-hygienic (NH) intervention plus placebo or NH plus one of five classes of antihypertensive agents: (1) diuretic (chlorthalidone), (2) beta-blocker (acebutolol), (3) alpha-antagonist (doxazosin mesylate), (4) calcium antagonist (amlodipine maleate), or (5) angiotensin-converting enzyme inhibitor (enalapril maleate). Echocardiograms were performed at baseline, at 3 months, and annually for 4 years. Changes in blood pressure averaged 16/12 mm Hg in the active treatment groups and 9/9 mm Hg in the NH only group. All groups showed significant decreases (10% to 15%) in LVM from baseline that appeared at 3 months and continued for 48 months. The chlorthalidone group experienced the greatest decrease at each follow-up visit (average decrease, 34 g), although the differences from other groups were modest (average decrease among 5 other groups, 24 to 27 g). Participants randomized to NH intervention only had mean changes in LVM similar to those in the participants randomized to NH intervention plus pharmacological treatment. The greatest difference between groups was seen at 12 months, with mean decreases ranging from 35 g (chlorthalidone group) to 17 g (acebutolol group) (P = .001 comparing all groups). Within-group analysis showed that changes in weight, urinary sodium excretion, and systolic BP were moderately correlated with changes in LVM, being statistically significant in most analyses.

CONCLUSIONS

NH intervention with emphasis on weight loss and reduction of dietary sodium is as effective as NH intervention plus pharmacological treatment in reducing echocardiographically determined LVM, despite a smaller decrease in blood pressure in the NH intervention only group. A possible exception is that the addition of diuretic (chlorthalidone) may have a modest additional effect on reducing LVM.