Whole blood impedance aggregometry for the assessment of platelet function in patients with congestive heart failure (EPCOT Trial)

OBJECTIVE

Data from small studies have shown the presence of platelet abnormalities in patients with congestive heart failure (CHF). We sought to characterize the diagnostic utility of the whole blood aggregometry (WBA) in a random outpatient CHF population.

METHODS

Blood samples were obtained for measurement of whole blood aggregation, shear-induced closure time, platelet contractile force, expression of GP IIb/IIIa, and P-selectin in 100 consecutive patients with CHF.

RESULTS

Substantial inter-individual variability of platelet characteristics exists in patients with CHF. There were no statistically significant differences when patients were divided by the incidence of vascular events, emergency revascularization needs, survival, or etiology of heart failure. Surprisingly, aspirin use did not affect instrument readings as well. Whole blood aggregometry correlates well with the closure time (r(2)=0.587), and with GP IIb/IIIa expression (r(2)=0.435). Significant but less strong correlation has been observed for the WBA with platelet P-selectin expression (r(2)=0.295), and no correlation was present for the platelet contractile force measures (r(2)=0.030).

CONCLUSIONS

Despite the fact that patients with heart failure enrolled in the EPCOT trial exhibited marginal, sometimes oppositely directed changes, in their platelet characteristics, whole blood impedance aggregometry is indeed capable to serve as a valuable diagnostic tool, and may be successfully used as an established screening device in this population. Ability of the whole blood aggregometry to predict clinical outcomes, or for the monitoring of anti-platelet agents in CHF patients, will be evaluated in the ongoing clinical trials.

[Calcium antagonists in the treatment of heart failure. Re-evaluation of therapeutic strategies]

The pharmacological management of heart failure has evolved during the last decade from therapies focused on improving haemodynamics to others that modulate neurohormonal systems which are activated in the setting of left ventricular dysfunction. Despite optimal inhibition of these systems with drugs such as ACE inhibitors, beta-blockers, digoxin and, most recently, spironolactone, the mortality rate remains unacceptably high. Calcium antagonists have long been investigated for use in a variety of cardiovascular diseases, including ischaemic heart disease, hypertension, and heart failure. However, concern has arisen with regard to the use of calcium antagonists in the treatment of left ventricular dysfunction--particularly those agents with negative inotropic activity. In addition, first generation dihydropyridines have also generated concern because of their profound vasodilatory effects and the fact that they have been shown to increase noradrenaline (norepinephrine) levels and neurohormonal activity. The third generation dihydropyridine calcium antagonists appear to be more promising therapies for heart failure, given their pharmacological properties of higher vascular selectivity and their minimal effects on neurohormonal activation. Several trials have been conducted with third generation dihydropyridines and additional trials are ongoing. A new class of calcium antagonists, which blocks the T-type calcium channel, was introduced in 1998. The prototype drug, mibefradil, was rigorously tested for use in heart failure in the Mortality Assessment in Congestive Heart Failure (MACH-1) trial. It was expected that calcium antagonists blocking the T-type calcium channel would be of benefit, because of their lack of negative inotropic effects and their ability to induce regression of hypertrophy. The results of the MACH-1 trial were disappointing, and the trial was prematurely discontinued as a result of excess mortality in the mibefradil arm. The purpose of this review is to examine the evidence-based pharmacotherapeutic strategies in the management of heart failure, and to discuss current and potential roles for calcium antagonists in the therapeutic regimen.

Therapeutic options for treating major depression, and the role of venlafaxine

Major depression is a debilitating disorder that is often undertreated. Psychotherapy, electroconvulsive therapy, and pharmacotherapy are options for management. Tricyclic antidepressants and selective serotonin reuptake inhibitors are the cornerstones of drug therapy. Venlafaxine, a phenylethylamine antidepressant that primarily inhibits reuptake of norepinephrine and serotonin, is an alternative to those agents. It has been studied in short-term and continuation studies and appears to have efficacy similar to that of imipramine, trazodone, and fluoxetine. Moreover, venlafaxine is effective in approximately one-third of patients with treatment-resistant depression. Venlafaxine is metabolized by the P-450 enzyme system to an active metabolite O-desmethyl-venlafaxine, which is excreted renally. Nausea, somnolence, and dizziness are dose-related adverse effects that often occur with initiation of therapy. Increases in blood pressure, particularly with high dosages, also may occur. Drug-drug interactions appear to be minimal.