Dose dependence of chronic positive inotropic effect of vesnarinone in patients with congestive heart failure due to idiopathic or ischemic cardiomyopathy

Preload-Adjusted 2 Wave-Intensity Peaks Reflect Simultaneous Assessment of Left Ventricular Contractility and Relaxation

BACKGROUND

The magnitudes of the first (WI1) and the second wave-intensity peak (WI2) during the ejection period can be used as indices of left ventricular (LV) contractility and relaxation, respectively. However, use of WI to characterize LV dp/dt and the end-diastolic volume (V ed) relationship may be more problematic, as WI may be affected by changes in preload.

METHODS AND RESULTS

The LV pressure-volume data sets, consisting of 23 recordings obtained by the conductance method from 12 heart disease patients, were studied. End-systolic elastance (E es) and volume-axis-intercept (V0) were calculated with varying preload. Time constant of LV relaxation (tau), V ed, and WI were calculated from steady-state averaged data. The E es showed a weak correlation with WI1 (r = 0.46, p < 0.05) but a better correlation with preload-adjusted WI1 [WI1/V ed; r=0.86, WI1/V(ed)2; r = 0.92, WI1/(V ed - V0)2; r = 0.89, all p < 0.01]. Similarly, tau did not correlate with WI2 but did correlate with preload-adjusted WI2 [WI2/V ed; r = -0.73, WI2/V(ed) 2; r = -0.63, WI2/(V ed - V0)2; r = -0.78, all p < 0.01].

CONCLUSIONS

These data demonstrate the importance of preload-adjustment when using the WI index for simultaneous assessment of LV contractility and relaxation.

Clinical characteristics of vesnarinone

Congestive heart failure is a common condition with a poor prognosis. Its high rates of morbidity and mortality produce a huge societal burden. Current pharmacological treatment approaches are based on angiotensin-converting enzyme inhibitors, diuretics and digoxin, but up to 5% of patients may have refractory disease with persistent symptoms at rest. Such patients with advanced-stage disease may be candidates for treatment with the novel agent vesnarinone, a mixed phosphodiesterase inhibitor and ion-channel modifier that has modest, dose-dependent, positive inotropic activity, but minimal negative chronotropic activity. Vesnarinone improves ventricular performance most in patients with the worst degree of heart failure. However, before the initiation of vesnarinone therapy, risk-benefit profiles in individual patients should be considered, because in two large-scale studies [i.e. of the high dosage used in the Vesnarinone Study Group Trial (VSGT), and of both dosages used in the Vesnarinone Trial (VEST)] a dose-dependent increase in mortality was identified for vesnarinone 30-120 mg/day. The two studies also found significant vesnarinone-induced, short-term improvements in quality of life (QOL) in patients with refractory end-stage heart failure. Such patients are the most willing to trade-off a slightly increased risk of mortality for improved QOL. It is thus in these patients with refractory end-stage heart failure that vesnarinone may ultimately establish an important treatment role. However, detailed further investigation of the overall place of vesnarinone in heart failure management, with particular reference to the clinical potential of vesnarinone plus beta-blocker combination therapy, for example, is certainly warranted.

Prognostic implications of echocardiography in advanced heart failure

PURPOSE OF REVIEW

The growing epidemic of systolic congestive heart failure mandates strategies to identify accurately people with high morbidity and mortality. Echocardiography remains the most widely available noninvasive tool for the assessment of cardiac structure, function, and hemodynamics. Clinical data paired with echocardiographic analysis in patients with systolic heart failure obtained from a variety of investigations have allowed for the evaluation of this modality as a prognostic tool.

RECENT FINDINGS

Detailed appraisal of the literature has revealed five distinct, easy-to-evaluate echocardiographic parameters that may assist clinicians to segregate high-risk patients. The presence of or the inability to modify a left ventricular ejection fraction less than 25%, impaired right ventricular function (assessed by any of four methods), left ventricular end-diastolic dimension greater than 6.5 to 7 cm, a restrictive mitral inflow, or pulmonary hypertension (peak tricuspid regurgitant velocity >2.5 m/s) should alert clinicians of patients with high morbidity (recurrent congestive heart failure admission, arrhythmia, impaired functional capacity) and mortality. Particularly important among these variables is the presence of a restrictive mitral inflow pattern.

SUMMARY

Detailed analysis of two-dimensional and Doppler data routinely obtained from echocardiograms has established prognostic implications among patients with systolic heart failure. Although prospective clinical trials are lacking, the use of echocardiography to segregate risk should be incorporated into current strategies to treat congestive heart failure and influence clinical listing for cardiac transplantation.

The limitations of preload-adjusted maximal power as an index of right ventricular contractility

Right ventricular (RV) dysfunction is an important cause of perioperative morbidity and mortality, particularly in cardiac surgery. However, assessment of RV contractility remains difficult in clinical practice. Our goal in this study was to examine the value of preload-adjusted maximal power (PWR(max)/end-diastolic volume [EDV](2); PAMP) as an alternative to the load-independent pressure-volume-derived indices of contractility in the RV. In anesthetized dogs, RV end-systolic elastance and preload-recruitable stroke work were studied as "gold standards" by using the conductance technique. PAMP was calculated with pulmonary artery flow and RV pressure measurements. Changes in these indices were compared after modulation of the inotropic state (dobutamine infusion; n = 12) and loading conditions (pulmonary artery and inferior caval vein occlusion; n = 14). All indices increased dose-dependently with dobutamine. PAMP was slightly influenced by preload reduction (the slope of the relation between PAMP and EDV was 0.00397 +/- 0.01026 W. mL(-3). 0.10(-4); mean +/- SD). PAMP decreased significantly during pulmonary artery banding (from 1.1 +/- 0.7 to 0.7 +/- 0.5 W. mL(-2). 0.10(-4); mean +/- SD), whereas end-systolic elastance and preload-recruitable stroke work did not change. We conclude that the value of PAMP as an index of RV contractility is limited in the open-chest/open-pericardium setting, primarily by its sensitivity to alterations in afterload.

IMPLICATIONS

Preload-adjusted maximal power (PAMP), a load-independent contractile index in the left ventricle, could offer a solution to the problem of measuring right ventricular (RV) contractility in clinical practice. However, this study in open-chest dogs suggests that PAMP is unreliable for assessment of RV contractility because of its sensitivity to afterload changes.

Optimal preload adjustment of maximal ventricular power index varies with cardiac chamber size

BACKGROUND

Maximal left ventricular power (PWRmax) can index contractile function and reserve; however, its marked preload dependence mandates load adjustment to yield a more cardiac-specific measurement. Prior studies have used varying methods, but supporting data have generally been lacking. We hypothesized that the optimal approach for preload adjustment varies with ventricular volume (particularly end-systolic volume) and is significantly different for dilated hearts with reduced left ventricular function compared with small to normal-sized hearts with normal systolic function.

METHODS

Left ventricular pressure-volume relations were measured by the conductance catheter method in 36 patients, with preload altered by inferior vena cava obstruction. Patients with normal ventricles (n = 16), hypertrophy or mitral stenosis (n = 12), and dilated cardiomyopathy (n = 8) were divided into three groups based on resting end-diastolic volume: group 1, 66.3 +/- 12; group 2, 118.1 +/- 20; and group 3, 218.2 +/- 48 ml. PWRmax was the maximal product of simultaneous left ventricular pressure and rate of volume change. PWRmax end-diastolic volume (EDV) data were fit to a power function, PWRmax = alphaEDVbeta (where alpha is a scaling factor and beta is the power coefficient), and the preload sensitivity of beta and PWRmax/EDVbeta ratios (beta = 1, 2, or best fit) were compared.

RESULTS

Beta varied directly with chamber size: 0 = 0.004 x (EDV + 0.56), r = 0.65, p < 0.0001. However, it was equally well approximated by 1.0 in groups 1 and 2 (ESV <75 ml, EF >40%), whereas beta = 2 was more appropriate in group 3.

CONCLUSION

PWRmax/EDV provides adequate preload independence in all but dilated hearts with reduced LV function, whereas PWRmax/EDV2 is required in the latter. These data should help clinical application of a noninvasive PWRmax index for assessing chamber contractility and contractile reserve in human beings.

Estimation of central aortic pressure waveform by mathematical transformation of radial tonometry pressure. Validation of generalized transfer function

BACKGROUND

Central aortic pressures and waveform convey important information about cardiovascular status, but direct measurements are invasive. Peripheral pressures can be measured noninvasively, and although they often differ substantially from central pressures, they may be mathematically transformed to approximate the latter. We tested this approach, examining intersubject and intrasubject variability and the validity of using a single averaged transformation, which would enhance its applicability.

METHODS AND RESULTS

Invasive central aortic pressure by micromanometer and radial pressure by automated tonometry were measured in 20 patients at steady state and during hemodynamic transients (Valsalva maneuver, abdominal compression, nitroglycerin, or vena caval obstruction). For each patient, transfer functions (TFs) between aortic and radial pressures were calculated by parametric model and results averaged to yield individual TFs. A generalized TF was the average of individual functions. TFs varied among patients, with coefficients of variation for peak amplitude and frequency at peak amplitude of 24.9% and 16.9%, respectively. Intrapatient TF variance with altered loading (> 20% variation in peak amplitude) was observed in 28.5% of patients. Despite this, the generalized TF estimated central arterial pressures to < or = 0.2 +/- 3.8 mm Hg error, arterial compliance to 6 +/- 7% accuracy, and augmentation index to within -7% points (30 +/- 45% accuracy). Individual TFs were only marginally superior to the generalized TF for reconstructing central pressures.

CONCLUSIONS

Central aortic pressures can be accurately estimated from radial tonometry with the use of a generalized TF. The reconstructed waveform can provide arterial compliance estimates but may underestimate the augmentation index because the latter requires greater fidelity reproduction of the wave contour.