Surrogate end points in heart failure

Implantable hemodynamic monitors: Can be conductance catheter system successfully implemented?

Successful management of cardiac heart failure requires a multifactorial approaching. It has been suggested that implantable hemodynamic long-term monitoring can improve patient care. This paper presents an analysis of the hemodynamic parameters commonly recorded, the most used implantable devices and their associated clinical trials. Newly implantable miniaturized sensors and devices are revisited. Finally, a newly implantable conductance-catheter based system is presented. The feasibility to realise volume and pressure measurements in the human left ventricular cavity using an implantable conductance-catheter based system is evaluated. It has the advantage to obtain LV signals continuously. In addition, it allows to realise maneuvers such as calibration and LV function by telemetry being avoiding patient hospitalizations. The rapid advances in device monitoring capabilities could change the new paradigm of the heart disease management.

Predictors of clinical outcomes in patients given carvedilol for heart failure

Risk factors for outcomes in heart failure (HF) were derived from populations in clinical trials, at hospital discharge, or in localized geographic or socioeconomic strata before the widespread use of beta blockers. This study observed 4,280 patients in a community-based HF registry for 1 year after completing carvedilol titration. Independent risk factors for death, hospitalization for HF, or hospitalization for cardiovascular reasons other than HF were first identified by age-, gender-, and race-adjusted analyses, then by multivariate analysis adjusted simultaneously for all factors. Over this period, 7% of patients died, 11% were hospitalized for HF, 12% were hospitalized for other cardiovascular reasons, and 27% had > or =1 of these events. The most significant outcome predictors were New York Heart Association class III or IV, history of hospitalization for HF or other cardiovascular reasons, and angina pectoris, all associated with increased odds of having an adverse outcome (all p < or =0.001). The left ventricular ejection fraction was not a significant outcome predictor by multivariate analysis. The odds ratio for an adverse outcome was significantly reduced for patients with hypertensive or idiopathic causes of HF and for those whose physicians had graduated from medical school > or =24 years earlier compared with <14 years earlier (all p <0.005). In conclusion, easily obtained historical information predicts clinical outcomes in patients with HF in the year after initiating carvedilol. In this unselected community population, these historical factors were better predictors of risk than the left ventricular ejection fraction.

Determination of left ventricular volume changes by intracardiac conductance using a biventricular electrode configuration

AIMS

The feasibility of determining left ventricular (LV) volume changes by LV conductance measurements with an implantable device was investigated in an animal model.

METHODS AND RESULTS

The haemodynamic state of six mongrel dogs was altered by overpacing with rates up to 140 bpm and by isoprenaline infusion with dosages up to 0.2 microg/kg/min. The LV conductance, aortic blood flow, and LV and aortic pressure were recorded. Conductance measurements were carried out using the two electrodes of a bipolar right ventricular pacing lead for current injection and two epicardial leads screwed into the mid-lateral LV wall for measuring the resulting voltage. Stroke conductance (SY) was correlated with the LV stroke volume (LVSV), which was computed from the aortic flow. The LVSV rose to 188+/-14% with increasing isoprenaline dosage. A strong correlation between the LV conductance SY and the LVSV was found (mean r=0.97). The LVSV decreased to 68+/-8% with an increasing pacing rate. Again, a strong correlation between SY and LVSV was found (mean r=0.89).

CONCLUSION

This animal study confirms the feasibility of assessing changes in LVSV by determining the LV intracardiac conductance. This creates the possibility of continuous haemodynamic monitoring with implantable devices.

The relationship between blood pressure, pulse pressure and right ventricular function following an atrial switch procedure for complete transposition of the great arteries

BACKGROUND

The pressure overload may be responsible for the failure of the systemic ventricle. No study so far has evaluated the association between arterial blood pressure values and right ventricular function in adults with atrially corrected complete transposition.

METHODS

This was a retrospective analysis. The studied population consisted of 60 patients with complete transposition, 11.5+/-2.7 years after atrial switch procedure, divided into subgroups according to the severity of systemic ventricular dysfunction (right ventricular ejection fraction < or = 0.40 vs. > 0.40), and the severity of perfusion abnormalities in the radionuclide study (absent or mild vs. moderate-to-severe).

RESULTS

All patients had blood pressure values (systolic 109.1+/-11.7 mm Hg and diastolic 72.3+/-9.7 mm Hg) within the normal range. Systolic blood pressure values correlated inversely with right ventricular ejection fraction (r = -0.450; p < 0.001). Compared to patients with systolic blood pressure below median values, patients with "elevated" blood pressure had lower right ventricular ejection fraction (32.6+/-6.3 vs. 38.9.+/-7.2; p < or = 0.002) and more significant perfusion abnormalities (1.5+/-1.0 vs. 2.9+/-1.5; p < or = 0.001). In a multivariate backward logistic regression model age at surgery and at the time of the study, systolic blood pressure at rest predicted impaired right ventricular ejection fraction (p < 0.02). Greater pulse pressure at peak exercise female sex were associated with greater more severe perfusion abnormalities (p < 0.01).

CONCLUSIONS

There is a significant correlation between blood pressure values and indices of right ventricular dysfunction in patients who underwent an atrial switch procedure for complete transposition. Blood pressure values might be considered as a surrogate end point in these patients.

Tolerability of carvedilol in heart failure: clinical trials experience

An extensive clinical trials database now exists to support the therapeutic efficacy of beta-blockers in systolic heart failure. However, concerns remain about the tolerability of these agents. These concerns relate to perceived complexity in initiation and uptitration, risk of worsening heart failure clinical status, and delay in beneficial effects on outcomes. All of the above concerns are thought especially relevant in patients with advanced disease. However, these perceptions are not borne out in the controlled clinical trial experience or in open-label studies and postmarketing surveillance programs with carvedilol. Specifically, in clinical studies, discontinuation rates (because of adverse events), serious adverse event rates, mean achieved dose, and percentage reaching target dose strongly suggest good tolerability. This is especially notable, considering that beta-blockade is used in addition to other background neurohormonal antagonists, such as angiotensin-converting enzyme inhibitors. Furthermore, tolerability in the everyday community setting also appears to be high. Carvedilol, specifically, is also well tolerated during initiation of therapy, with fewer withdrawals for heart failure during the first 8 weeks of uptitration, and no delay in the accrual of beneficial clinical outcomes, as observed in the Carvedilol Prospective Randomized Cumulative Survival (COPERNICUS) study. Thus, in contrast to widely held perceptions about tolerability of beta-blockade in heart failure, carvedilol appears to be an extremely well-tolerated agent, even during initiation and in the most advanced patients.

Meta-analysis of the effects of endothelin receptor blockade on survival in experimental heart failure

BACKGROUND

Although an initial study of endothelin receptor blockade reported positive findings, subsequent experiments and clinical trials in humans found little or no benefit.

METHODS

We applied meta-analytic methods to assess the methodologic rigor of preclinical studies of endothelin blockade and to quantitatively evaluate the totality of evidence regarding the effect of endothelin receptor blockers in experimental heart failure. A total of 396 animals were assigned to control and 594 were assigned to experimental therapy in the pooled analysis. Of the 9 studies identified, no study reported a priori sample size justification. Although there was a tendency to increased mortality with early administration (relative risk 1.39, P=.15) and decreased mortality with late administration (relative risk 0.85, P=.6), in the overall analysis, there was no significant evidence of benefit or harm (relative risk 1.03, P=.9). Studies with a small sample size had estimated effects that tended to deviate further from the pooled estimate of all studies.

CONCLUSIONS

Consideration of mortality effects in the totality of studies revealed no significant effect of endothelin antagonists in animal models of experimental heart failure. Given the potential for between-study variability, reliance on studies with small sample size may lead to unrealistic expectations when extrapolating preclinical experimental results to future research.