Neuroendocrine activation after myocardial infarction: causes and consequences

Percutaneous implantation of an intraventricular device for the treatment of heart failure: experimental results and proof of concept

BACKGROUND

A percutaneous system to implant a ventricular partitioning device (VPD) has been developed to partition the left ventricular (LV) cavity for treating regional wall motion abnormalities associated with post-left anterior descending (LAD) infarction, dilated left ventricle, and systolic dysfunction. The hemodynamic effects of this novel approach were evaluated in an ovine model with an anteroapical infarction created by a coil placed in the LAD.

METHODS AND RESULTS

LV anteroapical infarction (MI) was induced in 10 animals. The VPD device was implanted at 6 weeks after MI in 5 animals. The hemodynamic status of each animal was evaluated at 30 weeks post-MI in treated ("VPD+MI" group, n=5) and nontreated ("MI" group, n=5). The comparison of end-point hemodynamic variables shows a significantly smaller end-systolic LV volume in the animals receiving the implant (70.1+/-9.0 mL in "VPD+MI" group vs. 102.9+/-10.3 mL in "MI" group, P < .02), improved ejection fraction (46.9+/-5.2% in "VPD+MI" group vs. 34.7+/-6.8% in "MI" group, P < .04) and preserved cardiac output (5.2+/-0.7 L/min in "VPD+MI" group vs. 5.0+/-1.8 L/min in "MI" group, P=NS), suggesting more efficient mechanical performance of the LV with the implanted VPD.

CONCLUSIONS

A significant reduction in LV volumes and corresponding improvement in LV function occurred after device implantation indicating a potential beneficial effect of this new device in treatment of post MI LV dilation.

Neurohormones in an ovine model of compensated postinfarction left ventricular dysfunction

Clinical heart failure, often the result of myocardial infarction, may be preceded by a period of compensated left ventricular impairment. There is substantial need for an experimental model that reflects this human condition. In sheep, coronary artery ligation produced consistent left ventricular anteroapical myocardial infarctions resulting in chronic (5 wk), stable hemodynamic changes compared with sham controls, including reductions in ejection fraction (51 +/- 2 vs. 30 +/- 5%, P < 0.001), cardiac output (6.3 +/- 0.2 vs. 5.1 +/- 0.2 l/min, P < 0.01), and arterial pressure (93 +/- 2 vs. 79 +/- 3 mmHg, P < 0.001), and increases in cardiac preload (left atrial pressure, 3.3 +/- 0.1 vs. 8.3 +/- 1.3 mmHg, P < 0.001). These changes were associated with acute and sustained increases in plasma concentrations of atrial natriuretic peptide (ANP; 5 wk, 11 +/- 2 vs. 27 +/- 5 pmol/l, P < 0.001), brain natriuretic peptide (BNP; 3 +/- 0.2 vs. 11 +/- 2 pmol/l, P < 0.001), and amino-terminal pro-brain natriuretic peptide (NT-BNP; 17 +/- 3 vs. 42 +/- 12 pmol/l, P < 0.001). Significant correlations were observed between plasma levels of the natriuretic peptides (ANP, day 7 to week 5 samples; BNP and NT-BNP, day 1 to week 5 samples) and changes in left ventricular volumes and ejection fraction. In contrast, renin activity, aldosterone, catecholamines, and endothelin were not chronically elevated postinfarction and were not related to indexes of ventricular function. Coronary artery ligation in sheep produces the pathological, hemodynamic, and neurohormonal characteristics of compensated left ventricular impairment secondary to myocardial infarction. Plasma concentrations of the cardiac natriuretic peptides are sensitive markers of left ventricular dysfunction. This is a reproducible model that reflects the clinical condition and should prove suitable for investigating the pathophysiology of, and experimental therapies in, early left ventricular dysfunction.

Disruption of the relationship between renin and atrial natriuretic peptide early in the course of ventricular dysfunction

BACKGROUND

Plasma renin activity is normal in left ventricular dysfunction in the absence of diuretic therapy. In health there is a reciprocal relationship between renin and atrial natriuretic peptide (ANP) but a positive correlation in advanced heart failure. The relationship between renin and ANP in mild left ventricular dysfunction is unknown.

METHODS AND RESULTS

Patients with left ventricular dysfunction (n = 35, 18 without diuretic therapy) were compared to 20 age-matched healthy subjects. Plasma concentrations of active renin (PARC), ANP and norepinephrine were measured after 20 min rest and 45 min after an infusion of normal saline (10 ml/kg body wt.). Basal plasma ANP was increased in patients with left ventricular dysfunction compared to healthy subjects, whether or not they were receiving diuretics. PARC was similar in healthy controls and patients untreated with diuretics but was increased in diuretic treated patients. After saline loading in healthy subjects PARC fell while ANP rose. Patients with left ventricular dysfunction had a smaller decline in PARC, that did not achieve statistical significance, but had a greater increase in plasma ANP compared to healthy subjects (P<0.05). The close reciprocal relationship between PARC and ANP observed in healthy subjects before and after saline loading (r = 0.8, P<0.001 and r = 0.6, P<0.01) was weakened in those not receiving diuretics (r = 0.4, P<0.05 and r = 0.24, ns) and lost in those receiving diuretics (r = 0.1 and r = 0.08).

CONCLUSIONS

Patients with left ventricular dysfunction have a disturbance of the normal reciprocal relationship between PARC and ANP which antedates diuretic treatment. This should be taken into account when interpreting plasma neuroendocrine measurements in patients with ventricular dysfunction.

Plasma brain natriuretic peptide--an independent predictor of cardiovascular mortality in acute heart failure

PURPOSE

To examine the prognostic importance of both plasma atrial natriuretic and B-(brain natriuretic peptide) following an episode of acute heart failure.

SUBJECTS AND METHODS

A prospective cohort of 91 patients admitted into hospital with acute heart failure were recruited. After initial in-hospital management plasma ANP and BNP levels were measured by radioimmunoassay, and echocardiography was performed on the same day. Patients were followed up for 12 months and the main outcome measure was cardiovascular death.

RESULTS

Plasma ANP and BNP levels were significantly higher in patients who died of a cardiovascular cause within 12 months (P<0.001 and P<0.0001, respectively) or at 1-month (P<0.05 and P<0.001) after recruitment. By Kaplan-Meier estimated life-table curves, patients with above median plasma ANP or BNP levels had significantly higher 1-year mortality (42.5% vs. 11.6%, both P<0.005). By multivariate Cox proportional hazard regression analysis, the plasma BNP level was the most important prognostic factor predicting mortality (chi2 = 18.3, P<0.0001), followed by age (chi2 = 11.5, P<0.001). Other factors including ANP, left ventricular ejection fraction by M-mode echocardiography, pulmonary arterial pressure, sex, cause of heart failure as well as New York Heart Association class were not significant.

CONCLUSION

A plasma BNP level has independent and at least short-term prognostic significance in patients admitted with acute heart failure. This non-invasive and readily available blood test should be considered for risk stratification in patients with acute heart failure.