Electromechanical assessment of left ventricular function following successful percutaneous coronary revascularization

Effect of catheter-based transendocardial delivery of stromal cell-derived factor 1alpha on left ventricular function and perfusion in a porcine model of myocardial infarction

BACKGROUND

Myocardial regeneration after myocardial infarction can occur via stem cell recruitment. Stromal cell-derived factor 1alpha (SDF-1alpha) has been shown to be critical for stem cell homing to injured tissue.

METHODS

Myocardial infarction was induced in pigs via microembolization of the distal left anterior descending artery. Two weeks after myocardial infarction animals underwent catheter-based transendocardial injection of SDF-1alpha into the periinfarct myocardium (18 injections, 5 ìg per injection) (n = 12) or sham-intervention (n = 8). Tc99m sestamibi single-photon emission computed tomography (SPECT) and electromechanical mapping (EMM) of the left ventricle were performed two and seven weeks after myocardial infarction.

RESULTS

Infarct size by tetrazolium staining was similar in both groups (8.9 +/-1.2% of left ventricle vs. 8.9 +/- 2.6%). Vessel density in the periinfarct area was significantly higher in SDF-1alpha treated animals than in controls (349 +/- 17/mm2 vs. 276 +/- 21/mm2, p < 0.05). Myocardial perfusion (SPECT) did not change in either group. Ejection fraction and stroke volume (EMM) decreased in SDF-1alpha animals and increased in controls (difference between groups p = 0.05 for ejection fraction and p < 0.05 for stroke volume). Linear local shortening (EMM) did not change in controls (11.4 +/- 1.3% to 11.5 +/- 0.5%) but decreased significantly in SDF-1alpha treated animals (12.1 +/- 0.9% to 8.4 +/- 0.9%, p < 0.05, p < 0.05 for difference between groups). SDF-1 delivery was associated with a substantial loss of collagen in the periinfarct area (32+/-5% vs. 61+/-6% in control animals, p < 0.005).

CONCLUSION

A strategy to augment stem cell homing by catheter-based transendocardial delivery of SDF-1alpha in experimental myocardial infarction increases periinfarct vessel density, fails to improve myocardial perfusion, is associated with loss of collagen in the periinfarct area and impairs left ventricular function.

Characterization of hibernating myocardium with NOGA electroanatomic endocardial mapping

Because the terms "hibernation" and "viability" are not interchangeable, the recognition of hibernating myocardium within viable segments remained elusive for NOGA electroanatomic endocardial mapping. The aim of the present study was to determine the characteristics of hibernating myocardium in NOGA mapping. Baseline and follow-up endocardial mapping, thallium-201 myocardial perfusion scintigraphy at rest, and contrast ventriculography were performed in 28 patients who had proved viable myocardium before and 7.3 +/- 2.5 months after percutaneous coronary intervention. Significantly improved regional wall motion in the revascularized territory (region of interest) was confirmed in 9 patients (group 1) at follow-up (from -2.11 +/- 0.87 to -1.48 +/- 0.43 SD/chord, p <0.05), whereas no change in regional wall motion was observed in 19 patients (group 2; from -2.56 +/- 0.88 to -2.79 +/- 0.91 SD/chord). Average normalized thallium uptake at rest increased significantly in groups 1 and 2 after revascularization. A trend toward increased unipolar voltages in the region of interest was observed in group 1 at follow-up (from 10.6 +/- 3.5 to 11.7 +/- 4.0 mV, p = 0.073), whereas no change was observed in group 2 (from 8.7 +/- 4.4 to 8.9 +/- 3.8 mV). A significant increase in local linear shortening was measured only in group 1 (from 7.5 +/- 5.2% to 10.3 +/- 3.9%, p <0.05). Hibernating myocardial segments exhibited significantly higher unipolar voltages and late thallium uptake at rest at baseline. Receiver-operator characteristic analysis showed a mean unipolar voltage of 9.0 mV (predictive accuracy 0.708, common sensitivity and specificity 72%) in the region of interest for prediction of functional recovery. In conclusion, for characterizing the hibernating myocardium within viable segments, NOGA endocardial mapping offers on-line guidance for percutaneous coronary and noncoronary myocardial revascularization.

Prognostic value of endocardial electromechanical mapping in patients with left ventricular dysfunction undergoing percutaneous coronary intervention

Endocardial electromechanical mapping (EEM) has been proposed as a method for myocardial viability assessment. However, the impact of EEM data on clinical outcome has not been studied before. We sought to assess the prognostic value of EEM in patients with left ventricular (LV) dysfunction undergoing percutaneous coronary intervention (PCI). Seventy-five patients with coronary artery disease and LV dysfunction (angiographic LV ejection fraction [EF] 49 +/- 15%) underwent LV EEM for myocardial viability assessment before coronary revascularization. EEM parameters included mean unipolar electrographic amplitude, mean local shortening, LV volumes, LVEF, number of regions with electrographic amplitudes <7.5 mV, number of electromechanical mismatch, and match regions. Cardiac death, nonfatal myocardial infarction, nonfatal stroke, and acute heart failure requiring hospitalization were defined as clinical events. During a follow-up of 3.6 +/- 1.8 years, 20 clinical events occurred. Event-free survival after coronary revascularization was significantly better in patients with a mean unipolar electrographic amplitude of >/=9.5 mV than in patients with a mean unipolar electrographic amplitude of <9.5 mV (88% vs 57%; p <0.005). Cox regression analysis revealed angiographic LVEF, mean electrographic amplitude, number of regions with electrographic amplitudes <7.5 mV, number of electromechanical match regions, and EEM EF as univariate predictors of clinical events. In a multivariate analysis, angiographic LVEF <40% (hazard ratio 4.78, p <0.005) and mean electrographic amplitude <9.5 mV (hazard ratio 2.92, p <0.05) were independent predictors of clinical events. Thus, EEM provides prognostic information in patients with LV dysfunction undergoing coronary revascularization.