Device-induced ventricular geometric remodeling: appraisal of critical issues

Devices to therapeutically alter the shape of failing left ventricles are being developed by at least two laboratories. This review attempts to assess potential for benefit and possible negative consequences of the device concepts.

Data from all known publications and scientific presentations were reviewed. Findings address four key issues: (1) Predictions, based on physical computations, of direct beneficial reduction in myocardial afterload are indeed computationally realistic and supported by effects reported experimentally. (2) Concerns that remodeling might necessitate unacceptably high epicardial contact pressure appear unfounded. Computational force modeling indicates that with optimization of contact area and contour, the expected degree of remodeling (approximately 20% effective radius reduction) might be achieved by epicardial pressures very near existing endocardial pressures, and in diastole, well below arterial perfusion pressures. Reported augmentation of systolic function suggests that there is no significant compromise of regional perfusion in acute (< or = 4 weeks) preclinical studies. (3) If intramural tangential shear stresses were sustained by local bending, detrimental tensile/compressive stresses might be introduced. However, microstructure predicts and reported evidence confirms rapid shear-stress relaxation. (4) The same reduction in wall-stress/chamber-pressure ratios that produces benefit during systole would simultaneously worsen diastolic same-volume stiffness. However, if better systolic contraction effects more complete emptying, operational volume range should become incrementally lower, at least compensating. This is supported by early published data.

There appears to be solid computational and early experimental support for the concept of geometric ventricular remodeling. If one or more of the devices being tested should prove to be safe and effective, left ventricular geometric remodeling will be of substantial benefit in heart failure treatment.