Effects of passive cardiac containment on left ventricular structure and function: verification by volume and flow measurements

Biodegradable vs Nonbiodegradable Cardiac Support Device for Treating Ischemic Cardiomyopathy in a Canine Heart

Clinical studies of the efficacy of the nonbiodegradable CorCap device have shown inconsistent findings, at least in part, because of device-related impairment of diastolic cardiac function. We hypothesized that use of biodegradable material for the cardiac support device could contribute to an improvement in the diastolic function of the failing heart. Polyglycolic acid and polyethylene terephthalate were used to prepare biodegradable and nonbiodegradable cardiac support devices, respectively. Twelve-month-old beagles underwent anterior coronary artery ligation. One week after, the beagles were randomly assigned for implantation of a biodegradable cardiac support device (n = 7), nonbiodegradable cardiac support device (n = 8), or sham operation (n = 8). Twelve weeks after coronary artery ligation, the biodegradable group showed a significantly greater recovery of echocardiographical ejection fraction than the nonbiodegradable and the sham groups (40% ± 3.3%, 32% ± 2.5%, and 29 ± 2.6%, respectively). Of note, diastolic function, as assessed by Tau, -dp/dt min, and end-diastolic pressure-volume relationship in the cardiac catheter, was significantly better in both left and right ventricles in the biodegradable group than in the nonbiodegradable group. Moreover, global end-systolic wall stress was significantly lower in the 2 device groups than in the sham group (P < 0.03). Furthermore, global end-diastolic wall stress was significantly less in the biodegradable device group than in the nonbiodegradable group (P < 0.02). The cardiac support devices made of biodegradable material were more effective in improving systolic function, with preservation of diastolic function in the canine infarct heart, than devices made of nonbiodegradable material.

Novel treatment options for chronic heart failure: a radiologist's perspective

OBJECTIVE

This article aims to familiarize radiologists with novel treatment options for chronic heart failure that is unresponsive to medical therapy, such as mechanical cardiac assist devices, surgical procedures, resynchronization therapy with biventricular pacing, and cellular cardiomyoplasty, and their radiographic appearances.

CONCLUSION

Heart transplantation as a treatment of debilitating heart failure provides an opportunity for meaningful long-term survival but is limited by a shortage of donor hearts. This has spurred the development of new treatment options for chronic heart failure that is unresponsive to medical therapy.

Effect of passive cardiac containment on ventricular synchrony and cardiac function in awake dogs

OBJECTIVE

Passive restraint of the left ventricle (LV) has been shown to have beneficial effects on acute hemodynamics and reverse remodeling in both animal and human models. The goals of this study were to test whether a left ventricular support device (LVSD) improves LV synchrony and/or affects cardiac performance.

METHODS

Ten dogs were chronically instrumented to measure hemodynamics and LV volume (sonomicrometry). Congestive heart failure (CHF) was induced by repeated intracoronary microembolization via a chronically implanted coronary catheter. The LVSD was implanted after establishment of CHF in five animals, and five animals were observed as controls. All animals were then observed for 8 weeks. A mathematical model to measure LV synchrony was used to evaluate LV motion over time.

RESULTS

Mean arterial pressure and LV pressures was significantly increased after LVSD therapy, and LV pressure-volume relationships were shifted leftwards, although no change was seen in ejection fraction, end-systolic elastance, or LV dP/dt versus control. There was no significant change in diastolic function in LVSD animals compared with control animals. End-diastolic volumes were reduced by 15% after 8 weeks with LVSD treatment, versus an increase of 8% in control animals (p<0.05). Synchrony was significantly improved with LVSD therapy compared with control (9% vs 76% of baseline) in 1 of 11 ventricular dimension axes (Anterior-Apex).

CONCLUSIONS

LVSD therapy provided only minimal improvement in ventricular synchrony and partially improved hemodynamics. Further study into mechanisms of benefit are warranted.

Assessment of Mitral Valve Regurgitation at Electron-Beam CT: Comparison with Doppler Echocardiography

PURPOSE

To prospectively compare mitral valve regurgitation fractions calculated at electron-beam computed tomography (CT) (Doppler echocardiography as reference standard) and to evaluate accuracy of electron-beam CT volume and flow measurements compared with magnetic resonance (MR) imaging results.

MATERIALS AND METHODS

Institutional review board approval and informed consent were obtained. Volume and flow measurements were performed at electron-beam CT in 219 patients (197 men, 22 women; mean age, 61.5 years +/- 10.4 [standard deviation]), of whom 157 had known isolated mitral valve regurgitation. Regurgitation volume was calculated as the difference between left ventricular total and forward stroke volumes. Regurgitation fractions were compared with corresponding echocardiographic grades (grades 0-IV) by using Spearman rank correlation and a weighted kappa test. In 22 patients, CT volume and flow measurements were compared with MR results by using intraclass correlation.

RESULTS

Regurgitation fractions at CT correlated well with echocardiographic grading (rank correlation coefficient, r(S) = 0.82; P < .05). Mean regurgitation fractions for echocardiographic grades 0, I, II, III, and IV were 3.1% +/- 6.2, 12.7% +/- 9.9, 25.3% +/- 12.3, 40.4% +/- 11.5, and 55.9% +/- 13.7, respectively. The most suitable thresholds for differentiating echocardiographic grades were calculated regurgitation fractions of 6%, 20%, 30%, and 44%; with these thresholds, individual echocardiographic grades were differentiated (grades 0 vs I-IV, 0-I vs II-IV, 0-II vs III-IV, and 0-III vs IV, respectively) with sensitivities of 89%, 87%, 86%, and 93% and specificities of 81%, 87%, 92%, and 91%, respectively. There was perfect agreement in classification of mitral valve insufficiency between electron-beam CT and echocardiography in 134 (61%) patients and a mismatch by one grade in 72 (33%) and by two grades in 13 (6%) (kappa = 0.84). Intraclass correlation coefficients between CT and MR imaging for total and forward stroke volumes and regurgitation volume and fraction were 0.88, 0.79, 0.93, and 0.89, respectively.

CONCLUSION

Electron-beam CT provides quantitative information on severity of mitral valve regurgitation, but semiquantitative classification of regurgitation showed mismatch between electron-beam CT and Doppler echocardiography by at least one grade in more than one-third of all patients.

Worldwide clinical experience with the CorCap Cardiac Support Device

It has been hypothesized that the mechanical burden associated with LV remodeling leads to increased myocardial wall stress and adverse remodeling, all of which serve to further impair cardiac performance and contribute to disease progression. The CorCap Cardiac Support Device (CSD) (Acorn Cardiovascular, Inc., St. Paul, Minnesota) is a mesh-like device that is surgically implanted around the heart. The device is designed to provide circumferential myocardial wall support, and reduce wall stress and myocyte stretch. Clinical experience with CorCap CSD implants in patients with heart failure can be divided into 3 phases: (1) initial safety studies, (2) randomized controlled trials, and (3) limited marketed release. Initial safety studies were undertaken in 48 patients recruited between April 1999 and April of 2001. In 11 patients with complete follow-up, it was noted that LV size, as measured by LV end-diastolic dimension, significantly decreased as early as 3 months postimplant, with an even greater reduction at 6 months. Most importantly, this benefit was sustained, so that the LV end-diastolic dimension stayed smaller at 1, 2, and 3 years of follow-up. There was also an improvement in LV function, as manifested by changes in LV ejection fraction. Ejection fraction was significantly increased by 3 months and appeared to reach a peak improvement by 6 months. This benefit was likewise maintained at 1, 2, and 3 years postsurgery. Hemodynamic data did not show any evidence of constrictive physiology. These preliminary safety studies had shown that the CorCap CSD could be implanted safely and without excess operative morbidity or mortality. The primary objective of the Acorn Randomized Clinical Trial is to assess the efficacy and safety of the CorCap CSD in patients with advanced heart failure despite optimal medical therapy. A randomized trial with 2 arms (mitral valve surgery randomized to CSD and cardiomyopathy randomized to medical therapy alone or with CSD) enrolled 300 patients. The primary endpoint of the trial is a change in clinical status from baseline to the end of the efficacy phase as determined by a clinical composite score. The Acorn CorCap CSD received CE mark approval in Europe in 2001 and has been available to a small number of centers in a Limited Market Release Surveillance Study (LMRSS).