Partial loading of the left ventricle during mechanical assist device support is associated with improved myocardial function, blood flow and metabolism and increased exercise capacity

Background: Myocardial recovery has been observed after placement of left ventricular assist devices in some patients awaiting cardiac transplantation. Left ventricular assist devices provide profound volume and pressure unloading while restoring systemic blood flow. However, the optimal degree of left ventricular unloading during left ventricular assist device support is unknown. The purpose of this study was to assess the effect of the degree of left ventricular decompression, during left ventricular assist device support, on myocardial function and exercise capacity. Methods: Twenty patients with a left ventricular assist device performed cardiopulmonary exercise testing with simultaneous echocardiographic and hemodynamic measurements during full, and then partial, device support. Eleven patients underwent positron emission tomographic scanning for measurement of myocardial blood flow and oxygen consumption. Results: Patients were divided into two groups based on the degree of left ventricular decompression as assessed by echocardiographic measurements. Patients with partially decompressed ventricles (n = 13, LVEDD = 4.8 +/- 1.0 cm) as compared to those with fully decompressed ventricles (n = 10, LVEDD = 3.0 +/- 0.3 cm) demonstrated significant improvements in: peak oxygen consumption (16.8 +/- 4.3 versus 12.8 3.0 ml/kg-min), native left ventricular index during exercise (2.5 +/- 1.4 versus 0.8 +/- 0.8 liters/min(.)m(2)); ability to exercise with the device weaned (10 of 13 versus I of 10 patients); resting myocardial blood flow (0.55 +/- 0.11 versus 0.21 +/- 0.13 ml/g-min); and myocardial oxygen consumption (0.04 +/- 0.01 versus 0.02 +/- 0.001 min(-1)) (all p < 0.05). Conclusions: These results suggest that partial loading of the left ventricle during left ventricular assist device support may be beneficial, Further study of optimal ventricular decompression during device support is needed, as this may be important in improving myocardial recovery.