Doppler echocardiography of 119 normal-functioning St Jude Medical mitral valve prostheses: a comprehensive assessment including time-velocity integral ratio and prosthesis performance index.

The purpose of this study was to provide, in a large number of patients, comprehensive Doppler echocardiographic assessment of normal St Jude Medical mitral valve prosthesis function using Doppler-derived hemodynamic variables, including the mitral valve prosthesis-to-left ventricular outflow tract time-velocity integral ratio and prosthesis performance index. The pressure half-time was less than 130 milliseconds in all patients, and all but one patient had either a peak early mitral diastolic velocity of 2 m/s or less or a mitral valve prosthesis-to-left ventricular outflow tract time-velocity integral ratio of less than 2.2. There was a significant (P < .001) negative correlation between the prosthesis performance index and prosthesis size. This negative correlation suggests that there is more efficient use of the in vitro geometric orifice area with smaller prostheses.     

Effect of heart rate and preload on index of myocardial performance in the normal and abnormal left ventricle.

BACKGROUND: The index of myocardial performance (IMP) has been used as a prognostic systolic-diastolic index for patients with dilated cardiomyopathy and postmyocardial infarction. To date, systematic evaluation of the effect of heart rate and preload alteration on IMP has not been performed with normal or reduced left ventricular (LV) function. METHODS: We studied 14 mongrel dogs at baseline, after the induction of acute ischemic LV dysfunction, and with chronic LV dysfunction. Heart rate was altered by atrial pacing 10 and 20 beats above baseline, and volume loading was accomplished with 10 mL/kg of saline at a paced rate. Hemodynamics, and transmitral and transaortic pulsed Doppler, were obtained. RESULTS: With normal LV function, there were no changes in IMP with pacing. With acute LV dysfunction, IMP was also unchanged with pacing, although both LV ejection time (ET) (192 +/- 23 vs 208 +/- 25 milliseconds, P < .05) and isovolumic contraction time (58 +/- 25 vs 72 +/- 31 milliseconds, P < .05) declined. With chronic LV dysfunction, IMP was unchanged although LV ET declined (188 +/- 15 vs 204 +/- 18 milliseconds, P < .01). Volume loading did not alter the IMP with normal LV function although LV ET increased (208 +/- 25 vs 220 +/- 20 milliseconds, P < .001). With acute LV dysfunction, IMP decreased (0.66 +/- 0.11 vs 0.82 +/- 0.20, P < .05) because of a decrease in isovolumic relaxation time (63 +/- 33 vs 76 +/- 38 milliseconds, P < .05). With chronic LV dysfunction, IMP also declined with volume loading (0.59 +/- 0.29 vs 0.73 +/- 0.28, P < .01) because of an increase in LV ET (224 +/- 30 vs 198 +/- 22 milliseconds, P < .0001). CONCLUSION: Heart rate incrementation does not change IMP. However, volume loading reduces IMP primarily as a result of LV ET lengthening with chronic LV dysfunction. Further systematic evaluation of IMP is needed if this index is to be useful as a prognostic indicator.     

Histological changes over time around the site of sustained release naltrexone-poly(DL-lactide) implants in humans.

In order to assess the histological tissue changes over time around the site of implant, tissue biopsies were taken at 1 to 38 months post-implant from 54 (34 male) consenting human subjects who had received the Australian subcutaneous naltrexone-poly(DL-lactide) implant for heroin dependence. The implant consists of multiple tablets containing compressed naltrexone-poly[trans-3,6-dimethyl-1,4-dioxane-2,5-dione] (DL-lactide) loaded microspheres. Assessment of tissue samples by pathologists showed an early phase (up to 12 months post-implant) of inflammation, foreign body reaction, and fibrosis. This subsided gradually over the next 12 months until tissue returned to normal by 25+ months. Sufficient evidence was not available to conclude that the poly(DL-lactide) implant matrix was totally biodegradable within the study period. While implant material was not identified in most of the latter biopsies, its presence was noted in one biopsy at 26 months post-implant. Nevertheless the study results did demonstrate the implant's biocompatibility by the lack of inflammation, foreign body reaction, and fibrosis detected by 25+ months. It seems highly probable that surgical technique rather than the implant itself was associated with the additional finding of fat necrosis. Moderate fat necrosis was observed as a common feature of biopsies carried out during the first 6 months following implant. It subsided to mild levels over the next 18 months, and was notably absent by 25+ months. The results of the study indicated that the Australian naltrexone-poly(DL-lactide) implant is well tolerated and may have a role for use in the management of medical conditions such as heroin dependence.