Heart transplantation for tumor.

Unresectable cardiac tumors, although unusual, are often rapidly fatal. A 31-year-old woman presented with a large tumor arising from the left ventricle and causing symptoms of a constrictive cardiomyopathy. After evaluation with echocardiography, angiography, and computed tomography, an exploration was carried out to confirm the extent of disease. Orthotopic heart transplantation was subsequently performed when a donor organ became available. She is now alive and disease-free 12 months after transplantation.

Echocardiographic evaluation of size, function, and mass of normal and hypertrophied rat ventricles.

The noninvasive evaluation of cardiac structure and function in small animals would provide a means for investigators to repeatedly evaluate treatment effects at various stages of experimental protocols. In this study, commercially available echocardiographic and Doppler equipment was utilized to evaluate hypertrophied (HYP) and normal (SH) rat hearts. Surgically induced renovascular hypertension was used to produce a 35% increase in left ventricular (LV) weight in HYP relative to SH hearts. A commercially available echocardiographic system with integral Doppler capabilities and a 7.5-mHz single-crystal mechanical transducer was used to obtain parasternal long- and short-axis images of HYP and SH hearts in anesthetized animals. HYP hearts were found to have normal systolic function, as evidenced by preserved LV systolic and diastolic dimensions and volumes as well as fractional shortening and ejection fraction. HYP hearts demonstrated a 62% increase in their echocardiographically measured LV posterior wall thicknesses and a 44% increase in calculated ventricular mass. Both parameters were reliable in predicting the presence and degree of left ventricular hypertrophy. Doppler flow velocities through the aortic root and pulmonic valve did not differ between groups, again suggesting preserved LV systolic performance. These results indicate that two-dimensional echocardiography provides a useful means to noninvasively evaluate cardiac structure and function in rats.

Altered Ca2+ dynamics in single cardiac myocytes from renovascular hypertensive rats.

Several functional and biochemical characteristics of hypertrophied hearts isolated from rats with renovascular hypertension provide indirect evidence that cellular Ca2+ dynamics during myocardial contraction-relaxation are altered. In this study, intracellular Ca2+ concentration ([Ca2+]i) dynamics were examined in paced left ventricular (LV) myocytes isolated from rats with hypertension (HYP) induced by partial occlusion of the left renal artery and from normotensive rats (Sham). Characteristic myocardial changes produced by renovascular hypertension included a 40% increase in LV weight and a 3.6-fold increase in the fractional expression of the beta-heavy chain of myosin in isolated LV myocytes. In periods of mechanical quiescence between contractions, basal [Ca2+]i values were similar in Sham and HYP LV myocytes. During a contraction-relaxation cycle in HYP myocytes, peak [Ca2+]i, +d[Ca2+]i/dt, and -d[Ca2+]i/dt were reduced, whereas the time required for [Ca2+]i to rise from a basal value to a peak value (time-to-peak [Ca2+]i) was unaffected. In both Sham and HYP myocytes, the fall in [Ca2+]i from peak to basal values could be approximated by a monoexponential rate constant, kf. Values for kf were significantly smaller in HYP than in Sham myocytes. After treatment with 4 microM isoproterenol, peak [Ca2+]i, +[Ca2+]i/dt, -d[Ca2+]i/dt, and kf increased in both Sham and HYP myocytes. In contrast, basal [Ca2+]i and time-to-peak [Ca2+]i did not change. Thus, despite recent reports of inefficiencies of beta-adrenergic receptor coupling, there was no evidence of blunted beta-adrenergic responsiveness in HYP myocytes with respect to [Ca2+]i dynamics during contraction-relaxation. Finally, no Sham vs. HYP differences in the number of specific [3H]-PN200-110 binding sites per cell in quiescent, rod-shaped myocytes were detected, but a significant reduction in [3H]-PN200-110 binding sites in an enriched sarcolemmal membrane fraction isolated from HYP animals was observed. These observations are suggestive of a reduction in slow, Ca2+ channel surface density in HYP myocytes. The results of this study clearly indicate that [Ca2+]i dynamics during contraction-relaxation in single left ventricular myocytes are affected by residence in a chronic setting of renovascular hypertension. In addition, the prolonged [Ca2+]i removal phase observed in HYP myocytes can be restored toward normal by beta-adrenergic agonists.

Cardiac dysfunction in a rat model of chronic bacteremia.

Cardiac function was examined in vivo and in vitro in rats to determine if cardiac dysfunction could be demonstrated in a nonlethal model of infection. Bacteremic rats (n = 6) had a subcutaneous polymicrobial abscess produced via repeated inoculations of an encapsulated foreign body with Escherichia coli, Bacteroides fragilis, and Staphylococcus aureus while control rats (n = 6) had the same subcutaneous, encapsulated foreign body (an inflammatory focus) but were not inoculated with bacteria. Cardiovascular function was assessed indirectly in vivo by measuring the maximal O2 uptake during a progressive exercise test in both groups before and 14 days after the initiation of inoculations. Cardiac function was also assessed in vitro in the same rats by measuring stroke volumes generated at six different preloads with constant heart rate and afterload. Bacteremic rats had a significantly different fever curve and leukocytotic response than control rats over the 14 day period. The majority of rats that received inoculations demonstrated bacteremias, while none of the control animals had positive cultures for the inoculated organisms. Although in vivo assessment of cardiovascular function showed no evidence of dysfunction, in vitro assessment demonstrated a significant rightward shift of the Starling curve in bacteremic rats. These data suggest that LV dysfunction occurs even during nonlethal infections but may be masked in vivo by compensatory mechanisms.

Ca2+-dependent heterometric and homeometric autoregulation in hypertrophied rat heart.

There is evidence to suggest that the alterations in cardiac function that accompany several forms of myocardial hypertrophy are due in part to desensitization of the heart to the positive inotropic effect of extracellular Ca2+ (Cae2+). In this study the heterometric and homeometric functional responsiveness of normal (SH) and hypertrophied (HYP) isolated working rat hearts was examined as a function of extracellular Ca2+ concentration [( Ca2+]e). Surgically induced renovascular hypertension was used to produce a 39% increase in left ventricular (LV) weight in HYP hearts relative to LV weights of SH hearts. The Cae2+ dependence of heterometric autoregulation was examined in SH and HYP hearts. At high left atrial filling pressures, HYP hearts were functionally less sensitive to changes in [Ca2+]e than were SH hearts; this difference appeared to be due to a preload-dependent increase in the functional sensitivity of SH hearts but not HYP hearts to changes in [Ca2+]e. In both SH and HYP hearts, a step increase in afterload resulted in a beat-by-beat increase in peak aortic outflow systolic pressure (AoP) independent of changes in LV diastolic pressure. Under our experimental conditions, the magnitude of this homeometric AoP increase (the Anrep effect) was similar in both SH and HYP hearts. The AoP increase occurred at a monoexponential rate (kHA) and was much faster in SH than in HYP hearts. Furthermore, KHA varied directly as a function of [Ca2+]e only in the SH hearts.