Hans G. Olbrich

PROGNOSTIC SIGNIFICANCE OF CORONARY FLOW RESERVE ON LEFT VENTRICULAR EJECTION FRACTION IN CARDIAC TRANSPLANT RECIPIENTS

BACKGROUND Cardiac allograft vasculopathy is a common phenomenon in epicardial and microvascular vessels. Intramyocardial vessel disease may lead to small, stellate infarcts. The present study tested the impact of microvascular vasomotor function on changes in left ventricular systolic function in the long-term follow-up after cardiac transplantation. METHODS Seventeen consecutive cardiac transplant patients, 40+/-21 months after cardiac transplantation, without angiographically visible cardiac allograft vasculopathy and without episodes of acute rejection were included in the study. Coronary microvascular reactivity was assessed by the endothelium-dependent stimulus acetylcholine (50 microg i.c.) and by the endothelium-independent stimulus dipyridamole (0.56 mg/kg i.v.) utilizing an Doppler catheter. Radionuclide ventriculography was performed at the time of coronary flow measurement and repeated 2 years later to correlate changes in left ventricular ejection fraction with the coronary flow reserve measurement 2 years previously. RESULTS There was a statistically significant correlation between endothelium- independent coronary flow reserve to dipyridamole and changes in ejection fraction at rest (r=0.59; P < 0.01) and during exercise (r=0.48; P < 0.05). Twenty-four months later, patients with a coronary flow reserve to dipyridamole < 2.5 showed a significant decline in ejection fraction during exercise (-7 +/- 5%) compared to patients with a coronary flow reserve > 2.5 (1.1+/-5%; P=0.003). Coronary flow reserve to acetylcholine was not correlated with a reduced ejection fraction during exercise. CONCLUSIONS Endothelium-independent microvascular dysfunction has prognostic importance for deterioration of left ventricular function in cardiac transplant recipients without angiographically visible coronary artery stenoses. These results reinforce the concept that microvascular and epicardial vessel disease after transplantation are two distinct entities with different functional consequences.

The effect of cyclosporine on electrically paced isolated rat cardiomyocytes.

The acute cardiotoxicity of cyclosporine was investigated in isolated cardiomyocytes from adult rats. In a first study, myocytes were incubated with CsA ranging from 1 to 10 μg/ml and paced by electrical-field stimulation. After 30 min of stimulation the number of surviving rod-shaped myocytes was significantly reduced at 2.5 μg/ml (77.9%) and 5 μg/ml CsA (64.2%) as compared with the drug vehicle methanol (88.8%, P<0.05) with a further decrease at 10 μg/ml CsA (30.1% vs. 81.2%, P<0.005). In a second study, with the use of digital image processing of fura-2 fluorescence, the mean intracellular free calcium concentration, integrated over 1 sec, of single myocytes in the presence of 5 μg/ml CsA, the solvent methanol, or pure Krebs Ringer Hepes buffer was measured. Starting 2 Hz field stimulation increased the intracellular free calcium concentration from 100.1 to 177.9 nM in buffer and from 145.7 to 200.6 nM calcium with methanol. In contrast, there was a 3-fold increase of the intracellular free calcium concentration with 5 μg/ml CsA from 128.8 to 376.1 nM calcium. The intracellular free calcium during electrical stimulation was significantly higher with CsA than with the solvent (376.1 nM vs. 200.6 nM, P<0.001). In a further study, myocytes were incubated with calcium ranging from 0.5 to 8 mM calcium in the presence of 5 μg/ml CsA or the solvent methanol and electrically stimulated. Here, with increasing extracellular calcium the number of rod-shaped myocytes decreased significantly with CsA as compared with the solvent (P<0.02). The data suggest that CsA exerts a dose-dependent toxic effect on isolated rat cardiomyocytes that depends on the extracellular calcium concentration. There is direct evidence that CsA increases the intracellular free calcium concentration in rat cardiomyocytes.

Ultrastructural localization of calcium in the myocardium of cardiomyopathic Syrian hamsters

Cardiomyopathy of the Syrian hamster is characterized by myocardial calcium overload and focal myocardial necrosis. The cause of the myocardial calcium overload is not yet fully understood. In this study, the ultrastructural localization of calcium was determined in normal hamster hearts and in non-necrotic and necrotic myocardium of cardiomyopathic hamsters (strain BIO 82.62). In many cells from the non-necrotic myocardium of the cardiomyopathic hamsters the calcium deposits, visible as 20 nm particles, were confined to the inner leaflet of the plasma membrane, the T-tubules and the intercalated disks. This corresponds to the calcium distribution found in normal hamsters and other mammalian species. A number of morphologically normal cells, however, displayed an increased amount of calcium precipitate in the mitochondria as well as at the sarcolemma indicating that, in the cardiomyopathic hamster, focal calcium overload is detectable cytochemically in cells which otherwise do not show gross abnormalities. In cells showing morphological signs of myolytic degeneration a marked redistribution of calcium precipitate took place. Sarcolemma became devoid of calcium deposits whereas an enormous amount of clustered precipitate occurred in largely swollen mitochondria. These data are in support of a relationship between impaired ion homeostasis and degeneration events in cardiomyopathy. Furthermore, there appears to be a clear parallelism in calcium redistribution between hypoxic and cardiomyopathic myocardium.

Ultrastructural calcium distribution and myocardial calcium content in human idiopathic dilated cardiomyopathy

Myocardial calcium overload in chronic heart failure is still a debatable issue. The aim of this study was to investigate the myocardial calcium content and intracellular calcium distribution in end-stage dilated cardiomyopathy. The explanted hearts of 13 patients (9 male, 4 female, mean age 49 ± 12 years) undergoing heart transplantation because of end-stage dilated cardiomyopathy were examined. Samples were obtained from the right and left ventricular free wall and from the septum. Calcium and magnesium content were measured by atomic absorption spectrophotometry. Ultrastructural calcium distribution was examined in dilated cardiomyopathy using the phosphate-pyroantimonate method. Ultrastructural calcium distribution was also examined in left ventricular biopsies obtained from 3 patients (male, mean age 47 ± 3.6 years) with nonfailing hearts. The number of mitochondrial calcium precipitates was estimated morphometrically by a point counting method. Myocardial calcium and magnesium content in dilated cardiomyopathy did not differ significantly among the right and left ventricles and septum ranging from 8.5 to 10.8 mmol/kg dry weight. The phosphate-pyroantimonate method visualized calcium precipitates being confined to the sarcolemma, T-tubules, intercalated disks, and mitochondria in both nonfailing myocardium and dilated cardiomyopathy. Because mitochondria may act as buffers of cytoplasmic calcium, mitochondrial calcium precipitates served as a criterion for a possible cellular calcium overload. No differences in the amount of mitochondrial calcium deposits were observed between dilated cardiomyopathy and nonfailing hearts. The data suggest that there is no global myocardial calcium overload in human eng-stage dilated cardiomyopathy.

GENDER DIFFERENCES IN PATIENTS WITH CARDIOGENIC SHOCK COMPLICATING MYOCARDIAL INFARCTION: A SUBSTUDY OF THE IABP-SHOCK II-TRIAL

Cardiogenic shock (CS) complicating acute myocardial infarction is strongly associated with mortality. Even though there has been previous research regarding gender specific differences in these patients, the results so far are conflicting and, moreover, there is insufficient data for the

Cyclosporine A increases the intracellular free calcium concentration in electrically paced isolated rat cardiomyocytes

The effect of cyclosporine on the mean cytoplasmic free calcium concentration in electrically paced single cardiomyocytes from adult rats was studied. Cardiac myocytes were paced by electrical field stimulation with either 2 or 3 Hz in the presence of 5 micrograms/ml cyclosporine or the solvent cremophor. Exposure to cyclosporine during 40 minutes of electrical pacing caused irreversible hypercontracture in most cells, only 22.1% +/- 1.2% (mean +/- SEM) remained rod-shaped versus 64.1% +/- 3.2% in the solvent (p = 0.01). The cytoplasmic free calcium concentration was measured by means of digital image processing of fura-2 fluorescence. Electrical field stimulation increased the cytoplasmic free calcium from 69.7 +/- 5.4 to 124.9 +/- 24.5 nmol/L Ca2+ in the presence of the solvent and from 84.2 +/- 25.4 to 250.1 +/- 55.9 nmol/L in the presence of cyclosporine (p = 0.036 versus solvent). The data provide direct evidence that cyclosporine enhances the cytoplasmic free calcium concentration in single paced rat cardiomyocytes. These findings may be of importance in the consideration of a possible cardiotoxicity of cyclosporine.

Effect of Nebivolol on Survival of Cardiomyopathic Hamsters with Congestive Heart Failure

SummaryThe effect of nebivolol treatment on the survival of cardiomyopathic hamsters (BIO82.62) who had developed congestive heart failure was investigated. Five percent of the hamsters included in the study had died between 200 and 220 days of age, indicating development of congestive heart failure. At age 220 days, a treatment protocol was initiated and the remaining animals received either nonmedicated food (n = 34) or food supplemented with nebivolol (1 mg/kg/day, n = 33). The death rate was similar in both groups during the first 27 days of treatment, after which nebivolol significantly delayed mortality (p = 0.011). The median survival time was 293 days in controls vs 321 days in the nebivolol group. It is concluded that nebivolol prolongs survival in this animal model of congestive heart failure, although further investigation is needed to clarify the mechanism of action.