Ultrastructural effects induced by global ischaemia on the AV node compared with the working myocardium. A qualitative and morphometric investigation on the canine heart

Cellular edema and alterations in metabolite content in the ischemic and reperfused canine heart following different forms of cardiac arrest

This study investigates firstly how far cellular edema correlates with parameters of the anaerobic energy turnover independent of the method used for cardiac arrest, and secondly to what extent cellular edema developing during reversible global ischemia is reduced after reperfusion. Canine hearts were arrested 1. by aortic cross clamping (ACC), 2. by coronary perfusion with St. Thomas solution, or 3. HTK (histidine tryptophan ketoglutarate) solution (Custodiol). Samples for biochemical and structural analysis were taken at different times during ischemia and after reperfusion with Tyrode solution. Cellular edema determined morphometrically and given as volume ratio of sarcoplasm and mitochondria to myofibrils (Vvsp + V vmi/Vvmf) varies significantly in the differently arrested hearts. Reperfusion after a decrease in ATP to 4 mumol/gww (revival time) leads to a nearly complete structural recovery. The relationship between cellular edema and defined over-all metabolite tissue concentrations and extracellular pHe values shows: 1. during the decrease of creatine phosphate to 3 mumol/gww, cellular edema does not change; it is, however, significantly higher after ACC and St. Thomas than after HTK perfusion; 2. at each lactate concentration, cellular edema differs significantly depending on the form of cardiac arrest; 3. during the decrease of ATP and pHe cellular edema increases and is comparable at concentrations < 4 mumol/gww and at pHe values < 6.5 independent of the form of cardiac arrest; 4. beyond 10 mumol/gww of inorganic phosphate (Pi), increasing values for cellular edema correspond to defined Pi values in the differently arrested hearts. Thus, the ratio VVSp+ VVMi/VVMf is a powerful parameter for the determination of cellular edema during ischemia, as well as for correlations with metabolic parameters.

Microquantitative determination of lactate dehydrogenase isoenzymes in the myocardium and the conducting system

A newly developed technique was used for the electrophoretic separation of lactate dehydrogenase (LDH) isoenzymes from lyophilized tissue samples in the nanogram range. In this study portions of 10-200 ng from the myocardium and the conducting system of cattle, sheep, pig and man were microdissected and analysed. In the heart tissues of cattle, sheep and pig, the isoforms LDH1, LDH2 and LDH3 were detected in species-specific varying amounts. In all these animals, the conducting system is marked by high LDH1 activity, which is present at a ratio of about 2:1 compared with the myocardium. The values in man, however, differ from these values, but this might be due to post-mortem changes. The findings are discussed with respect to possible aerobic-anaerobic functions.

Pediatric heart transplantation for congenital heart disease and cardiomyopathy

Orthotopic heart transplantation has become an accepted therapy for adult patients with end-stage heart disease. In newborns and infants, this procedure is still controversial because of the unknown long-term results and the lack of donor organs. Since March 1988, we have performed orthotopic heart transplantation in 11 infants and children with hypoplastic left heart syndrome (n = 6), cardiomyopathy (n = 4), or congenital endocardial fibroelastosis (n = 1). The smallest infant was 3 days old and weighed 2,650 g. Four of 15 potential donors had to be refused for various medical reasons, and 4 were transferred to our hospital for organ retrieval. Seven hearts were procured remotely. We accepted weight mismatches up to 105% between donor and recipient. There were three perioperative deaths, two in patients 5 and 17 days old with hypoplastic left heart syndrome and 1 in a 2-year-old patient with a dilated cardiomyopathy. All 3 patients had drug-resistant right heart failure. A 2-year-old girl with a dilated cardiomyopathy died 2 months after transplantation owing to severe pulmonary embolism originating from the superior vena cava. The remaining 7 patients are alive and well between 1 month and 31 months after transplantation. Angiographic follow-up has not revealed signs of graft atherosclerosis at 2 years.

Application of a CCD linear array camera in the quantification of tissue staining: NBT detection in ischaemic myocardium

A method was developed to quantify the intensity of tissue staining using a CCD (charge-coupled device) camera. Reflection spectra of NBT-stained (nitro-blue tetrazolium-stained) and unstained myocardium were recorded via fibre optics coupled to a CCD camera, connected to a microcomputer. The calculation of the intensity of staining was based on evaluation of the NBT-related changes of the reflectance spectrum. In each of six anaesthetized sheep, global ischaemia was induced by cross-clamping of the aorta. The hearts were removed and incubated at 35 degrees C. At predetermined times two sections of ventricular myocardium were taken, one of which was then stained with NBT, the other being left unstained. Evaluation of the reflectance spectra from stained sections during the first phase of ischaemia showed a slight loss of NBT colour intensity followed by a more rapid loss of staining until the values of the unstained sections were reached. In contrast to the conventional visual evaluation, the method provides quantitative data on the intensity of staining, and allows use of the NBT technique for statistical evaluation of what happens over time, and the regional distribution of ischaemic injury of tissue. This method may also be applied to other staining techniques.

Improved preservation of phospholipid-rich multilamellar bodies in conventionally embedded mammalian lung tissue--an electron spectroscopic study

Different conventional methods of tissue processing were studied to determine the extent to which phospholipid-rich multilamellar bodies of pulmonary alveolar epithelial type II cells of the pig were preserved. Prolonged treatment with half-saturated aqueous uranyl acetate yielded excellent results on the stabilization of the multilamellar substructure, irrespective of whether glutaraldehyde-paraformaldehyde or glutaraldehyde-tannic acid was used as a primary fixative. The lamellar periodicities were observed to be 5.5-6.1 nm. Differences in the phosphorus distribution among several types of lipid bodies of alveolar epithelial type II cells were studied by means of electron spectroscopic imaging and electron energy-loss spectroscopy. Multilamellar bodies gave phosphorus signals which were significantly higher than those obtained from granular regions of composite bodies, whereas homogeneous bodies gave phosphorus signals which were even lower than those obtained from mitochondria, endoplasmic reticulum membranes or ribosomes.

The ultrastructural effects of global ischaemia on Purkinje fibres compared with working myocardium: a qualitative and morphometric investigation on the canine heart

During open heart surgery, reperfusion-induced arrhythmias arising after short periods of ischaemia may originate from subendocardial Purkinje fibres. We investigated the ultrastructure of these fibres during 30 min of global ischaemia at 25 degrees C. The effects both with myocardial protection (HTK cardioplegia) and without it (pure ischaemia) were compared qualitatively and morphometrically. After 30 min pure ischaemia overcontraction of sarcomeres, hypercontraction and contraction bands, together with considerable changes in organelles, predominate over cellular oedema. In Purkinje fibres, both cellular and mitochondrial swelling were significantly increased within this 30-min time period from the onset of pure ischaemia. In contrast, following HTK cardioplegia and 30 min ischaemia, cellular and mitochondrial swelling remain moderate and over-contractions are almost entirely lacking. This means that despite remarkable differences between pure ischaemia and HTK cardioplegia in the degree of protection attained it is clear that, compared with the working myocardium, subendocardial Purkinje fibres do not display a higher resistance to early global ischaemia. Further investigations of this sensitivity of Purkinje fibres to global ischaemia and certain drugs may bring about new insights into myocardial protection and pharmacotherapy of arrhythmias.

Occurrence and prevention of contraction bands in Purkinje fibres, transitional cells and working myocardium during global ischaemia

Contraction bands usually occur in the intramural working myocardium following post-ischaemic reperfusion. In the subendocardium, however, they are found during ischaemia. Thus, we ascertained the contraction states of Purkinje fibres, transitional cells, subendocardial and intramural parts of the working myocardium during 30 min global ischaemia at 25 degrees C. The effects with and without myocardial protection were compared. At the onset of pure ischaemia contraction bands are completely lacking in all cell types. During pure ischaemia contraction bands are found in all subendocardial cell types but not in the intramural working myocardium. A peak of pathological contraction states is found in the intramural working myocardium at the onset (0 min), in the subendocardial working myocardium at 10 min, in the transitional cells and Purkinje fibres at 30 min of pure ischaemia. Histidine-, tryptophan-, ketoglutarate-enriched (HTK) cardioplegia prevents contraction bands completely at the onset of ischaemia and prevents both contraction bands and pathological contraction states during ischaemia almost completely. Striking differences in the physiological contraction states are seen only in the working myocardium: HTK cardioplegia brings about dominance of relaxation during ischaemia. These findings may be due mainly to the effects of global ischaemia on the one hand and to catecholamines, calcium and oxygen on the other.