Age peculiarities of changes in the contractile function of isolated rat hearts during prolonged perfusion

A selective and sensitive assay for the determination of TNP-470 and two of its metabolites, AGM-1883 and M-II, in human plasma was developed. The assay involved liquid-liquid extraction followed by analysis using high-performance liquid chromatography-atmospheric pressure chemical ionization tandem mass spectrometry. Because TNP-470 is most stable in a pH of 4-5, an acidification procedure was utilized to prevent degradation of TNP-470 during sample collection which involved acidifying the whole blood sample collected with 5 mg of citric acid per ml of blood. Liquid-liquid extraction using an organic solvent mixture was chosen over solid-phase extraction to minimize the degradation of TNP-470 during solvent evaporation.     

Refractory angina despite patent coronary artery bypass grafts: treatment with transmyocardial laser revascularization and scintigraphic evidence of improved myocardial perfusion

Erdheim-Chester disease is a rare sporadic systemic histiocytic disease of unknown aetiology that affects multiple organ systems. The case records of all patients with Erdheim-Chester disease who had been seen at the Mayo Clinic between 1975 and 1996 were reviewed to assess the neurological manifestations of the disease. Two of 10 patients had neurological involvement. A 42 year old woman developed central diabetes insipidus and a progressive cerebellar syndrome. Brain MRI showed a lesion in the left pons with patchy gadolinium enhancement and T2 weighted signal abnormalities extending into both cerebellar peduncles and the medulla. Biopsy of the brainstem mass showed a xanthogranulomatous lesion. The second patient was a 53 year old man with retroperitoneal fibrosis secondary to xanthogranulomatous infiltration. Although he had no neurological symptoms and a normal neurological examination, MRI of the head showed multiple uniformly enhancing extra-axial masses along the dura of both convexities and the falx, and a mass in the left orbital apex. Both patients had the characteristic radiographic and bone scan findings of Erdheim-Chester disease. Review of the literature disclosed a wide variety of neurological manifestations in Erdheim-Chester disease. The most frequent CNS manifestations are diabetes insipidus, cerebellar syndromes, orbital lesions, and extra-axial masses involving the dura.     

Detection and assessment of laser-mediated injury in transmyocardial revascularization

When channels are made through the myocardium with a laser, tissue surrounding the channels is injured. Thus, methods of examining and quantifying the histologic changes caused by laser-mediated injury are required both for comparison of different channel making protocols and also to help understand the mechanisms of transmyocardial revascularization. The two principal components of the myocardium, collagen and muscle, are both normally birefringent. This optical property can be exploited with the use of polarized light microscopy to assess tissue structure at the cellular and subcellular levels allowing several different types of injury to be detected. Increases in tissue temperature above 60 degrees C for muscle and 70 degrees C for collagen decrease their birefringence and, hence, result in decreased brightness when viewed with polarized light. Lower temperatures may cause cell membrane injury, calcium overload, and the formation of contraction bands, which appear as areas of increased birefringence. In this way, the extent of thermal injury can be assessed. The same optical properties can be used to measure cell and fiber orientation and, hence, enable assessment of mechanical disruption of the tissue after ablation. Long-term remodeling of the myocardium in the form of scar formation, increased interstitial fibrosis, and muscle disarray can also be quantified. The ability to measure the acute injury and the long-term structural consequences of that injury with the use of polarized light microscopy should prove vital in determining the optimal laser "dose" required and may also reveal information on the mechanism(s) of benefit found with transmyocardial revascularization.     

Assessment of transmural distribution of myocardial perfusion with contrast echocardiography

BACKGROUND: We hypothesized that by using our newly defined method of destroying microbubbles and measuring their rate of tissue replenishment, we could assess the transmural distribution of myocardial perfusion. METHODS AND RESULTS: We studied 12 dogs before and after creation of left anterior descending coronary artery stenoses both at rest and during hyperemia (n=62 stages). Microbubbles were administered as a constant infusion, and myocardial contrast echocardiography (MCE) was performed with the use of different pulsing intervals. The video intensity versus pulsing interval plots derived from each myocardial pixel were fitted to an exponential function: y=A(1-ebetat), where A reflects microvascular cross-sectional area (or myocardial blood volume), and beta reflects mean myocardial microbubble velocity. The product A . beta represents myocardial blood flow (MBF). Average values for these parameters were derived from the endocardial and epicardial regions of interest placed over the left anterior descending coronary artery bed. Radiolabeled microsphere-derived MBF was also measured from the same regions. There was poor correlation between radiolabeled microsphere-derived MBF and A-endocardial/epicardial ratios (EER) (r=0.46). The correlation with beta-EER was better (r=0. 69, P<0.01). The best correlation with radiolabeled microsphere-derived MBF-EER was noted with A . beta-EER (r=0.88, P<0. 01). CONCLUSIONS: The transmural distribution of myocardial perfusion can be accurately assessed with MCE with the use of our newly described method of tissue replenishment of microbubbles after their ultrasound-induced destruction. In the model studied, an uncoupling of the transmural distribution of MBF and myocardial blood volume was observed during reversal of the MBF-EER.     

Assessment of myocardial perfusion hemodynamics using echo planar MR imaging

It was possible to obtain images for individual heart beats using single-shot Echo Planar Imaging(EPI), and changes of myocardial signal intensity could be assessed visually after GD-DTPA administration. Measurement of the same site in the myocardium on myocardial perfusion images for individual heart beats was facilitated by imaging during breath-holding, and accurate evaluation was possible. In patients with coronary artery disease, the site of myocardial infarction tended to show less increase in signal intensity than the normal myocardium, and could easily be distinguished from normal myocardium according to the change in signal intensity. In patients with atrial fibrillation, the signal intensity of the myocardium varied with each heart beat, and it was difficult to assess perfusion hemodynamics. Myocardial perfusion studies using EPI still present problems with respect to spatial resolution, but the myocardial perfusion hemodynamics for individual heart beats can be determined by preparing time/intensity curves. It is also possible to obtain information on cardiac morphology, wall motion, and myocardial metabolism in addition to perfusion data by combining myocardial perfusion studies with methods such as high speed cine MRI, tagging, or myocardial MRS. It is possible that this method will also be useful in studying myocardial viability.     

Neovascularization after transmyocardial laser revascularization in a model of chronic ischemia

BACKGROUND: The mechanism of clinical improvement after transmyocardial laser revascularization (TMR) is unknown. One hypothesis holds that TMR causes increased myocardial perfusion through neovascularization. This study sought to determine whether angiogenesis occurs after TMR in a porcine model of chronic myocardial ischemia. METHODS: Six miniature pigs underwent subtotal left circumflex coronary artery occlusion to reduce resting blood flow to 10% of baseline. After 2 weeks in the low-flow state, dobutamine stress echocardiography and positron emission tomography were performed to document ischemic, viable myocardium. The animals then underwent TMR and were sacrificed 6 months later for histologic and immunohistochemical analysis. RESULTS: Histologic analysis of the lased left circumflex region demonstrated many hypocellular areas filled with connective tissue representing remnant TMR channels. Histochemical staining demonstrated a highly disorganized pattern of neovascularization consistent with angiogenesis located predominantly at the periphery of the channels. Immunohistochemical analysis confirmed the presence of endothelial cells within neovessels. Vascular density analysis revealed a mean of 29.2+/-3.6 neovessels per high-power field in lased ischemic myocardium versus 4.0+/-0.3 (p<0.001) in nonlased ischemic myocardium. CONCLUSIONS: This study provides evidence that neovascularization is present long term in regions of ischemic, viable myocardium after TMR. Angiogenesis may represent the mechanism of clinical improvement after TMR.     

Acceleration of widespread adenoviral gene transfer to intact rabbit hearts by coronary perfusion with low calcium and serotonin

Previous attempts at adenoviral gene transfer to the intact heart have been limited by the requirement for prolonged exposure to high virus concentrations. In an ex vivo coronary perfusion model of intact adult rabbit hearts, we previously reported gene transfer to 96% of cardiac myocytes after a 60 min exposure to 1.6 x 10(9) p.f.u./ml Ad beta gal, a recombinant adenovirus encoding beta-galactosidase. Here we sought to decrease the virus exposure time by enhancing microvascular permeability to increase the efficiency of adenoviral gene transfer. Baseline perfusion with 1.0 x 10(8) p.f.u./ml Ad beta gal in normal Krebs solution (1 mM calcium) caused infection of 22% of myocytes at 30 min and 40% at 60 and 120 min. Increasing the virus concentration, decreasing perfusate calcium concentration, or pretreating with serotonin or bradykinin in Krebs solution or L-NAME in heparinized rabbit blood significantly decreased the necessary exposure time. Under optimal conditions of serotonin pretreatment, 50 mumol/l perfusate calcium, and a virus concentration of 1.6 x 10(9) p.f.u./ml, 2 min of coronary perfusion sufficed to produce near-total infection. This profound enhancement of infection parameters has important implications for in vivo myocardial gene transfer, where a similar strategy could facilitate gene therapy for common myocardial disorders.     

A review of the literature: transmyocardial laser revascularization

Cavernous hemangiomas are vascular malformations of the central nervous system that may rarely affect the epidural space of the spine. We report a case of an epidural cavernous hemangioma which was originating from the left C8 nerve root and extending anteriorly to the apex of the left lung.     

Effects of vasodilators and perfusion pressure on coronary flow and simultaneous release of nitric oxide from guinea pig isolated hearts

OBJECTIVE: The aims were to validate the use of a direct reading NO electrode, to compare the effects of diverse acting drugs on altering coronary flow (CF) and NO release, and to examine the effects of altered perfusion pressure on flow-induced changes in NO concentration [NO] in the hemoglobin free effluent of guinea pig isolated hearts. METHODS: Hearts were isolated and perfused initially at a constant perfusion pressure (55 mmHg) with a modified Krebs-Ringer's solution equilibrated with 97% O2 and 3% CO2 at 37 degrees C. Heart rate, left ventricular pressure, CF, and effluent pH, pCO2, pO2, and NO generated current were monitored continuously on-line. Effluent was sampled for L-citrulline. Percent O2 extraction and O2 consumption were calculated. [NO] was quantitated with a sensitive amperometric sensor (sensitivity > or = 1 nmol/l approximately 3 pA) and a selective gas permeable membrane. RESULTS: The electrode was not sensitive to changes in solution pO2, flow, or pressure. The electrode was sensitive to pCO2 (-0.50 nmol/l/mmHg) and temperature (+24.5 nmol/l/degree C), so coronary effluent pCO2 was measured to compensate for a small decrease in pCO2 that occurred with an increase in coronary flow, and effluent temperature was rigidly controlled. Serotonin, bradykinin, and nitroprusside increased NO release along with CF, whereas nifedipine, butanedione monoxime, zaprinast, and bimakalim comparably increased CF but did not increase [NO] or NO release. Increases in CF (ml/g/min) and NO release (pmol/g/min), respectively, were 5.0 +/- 1 and 100 +/- 17 for 1 mumol/l serotonin, 7.5 +/- 1 and 148 +/- 18 for 100 nmol/l bradykinin, and 7.8 +/- 1 and 173 +/- 28 for 100 mumol/l nitroprusside. The increases in effluent NO by bradykinin were proportional to the increases in L-citrulline. Tetraethylammonium decreased CF, but did not change NO release, indomethacin changed neither CF nor NO release, and NG-nitro-L-arginine methyl ester (L-NAME) reduced CF by 2.6 +/- 1 ml/g/min and NO release by 25 +/- 8 pmol/g/min. An increase of CF of 8.0 +/- 0.3 ml/g/min, produced by increasing perfusion pressure from 25 to 90 mmHg, increased [NO] by 30 +/- 4 nmol/l; L-NAME but did not reduce the pressure-induced increase in CF, but reduced the increase in [NO] to 10 +/- 5 nmol/l. CONCLUSIONS: This study demonstrates in intact hearts real-time release of NO by several vasodilator drugs and by pressure-induced increases in flow (shear stress) and attenuation of these effects by L-NAME.     

Effects of L-arginine and N omega-nitro-L-arginine methyl ester on cardiac perfusion and function after 1-day cold preservation of isolated hearts

BACKGROUND: Coronary flow responses to endothelium-dependent (acetylcholine [ACh] or 5-hydroxytryptamine [5-HT]) and endothelium-independent (adenosine [ADE] or nitroprusside [NP]) vasodilators may be altered before and after 1-day hypothermia during the perfusion of arginine vasopressin (AVP), D-arginine (D-ARG), L-arginine (L-ARG), or nitro-L-arginine methyl ester (L-NAME). METHODS AND RESULTS: Four groups of guinea pig hearts (37.5 degrees C [warm]) were perfused for 6 hours with AVP, L-ARG, L-NAME, or nothing (control). Five heart groups (cold) were perfused with AVP, D-ARG, L-ARG, L-NAME, or nothing (control), but after 2 hours they were perfused at low flow for 22 hours at 3.7 degrees C and again for 3 hours at 37.5 degrees C. ADE, butanedione monoxime, and NP were given for cardioprotection before, during, and after hypothermia. In warm groups, L-ARG did not alter basal flow or ADE, ACh, 5-HT, or NP responses, whereas L-NAME and AVP reduced basal flow and the ADE response, abolished ACh and 5-HT responses, and increased the NP response. In cold groups after hypothermia. L-ARG did not alter basal flow, but L-NAME, AVP, D-ARG, and control reduced flow. In the postcold L-ARG group, ACh increased peak flow, but NP did not increase flow in other cold groups. Effluent L-ARG and L-CIT in the cold control group fell from 64 +/- 9 and 9 +/- 1 micrograms/L at 1 hour to 36 +/- 5 and 5 +/- 1 micrograms/L at 25 hours, respectively. Left ventricular pressure and cardiac efficiency improved more in the postcold L-ARG group than in the postcold D-ARG, AVP, and L-NAME groups. CONCLUSIONS: Endogenous effluent levels of L-ARG and L-CIT decrease after 24 hours in isolated hearts, whereas perfusion of L-ARG improves cardiac performance, basal coronary flow, and vasodilator responses. In contrast, L-NAME, L-ARG, and AVP limit flow and performance but maintain a partial vasodilatory response to NP. Sustained release of NO may account for improved performance after L-ARG after hypothermia.     

Color coded ultrasound--quantification of perfusion in a perfusion model

One patient with acute and transient functional psychosis was assessed repeatedly using a brief neuropsychological assessment during his recovery from the psychotic episode. The psychotic features of the patient were characterized by perplexed behavior, attentional disturbance and emotional turmoil. Characteristic findings, including impairment of attention tests, dysgraphia and constructional disturbances, were seen. Findings improved in accordance with recovery on a behavioral level. We discussed the similarity of neuropsychological and behavioral abnormalities of this patient and those of patients in an acute confusional state.     

Assessment of brain perfusion by 99mTc-HMPAO SPECT in akinetic mutism due to high-dose intravenous methotrexate therapy

Chemotherapy of the central nervous system may cause neurotoxicity in children with acute lymphocytic leukemia. We evaluated regional blood flow in a 6-year-old child presenting with akinetic mutism, using 99mTc-HMPAO single photon emission tomography (SPECT) following high-dose intravenous methotrexate therapy. While findings in X-ray computerized tomography were decreased density in bilateral basal ganglia and thalamic nuclei with diffusely decreased attenuation of the periventricular white matter, a global, frontal dominant profoundly abnormal perfusion pattern involving both gray and white matter was observed in the SPECT study. Treatment of the central nervous system with high dose intravenous chemotherapy may cause profound abnormalities in white and gray matter blood flow and early assessment of the neurotoxicity may be identified by 99mTc-HMPAO SPECT in the pediatric age group.     

Histologic appearance of transmyocardial laser channels after 4 1/2 weeks

Preliminary results of clinical studies suggest that transmyocardial laser revascularization is an effective treatment for patients with chronic angina that cannot be treated by other means. The mechanism of this effect remains controversial. We present autopsy results from a patient obtained 4 1/2 weeks after operation that show that the channels do not maintain patency. Further work is needed to determine the frequency of channel patency and its relation to clinical benefit.     

Control of growth in neonatal pig hearts

The pig heart grows at a maximal rate in the first 2-3 days of life due to a volume overload imposed on the heart at birth. Rates of ribosome formation and protein synthesis cannot be further accelerated during in vitro perfusion with agents that increase cyclic AMP, that bind to alpha 1-adrenergic receptors or that bind to angiotensin II receptors. Growth of the heart in vivo can be restrained by treatment with an angiotensin-converting enzyme inhibitor, enalapril maleate, or an angiotensin receptor antagonist, DuP 753. In the enalapril-treated heart, norepinephrine plus propranolol, but not angiotensin II, accelerated ribosome formation. Rapid growth of the left ventricle of pig heart during the first 10 days of life is due largely to eccentric hypertrophy.