Microvascular spasm in the cardiomyopathic Syrian hamster: a preventable cause of focal myocardial necrosis

Cardiac disease in transgenic mice expressing human immunodeficiency virus-1 nef in cells of the immune system

We previously reported that a severe acquired immune deficiency syndrome-like disease develops in transgenic (Tg) mice expressing the human immunodeficiency virus-1 in its natural target cells: immature and mature CD4(+) T cells and cells of the macrophage/dendritic lineage. Here, we show that these mice also develop cardiac disease, characterized most prominently by a focal myocytolysis, occasionally by myocarditis and by deposition of endogenous immunoglobulin on cardiomyocytes. Microfil perfusion demonstrated widespread coronary arteriospasm and echocardiographic analysis revealed depressed cardiac function in Tg mice. A higher (but still modest) level of cardiomyocyte apoptosis was detected in Tg as compared to non-Tg hearts. Tg expression was detected in some of the infiltrating mononuclear cells, but not in cardiomyocytes or in cells of the heart vessels, suggesting a human immunodeficiency virus-1-induced disease process mediated by cells of the immune system. The similarity of the heart disease observed in these Tg mice to that observed in acquired immune deficiency syndrome patients suggests a common pathogenesis.

T-1032, a novel phosphodiesterase type 5 inhibitor, increases the survival of cardiomyopathic hamsters

To evaluate the influence of T-1032 (methyl2-(4-aminophenyl)-1,2-dihydro-1-oxo-7-(2-pyridylmethoxy)-4-(3,4,5-trimethoxyphenyl)-3-isoquinoline carboxylate sulfate), a potent and relatively selective phosphodiesterase 5 inhibitor, on chronic heart failure, we examined the acute hemodynamic profile of T-1032 and its chronic effect on the survival of Bio 14.6 cardiomyopathic hamsters. In the acute study, T-1032 (1, 10, 100 microg/kg) was administered intravenously by means of a dose-escalating procedure in 55-week-old hamsters. T-1032 significantly reduced both the right and left ventricular end-diastolic pressure in a dose-dependent manner. T-1032 modestly reduced the systemic arterial pressure at the highest dose (100 microg/kg i.v.). T-1032 did not change the heart rate or left ventricular dp/dt(max). In the survival study, chronic administration of T-1032 (50 and 500 ppm in a diet) increased survival, and the survival rate was 24.2%, 45.4% and 48.5% in the control, 50 and 500 ppm-treated groups, respectively. The median survival was 55, 58 and 58 weeks in control, 50 and 500 ppm-treated groups, respectively. Analysis of the survival curves revealed that T-1032 (500 ppm) significantly increased the survival of these hamsters (P<0.05 vs. control). It was concluded that T-1032 had beneficial hemodynamic effects on heart failure in Bio 14.6 cardiomyopathic hamsters, and the favorable hemodynamic changes induced by T-1032 were partly related to the increase in the survival of these hamsters. Phosphodiesterase type 5 inhibitors may have therapeutic potential for the treatment of chronic heart failure.

Innovative drug treatments for viral and autoimmune myocarditis

Myocarditis is a common cause of cardiomyopathy and is thought to account for 25% of all cases in humans. Unfortunately, the disease is difficult to detect clinically before a myopathic process ensues. Management of myocarditis-induced heart failure includes the standard regimen of diuretics, digoxin, angiotensin-converting enzyme inhibitors, angiotensin-II receptor blockers, and beta-adrenergic blockers. The management of myocarditis itself is dependent on the etiology of the illness. Treatments that are currently under investigation include immunosuppressants, nonsteroidal antiinflammatory agents, immunoglobulins, immunomodulation, antiadrenergics, calcium-channel blockers, angiotensin-converting enzyme inhibitors, nitric oxide inhibitors (e.g., aminoguanidine), and antivirals. Despite advances in treatment, more work needs to be done in the early detection of myocarditis. Additionally, better means need to be established for distinguishing between viral and noninfectious autoimmune forms of the disease, so that appropriate treatment can be instituted.

Treatment of heart failure in patients with diabetes mellitus

Patients with diabetes mellitus have an increased morbidity and mortality from cardiovascular disease. Both coronary artery disease and congestive heart failure (CHF) are largely responsible for the increased cardiovascular adverse events in patients with diabetes. This review discusses the pathophysiology of CHF, the mechanisms of left ventricular (LV) dysfunction and the neurohormonal mechanisms involved in both LV dysfunction and CHF. Diabetes with and without hypertension is an important cause of LV dysfunction and CHF. Diabetes may be responsible for the metabolic and ultrastructural causes of LV dysfunction, while hypertension may be responsible for the marked fibrotic changes that are found. Experimental induction of diabetes in animals has shed light on the biochemical and ultrastructural changes seen. The role of insulin to reverse both metabolic and structural changes is reviewed both from experimental data and with the limited amount of clinical data available. The therapy of CHF in patients with diabetes is similar to that of patients without diabetes, with therapy directed toward the use of beta-blockers and angiotensin converting enzyme (ACE) inhibitors. As the morbidity and mortality are higher in patients with diabetes, several studies have pointed out the importance of this subgroup where the opportunity to make a significant clinical impact exists. A significant opportunity exists to reduce morbidity and mortality with beta-blockers and ACE inhibitors when ischaemia and CHF are both present. However, studies in patients diabetes have been limited to post hoc subgroup analyses and rarely as predefined subgroups. Clinical trials involving patients with diabetes with and without hypertension and LV dysfunction are clearly needed in the future to adequately address the needs of this high risk subgroup.

Altered coronary and cardiac adrenergic response in the failing hamster heart: role of cyclooxygenase derivatives

Although the influence of the adrenergic system has been studied in the presence of heart failure, controversies still exist. Since cyclooxygenase derivatives appear to modulate coronary and cardiac adaptation in the failing heart, we hypothesized that cyclooxygenase derivatives may participate in the altered adrenergic responses in this situation. Isolated hearts from cardiomyopathic (UM-X7.1 subline) and normal hamsters, aged > 240 days, were utilized. Coronary and cardiac response to alpha1-, beta1-, and beta2-adrenergic stimulations was observed before and after pretreatment with indomethacin, a cyclooxygenase inhibitor. Reduction of coronary flow elicited by alpha1-adrenergic stimulation was unchanged in the presence of heart failure, while beta1- and beta2-induced vasodilatations were reduced. Inotropic response to alpha1 and beta1 stimulations were also reduced in failing hearts, while beta2-adrenergic action was unchanged. Pretreatment with indomethacin exacerbated coronary flow reduction observed with alpha1 stimulation in failing hearts only. Beta2-induced coronary vasodilatation and inotropic response to alpha1 and beta2 stimulations were impaired similarly in the presence of indomethacin in normal and failing hearts. The results suggest a complex interaction between adrenergic and cyclooxygenase activation.

Coronary endothelial dysfunction and myocardial cell damage in chronic stable idiopathic dilated cardiomyopathy

Impairment of endothelium-dependent vasodilatation in response to acetylcholine reflects an abnormal endothelial function. Labelled indium-111 monoclonal antimyosin antibodies enable detection of myocardial cell damage. We analysed whether endothelial dysfunction correlates with myocardial antimyosin uptake in a selected group of patients with idiopathic dilated cardiomyopathy.

METHODS

Twenty-two consecutive patients with chronic stable idiopathic dilated cardiomyopathy (18 males and four females) were included. The duration of heart failure symptoms was 46+/-34 months. At inclusion, the functional class of New York Heart Association was 2.1+/-0.7. Endothelial function was evaluated using intracoronary graded concentrations of acetylcholine. Vasomotor responses of the left anterior descending coronary artery were measured by quantitative coronary analysis. Myocardial uptake of antimyosin antibodies was quantified by means of a heart-to-lung ratio (HLR).

RESULTS

Eighteen patients showed endothelial dysfunction (82%) and the remaining four patients showed a normal endothelial function. There were no statistically significant differences between patients with and without endothelial dysfunction in relation to clinical, echocardiographic and hemodynamic parameters. In addition, these variables did not correlate with the magnitude of the vasomotor response to acetylcholine. Eighteen patients (82%) showed abnormal antimyosin uptake; 15 of them (83%) showed endothelial dysfunction. The global mean HLR of antimyosin uptake was 1.73+/-0.24. The coronary vasomotor response to acetylcholine correlated with the intensity of uptake of antimyosin antibodies (r=-0.45, P<0.04).

CONCLUSIONS

Coronary endothelial dysfunction and myocardial antimyosin uptake was found in a high percentage of patients with chronic stable idiopathic dilated cardiomyopathy. The abnormal vasomotor response seems to be related to the degree of myocardial damage.

Cardioprotective effects of verapamil on myocardial structure and function in a murine model of chronic Trypanosoma cruzi infection (Brazil Strain): an echocardiographic study

Verapamil has been shown to attenuate the extent of myocardial injury in murine models of chronic Trypanosoma cruzi infection. Infected mice treated with verapamil have significantly lower myocardial expression of inducible nitric oxide synthase and cytokines and substantially less inflammatory infiltrate and myocyte necrosis at necropsy. In the present study, we examined the cardiac structural and functional correlates of verapamil treatment in CD1 mice infected with the Brazil strain of T. cruzi using serial transthoracic echocardiography. There were four groups: uninfected- untreated control, uninfected-verapamil-treated, infected-untreated control, and infected-verapamil-treated. Verapamil was given in drinking water (1 gm/l) continuously from the day of infection for a total of 120 days. Mice were evaluated at baseline, 40 and 150 days p.i. Mice in the untreated-infected group compared with the mice in the infected-verapamil-treated group showed thinning of the left ventricular wall (0.84 +/- 0.02-vs-0.92 +/- 0.04, P<0.05 mm), increase in the left ventricular end-diastolic diameter (3.27 +/- 0.15-vs-2.74 +/- 0.05 mm, P<0.05) and reduction in percent fractional shortening (37 +/- 2-vs-53 +/- 4%, P<0.05). No differences in these parameters were noted among mice in the uninfected-untreated and uninfected-verapamil-treated groups. Furthermore, right ventricular dilation was more severe in mice from the infected-untreated group as compared with those in the infected- verapamil-treated group (visual grade 1.9 +/- 0.4-vs-1.0 +/- 0.2, P<0.05). At necropsy, the extent of myocardial injury, as determined histologically, was significantly greater in the infected-untreated mice. These data provide cardiac structural and functional correlates for the previously observed cardioprotective effects of verapamil in chronic chagasic cardiomyopathy.

Multiple endothelial injury in epicardial coronary artery induces downstream microvascular spasm as well as remodeling partly via thromboxane A2

OBJECTIVES

The study was undertaken to develop a coronary microvascular spasm model in pigs by repeated epicardial coronary artery endothelial injury.

BACKGROUND

The pathophysiologic mechanisms responsible for coronary microvascular spasm remain unclear, in large part because a suitable animal model has yet to be found.

METHODS

Balloon endothelial denudation was done just distal to the site of an implanted Doppler flowmeter in the left anterior descending coronary artery (LAD) every two weeks for a total of four times. Changes in LAD blood flow by intracoronary administration of vasoactive agents were assessed before each denudation.

RESULTS

In the epicardial LAD endothelial denudation pigs, decreases in LAD blood flow caused by acetylcholine were augmented. Before denudation, it was - 15 +/- 4%, and at week 8 (i.e., two weeks after the fourth denudation) it was -100% (i.e., zero flow [p < 0.01]). The LAD flow changes in response to 5-hydroxytryptamine (5-HT) changed from an increase to a decrease, accompanied by medial thickening of microvessels in the LAD perfusion area. These flow responses were observed without significant changes in LAD diameter. In contrast, the LAD blood flow responses to acetylcholine and 5-HT did not change throughout the experiment in pigs given aspirin and a thromboxane A2 (TXA2) synthase inhibitor orally.

CONCLUSIONS

This microvascular spasm model indicates that hypersensitivity to vasoactive substances in the microvascular beds as well as microvascular remodeling are brought about partly through TXA2. This model should be useful for examining the pathophysiology and treatment of microvascular angina.

BK(Ca) channels compensate for loss of NOS-dependent coronary artery relaxation in cardiomyopathy

Previously, we showed that development of myocardial necrotic lesions is associated with impaired endothelium-dependent coronary artery relaxation in young cardiomyopathic hamsters. Since active necrosis declines with aging, this study was designed to determine whether coronary artery endothelium-dependent relaxation to ACh is restored and to identify the mechanisms mediating this effect. Intraluminal diameter was recorded in coronary arteries (150-250 micrometer) from control (C, 297 +/- 5 days old) and cardiomyopathic (M, 296 +/- 4 days old) hamsters. Relaxation to ACh (10(-9)-3 x 10(-5) M) was similar in vessels from C and M hamsters. However, mechanisms mediating relaxation to ACh were altered. Inhibition of nitric oxide synthase (NOS) activity with N-nitro-L-arginine (1 mM) had a greater inhibitory effect in vessels from C hamsters, indicating a reduction in NOS-dependent relaxation in vessels from M hamsters. Conversely, inhibition of large Ca(2+)-dependent K(+) (BK(Ca)) channels with charybdotoxin (CTX, 0.1 microM) had a greater inhibitory effect in vessels from M hamsters. In the presence of both N-nitro-L-arginine and CTX, relaxation to ACh was abolished in both groups. CTX (0.1 micrometer) produced a 50 +/- 4 and 30 +/- 3% contraction of vessels from M and C hamsters, respectively, indicating an enhanced role for BK(Ca) channels in regulation of coronary artery tone in M hamsters. Finally, vasodilatory cyclooxygenase products contributed to ACh-induced relaxation in vessels from M, but not C, hamsters. In conclusion, NOS-dependent relaxation of coronary small arteries is reduced in the late stage of cardiomyopathy. An increase in relaxation mediated by BK(Ca) channels and vasodilatory cyclooxygenase products compensates for this effect.

Effects of long-term treatment with verapamil on left ventricular function and myocardial blood flow in patients with dilated cardiomyopathy without overt heart failure

Myocardial blood flow (MBF) abnormalities are present in early stage dilated cardiomyopathy (DCM) and have been attributed to coronary microvascular abnormalities. The favorable effects of verapamil on coronary microcirculation might indicate its use in early stage DCM. We assessed the safety of long-term combination therapy of verapamil and enalapril and its effects on both left ventricular function and myocardial perfusion compared with enalapril alone in 18 patients with DCM (15 men, 3 women; mean age, 50+/-9 years) without overt heart failure (NYHA class I-II). At baseline and after 6 months of randomized treatment with either enalapril (10-20 mg) (nine patients, group 1) or enalapril (10-20 mg) and verapamil (120-240 mg) (nine patients, group 2), left ventricular function was assessed at rest, during handgrip, and during bicycle exercise by equilibrium radionuclide angiography. Mean MBF was measured at rest and after dipyridamole by positron emission tomography (PET) and 13N-ammonia as a flow tracer. At baseline, the two groups had reduced left ventricular ejection fraction at rest, which was further impaired during isometric exercise, but increased at peak bicycle exercise. MBF was similarly reduced in the two groups at rest and during dipyridamole. During treatment, no adverse events occurred in either group. After 6 months there was no significant difference in the main study variables either between the two groups or within each group before and after treatment. Long-term combination therapy with verapamil and enalapril is safe in patients with DCM without overt heart failure. Despite no favorable effect on myocardial perfusion, combined treatment prevented deterioration of left ventricular function, similarly to enalapril alone.

Altered membrane proteins and permeability correlate with cardiac dysfunction in cardiomyopathic hamsters

A mutation in the delta-sarcoglycan (SG) gene with absence of delta-SG protein in the heart has been identified in the BIO14.6 cardiomyopathic (CM) hamster, but how the defective gene leads to myocardial degeneration and dysfunction is unknown. We correlated left ventricular (LV) function with increased sarcolemmal membrane permeability and investigated the LV distribution of the dystrophin-dystroglycan complex in BIO14.6 CM hamsters. On echocardiography at 5 wk of age, the CM hamsters showed a mildly enlarged diastolic dimension (LVDD) with decreased LV percent fractional shortening (%FS), and at 9 wk further enlargement of LVDD with reduction of %FS was observed. The percent area of myocardium exhibiting increased membrane permeability or membrane rupture, assessed by Evans blue dye (EBD) staining and wheat germ agglutinin, was greater at 9 than at 5 wk. In areas not stained by EBD, immunostaining of dystrophin was detected in CM hamsters at sarcolemma and T tubules, as expected, but it was also abnormally expressed at the intercalated discs; in addition, the expression of beta-dystroglycan was significantly reduced compared with control hearts. As previously described, alpha-SG was completely deficient in CM hearts compared with control hearts. In myocardial areas showing increased sarcolemmal permeability, neither dystrophin nor beta-dystroglycan could be identified by immunolabeling. Thus, together with the known loss of delta-SG and other SGs, abnormal distribution of dystrophin and reduction of beta-dystroglycan are associated with increased sarcolemmal permeability followed by cell rupture, which correlates with early progressive cardiac dysfunction in the BIO14.6 CM hamster.

Disruption of the beta-sarcoglycan gene reveals pathogenetic complexity of limb-girdle muscular dystrophy type 2E

Limb-girdle muscular dystrophy type 2E (LGMD 2E) is caused by mutations in the beta-sarcoglycan gene, which is expressed in skeletal, cardiac, and smooth muscle. beta-sarcoglycan-deficient (Sgcb-null) mice developed severe muscular dystrophy and cardiomyopathy with focal areas of necrosis. The sarcoglycan-sarcospan and dystroglycan complexes were disrupted in skeletal, cardiac, and smooth muscle membranes. epsilon-sarcoglycan was also reduced in membrane preparations of striated and smooth muscle. Loss of the sarcoglycan-sarcospan complex in vascular smooth muscle resulted in vascular irregularities in heart, diaphragm, and kidneys. Further biochemical characterization suggested the presence of a distinct epsilon-sarcoglycan complex in skeletal muscle that was disrupted in Sgcb-null mice. Thus, perturbation of vascular function together with disruption of the epsilon-sarcoglycan-containing complex represents a novel mechanism in the pathogenesis of LGMD 2E.

The potential for myocardial imaging with hypoxia markers

Direct "hot spot" imaging of myocardial tissue hypoxia is potentially of great clinical importance because available noninvasive approaches for the detection of myocardial ischemia have generally been based on the detection of flow heterogeneity or identification of regional alterations of myocardial metabolism. These existing approaches provide only an indirect assessment of regional myocardial ischemia, and may be affected by either sympathetic activation or substrate availability. The assessment of tissue oxygenation with hypoxic compounds may be the best indicator of the balance of flow and oxygen consumption. These compounds may provide a means of identifying dysfunctional chronically ischemic but viable "hibernating" myocardium and find a critical place in the assessment of angiogenesis. Nitroimidazole compounds hold promise for positive imaging of hypoxia in the heart. However, refinement of these compounds is needed to improve target specificity. The potential of technetium-99m (Tc99m) complexes derived from removal of the nitroimidazole moiety from a nitroimidazole-containing ligand is interesting and warrants further investigation. Experimental studies support the possibility of identifying myocardial hypoxia with the positron-emitting compound F18-fluoromisonidazole noninvasively. The potential of a Tc99m labeled nitroimidazole for positive imaging of myocardial ischemia is tremendous because single-photon imaging is more widely available. The true clinical potential of these nitroimidazole compounds can only be defined with future experimental and clinical studies. Ideally, these studies should include comparisons of tracer uptake with independent measures of regional ischemia or measures of oxygen tension, potentially using magnetic resonance imaging.

epsilon-sarcoglycan replaces alpha-sarcoglycan in smooth muscle to form a unique dystrophin-glycoprotein complex

The sarcoglycan complex has been well characterized in striated muscle, and defects in its components are associated with muscular dystrophy and cardiomyopathy. Here, we have characterized the smooth muscle sarcoglycan complex. By examination of embryonic muscle lineages and biochemical fractionation studies, we demonstrated that epsilon-sarcoglycan is an integral component of the smooth muscle sarcoglycan complex along with beta- and delta-sarcoglycan. Analysis of genetically defined animal models for muscular dystrophy supported this conclusion. The delta-sarcoglycan-deficient cardiomyopathic hamster and mice deficient in both dystrophin and utrophin showed loss of the smooth muscle sarcoglycan complex, whereas the complex was unaffected in alpha-sarcoglycan null mice in agreement with the finding that alpha-sarcoglycan is not expressed in smooth muscle cells. In the cardiomyopathic hamster, the smooth muscle sarcoglycan complex, containing epsilon-sarcoglycan, was fully restored following intramuscular injection of recombinant delta-sarcoglycan adenovirus. Together, these results demonstrate a tissue-dependent variation in the sarcoglycan complex and show that epsilon-sarcoglycan replaces alpha-sarcoglycan as an integral component of the smooth muscle dystrophin-glycoprotein complex. Our results also suggest a molecular basis for possible differential smooth muscle dysfunction in sarcoglycan-deficient patients.

Disruption of the sarcoglycan-sarcospan complex in vascular smooth muscle: a novel mechanism for cardiomyopathy and muscular dystrophy

To investigate mechanisms in the pathogenesis of cardiomyopathy associated with mutations of the dystrophin-glycoprotein complex, we analyzed genetically engineered mice deficient for either alpha-sarcoglycan (Sgca) or delta-sarcoglycan (Sgcd). We found that only Sgcd null mice developed cardiomyopathy with focal areas of necrosis as the histological hallmark in cardiac and skeletal muscle. Absence of the sarcoglycan-sarcospan (SG-SSPN) complex in skeletal and cardiac membranes was observed in both animal models. Loss of vascular smooth muscle SG-SSPN complex was only detected in Sgcd null mice and associated with irregularities of the coronary vasculature. Administration of a vascular smooth muscle relaxant prevented onset of myocardial necrosis. Our data indicate that disruption of the SG-SSPN complex in vascular smooth muscle perturbs vascular function, which initiates cardiomyopathy and exacerbates muscular dystrophy.

Potential role of the microvasculature in progression of heart failure

After cardiac injury, there are changes in the cardiac myocyte morphology, function, matrix, and molecular gene expression. These all play an important role in remodeling of the injured heart, contributing to the progression toward heart failure. The role of the microvasculature in the progression toward heart failure is less well characterized. However, laboratory studies have established that there are important interactions between the microvascular endothelium and the myocyte. Furthermore, in a multitude of animal models of heart failure and cardiomyopathy, there is always an association with microvascular abnormalities. Reversal of these abnormalities is also associated with improvement in the cardiomyopathy. Major mediators that likely play an important role in the microvasculature include endothelin and nitric oxide. These are elaborated by both endothelium and myocyte compartments of the myocardium. Preliminary clinical studies already demonstrate that microvascular ischemia may have prognostic power in patients with nonischemic dilated cardiomyopathy. Results from these studies showed a reduction in mortality from treatment with amlodipine, suggesting a possible benefit based on changes in the microvasculature.

Effect of prolonged treatment with amlodipine on enhanced vascular contractility in cardiomyopathic hamsters

This study examined the effects of prolonged treatment with amlodipine on the enhanced vascular contractions in dilated cardiomyopathic (CM) hamsters. From the ages of 5 to 20 weeks, CM hamsters (BIO 53.58) orally received amlodipine. Then we compared the contractile responses to vasoconstrictors in aortas and mesenteric arteries from CM hamsters with or without treatment with those in the arteries from controls (F1b). We also investigated the effect of amlodipine treatment on the Ca2+ sensitivity of tension in beta-escin-skinned smooth muscle of mesenteric artery. The contractile responses to phenylephrine, angiotensin II, and high K+ in both aorta and mesenteric artery were greatly enhanced in CM hamsters compared with controls. Amlodipine treatment slightly but significantly inhibited the enhanced responses in aorta but did not alter the responses in mesenteric arteries. The Ca2+ sensitivity of tension was significantly increased in CM hamster preparations, which was unaffected by amlodipine treatment. These data indicate that amlodipine treatment differentially affects the enhanced responses to vasoconstrictors between large and small blood vessels from CM hamsters. The lack of effect of amlodipine treatment on the responsiveness of CM mesenteric artery leads to the suggestion that the preventive effect of amlodipine on focal myocytolytic necrosis of cardiomyocytes, which was previously reported to be the main cause of cardiomyopathy, results from an action on cardiomyocytes.

MCI-154, a Ca2+ sensitizer, increases survival in cardiomyopathic hamsters

To assess the long-term efficacy of a Ca2+ sensitizer MCI-154, 6-[4-(4'-pyridylamino)phenyl]-4,5-dihydro-3(2H)-pyridazinone hydrochloride trihydrate, on chronic heart failure, we studied the effects of the agent on the life span of cardiomyopathic hamsters of the BIO-14.6 strain. At approximately 150 days of age, 210 male hamsters were randomly divided into three groups: MCI-154 0.1 mg kg(-1), day(-1)(MCI-154-low), MCI-154 1 mg kg(-1) day(-1) (MCI-154-high), and control group. The median survival time in control, MCI-154-low and MCI-154-high groups was 227, 243 and 260 days after the start of treatment, respectively. Final survival rate at 284 days in control, MCI-154-low and MCI-154-high groups was 0, 17.1 and 38.6%, respectively. The cumulative survival times in the two MCI-154 treated groups were significantly prolonged in comparison with that in the control group (P < 0.0001). Thus, the present study clearly showed that MCI-154 prolonged the life span of cardiomyopathic hamsters, suggesting that long-term therapy with MCI-154 would be promising in the treatment of congestive heart failure.

Beneficial effect of myocardial angiogenesis on cardiac remodeling process by amlodipine and MCI-154

The present study examined the effect of long-term treatment with amlodipine and MCI-154 (a Ca2+ sensitizer) on progressive cardiac dysfunction and microvasculature in the dilated cardiomyopathic (DCM) hamster heart. After treatment of DCM hamsters (Bio 53.58) with amlodipine or MCI-154 for 15 wk from the age of 5 wk, amlodipine and MCI-154 were found to cause an increase in left ventricular percent fractional shortening and decreases in left ventricular diastolic dimension and isovolumic relaxation time in echocardiograms (P < 0.01). A hemodynamic study showed that the diastolic time constant decreased in the amlodipine-treatment group (P < 0.05). In a morphometric study employing a double-staining method that discriminated arteriolar and venular capillaries, amlodipine and MCI-154 caused increases in total capillary density (P < 0.05) and the proportion of venular capillaries (P < 0.05). Moreover, Northern blot analysis showed that the expression of mRNA for vascular endothelial growth factor was significantly increased by amlodipine and MCI-154. They preserve coronary microvasculature in the DCM hamster and might induce angiogenesis of small vessels, thereby contributing to preservation of cardiac systolic and diastolic function.

Acute hemodynamic and coronary circulatory effects of experimental autoimmune myocarditis

Myocarditis and progression to cardiomyopathy is associated with focal spasm and reperfusion of the coronary microcirculation. Experimental autoimmune myocarditis (EAM), induced with cardiomyosin peptide-specific T cells in Lewis rats, was hypothesized to cause acute hemodynamic and coronary vasculature changes. Fifteen experimental animals (5 each at 1, 2, and 3 weeks after T-cell injection) and eight controls were studied using the constant pressure variant of the isolated heart. Coronary resistant decreased while coronary flow increased (P < 0.05) in EAM hearts after the first week. Rate-pressure product, +dP/dt and -dP/dt, decreased while the heart/body weight ratio increased (P < 0.05) compared with controls at 1 week but not at 2 or 3 weeks. Mean local myocardial PO2, which reflects local oxygen delivery and consumption, and MVO2 were not different for EAM hearts. However, compared with controls EAM myocardial PO2 varied more widely and was often beyond the usual range, suggesting the occurrence of localized hypoxic and hyperoxic areas. In summary, after the first week there was a significant decrease in coronary resistance in the EAM animals, which required higher flow to maintain a similar perfusion pressure. These changes in coronary resistance and flow along with the heterogeneity and extremes of local myocardial PO2 levels without a significant change in MVO2 may be explained by postulating development of low-resistance, high-flow hyperoxic areas which steal flow, thus causing hypoxia in other areas.

Effects of diltiazem on myocardial perfusion abnormalities during exercise in patients with hypertrophic cardiomyopathy

The effect of diltiazem on myocardial ischemia in patients with hypertrophic cardiomyopathy (HCM) was evaluated by exercise myocardial 201Tl single photon emission computed tomography (SPECT). Exercise myocardial SPECT was performed before and 8 weeks after oral administration of diltiazem (180 mg/day) in 20 patients with HCM who showed transient perfusion defects on exercise myocardial 201Tl SPECT under control conditions. SPECT images were divided into 17 segments. The 201Tl perfusion defects were visually scored and evaluated as the defect score. The transient dilation index was calculated as an index of subendocardial ischemia. Improvement of the defect score was demonstrated in 15 patients after the administration of diltiazem. The mean defect score decreased significantly from 9.90 +/- 5.17 to 5.50 +/- 4.89 (p < 0.0001). Although 16 of 20 patients showed an abnormal transient dilation index before diltiazem treatment, 16 showed improvement and 13 of these normalized after diltiazem therapy. The mean transient dilation index decreased from 1.16 +/- 0.10 to 1.02 +/- 0.09 (p < 0.0001). In conclusion, diltiazem prevents or diminishes myocardial ischemia in patients with HCM.

A serine elastase inhibitor reduces inflammation and fibrosis and preserves cardiac function after experimentally-induced murine myocarditis

In viral myocarditis, inflammation and destruction of cardiac myocytes leads to fibrosis, causing progressive impairment in cardiac function. Here we show the etiologic importance of serine elastase activity in the pathophysiology of acute viral myocarditis and the therapeutic efficacy of an elastase inhibitor. In DBA/2 mice inoculated with the encephalomyocarditis virus, a more than 150% increase in myocardial serine elastase activity is observed. This is suppressed by a selective serine elastase inhibitor, ZD0892, which is biologically effective after oral administration. Mice treated with this compound had little evidence of microvascular constriction and obstruction associated with myocarditis-induced ischemia reperfusion injury, much less inflammation and necrosis, only mild fibrosis and myocardial collagen deposition, and normal ventricular function, compared with the infected nontreated group.

Combined assessment of myocardial perfusion and left ventricular function with exercise technetium-99m sestamibi gated single-photon emission computed tomography can differentiate between ischemic and nonischemic dilated cardiomyopathy

The purpose of this study was to determine whether exercise technetium-99m sestamibi gated single-photon emission computed tomography (SPECT) accurately distinguishes between patients with ischemic cardiomyopathy and patients with nonischemic left ventricular systolic dysfunction. Noninvasive tests have previously failed to accurately separate patients with ischemic cardiomyopathy from those with nonischemic cardiomyopathy. Technetium-99m gated SPECT imaging offers advantages that have the potential to overcome the limitations of previous studies. Thirty-seven adults with a left ventricular ejection fraction < or = 35%, including 24 patients with nonischemic cardiomyopathy and 13 patients with ischemic cardiomyopathy, were prospectively evaluated using symptom-limited metabolic exercise treadmill testing with technetium-99m sestamibi gated SPECT imaging. Interpretation of myocardial perfusion and regional wall motion was performed, using a 17-segment model. Summed stress, rest, and reversibility perfusion defect scores were determined, and the variance of segmental wall motion scores was computed. Summed stress, rest, and reversibility perfusion defect scores were significantly lower in nonischemic cardiomyopathy patients, compared with those with ischemic cardiomyopathy (summed stress defect score: 6.9 +/- 3.8 vs 32.9 +/- 7.7, respectively, p <0.001). Variability in segmental wall motion was also significantly lower in patients with nonischemic cardiomyopathy compared with those with ischemic cardiomyopathy (variance: 0.3 +/- 0.3 vs 1.2 +/- 0.8, respectively, p <0.001). Thus, assessment of myocardial perfusion and regional ventricular function with exercise technetium-99m sestamibi gated SPECT imaging can reliably distinguish between patients with ischemic cardiomyopathy and patients with nonischemic dilated cardiomyopathy.

Oxidative stress and the pathogenesis of heart failure

There is strong evidence for an adverse role of oxidative stress in CHF in both animals and humans. Antioxidant supplement have been very effective in the treatment of animal paradigms; however, the data for the possible benefits of treatment for patients with CHF is either retrospective or inferential. Such information is important and should be the subject of prospective randomized trials.

Capillary density and leukocyte adhesion in hamsters with hereditary cardiomyopathy

The aim of this study was to characterize microvascular networks in cheek pouch of cardiomyopathic Syrian hamster (CM) (Bio 14.6), which is an interesting model of idiopathic cardiomyopathy and congestive heart failure. Microcirculation was visualized by fluorescence microscopy. Diameter and length of arterioles, classified according to centrifugal ordering scheme, were measured. A computational method was arranged to determine the density of arterioles and capillaries (total vessel length per unit area, cm-1), fractal dimension of capillaries, and the associated Voronoi tesselation. Furthermore, leukocyte adhesion to venules and arteriolar reactivity to drugs were studied. Increase in the number of terminal arterioles and capillary rarefication characterized CM microvasculature compared with that of age-matched controls (58 +/- 7 versus 25 +/- 5 cm-1, and 128 +/- 15 versus 240 +/- 10 cm-1, respectively). Fractal dimension of capillaries was reduced in CM compared with controls (1. 40 +/- 0.10 versus 1.85 +/- 0.09) and associated with increased avascular spaces, as shown by Voronoi tesselation results. Leukocyte adhesion to venules increased significantly in CM. In CM responsiveness of arterioles to nitric oxide inhibition and propranolol was slighter but more marked to norepinephrine and angiotensin II compared with that of control hamsters. In conclusion, the different geometry, increased leukocyte adhesion, and altered arterial responsiveness may contribute to flow disturbances in the microcirculation of CM hamsters.

Chronic effects of enalapril and amlodipine on cardiac remodeling in cardiomyopathic hamster hearts

This study examined the effects of long-term treatments with the angiotensin-converting enzyme inhibitor, enalapril, and the calcium antagonist, amlodipine, on the morphologic changes, progressive left ventricular dysfunction, and gene expression of the ryanodine receptor (RyR) and phospholamban (PLN) in dilated cardiomyopathy. From the ages of 5 through 20 weeks, dilated cardiomyopathic hamsters, BIO53.58 (BIO), and control hamsters, F1b, orally received either enalapril or amlodipine. Cardiac function was assessed by echocardiography. At the age of 20 weeks, the collagen volume fractions were analyzed by the stereologic method. RyR and PLN messenger RNAs (mRNAs) were examined by Northern blot in the amlodipine group. In BIO, the reduction of left ventricular percentage of fractional shortening was attenuated in the enalapril group (p < 0.05) and amlodipine group (p < 0.001), and the increase in the collagen volume fraction and the loss of myocytes were suppressed in the amlodipine group compared with the untreated group. RyR mRNA level decreased in BIO (p < 0.01) compared with F1b, but PLN mRNA level was unchanged. RyR and PLN mRNA levels were unaffected by the treatment with amlodipine. Enalapril and amlodipine prevent progressive remodeling and reduce cardiac dysfunction in BIO. Amlodipine prevents fibrosis and cell death without modifying RyR and PLN mRNA levels in BIO.

A role of myofilament Ca2+ sensitivity in enhanced vascular reactivity in cardiomyopathic hamsters

We compared the contractile responses to vasoconstrictors in aortas from 20- to 22-week old cardiomyopathic hamsters, BIO 53.58 strain, and age-matched F1b strain controls. Aortas from cardiomyopathic hamsters exhibited greater contractions in response to phenylephrine, angiotensin II, and high K+ than did the controls. Neither endothelium removal nor the presence of indomethacin and N(omega)-nitro-L-arginine (L-NNA) affected the enhanced contractile responses to these vasoconstrictors, indicating no involvement of endogenous prostanoids and nitric oxide from the endothelium. The contractile response to phorbol-12,13-dibutyrate (PDB) was also more markedly increased in cardiomyopathic aortas regardless of whether extracellular Ca2+ was present. The contractile response of cardiomyopathic aorta to phenylephrine was more sensitive to the inhibitory actions of the protein kinase C inhibitors staurosporine and calphostin C than was that of control aorta. These results suggest that activation of protein kinase C is partly involved in the enhanced phenylephrine response of cardiomyopathic aorta. None of nifedipine, ryanodine, and cyclopiazonic acid modified the maximum contractions induced by phenylephrine in either cardiomyopathic aortas or controls. The Ca2+ sensitivity of tension was significantly increased in beta-escin-skinned smooth muscle of mesenteric artery from cardiomyopathic hamsters compared to that of controls. PDB induced Ca2+ sensitization, but significantly only in cardiomyopathic hamsters. We propose that the enhanced vascular reactivity in cardiomyopathic hamsters may primarily result from increased Ca2+ sensitivity of contractile proteins. In addition, protein kinase C-mediated Ca2+ sensitization may further contribute to the enhanced vascular response to agonists.

Effects of phosphoramidon, BQ 788, and BQ 123 on coronary and cardiac dysfunctions of the failing hamster heart

Coronary dysfunctions identified in the presence of chronic heart failure are an important pathophysiologic abnormality that influences the prognosis of the disease. Because the endothelin pathway plays a significant role in the increased peripheral vascular tone associated with heart failure, we hypothesized that the endothelin pathway may be involved in the abnormal coronary vasomotion associated with this pathologic condition. Experiments were carried out in failing hearts (UM-X7.1 cardiomyopathic hamsters, aged 225-250 days) and normal hearts (Syrian LVG hamsters, also aged 225-250 days). Isolated hearts were perfused at constant flow and exposed to the blocker of the generation of endothelin-1 (ET-1), phosphoramidon (10 microM infusion), as well as to the selective ET(A)-receptor antagonist BQ 123 (10 microM infusion) and to a selective ET(B)-receptor antagonist BQ 788 (1 microM infusion). Coronary and cardiac effects of exogenous ET-1 (0.01-100 pmol) were also studied. Phosphoramidon, BQ 788, and BQ 123 did not altered coronary perfusion pressure either in normal or in failing hearts, whereas cardiac contractility was significantly impaired in the presence of phosphoramidon and BQ 123. Coronary sensitivity to exogenous ET-1 did not demonstrate a significant difference between normal and failing hearts [median effective concentration (EC50), 7 pmol in failing hearts vs. 12 pmol in normal hearts; p = NS]. In the presence of exogenous ET-1, cardiac contractility was significantly increased in both groups. In normal hearts, the exogenous ET-1-induced increase in coronary perfusion pressure was completely antagonized by BQ 123, whereas combined administration of BQ 788 and BQ 123 was necessary to induce complete inhibition in failing hearts. The positive inotropic effect elicited by exogenous ET-1 (EC50) was completely abolished in the presence of BQ 123, whereas BQ 788 had no significant effect. Results indicate that the endothelin pathway does not play a significant role in the altered coronary vasomotion observed in this model of chronic heart failure. On the contrary, the endothelin pathway appears to participate in the maintenance of myocardial contractility. According to these observations, administration of an inhibitor of ET-1 synthesis, as well as the use of an ET(A)-receptor antagonist, may be contraindicated in the presence of poor left ventricular function because the endothelin pathway contributes significantly to the maintenance of cardiac contractility.

Coronary endothelial dysfunction in patients with acute-onset idiopathic dilated cardiomyopathy

OBJECTIVES

This study sought to determine whether coronary endothelial dysfunction exists in patients with acute-onset idiopathic dilated cardiomyopathy (DCM) and to explore its relation to recovery of left ventricular systolic function in this patient population.

BACKGROUND

Coronary endothelial dysfunction exists in chronic DCM, but its importance in the development and progression of ventricular dysfunction is not known. To address this issue we studied coronary endothelial function in patients with idiopathic DCM <6 months in duration and explored the relation between coronary endothelial function and subsequent changes in left ventricular ejection fraction (LVEF).

METHODS

Ten patients with acute-onset idiopathic DCM (duration of heart failure symptoms 2.0 +/- 0.4 months [mean +/- SEM]) and 11 control patients with normal left ventricular function underwent assessment of coronary endothelial function during intracoronary administration of the endothelium-dependent vasodilator acetylcholine and the endothelium-independent vasodilator adenosine. Coronary cross-sectional area (CSA) was determined by quantitative coronary angiography and coronary blood flow (CBF) by the product of coronary CSA and CBF velocity measured by an intracoronary Doppler catheter. Patients with DCM underwent assessment of left ventricular function before and several months after the study.

RESULTS

Acetylcholine infusion produced no change in coronary CSA in control patients but significant epicardial constriction in patients with DCM (-36 +/- 11%, p < 0.01). These changes were associated with increases in CBF in control patients (+118 +/- 49%, p < 0.01) but no change in patients with DCM. Infusion of adenosine produced increases in coronary caliber and blood flow in both groups. Follow-up assessment of left ventricular function was obtained in nine patients with DCM 7.0 +/- 1.7 months after initial study, at which time LVEF had improved by > or =0.10 in four patients. Multiple linear regression revealed a positive correlation between both the coronary CSA (r2 = 0.57, p < 0.05) and CBF (r2 = 0.68, p < 0.01) response to acetylcholine and the subsequent improvement in LVEF.

CONCLUSIONS

Coronary endothelial dysfunction exists at both the microvascular and the epicardial level in patients with acute-onset idiopathic DCM. The preservation of coronary endothelial function in this population is associated with subsequent improvement in left ventricular function.

Increased oxidative stress in patients with congestive heart failure

OBJECTIVES

We sought to study the markers of lipid peroxidation and defenses against oxidative stress in patients with varying degrees of heart failure.

BACKGROUND

Despite advances in other areas of cardiovascular disease, the morbidity and mortality from congestive heart failure (CHF) are increasing. Data mainly from animal models suggest that free radical injury may promote myocardial decompensation. However, there are no studies in humans correlating the severity of heart failure with increased free radical injury and antioxidants.

METHODS

Fifty-eight patients with CHF and 19 control subjects were studied. In addition to complete clinical and echocardiographic evaluations, the prognosis of these patients was established by measuring the levels of soluble tumor necrosis factor-alpha receptors 1 and 2 (sTNF-R1 and sTNF-R2). Oxidative stress was evaluated by measuring plasma lipid peroxides (LPO), malondialdehyde (MDA), glutathione peroxidase (GSHPx) and vitamin E and C levels.

RESULTS

The patients' age range, cause of heart failure and drug intake were comparable across the different classes of heart failure. Heart failure resulted in a significant increase in LPO (p < 0.005), MDA (p < 0.005), sTNF-R1 (p < 0.005) and sTNF-R2 (p < 0.005). There was a significant positive correlation between the clinical class of heart failure and LPO, MDA, sTNF-R1 and sTNF-R2 levels. There was an inverse correlation between GSHPx and LPO. With increased lipid peroxidation in patients with CHF, the levels of vitamin C decreased, but vitamin E levels were maintained.

CONCLUSIONS

These data demonstrate a progressive increase in free radical injury and encroachment on antioxidant reserves with the evolution of heart failure; they also suggest that oxidative stress may be an important determinant of prognosis. The therapeutic benefit of administering antioxidant supplements to patients with CHF should be evaluated.

Innovative drug treatments for viral and autoimmune myocarditis

Myocarditis has been shown to be a common cause of cardiomyopathy and is believed to account for 25% of all cases in human beings. Unfortunately, the disease is difficult to detect before a myopathic process ensues. Treatment of myocarditis-induced heart failure includes the standard regimen of diuretics, digoxin, angiotensin-converting enzyme inhibitors, and currently, beta-adrenergic blockers. Treatment of myocarditis itself is dependent on the etiology of the illness. Treatments under investigation include immunosuppressants, nonsteroidal antiinflammatory agents, immunoglobulins, immunomodulation, antiadrenergics, calcium-channel blockers, angiotensin-converting enzyme inhibitors, nitric oxide inhibition (e.g., aminoguanidine), and antiviral agents. Despite advances in treatment, more work needs to be done in the early detection of myocarditis. Additionally, better means need to be established for distinguishing between viral and autoimmune forms of the disease, so that appropriate treatment can be instituted.

Safety of calcium antagonists in patients with congestive heart failure

Continuing high morbidity and mortality have spurred an ongoing search for new therapeutic agents for patients with congestive heart failure. Calcium antagonists (CAs) have been under active investigation in patients with heart failure since their introduction into clinical medicine, because their anti-ischemic and vasodilator properties were thought to be of potential benefit in this patient population. However, review of published clinical trials of CAs in patients with heart failure reveals that some of these drugs are associated with detrimental effects, including acute hemodynamic deterioration, increased symptoms of heart failure, and increased mortality. The adverse effects of short-acting CAs in patients with heart failure include negative inotropic effects and neurohormonal activation. Long-acting CAs, such as amlodipine and felodipine, had fewer negative inotropic effects, showed less evidence of neurohormonal activation, and were better tolerated in clinical trials. Amlodipine, in combination with an angiotensin-converting enzyme inhibitor, had a neutral effect in patients with ischemic heart failure and an unexplained benefit in a subgroup of patients with non-ischemic cardiomyopathy. Although the preliminary experience with long-acting dihydropyridine CAs in heart failure has been encouraging, safety concerns raised by past trials dictate that no CA can be recommended for the treatment of heart failure at this time.

Vitamin E and oxidative stress in the heart of the cardiomyopathic syrian hamster

Myocardial deterioration is relentlessly progressive in almost all patients who develop overt symptoms. Many dilated cardiomyopathies are associated with a marked increase in cardiac sympathetic tone which may be toxic to myocytes. Microvascular spasm, leading to diffuse, focal reperfusion injury, also appears to be an important mechanism of cardiomyocyte loss in many models of dilated cardiomyopathy. Free radicals may mediate both catecholamine-induced damage and reperfusion injury. We hypothesized that myocardial antioxidant reserve may be significantly reduced in dilated cardiomyopathy and that alpha-tocopheryl acetate may be of benefit. The enzymes superoxide dismutase, catalase and glutathione peroxidase were measured in the myocardial tissue of control and cardiomyopathic hamsters in early (25-50 days) and late (275-320 days) stages of the cardiomyopathy. In another study, myocardial glutathione peroxidase activity and protein oxidation was measured in control and late stage cardiomyopathic hamsters receiving alpha-tocopheryl (70 mg/kg/day) or vehicle for 1 month. There were no significant differences in glutathione peroxidase activity between control and cardiomyopathic hamsters in the early stage of the cardiomyopathy. Superoxide dismutase and catalase activities did not change with aging; however, glutathione peroxidase decreased over 30%, alpha-tocopherol was reduced by approximately 50% and protein oxidation increased more than 2-fold in the hearts of late stage cardiomyopathic hamsters. Alpha-tocopheryl acetate administration restored alpha-tocopherol levels, glutathione peroxidase activity and protein oxidation to normal. We conclude that the decompensating heart has significantly limited antioxidant reserve and that this reserve is sensitive to the intake of antioxidant supplements.

Altered vascular function in early stages of heart failure in hamsters

BACKGROUND

Congestive heart failure is a clinical condition associated with alterations in the normal balance of neurohumoral agents and factors acting on the vascular wall. The etiology of this condition, however, remains largely undefined. To help elucidate the pathophysiology of this disease, vascular function and angiotensin-converting enzyme activity were evaluated in 2-month-old Syrian cardiomyopathic hamsters (SCHs) that had not yet developed heart failure. Age-matched normal hamsters were used as control hamsters.

METHODS AND RESULTS

Vascular function studies included determinations of contractile responses of aortic rings to 0.1 microM angiotensin II and 0.1 microM norepinephrine. In addition, endothelial function was evaluated by the vasorelaxant action of acetylcholine on norepinephrine-precontracted aortic rings. The results indicate that the pressor effect of angiotensin II (0.1 microM) was 35% greater in aortic rings from SCRs than that observed in control animals. This effect is specific for angiotensin II because the contraction induced by NE (0.1 microM) was similar in both of these strains. Angiotensin-converting enzyme activity was three-fold higher in aorta homogenates from SCHs but normal in plasma and heart tissue when compared with control hamsters. Aortic ring preparations from SCHs also exhibited endothelial dysfunction because the maximal relaxation elicited by 10 microM acetylcholine was reduced 53%. Concentration-response curves with acetylcholine yielded EC50 values that were threefold lower in SCHs (97.2 +/- 0.1 nM) than in control animals (286 +/- 7 nM). Indomethacin (1 microM) increased the vasorelaxant effect of acetylcholine 28% in SCHs and shifted to the left the concentration-response curve of this agonist, suggesting an increased relaxation with the cyclooxygenase inhibitor. No effect of indomethacin on acetylcholine-induced relaxation was observed in control animals. Sodium nitroprusside induced similar relaxations in both control animals and SCHs, suggesting that the vascular smooth muscle response is normal in SCR.

CONCLUSIONS

Altogether these results point to a state of enhanced vascular contractility in young SCHs that could predispose these animals to develop heart failure, the enhanced vascular contractility could result from increased activity of the local renin-angiotensin system, augmented vascular response to angiotensin II, reduced nitric oxide synthesis, and enhanced production of prostaglandins.

Coronary constriction impairs cardiac function and induces myocardial damage and ventricular remodeling in mice

To establish whether coronary artery narrowing (CAN) in mice was accompanied by depressed ventricular function, tissue injury, and modifications in cardiac anatomy, the left coronary artery was constricted in FVB/N mice and the animals were killed 7 days later. CAN consisted of a 53% reduction in luminal diameter, which resulted in a twofold increase in left ventricular end-diastolic pressure. Left ventricular systolic pressure and left ventricular + and -dP/dt decreased 15, 21, and 11%, respectively. Left ventricular weight-to-body weight ratio increased 33%. This hypertrophic adaptation was characterized by a 9 and 20% increase in the longitudinal and transverse cavitary diameters, which provoked a 1.5-fold expansion in chamber volume. In contrast, wall thickness decreased 15%. These anatomic and functional changes induced a threefold elevation in diastolic stress. Foci of reparative fibrosis were found in the endomyocardium and epimyocardium, involving 2-3% of the tissue. Finally, myocyte loss in the ventricle was 15%, and myocyte hypertrophy was 38%. Impaired ventricular function, diastolic Laplace overloading, myocyte loss, and decompensated eccentric hypertrophy in mice after CAN mimic the ischemic cardiomyopathic heart in humans.

Contribution of hypoxia to the development of cardiomyopathy in hamsters

OBJECTIVE

It has been hypothesized that microvascular spasms cause cardiomyopathy. To elucidate the contribution of hypoxia to the development of cardiomyopathy, the newly-developed hypoxia tracer, Tc-99m nitroimidazole, was applied to detect myocardial hypoxia in a hamster model.

METHODS

Tc-99m nitroimidazole (180 MBq) and I-125 iodoantipyrine (370 kBq) were injected into cardiomyopathic Syrian hamsters or control hamsters at age 10, 25, and 40 weeks (n = 6 in each group). The myocardial uptake of Tc-99m nitroimidazole was measured and dual tracer autoradiography was performed.

RESULTS

Histologic study revealed that the cardiomyopathic hamsters at age 10, 25 and 40 weeks were in the myocytolytic stage, the fibrotic and healing stage, and the hypertrophy and dilatation stage, respectively. Tc-99m nitroimidazole uptake was significantly greater in the cardiomyopathic hamsters than in the controls at age 25 weeks (cardiomyopathic hamsters, 33.3 +/- 4.7% g dose/g; control, 25.2 +/- 3.1), whereas there were no significant differences between both strains at age 10 and 40 weeks. The quantified concentration of I-125 iodoantipyrine in the cardiomyopathic hamster at age 40 weeks was significantly lower than that in the controls. When the Tc-99m nitroimidazole uptake was normalized by I-125 iodoantipyrine concentrations, the cardiomyopathic hamsters at age 25 and 40 weeks showed significantly greater uptake than the controls.

CONCLUSION

The myocardium in cardiomyopathic hamsters was hypoxic at the fibrotic and healing stage and may be hypoxic at the hypertrophy and dilatation stage. This may contribute to the development of cardiomyopathy.

Inflammatory myocardial diseases and cardiomyopathies

Inflammatory myocardial disease has been associated with a variety of infectious and noninfectious etiologies. It is associated with the development of dilated cardiomyopathy in some patients. Given its imprecise diagnosis, varied clinical presentation and undefined natural history, it is quite difficult to make broad generalizations regarding its evaluation and treatment. It is hoped continued application of new molecular biological and other techniques will shed further light on the pathophysiologic mechanisms of myocarditis in humans, thus pointing to therapeutic interventions.

The role of stressor intensity and underlying vasculopathy in altering coronary reactivity in cardiomyopathic hamsters

OBJECTIVE

Our previous work showed that stress sensitized the vessels of cardiomyopathic hamsters (CMHs), but only hamsters in the lesion-forming period of their life. We hypothesized that we would find an interaction between stressor intensity and microvascular vulnerability.

METHOD

Male CMHs at ages of 1.5, 2.5, and 3.5 months were stressed with supine immobilization for five consecutive days. Stressor intensity was manipulated by immobilizing groups of CMHs at room temperature for 0 minutes, 15 minutes, 30 minutes, 1 hour, or 2 hours. CMHs were anesthetized and sacrificed 5 days after stress, and their hearts were perfused using a modified Langendorff system. Body weight changes and baseline coronary vascular resistance (CVR) were recorded, and CVR was also measured after coronary artery infusion of arginine vasopressin (AVP).

RESULTS

Stress produced no effect on coronary vasculature in 1.5-month-old CMHs. In 2.5-month-old CMHs, only the two highest-intensity stressors enhanced coronary reactivity to AVP. In 3.5-month-old CMHs, higher-intensity stressors produced a marginal AVP-induced increase in CVR; but this marginal increase was significantly lower than the increases seen with the two highest-stressor intensities in the 2.5-month-old CMHs.

CONCLUSION

The stress-induced coronary hyperreactivity to AVP seen in 2.5-month-old CMHs diminished when microvascular vulnerability was lower in 3.5-month-old CMHs. For 1.5-month-old CMHs, the resting CVR was extremely high, so that the addition of stress produced no further increase. Thus, stressor intensity interacted with microvascular vulnerability to alter the consequences of stress.

Prevention by cromakalim of spontaneously occurring cardiac necroses in polymyopathic hamsters

Previous studies on the heart necrotizing process at early stages of the hamster polymyopathy have led us to believe that this hereditary disease derives from a defective transmembrane ion flux resulting in myocardial Ca2+ over-load. On the other hand, certain K+ ATP channel openers were shown to prevent cytosolic Ca2+ accumulation in ischemic hearts. Therefore, we investigated the potential beneficial effect of chronic treatment with cromakalim (CR) on the development of necrotic changes in hamster myopathic hearts. Young cardiomyopathic (CM) hamsters were treated parenterally with CR over 4 consecutive weeks. The K+ ATP opener was dissolved in 5% DMSO and injected twice daily (s.c. and i.p. alternatively) at a dose level of 2.5 mg/kg per injection. Microscopic readings were carried out in staged serial paraffin sections of heart ventricles, the diaphragm, and tongue, will all tissues freshly taken at autopsy. In comparison with control untreated hearts, which exhibit numerous necrotic calcific foci, only minute myolytic lesions were found in 5 of 12 hamsters hearts receiving CR (p < 0.0001). Interestingly, the dystrophic process in the tongue was significantly less severe (p < 0.0004) in CR-treated animals. These observations provide evidence for the first time that in vivo sustained treatment with a K+ ATP opener exerts cardioprotection upon development of the hamster hereditary cardiomyopathy.

Modification of aortic contractility in the cardiomyopathic hamster

1. The functional arterial response in the cardiomyopathic hamster compared with inbred control, was investigated in thoracic aortae. For this purpose, vessels were cut into 6-mm rings and mounted in 20-ml organ baths. 2. In a first experimental series, the function of the endothelium was evaluated. Dose-response curves to acetylcholine (0.1 nM-10 microM) on phenylephrine (0.3 microM)-preconstricted rings of cardiomyopathic hamsters and inbred age-matched controls were comparable (log[EC50] of -7.08 +/- 0.12 and -7.18 +/- 0.12, respectively; n = 4). 3. Changes in contractility of cardiomyopathic hamster endothelium-denuded aortae were investigated. Dose-response curves to phenylephrine (1 nM-0.1 mM), angiotensin II (10 pM-0.3 microM), 5-hydroxytryptamine (5-HT) (1 nM-0.1 mM) and KCl (1 mM-0.1 M) were performed. Increased sensitivity in cardiomyopathic hamster aortae, compared to controls, was observed with phenylephrine (log[EC50] of -7.25 +/- 0.05 and -6.83 +/- 0.05, respectively, n = 6, P < 0.001) and angiotensin II (log[EC50] of -8.67 +/- 0.07 and -8.26 +/- 0.06, respectively, n = 6, P = 0.001) but not with 5-HT or KCl. A decreased maximum response in cardiomyopathic, compared to control, was observed with 5-HT (1.28 +/- 0.06 g vs 1.56 +/- 0.07 g, respectively, n = 6, P = 0.03). Comparable results were found in aortae with an intact endothelium. 4. No difference in the maximum contractile response to the G-protein activator, NaF (3, 10 and 30 mM) was observed in either group of animals. 5. Phorbol 12-myristate 13-acetate (PMA, 1-10 microM) was used to assess changes in the activity of protein kinase C (PKC). Contractility to PMA was increased in cardiomyopathic hamster aortae compared to controls (0.22 +/- 0.02 g vs 0.07 +/- 0.03 g at 3 microM, respectively, n = 6, P = 0.003). 6. Finally, cardiomyopathic hamsters aortae were found to be less sensitive when exposed to increasing concentrations of Ca2+ (10 microM-1 mM) in KCl-depolarized rings (0.58 +/- 0.04 g in cardiomyopathic vs 0.79 +/- 0.06 g in control aortae at 0.3 mM, n = 8, P = 0.03). 7. In conclusion, aortae from cardiomyopathic hamsters are more sensitive to phenylephrine and angiotensin II, but not to 5-HT, than those of controls. The increase in sensitivity does not implicate Ca2+ channels or Ca2+ itself since cardiomyopathic hamsters aortae are not more sensitive to KCl- and Ca(2+)-induced contraction. The greater effect of PMA on cardiomyopathic hamster aortae suggests that the increase in sensitivity to phenylephrine and angiotensin II involves an enhanced activity of PKC.

Myocardial alterations in diabetes and hypertension

Diabetes mellitus is a complex group of diseases that has hyperglycemia as a common metabolic abnormality. Although it is well-known that diabetic patients are susceptible to the effects of large vessel atherosclerosis with specific cardiac and cerebral complications, the association of diabetes mellitus with cardiac dysfunction caused by cardiomyopathy in the absence of significant coronary artery disease has been recognized for many years. However, the pathogenesis of diabetic cardiomyopathy remains unknown and has been somewhat controversial. Specifically, whether diabetes mellitus with its metabolic effects is sufficient to account for cardiomyopathy remains to be proven. This paper reviews the evidence for and against a metabolic etiology. In addition, we review the clinical and experimental evidence that supports the view that diabetes mellitus acts together with hypertension to produce structural damage in the heart that manifests as ventricular dysfunction and ultimately congestive heart failure. The concomitant effects of the metabolic derangements of diabetes and the vascular abnormalities associated with hypertension may lead to microvascular-induced tissue injury. Findings supporting this hypothesis are presented, along with observations suggesting that treatment with vasodilating calcium channel blockers or angiotensin converting enzyme inhibitors may be beneficial in regard to tissue pathology and mortality in experimental models. Recent clinical studies also support a role for the microcirculation in diabetics. Finally, it is suggested that if the microcirculation is pathogenetically involved in diabetic cardiomyopathy, then agents that improve microcirculatory flow along with tight control of hypertension may be as beneficial in the treatment or prevention of diabetic cardiomyopathy as strict metabolic control of hyperglycemia.

Altered coronary endothelial function in a patient with asymptomatic left ventricular dysfunction

Coronary endothelial dysfunction has been demonstrated in patients with symptomatic heart failure. Furthermore the endothelium has been implicated in the pathogensis of cardiomyopathy in patients with normal coronary angiograms and no other known causes of heart failure. Herein we describe an asymptomatic patient with an early cardiomyopathy and abnormal coronary endothelial function. There was no evidence for coronary disease by both angiography and intravascular ultrasound. Epicardial coronary artery vasoconstriction and a decrease in coronary blood flow was noted during the intracoronary infusion of graded concentrations of acetylcholine. This case demonstrates that endothelial dysfunction occurs in the setting of asymptomatic left ventricular dysfunction and highlights the potential importance of the endothelium in the early development of heart failure.