Comparison of exercise effects on the hemodynamics of the Bio 14.6 cardiomyopathic hamster.

1. Comparisons of the effects of 4 and 16 weeks of exercise were made on; cardiac output, stroke volume, heart rate, left intraventricular systolic and diastolic pressures, dP/dt, and heart calcium in the Bio 14.6 cardiomyopathic and F1 B hamsters. 2. In the cardiomyopathic hamster the cardiac output, stroke volume, left intraventricular systolic pressure and dP/dt, which were all depressed in the age related sedentary animals, were increased by both periods of exercise. The left intraventricular diastolic pressure which was elevated was likewise decreased by both exercise periods. Only the 16 week exercise period decreased the resting heart rate. 3. In the normal F1 B hamster, both periods of exercise increased the cardiac output and stroke volume while the left intraventricular systolic pressure was decreased. Only the 16 week exercise decreased the resting heart rate and left intraventricular diastolic pressure and increased the left ventricular dP/dt. 4. Both periods of exercise increased the total heart calcium in the Bio 14.6 hamster while the heart calcium in the F1 B was increased only by the 16 week exercise period.     

Left ventricular pressure-volume relationship in a rat model of advanced aging-associated heart failure

Aging is associated with profound changes in the structure and function of the heart. A fundamental understanding of these processes, using relevant animal models, is required for effective prevention and treatment of cardiovascular disease in the elderly. Here, we studied cardiac performance in 4- to 5-mo-old (young) and 24- to 26-mo-old (old) Fischer 344 male rats using the Millar pressure-volume (P-V) conductance catheter system. We evaluated systolic and diastolic function in vivo at different preloads, including preload recruitable stroke work (PRSW), maximal slope of the systolic pressure increment (+dP/dt), and its relation to end-diastolic volume (+dP/dt-EDV) as well as the time constant of left ventricular pressure decay, as an index of relaxation. The slope of the end-diastolic P-V relation (EDPVR), an index of left ventricular stiffness, was also calculated. Aging was associated with decrease in left ventricular systolic pressure, +dP/dt, maximal slope of the diastolic pressure decrement, +dP/dt-EDV, PRSW, ejection fraction, stroke volume, cardiac and stroke work indexes, and efficiency. In contrast, total peripheral resistance, left ventricular end-diastolic volume, left ventricular end-diastolic pressure, and EDPVR were greater in aging than in young animals. Taken together, these data suggest that advanced aging is characterized by decreased systolic performance accompanied by delayed relaxation and increased diastolic stiffness of the heart in male Fischer 344 rats. P-V analysis is a sensitive method to determine cardiac function in rats.     

Effects of dihydroergotamine on hemodynamic molsidomine actions in anesthetized dogs

In pentobarbital-anesthetized mongrel dogs the intravenous actions of 0.50 mg/kg molsidomine on pulmonary artery and left ventricular (LV) end-diastolic pressures and internal heart dimensions (preload), left ventricular systolic and peripheral blood pressures, and total peripheral resistance (afterload), as well as on heart rate, dP/dt, stroke volume, and cardiac output (heart performance) were studied for 2 h. Hemodynamic molsidomine effects were influenced by increasing amounts of intravenously infused dihydroergotamine solution (DHE, 1-64 micrograms X kg-1 X min-1). Molsidomine decreased preload, stroke volume, and cardiac output for over 2 h but decreased ventricular and peripheral pressures for 45 min. Systemic vascular resistance showed a tendency to decrease while heart rate and LV dP/dtmax were not altered. DHE infusion reversed molsidomine effects on the preload and afterload of the heart. The diminished stroke volume was elevated so that cardiac output also increased. Total peripheral resistance increased while heart rate fell in a dose-dependent fashion. The LV dP/dtmax remained unchanged until the highest dose of 64 micrograms X kg-1 X min-1 DHE elevated the isovolumic myocardial contractility. These experiments indicate that DHE can reverse the intravenous molsidomine effects on hemodynamics. Most likely, this is mediated through peripheral vasoconstriction of venous capacitance vessels, thereby affecting molsidomine's action on postcapillary beds of the circulation.     

Acidaemia reduces cardiac output and left ventricular contractility in conscious lambs

We studied the effects of HCI-induced metabolic acidaemia on cardiac output, contractile function, myocardial blood flow, and myocardial oxygen consumption in nine unanaesthetized newborn lambs. Through a left thoracotomy, catheters were placed in the aorta, left atrium and coronary sinus. A pressure transducer was placed in the left ventricle. Three to four days after surgery, we measured cardiac output, dP/dt, left ventricular end diastolic and aortic mean blood pressures, heart rate, aortic and coronary sinus blood oxygen contents, and left ventricular myocardial blood flow during a control period, during metabolic acidaemia, and after the aortic pH was restored to normal. We calculated systemic vascular resistance, myocardial oxygen consumption and left ventricular work. Acidaemia was associated with reduction in cardiac output, maximal dP/dt, and aortic mean blood pressure. Left ventricular end diastolic pressure and systemic vascular resistance increased, and heart rate did not change significantly. The reduction in myocardial blood flow and oxygen consumption was accompanied by fall in cardiac work. Cardiac output returned to control levels after the pH had been normalized but maximal dP/dt was incompletely restored. Myocardial blood flow and oxygen consumption increased beyond control levels. This study demonstrates that HCI-induced metabolic acidaemia in conscious newborn lambs is associated with a reduction in cardiac output which could have been mediated by the reduction in contractile function and/or the increase in systemic vascular resistance. The decreases in myocardial blood flow and oxygen consumption appear to reflect diminished cardiac work. The restoration of a normal cardiac output after normalization of the pH appears to have resulted from the increases in heart rate and left ventricular filling pressures in conjunction with an incomplete restoration of contractile function.     

Divergent changes in the rate of development of pressure in the left ventricle and in the performance of the heart as a pump.

Dog hearts were prepared in situ so that heart rate (HR), left ventricular end diastolic pressure (LVEDP) and mean aortic pressure (MAP) could be controlled separately during computation of left ventricular dP/dt max and external stroke work (SW). Progressive increases in HR consistently raised dP/dt max over a wide range, and consistently lowered SW except at low rates. Progressive increases in LVEDP or MAP consistently raised both dP/dt max and SW. Infusion of noradrenaline consistently raided both dP/dt max and SW, except at very high HR when only dP/dt max was consistently raised. Our results lead us to question the validity of equating changes in pre-ejection measurements with changes in performance of the heart as a pump under abnormal conditions and in the assessment of inotropic agents.     

Correlation of changes in cardiac calcium channels with hemodynamics in Syrian hamster cardiomyopathy and heart failure

We compared hemodynamics with [3H]nitrendipine (calcium channel) binding to cardiac membranes from Bio 14.6 cardiomyopathic Syrian hamsters at 4 and 10 months with their F1B controls. A 50% increase in the number (Bmax) of nitrendipine binding sites (calcium channels) was seen only in the 4 month old myopathic vs controls (Bmax = 468 +/- 11 vs 309 +/- 10 fmol/mg prot with no change in affinity (KD) (KD = .65 +/- .12 vs .75 +/- .14 nM), while no differences in Bmax or KD were seen at 10 months (Bmax = 375 +/- 9 vs 362 +/- 7 fmol/mg prot/KD = .82 +/- .18 vs .89 +/- .17 nM) myopathic vs control respectively. Hemodynamic studies revealed no significant differences in cardiac output, cardiac index, stroke volume, heart rate, mean arterial pressure, peripheral resistance, body weight, heart weight at 4 months, but a significant decrease in peripheral resistance (1120 +/- 360 vs 2080 +/- 240) increase in body weight (118 +/- 2 vs 94 +/- 2 grams) and heart weight (97 +/- 5 vs 78 +/- 2 gms/100 gms body weight) in 10 month myopathic vs control animals. We conclude that the onset of cardiomyopathy at 4 months is associated with a selective increase in calcium channel binding sites and heart failure at 10 months is associated with a relative decrease in these sites.     

Gender differences in the cardiac response to dietary conjugated linoleic acid isomers

The present study was undertaken to assess the heart function, by the in vivo catheterization technique, of healthy male and female Sprague-Dawley rats fed different conjugated linoleic acid (CLA) isomers, (cis-9, trans-11 (c9,t11) and trans-10, cis-12 (t10,c12)) individually and in combination (50:50 mix as triglyceride or fatty acids) from 4 to 20 weeks of age. Whereas the triglyceride form of the CLA isomer mix lowered the heart rate, the rate of contraction (+dP/dt) and rate of relaxation (-dP/dt), systolic and diastolic pressures, mean arterial pressure, and the left ventricular systolic pressure were higher in male rats as compared with all the other dietary groups. In contrast, there were no significant effects in the cardiac function of the female rats in response to the CLA isomer mix in triglyceride form. Whereas the heart rate, +dP/dt, and left ventricular systolic pressure were lower in male rats fed the t10,c12 CLA isomer alone, the heart rate of the female rats was higher, but the systolic pressure, +dP/dt, and mean arterial pressure were lower compared with the control group. Also, the left ventricular end-diastolic pressure was specifically higher in the female rats in response to free fatty acids-containing CLA mix. Furthermore, an additive effect of the free fatty acids-containing CLA mix was seen in the +dP/dt and -dP/dt of female rats compared with the control group. These results indicate that CLA isomers exert differential effects on heart function and suggest the need for a complete evaluation of the benefits, interactions, and potential side effects of each isomer.     

Haemodynamic effects of respiratory alkalosis independent of changes in airway pressure in anaesthetized newborn dogs

We have recently reported a decrease in cardiac output in newborn dogs during respiratory alkalosis which is independent of changes in airway pressure. The present study was designed to characterize the mechanism responsible for this reduction in cardiac output. Twelve newborn coonhounds were anaesthetized with pentobarbital, paralyzed with pancuronium and hyperventilated to an arterial carbon dioxide tension (PaCO2) of 20 torr. Subsequent changes in PaCO2 were achieved by altering the FiCO2. Measurements were made after 30 min at either 40 or 20 torr PaCO2. The sequence of PaCO2 levels was randomized. Compared to normocarbia, respiratory alkalosis resulted in significantly decreased cardiac output (279 +/- 16 to 222 +/- 10 ml/min per kg, mean +/- SEM, P less than 0.001), stroke volume (1.60 +/- 0.10 to 1.24 +/- 0.06 ml/kg; P less than 0.001), maximum left ventricular dP/dt (1629 +/- 108 to 1406 +/- 79 mmHg/s, P less than 0.01) and left ventricular end diastolic pressure (3.9 +/- 0.4 to 2.9 +/- 0.3 mmHg; P less than 0.001). The decrease in cardiac output during respiratory alkalosis is manifest through a decrease in stroke volume, which is due, at least in part, to the decrease in left ventricular end diastolic pressure. The decrease in maximum left ventricular dP/dt is likely a reflection of the decrease in preload, however, a change in myocardial contractility cannot be excluded. We speculate the decrease in filling pressure may be due to an increase in venous capacitance.     

Disruption of protein kinase A interaction with A-kinase-anchoring proteins in the heart in vivo: effects on cardiac contractility, protein kinase A phosphorylation, and troponin I proteolysis

Protein kinase A (PKA)-dependent phosphorylation is regulated by targeting of PKA to its substrate as a result of binding of regulatory subunit, R, to A-kinase-anchoring proteins (AKAPs). We investigated the effects of disrupting PKA targeting to AKAPs in the heart by expressing the 24-amino acid regulatory subunit RII-binding peptide, Ht31, its inactive analog, Ht31P, or enhanced green fluorescent protein by adenoviral gene transfer into rat hearts in vivo. Ht31 expression resulted in loss of the striated staining pattern of type II PKA (RII), indicating loss of PKA from binding sites on endogenous AKAPs. In the absence of isoproterenol stimulation, Ht31-expressing hearts had decreased +dP/dtmax and -dP/dtmin but no change in left ventricular ejection fraction or stroke volume and decreased end diastolic pressure versus controls. This suggests that cardiac output is unchanged despite decreased +dP/dt and -dP/dt. There was also no difference in PKA phosphorylation of cardiac troponin I (cTnI), phospholamban, or ryanodine receptor (RyR2). Upon isoproterenol infusion, +dP/dtmax and -dP/dtmin did not differ between Ht31 hearts and controls. At higher doses of isoproterenol, left ventricular ejection fraction and stroke volume increased versus isoproterenol-stimulated controls. This occurred in the context of decreased PKA phosphorylation of cTnI, RyR2, and phospholamban versus controls. We previously showed that expression of N-terminal-cleaved cTnI (cTnI-ND) in transgenic mice improves cardiac function. Increased cTnI N-terminal truncation was also observed in Ht31-expressing hearts versus controls. Increased cTnI-ND may help compensate for reduced PKA phosphorylation as occurs in heart failure.     

The effect of changes in cardiac frequency on left and right ventricular dP/dt max at different contractile states of the myocardium

In 17 canine heart-lung preparations the dependence of frequency potentiation of the right and left ventricular myocardium on the basic inotropic state of the heart was investigated. The effect of unipolar stimulation of the right atrium on dP/dt max in both ventricles was measured. The aortic pressure was maintained constant. Shortly after isolation of the heart, a stepwise increase of rate from 140 to 200 beats/min only had a very weak influence on left ventricular dP/dt max. With deterioration of the myocardium the frequency potentiation of dP/dt max increased considerably. End-diastolic pressure regularly decreased with rising cardiac frequency. Since the real positive inotropic effect is masked by the concomitant fall in diastolic loading, the end-diastolic pressure was maintained constant in a second group of 8 hearts during rate variation. The most pronounced inotropic effect was now found shortly after isolation of the heart. A rate increase of 30 beats/min resulted in a 20% rise of dP/dt max. The frequency potentiation decreased with deterioration of the heart resulting in a 12% dP/dt max increase at an estimated inotropic state of 50% of control. When the contractile state of the heart was improved above the control state by calcium application the frequency potentiation of the myocardium decreased. In the right ventricle similar results were obtained except for the fact that no significant correlation between the steepness of the frequency characteristics and the contractile state of the heart could be found when the end-diastolic pressure was kept constant.     

Participation of the autonomic nervous system in the cardiovascular effects of milrinone

The cardiodynamic activity of intravenously administered milrinone was examined in alpha-chloralose anesthetized dogs. Two groups of dogs were used, one pretreated with hexamethonium to block autonomic reflexes, and a second group which received no pretreatment. In the untreated group milrinone produced dose-dependent increases in +dP/dt and heart rate while decreasing both systolic and diastolic blood pressure and left ventricular end diastolic pressure (LVEDP). After treatment with hexamethonium basal heart rate was significantly increased, whereas reflex changes in heart rate in response to i.v. norepinephrine or nitroglycerin were ablated. Systolic, but not diastolic blood pressure was also markedly reduced by hexamethonium. In the presence of hexamethonium responses to milrinone were qualitatively similar to milrinone responses in the absence of hexamethonium. However, the dose-response curves for milrinone were shifted dextrally for changes in +dP/dt and LVEDP, whereas the dose-response curve for blood pressure was shifted sinistrally. Thus, it appears that the autonomic nervous system enhances the effect of milrinone on +dP/dt and LVEDP, but attenuates its effect on blood pressure.     

Exhaustion of the Frank-Starling mechanism in conscious dogs with heart failure induced by chronic coronary microembolization

The role of the Frank-Starling mechanism in the regulation of cardiac systolic function in the ischemic failing heart was examined in conscious dogs. Left ventricular (LV) dimension, pressure and systolic function were assessed using surgically implanted instrumentations and non-invasive echocardiogram. Heart failure was induced by daily intra-coronary injections of microspheres for 3-4 weeks via implanted coronary catheters. Chronic coronary embolization resulted in a progressive dilation of the left ventricle (12+/-3%), increase in LV end-diastolic pressure (118+/-19%), depression of LV dP/dt(max) (-19+/-4%), fractional shortening (-36+/-7%), and cardiac work (-60+/-9%), and development of heart failure, while the LV contractile response to dobutamine was depressed. A brief inferior vena caval occlusion in dogs with heart failure decreased LV preload to match the levels attained in their control state and caused a further reduction of LV dP/dt(max), fractional shortening, stroke work and cardiac work. Moreover, in response to acute volume loading, the change in the LV end-diastolic dimension-pressure (DeltaLVEDD-DeltaLVEDP) curve in the failing heart became steeper and shifted significantly to the left, while the increases in LV stroke work and cardiac work were blunted. Thus, our results suggest that the Frank-Starling mechanism is exhausted in heart failure and unable to further respond to increasing volume while it plays an important compensatory role in adaptation to LV dysfunction in heart failure.     

Effects of intra-coronary administration of leukotriene D4 in the anaesthetized dog

The left anterior descending coronary artery in anaesthetized greyhounds was perfused at constant pressure with blood pumped from the carotid artery. Phasic and mean coronary flow, left ventricular pressure, dP/dt, cardiac output, ECG, heart rate and systemic pressure were measured. Leukotriene (LT) D₄ was administered into the left anterior descending coronary artery as a bolus injection. LTD₄ caused dose-related reductions in coronary flow. Other parameters showed little immediate change although a gradual decrease in left ventricular pressure, dP/dt, cardiac output and systemic pressure occurred after administration of LTD₄. Following intracoronary administration of LTD₄ small surface haemorrhages were observed over the area perfused. The reduction in coronary flow was not inhibited by indomethacin.     

Effects of naloxone on systemic and regional hemodynamic responses to exercise in dogs

To determine whether endogenous opiates have a role in circulatory regulation during mild to moderate exercise, 11 chronically instrumented dogs were exercised on a treadmill up a 6% incline at 2.5 and 5.0 mph, each for 20 min, after treatment with either the opiate receptor antagonist naloxone (1 mg/kg bolus and 20 micrograms.kg-1.min-1 infusion) or normal saline. Naloxone increased plasma beta-endorphin and adrenocorticotropic hormone at rest but had no effect on resting heart rate, aortic pressure, cardiac output, left ventricular time derivative of pressure (dP/dt) and ratio of dP/dt at a developed pressure of 50 mmHg and the developed pressure (dP/dt/P), or plasma catecholamines. Plasma beta-endorphin and adrenocorticotropic hormone increased during exercise. In addition, graded treadmill exercise produced proportional increases in heart rate, cardiac output, aortic pressure, left ventricular dP/dt and dP/dt/P, and blood flow to exercising muscles, right and left ventricular myocardium, and adrenal glands. However, there were no differences in the circulatory responses to exercise between animals receiving naloxone and normal saline. Thus the endogenous opiate system probably does not play an important role in regulating the systemic hemodynamic and blood flow responses to mild and moderate exercise.     

Ventricular function following acute carbon monoxide exposure.

Cardiac output function curves were used to investigate the effects of carbon monoxide on the heart in the conscious dog. Each dog was briefly exposed to 1,500 ppm carbon monoxide through a permanent tracheostomy. Immediately upon attaining either 10%, 20%, or 30% HbCO a rapid infusion of Ringer's lactate was given to test cardiac capabilities. The combined effects of carbon monoxide and infusion produced significant increases in cardiac output, heart rate, mean left ventricular pressure, dP/dt and (dP/dt)/IP. Cardiac output was sufficient to prevent peripheral hypoxia at all HbCO levels; however, there was evidence of impending cardiac depression beginning at 20% HbCO.     

Congestive heart failure in copper-deficient mice

Copper Deficiency (CuD) leads to hypertrophic cardiomyopathy in various experimental models. The morphological, electrophysiological, and molecular aspects of this hypertrophy have been under investigation for a long time. However the transition from compensated hypertrophy to decompensated heart failure has not been investigated in the study of CuD. We set out to investigate the contractile and hemodynamic parameters of the CuD mouse heart and to determine whether heart failure follows hypertrophy in the CuD heart. Dams of FVB mice were fed CuD or copper-adequate (CuA) diet starting from the third day post delivery and the weanling pups were fed the same diet for a total period of 5 weeks (pre- and postweanling). At week 4, the functional parameters of the heart were analyzed using a surgical technique for catheterizing the left ventricle. A significant decrease in left ventricle systolic pressure was observed with no significant change in heart rate, and more importantly contractility as measured by the maximal rate of left ventricular pressure rise (+dP/dt) and decline (-dP/dt) were significantly depressed in the CuD mice. However, left ventricle end diastolic pressure was elevated, and relaxation was impaired in the CuD animals; the duration of relaxation was prolonged. In addition to significant changes in the basal level of cardiac function, CuD hearts had a blunted response to the stimulation of the beta-adrenergic agonist isoproterenol. Furthermore, morphological analysis revealed increased collagen accumulation in the CuD hearts along with lipid deposition. This study shows that CuD leads to systolic and diastolic dysfunction in association with histopathological changes, which are indices commonly used to diagnose congestive heart failure.     

Effect of methylene blue on cardiac output response to exercise in dogs

To determine whether the increase in cardiac output during mild to moderate exercise is related to an increase in the tissue redox potential, we compared the responses of cardiac output, total body oxygen consumption, and arterial blood lactate-to-pyruvate ratio (a measure of NADH/NAD) to treadmill exercise between dogs treated with normal saline and those treated with a hydrogen acceptor, new methylene blue. Normal saline was infused into the left atrium in the first group of dogs at a rate of 0.38 ml/min throughout the treadmill exercise (2.5 mph and 5.0 mph on a 6% incline, each for 20 min). In the second group, methylene blue was administered as a loading dose (4 mg/kg) before exercise, followed by a continuous infusion (0.15 mg X kg-1 X min-1) throughout exercise. A similar infusion of methylene blue was given to a third group of dogs without exercise; it reduced the arterial lactate-to-pyruvate ratio from 6.70 +/- 0.35 to 4.12 +/- 0.27 but had no or little effects on cardiac output, heart rate, arterial pressure, and left ventricular dP/dt and (dP/dt)/P. Treadmill exercise doubled cardiac output and increased total body O2 consumption three- to fourfold in the first two groups but increased arterial blood lactate-to-pyruvate ratio only in group 1 (6.0 +/- 0.54 to 9.97 +/- 0.91). The relationship between cardiac output and total body O2 consumption was unaffected by the simultaneous administration of methylene blue during exercise. Groups 1 and 2 also did not differ in their heart rate, left ventricular dP/dt and (dP/dt)/P, and plasma catecholamine responses to exercise.(ABSTRACT TRUNCATED AT 250 WORDS)     

Changes in hamster liver albumin synthesis during the development of cardiomyopathy

Control ( F1B ) and cardiomyopathic (Bio 14.6) hamsters have been studied over an 11 month time interval, in an attempt to relate alterations in liver function with the onset of progressive heart damage. In most instances the parameters measured (e.g., liver weight, liver polysome content, in vitro polysome driven protein synthesis) were similar for both groups of animals. The exceptions appeared to be two Bio 14.6 animals that had liver hypertrophy, coupled with severe necrosis and liver damage. These livers had very low levels of virtually inactive polysomes and depicted many of the histopathological characteristics of hepatic ischemic injury known in humans to be associated with congestive heart failure. Our biochemical and histological data suggests that for the Bio 14.6 hamsters, progressive cardiomyopathy is associated with severe liver damage for only a few animals.     

Stimulatory guanine nucleotide-binding protein and adenylate cyclase activities in Bio 14.6 cardiomyopathic hamsters at the hypertrophic stage

The Bio 14.6 cardiomyopathic Syrian hamster is an animal model of human idiopathic cardiomyopathy. The pathogenesis of the disease in this animal has not yet been clearly elucidated. It is well known that α- and β-adrenergic receptors are increased in the myocardium of this animal, but that isoprenaline does not produce an augmented response. We examined the activity of cardiac stimulatory GTP-binding protein (Gs), which couple with β-adrenergic receptors to stimulate adenylate cyclase, in Bio 14.6 cardiomyopathic hamsters at 90 and 160 days of age. The cardiac norepinephrine concentration was significantly increased in Bio 14.6 hamsters compared with control hamsters (F1B) at 90 days of age (1,739±120 vs 1,470±161 ng/g wet tissue weight, p<0.05). Cardiac forskolin-stimulated adenylate cyclase activities at 90 and 160 days of age were lower in the cardiomyopathic hamsters than in the F1B controls (90 days old: 98±24 vs 122±29 pmol/min/mg protein, p<0.05; 160 days old: 74±13 vs 124±28 pmol/min/mg protein, p<0.01). Cardiac Gs activities at 90 and 160 days of age were significantly lower in Bio 14.6 hamsters than those in F1B hamsters (90 days old: 204±42 vs 259±49 pmol/min/mg protein, p<0.05; 160 days old: 156±39 vs 211±60 pmol/min/mg protein, p<0.05). We thus demonstrated functional defects in cardiac Gs protein and adenylate cyclase activity in the Bio 14.6 cardiomyopathic hamsters at 90 to 160 days of age (the hypertrophic stage of cardiomyopathy). Such defects could be one possible mechanism preventing an enhanced response to β-adrenergic stimulation in this animal and could also contribute to myocardial decompensation in the late stage of cardiomyopathy.