Autoimmunity in idiopathic dilated cardiomyopathy. Characterization of antibodies against the beta 1-adrenoceptor with positive chronotropic effect

BACKGROUND

Autoantibodies against the beta 1-adrenoceptor have been detected in the sera of patients with idiopathic dilated cardiomyopathy (DCM). The mechanisms by which these autoantibodies can alter normal receptor function are investigated, and the results are interpreted in the light of the beneficial effects of beta 1-blockade in some of these patients.

METHODS AND RESULTS

Autoantibodies against the beta 1-adrenoceptor, affinity purified from sera of patients with idiopathic DCM, were analyzed in a functional test system of spontaneously beating neonatal rat heart myocytes. Antibodies from rabbits immunized with peptides derived from the amino acid sequence of this receptor were also analyzed. Autoantibodies, against the second extracellular loop increased the beating frequency of isolated myocytes in a concentration-dependent manner, to approximately 80% of maximal isoproterenol stimulation. Rabbit anti-peptide antibodies against the second extracellular loop increased the beating frequency correspondingly. Autoantibodies and rabbit anti-peptide antibodies against the second extracellular loop were able to immunoprecipitate the unliganded receptor but not the antagonist-occupied receptor. In contrast, rabbit antibodies against the extracellular N-terminal sequence 34-57 of the beta 1-adrenoceptor were able to immunoprecipitate both the unliganded and the antagonist-occupied receptor although with no effect on the beating frequency of myocytes. The positive chronotropic effect of the antibodies was completely neutralized both by the addition of increasing concentrations of the beta 1-selective antagonist bisoprolol and by preincubation with the peptide corresponding to the second extracellular loop. The antibody-induced increase in beating frequency remained unchanged for more than 6 hours. This should be compared with the isoproterenol-stimulated beating frequency, which undergoes desensitization within 60 minutes. Addition of isoproterenol to autoantibody-stimulated myocytes resulted in only a small increase in beating frequency and did not cause desensitization. Antibodies had only a marginal effect on cyclic AMP production of stimulated cardiomyocytes compared with the 10-fold increase obtained after stimulation with isoproterenol.

CONCLUSIONS

The second extracellular loop of the beta 1-adrenoceptor is a specific target for antibodies with stimulatory activity detected in patients with idiopathic DCM. The antibodies have a positive chronotropic effect on isolated rat heart myocytes. Autoantibody stimulation does not cause the normal agonist-induced desensitization phenomena of the effector system. These findings could contribute to our understanding of the pathophysiological mechanisms of the autoantibodies and of the beneficial effect of beta 1-blocking agents in the treatment of patients with idiopathic DCM.

Ten-year mortality rate among patients in whom acute myocardial infarction was not confirmed in relation to clinical history and observations during hospital stay: experiences from the Göteborg Metoprolol Trial

BACKGROUND

The majority of patients hospitalized due to suspected acute myocardial infarction (AMI) will eventually not develop infarction. Information about the long-term prognosis in this patient population is limited.

AIM

To describe the mortality during 10 years of follow-up in patients hospitalized due to an initially strong suspicion of AMI, but in whom the diagnosis of AMI could not be confirmed.

PATIENTS

All patients participating in an early intervention trial with metoprolol in suspected AMI, but in whom the diagnosis was not confirmed. Patients were included during 1976-1981.

RESULTS

In all 1395 patients were included in the study, of whom 586 did not fulfil the criteria for confirmed AMI. The overall mortality during 10 years of follow-up in this population was 26%. In a multivariate analysis considering age, sex, history of cardiovascular diseases, initial heart rate and various complications during the hospital stay, including congestive heart failure, severe ventricular arrhythmias, tachycardia, hypotension, high degree AV-block and severe chest pain, the following appeared as independent predictors of death: previous infarction (P < 0.001), age (P < 0.001), history of diabetes mellitus (P < 0.001) history of smoking (P < 0.05), history of hypertension (P < 0.05), male sex (P < 0.05), and the initial heart rate (P < 0.05).

CONCLUSION

Among patients in whom AMI was not confirmed the major risk indicators for death during 10 years of follow-up were: a history of cardiovascular diseases and smoking, age, male sex and high heart rate on admission to hospital.

Improved exercise hemodynamic status in dilated cardiomyopathy after beta-adrenergic blockade treatment

OBJECTIVES

This study was performed to investigate exercise hemodynamic status in a double-blind, placebo-controlled trial and was a substudy in the Metoprolol in Dilated Cardiomyopathy Trial.

BACKGROUND

Previous open studies have shown beneficial effects on exercise hemodynamic status after beta-adrenergic blocking agent therapy in patients with congestive heart failure.

METHODS

The study included 41 patients with idiopathic dilated cardiomyopathy with ejection fraction < 0.40 (metoprolol, 20 patients; placebo, 21 patients) whose hemodynamic status was investigated at rest and during supine submaximal exercise, at baseline and after 6 and 12 months of treatment. Myocardial metabolism was evaluated in a subset of 19 patients.

RESULTS

Metoprolol-treated patients responded favorably, as expressed by improved exercise cardiac index ([mean +/- SD] placebo 4.8 +/- 1.6 to 4.7 +/- 1.8 liters/min per m2, metoprolol 4.3 +/- 1.1 to 5.4 +/- 1.9 liters/min per m2, p = 0.0001) and stroke work index (placebo 44 +/- 20 to 41 +/- 27 g.m/m2, metoprolol 35 +/- 16 to 58 +/- 28 g.m/m2, p < 0.0001). Exercise systolic arterial pressure increased (placebo 161 +/- 25 to 151 +/- 23 mm Hg, metoprolol 155 +/- 29 to 165 +/- 37 mm Hg, p = 0.0003) as well as exercise oxygen consumption index (placebo 463 +/- 194 to 474 +/- 232 ml/min per m2, metoprolol 406 +/- 272 to 507 +/- 298 ml/min per m2, p = 0.045). There was a significant increase in exercise duration in the metoprolol group (63 +/- 38 s) compared with the placebo group (-24 +/- 42 s) (p = 0.01). Net myocardial lactate extraction increased in the metoprolol group, suggesting less myocardial ischemia (placebo 17 +/- 22 to 9.5 +/- 6.4 mmol/min, metoprolol -32 +/- 100 to 42 +/- 45 mmol/min, p = 0.03). Peripheral levels of norepinephrine tended to decrease at rest and during exercise, whereas myocardial net spillover was unchanged.

CONCLUSIONS

Metoprolol improved hemodynamic status in patients with dilated cardiomyopathy at rest and had a more pronounced effect during exercise. These positive effects were achieved along with improved or stable myocardial metabolic data.

The appropriateness of performing coronary angiography and coronary artery revascularization in a Swedish population

OBJECTIVE

To evaluate the appropriateness of performing coronary angiography and revascularization in a Swedish population.

DESIGN

Prospective population study of questionnaires and medical records.

SETTING

All the hospitals in southwestern Sweden that perform coronary angiography and revascularization.

PATIENTS

Random sample of 831 patients (with chronic stable angina) on the waiting list for coronary angiography or revascularization in southwestern Sweden in September 1990.

MAIN OUTCOME MEASURE

Percentage of patients referred for coronary angiography or revascularization for appropriate, uncertain, or inappropriate indications.

RESULTS

Of the patients referred for angiography, 89% were classified as appropriate, 9% as uncertain, and 2% as inappropriate. The percentages are similar for patients referred for coronary artery bypass graft surgery and for angioplasty (91% and 86%, respectively, classified as appropriate). The majority of patients had chest pain rated as Canadian Cardiovascular Society classes II through IV (93%), despite maximum anti-ischemic therapy in 90% of these patients.

CONCLUSIONS

Few patients were referred for coronary angiography or revascularization for inappropriate or uncertain indications. The percentage of these patients who are from southwestern Sweden is similar to the percentage recently reported from New York State.

Properties of G-protein modulated receptor-adenylyl cyclase system in myocardium of spontaneously hypertensive rats treated with adriamycin

Properties of the receptor--G protein--adenylyl cyclase system were studied in spontaneously hypertensive rats (SHR) and age-matched normotensive Wistar-Kyoto rats (WKY) treated with adriamycin (ADR, 1 mg/kg per week) for 12 weeks. An identical dosing schedule caused a significantly greater decline in body weight gain and a marked elevation of plasma norepinephrine level in SHR than in WKY. A significant increase in the messenger RNA encoding Gi-alpha 2 was found in SHR+ADR group. The activity of the adenylyl cyclase stimulated by guanyliminodiphosphate [Gpp(NH)p] was decreased by 49% in SHR and 73% in SHR+ADR. However, stimulated activities of adenylyl cyclase by both sodium fluoride and forskolin remained unchanged. Functional level of stimulatory G-protein (Gs) as measured by reconstitution assay in sarcolemmal membrane was unaltered among different groups. Furthermore, the density of beta-adrenoceptor was significantly decreased without change of its affinity. Muscarinic receptors exhibited a three-site affinity distribution in SHR+ADR whereas other groups displayed only two-site affinity distribution. These results suggest that SHR exhibited a depressed myocardial adenylyl cyclase signaling system which may not be due to the functional uncoupling of beta-adrenoceptors from Gs but to the increased inhibitory G-protein (Gi) activity as demonstrated by the increased mRNA of Gi-alpha 2, increased inhibition of Gpp(NH)p-mediated adenylyl cyclase and the super high affinity for carbachol of the muscarinic receptors. Decreased beta-adrenoceptor density and functional alteration of Gi might be regarded as the predisposing factors for the increased susceptibility of myocardium of SHR to ADR.

Ten year mortality in relation to original size of myocardial infarct: results from the Gothenburg metoprolol study

OBJECTIVE

To describe the relation between the extent of a myocardial infarct, measured according to maximum serum enzyme activity of lactate dehydrogenase, and mortality at 10 years.

PATIENTS

In 759 patients with acute myocardial infarction in whom serum activity of heat stable lactate dehydrogenase had been determined every 12 hours for 108 hours after randomisation in an early intervention trial with metoprolol.

MAIN OUTCOME MEASURE

Mortality at 10 years in relation to quartile of maximum serum lactate dehydrogenase activity and history of cardiovascular disease.

RESULTS

Among all patients mortality at 10 years was 39% in the lowest quartile, 51% in the second quartile, 50% in the third, and 59% in the fourth (p < 0.001 for relation between infarct size and 10 year mortality). Among patients without a history of myocardial infarction, angina pectoris, diabetes mellitus, or hypertension the mortality in each quartile was 29%, 32%, 41%, and 56%, respectively (p < 0.001 for relation between infarct size and 10 year mortality). Among patients with any of these risk indicators the association between the estimated infarct size and mortality at 10 years was weak (p < 0.05).

CONCLUSION

Estimated size of a myocardial infarct and mortality over 10 years seem to be related but mainly in patients without a history of cardiovascular disease.

Empiric therapy with beta-blockers

The only class of drugs with significant effects on ventricular fibrillation and sudden death in humans is that of beta-blockers. The exact mechanisms for these prophylactic effects are not known but may be related to both antiischemic or antiarrhythmic influences. It seems reasonable to suggest that one should use a beta-blocker with proven effect on total mortality and sudden cardiac death after myocardial infarction as prophylaxis. Therefore, propranolol, timolol, or metoprolol, should be instituted in order to improve prognosis when there are no contraindications. In addition to possible effects on survival one would also expect to reduce the risk for new ischemic events with angina or reinfarction. In contrast, class I antiarrhythmic agents are useful for symptomatic ventricular arrhythmias but there is no proof for any effect on ventricular fibrillation and sudden cardiac death.

Immunocytochemical localization of M2 muscarinic receptors in rat ventricles with anti-peptide antibodies

We produced antibodies against a synthetic peptide corresponding to amino acids 168-192 of the second extracellular loop of the M2 human muscarinic receptor in rabbits. In immunoblot, affinity-purified antibodies specifically recognized a major band of rat ventricular muscarinic receptor protein with a molecular weight of about 80 KD. This recognition could be blocked by pre-incubation with peptide. Moreover, with both light (LM) and electron microscopic (EM) immunocytochemistry techniques, muscarinic receptors were detected on sarcolemma and T-tubules of rat cardiomyocytes. In addition, immunoreactions were localized in membranes of capillaries. Likewise, these reactivities were abolished by pre-incubation with peptide. These results suggest that the antibodies against the second extracellular loop of human M2 muscarinic receptor could specifically recognize rat ventricular muscarinic receptor protein and could be a powerful tool to study the fate of this receptor under different pathological or physiological conditions.

The epidemiology of a coronary waiting list. A description of all of the patients

OBJECTIVES

To describe the characteristics and the severity of symptoms amongst patients on the waiting list for possible coronary revascularization.

DESIGN

All the patients were sent a postal questionnaire for symptom evaluation.

SETTING

All hospitals in western Sweden.

SUBJECTS

All patients in western Sweden on the waiting list in September 1990, who had been referred for coronary angiography or revascularization (n = 904) and a sex- and age-matched reference group (n = 809).

RESULTS

More than half of the patients had daily attacks of chest pain, whereas 16% reported less than one attack per week or no pain at all. However, other symptoms such as dyspnoea, tachycardia and nervous reactions were also common and 25% of all patients used sedatives. A long waiting time for a given procedure was not associated with more pain but with more nervous symptoms such as restlessness and insomnia (P < 0.0001) and greater use of sedatives and cigarettes (P < 0.05).

CONCLUSIONS

We conclude that a long waiting time for possible coronary revascularization is associated with more nervous symptoms but not with more pain.

Causes of death in patients presenting to hospital with symptoms suggestive of acute myocardial infarction: a one-year follow-up study with autopsy results

BACKGROUND

About 20% of patients admitted to a medical emergency room have chest pain or other symptoms raising suspicion of acute myocardial infarction.

AIM

To describe the place and mode of death in such patients during 1 year of follow-up.

PATIENTS

All patients (n = 5362) admitted to a single hospital during 21 months because of such symptoms.

RESULTS

In all, 565 patients (11%) died. Death rate was directly related to the initial degree of suspicion of acute myocardial infarction. Of these patients, 196 (35%) died during initial hospitalization and only 89 (16%) died outside the hospital. The overall autopsy rate was 53%. Of the deaths that occurred during initial hospitalization, the majority were judged as cardiac, most being due to acute myocardial infarction, particularly if the patients died in the coronary care unit. Among patients who died after discharge from hospital, non-cardiac factors contributed more substantially to death, particularly in patients who died during rehospitalization. The cause of death was not established in a high proportion of patients who died outside hospital.

CONCLUSION

The results suggest that, among patients admitted to the emergency room because of suspected acute myocardial infarction, causes of death other than a documented cardiac event become increasingly important when the interval between admittance to the emergency room and death increases.

The role of beta-blockers in the treatment of cardiomyopathy and ischaemic heart failure

As first reported by our group in 1975, severe heart failure due to idiopathic dilated cardiomyopathy could be improved in patients receiving beta-blocker therapy starting at a very low dose and followed by a stepwise increase. Since then, these results have been confirmed by our own group and by others, and similar results were also obtained in patients with other forms of cardiomyopathy, including ischaemic cardiomyopathy. In 13 separate studies involving a total of 651 patients with idiopathic dilated cardiomyopathy, beta-blockade for 2 to 19 months (in addition to conventional treatment of heart failure, including angiotensin converting enzyme inhibitor therapy), significantly improved cardiac function. These studies were performed using metoprolol, bucindolol, labetalol and practolol. Eight studies investigated the effects of long term beta-blocker treatment in patients with heart failure and cardiomyopathy due to coronary artery disease, valvular heart disease, diabetes and doxorubicin therapy. A total of 128 patients were treated with metoprolol, carvedilol or bucindolol for periods of 2 to 12 months. All studies reported a significant improvement in cardiac function. Three studies reported results on survival and the need for cardiac transplantation. The first study published by our group reported improved survival in patients with idiopathic dilated cardiomyopathy treated with metoprolol plus digitalis and diuretics compared with a matched control group.(ABSTRACT TRUNCATED AT 250 WORDS)

Ten-year mortality among patients with suspected acute myocardial infarction in relation to early diagnosis

Previous studies have compared the outcome between patients with and without a confirmed acute myocardial infarction (AMI) mainly during the first few years after its onset. Our aim was to compare the prognosis between patients with and without a confirmed AMI during 10 years of follow-up. Patients participating in an early intervention trial with metoprolol in suspected AMI between 1976 and 1981 took part in this evaluation. The total 10-year mortality rate including hospital mortality was 51% for patients with confirmed AMI as compared with 32% for patients with a possible AMI and 23% for patients in whom AMI was definitely ruled out (p < 0.001). The 10-year mortality after discharge from hospital was in AMI 46%, possible AMI 32% and in definitely ruled out AMI 23% (p < 0.001). When simultaneously considering age, sex, previous history of cardiovascular disease and smoking, the development of AMI appeared as an independent predictor of death (p < 0.001). Thus, among patients hospitalized due to suspected AMI, 10-year mortality after discharge from hospital was directly related to the diagnosis during the first 3 days in hospital.

Epitope analysis of T- and B-cell response against the human beta 1-adrenoceptor

Several reports have recently raised the possible significance of the presence of autoantibodies against the beta 1-adrenoceptor in patients with idiopathic dilated cardiomyopathy. An investigation was thus initiated to study the immune response against this receptor at the T-cell and the B-cell level. Using membranes of E coli transfected with the human beta 1-adrenoceptor gene as immunogen, T-helper cells of the immunized mice were stimulated with synthetic peptides derived from the receptor and predicted to be immunogenic to assess the T-cell immunodominant regions of the receptor. Three peptides derived from the second transmembrane region, from the second extracellular loop and from the C-terminal domain were shown to be stimulatory. Synthetic peptides, derived from two domains of the receptor which could be potential targets for autoantibodies, yielded an antibody response after immunization with the free peptides. The peptide derived from the N-terminal region yielded antibodies which recognized the receptor in immunoblot and by immunoprecipitation but they had no functional effect on the receptor. The peptide derived from the second extracellular loop yielded antibodies which recognized the receptor in immunoblot and by immunoprecipitation of the free receptor and which had a pharmacological effect on the receptor. The second extracellular loop thus contains T- and B-cell epitopes which could be involved in the autoimmune process.

Prognosis during one year of follow-up after acute myocardial infarction with emphasis on morbidity

Previous descriptions of the prognosis after acute myocardial infarction (AMI) have mainly included patients admitted to coronary care units, often with an upper age limit. This study describes the prognosis, with emphasis on morbidity, during 1 year in 921 patients admitted to one single hospital with AMI regardless of age and regardless of whether or not they were admitted to the coronary care unit. During the first year, 29% of the patients died and 16% developed a reinfarction. Fifty-four percent required rehospitalization for various reasons, mainly for AMI, chest pain of other origins, and congestive heart failure. After 1 year, 52% of the surviving patients had symptoms of angina pectoris. Among patients younger than 65 years, only 37% were back to work full time after 1 year. Of patients alive after 1 year, 25% fulfilled the following criteria: no reinfarction, no rehospitalization, and no angina pectoris. Of patients aged less than 65 years at follow-up, 12% fulfilled the same criteria and were back to work full time after 1 year. In this unselected, consecutive series of patients with AMI, mortality and morbidity were high during the first year. Only a small percentage of patients were free of events or symptoms of angina pectoris.

Reoxygenation-induced cell damage of isolated neonatal rat ventricular myocytes can be reduced by chain-breaking antioxidants

To study the role of chain-breaking antioxidants on reperfusion injury in the ischemic heart, cultured ventricular heart cells (myocytes) were subjected to hypoxia and reoxygenation. The myocytes were prepared from neonatal rats and cultured in F10 medium that was supplemented with serum. As a marker for cell damage, lactate dehydrogenase was analyzed in the medium. Cells subjected to hypoxia for 5 h showed a 1.9 fold increase in lactate dehydrogenase (LD) leakage, while cells subjected to 1 h hypoxia followed by 4 h reoxygenation showed a 5-fold increase in LD intake. Alpha-tocopherol, beta-carotene, nordihydroguairetic acid (NDGA), butylated hydroxyltoluene (BHT), and ICI211965 were added to the cell medium every 24 h for 6 d prior to reoxygenation. All compounds protected against reoxygenation-induced cell damage. In the presence of the 5-lipoxygenase inhibitor ICI211965, protection against LD leakage was found only at high concentrations, which corresponded to the antioxidative effect of ICI211965, and not to inhibition of 5-lipoxygenase. We conclude that cultured ventricular myocytes can be used to evaluate the protective effect of antioxidants on reoxygenation-induced cell damage, and that chain-breaking antioxidants protected well against reoxygenation-induced cell damage.

Beneficial effects of metoprolol in idiopathic dilated cardiomyopathy. Metoprolol in Dilated Cardiomyopathy (MDC) Trial Study Group

Several small studies have suggested beneficial effects of long-term beta-blocker treatment in idiopathic dilated cardiomyopathy. Our large multicentre study aimed to find out whether metoprolol improves overall survival and morbidity in this disorder. 383 subjects with heart failure from idiopathic dilated cardiomyopathy (ejection fraction < 0.40) were randomly assigned placebo or metoprolol. 94% were in New York Heart Association functional classes II and III, and 80% were receiving background treatment. A test dose of metoprolol (5 mg twice daily) was given for 2-7 days; those tolerating this dose (96%) entered randomisation. Study medication was increased slowly from 10 mg to 100-150 mg daily. There were 34% (95% CI -6 to 62%, p = 0.058) fewer primary endpoints in the metoprolol than the placebo group; 2 and 19 patients, respectively, deteriorated to the point of needing transplantation and 23 and 19 died. The change in ejection fraction from baseline to 12 months was significantly greater with metoprolol than with placebo (0.13 vs 0.06, p < 0.0001). Pulmonary capillary wedge pressure decreased more from baseline to 12 months with metoprolol than with placebo (5 vs 2 mm Hg, p = 0.06). Exercise time at 12 months was significantly greater (p = 0.046) in metoprolol-treated than in placebo-treated patients. In patients with idiopathic dilated cardiomyopathy, treatment with metoprolol prevented clinical deterioration, improved symptoms and cardiac function, and was well tolerated.

Ten-year mortality rate after development of acute myocardial infarction in relation to clinical history and observations during hospital stay: experience from the Göteborg metoprolol trial

BACKGROUND

Previous studies on the prognosis after acute myocardial infarction (AMI) have mainly focused on the first few years. In this study, we aimed to describe the mortality rate during 10 years of follow-up after development of AMI in relation to clinical history and observations during the hospital stay.

METHODS

We prospectively followed for 10 years all patients with suspected AMI, enrolled between 1976 and 1981, participating in an early intervention trial with metoprolol who fulfilled given criteria for AMI.

RESULTS

A total of 809 patients developed AMI during the first 3 days in hospital, of whom 399 were randomly assigned to receive metoprolol and 410 to receive placebo. The overall 10-year mortality rate, including initial in-hospital mortality, was 51%. In a multivariate analysis considering age, sex, history of cardiovascular diseases, estimated infarct size, and the occurrence of various complications during initial hospitalization (i.e. congestive heart failure, severe ventricular arrhythmias, tachycardia, hypotension, high-degree atrioventricular block and severity of pain) the following appeared as independent predictors of death: a history of diabetes mellitus (P < 0.001), congestive heart failure during hospitalization (P < 0.001), age (P < 0.001), and a history of previous myocardial infarction (P < 0.001).

CONCLUSION

Independent predictors of death during the first 10 years after AMI were a history of diabetes mellitus, congestive heart failure during hospitalization, age, and previous myocardial infarction.

Hypersensitivity of Gi protein mediated muscarinic receptor adenylyl cyclase in chronic ischaemic heart failure in the rat

OBJECTIVE

The aim was to study the Gi protein mediated muscarinic signalling system in the myocardium of rats with chronic ischaemic heart failure.

METHODS

Chronic ischaemic heart failure was induced by myocardial ischaemia (four weeks after coronary artery ligation) in rats. The densities and agonist affinities of muscarinic receptors, and the functional activity and concentration of Gi proteins were studied.

RESULTS

In failing hearts, the activity of adenylyl cyclase stimulated by guanyliminodiphosphate (Gpp(NH)p) was decreased by 46%. Stimulated activities of adenylyl cyclase by both sodium fluoride and forskolin, however, remained unchanged. Carbachol depressed forskolin stimulated adenylyl cyclase more in membranes from failing hearts than those from normal hearts. The functional level of Gs protein as measured by a reconstitution assay in sarcolemmal membrane did not differ between the two groups. Furthermore, muscarinic receptors exhibited superhigh and low affinities for agonist in failing hearts whereas those in control hearts displayed only high and low affinities. No significant difference in the peptide equivalent amount of membrane bound Gi protein was found in either group.

CONCLUSIONS

The experimental chronic failing heart due to myocardial ischaemia showed a depressed myocardial adenylyl cyclase signalling system. This may be due to the hypersensitivity of the Gi protein mediated muscarinic receptor-adenylyl cyclase system as shown by the increased inhibition of Gpp(NH)p mediated adenylyl cyclase, more potent inhibition of stimulated adenylyl cyclase by carbachol, and the superhigh affinity of the muscarinic receptors for carbachol.

Prognosis in men and women coming to the emergency room with chest pain or other symptoms suggestive of acute myocardial infarction

BACKGROUND

Previous studies suggest a gender-related difference in prognosis among patients with ischaemic heart disease. In the present study, we aimed to describe the characteristics and prognosis among patients with suspected ischaemic heart disease in relation to gender.

METHODS

During the 21 months of the study, all patients who came to the medical emergency room of one single hospital as a result of chest pain or other symptoms suggestive of acute myocardial infarction were prospectively followed for 1 year.

RESULTS

A total of 5362 patients were admitted on 7157 occasions; men accounted for 55% of the admissions. The 1-year mortality rate was 11% for men compared with 10% for women. The women were older and had a higher prevalence of known congestive heart failure and hypertension, whereas the prevalence of previous myocardial infarction was higher in men. When correcting for the dissimilarities in age and history of cardiovascular diseases, male gender appeared as an independent predictor of death. Development of myocardial infarction occurred in 25% of the men and 16% of the women (P < 0.001) during 1 year. The symptoms that brought patients to the emergency room were interpreted as being caused by myocardial infarction or myocardial ischemia in 29% of men compared with 21% of women (P < 0.001).

CONCLUSIONS

In a consecutive series of patients with chest pain or other symptoms suggesting acute myocardial infarction in the emergency room, male gender was an independent risk indicator for death during 1 year. This might be explained by a higher occurrence of coronary artery disease in men than in women in this patient population.

Decreased density of mesenteric arteries but not of myocardial endothelin receptors and function in rats with chronic ischemic heart failure

Mesenteric artery and cardiac ventricular endothelin receptors and endothelin-1-induced pressor responses were studied in normal rats and rats with chronic congestive heart failure induced by myocardial ischemia (4 weeks after coronary artery ligation). In mesenteric arteries of rats with chronic ischemic heart failure, endothelin receptor density was significantly decreased by 59%, whereas the dissociation constant was increased 2.8-fold, as compared with controls. There were, however, no changes in endothelin-receptor density or the dissociation constant in cardiac ventricular membrane preparations from rats with congestive heart failure as compared with controls. In pithed rats with congestive heart failure there was a reduced pressor response to a bolus injection of endothelin-1 (800 pmole/kg body weight), while the vasodilatory response was unaltered as compared with sham-operated controls. These results demonstrate that there is a decreased vascular endothelin-receptor function due to a down-regulated endothelin receptor. The in vivo data indicate that this is due to impaired endothelin A but not endothelin B receptor function. Thus, there is an impaired arterial but not cardiac ventricular endothelin receptor-mediated signalling system in the rat with chronic ischemic heart failure.

Prognosis of acute myocardial infarction in diabetic and non-diabetic patients

We evaluated the prognosis of 858 patients with acute myocardial infarction (MI), of whom 97 (11%) had a history of diabetes mellitus. Among patients with diabetes the 1-year mortality rate was 41% versus 26% for non-diabetic patients (p < 0.01), and the 1-year reinfarction rates were 23% and 14%, respectively (p = 0.05). Diabetic patients with a history of hypertension had a similar mortality rate as compared with diabetic patients without hypertension. In a multivariate analysis including age and history of cardiovascular disease, diabetes did not significantly contribute to death or reinfarction. Among diabetic patients the only independent risk factor for death was age. The place and mode of death appeared similar in the two groups. Patients with and without a history of diabetes had a similar infarct size. We conclude that diabetic patients with acute myocardial infarction have a very poor prognosis. Within 1 year nearly half of them are dead and one-quarter develop reinfarction. The mode of death appeared to be similar in diabetic patients as compared with non-diabetic patients.

Localization of a functional autoimmune epitope on the muscarinic acetylcholine receptor-2 in patients with idiopathic dilated cardiomyopathy

A peptide corresponding to the sequence 169-193 of the second extracellular loop of the human muscarinic acetylcholine receptor-2 was used as an antigen to screen sera from patients with idiopathic dilated cardiomyopathy (DCM, n = 36) and healthy blood donors (HBD, n = 40). The sera from 14 patients with DCM (38.8%) and 3 HBD (7.5%) recognized the muscarinic receptor peptide at dilutions varying from 1:20 to 1:160 in ELISA. A highly significant correlation (P = 0.006) was found between the presence of antimuscarinic receptor-2 autoantibodies and anti-beta-adrenoceptor-1 autoantibodies in the patients' sera. Affinity-purified autoantibodies from positive sera of patients with DCM recognized on the electrotransferred protein of rat ventricular membrane a major band of about 80 kD. Incubation of autoantibodies with membrane resulted not only in a decrease in the maximal binding sites (Bmax) but also in an increase in Kd of radioligand binding in a concentration-dependent manner. This suggests a mixed-type of inhibition. Moreover, preincubation with atropine abolished the inhibitory effect of autoantibodies on the receptor binding whereas carbachol appeared to have no effect on the activity of the autoantibodies. These data define a subgroup of patients with idiopathic DCM who have in their sera functionally active autoantibodies against muscarinic receptor-2.

One-year prognosis in patients hospitalized with a history of unstable angina pectoris

The prognosis during 1 year of follow-up in 715 patients admitted to one single hospital due to suspected acute myocardial infarction (AMI) with a history of unstable angina pectoris immediately preceding hospitalization is described. AMI developed in 192 patients (27%) during the first three days and in 255 patients (38%) during the first year. The mortality during hospitalization was 7% (50 patients) and during 1 year 19% (130 patients). Of the nonsurvivors, 54% died of AMI, 28% of congestive heart failure, and 20% of cardiogenic shock. Based on simple clinical parameters on admission to the emergency room, risk indicators for death during the following year could be identified as follows, in the order of significance: high age (p < 0.001), ST-segment depression on admission (p < 0.001), and a history of diabetes mellitus (p < 0.05). At admission to the emergency room, risk indicators for development of AMI during the following year were as follows: initial degree of suspicion of AMI (p < 0.001), electrocardiographic signs of acute ischemia on admission (p < 0.001), ST-segment elevation on admission (p < 0.01), age (p < 0.05), and lack of a previous history of chronic stable angina pectoris (p < 0.05). We conclude that, among patients admitted to hospital due to suspected AMI with a history of unstable angina pectoris immediately preceding hospitalization, 38% developed a confirmed infarction and 19% died during the following year.

Occurrence of angina pectoris prior to acute myocardial infarction and its relation to prognosis

In 917 patients with acute myocardial infarction (AMI) we evaluated the impact of previous angina pectoris on the prognosis. Thirty-four percent of the patients had chronic angina prior to AMI, and 22% had angina pectoris of short duration. Patients with chronic angina pectoris differed from the remaining patients having a more frequent previous history of AMI, diabetes mellitus, hypertension, and congestive heart failure. They less frequently developed a Q-wave AMI, and had smaller infarcts according to maximum serum-enzyme activity as compared with the remaining patients. They had a higher one-year mortality rate (36%) as compared with those having angina pectoris of short duration (22%), and those with no angina pectoris (26%). Their reinfarction rate was also higher (26%) as compared with that in the other two groups (15% and 9% respectively). In a multivariate analysis considering age, sex, clinical history, initial symptoms, initial electrocardiogram and estimated infarct size, previous chronic angina pectoris was not an independent risk factor for death, but was independently associated with the risk of reinfarction (P < 0.001). Among patients with a history of angina pectoris the outcome was related to medication prior to onset of AMI and at discharge from hospital. Patients in whom beta-blockers were prescribed at discharge had a one-year mortality of 13% as compared with 30% in the remaining patients (P < 0.001).