Free radical scavenging enzymes and G protein mediated receptor signalling systems in ischaemically preconditioned porcine myocardium

OBJECTIVE

Increased antioxidant defence and altered G protein mediated receptor signalling systems could be expected in myocardial preconditioning. The myocardial antioxidant defence and the integrity of the G protein mediated receptor signalling systems were therefore examined in normal and preconditioned myocardium.

METHODS

Preconditioning in the porcine heart was induced by two occlusions of the mid left anterior descending coronary artery for 10 min, with a 30 min reperfusion interval. Left ventricular biopsies were obtained from control and preconditioned regions 30 min after the last occlusion.

RESULTS

In biopsies from the preconditioning region, neither the activities of superoxide dismutase of glutathione peroxidase, nor the content of malondialdehyde were changed. There were no alterations in either the number of receptors (beta adrenergic, muscarinic and endothelin receptors) or the amount of G proteins. Furthermore, the activity of adenylyl cyclase remained unchanged.

CONCLUSIONS

No change in the antioxidant defence was demonstrated in preconditioned myocardium. This finding does not support the hypothesis that increased antioxidant defence could contribute to the cardioprotection of preconditioning. Additionally, an intact G protein mediated receptor signalling system was found in preconditioned myocardium with regard to beta adrenergic, muscarinic, and endothelin receptors.

Delay time between onset of myocardial infarction and start of thrombolysis in relation to prognosis

In 292 patients with suspected acute myocardial infarction given thrombolytic agents, we describe the delay time between the onset of pain and the start of thrombolysis and relate the observations to the prognosis. In 3%, treatment was started 1 h or less and in 22% 2 h or less after onset of symptoms. The median delay time between onset of symptoms and arrival in hospital was 1 h 38 min, and the median delay time between the arrival in hospital and start of thrombolysis was 1 h 25 min. A very strong association between delay time to thrombolysis and mortality during 2 weeks and 1 year of follow-up was observed.

Increase in functional activity rather than in amount of Gi-alpha in failing human heart with dilated cardiomyopathy

OBJECTIVE

The aim was to investigate whether or not increased pertussis toxin catalysed ADP ribosylation correlates with increased amount of Gi-alpha in failing human heart.

DESIGN

Antisera raised against unique synthetic peptides corresponding to alpha subunits of Gs and Gi 1-3 were used in immunoblotting and ELISA to determine amounts of various G proteins. Adenylyl cyclase activity, beta adrenoceptors, and muscarinic receptors were then measured in cardiomyopathic hearts (n = 6) obtained at transplant in order to study whether or not an altered expression of G proteins has relevance to the integrity and function of the receptor--adenylyl cyclase system. Six non-failing control hearts were also studied.

RESULTS

No significant differences in the peptide equivalent amounts of either Gs or Gi were found in the failing human heart as compared to the non-failing heart. However, functional activity of Gi was shown to increase significantly since there was a decrease in basal (57%), isoprenaline stimulated (60%), and guanyliminodiphosphate stimulated (52%) adenylyl cyclase activity. In contrast the density of beta adrenoceptors was markedly decreased (51%) in failing human heart in comparison to non-failing hearts. Neither the density nor the affinity of muscarinic receptors changed in the failing human heart.

CONCLUSION

These results suggest that in the failing human heart, there is an increase in functional activity rather than in amount of Gi, and an important part of functional expression of Gi-alpha may be regulated at the post-translational level.

Prognosis in hypertensives with acute myocardial infarction

OBJECTIVES

A previous history of hypertension is overrepresented among patients with ischaemic heart disease. The present study aims at describing the influence of a previous history of hypertension upon the prognosis among patients hospitalized due to acute myocardial infarction.

DESIGN

Patients were followed for 1 year. Mortality and morbidity are described during hospitalization and after discharge from hospital.

SETTING

Sahlgrenska Hospital, serving half of the area of Gothenburg in Sweden.

PATIENTS

All patients admitted to Sahlgrenska Hospital during 21 months due to acute myocardial infarction regardless of age and whether they were admitted to the coronary care unit.

RESULTS

Among all patients with confirmed acute myocardial infarction (n = 917) a previous history of hypertension was reported in 324 patients. Hypertensives more frequently had a previous history of acute myocardial infarction, angina pectoris, congestive heart failure and diabetes mellitus. Their mortality during hospitalization was similar to that in normotensives. However, the total mortality during 1 year of follow-up was 35% in hypertensives and 25% for normotensives (P < 0.01), and a previous history of hypertension was an independent risk indicator for death after discharge from hospital. Place and mode of death appeared similar in normotensives and hypertensives. Reinfarction was twice as common in hypertensives as in normotensives, and a previous history of hypertension was an independent risk indicator for reinfarction.

CONCLUSIONS

Among patients with acute myocardial infarction a previous history of hypertension indicates a poor prognosis, one-third of patients dying and one-quarter developing reinfarction during the first year after onset of acute myocardial infarction.

Prognosis for patients with initially suspected acute myocardial infarction in relation to presence of chest pain

In all 4,232 patients admitted to a single hospital during a 21-month period due to initially suspected acute myocardial infarction (AMI), the prognosis and risk factor pattern were related to whether patients had chest pain or not. Symptoms other than chest pain that raised a suspicion of AMI were mainly acute heart failure, arrhythmia, and loss of consciousness. In 377 patients (9%) symptoms other than chest pain raised an initial suspicion of AMI. These patients developed a confirmed infarction during the first three days in hospital with a similar frequency (22%) as compared with patients having chest pain (22%). However, patients with "other symptoms" had a one-year mortality of 28% versus 15% for chest pain patients (p less than 0.001). Patients with "other symptoms" more often died in association with ventricular fibrillation and less often in association with cardiogenic shock as compared with chest pain patients. Among the 921 patients who developed early AMI, 64 (7%) had symptoms other than chest pain. They had a one-year mortality of 48% versus 27% for chest pain patients (p less than 0.001). We conclude that in a nonselected group of patients hospitalized due to suspected AMI, those with symptoms other than chest pain have a one-year mortality, which is nearly twice that of patients with chest pain.

Oxygen free radical injury and Gs mediated signal transduction in the stunned porcine myocardium

OBJECTIVE

The aim was to investigate involvement of oxygen free radicals and any changes in the Gs mediated beta adrenergic signalling system of stunned porcine myocardium.

METHODS

Myocardial stunning was induced in eight pentobarbitone anaesthetised pigs by brief occlusions of the distal left anterior descending coronary artery for periods of up to 10 min. Segment length function was measured in the ischaemic region and in a control region supplied by the circumflex artery. Left ventricular biopsies were obtained from the two regions 1 h after the last occlusion for ultrastructural and biochemical studies. Timolol has been used to prevent arrhythmia during ischaemia.

RESULTS

At the time when biopsies were obtained, percent systolic shortening was reduced to 58% in the region subjected to ischaemia and was only minimally reduced in the control region. In the biopsies from the stunned region: (1) electron microscopy showed mild and reversible intracellular changes in the stunned myocardium; (2) the activities of superoxide dismutase and glutathione peroxidase were decreased by 66% and 52%, respectively; (3) the content of malondialdehyde was increased by 49%; (4) neither density nor affinity of beta adrenoceptors showed any changes; (5) there were no alterations in messenger RNA encoding for the alpha subunit of the stimulatory guanine nucleotide binding protein (Gs), demonstrated by northern and dot-blot hybridisations; (6) ELISA technique utilising a specific antipeptide antibody showed no quantitative change in Gs; (7) the activity of adenyl cyclase was unchanged.

CONCLUSIONS

Even though the stunned porcine myocardium showed substantial evidence of free radical injury, the beta adrenergic signalling system was intact.

Metoprolol-induced reduction in postinfarction mortality: pooled results from five double-blind randomized trials

Several postinfarction trials have evaluated the effect of secondary prophylaxis with different beta-blockers. Although so called meta-analysis of the results from all the trials have shown a beneficial effect of postinfarction beta-blockade, many of the individual studies have shown inconclusive results, mainly due to low statistical power. In order to obtain an evaluation of the merits of postinfarction therapy with metoprolol, data from the five available studies with metoprolol have been pooled into one database. In the total material 5474 patients (4353 men, 1121 women) have been studied during double-blind therapy with metoprolol 100 mg twice daily or matching placebo. The follow-up ranges from 3 months to 3 years. In total 4732 patient years of observation have been obtained. In total there were 223 deaths in the placebo-treated patients as compared to 188 deaths in the metoprolol-treated patients (P = 0.036), which corresponds to mortality rates of 97.0 and 78.3 per 1000 patient years, respectively. The mortality reduction was found both in men and women. As has been reported from individual postinfarction beta-blocker trials, the pooled results showed a marked reduction in sudden deaths (104 in the placebo group, 62 in the metoprolol group, P = 0.002). In a Cox regression model the influence of sex, age and smoking habits on the effect of metoprolol was evaluated. None of these factors influenced the metoprolol effect significantly. It is concluded that metoprolol therapy after acute myocardial infarction reduces the total number of deaths, and especially sudden cardiac deaths. The mortality reduction was independent of gender, age and smoking habits. Available data support a continuous beneficial effect.

Characteristics and prognosis of patients with acute myocardial infarction in relation to whether they were treated in the coronary care unit or in another ward

The characteristics and the prognosis in 921 consecutive patients with acute myocardial infarction (AMI) admitted to one single hospital are described and related to whether they were treated in the coronary care unit or not. Patients treated in the coronary care unit (n = 779) had a 1-year mortality rate of 26% as compared with 41% for patients treated in general wards (n = 115; p < 0.001) and 74% for patients treated in the intensive care unit (n = 27; p < 0.001). Patients treated outside the coronary care unit had a different risk factor pattern including a higher age and a higher prevalence of a previous cardiovascular disease. Independent clinical risk indicators for death among patients in the coronary care unit were in order of significance, high age (p < 0.001), arrhythmia on admission (p < 0.01), acute congestive heart failure on admission (p < 0.01) and a history of diabetes mellitus (p < 0.05). In patients treated in general wards, the only risk indicator for death was a history of congestive heart failure.

Prognosis in diabetics with chest pain or other symptoms suggestive of acute myocardial infarction

We evaluated the prognosis of 599 diabetics who came to the emergency department with chest pain or other symptoms suggestive of acute myocardial infarction (AMI). They made up 8% of the patients with such symptoms (n = 7,157). Diabetics had a 1-year mortality rate of 25% as compared with 10% for nondiabetics (p less than 0.001). The difference remained significant regardless of whether there was a strong or a vague initial suspicion of AMI. On admission, independent risk factors for death were age, acute congestive heart failure and initial degree of suspicion of AMI. We conclude that among diabetics who appear in the emergency department with chest pain or other symptoms suggestive of AMI, 25% are dead within 1 year. The prognosis is directly related to the initial suspicion of AMI.

Occurrence of chest pain more than 24 hours after hospital admission in acute myocardial infarction and its relation to prognosis

In 857 consecutive patients with acute myocardial infarction (AMI), the occurrence of chest pain more than 24 h after hospital admission is described and related to death or reinfarction during one year of follow-up. Prolonged chest pain was observed in 333 patients (39%). In this group 15% died and 7% developed reinfarction during the first month as compared with 10% (p < 0.05) and 2% (p < 0.01) respectively in patients without prolonged pain. However, during one year of follow-up mortality did not differ significantly between patients with (27%) and without (24%) prolonged pain. The 1-year reinfarction rate was similar in the two groups (18% and 14%, respectively; NS). We conclude that AMI patients with prolonged chest pain have a particularly high mortality during the first month. However, during a longer follow-up the prognosis is similar in patients with and without prolonged chest pain.

Functional analysis of rabbit anti-peptide antibodies which mimic autoantibodies against the beta 1-adrenergic receptor in patients with idiopathic dilated cardiomyopathy

A synthetic peptide corresponding to the second extracellular loop of the beta 1-adrenergic receptor was used as an antigen for antibody production in three rabbits. Antibodies of high titers were obtained in all rabbits. Only one rabbit yielded antibodies which decreased radioligand binding on the receptor in a similar way to that described for autoantibodies in patients with dilated cardiomyopathy. These antibodies recognized the receptor protein in immunoblots. Epitope mapping indicated that the N-terminal sequence of the loop used as antigen was the target of the major antigen fraction. Incubation of antibodies with C6 glioma cell membranes or inner membranes of E. coli, which express the human beta 1-adrenergic receptor, resulted in a decrease in number of radioligand binding sites. This decrease was dependent on the concentration of antibody and of Mg++ ions. It was not affected by the GTP analog GppNHp or the beta 1 subtype-specific antagonist metoprolol. The agonist, isoproterenol, also induced a decrease but the effects of antibody and agonist were not additive. These results suggest that the antibodies induce a Mg(++)-dependent, 'active', labile conformation of the receptor, independent from coupling to the GTP regulatory protein, but similar to that induced by the agonist isoproterenol. This interpretation was corroborated by the beta 1-adrenergic receptor agonist-like effect of the antibodies on cardiomyocytes in culture.

Myocardial infarction. Effects of beta-blockade

By the mid 1960s a beneficial effect of post-myocardial infarction treatment with beta-blockade had been proposed. However, it was not until 1981 that large clinical trials clearly demonstrated a beneficial effect both in terms of reduction in mortality and morbidity. Today treatment with beta-blockers both in the acute phase of acute myocardial infarction as well as in the stable post-myocardial infarction patient is well established. In this review article, different aspects of early and late treatment with beta-adrenoceptor blockers are discussed. The cardioprotective effects of beta-blockers on mortality and morbidity should not be considered class effects valid for all beta-blockers. Pooled data have clearly demonstrated that beta-blockers with intrinsic sympathomimetic activity have less marked effects. Impressive effects on mortality and morbidity have been obtained with propranolol, timolol, and metoprolol, which are noncardioselective as well as more beta 1-selective (metoprolol), but they are all lacking intrinsic sympathomimetic activity and, furthermore, have a relatively high degree of lipophilicity. It is clear that acute beta-adrenoceptor blockade in suspected acute myocardial infarction reduces mortality and morbidity as well as complications such as chest pain and ventricular arrhythmias during the acute phase. In post-myocardial infarction treatment, it is clear that both mortality and morbidity are reduced. Reports from extended follow-ups after termination of initial double-blind beta-blocker studies in postinfarction patients indicate that withdrawal of the active treatment may increase mortality after cessation of treatment. This is observed despite measures having been taken to avoid so-called acute withdrawal phenomena.(ABSTRACT TRUNCATED AT 250 WORDS)

New therapeutic strategies in chronic heart failure: challenge of long-term beta-blockade

It is claimed that long-term treatment with beta-blockers improves cardiac function and exercise capacity in patients with various forms of congestive heart failure. This was first reported by Waagstein and coworkers in patients with idiopathic dilated cardiomyopathy in 1975 and was later confirmed in 8 further studies in this type of patient. A total of 211 patients with idiopathic dilated cardiomyopathy were treated for 12-19 months. About two thirds of the patients have improved to some extent. Seven other studies reported favourable long-term effects of beta-blockers in 120 patients with other forms of dilated cardiomyopathy, e.g. caused by coronary artery disease, adriamycin, diabetes, or valvular heart disease. Pooled data from 10 studies on 153 patients with various forms of cardiomyopathy, showed that ejection fraction was improved by 40% from 27 to 38%. Only two studies were inconclusive, both with only one month's treatment. In all studies with favourable effects of long-term beta-blockade, treatment was given for more than 2 months and in most cases for about 6 months. A number of beta-blockers have been used in the studies, including acebutulol, alprenolol, bucindolol, labetalol, metoprolol, practolol and propranolol. In most cases, a rather low dose was given initially and there was a stepwise increase in the dosages. After 6-8 weeks most patients were given beta-blockers in daily doses comparable to those given in patients with angina pectoris and hypertension. There is at present no indication that one beta-blocker is superior to others. It therefore seems reasonable to believe that the effects are due to beta 1-blockade.(ABSTRACT TRUNCATED AT 250 WORDS)

Prognosis in acute myocardial infarction in relation to development of Q waves

In a totally nonselected group of patients with acute myocardial infarction (AMI) (n = 921) admitted from the emergency department to the coronary care unit or other hospital ward, the occurrence of non-Q-wave AMI and the prognosis in these patients was determined and compared with those in whom Q waves were developed. Fifty-two percent had AMI without new Q waves. Patients with a non-Q-wave AMI differed from patients with Q-wave AMI, more frequently having a previous history of AMI (p less than 0.001), angina pectoris (p less than 0.01), diabetes mellitus (p less than 0.05), congestive heart failure (p less than 0.001), and a higher mean age (p less than 0.001), whereas smoking was more common in Q-wave AMI. Patients with non-Q-wave AMI had a 1-year mortality of 31% compared with 26% in Q-wave AMI (p greater than 0.2) and a reinfarction rate of 20% compared with 12% for Q-wave AMI (p less than 0.01). Among patients aged less than 75 years without a previous history of AMI, congestive heart failure, and diabetes mellitus, the 1-year mortality rate was 16% for patients with Q waves versus 15% for those without Q waves (NS). Appearance of Q waves was not independently associated with death. We conclude that in a nonselected group of patients with AMI the occurrence of a non-Q-wave AMI is much higher than previously reported. The prognosis in AMI during one year of follow-up is not associated with development of Q waves.

One-year mortality rate after discharge from hospital in relation to whether or not a confirmed myocardial infarction was developed

Consecutive patients admitted to our hospital with suspected acute myocardial infarction during 21 months were prospectively evaluated. One-year mortality after discharge from hospital was related to whether or not an infarction developed (infarct versus non-infarct patients). Of patients discharged alive after developing an infarct, there was a mortality of 17% (n = 777) versus 12% (n = 1830) (P less than 0.001) for all patients not developing infarction. In a high risk group (any of the following: age greater than or equal to 75 years, previous history of myocardial infarction, diabetes mellitus or congestive heart failure) patients developing infarction had a mortality of 24% (n = 457) versus 17% (n = 1221) for those who did not (P less than 0.001). In a low risk group (none of the high risk criteria), the corresponding mortality was 8% (n = 316) for patients suffering infarction and 3% (n = 603) for those not having infarction (P less than 0.001). The difference in mortality between patients with and without infarction was most marked in women (21% vs 11%; P less than 0.01) and in hypertensives (25% vs 12%; P less than 0.001), but less marked in men (16% vs 13%; NS) and in patients without hypertension (13% vs 12%; NS). Among patients not suffering infarction, mortality was particularly high in those with previous congestive heart failure (23%) and diabetes mellitus (21%).

Serum lipids and lipoproteins in relation to restenosis after coronary angioplasty

Restenosis after coronary angioplasty (PTCA) is a major problem, limiting the long-term efficacy of the procedure. Lipoprotein levels are associated with the development of atherosclerosis and may also be associated with restenosis. In this study the serum levels of cholesterol (CH), triglycerides (TG), high density lipoprotein (HDL) and low density lipoprotein (LDL) were analysed in 157 patients undergoing 161 PTCA procedures. Follow-up coronary angiograms were performed after 6.0 +/- 4.3 months. The restenosis rate was 33%. Treatment with aspirin and a residual stenosis of 25-49% immediately after successful PTCA were the only variables associated with restenosis (P less than 0.05), otherwise the clinical and angiographic characteristics were similar with and without restenosis. There was no relationship between restenosis and the levels of CH, TG, HDL or LDL (P greater than 0.05). In univariate and multivariate analysis of males (n = 121) and females (n = 40) separately, restenosis was associated with low HDL in men and high HDL in women (P less than 0.05), but not with CH, TG or LDL (P greater than 0.05). We conclude that the serum levels of CH, TG and LDL do not seem to be related to restenosis after PTCA. It is suggested that low HDL in males and high HDL in females is related to restenosis.

Patients admitted to the emergency room with symptoms indicative of acute myocardial infarction

All 7157 patients (55% men) admitted to the emergency room with chest pain or other symptoms indicative of acute myocardial infarction during a period of 21 months were registered consecutively. Chest pain was reported by 93% of the patients. On the basis of history, clinical examination, and electrocardiogram in the emergency room, all patients were prospectively classified in one of four categories: (i) obvious infarction (4% of all patients); (ii) strongly suspected infarction (20%); (iii) vague suspicion of infarction (35%); and (iv) no suspected infarction (41%). In patients with no suspected infarction (n = 2910), musculoskeletal (26%), obscure (21%) and psychogenic origins (16%) of the symptoms occurred most frequently. We conclude that few of the patients had an obvious infarction on admission, and that a musculoskeletal origin of the symptoms occurred most frequently in patients with no suspected infarction.

Early prediction of acute myocardial infarction from clinical history, examination and electrocardiogram in the emergency room

The possibility of early prediction of acute myocardial infarction (AMI) was assessed in 7,157 consecutive patients coming to our emergency room during a 21-month period with chest pain or other symptoms suggestive of AMI. Of these patients 921 developed an AMI during the first 3 days in the hospital. Of the 4,690 patients admitted to hospital, 1,576 (34%) had a normal admission electrocardiogram, and 90 of these (6%) developed AMI. Of 1,964 patients with an abnormal electrocardiogram without signs of acute ischemia (42% of those admitted), 268 (14%) developed AMI, and 563 (51%) of 1,109 patients with acute ischemia on the electrocardiogram (24%) developed AMI. All patients were prospectively classified in the emergency room on the basis of history, clinical examination and electrocardiogram into 1 of 4 categories, according to the initial degree of suspicion of AMI. Of 279 admitted patients judged to have an obvious AMI (6% of the 4,690), 245 (88%) actually developed AMI; of 1,426 with a strong suspicion of AMI (30%), 478 (34%) developed one; of 2,519 with a vague suspicion of AMI (54%), 192 (8%) developed one; and of 466 with no suspicion of AMI (10%), 6 (1%) developed one. Thus, only a low percentage of the patients with a normal initial electrocardiogram or a vague initial suspicion of AMI developed a confirmed AMI.

Long-term follow-up of health-related quality of life in patients with suspected acute myocardial infarction when the diagnosis was not confirmed

This study describes the outcome in terms of health-related quality of life (QL) five years after onset of symptoms in 397 patients with an initial suspicion of acute myocardial infarction (MI) but in whom the diagnosis was not confirmed. The patients were approached by means of a postal inquiry that comprised two questionnaires. The most pronounced impairment in health-related QL was expressed as decreased energy, whereas social life was the least affected area. The overall QL was very similar to that in patients who had a confirmed MI. Subsets of patients with impaired QL were those given the diagnosis of angina pectoris or possible infarction.

Effect of metoprolol on activity of beta-adrenoceptor coupled to guanine nucleotide binding regulatory proteins in adriamycin-induced cardiotoxicity

Prevention of cardiotoxicity without interfering with the therapeutic efficacy of adriamycin is a very crucial question. We have investigated the activity of beta-adrenoceptor coupled to guanine nucleotide binding regulatory proteins (G-proteins) and Ca(2+)-ATPase activity in experimental adriamycin-induced cardiotoxicity and the influence of metoprolol treatment on these variables. Adriamycin was administered to rats intravenously as a single dose of 6 mg/kg, and metoprol was continuously given by means of implanted osmotic pumps. beta-Adrenoceptor characteristics were measured by radioligand-binding experiments and by basal and stimulated adenylyl cyclase activity. Northern blot and dot blot analysis was used to quantify G-protein mRNA. It was shown that adriamycin did not induce any change in the total beta-adrenoceptor density, nor did the high affinity agonist binding to beta-adrenoceptor change. Adriamycin did not induce any alteration in the amount of mRNA encoding for stimulatory (Gs) or inhibitory (Gi) G-proteins. Also, basal and stimulated adenylyl cyclase activities were identical in the different experimental groups. In contrast, the Ca(2+)-ATPase was shown to increase in adriamycin-treated rats compared to control rats (45 +/- 3.8 versus 23 +/- 1.2 mumol Pi/mg/h, P less than .01). Metoprolol was shown to normalize this increase (29 +/- 2.1 mumol Pi/mg/h). Thus, it may be concluded that in experimental adriamycin-induced cardiotoxicity, despite Ca(2+)-overloading, the beta-adrenoceptor-G protein-adenylyl cyclase system remains intact. Metoprolol seems to prevent Ca(2+)-overloading independently of the beta-adrenoceptors studied here.