Hemodynamic effects of captopril and isosorbide mononitrate started early in acute myocardial infarction: a randomized placebo-controlled study

Postconditioning with Nitrates Protects Against Myocardial Reperfusion Injury: A New Use for an Old Pharmacological Agent

Early reperfusion remains the key therapy to salvage viable myocardium and must be applied as soon as possible following an acute myocardial infarction (AMI) to attenuate the ischemic insult. However, reperfusion injury may develop following reintroduction of blood and oxygen to vulnerable myocytes, which results in more severe cell death than in the preceding ischemic episode. Ischemic postconditioning (I-PostC) provides a cardioprotective effect in combination with pharmacological agents. Although nitrates have been tested in many experimental and clinical studies of acute AMI to evaluate the cardioprotective effect, few investigations have been focused on nitrates postconditioning in patients undergoing percutaneous coronary intervention (PCI). This review presents the manifestations of myocardial reperfusion injury (RI) and potential mechanisms underlying it, and provides the mechanisms involved in the cardioprotection of I-PostC. We also present a new therapeutic approach to attenuate RI by use of an ‘old’ agent – nitrates – in AMI patients.

Effects of early use of atenolol or captopril on infarct size and ventricular volume: A double-blind comparison in patients with anterior acute myocardial infarction

BACKGROUND

beta-Blockers and ACE inhibitors reduce early mortality when either one is started in the first hours after myocardial infarction (MI). Considering the close correlation between morphological changes and prognosis, we aimed to investigate whether the benefit of both beta-blockers and ACE inhibitors might reside in a similar protective effect on infarct size or ventricular volume.

METHODS AND RESULTS

In a randomized, double-blind comparison between early treatment with captopril or atenolol in 121 patients with acute anterior MI, both drugs showed a similar reduction in mean blood pressure. However, only the atenolol-treated patients showed a significant early reduction in heart rate. Infarct size, obtained from the perfusion defect in resting single photon emission imaging, was higher in captopril-treated patients than in atenolol-treated patients: 29.8+/-12% versus 20.8+/-12% (P:<0.01) by polar map and 28.3+/-13% versus 20.0+/-13% (P:<0.01) by tomography. Changes from baseline to 1 week and to 3 months in ventricular end-diastolic volume, assessed by echocardiography, were as follows: 58+/-14 versus 64+/-19 (P<0.05) and 65+/-21 mL/m(2) (P<0.05), respectively, with captopril, and 58+/-18 versus 64+/-18 (P<0.05) and 69+/-30 mL/m(2) (P<0.05), respectively, with atenolol. Neither group showed significant changes in end-systolic volume. Among patients with perfusion defect >18% (n=51), those treated with atenolol showed a significant increase of end-systolic and end-diastolic ventricular volumes, whereas captopril-treated patients did not.

CONCLUSIONS

Although early treatment with atenolol or captopril results in similar overall short- and medium-term preservation of ventricular function and volumes, in patients with larger infarctions, a beta-blocker alone does not adequately protect myocardium from ventricular dilatation.

A computer model of normal conduction in the human atria

Although considerable progress has been made in understanding the process of wavefront propagation and arrhythmogenesis in human atria, technical concerns and issues of patient safety have limited experimental investigations. The present work describes a finite volume-based computer model of human atrial activation and current flow to complement these studies. Unlike previous representations, the model is three-dimensional, incorporating both the left and right atria and the major muscle bundles of the atria, including the crista terminalis, pectinate muscles, limbus of the fossa ovalis, and Bachmann's bundle. The bundles are represented as anisotropic structures with fiber directions aligned with the bundle axes. Conductivities are assigned to the model to give realistic local conduction velocities within the bundles and bulk tissue. Results from simulations demonstrate the role of the bundles in a normal sinus rhythm and also reveal the patterns of activation in the septum, where experimental mapping has been extremely challenging. To validate the model, the simulated normal activation sequence and conduction velocities at various locations are compared with experimental observations and data. The model is also used to investigate paced activation, and a mechanism of the relative lengthening of left versus right stimulation is presented. Owing to both the realistic geometry and the bundle structures, the model can be used for further analysis of the normal activation sequence and to examine abnormal conduction, including flutter. The full text of this article is available at http://www.circresaha.org.

Effect of ED management on ICU use in acute pulmonary edema

Acute pulmonary edema (APE) is a common Emergency Department (ED) presentation requiring admission to an intensive care unit (ICU). This study was undertaken to examine the effect of ED management on the need for ICU admission in patients with APE. ED records of APE patients were abstracted for patient age, prehospital and ED pharmacological treatment, diagnoses, airway interventions, and ICU length of stay (LOS). Statistical analysis was through multiple regression, logistic regression, chi-square, and ANOVA. One hundred eighty-one patients composed the study group. Pharmacological treatment included nitroglycerin (NTG), 147 patients (81%); morphine sulfate (MS), 88 (49%); loop diuretics (LD), 133 (73%); and captopril sublingual (CSL), 47 (26%). Use of CSL and MS were associated with opposing needs for ICU admission. MS use was associated with increased ICU admissions (odds ratio, 3.08; P = .002), whereas CSL use was associated with decreased ICU admissions (odds ratio, 0.29; P = .002). Morphine sulfate use also demonstrated an increased need for endotracheal intubation (ETI) (odds ratio, 5.04; P = .001), whereas CSL demonstrated a decreased need for ETI (odds ratio, 0.16; P = .008). Ninety-three patients required some form of respiratory support. Forty received noninvasive pressure support ventilation (NPSV) from a bilevel positive airway pressure system (BiPAP), and 60 received endotracheal intubation. Some patients received more than 1 form of respiratory support; all other patients received supplemental oxygen only. The ICU-LOS associated with different airway interventions were supplemental oxygen, 0.72 days; BiPAP, 1.48 days; and ETI, 3.70 days (P < .001). Specific ED pharmacological interventions are associated with a decreased need for ICU admission and endotracheal intubation in acute pulmonary edema patients, whereas use of noninvasive pressure support ventilation correlates with a reduction in the ICU length of stay for patients who do require critical care admission.

Heterogeneous atrial denervation creates substrate for sustained atrial fibrillation

BACKGROUND

Heterogeneous electrophysiological properties, which may be due in part to autonomic innervation, are important in the maintenance of atrial fibrillation (AF). We hypothesized that heterogeneous sympathetic denervation with phenol would create a milieu for sustained AF.

METHODS AND RESULTS

After the determination of baseline inducibility, 15 dogs underwent atrial epicardial phenol application and 11 underwent a sham procedure. After 2 weeks of recovery, the animals had repeat attempts at inducing AF and effective refractory period (ERP) testing. Epicardial maps were obtained to determine local AF cycle lengths. ERPs were determined at baseline and during sympathetic, vagal, and simultaneous vagal/sympathetic stimulation. Dogs then underwent PET imaging with either a sympathetic ([11C]hydroxyephedrine, HED) or parasympathetic (5-[11C]methoxybenzovesamicol, MOBV) nerve label. None of the animals had sustained AF (>60 minutes) at baseline. None of the sham dogs and 14 of 15 phenol dogs had sustained AF at follow-up. Sites to which phenol was applied had a significantly shorter ERP (136+/-17.6 ms) than those same sites in the sham controls (156+/-19.1 ms) (P=0.01). Although there was no difference in the ERP change with either vagal or sympathetic stimulation alone between phenol and nonphenol sites, the percent decrease in ERP with simultaneous vagal/sympathetic stimulation was greater in the phenol sites (17+/-8%) than in the nonphenol sites (9+/-9%) (P=0.01). There was a significantly increased dispersion of refractoriness (21+/-6.4 ms in the sham versus 58+/-14 ms in the phenol dogs, P=0.01) as well as dispersion of AF cycle length (49+/-10 ms in the sham versus 105+/-12 ms in the phenol dogs, P=0.0001). PET images demonstrated defects of HED uptake in the areas of phenol application, with no defect of MOBV uptake.

CONCLUSIONS

Heterogeneous sympathetic atrial denervation with phenol facilitates sustained AF.

Effect of early captopril treatment on blood adrenaline levels in acute myocardial infarction (the substudy of ISIS-4). International Study of Infarct Survival-4

Of patients with acute myocardial infarction eligible for the International Study of Infarct Survival-4, randomized to captopril (n = 30) or placebo (n = 33), the captopril group had a significant decrease in blood adrenaline on day 3 compared with baseline values. Results suggest that suppression of sympathetic activity contributes to the beneficial effects of treatment with angiotensin-converting enzyme inhibitors in the early phase of acute myocardial infarction.

Relationship between local atrial fibrillation interval and refractory period in the isolated canine atrium

BACKGROUND

Atrial refractory periods and their spatial distribution are important determinants of atrial reentrant arrhythmias. The objective of this study was to demonstrate a correlation between the local atrial fibrillation interval (AFI) and local effective refractory period (ERP).

METHODS AND RESULTS

To measure the local ERP and local AFI under stable conditions without hemodynamic, autonomic, or reflex influences, isolated perfused canine whole atria were used (n = 8). The isolated atria were mounted on two endocardial electrodes. Bipolar electrograms were simultaneously recorded from 253 endocardial sites, and 16 to 20 randomly distributed electrodes were used to measure the local ERP by the extrastimulus technique. In all studies, several episodes of AF were induced by a single extrastimulus. The ERP and minimum AFI converged with increasing duration of AF. The convergence was more rapid if the total duration of AF analyzed came from multiple episodes of AF. The correlation coefficient between the local ERP and minimum local AFI was .92 (n = 119, P < .001). The minimum AFI was used to construct AFI distribution maps at all 253 sites. Activation block during premature stimulation correlated with regions of long AFI.

CONCLUSIONS

The minimum local AFI measured from at least 10 seconds of AF approximates the local ERP. Construction of a minimum local AFI map during AF can be used to predict the distribution of refractoriness and can be used to predict sites of functional block. Contrary to studies done in intact animals and patients, the AFI were longer than the ERPs, suggesting that reflex changes may shorten ERP in the intact heart.

Activation and entrainment mapping defines the tricuspid annulus as the anterior barrier in typical atrial flutter

BACKGROUND

The importance of anatomic barriers in the atrial flutter reentry circuit has been well demonstrated in canine models. It has been shown previously that the crista terminalis and its continuation as the eustachian ridge form a posterior barrier. In this study we tested the hypothesis that the tricuspid annulus forms the continuous anterior barrier to the flutter circuit.

METHODS AND RESULTS

Thirteen patients with typical atrial flutter were studied. A 20-pole halo catheter was situated around the tricuspid annulus. A mapping catheter was used for activation and entrainment mapping from seven sequential sites around the tricuspid annulus and from three additional sites including the tip of the right atrial appendage, at the fossa ovalis, and in the distal coronary sinus. Sites were considered to be within the circuit when the postpacing interval minus the flutter cycle length and the stimulus time minus the activation time were < or = 10 ms; sites were considered to be outside the circuit when these intervals were > 10 ms. All seven annular sites were within the circuit; activation occurred sequentially around the annulus and accounted for 100% of the flutter cycle length. The fossa ovalis, the distal coronary sinus, and the right atrial appendage were outside the circuit.

CONCLUSIONS

Closely spaced sites around the tricuspid annulus are activated sequentially, and are all within the flutter circuit according to entrainment criteria. This demonstrates that the tricuspid annulus constitutes a continuous anterior barrier constraining the reentrant wave front of human counterclockwise atrial flutter.

Effect of nitrates on myocardial remodeling after acute myocardial infarction

Nitrates are effective for the therapy of acute coronary syndromes, including acute myocardial infarction. Their application in acute infarction has established that vasodilators are beneficial provided hypotension is avoided. Nitrates limit early ventricular remodeling in infarction. New dosing strategies and formulations that permit chronic use after infarction with less tolerance might limit late remodeling. Over the last decade, the demonstrated effectiveness of angiotensin-converting enzyme (ACE) inhibitors in limiting ventricular dilation postinfarction has generated controversy over the usefulness of nitrates for that indication. The uncertainty has been intensified by 2 large mortality trials that tested both agents as adjuncts to conventional therapy. These trials were not designed to test whether nitrates might limit remodeling. Mechanistic experimental and clinical studies that tested whether nitrates or ACE inhibitors could effectively limit ventricular remodeling showed that both improved remodeling endpoints. However, experimental studies raise some concern about the decrease in infarct collagen associated with ACE inhibition and emphasize the fact that final outcome represents a balance of effects. That nitrates do not decrease infarct collagen could be important. Nitrate-induced early recruitment of ventricular function after late reperfusion of acute infarction might also be important. In the mortality trials, >50% of patients received open-label nitrates as per indication. Thus, the trial results to date do not suggest that nitrates are ineffective for remodeling, but rather that ACE inhibitors can confer added benefit. There has been no large clinical trial to test the efficacy of nitrates for remodeling as there has been for ACE inhibitors.

Role of right atrial endocardial structures as barriers to conduction during human type I atrial flutter. Activation and entrainment mapping guided by intracardiac echocardiography

BACKGROUND

The importance of barriers in atrial flutter has been demonstrated in animals. We used activation and entrainment mapping, guided by intracardiac echocardiography (ICE), to determine whether the crista terminalis (CT) and eustachian ridge (ER) are barriers to conduction during typical atrial flutter in humans.

METHODS AND RESULTS

In eight patients, ICE was used to guide the placement of 20-pole and octapolar catheters along the CT and interatrial septum and a roving catheter to nine sites: just posterior (1) and anterior (2) to the CT along the lateral right atrium, at the fossa ovalis (3), and just posterior and anterior to the ER at the low posterolateral (4 and 5), low posterior (6 and 7), and low posteromedial (8 and 9) right atrium. Entrainment was performed, and each site was considered within the flutter circuit if the postpacing interval-flutter cycle length (PPI-FCL) and the stimulus time-activation time (stim time-act time) were < 10 msec. Split potentials were recorded along the CT with components activated in a low-to-high pattern and a high-to-low pattern. Conduction times, as percentage of FCL, were significantly different at sites on either side of the CT and ER: site 1 (33 +/- 13%) and site 2 (43 +/- 12%) (P = .02), site 4 (48 +/- 24%) and site 5 (75 +/- 8.9%) (P = .02), and site 6 (22 +/- 10%) and site 7 (82 +/- 5.3%) (P = .0009). During entrainment, no surface fusion was observed at sites 5, 7, or 9. The PPI-FCL and stim time-act time were not significantly different than 0 at sites 2, 7, 5, or 9, indicating that they were within the flutter circuit, whereas sites 1, 3, 4, and 6 were not.

CONCLUSIONS

ICE enabled the correlation of functional electrophysiological properties with specific anatomic landmarks, identifying the CT and ER as barriers to conduction during human atrial flutter.

Impact of left ventricular unloading after late reperfusion of canine anterior myocardial infarction on remodeling and function using isosorbide-5-mononitrate

BACKGROUND

Late reperfusion during acute myocardial infarction results in delayed recovery of ventricular function and less remodeling, whereas ventricular unloading with nitrates improves function and attenuates remodeling. Whether late reperfusion combined with prolonged unloading with isosorbide-5-mononitrate (ISMN) might produce greater functional recovery and less remodeling than late reperfusion alone is not known.

METHODS AND RESULTS

In vivo left ventricular function and topography (echocardiograms), postmortem topography (planimetry), and collagen (hydroxyproline) were measured in dogs that were randomized to reperfusion 2 hours after left anterior descending coronary artery ligation, and ISMN (n = 12) or placebo (n = 12) was given as 25 mg IV over 4 hours followed by 50 mg PO QID for 6 weeks. Compared with placebo, the ISMN group had similar heart rate but lower left atrial pressure, mean arterial pressure, and rate-pressure products. Although in vivo baseline remodeling and functional parameters were similar in the two groups, by 6 weeks the ISMN group had smaller (P < or = .05) infarct and noninfarct segment lengths, ventricular volumes, and mass; less (P < .001) asynergy; and greater (P < .001) ejection fraction. More important, by 2 days, ejection fraction was 18% greater (P < .025) and asynergy 26% less (P < .05) with ISMN. At 6 weeks, ISMN showed less (P < or = .05) scar size, scar collagen, cavity dilation, noninfarct wall thickness, and apical bulging than placebo. In another 4 dogs, acute ISMN produced less improvement in function and remodeling than prolonged ISMN.

CONCLUSIONS

Late reperfusion of acute anterior myocardial infarction combined with prolonged ISMN unloading results in greater and earlier recovery of ventricular function and less remodeling than late reperfusion alone.

The risk of atrial fibrillation following radiofrequency catheter ablation of atrial flutter

BACKGROUND

Although radiofrequency catheter ablation of atrial flutter is associated with a high rate of initial success, several clinical issues regarding this therapy remain to be defined. For example, the risks of recurrent atrial flutter and of developing atrial fibrillation after flutter ablation are unknown. In addition, it is not known whether elimination of atrial flutter will modify the natural history of atrial fibrillation in patients who experience both of these arrhythmias. The purpose of the present study was to determine the actuarial freedom from recurrent or new atrial arrhythmias in patients with atrial flutter undergoing catheter ablation.

METHODS AND RESULTS

The study population consisted of 59 consecutive patients (mean age, 61.9 +/- 12.6 years) with typical atrial flutter who underwent catheter ablation of the reentrant circuit. Catheter ablation was not advised for patients in whom paroxysmal atrial fibrillation had been a major clinical problem. The inducibility of atrial fibrillation and atrial flutter was assessed after successful atrial flutter ablation with programmed atrial stimulation and rapid atrial pacing to a cycle length of 180 ms or 2:1 atrial capture. Atrial flutter was successfully ablated and rendered noninducible in 53 of 59 patients (90%). Over a mean follow-up period of 13.2 +/- 6.6 months, atrial flutter recurred in 5 patients (9.4%). Atrial fibrillation occurred in 14 of 53 patients after successful ablation (26.4%). Four clinical variables were associated by univariate analysis with the late occurrence of atrial fibrillation: (1) the presence of structural heart disease, (2) a history of atrial fibrillation before ablation of atrial flutter, (3) inducible sustained atrial fibrillation after ablation, and (4) a greater number of failed antiarrhythmic drugs. By multivariate analysis, only the persistent inducibility of sustained atrial fibrillation predicted the later development of atrial fibrillation.

CONCLUSIONS

Although atrial flutter ablation is highly effective and associated with a low risk of recurrent atrial flutter, atrial fibrillation continues to be a long-term risk for individuals undergoing this procedure. The risk of later atrial fibrillation is especially high for patients in whom sustained atrial fibrillation remains inducible after ablation of atrial flutter.

Nitrates in myocardial infarction: influence on infarct size, reperfusion, and ventricular remodelling

OBJECTIVE

To assess the possible benefits of intravenous isosorbide dinitrate in acute myocardial infarction and oral isosorbide mononitrate in subacute myocardial infarction.

METHODS

316 patients presenting with acute myocardial infarction were entered into double blind placebo controlled clinical trials assessing infarct size by enzyme release, ventricular size and function by echocardiography, reperfusion by continuous 12 lead ST segment monitoring and late potentials by high resolution electrocardiography.

RESULTS

301 patients, of whom 292 (97%) received thrombolytic treatment, were randomised on admission to intravenous isosorbide dinitrate or placebo. Overall, there was no significant effect of treatment on infarct size, ST segment resolution, ventricular remodelling, or late potentials at day 3. A trend was observed towards a reduction in infarct size in patients with non-Q wave infarction treated with isosorbide dinitrate. Heterogeneity of nitrate effect was observed in relation to the degree of ST segment elevation on presentation with a clear benefit of isosorbide dinitrate in patients with moderate ST segment elevation (472 U/l v 704 U/l, P = 0.003) and a trend towards a deleterious effect in patients with marked ST segment elevation (1152 U/l v 1058 U/l, P = 0.2). ST segment re-elevation was more common among patients receiving nitrate treatment than in those assigned to placebo (29 v 16, P < 0.05). Some 160 patients underwent a further randomisation to sustained release isosorbide mononitrate or placebo on day 3. Echocardiographic volumes after 6 weeks of treatment were similar in the two groups.

CONCLUSIONS

No benefit was observed with administration of nitrates in the treatment groups as a whole for either acute or subacute infarction. There was, however, evidence of heterogeneity of effect in the different subgroups of acute infarction, and the possibility that nitrates may have differing actions in different groups of patients should be considered.

Expanding the paradigm of the renin-angiotensin system and angiotensin-converting enzyme inhibitors

The renin-angiotensin system acts systemically and locally to influence vascular tone, blood volume, myocardial contractility, thromboresistance, and tissue responses to injury. ACE inhibitors have assumed a vital role in the treatment of patients with ventricular dysfunction, including those who have sustained one or more myocardial infarctions. The greatest benefits appear over time and not unexpectedly are most pronounced in cases of moderate to severe reduction in left ventricular performance. Emerging evidence suggests that the paradigm for ACE inhibitor use will expand even further, opening new doors for patient care.

Nitrates in myocardial infarction

Until two decades ago nitroglycerin was contraindicated in acute myocardial infarction (MI). Studies in the canine model demonstrated that low-dose intravenous (i.v.) infusion, carefully titrated to decrease mean blood pressure by 10% but not below 80 mmHg, during early stages of acute MI produced marked reduction of left ventricular (LV) preload, improvement in regional perfusion, and limitation of infarct size and remodeling. However, more i.v. nitroglycerin to decrease blood pressure further resulted in a paradoxical J-curve effect, with hypoperfusion and increased infarct size. Clinical studies have confirmed that low-dose i.v. nitroglycerin infusion for the first 48 hours after acute MI is safe, not only for improving performance in LV failure, but also for limiting ischemic injury, infarct size, remodeling, and infarct-related complications, including deaths in-hospital and up to 1 year. Recent studies suggest that more prolonged therapy with nitrates spanning the healing phase of acute anterior Q-wave MI can further limit LV remodeling and preserve function. Preliminary results of the recently completed ISIS-4 megatrial suggest, however, that long-term nitrate in patients with suspected MI in the 1990s does not improve survival significantly.

The new trials: AIRE, ISIS-4, and GISSI-3. Is the dossier on ACE inhibitors and myocardial infarction now complete?

Recent studies have strengthened the arguments for the use of angiotensin-converting enzyme (ACE) inhibitors in the early postinfarct period. Those with clinically detectable heart failure, and hence at highest risk, will benefit most, as shown in the AIRE study, but those at lower risk with left ventricular dysfunction still have some benefit, theoretically through ventricular remodeling. In patients in the very early stages of acute myocardial infarction, three trials have shown discordant results. In CONSENSUS-II, intravenous enalaprilat followed by oral enalapril gave no benefit, rather causing excess hypotension and a possible increase in mortality. In ISIS-4 and GISSI-3, mortality improved by 0.46% and 0.8%, respectively, with risk reductions of 9% and 11%. Added transdermal nitrate in GISSI-3 gave a total reduction of 17%. In view of the risk of hypotension (20% in ISIS-4, compared with placebo 10%), very early ACE inhibition will probably only be used for selected patients. Logically, one target group would be those seen 7-24 hours after the onset of symptoms, particularly 7-12 hours, at which time captopril alone gave a reduction of 14.5% in risk. These mortality differences compare favorably with those recently found when comparing tPA and streptokinase in the GUSTO study.

Effect of prolonged nitrate therapy on left ventricular remodeling after canine acute myocardial infarction

BACKGROUND

Prolonged nitrate therapy during healing between 2 days and 6 weeks after anterior myocardial infarction has the potential for limiting further left ventricular remodeling (or changes in topography) and preserving function. Longterm therapy throughout healing over 6 weeks might be more beneficial than short-term therapy over the first 2 weeks after infarction.

METHODS AND RESULTS

The effect of prolonged nitrate therapy between 2 days and 6 weeks during healing after infarction on serial parameters of ventricular remodeling (scar expansion, scar thinning, ventricular dilation, and hypertrophy) and function (asynergy or akinesis plus dyskinesis and ejection fraction) by serial two-dimensional echocardiography, hemodynamics, postmortem topography (computerized planimetry, geometric maps, and radiographs), and collagen content (hydroxyproline) was studied in 64 instrumented dogs randomized 2 days after left anterior descending coronary artery ligation to various nitrate regimens (n = 32) over the first 2 weeks (subgroup 1: 2% transdermal nitroglycerin at 8 AM and 4 PM, n = 6; subgroup 2: 2% transdermal nitroglycerin plus 2.6 mg of sustained-release oral nitroglycerin at 8 AM, 3 PM, and 10 PM, n = 5; subgroup 3: oral isosorbide dinitrate, 30 mg at 8 AM and 4 PM, n = 11) or 6 weeks (subgroup 4: isosorbide dinitrate, n = 10) and in matching controls (n = 32). Nitrate therapy reduced left atrial pressure, mean arterial pressure, and the rate-pressure product compared with controls over the 6 weeks. Postmortem scar mass and hydroxyproline were similar in control and nitrate groups. However, scar stretching and thinning, cavity dilation, noninfarct wall hypertrophy, and apical bulging were less with nitrates, especially in the long-term subgroup 4. In vivo remodeling parameters between 2 days and 6 weeks after ligation showed that, compared with controls, nitrate therapy prevented further stretching of the asynergic segment, decreased the expansion index, decreased further scar thinning, prevented the increase in ventricular volumes, reduced the frequency of ventricular aneurysm, prevented the increase in ventricular mass, reduced the extent of asynergy, and improved ejection fraction. Although the beneficial effect on topography and function was seen in all nitrate subgroups, the overall benefit was greater with long-term therapy over 6 weeks (subgroup 4) than short-term therapy confined to the first 2 weeks (subgroups 1, 2, and 3).

CONCLUSIONS

Prolonged nitrate therapy, in various regimens during healing after infarction, effectively reduced left ventricular loading and prevented infarct thinning, further infarct expansion, progressive ventricular dilation, and the increase in mass. These effects were associated with decreased asynergy and improved ejection fraction. The beneficial effects were greater with long-term therapy over 6 weeks than short-term therapy over the first 2 weeks.

Does captopril treatment before thrombolysis in acute myocardial infarction attenuate reperfusion damage? Short-term and long-term effects

Several experimental studies carried out on animals and on isolated heart preparations show that captopril can reduce post-ischemic reperfusion injury. Our study was aimed at investigating the effects of captopril before thrombolysis in acute myocardial infarction (AMI) and included 259 patients, hospitalized within 4 h of the onset of symptoms. Patients were randomly subdivided into two groups: the first group (131 patients, Group A, pretreatment) received 6.25 mg captopril orally about 15 min before i.v. administration of urokinase (2 million), the second group (128 patients, Group B, late-treatment), received captopril about 3 days after thrombolytic treatment. Captopril doses were later increased in both groups according to blood pressure. All patients were subdivided according to the localization of infarction. Anterior AMI was shown by 166 patients (84 from Group A and 82 from Group B); 93 patients showed inferior AMI (47 from Group A and 46 from Group B). Ventricular hyperkinetic arrhythmias (VHAs) due to reperfusion were evaluated during the first 2 h. VHAs occurred in 11.9% of patients with anterior AMI in Group A vs. 37.8% in Group B (P < 0.001). CK peak normalization time in the group with anterior AMI was achieved after 58 +/- 2 h in Group A vs. 71 +/- 2 h in Group B (P < 0.001). CK peak was 1719 +/- 152 in Group A vs. 2184 +/- 164 U/l in Group B, (P < 0.039). Late arrhythmias, higher than Lown's Class 2 were found to occur in 15.4% of patients with anterior AMI of Group A vs. 31.7% in Group B (P < 0.022), at predischarge Holter test.(ABSTRACT TRUNCATED AT 250 WORDS)