Spontaneous reperfusion enhances succinate concentration in peripheral blood from stemi patients but its levels does not correlate with myocardial infarct size or area at risk

Succinate is enhanced during initial reperfusion in blood from the coronary sinus in ST-segment elevation myocardial infarction (STEMI) patients and in pigs submitted to transient coronary occlusion. Succinate levels might have a prognostic value, as they may correlate with edema volume or myocardial infarct size. However, blood from the coronary sinus is not routinely obtained in the CathLab. As succinate might be also increased in peripheral blood, we aimed to investigate whether peripheral plasma concentrations of succinate and other metabolites obtained during coronary revascularization correlate with edema volume or infarct size in STEMI patients. Plasma samples were obtained from peripheral blood within the first 10 min of revascularization in 102 STEMI patients included in the COMBAT-MI trial (initial TIMI 1) and from 9 additional patients with restituted coronary blood flow (TIMI 2). Metabolite concentrations were analyzed by ¹H-NMR. Succinate concentration averaged 0.069 ± 0.0073 mmol/L in patients with TIMI flow ≤ 1 and was significantly increased in those with TIMI 2 at admission (0.141 ± 0.058 mmol/L, p < 0.05). However, regression analysis did not detect any significant correlation between most metabolite concentrations and infarct size, extent of edema or other cardiac magnetic resonance (CMR) variables. In conclusion, spontaneous reperfusion in TIMI 2 patients associates with enhanced succinate levels in peripheral blood, suggesting that succinate release increases overtime following reperfusion. However, early plasma levels of succinate and other metabolites obtained from peripheral blood does not correlate with the degree of irreversible injury or area at risk in STEMI patients, and cannot be considered as predictors of CMR variables.Trial registration: Registered at www.clinicaltrials.gov (NCT02404376) on 31/03/2015. EudraCT number: 2015-001000-58.

Sex bias in admission to tertiary-care centres for acute myocardial infarction and cardiogenic shock

BACKGROUND

There are limited data on sex-specific outcomes and management of cardiogenic shock complicating ST-segment elevation myocardial infarction (CS-STEMI). We investigated whether any sex bias exists in the admission to revascularization capable hospitals (RCH) or intensive cardiac care units (ICCU) and its impact on in-hospital mortality.

METHODS

We used the Spanish National Health System Minimum Basic Data from 2003 to 2015 to identify patients with CS-STEMI. The primary outcome was sex differences in in-hospital mortality.

RESULTS

Among 340 490 STEMI patients, 20 262 (6%) had CS and 29.2% were female. CS incidence was higher in women than in men (7.9% vs 5.1%, P = .001). Women were older and had more hypertension and diabetes, and were less often admitted to RCH than men (from 58.7% in 2003 to 79.6% in 2015; and from 61.9% in 2003 to 85.3% in 2015; respectively, P = .01), and to ICCU centres (25.7% vs 29.2%, P = .001). Adjusted mortality was higher in women than men over time (from 79.5 ± 4.3% to 65.8 ± 6.5%; and from 67.8 ± 6% to 58.1 ± 6.5%; respectively, P < .001). ICCU availability was associated with higher use of Percutaneous coronary intervention (PCI) in women (46.8% to 67.2%; P < .001) but was even higher in men (54.8% to 77.4%; P < .001). In ICCU centres, adjusted mortality rates decreased in both sexes, but lower in women (from 74.9 ± 5.4% to 66.3 ± 6.6%) than in men (from 67.8 ± 6.0% to 58.1 ± 6.5%, P < .001). Female sex was an independent predictor of mortality (OR 1.18 95% CI 1.10-1.27, P < .001).

CONCLUSIONS

Women with CS-STEMI were less referred to tertiary-care centres and had a higher adjusted in-hospital mortality than men.

Invasive Versus Conservative Strategy in Frail Patients With NSTEMI: The MOSCA-FRAIL Clinical Trial Study Design

INTRODUCTION AND OBJECTIVES

Although clinical guidelines recommend invasive management in non-ST-segment elevation myocardial infarction (NSTEMI), this strategy is underused in frail elderly patients in the real world. Furthermore, these patients are underrepresented in clinical trials and therefore the evidence is scarce. Our hypothesis is that an invasive strategy will improve prognosis in elderly frail patients with NSTEMI.

METHODS

This will be a prospective, multicenter, randomized trial, in which the conservative and invasive strategies will be compared in patients meeting all of the following inclusion criteria: NSTEMI diagnosis, age ≥ 70 years, and frailty defined by a category ≥ 4 in the Clinical Frailty Scale. Participants will be randomized to an invasive (coronary angiogram and revascularization if anatomically amenable) or conservative (medical treatment and coronary angiogram only if persistent clinical instability) strategy. The primary endpoint will be the number of days alive out of hospital during the first year. The coprimary endpoint will be the time until the first cardiac event (cardiac death, reinfarction or postdischarge revascularization). We estimate a sample size of 178 patients (89 per arm), considering an increase of 20% in the proportion of days alive out of hospital with the invasive management.

RESULTS

The results of this study will add important knowledge to inform the management of frail elderly patients hospitalized with NSTEMI.

CONCLUSIONS

We hypothesize that the invasive strategy will improve outcomes in frail elderly patients with NSTEMI. If this is confirmed, frailty status should not dissuade physicians from implementing an invasive management strategy.

CLINICAL TRIAL REGISTRATION

URL: http://www.clinicaltrials.gov.Identifier: NCT03208153.

Randomized comparison between the invasive and conservative strategies in comorbid elderly patients with non-ST elevation myocardial infarction

BACKGROUND

Comorbid elderly patients with non-ST-elevation myocardial infarction (non-STEMI) are underrepresented in randomized trials and undergo fewer cardiac catheterizations according to registries. Our aim was to compare the conservative and invasive strategies in these patients.

METHODS

Randomized multicenter study, including 106 patients (January 2012-March 2014) with non-STEMI, over 70years and with comorbidities defined by at least two of the following: peripheral artery disease, cerebral vascular disease, dementia, chronic pulmonary disease, chronic renal failure or anemia. Patients were randomized to invasive (routine coronary angiogram, n=52) or conservative (coronary angiogram only if recurrent ischemia or heart failure, n=54) strategy. Medical treatment was identical. The main endpoint was the composite of all-cause mortality, reinfarction and readmission for cardiac cause (postdischarge revascularization or heart failure), at long-term (2.5-year follow-up). Analysis of cumulative event rate (incidence rate ratio=IRR) and time to first event (hazard ratio=HR), were performed.

RESULTS

Cardiac catheterization/revascularization rates were 100%/58% in the invasive versus 20%/9% in the conservative arm. There were no differences between groups in the main endpoint (invasive vs conservative: IRR=0.946, 95% CI 0.466-1.918, p=0.877) at long-term. The invasive strategy, however, tended to improve 3-month outcomes in terms of mortality (HR=0.348, 95% CI 0.122-0.991, p=0.048), and of mortality or ischemic events (reinfarction or postdischarge revascularization) (HR=0.432, 95% CI 0.190-0.984, p=0.046). This benefit declined during follow-up.

CONCLUSIONS

Invasive management did not modify long-term outcome in comorbid elderly patients with non-STEMI. The finding of a tendency towards an improvement in the short-term needs confirmation in larger studies (clinicaltrials.govNCT1645943).

Platelet deposition in remote cardiac regions after coronary occlusion

BACKGROUND

Activated platelets might contribute to endothelial dysfunction in non-ischaemic territories during acute myocardial infarction. We assessed platelet deposition, coronary flow reserve and contractile function in remote cardiac regions after transient coronary occlusion and their association with systemic platelet activation.

MATERIALS AND METHODS

In 10 pigs (series A) subjected to 48-min occlusion of the left anterior descending coronary artery (LAD), 99mTc-platelet content in the right coronary artery (RCA) and its dependent myocardium was counted after reflow. In 10 pigs (series B) receiving the same occlusion of the RCA, the hyperaemic response at the LAD and systolic shortening in LAD-dependent myocardium were monitored after reperfusion. P-selectin expression on circulating platelets was assessed in both series by flow cytometry.

RESULTS

In series A, platelet counts in the RCA and non-ischaemic myocardium were correlated with platelet content, polymorphonuclear leukocyte infiltration and infarct size in the reperfused zone, as well as with the percentage of P-selectin-positive platelets after reflow. In series B, a transient reduction in peak hyperaemic response in the LAD and sustained contractile dysfunction in non-ischemic myocardium were observed after releasing the RCA occlusion, these changes being also correlated with platelet activation status.

CONCLUSIONS

Ischaemic injury triggers macro- and microvascular platelet deposition and causes an impairment in coronary flow reserve and contractile function in distant regions of the heart, which are related to activation of circulating platelets.

Pre-treatment with the Na+/H+ exchange inhibitor cariporide delays cell-to-cell electrical uncoupling during myocardial ischemia

OBJECTIVE

Inhibition of Na(+)-H(+) exchange (NHE) delays the onset of myocardial rigor contracture during ischemia. The aim of this study was to analyse the effects of NHE inhibition on cell-to-cell electrical uncoupling during myocardial ischemia/reperfusion.

METHODS

Twenty-six isolated rat hearts and 23 in situ porcine hearts were submitted to no-flow ischemia followed by reperfusion, with or without pre-treatment with cariporide (7 microM in rats and 3 mg/kg in pigs). Ischemic rigor and hypercontracture, conduction velocity and myocardial electrical impedance were monitored.

RESULTS

Pre-treatment with cariporide delayed ATP depletion (luminescence assay in rat myocardium) and onset of rigor contracture (tension recordings or ultrasonic crystals) during ischemia both in rat and pig hearts (P<0.05). In addition, cariporide delayed the onset of sharp changes in tissue resistivity and phase angle in impedance recordings (four-electrode probes) from 10+/-1 to 13+/-1 min (P<0.001) in rat hearts, and from 22+/-1 to 38+/-2 min (P<0.001) in pigs. Blockade of impulse propagation (transmembrane action potentials in rat hearts) was also markedly delayed by cariporide (from 14+/-1 to 20+/-1 min, P<0.001). Reperfusion-induced LDH release in rat hearts and infarct size in pigs were markedly reduced by pre-treatment with cariporide.

CONCLUSIONS

Inhibition of NHE with cariporide slows the progression of ischemic injury during myocardial ischemia, and delays the onset of cell-to-cell electrical uncoupling.

Intravenous administration of the natriuretic peptide urodilatin at low doses during coronary reperfusion limits infarct size in anesthetized pigs

OBJECTIVE

It has been shown that cGMP content is reduced in post-ischemic myocardium, and that stimulation of cGMP synthesis prevents cardiomyocyte hypercontracture and cell death in vitro. This study was aimed at determining whether administration of the natriuretic peptide urodilatin (URO) at the time of reperfusion could limit myocardial cell death secondary to transient coronary occlusion.

METHODS

The relation between cGMP content in reperfused myocardium and the extent of cell death was investigated in isolated rat hearts (n=62) receiving different URO concentrations during initial reperfusion. The dose of intravenous URO necessary to obtain the targeted increase in cGMP in reperfused myocardium was investigated in ten pigs submitted to transient coronary occlusion (CO), and the effect of two selected doses of URO on infarct size was investigated in 22 pigs.

RESULTS

cGMP was severely reduced in post-ischemic rat hearts. Addition of 0.01 microM URO during the first 15 min of reperfusion had no effect on myocardial cGMP content, functional recovery or LDH release in hearts submitted to 40 or 60 min of ischemia. At 0.05 microM, URO increased myocardial cGMP to 111% of values in normoxic hearts, improved functional recovery (P=0.01) and reduced peak LDH released by 40% (P=0.02). The beneficial effect of urodilatin was abolished by ANP receptor inhibition. At 1 microM, URO increased cGMP in reperfused myocardium to 363% of normoxic controls and had no beneficial effect. In pigs allocated to 47 min of CO and 5 min of reperfusion, cGMP was markedly reduced in reperfused myocardium. Intravenous URO at 10 ng/kg per min during the first 25 min of reperfusion normalized myocardial cGMP after 5 min of reflow (95% of control myocardium), and reduced infarct size by 40% (P=0.04). At 50 ng/kg per min, urodilatin increased myocardial cGMP in reperfused myocardium to 335% of control myocardium and failed to significantly reduce infarct size (46 vs. 66%, P=0.125). None of these doses had detectable hemodynamic effects.

CONCLUSIONS

Intravenous low-dose URO at the time of reperfusion normalizes myocardial cGMP and limits necrosis. Large doses of URO increasing myocardial cGMP well over normal values may lack this beneficial effect.

Q-wave evolution of a first acute myocardial infarction without significant ST segment elevation

BACKGROUND

Some patients with acute myocardial infarction presenting without significant ST segment elevation develop a Q-wave infarction. It is unclear whether these patients can be identified from the admission electrocardiogram (ECG) and whether they differ in their in-hospital prognosis from those who retain a non-Q-wave myocardial infarction.

METHODS

In 432 consecutive patients admitted to our centre with a first acute myocardial infarction without Q waves and with ST segment amplitudes < or =0.1 mV on admission, we assessed the frequency, the electrocardiographic predictors and the short-term implications of a Q-wave evolution.

RESULTS

In 94 patients (22%), a Q-wave myocardial infarction evolved before hospital discharge (14 anterior, 26 inferior, six lateral, and 48 posterior). Minor anterior ST segment elevation was 36% sensitive and 95% specific in predicting anterior Q waves; minor inferior ST segment elevation, 42% and 89%, respectively, for inferior Q waves; and a maximal ST segment depression > or =0.2 mV in leads V2-V3 with upright T waves and without remote ST segment depression, 38% and 97%, respectively, for posterior R waves. Although patients with a Q-wave evolution had a greater creatinkinase MB peak than those retaining a non-Q-wave pattern (191+/-113 vs. 105+/-77 IU/l, respectively, P<0.001), they experienced a benign in-hospital course, with similar risk of severe complications after adjustment for the baseline clinical predictors than non-Q-wave patients.

CONCLUSIONS

About one fifth of patients with a first acute myocardial infarction without a significant ST segment elevation develop a Q-wave infarction and the admission ECG can help identify them. This evolution, however, is not associated with a worse in-hospital outcome.

Dynamic intracoronary thrombosis does not cause significant downstream platelet embolization

OBJECTIVE

A mural intracoronary thrombus is a potential source of platelet emboli that may obstruct downstream microvessels, but this phenomenon has not been characterized. The present study aimed to assess the magnitude of myocardial platelet accumulation downstream of a mural intracoronary thrombus and its modification by a concomitant transient coronary occlusion (OC) or by treatment with aspirin.

METHODS

The myocardial content of 99mTc-labelled platelets was analyzed in 26 pigs submitted to intimal injury of the left anterior descending coronary artery (LAD) followed by no intervention (n=6), 25-min OC (n=6), or 48-min OC preceded (n=8) or not (n=6) by intravenous administration of 250 mg aspirin.

RESULTS

After 2 h, 24 animals had had 12+/-1 cyclic flow reductions (CFRs) reflecting dynamic LAD thrombosis. Myocardial platelet content in the inferior region was similar among groups. Platelet content in the LAD region was not significantly different to that in the inferior region (129+/-19%, P=NS) in the no intervention group, but was increased following OC (172+/-20 and 312+/-71% after 25- and 48-min OC, respectively, P<0.05). Pre-treatment with aspirin lessened the number of CFRs but did not reduce platelet accumulation in LAD myocardium (483+/-148%). Myocardial platelet accumulation was not associated with the magnitude of platelet deposition in the LAD nor with the number of CFRs, but was correlated with myeloperoxidase activity (r=0.91, P<0.001) and with infarct size (r=0.52, P=0.05). Histological analysis frequently showed sparse platelets or small platelet or leukoplatelet aggregates in small vessels, but arteriolar emboli were rare. In none of seven additional experiments coronary angiography showed obstructions of arterial branches during CFRs.

CONCLUSION

The magnitude of platelet embolization from a mural intracoronary thrombus into downstream myocardium is small despite the presence of repetitive CFRs.

Prognostic significance of ST segment depression in lateral leads I, aVL, V5 and V6 on the admission electrocardiogram in patients with a first acute myocardial infarction without ST segment elevation

OBJECTIVES

We sought to investigate the short-term prognostic value of the admission electrocardiogram (ECG) in patients with a first acute myocardial infarction (MI) without ST segment elevation.

BACKGROUND

ST segment depression on hospital admission predicts a worse outcome in patients with a first acute MI, but the prognostic information provided by the location of ST segment depression remains unclear.

METHODS

In 432 patients with a first acute MI without Q waves or > or = 0.1 mV of ST segment elevation, we evaluated the ability of the initial ECG to predict in-hospital death.

RESULTS

The presence, magnitude and extent of ST segment depression were associated with an increased mortality, but the only electrocardiographic variable that was significant in predicting death after adjusting for baseline predictors was ST segment depression in two or more lateral (I, aVL, V5, or V6) leads (odds ratio 3.5, 95% confidence interval 1.2 to 10.6). Patients with lateral ST segment depression (n = 91, 21%) had higher rates of death (14.3% vs. 2.6%, p < 0.001), severe heart failure (14.3% vs. 4.1%, p < 0.001) and angina with electrocardiographic changes (20.0% vs. 11.6%, p = 0.04) than did the remaining patients, even though they had similar peak creatine kinase, MB fraction levels (129 +/- 96 vs. 122 +/- 92 IU/liter, p = NS). In contrast, ST segment depression not involving the lateral leads did not predict a poor outcome. Among patients who were catheterized, those with lateral ST segment depression had a lower left ventricular ejection fraction (57 +/- 12% vs. 66 +/- 13%, p = 0.001) and more frequent left main coronary artery or three-vessel disease than did the remaining patients (60% vs. 22%, p < 0.001).

CONCLUSIONS

In patients with a first non-ST segment elevation acute MI, ST segment depression in the lateral leads on hospital admission predicts a poor in-hospital outcome.

L-Arginine administration prevents reperfusion-induced cardiomyocyte hypercontracture and reduces infarct size in the pig

OBJECTIVE

Stimulation of cGMP synthesis protects cardiomyocytes against reoxygenation-induced hypercontracture. The purpose of this study was to determine whether L-arginine supplementation has a protective effect against reperfusion-induced hypercontracture and necrosis in the intact animal.

METHODS

Twenty-four Large-White pigs were randomized to receive either 100 mg/kg of L-arginine i.v. or vehicle 10 min before 48 min of coronary occlusion and 2 h of reperfusion. Hemodynamic variables, coronary blood flow and myocardial segment length changes (piezoelectric crystals) were monitored. Postmortem studies included quantification of myocardium at risk (in vivo fluorescein), infarct size (triphenyltetrazolium reaction), myocardial myeloperoxidase activity and histological analysis. Systemic, coronary vein, and myocardial cGMP concentration were measured in additional animals.

RESULTS

Administration of L-arginine had no significant effect in hemodynamics or coronary blood flow. During reperfusion, myocardial cGMP content was reduced in the LAD as compared to control myocardium (P=0.02). L-Arginine increased myocardial cGMP content and caused a transient increase in plasma cGMP concentration during the initial minutes of reperfusion (P=0.02). The reduction in end-diastolic segment length induced by reperfusion, reflecting hypercontracture, was less pronounced in the L-arginine group (P=0.02). Infarct size was smaller in pigs receiving L-arginine (47.9+/-7.2% of the area at risk) than in controls (62.9+/-4.9%, P=0.047). There were no differences between groups in leukocyte accumulation in reperfused myocardium (P=0.80).

CONCLUSION

L-Arginine supplementation reduces myocardial necrosis secondary to in situ ischemia-reperfusion by a direct protective effect against myocyte hypercontracture.

Regional expansion during myocardial ischemia predicts ventricular fibrillation and coronary reocclusion

Primary ventricular fibrillation (VF) complicating acute myocardial infarction is associated with occluded infarction-related arteries. The relationship between VF during ischemia and spontaneous coronary reocclusion was analyzed in 48 anesthetized pigs submitted to 48 min of coronary ligation and 6 h of reflow. Reocclusion was associated with ischemic VF (6 of 11 animals with VF but only 6 of 37 without it had reocclusion) but not with reperfusion arrhythmias, the size of the ischemic area, the magnitude of electrocardiogram changes or contractile dysfunction during ischemia, or the severity of intimal injury at the occlusion site. The increase in end-diastolic length in the ischemic region during coronary occlusion was associated with ischemic VF (15 min after occlusion, end-diastolic length was 116 +/- 2 and 111 +/- 1% of baseline in animals with or without presenting subsequent VF, respectively) and was retained by multiple logistic regression analysis as the only independent predictor of ischemic VF and reocclusion. Thus ischemic VF is strongly associated with an increased rate of spontaneous coronary reocclusion during subsequent reperfusion. Acute expansion of ischemic myocardium appears as a prominent determinant of both ischemic VF and reocclusion.

Gap junction uncoupler heptanol prevents cell-to-cell progression of hypercontracture and limits necrosis during myocardial reperfusion

BACKGROUND

The objective of this study was to test the hypothesis that chemical interaction through gap junctions may result in cell-to-cell progression of hypercontracture and that this phenomenon contributes to the final extent of reperfused infarcts.

METHODS AND RESULTS

Cell-to-cell transmission of hypercontracture was studied in pairs of freshly isolated adult rat cardiomyocytes. Hypercontracture induced by microinjection of a solution containing 1 mmol/L Ca2+ and 2% lucifer yellow (LY) was transmitted to the adjacent cell (11 of 11 pairs), and the gap junction uncoupler heptanol (2 mmol/L) prevented transmission in 6 of 8 pairs (P=.003), with a perfect association between passage of the LY and transmission of hypercontracture. In the isolated, perfused rat heart submitted to 30 minutes of hypoxia, addition of heptanol to the perfusion media during the first 15 minutes of reoxygenation had a dose-related protective effect against the oxygen paradox, as demonstrated by a reduction of diastolic pressure and marked recovery of developed pressure (P<.001), as well as less lactate dehydrogenase release during reoxygenation (P<.001) and less contraction band necrosis (P<.001) than controls. In the in situ pig heart submitted to 48 minutes of coronary occlusion, the intracoronary infusion of heptanol during the first 15 minutes of reperfusion at a final concentration of 1 mmol/L limited myocardial shrinkage, reflecting hypercontracture (P<.05), reduced infarct size after 5 hours of reperfusion by 54% (P=.04), and modified infarct geometry with a characteristic fragmentation of the area of necrosis. Heptanol at 1 mmol/L had no significant effect on contractility of nonischemic myocardium.

CONCLUSIONS

These results demonstrate that hypercontracture may be transmitted to adjacent myocytes through gap junctions and that heptanol may interfere with this transmission and reduce the final extent of myocardial necrosis during reoxygenation or reperfusion. These findings are consistent with the hypothesis tested and open a new approach to limitation of infarct size by pharmacological control of gap junction conductance.

Prevention of ischemic rigor contracture during coronary occlusion by inhibition of Na(+)-H+ exchange

OBJECTIVE

To determine the effect of Na(+)-H+ exchange blockade on ischemic rigor contracture and reperfusion-induced hypercontracture.

METHODS

Thirty-six pigs were submitted to 55 min of coronary occlusion and 5 h reperfusion. Myocardial segment length analysis with ultrasonic microcrystals was used to detect ischemic rigor (reduction in passive segment length change) and hypercontracture (reduction in end-diastolic length).

RESULTS

Pretreatment with the new, highly selective Na(+)-H+ exchange inhibitor HOE642 before occlusion reduced ischemic rigor (P < 0.05), attenuated segment shrinkage (P < 0.05) during subsequent reperfusion, dramatically reduced infarct size (P < 0.0001) and attenuated arrhythmias (P < 0.01). Inhibition of Na(+)-H+ exchange only during reperfusion by means of direct intracoronary infusion of HOE642 into the area at risk prevented reperfusion arrhythmias but had no effect on final infarct size, while treatment with intravenous HOE642 immediately before reperfusion had no detectable effects.

CONCLUSION

These results indicate that inhibition of Na(+)-H+ exchange during ischemia is necessary to limit myocardial necrosis secondary to transient coronary occlusion, and that this action could by mediated by a protective effect against ischemic contracture. Inhibition of Na(+)-H+ exchange only during reperfusion has a partial and transient beneficial effect, but only when the inhibitor reaches the area at risk before reflow.

[Should individuals without evidence of coronary disease and with risk factors receive continuous treatment with aspirin? Arguments in favor]

There is general agreement on the efficacy of aspirin treatment in patients with coronary heart disease, but the indications of aspirin in individuals without coronary heart disease are debated. This paper analyses data from the main studies which investigated the usefulness of aspirin in the primary prevention of coronary heart disease. Particular attention is paid to the risks and benefits of aspirin treatment in different clinically relevant subgroups of patients. It is concluded that, according to available information, the use of aspirin must be integrated in a global strategy for the primary prevention of coronary heart disease and should be probable recommended in males older than 50 years old presenting a higher risk of coronary heart disease (due to the number and intensity of risk factors) and low risk of adverse effects.

Intimal injury in a transiently occluded coronary artery increases myocardial necrosis. Effect of aspirin

This study tested the hypothesis that intimal injury in a transiently occluded coronary artery limits myocardial salvage. The effect of intimal injury on reactive hyperaemia was investigated in 17 pigs submitted to a 30-min occlusion of the left anterior descending coronary artery (LAD), not resulting in myocardial infarction. Catheter-induced intimal damage increased local platelet deposition (99mTc) and reduced hyperaemia, but did not modify myocardial platelet or polymorphonuclear leucocyte content (myeloperoxidase activity) after 6 h reperfusion. To investigate the influence of intimal injury on the extent of myocardial necrosis secondary to a more prolonged coronary occlusion, and the role of platelets on this influence, 52 pigs were submitted to a double randomization (2x2 factorial design) to 250 mg i.v. aspirin vs. placebo and to coronary intimal injury vs. no coronary damage before a 48-min occlusion of the LAD and 6 h of reperfusion. After excluding 12 animals with reocclusion, coronary intimal injury was associated with larger infarcts (triphenyltetrazolium reaction) in animals receiving placebo (36.2+/-7.0% of the area at risk in animals with intimal injury vs. 10.8+/-3.9% in animals without coronary injury, P=0.006) but not in those receiving aspirin (20.3+/-6.5 vs. 21.7+/-6.5% of the area at risk in animals with and without intimal injury respectively). These results suggest that coronary intimal injury in the reperfused artery may have adverse effects on myocardial salvage by mechanisms other than reocclusion or embolization of platelet aggregates.

Myocardial segment shrinkage during coronary reperfusion in situ. Relation to hypercontracture and myocardial necrosis

We have investigated the changes in myocardial segment length induced by reperfusion, and their relation to myocyte hypercontracture and contraction band necrosis. Regional wall function was monitored by ultrasonic gauges in 39 pigs submitted to 48-min occlusion of the left anterior descending coronary artery (LAD) and 6h of reperfusion. Infarct size (triphenyltetrazolium reaction), the extent of contraction band necrosis (quantitative histology) and myocardial water content (desiccation) were measured. Reperfusion induced a marked reduction in end-diastolic length of the LAD segment in all animals, maximal within 15 min after reflow. After 30 min of reperfusion, end-diastolic length of the LAD segment remained below the basal value in 15 animals. The 15 animals that showed shrinkage of the reperfused segment did not differ from the remaining animals in heart rate, aortic pressure, or control segment variables, but had larger infarcts (mean +/- SEM: 32.1 +/- 5.4 vs 12.1 +/- 3.2% of the area at risk, P = 0.003). There was an inverse correlation between end-diastolic length of the LAD segment after 30 min of reperfusion and infarct percentage (r = -0.72) or the extent of contraction band necrosis (r = -0.71). End-diastolic length reduction was more pronounced in larger infarcts despite a more severe myocardial oedema. Neither systolic shortening of the LAD segment nor end-diastolic length or systolic shortening of the control segment, or haemodynamic variables after 30 min of reperfusion correlated to infarct percentage or to the extent of contraction band necrosis. It is concluded that myocardial segment shrinkage during reperfusion reflects myocyte hypercontracture leading to contraction band necrosis.

Effect of osmotic stress on sarcolemmal integrity of isolated cardiomyocytes following transient metabolic inhibition

OBJECTIVE

Exposure to hypotonic medium induces sarcolemmal rupture in metabolically inhibited cardiomyocytes. This study investigated the effect of osmotic stress applied during reoxygenation and the possible cooperation between cell swelling and hypercontracture to produce sarcolemmal disruption.

METHODS

Freshly isolated adult rat myocytes were submitted to 60 min of metabolic inhibition (NaCN 2 mM). Reoxygenation was simulated by changing to one of 3 inhibitor free buffers: (1) normo-osmotic (312 mOsm); (2) hypo-osmotic (80 mOsm); (3) low Na+ normo-osmotic (312 mOsm). The contribution of hypercontracture-induced reoxygenation on sarcolemmal rupture was investigated in myocytes submitted to hypo-osmotic reoxygenation in presence of 2,3-butanedione monoxime 30 mM, a blocker of contractility. Recovery from mechanical fragility was studied by exposing cells to hypotonic buffer 20 or 40 min after restoration of metabolic activity, in either presence or absence of 2,3-butanedione monoxime. Two control groups without metabolic inhibition were used. One was exposed to osmotic stress after 60 min incubation in control conditions, the other was induced to hypercontract by exposure to hypo-osmotic, high-calcium buffer. Cell viability was assessed by the Trypan blue test.

RESULTS

Before any intervention 81.9(1.2)% of cells were rod-shaped. After 60 min of metabolic inhibition most cells developed rigor contracture and only 16.4(1.8)% remained rod-shaped. Restoration of metabolic activity induced hypercontracture of most cells with rigor independently of buffer osmolality. Cell viability, however, significantly differed among groups: only 25.9(4.4)% of cells reoxygenated with hypo-osmotic buffer were viable vs. 74.1(7.6)% in the normo-osmotic reoxygenation group, and 82.9(2.9)% in the control group. Addition of 2,3-butanedione monoxime 30 mM during hypo-osmotic reoxygenation prevented hypercontracture and preserved cell viability. Delaying osmotic stress 20 or 40 min after the onset of reoxygenation did not improve viability [19.3(3.9) and 34.9(1.3)%, respectively]. Contractile blockade with 2,3-butanedione monoxime during the first 20 or 40 min of reoxygenation was associated with a reduction in the number of hypercontracted cells after the removal of the inhibitor but did not increase the proportion of hypercontracted viable cells (25% and 27%, respectively).

CONCLUSIONS

(1) Osmotic stress following transient metabolic inhibition produces sarcolemmal disruption, and this effect is not related to the low Na+ concentration present in the hypo-osmotic buffer; (2) reoxygenation-induced hypercontracture cooperates with cell swelling to produce sarcolemmal disruption; and (3) osmotic fragility persists for at least 40 min after restoration of metabolic activity.

Contraction band necrosis at the lateral borders of the area at risk in reperfused infarcts. Observations in a pig model of in situ coronary occlusion

The aim of this study was to test the hypothesis that increased mechanical stress at the lateral borders of the area at risk may render this area more susceptible to ischaemia/reperfusion injury in the absence of collateral flow. The spatial distribution of myocardial necrosis within the territory of a transiently occluded left anterior descending coronary artery was investigated in 31 porcine hearts submitted to 48 min of coronary occlusion and 6 h of reperfusion. Immediately before excising the heart, the left anterior descending coronary artery was re-occluded and 10% fluorescein was injected in the left atrium. The area at risk was imaged by ultraviolet illumination of the myocardial slices, and the area of necrosis by incubation in triphenyltetrazolium chloride. The area at risk was divided in four sectors and an index of eccentricity was calculated as the percent of the area of necrosis located in the two lateral sectors of the area at risk. The area of contraction band necrosis was measured in whole heart histological sections. Infarcts were generally small, and were composed almost exclusively of contraction band necrosis. There was a good correlation between the extent of the area of contraction band necrosis and infarct size (r = 0.831, P < 0.0005). The area of necrosis had a patchy appearance and was predominantly distributed along the lateral borders of the area at risk. This eccentric distribution was more prominent in smaller infarcts, and the eccentricity index was inversely correlated with infarct size (r = -0.471, P = 0.007), suggesting that contraction band necrosis occurs first at the interface between control and reperfused myocardium in this model. These results are in agreement with a prominent role of mechanical factors in the genesis of myocardial necrosis during transient coronary occlusion.

[Effects of reoxygenation-induced osmotic edema on cell viability. Study using isolated myocytes]

OBJECTIVE

To investigate the hypothesis that reperfusion edema may kill myocytes.

METHODS

Adult Sprague-Dawley rat hearts were perfused with a calcium free dissociation buffer containing collagenase 0.03% in a Langedorff system. Intact cells were selected and myocytes were cultured in adherent pretreated dishes. After 3 hours, 80% of cells were rod-shaped. Anoxia was simulated by means of metabolic inhibition by adding NaCN 2 mM to the control media, and reoxygenation by substituting this media with one of the following media non containing NaCN: 1) normo-osmotic (312 mOsm); 2) hypoosmotic (80 mOsm); 3) normo-osmotic with low Na+ (312 mOsm). A group of cells was kept with control media without metabolic inhibition and then submitted to simulated reoxygenation with hypoosmotic media (control group). The number of rod, square and round-shaped cells was monitored, and cell viability was assessed after 5 min of reoxygenation by the Trypan blue test.

RESULTS

After 60 min of metabolic inhibition there were no differences in the % of cells without hypercontracture among groups reoxygenated with normo-osmotic, hypoosmotic, low Na+ normo-osmotic and control media (84 +/- 16, 74 +/- 10, 76 +/- 14 and 90 +/- 6% respectively (p = NS). After 5 min of reoxygenation, these values decreased (p < 0.001) to 19 +/- 6, 11 +/- 9 and 13 +/- 3% (p = NS), respectively, in groups with normo-osmotic, hypoosmotic, and low Na+ normo-osmotic reoxygenation, but were not modified in the control group (78 +/- 4). The % of viable cells (Trypan negative) preserved after 5 min of reoxygenation was 67 +/- 29% in the group with normo-osmotic reoxygenation, 31 +/- 23% in the group with hypoosmotic reoxygenation, and 85 +/- 12% in the group with low Na+ normo-osmotic reoxygenation (p < 0.001). Exposing cells without metabolic inhibition to hypoosmotic media resulted in no significative reduction of cell viability.

CONCLUSION

Hypoosmotic reoxygenation following prolonged metabolic inhibition may kill viable myocytes. This effect is not due to the low Na+ concentration in the hypoosmotic medium.

Strategies for prognostic assessment of uncomplicated first myocardial infarction: 5-year follow-up study

OBJECTIVES

Our aim was to use noninvasive studies early after infarction to assess medium-term prognosis in patients with a first uncomplicated myocardial infarction.

BACKGROUND

Although the use of early postinfarction assessment to gauge short-term prognosis in myocardial infarction is well established, there have been few comprehensive evaluations of noninvasive methods for assessing medium- and long-term prognosis.

METHODS

We prospectively studied 115 consecutive patients < 65 years old with a first acute uncomplicated myocardial infarction to evaluate the prognostic role of predischarge cardiac studies. These included submaximal exercise testing, thallium-201 scintigraphy, radionuclide exercise ventriculography, two-dimensional echocardiography, ambulatory electrocardiographic (Holter) monitoring and cardiac catheterization. All patients without complications were followed up > or = 5 years.

RESULTS

During the follow-up period, 78 patients (68%) developed complications, which were severe in 37 (32%). Exercise thallium-201 scintigraphy yielded the highest percentage (77%) for correctly classified patients. It also had the highest predictive value for complications (97%) and severe complications (92%) when it was used in association with exercise testing and radionuclide ventriculography. The addition of cardiac catheterization did not improve on the predictive power of noninvasive studies. Four decision trees (exercise testing + echocardiography, exercise testing + radionuclide ventriculography, thallium-201 + echocardiography, thallium-201 + radionuclide ventriculography) allowed stratification of all patients in a high, intermediate or low risk category. The combination of thallium-201 scintigraphy and radionuclide ventriculography yielded the best results (90% predictive value for complications if the outcome of both tests was positive), but there were no significant differences with the other models.

CONCLUSIONS

Any combination of a test detecting residual ischemia or functional capacity, or both (exercise testing or thallium-201 scintigraphy), and a test assessing ventricular function (echocardiography or radionuclide ventriculography) results in useful prognostic information in patients with an uncomplicated first acute myocardial infarction.

Dissociation between anti-infarct effect and anti-edema effect of ischemic preconditioning

This study tested the hypothesis that preconditioning, by reducing catabolite accumulation during ischemia, reduces osmotic swelling and myocardial necrosis during subsequent reperfusion. Farm pigs were randomly allocated to one of three groups of treatment: a control group undergoing a 48-min coronary occlusion (CO) of the middle left anterior descending artery, a preconditioned group (2 cycles of 5-min CO and 5-min reperfusion before the 48-min CO), or an intracoronary perfusion group receiving a substrate-free anoxic buffer perfusion into the area at risk between minutes 5 and 10 of the prolonged CO. Animals were killed after 30 min (n = 23) or 6 h (n = 31) of reperfusion. Compared with the control group, both ischemic preconditioning and washout of ischemic by-products by transient anoxic perfusion reduced myocardial edema after 30 min of reperfusion (P < 0.002) by 35 and 32%, respectively, but only ischemic preconditioning reduced final infarct size (by 55%, P < 0.006). Myocardial lactate content before reperfusion, measured in an additional series of 12 experiments, was reduced by 35% in animals receiving preconditioning or intracoronary perfusion. Thus ischemic preconditioning has a marked protective effect against reperfusion edema, and this effect can be explained by reduced catabolite accumulation during ischemia. However, there is no evidence from this study indicating that reduced catabolite accumulation and limited reperfusion edema explain the important anti-infarct effect of ischemic preconditioning.

Purulent pericarditis: review of a 20-year experience in a general hospital

OBJECTIVES

The purpose of this study was to review the features of purulent pericarditis in patients from a general hospital during a recent 20-year period.

BACKGROUND

Although studies published from 1974 to 1977 suggested a changing spectrum for purulent pericarditis, this view has not been proved.

METHODS

We retrospectively evaluated the records of 33 patients from one general hospital who had a diagnosis of purulent pericarditis during the period 1972 to 1991. All autopsy protocols from the same period were also reviewed. In 19 patients (group I), the condition was diagnosed during life; in 14 (group II), it was identified at autopsy.

RESULTS

In group I, the possible sources of pericardial infection were identified in 17 patients; pneumonia (6 patients) was the most common source. Empyema was present in 10 patients; 15 had cardiac tamponade. The most common microorganisms were streptococci, pneumococci and staphylococci. Six patients developed constrictive pericarditis and required pericardiectomy. Three patients died, 1 patient was lost to follow up and 15 patients had a favorable outcome at a mean follow-up interval of 35 months. In group II, the clinical diagnoses included pneumonia (five patients) among other infections, with empyema in six patients. Purulent pericarditis was probably the direct cause of death in two patients.

CONCLUSIONS

In our experience, the spectrum of purulent pericarditis has not changed in recent years. Many patients do not have the classical findings of pericarditis, and diagnosis is made only at autopsy or after tamponade has developed. Empyema remains a common predisposing condition. Purulent pericarditis is still a severe disease, but its prognosis is excellent in patients who can be discharged from the hospital.

[The usefulness of Doppler echocardiography in the preoperative assessment of valvulopathies. A comparison with the hemodynamic and surgical findings]

The Doppler echocardiography and cardiac catheterization studies of all patients who underwent valvular surgery in a three-year period were reviewed to assess the correlation between the estimated severity of valvular disease by both methods. Two-hundred and thirty-five patients (group I: 140 male, age 58 +/- 12; 95 female, age 60 +/- 13) underwent both studies within 6 months. There was agreement on estimation of severity of valve lesions in 140 of 162 patients with aortic valve disease (93% of stenosis, 82% of regurgitations and 79% of mixed lesions), in 58 of 80 patients with mitral valve disease (83% of stenosis, 76% of regurgitations and 33% of mixed lesions) and in 10 of 16 patients with prosthetic valve disfunction. The correlation between both methods was significantly lower in mixed mitral lesions than in the remaining native valve lesions (p < 0.05). Significant disagreement occurred in 4 cases of aortic valve disease, four of mitral valve disease and five of prosthetic disfunction. When disagreement was present, Doppler often underestimated the severity of the disease. Disagreement was more frequent in patients with combined aortic and mitral disease. According to the surgical conclusions cardiac catheterization provided a diagnostic profit in the assessment of the disease severity in 8, 11 and 22% of cases of aortic and mitral valve disease and prosthetic valve disfunction, respectively. Coronary artery disease was present in 19% of patients who underwent coronary arteriography. One-hundred and two patients (group II: 44 m, 48 +/- 15; 58 f, 53 +/- 11) underwent surgery without previous cardiac catheterization.(ABSTRACT TRUNCATED AT 250 WORDS)