Hemodynamic spectrum of myocardial infarction and cardiogenic shock. A conceptual model

Treatment strategy for acute myocarditis in pediatric patients requiring emergency intervention

BACKGROUND

Patients with acute myocarditis present with a wide range of symptoms. Treatment strategies for pediatric patients with circulatory failure comprise extracorporeal membrane oxygenation (ECMO), emergency temporary pacing, and pharmacotherapy. However, they remain controversial. ECMO is an effective treatment but gives rise to several complications; the goal is therefore to avoid excessive treatment as much as possible. We aimed to evaluate the importance of electrocardiogram findings in differentiating severity and establish an appropriate treatment strategy in pediatric patients with acute myocarditis who required emergency interventions.

METHODS

This retrospective study enrolled pediatric patients admitted to and treated in our hospital for acute myocarditis between April 1983 and December 2021. Patients were retrospectively divided into whether circulatory failure occurred (ECMO or temporary pacing was needed; emergency intervention group) or not (pharmacotherapy alone).

RESULTS

Of the 26 pediatric patients, 11 experienced circulatory failure while 15 did not. In the circulatory failure group, six patients were treated with ECMO (ECMO group) and five patients with temporary pacing (pacing group). In the pacing group, all patients were diagnosed with complete and/or advanced atrioventricular block (CAVB and/or advanced AVB) and narrow QRS. Furthermore, these patients improved only with temporary pacing and pharmacotherapy, without requiring ECMO. Wide QRS complexes (QRS ≥ 0.12 ms) with ST-segment changes were detected on admission in five of six patients in the ECMO group and none in the pacing group (P = 0.015). Although all patients in the ECMO group experienced complications, none did in the pacing group (P < 0.008).

CONCLUSIONS

Regarding emergency intervention for acute myocarditis, ECMO or temporary pacing could be determined based on electrocardiogram findings, particularly wide QRS complexes with ST-segment changes on admission. It is important to promptly introduce ECMO in patients with wide QRS complexes with ST-segment changes, however, patients with CAVB and/or advanced AVB and narrow QRS could improve without undergoing ECMO. Therefore, excessive treatment should be avoided by separating ECMO from temporary pacing based on electrocardiogram findings on admission.

Elevated myocardial wall stress after percutaneous coronary intervention in acute ST elevation myocardial infraction is associated with increased mortality

BACKGROUND

Despite early attempts to salvage myocardium-at-risk with percutaneous coronary intervention (PCI), changes in myocardial wall stress (MWS) leads to ventricular dilatation and dysfunction after acute ST-elevation myocardial infraction (STEMI). Whether this is transient or leads to long-term adverse outcomes major adverse cardiovascular events (MACE) is not known. We studied the association between MWS and MACE in patients after a successful PCI for acute STEMI.

OBJECTIVES

To study the MWS in percutaneously revascularized STEMI patients in relation to all-cause mortality and MACE.

METHODS

We prospectively enrolled 142 patients who presented to our tertiary care hospital with acute STEMI requiring emergent PCI. In addition to the standard clinical biomarkers, both end-systolic and end-diastolic MWS was calculated using our recently validated Echocardiographic indices. Patients were then prospectively followed up to an average of 16.5 (± 12.0) months to assess all-cause mortality and MACE.

RESULTS

During the follow-up period, 9% of the patients died and 17% developed MACE. Patients who died had significantly elevated end-systolic WS compared to those who survived (mean ESWS, 80.01 ± 36.86 vs 59.28 ± 27.68). There was no significant difference in end-diastolic WS, left ventricular systolic function and peak troponin levels among survivors versus non-survivors. Elevated ESWS (>62.5 Kpa) and age remained the significant predictors of mortality on multivariate logistic analysis (OR 7.75, CI 1.33-73.86, P = .03; OR 1.16, CI 1.06-1.31, P = .002).

CONCLUSION

Elevated ESWS measured by echocardiogram is associated with increased odds of long-term mortality in STEMI patients who have undergone emergent PCI. This finding can help clinicians to risk stratify high-risk patients.

Outcome differences in acute vs. acute on chronic heart failure and cardiogenic shock

Aims

Despite advances in coronary reperfusion and percutaneous mechanical circulatory support, mortality among patients presenting with cardiogenic shock (CS) remains unacceptably high. Clinical trials and risk stratification tools have largely focused on acute CS, particularly secondary to acute coronary syndrome. Considerably less is understood about CS in the setting of acute decompensation in patients with chronic heart failure (HF). We sought to compare outcomes between patients with acute CS and patients with acute on chronic decompensated HF presenting with laboratory and haemodynamic features consistent with CS.

Methods and results

Sequential patients admitted with CS at a single quaternary centre between January 2014 and August 2017 were identified. Acute on chronic CS was defined by having a prior diagnosis of HF. Initial haemodynamic and laboratory data were collected for analysis. The primary outcome was in‐hospital mortality. Secondary outcomes were use of temporary mechanical circulatory support, durable ventricular assist device implantation, total artificial heart implantation, or heart transplantation. Comparison of continuous variables was performed using Student's t‐test. For categorical variables, the χ² statistic was used. A total of 235 patients were identified: 51 patients (32.8%) had acute CS, and 184 patients (64.3%) had acute decompensation of chronic HF with no differences in age (52 ± 22 vs. 55 ± 14 years, P = 0.28) or gender (26% vs. 23%, P = 0.75) between the two groups. Patients with acute CS were more likely to suffer in‐hospital death (31.4% vs. 9.8%, P < 0.01) despite higher usage of temporary mechanical circulatory support (52% vs. 25%, P < 0.01) compared with patients presenting with acute on chronic HF. The only clinically significant haemodynamic differences at admission were a higher heart rate (101 ± 29 vs. 82 ± 17 b.p.m., P < 0.01) and wider pulse pressure (34 ± 19 vs. 29 ± 10 mmHg, P < 0.01) in the acute CS group. There were no significant differences in degree of shock based on commonly used CS parameters including mean arterial pressure (72 ± 12 vs. 74 ± 10 mmHg, P = 0.23), cardiac output (3.9 ± 1.2 vs. 3.8 ± 1.2 L/min, P = 0.70), or cardiac power index (0.32 ± 0.09 vs. 0.30 ± 0.09 W/m², P = 0.24) between the two groups.

Conclusions

Current definitions and risk stratification models for CS based on clinical trials performed in the setting of acute coronary syndrome may not accurately reflect CS in patients with acute on chronic HF. Further investigation into CS in patients with acute on chronic HF is warranted.

How to Bail Out Patients with Severe Acute Myocardial Infarction

Cardiogenic shock (CS) is the most serious complication of acute myocardial infarction (AMI). The practice of early revascularization by percutaneous coronary intervention, and advances in pharmacotherapy have reduced the rate of complications of CS. However, when CS is combined with AMI, mortality from AMI is still high, and many clinicians are wondering how to treat CS with AMI. In recent years, mechanical circulatory support (MCS) devices have improved the clinical outcome in AMI patients with CS. For best outcome, treatment of AMI with CS should always consider treatments that improve the prognosis of the patients.

Cardiogenic shock: evolving definitions and future directions in management

Cardiogenic shock (CS) is a complex and highly morbid entity conceptualised as a vicious cycle of injury, cardiac and systemic decompensation, and further injury and decompensation. The pathophysiology of CS is incompletely understood but limited clinical trial experience suggests that early and robust support of the failing heart to allow for restoration of systemic homoeostasis appears critical for survival. We review the pathophysiology, clinical features and trial data to construct a contemporary model of CS as a systemic process characterised with maladaptive compensatory mechanisms requiring prompt and appropriately tailored medical and mechanical support for optimal outcomes. We conclude with an algorithmic approach to acute CS incorporating clinical and haemodynamic data to match the patient’s cardiac and systemic needs as a template for contemporary management.

Real-Time in Vivo Photoacoustic Imaging in the Assessment of Myocardial Dynamics in Murine Model of Myocardial Ischemia

Photoacoustic imaging (PAI) is an evolving real-time imaging modality that combines the higher contrast of optical imaging with the higher spatial resolution of ultrasound imaging. We utilized dual-wavelength PAI for the diagnosis and monitoring of myocardial ischemia by assessing variations in blood oxygen saturation estimated in a murine model. The use of high-frequency ultrasound in conjunction with PAI enabled imaging of anatomic and functional changes associated with ischemia. Myocardial ischemia was established in eight mice by ligating the left anterior descending artery (LAD). Longitudinal results reveal that PAI is sensitive to acute myocardial ischemia, with a rapid decline in blood oxygen saturation (p ˂ 0.001) observed after LAD ligation (30 min: 33.05 ± 6.80%, 80 min: 36.59 ± 5.22%, 120 min: 36.70 ± 9.46%, 24 h: 40.55 ± 13.04%) compared with baseline (87.83 ± 5.73%). Variation in blood oxygen saturation was found to be linearly correlated with ejection fraction (%), fractional shortening (%) and stroke volume (µL), with Pearson's correlation coefficient values of 0.66, 0.67 and 0.77, respectively (p ˂ 0.001). Our results indicate that PAI has the potential for real-time diagnosis and monitoring of acute myocardial ischemia.

Syndromes of Acute Left Ventricular Failure

The syndrome of acute left ventricular failure, manifesting as pulmonary edema and/or cardiogenic shock, occurs in many different clinical settings, has many different causes, and variable treatment strategies. Most commonly it is seen as a complication of acute myocardial infarction where loss of myocardial tissue results in ineffective systolic performance of the left ventricle. Urgent percutaneous transluminal coronary angioplasty may have a significant impact on outcome in this setting. Other complicating events following myocardial infarction may also precipitate left ventricular failure including papillary muscle dysfunction and ventricular septal defect. The syndrome of acute left ventricular failure is also commonly seen in patients with chronic congestive cardiac failure whereby myocardial infarction, arrhythmia and even minor increases in salt intake can precipitate acute decompensation. Other conditions such as fulminant myocarditis, bacterial endocarditis and disease processes characterized by diastolic dysfunction can all cause acute left ventricular failure. Moreover, cardiac function may be depressed in septic shock by the presence of cardiodepressant factors. In summary, acute left ventricular failure is a syndrome with a diverse etiology. Specific diagnosis of the particular cause is crucial to appropriate management.

Cardiogenic shock: a historical perspective

Significant progress has been made over the past 60 years in defining and recognizing cardiogenic shock (CS), and there have been tremendous advances in the care of patients who have this illness. Although there are many causes of this condition, acute myocardial infarction with loss of a large amount of functioning myocardium is the most frequent cause. It was recognized early in the study of CS that prompt diagnosis and rapid initiation of therapy could improve the prognosis, and this remains true today. Although the mortality from CS remains high, especially in elderly populations, modern therapies improve the chance of survival from this critical illness.

Structure and Mechanics of Healing Myocardial Infarcts

Therapies for myocardial infarction have historically been developed by trial and error, rather than from an understanding of the structure and function of the healing infarct. With exciting new bioengineering therapies for myocardial infarction on the horizon, we have reviewed the time course of structural and mechanical changes in the healing infarct in an attempt to identify key structural determinants of mechanics at several stages of healing. Based on temporal correlation, we hypothesize that normal passive material properties dominate the mechanics during acute ischemia, edema during the subsequent necrotic phase, large collagen fiber structure during the fibrotic phase, and cross-linking of collagen during the long-term remodeling phase. We hope these hypotheses will stimulate further research on infarct mechanics, particularly studies that integrate material testing, in vivo mechanics, and quantitative structural analysis.

Favourable clinical outcome in patients with cardiogenic shock due to fulminant myocarditis supported by percutaneous extracorporeal membrane oxygenation

AIMS

The clinical outcome of severe acute myocarditis patients with cardiogenic shock who require circulatory support devices is not well known. We studied the survival and clinical courses of patients with fulminant myocarditis supported by percutaneous extracorporeal membrane oxygenation (ECMO) and compared them with those of patients with acute non-fulminant myocarditis.

METHODS AND RESULTS

Patients with acute myocarditis were divided into the following two groups. Fourteen patients who required ECMO for cardiogenic shock were defined as having fulminant myocarditis (F group), whereas 13 patients who had an acute onset of symptoms, but did not have compromised, were defined as having acute non-fulminant myocarditis (NF group). In the F group, 10 patients were weaned successfully from percutaneous ECMO. Therefore, the overall acute survival rate was 71%. Patients who were not weaned from ECMO showed smaller left ventricular end-diastolic and end-systolic dimensions, thicker left ventricular wall, and higher creatine phosphokinase MB isoform levels than those who were weaned from ECMO. When compared with patients in the NF group, the fractional shortening in the F group was more severely decreased in the acute phase [F: 10+/-4 vs. NF: 23+/-8% (mean+/-SD), P<0.001], but recovered in the chronic phase (F: 33+/-7 vs. NF: 34+/-6%). The prevalence of adverse clinical events in both groups was similar during the follow-up period of 50 months.

CONCLUSION

In patients with fulminant myocarditis, percutaneous ECMO is a highly effective form of a haemodynamic support. Once a patient recovers from inflammatory myocardial damage, the subsequent clinical outcome is favourable, similar to that observed in patients with acute non-fulminant myocarditis.

Risk factors for patients developing a fulminant course with acute myocarditis

BACKGROUND

A fulminant course can be difficult to predict at the onset of acute myocarditis, so the aim of the present study was to identify the predictive clinical symptoms/signs or laboratory findings.

METHODS AND RESULTS

Thirty-nine patients with acute lymphocytic myocarditis, excluding 8 who manifested shock at admission, were studied. The fulminant group was defined as 12 patients who developed shock after admission, requiring intraaortic balloon pumping or percutaneous cardiopulmonary support, and the non-fulminant group comprised the 27 patients without shock. Various parameters at admission were compared between the 2 groups, together with multiple logistic regression analysis, excluding 6 patients with partially missing values. In the fulminant group, C-reactive protein (7.0 +/- 7.0 vs 2.3 +/- 2.2 mg/dl, p<0.01) and creatine kinase (1,147 +/- 876 vs 594 +/- 568 IU/L, p<0.05) concentrations were higher, intraventricular conduction disturbances were more frequent (9/12 vs 7/27 patients, p<0.01) and the left ventricular ejection fraction was lower (40.7 +/- 13.9 vs 50.1 +/- 10.6%, p<0.05) than in the non-fulminant group. In the multiple logistic regression analysis model with the presence/absence of a fulminant course considered as the independent variable, and C-reactive protein, creatine kinase, intraventricular conduction disturbances, and left ventricular ejection fraction as dependent variables, a high-risk group (expected proportion of fulminant course > or = 0.5) and a low-risk group (<0.5) could be differentiated. A fulminant course occurred in 9/13 (69%) patients in the high-risk group, but in only 2/20 (10%) patients in the low risk group (p<0.001).

CONCLUSIONS

The risk of a fulminant course of acute myocarditis was high in patients with elevated C-reactive protein, and creatine kinase concentrations, decreased left ventricular ejection fraction, and intraventricular conduction disturbances at the time of admission.

Cardiac power is the strongest hemodynamic correlate of mortality in cardiogenic shock: A report from the SHOCK trial registry

OBJECTIVES

We sought to analyze clinical, angiographic, and outcome correlates of hemodynamic parameters in cardiogenic shock.

BACKGROUND

The significance of right heart catheterization in critically ill patients is controversial, despite the prognostic importance of the derived measurements. Cardiac power is a novel hemodynamic parameter.

METHODS

A total of 541 patients with cardiogenic shock who were enrolled in the SHould we emergently revascularize Occluded Coronaries for cardiogenic shocK (SHOCK) trial registry were included. Cardiac power output (CPO) (W) was calculated as mean arterial pressure x cardiac output/451.

RESULTS

On univariate analysis, CPO, cardiac power index (CPI), cardiac output, cardiac index, stroke volume, left ventricular work, left ventricular work index, stroke work, mean arterial pressure, systolic and diastolic blood pressure (all p < 0.001), coronary perfusion pressure (p = 0.002), ejection fraction (p = 0.013), and pulmonary artery systolic pressure (p = 0.047) were associated with in-hospital mortality. In separate multivariate analyses, CPO (odds ratio per 0.20 W: 0.60 [95% confidence interval, 0.44 to 0.83], p = 0.002; n = 181) and CPI (odds ratio per 0.10 W/m(2): 0.65 [95% confidence interval, 0.48 to 0.87], p = 0.004; n = 178) remained the strongest independent hemodynamic correlates of in-hospital mortality after adjusting for age and history of hypertension. There was an inverse correlation between CPI and age (correlation coefficient: -0.334, p < 0.001). Women had a lower CPI than men (0.29 +/- 0.11 vs. 0.35 +/- 0.15 W/m(2), p = 0.005). After adjusting for age, female gender remained associated with CPI (p = 0.032).

CONCLUSIONS

Cardiac power is the strongest independent hemodynamic correlate of in-hospital mortality in patients with cardiogenic shock. Increasing age and female gender are independently associated with lower cardiac power.

Chronic experimental myocardial infarction produces antinatriuresis by a renal nerve-dependent mechanism

The present study focused on the role of sympathetic renal nerve activity, in mediating congestive heart failure-induced sodium retention following experimental chronic myocardial infarction. Groups of male Wistar rats (240-260 g) were studied: sham-operated coronary ligation (CON3W, N = 11), coronary ligation and sham-operated renal denervation (INF3W, N = 19), 3 weeks of coronary ligation and sympathetic renal nerve denervation (INF3WDX, N = 6), sham-operated coronary ligation (N = 7), and 16 weeks of coronary ligation (INF16W, N = 7). An acute experimental protocol was used in which the volume overload (VO; 5% of body weight) was applied for 30 min after the equilibration period of continuous iv infusion of saline. Compared to control levels, VO produced an increase (P < 0.01, ANOVA) in urine flow rate (UFR; 570%) and urinary sodium excretion (USE; 1117%) in CON3W. VO induced a smaller increase (P < 0.01) in USE (684%) in INF3W. A similar response was also observed in INF16W. In INF3WDX, VO produced an immediate and large increase (P < 0.01) in UFR (547%) and USE (1211%). Similarly, in INF3W VO increased (P < 0.01) UFR (394%) and USE (894%). Compared with INF3W, VO induced a higher (P < 0.01) USE in INF3WDX, whose values were similar to those for CON3W. These results suggest that renal sympathetic activity may be involved in sodium retention induced by congestive heart failure. This premise is supported by the observation that in bilaterally renal denervated INF3WDX rats myocardial infarction was unable to reduce volume expansion-induced natriuresis. However, the mechanism involved in urinary volume regulation seems to be insensitive to the factors that alter natriuresis.

Measurement of End-tidal Carbon Dioxide in Patients with Cardiogenic Shock Treated Using a Percutaneous Cardiopulmonary Assist System

We have reported that percutaneous cardiopulmonary assist systems (PCPS) are effective in treating life-threatening cardiogenic shock that is intractable to treatment with intraaortic balloon pumping (IABP). However, there are few clinical indices that can be used to evaluate the effectiveness of PCPS. End-tidal carbon dioxide (ET-CO(2)) content reflects pulmonary blood flow. We monitored ET-CO(2) continuously and determined whether we could use it as a new index to evaluate the effectiveness of PCPS. Seventeen patients with cardiogenic shock were intubated and evaluated by ET-CO(2) monitoring during PCPS. The etiology of shock included acute myocardial infarction (n=10), acute myocarditis (n=2), recent coronary artery bypass graft (n=1), cardiac rupture (n=1), hypertrophic obstructive cardiomyopathy complicated by ventricular fibrillation (n=1), left atrial myxoma (n=1) and artificial valve malfunction (n=1). PCPS was extremely effective in 10 of 17 patients (58.8%), and they recovered from the cardiogenic shock. The remaining 7 patients did not recover from shock, and died during PCPS. Six of ten patients who recovered from shock were successfully weaned from PCPS and 4 patients had good long-term survival. In the cases where PCPS was effective, the ET-CO(2) measured soon after the beginning of PCPS was significantly higher than in the cases in which PCPS was ineffective. Furthermore, the ET-CO(2) content increased gradually with the improvement in hemodynamics. In contrast, ET-CO(2) content remained low if PCPS was not effective. The ET-CO(2) represents a useful predictor of survival or death and is also a good index for weaning in patients treated with PCPS.

The clinical profile of patients with suspected cardiogenic shock due to predominant left ventricular failure: a report from the SHOCK Trial Registry. SHould we emergently revascularize Occluded Coronaries in cardiogenic shocK?

OBJECTIVES

We sought to evaluate the frequency of pulmonary congestion and associated clinical and hemodynamic findings in patients with suspected cardiogenic shock (CS).

BACKGROUND

The prevalence of pulmonary congestion in the setting of CS is uncertain.

METHODS

The 571 SHOCK Trial Registry patients with predominant left ventricular failure (LVF) were divided into four groups: Group A = no pulmonary congestion/no hypoperfusion = 14 (3%), Group B = isolated pulmonary congestion = 32 (6%), Group C = isolated hypoperfusion = 158 (28%) and Group D = congestion with hypoperfusion = 367 (64%). Statistical comparisons between Group C and D only, with regard to patient demographics, hemodynamics, treatment and outcome, were made.

RESULTS

A significant proportion of patients with shock had no pulmonary congestion (Group C = 28%, 95% CI, 24% to 31%). Age and gender in this group were similar to Group D. Group C patients were less likely to have a prior MI (p = 0.028), congestive heart failure (p = 0.005) and renal insufficiency (p = 0.032), and the index MI was less likely to be anterior (p = 0.044). Cardiac output, cardiac index and ejection fraction were similar for the two groups but pulmonary capillary wedge pressure was slightly lower for Group C (22 vs. 24 mm Hg, p = 0.012). Treatment with thrombolysis, angioplasty and bypass surgery was similar in the two groups. In-hospital mortality rates for Groups C and D were 70% and 60%, respectively (p = 0.036). After adjustment, this difference was no longer statistically significant (p = 0.153).

CONCLUSIONS

Absence of pulmonary congestion at initial clinical evaluation does not exclude a diagnosis of CS due to predominant LVF and is not associated with a better prognosis.

Disruption of the plasminogen gene in mice abolishes wound healing after myocardial infarction

The plasminogen system plays an important role in the proteolytic degradation of extracellular matrices during wound healing. In the present study we investigated the impact of the plasminogen system on cardiac wound healing and function after myocardial infarction. Myocardial infarction was induced in plasminogen-deficient mice (Plg-/-) and in wild-type controls (Plg+/+). Structural analysis 1, 2, and 5 weeks after infarction revealed that infarct healing was virtually abolished in Plg-/- mice, indicating that the plasminogen system is required for the repair process of the heart after infarction. In the absence of plasminogen, inflammatory cells did not migrate into the infarcted myocardium. Necrotic cardiomyocytes were not removed and the formation of granulation tissue and fibrous tissue did not occur. In these non-healing infarcted hearts, LV dilatation was not altered. In addition, gelatinolytic activity of MMP-2 and MMP-9 was depressed in the Plg-/- infarcted hearts, suggesting that the plasmin effect on infarct healing may be mediated by MMPs. Surprisingly, cardiac function was only attenuated to a rather small extent in the Plg-/- infarcted mice when compared to the wild-types. This study provides direct prove that plasmin-mediated proteolysis plays a central role in cardiac wound healing after myocardial infarction in mice.

ED use of rapid lactate to evaluate patients with acute chest pain

STUDY OBJECTIVE

To test the hypothesis that ED arrival venous lactate levels can be used to diagnose acute myocardial infarction (AMI) and to identify patients with critical illness in the triage of ED patients presenting with chest pain.

METHODS

This was a prospective, double-blind, clinical study in an urban, academic ED. We enrolled a convenience sample of adult patients who had chest pain or cardiac symptoms suggesting AMI that began within 24 hours of presentation. Patients underwent standard medical management for their chest pain. Venous lactate samples were analyzed in the ED on whole blood. An abnormal lactate level of 1.5 mmol/L or higher at the time of arrival was prospectively defined as indicating the presence of acute cardiac disease. ECG findings, levels of creatine phosphokinase (CK) and CK-MB, hospital stay data, and diagnosis of AMI by the cardiology admitting team were recorded.

RESULTS

Of the 129 patients included in the study, 73 had an initial lactate level of 1.5 mmol/L or higher. The mean lactate level (+/- SD) for all patients was 1.8 +/- 1.2 mmol/L. A total of 28 patients (21%) were diagnosed with AMI and had a mean lactate level of 2.2 +/- .7 mmol/L, compared with 1.7 +/- 1.3 mmol/L in those patients who were not diagnosed with AMI (P < .03). The sensitivity of this lactate level in diagnosing AMI was 96% (95% confidence interval [CI], 89% to 100%), and the specificity was 55% (95% CI, 45% to 64%). The negative predictive value of blood lactate was 98% (95% CI, 95% to 100%). Lactate was elevated independent of the duration of chest pain symptoms, with a median time from onset to sampling of 3 hours. Lactate was elevated in patients who either died or required longer than 48 hours of ICU care, compared with survivors not requiring ICU care (4.5 +/- 4.3 mmol/L versus 1.4 +/- .6 mmol/L, respectively; P < .01).

CONCLUSION

The blood lactate concentration obtained on ED arrival identifies those chest pain patients with critical cardiac illness (eg, AMI, severe congestive heart failure [CHF], decompensated arrhythmias). A normal blood lactate result has a high negative predictive value for AMI. An elevated lactate level used in conjunction with ECG and history distinguishes patients with significant myocardium at risk who are likely to benefit from more urgent attention and interventions by the attending physician. Additionally, hyperlactatemia clearly correlates with mortality and the need for ICU management in the acute cardiac patient presenting to the ED.

Use of the QRS scoring system in the early estimation of myocardial infarct size following reperfusion

While the QRS scoring system has been established as a convenient tool for estimating infarct size in nonreperfused patients during the chronic stage of myocardial infarction, its applicability to reperfused patients in the acute stage has not been established. To investigate whether infarct size could be estimated by the QRS scoring system soon after reperfusion, we evaluated QRS scores obtained serially 6 hours to 1 month after reperfusion, total creatine kinase release, and left ventricular ejection fraction in 126 patients with acute myocardial infarction who underwent successful reperfusion therapy. A significant correlation was observed between the QRS score obtained after 6 hours and that obtained after 1 month (r = .89). The QRS scores obtained after 6 hours and 1 month were significantly correlated with total creatine kinase release (r = -.65 and r = -.75, respectively) and left ventricular ejection fraction (r = .62 and r = .76, respectively). Thus, the QRS scoring system can be used as a simple and economical method for estimation of infarct size soon after reperfusion.

Comparison of patients with and without papillary muscle rupture during acute myocardial infarction

Seventeen of 31 patients with papillary muscle rupture (PMR) were admitted with a >24-hour delay since onset of acute myocardial infarction (AMI) in contrast to 81 of 1,012 with AMI without cardiac rupture; in 8 of 11 patients with in-hospital PMR it was preceded by new anginal pain in 5 and/or by strenuous exercise in 4; mortality was higher in those with anterior PMR, previous infarction, or 3-vessel disease than in those without PMR. Thus, persistence of physical activity before or during hospitalization, as well as postinfarction ischemia/infarct extension, appear to be relevant triggers of PMR, whereas mortality is more often associated with existence of a previous infarction, 3-vessel disease, and/or anterior PMR.

Opposite effects of the remodeling of infarcted and non-infarcted myocardium on left ventricular function early after infarction in humans. An echocardiographic study in patients examined before and after myocardial infarction

OBJECTIVE

The purpose of this study was to evaluate infarction-related changes in the infarcted and the non-infarcted myocardium using a baseline assessment of ventricular function obtained prior to the infarction.

BACKGROUND

Experimental studies have shown that both infarcted and non-infarcted myocardium contribute to the process of left ventricular dilatation soon after the infarction, but no data exist on the effect that the infarct has on the pre-infarct ventricular morphology in humans.

METHODS AND RESULTS

10 patients, out of 721 admitted to our coronary care unit with a first acute myocardial infarction over a 3-year period, had had an echocardiographic examination performed before (354 +/- 407 days) and after (10 +/- 9 days) the infarction which were adequate for quantitative evaluation. Ventricular volume (Simpson) and regional wall motion (Centerline method) were evaluated by biplane apical sections and the endocardial length of the infarct and the non-infarct segments, imaged in a cross-sectional view at the papillary muscle level, were measured. After the infarction end-diastolic and end-systolic ventricular volume increased (P = 0.0003 and P < 0.0001, respectively); diastolic and systolic infarct segment length increased (P = 0.011 and P = 0.0008, respectively), while non-infarct segment had only diastolic lengthening (P = 0.019), without systolic changes. The ejection fraction decreased after the infarction (P < 0.0001), in inverse relation to infarct size and in direct relation to diastolic non-infarct segment lengthening. In the five patients in whom there was a significant diastolic lengthening of non-infarct segment (larger than mean +/- 2 S.D. of the interobserver variability) the decrease in ejection fraction was less than in the patients without significant lengthening of this segment (P = 0.017), despite a similar echocardiographic infarct size index.

CONCLUSION

Ventricular enlargement early after myocardial infarction is due to both infarct expansion and lengthening of non-infarct segment. However, while systolic stretching of the infarct segment is a deleterious process that accounts for the increase in end-systolic volume, diastolic non-infarct segment lengthening is the expression of a functional compensatory mechanism that counteracts the reduction of the ventricular pump function secondary to the infarction.

Bezold-Jarisch reflex in myocardial infarcted rats

The Bezold-Jarisch reflex (BJR), produced by the administration of 5-hydroxytryptamine (5-HT, 4-16 micrograms/kg, iv), was evaluated in awake rats bearing short- (1 day) or long-term (30 days) myocardial infarction. Heart chronotropic response produced by acetylcholine was further assessed by Langendorff's isolated heart perfusion technique. Compared to the sham-operated group, infarcted rats showed either hypotension and tachycardia or bradycardia following short- or long-term myocardial infarction, respectively. Whereas the long-term myocardial infarction attenuated 5-HT-induced hypotension and bradycardia by about -25 and -80%, respectively, no significant response changes were observed in short-term infarcted rats. Impairment of BJR correlated significantly (P < 0.01) with the extent of myocardial necrosis in the 30-days infarcted group. Chronotropic responsiveness of the heart to acetylcholine in infarcted rats did not differ from the sham-operated group. Transmural antero-medio-lateral infarcted areas spanned over nearly 37% (1-day group) and 35% (30-days group) of the left ventricular circumference. These results indicate that cardioinhibitory and vasodepressor reflex responses to 5-HT are significantly impaired in chronic myocardial infarction associated with (1) marked hypertrophy of left atrium and/or of non-infarcted left ventricle, which are the main origin of vagal chemosensitive C-fibers, (2) morphological damage of this innervation due to the necrotic injury of the left ventricle, (3), possible attenuation in the vagal afferents located in the lungs and/or (4) enhancement of the chemical sensitivity of cardiac sympathetic afferents.

Cardiac baroreflex properties in myocardial infarcted rats

Recent studies demonstrated that chronic but not acute myocardial infarction impairs the cardiopulmonary reflex. The aim of the present study was to evaluate the baroreflex in awake rats bearing short-term (1 day) or long-term (30 days) myocardial infarction. Left ventricular infarction was produced by ligation of the anterior descending branch of the left coronary artery. In order to examine the baroreceptor reflex function by means of sigmoidal curvefitting analysis in conscious rats, reflex heart rate responses were elicited by alternate intravenous injections of phenylephrine (change, +5 to +40 mmHg) and sodium nitroprusside (change, -5 to -40 mmHg). Infarcted rats showed either hypotension plus tachycardia (1 day) or bradycardia (30 days) in resting conditions. The baroreceptor reflex gain (sensitivity) was significantly increased in 30 days (5.20 +/- 0.33 bpm/mmHg, p < 0.01) but not in 1 day (3.78 +/- 0.20 bpm/mmHg) infarcted rats when compared to sham rats (3.83 +/- 0.16 bpm/mmHg). Transmural antero-medio-lateral infarcted areas spanned over nearly 37% (1 day group) and 35% (30 days group) of the left ventricular circumference. Myocardial hypertrophy was showed in right ventricle (39%, p < 0.01) as well as in right (35%, P < 0.05) and left atria (127%, p < 0.001) in the 30 days but not in the 1 day infarcted group. The enhancement of baroreflex correlated significantly with the extent of myocardial necrosis in the 30 days infarcted group. We conclude that baroreflex control of heart rate is well preserved in short- but exaggerated in long-term myocardial infarction. The enhancement of the baroreflex gain could reflect a compensatory mechanism to the impairment of the cardiopulmonary reflex following chronic myocardial infarction and thus contributing to sustain the arterial pressure and heart rate in low levels.

The renin-angiotensin system in left ventricular remodeling

Left ventricular remodeling is a dynamic process that occurs in reaction to an insult to the myocardium. The response to either loss of cells, as may occur following myocardial infarction, or to hemodynamic overload, as may occur in aortic stenosis, is an attempt to maintain cardiac output and normalize wall tension. This is accomplished through the activation of the renin-angiotensin system and hypertrophy of noninfarcted segments of the myocardium. in the case of moderate or large infarctions these mechanisms fail to normalize wall stress. The stimulus to further remodeling remains, viable myocytes hypertrophy (with greater increases in cell length than width), the mass-to-volume ratio increases, and an exponential increase in wall stress results. This increase in myocyte tension has been associated with premature myocyte cell death. Thus, a vicious cycle is established wherein overstretch of the myocardium while sustaining cardiac output leads to progressive myocyte loss and left ventricular dilation. The renin-angiotensin system plays an integral role in this process. Its inhibition by angiotensin-converting enzyme (ACE) inhibitors both chronically and immediately after myocardial infarction has been shown to decrease left ventricular volumes and reduce mortality. Controversy exists regarding the mechanism through which ACE inhibitors exert their effects. ACE inhibitors reduce afterload/preload, circulating angiotensin II levels, and raise circulating levels of bradykinin. It is not yet clear which mechanism is responsible for the greatest impact on left ventricular dilation and mortality. inhibition of the renin-angiotensin system is clearly beneficial to cardiac performance as well as morbidity and mortality when myocardium is lost and heart failure ensues. Specific modes of action require further definition, including local and systemic effects. Possible benefits of angiotensin receptor blockade versus augmentation of bradykinin requires definition, setting the stage for further study, while the beneficial therapeutic use of these agents continues.

Prognostic value of N-terminal proatrial natriuretic factor plasma levels measured within the first 12 hours after myocardial infarction. Thrombolysis in Myocardial Infarction (TIMI) II Investigators

OBJECTIVES

The aim of the present study was to examine the relation between the plasma levels of the atrial peptide N-terminal proatrial natriuretic factor (proANF) measured during the 1st 12 h after myocardial infarction and 1-year mortality.

BACKGROUND

The atrial peptides atrial natriuretic factor and N-terminal proANF are released from cardiac atria secondary to increased atrial pressures. The plasma levels of both peptides have been found to be related to long-term prognosis when measured in the subacute phase of myocardial infarction.

METHODS

The study was of a retrospective case-control design studying patients enrolled in the Thrombolysis in Myocardial Infarction (TIMI) II trial. Seventy-six patients who died within the 1st year of enrollment in the trial were matched with another 76 patients who survived. N-terminal proANF was analyzed by radioimmunoassay at enrollment (no later than 4 h after the start of chest pain) and at 50 min, 5 h and 8 h after enrollment.

RESULTS

At all studied time points the peptide levels were significantly higher in the case group than in the control group. At 8 h after enrollment, an N-terminal proANF value above a cutoff point of 1,500 pmol/liter was associated with an odds ratio for death of 3.9.

CONCLUSIONS

The plasma level of N-terminal proANF, when measured during the 1st 12 h after the onset of chest pain, is related to 1-year mortality after myocardial infarction. Together with previous findings, these results suggest that N-terminal proANF measurements represent a valuable supplement to currently used prognostic indicators after myocardial infarction.

Infarct size after acute myocardial infarction measured by quantitative tomographic 99mTc sestamibi imaging predicts subsequent mortality

BACKGROUND

99mTc sestamibi is a recently developed radioisotope that has been used to measure myocardium at risk and infarct size. The relation between these measurements and subsequent patient outcome has not yet been demonstrated.

METHODS AND RESULTS

Two hundred seventy-four consecutive patients with acute myocardial infarction underwent tomographic 99mTc sestamibi imaging on arrival at the hospital (to measure myocardium at risk before reperfusion therapy) and at hospital discharge (to measure the amount of salvaged myocardium and final infarct size). Defect size on the sestamibi images was quantified using a threshold value of 60% of peak counts from the circumferential count profile curves generated for five representative slices of the left ventricle. Patients were followed after hospital discharge to evaluate the association between final infarct size and subsequent mortality. The median defect size measured was 27% of the left ventricle at presentation to the hospital (range, 0% to 77%) and was 12% of the left ventricle at hospital discharge (range, 0% to 68%). Almost one half of the patients had a final infarct size of < or = 10%. The median amount of myocardium salvaged was 9% (range, -31% to 75%). During a median duration of follow-up of 12 months, there were 10 deaths (7 cardiac and 3 noncardiac) and 1 resuscitated out-of-hospital cardiac arrest. There was a significant association between infarct size and overall mortality (chi 2 = 8.66, P = .003) and cardiac mortality (chi 2 = 11.89, P < .001). Two-year mortality was 7% for patients whose infarct size was > or = 12% versus 0% for patients whose infarct size was < 12%. There also was a significant association between myocardium at risk and cardiac mortality (chi 2 = 6.87, P = .009). There was no association between myocardium at risk and overall mortality or between amount of myocardium salvaged and either overall mortality or cardiac mortality.

CONCLUSIONS

Larger infarct size measured by 99mTc sestamibi imaging after acute myocardial infarction is associated with increased mortality risk during short-term follow-up.

Quantitation of myocardial dysfunction in ischemic heart disease by echocardiographic endocardial surface mapping: correlation with hemodynamic status

Autopsy studies have suggested that infarction of > 35% of the myocardium is associated with cardiogenic shock. However, the relation between the extent of myocardial dysfunction and hemodynamic status has not been defined in patients in vivo. This study investigated, in patients with short-term and chronic left ventricular dysfunction, the relation between hemodynamic status and the extent of regional dyssynergia measured by two-dimensional echocardiography with quantitative endocardial surface mapping. Sixty patients were classified into hemodynamic groups by pulmonary capillary wedge pressure and cardiac index. Two-dimensional echocardiograms were used to calculate left ventricular endocardial surface area index (ESAi), abnormal wall motion index (AWMi), percentage myocardial dysfunction (%MD), and number of wall motion abnormalities. All patients in class 4 (high pulmonary capillary wedge pressure and low cardiac index had > or = 60% MD. With univariate analysis, hemodynamic class correlated with ESAi, AWMi, %MD, the number of wall motion abnormalities, and two clinical variables (number of infarctions and use of diuretic agents). By stepwise linear regression, only AWMi and the number of infarctions were independently predictive of hemodynamic status.

Left ventricular remodeling after acute myocardial infarction

The loss of myocytes as a consequence of myocardial infarction results in a prompt reduction in regional wall motion and often leads to more protracted and progressive changes in ventricular architecture. The recognition that the process of ventricular enlargement following myocardial infarction is modifiable provided the initial rationale for the use of angiotensin-converting enzyme (ACE) inhibitors as therapy to prevent deterioration in ventricular size and function following infarction. Experimental and clinical studies have documented the effectiveness of this therapy in preventing this late enlargement following infarction. Increasing clinical evidence indicates that this new use of ACE inhibitor therapy in survivors of acute myocardial infarction will lead to an improvement in clinical outcome.

Left ventricular dysfunction in ischemic heart disease: fundamental importance of the fibrous matrix

The contractile function of the myocardium is coordinated by a fibrous matrix of exquisite organization and complexity. In the normal heart, and apparently in physiological hypertrophy, this matrix is submicroscopic. In pathological states changes are frequent, and usually progressive. Thickening of the many elements of the fine structure is due to an increased synthesis of Type I collagen, This change, which affects the myocardium in a global manner, can be observed by light microscopy using special techniques. Perivascular fibrosis, with an increase in vascular smooth muscle, is accompanied by development of fibrous septa, with a decrease in diastolic compliance. These structural changes are believed to be due to increased activation of the renin-angiotensin-aldosterone system, and to be independent of the processes of myocyte hypertrophy. Reparative or replacement fibrosis is a separate process by means of which small and large areas of necrosis heal, with the development of coarse collagen structures, which lack a specific organizational pattern. Regarding ischemic heart disease, an increase in tissue collagenase is found in experimental myocardial "stunning" and in the very early phase of acute infarction. Absence of elements of the fibrous matrix allow for myocyte slippage, and--if the affected area is large--cardiac dilatation. If, subsequently, the necrosis becomes transmural, there is further disturbance of collagen due to both mechanical strain and continued autolysis, During healing collagen synthesis increases greatly to allow for reparative scarring in the available tissue matrix. In cases of infarction with moderate or severe initial dilatation, pathological hypertrophy of the spared myocardium is progressive, accounting for late heart failure and poor survival.(ABSTRACT TRUNCATED AT 250 WORDS)

Reperfusion reduces left ventricular dilatation by preventing infarct expansion in the acute and chronic phases of myocardial infarction

Reperfusion reduces left ventricular dilatation in patients with acute myocardial infarction, but it is unclear to what extent this is a primary effect or only a consequence of the limiting effect of reperfusion on infarct size. To address this issue, 56 consecutive patients were examined by means of two-dimensional echocardiography on day 1, on day 3, before discharge, and at 6 months after an acute myocardial infarction. From this population two groups of 12 patients each, perfectly matched for site of myocardial infarction, extent of ventricular asynergy at two-dimensional echocardiography (akinesis + dyskinesis), and clinical characteristics were identified according to the creatine kinase (CK) time to peak, which was regarded as a marker of spontaneous or induced reperfusion: (1) CK time to peak of 12 hours or less (reperfused patients, n = 12), and (2) CK time to peak of more than 12 hours (nonreperfused patients, n = 12). In these two groups of patients end-diastolic and end-systolic left ventricular volumes and endocardial lengths of asynergic and normal ventricular segments, imaged in a cross-sectional view at the level of the papillary muscles, were then computed. At the first examination end-diastolic volume, end-systolic volume, and endocardial segment lengths of normal and asynergic segments were similar in the two groups of patients. Patients with late CK time to peak, however, showed a progressive increase in left ventricular systolic volumes and in asynergic endocardial segment lengths between the first and third (predischarge) examinations (p < 0.05 for both), with no change in systolic length of the normal myocardium. The left ventricular end-systolic volume and the asynergic endocardial segment length of patients with early CK time to peak, however, did not increase during hospitalization. The increment in end-systolic volume and in systolic infarct segment length from the first to the third examinations was higher in nonreperfused patients (p = 0.018 and p = 0.04, respectively). Changes similar to those detected in systole were found for diastolic volume and diastolic infarcted and noninfarcted segment length in both groups, but they did not reach statistical significance. After 6 months, an increases in volume and endocardial length were found in both groups of patients. Relative to the first examination, however, the increase in systolic volume and in asynergic systolic endocardial lengths remained greater for nonreperfused patients (p = 0.077 and p = 0.01, respectively).(ABSTRACT TRUNCATED AT 400 WORDS)

Prognosis of myocardial infarctions involving more than 40% of the left ventricle after acute reperfusion therapy

BACKGROUND

Prior studies based on autopsy data suggest that infarction of more than 40% of the left ventricle necessitates cardiogenic shock and death.

METHODS AND RESULTS

Technetium-99m Sestamibi tomography was used prospectively to measure infarct size at discharge in 166 patients with acute myocardial infarction. Patients with previous myocardial infarction or revascularization were excluded from the trial. Sixteen patients were identified with final infarct sizes > 40% of the left ventricle despite acute reperfusion therapy. These 16 patients (13 men) had a mean age of 63 +/- 10 years; 44% had a previous history of angina. Ten patients had emergent coronary angioplasty only (mean time to percutaneous transluminal coronary angioplasty [PTCA], 6.0 +/- 3.0 hours); 6 had thrombolysis (mean time to tissue plasminogen activator, 4.0 +/- 1.5 hours), of which 2 had rescue PTCA (5 and 3 hours from onset of pain). Of 15 patients who had angiograms after therapy, 15 had open infarct-related arteries. The left anterior descending artery was the infarct-related artery in 14 (9 proximal and 5 distal lesions). Half the patients had only single-vessel disease. Infarct size measured 50 +/- 7% of the left ventricle (range, 42% to 68%). Ejection fraction by radionuclide angiogram was 0.33 +/- 0.09 and 0.38 +/- 0.07 at discharge and 6 weeks, respectively. Hospital complications included shock (1 patient), pulmonary edema (2), angina (3), symptomatic nonsustained ventricular tachycardia (1), transient complete heart block (2), and transient bifascicular block (1). At follow-up (13 +/- 9 months), the patient with shock had died, but the remaining 15 patients were asymptomatic (1 had late PTCA for angina).

CONCLUSIONS

In the interventional and thrombolytic era, patients with large residual myocardial infarctions can survive without heart failure.

The effects of chronic oral milrinone therapy on early postinfarction left ventricular remodeling

Left ventricular remodeling following acute transmural myocardial infarction may result in early left ventricular enlargement. To characterize the effects of milrinone on components of early left ventricular dilation, rats (n = 120) underwent left coronary artery ligation or sham surgery. In the immediate postoperative period, rats received either no treatment or milrinone (3.17 +/- 0.08 mg/kg/day) dissolved in drinking water for 20 days. Twenty-one days after the initial surgery, hemodynamic measurements were made. The rats were then put to death and the hearts arrested in diastole were excised and fixed at a constant pressure for morphometric analysis. To examine the effects of milrinone on the relative contribution of infarcted and noninfarcted segments to early left ventricular dilation after acute myocardial infarction, a subgroup of infarcted rats chosen randomly was put to death 3 days after the initial surgery for morphometric analysis. Compared with infarcted untreated rats, infarcted milrinone-treated rats had a lower left ventricular volume (1.41 +/- 0.07 ml/kg vs 2.16 +/- 0.19 ml/kg, p < 0.001), lower left ventricular wall stress (0.64 +/- 0.03 vs 0.91 +/- 0.06, p < 0.001), and a lower expansion index (1.61 +/- 0.12 vs 2.61 +/- 0.22, p < 0.001). Morphometric analysis revealed that the noninfarcted segment length did not differ between the two infarcted groups either 3 days or 21 days after left coronary artery ligation. Infarct segment length also did not differ between the two infarcted groups at 3 days, but at 21 days infarct segment was shorter in the milrinone-treated group compared with the untreated group (p < 0.03).(ABSTRACT TRUNCATED AT 250 WORDS)

Modification of regional myocardial performance caused by blood withdrawal and infusion in acute ischaemic canine heart

The effect of changes in preload on regional myocardial motion in acute ischaemia was examined by miniature ultrasonic gauges after left anterior descending coronary artery occlusion in eight open chest dogs with the pericardium preserved. Left ventricular end-diastolic pressure was varied by blood withdrawal and infusion. When preload changed, isovolumetric shortening in the non-ischaemic region was inversely related to that in the ischaemic region. When preload decreased, stroke volume decreased and was accompanied by a decrease in end-diastolic length and ejection shortening in the non-ischaemic region together with an increase in isovolumetric bulging in the ischaemic region. When preload increased, these variables changed in opposite directions. These results indicate that in acute ischaemia: (1) changes in isovolumetric shortening in the non-ischaemic and ischaemic regions were related with each other when the level of volume expansion varied, and suggest that; (2) stroke volume is affected by end-diastolic length, ejection shortening in the non-ischaemic region and isovolumetric bulging in the ischemic region.

Pathogenesis and management of acute heart failure and cardiogenic shock: role of inotropic therapy

Patients with acute heart failure or cardiogenic shock following myocardial infarction have a high mortality. The first priority is to salvage any remaining viable myocardium, either by thrombolytic agents or, if necessary, by coronary angioplasty. A mechanical cause for the heart failure or shock needs to be excluded. Thereafter, the optimal therapeutic regimen needs to be chosen on the basis of each patient's hemodynamic profile. Patients can be broadly classified into three groups: (1) patients with a high left ventricular filling pressure (> 18 mm Hg) and a cardiac index < 2.2 L/min/m2 but systolic arterial pressure > 100 mm Hg; (2) patients with a systolic arterial pressure < 90 mm Hg, left ventricular filling pressure > 18 mm Hg, and cardiac index < 2.2 L/min/m2; and (3) patients with an elevated right ventricular filling pressure (> 10 mm Hg) and cardiac index < 2.2 L/min/m2 and a systolic arterial pressure < 100 mm Hg. Patients in the first subset usually require the use of vasodilator therapy and/or dobutamine. The choice of inotropic agent in patients in the second hemodynamic subset depends on the degree of systemic hypotension; dopamine is usually preferred initially because it increases arterial pressure in addition to improving cardiac output. Once the systemic blood pressure has been stabilized, dobutamine can be substituted for superior augmentation of cardiac output and its additional beneficial effects on the left ventricular filling pressure. Norepinephrine may be indicated in cases of severe systemic hypotension. Patients in hemodynamic subset 3, ie, right ventricular infarction, are treated with volume expansion and dobutamine. Use of nonpharmacologic means of circulatory support, eg, intra-aortic balloon pump or left ventricular assist device may also be required in any of these subsets.

Early hemodynamic results of left ventricular reconstructive surgery for anterior wall left ventricular aneurysm

To assess the efficacy of left ventricular (LV) reconstruction after aneurysmectomy, 35 consecutive patients with anterior LV aneurysm were studied before and after surgery. Surgical technique was performed by applying a circular patch after aneurysmectomy to maintain a "more physiological" LV cavity. Myocardial revascularization was performed in all but 1 patient concurrently. Global perioperative mortality was 4.8%. LV filling pressure and volumes and regional wall motion were assessed before and after surgery. The major indication for surgery was angina; 8 patients were in New York Heart Association class III/IV. The results showed a significant decrease in end-diastolic volume index (from 120 +/- 55 ml/m2 to 76 +/- 22 ml/m2, p less than 0.001), end-systolic volume index (from 74 +/- 44 ml/m2 to 40 +/- 18 ml/m2, p less than 0.001) and end-diastolic pressure (from 17 +/- 7 mm Hg to 13 +/- 5 mm Hg, p less than 0.05). Ejection fraction significantly increased (from 39 +/- 13% to 49 +/- 15%, p less than 0.001). LV wall motion significantly improved in all but the anterobasal region; the extent of LV asynergy significantly decreased after surgery. Six of the 35 patients had a deterioration of postintervention ejection fraction (from 44 +/- 14% to 34 +/- 9%). They had no reduction in LV volumes and no improvement in wall kinetics. It is concluded that LV reconstruction after aneurysmectomy induces significant early improvement of global and regional LV function in most patients; postoperative functional improvement is mainly related to the increase in inferior LV wall motion.

Progressive ventricular dilation in experimental myocardial infarction and its attenuation by angiotensin-converting enzyme inhibition

The extent to which the impaired left ventricle dilates may have important prognostic implications for survival. To determine the influence of infarct size and duration on ventricular dilation, the passive pressure-volume relation of the left ventricle in the rat after coronary artery ligation was obtained. In the early (0.25 to 2 days) phase, the pressure-volume relation was relatively unchanged in all infarct-size groups, except for a rightward shift in the low pressure range for moderate and large infarcts and a leftward shift in the high pressure range for small infarcts. From 2 to 7 days, ventricular dilatation occurred in all groups in relation to infarct size. Thereafter (to 106 days), in rats with moderate and large infarcts, the left ventricle continued to dilate. Associated with this late dilation was a decrease in left ventricular chamber stiffness and an increase in the volume to mass ratio. To determine whether the potentially deleterious progression of ventricular dilation could be attenuated, the angiotensin-converting enzyme inhibitor captopril was given 2 or 21 days after infarction and continued for 3 months. There was a significant overall effect of this treatment in attenuating left ventricular dilation, which was most pronounced in moderate infarcts. Captopril not only attenuated the rightward shift of the pressure-volume relation, but also markedly lowered left ventricular filling pressures so that operating volumes in treated rats were considerably reduced compared with those in untreated rats, even in large infarcts. Therapy with captopril also had an overall effect in prolonging survival, the most benefit being observed in moderate infarcts with lesser dilated left ventricles.

Thrombolytic treatment in acute myocardial infarction: neutrophil activation, peripheral leucocyte responses, and myocardial injury

OBJECTIVE

To examine early leucocyte responses and neutrophil activation in acute myocardial infarction treated by streptokinase and to relate the findings to coronary recanalisation and indices of myocardial damage in order to provide further information about the role of neutrophils in the evolution of injury.

DESIGN

Group analysis of paired blood samples, obtained before streptokinase treatment and one hour after it, and of three indirect measures of myocardial injury: left ventricular ejection fraction, QRS score, and peak creatine kinase.

SETTING

The coronary care unit of a district general hospital.

PATIENTS

39 patients with acute myocardial infarction who underwent paired blood sampling (before streptokinase and one hour after streptokinase) and cardiac catheterisation 5 (3-8) days later.

END POINTS

Changes in peripheral white cell and neutrophil counts and plasma elastase one hour after streptokinase infusion. Comparison of these variables in patients with and without patency of the infarct related coronary artery. Correlations between these variables and indirect measures of myocardial injury.

RESULTS

Neutrophil activation, as reflected by plasma elastase, increased sharply one hour after streptokinase. Total white cell and neutrophil counts also increased. Changes tended to be more pronounced in patients with patency of the infarct related artery, though the trend was not statistically significant. Neutrophil activation before streptokinase was unrelated to indirect indices of myocardial injury but only one hour after streptokinase a weak negative correlation with left ventricular ejection fraction had developed. Peripheral neutrophil responses showed a similar relation to ejection fraction and also correlated with peak creatine kinase and QRS score.

CONCLUSIONS

Thrombolytic treatment in acute myocardial infarction is associated with an abrupt reactive neutrophil response which provides an early measure of injury. It is also associated with neutrophil activation, probably in response to coronary recanalisation and myocardial reperfusion. Activated neutrophils are recognised as mediators of reperfusion injury in experimental infarction and the data in the present study provide preliminary evidence of a similar pathogenic role in the clinical setting.

Ventricular remodeling after myocardial infarction. Experimental observations and clinical implications

An acute myocardial infarction, particularly one that is large and transmural, can produce alterations in the topography of both the infarcted and noninfarcted regions of the ventricle. This remodeling can importantly affect the function of the ventricle and the prognosis for survival. In the early period, infarct expansion has been recognized by echocardiography as a lengthening of the noncontractile region. The noninfarcted region also undergoes an important lengthening that is consistent with a secondary volume-overload hypertrophy and that can be progressive. The extent of ventricular enlargement after infarction is related to the magnitude of the initial damage to the myocardium and, although an increase in cavity size tends to restore stroke volume despite a persistently depressed ejection fraction, ventricular dilation has been associated with a reduction in survival. The process of ventricular enlargement can be influenced by three interdependent factors, that is, infarct size, infarct healing, and ventricular wall stresses. A most effective way to prevent or minimize the increase in ventricular size after infarction and the consequent adverse effect on prognosis is to limit the initial insult. Acute reperfusion therapy has been consistently shown to result in a reduction in ventricular volume. The reestablishment of blood flow to the infarcted region, even beyond the time frame for myocyte salvage, has beneficial effects in attenuating ventricular enlargement. The process of scarification can be interfered with during the acute infarct period by the administration of glucocorticosteroids and nonsteroidal antiinflammatory agents, which result in thinner infarcts and greater degrees of infarct expansion. Modification of distending or deforming forces can importantly influence ventricular enlargement. Even short-term augmentations in afterload have deleterious long-term effects on ventricular topography. Conversely, judicious use of nitroglycerin seems to be associated with an attenuation of infarct expansion and long-term improvement in clinical outcome. Long-term therapy with an angiotensin converting enzyme inhibitor can favorably alter the loading conditions on the left ventricle and reduce progressive ventricular enlargement as demonstrated in both experimental and clinical studies. With the former therapy, this attenuation of ventricular enlargement was associated with a prolongation in survival. The long-term clinical consequences of long-term angiotensin converting enzyme inhibitor therapy after myocardial infarction is currently being evaluated. Although studies directed at attenuating left ventricular remodeling after infarction are in the early stages, it does seem that this will be an important area in which future research might improve long-term outcome after infarction.

Correlation between left ventricular risk area and clinical, electrocardiographic, hemodynamic, and angiographic variables during acute myocardial infarction

Since the area at risk for necrosis is the most important determinant of ultimate infarct size, knowledge of its size would be helpful in making therapeutic decisions during acute myocardial infarction. We hypothesized that indirect estimations of the risk area by use of clinical, electrocardiographic, hemodynamic, or angiographic variables are inaccurate in the setting of acute myocardial infarction. Accordingly, these variables were correlated with an echocardiographically derived risk area in 24 patients experiencing their first acute myocardial infarction. These patients underwent cardiac catheterization and echocardiography within 3 hours of hospital admission. The clinical (Killip class) and electrocardiographic findings (number of leads with ST segment changes) correlated poorly with the size of the risk area (r = 0.28 and r = -0.10, respectively). Hemodynamic data (which included right atrial, pulmonary artery, and pulmonary capillary wedge, aortic, and left ventricular end-diastolic pressures) and cardiac output, systemic and pulmonary vascular resistance, and heart rate demonstrated a poor correlation (r less than or equal to 0.47) with the risk area. The left ventricular ejection fraction and the number of diseased vessels determined by angiography also correlated poorly with the risk area (r = -0.47 and r = 0.10, respectively). Patients with multivessel disease were more likely to have abnormal wall motion remote from the infarct zone compared to patients with single-vessel disease (45% versus 8%, p less than 0.05). The left ventricular ejection fractions were lower in the group of patients with multivessel disease (0.43 versus 0.51, p = 0.06) and correlated better with the total extent of abnormal wall motion on echocardiography compared to patients with single-vessel disease (r = -0.67 versus r = -0.007). We conclude that clinical, electrocardiographic, hemodynamic, and angiographic variables do not provide an accurate estimate of the size of the left ventricular risk area during acute myocardial infarction. A direct visualization of left ventricular dynamics may provide a more accurate assessment of the size of the risk area and the total extent of left ventricular dysfunction.