Left ventricular function in acute myocardial infarction

Contractility, ventriculoarterial coupling, and stroke work after acute myocardial infarction using CMR-derived pressure-volume loop data

BACKGROUND

Noninvasive left ventricular (LV) pressure-volume (PV) loops derived by cardiac magnetic resonance (CMR) have recently been shown to enable characterization of cardiac hemodynamics. Thus, such PV loops could potentially provide additional diagnostic information such as contractility, arterial elastance (Ea ) and stroke work (SW) currently not available in clinical routine. This study sought to investigate to what extent PV-loop variables derived with a novel noninvasive method can provide incremental physiological information over cardiac dimensions and blood pressure in patients with acute myocardial infarction (MI).

METHODS

A total of 100 patients with acute MI and 75 controls were included in the study. All patients underwent CMR 2-6 days after MI including assessment of myocardium at risk (MaR) and infarct size (IS). Noninvasive PV loops were generated from CMR derived LV volumes and brachial blood pressure measurements. The following variables were quantified: Maximal elastance (Emax ) reflecting contractility, Ea , ventriculoarterial coupling (Ea /Emax ), SW, potential energy, external power, energy per ejected volume, and efficiency.

RESULTS

All PV-loop variables were significantly different in MI patients compared to healthy volunteers, including contractility (Emax : 1.34 ± 0.48 versus 1.50 ± 0.41 mmHg/mL, p = .024), ventriculoarterial coupling (Ea /Emax : 1.27 ± 0.61 versus 0.73 ± 0.17, p < .001) and SW (0.96 ± 0.32 versus 1.38 ± 0.32 J, p < .001). These variables correlated to both MaR and IS (Emax : r2  = 0.25 and r2  = 0.29; Ea /Emax : r2  = 0.36 and r2  = 0.41; SW: r2  = 0.21 and r2  = 0.25).

CONCLUSIONS

Noninvasive PV-loops provide physiological information beyond conventional diagnostic variables, such as ejection fraction, early after MI, including measures of contractility, ventriculoarterial coupling, and SW.

Prognostic value of depressed cardiac index after STEMI: a phase-contrast magnetic resonance study

AIMS 

An invasively measured cardiac index (CI) of ≤2.2 L/min/m2 is one of the strongest prognostic indicators after ST-elevation myocardial infarction (STEMI), however, knowledge is mainly based on invasive evaluations performed in the pre-stent era. Velocity-encoded phase-contrast cardiac magnetic resonance (PC-CMR) allows non-invasive determination of CI.

METHODS AND RESULTS 

In this prospective study, CMR was performed in 406 stable and contemporarily revascularized patients a median of 3 days after STEMI. Forward stroke volume was assessed at the level of the ascending aorta by PC-CMR. Left ventricular ejection fraction (LVEF) and global longitudinal strain (GLS) were determined by cine CMR. Major adverse cardiac events (MACE) were defined as the composite of death, myocardial infarction, or hospitalization for heart failure. Median CI was 2.52 L/min/m2 and 27% of patients had ≤2.2 L/min/m2. Median LVEF was 53% and median GLS was -12.2%. During a median follow-up of 14.2 [95% confidence interval (95% CI) 13.6-14.7] months, 41 patients (10.1%) experienced a MACE. A depressed CI was significantly associated with MACE after adjustment for LVEF, GLS, Thrombolysis in Myocardial Infarction (TIMI) risk score, and infarct size [hazard ratio = 3.15 (95% CI 1.53-6.47); P = 0.002] and led to significant discrimination improvement [net reclassification improvement 0.61 (95% CI 0.25-0.97); P < 0.001].

CONCLUSIONS 

A CI of 2.2 L/min/m2 or less as measured by PC-CMR was present in 27% of clinically stable patients after STEMI and strongly and independently predicted medium-term MACE. The prognostic value of a depressed CI was superior and incremental to LVEF, GLS, TIMI risk score, and infarct size.

Mechanical circulatory support device-heart hysteretic interaction can predict left ventricular end diastolic pressure

The full potential of mechanical circulatory systems in the treatment of cardiogenic shock is impeded by the lack of accurate measures of cardiac function to guide clinicians in determining when to initiate and how to optimally titrate support. The left ventricular end diastolic pressure (LVEDP) is an established metric of cardiac function that refers to the pressure in the left ventricle at the end of ventricular filling and immediately before ventricular contraction. In clinical practice, LVEDP is typically only inferred from, and poorly correlates with, the pulmonary capillary wedge pressure (PCWP). We leveraged the position of an indwelling percutaneous ventricular assist device and advanced data analysis methods to obtain LVEDP from the hysteretic operating metrics of the device. We validated our hysteresis-derived LVEDP measurement using mock flow loops, an animal model of cardiac dysfunction, and data from a patient in cardiogenic shock to show greater measurement precision and correlation with actual pressures than traditional inferences via PCWP. Delineation of the nonlinear relationship between device and heart adds insight into the interaction between ventricular support devices and the native heart, paving the way for continuous assessment of underlying cardiac state, metrics of cardiac function, potential closed-loop automated control, and rational design of future innovations in mechanical circulatory support systems.

Predicting tachycardia as a surrogate for instability in the intensive care unit

Tachycardia is a strong though non-specific marker of cardiovascular stress that proceeds hemodynamic instability. We designed a predictive model of tachycardia using multi-granular intensive care unit (ICU) data by creating a risk score and dynamic trajectory. A subset of clinical and numerical signals were extracted from the Multiparameter Intelligent Monitoring in Intensive Care II database. A tachycardia episode was defined as heart rate ≥ 130/min lasting for ≥ 5 min, with ≥ 10% density. Regularized logistic regression (LR) and random forest (RF) classifiers were trained to create a risk score for upcoming tachycardia. Three different risk score models were compared for tachycardia and control (non-tachycardia) groups. Risk trajectory was generated from time windows moving away at 1 min increments from the tachycardia episode. Trajectories were computed over 3 hours leading up to the episode for three different models. From 2809 subjects, 787 tachycardia episodes and 707 control periods were identified. Patients with tachycardia had increased vasopressor support, longer ICU stay, and increased ICU mortality than controls. In model evaluation, RF was slightly superior to LR, which accuracy ranged from 0.847 to 0.782, with area under the curve from 0.921 to 0.842. Risk trajectory analysis showed average risks for tachycardia group evolved to 0.78 prior to the tachycardia episodes, while control group risks remained < 0.3. Among the three models, the internal control model demonstrated evolving trajectory approximately 75 min before tachycardia episode. Clinically relevant tachycardia episodes can be predicted from vital sign time series using machine learning algorithms.

Keeping donor hearts in completely beating status with normothermic blood perfusion for transplants

BACKGROUND

Previously, we reported the preservation method of donor hearts in an empty beating status with mild hypothermic perfusion. To completely avoid cardiac arrest and myocardial ischemia, we performed the beating preservation technique from procurement of hearts to transplants and assessed its efficacy for long-term preservation and feasibility for heart transplantation.

METHODS

Thirty-two swine donor hearts were preserved in beating status (group A, n = 8 pairs, perfused continuously with normothermic blood) or in static cold storage (group B, n = 8 pairs, stored in 4°C histidine-tryptophan-ketoglutarate solutions) for 8 hours. Then the donor hearts were implanted either in beating or static status. During transplantation, the incidence of arrhythmia, duration of anastomosis and cardiopulmonary bypass, and dosage of inotropic drugs were recorded. Hemodynamics of left ventricle and serum level of creatine kinase-MB were measured during transplantation. Myocardial ultrastructure was observed.

RESULTS

Compared with group B, in group A the anastomotic time was significantly longer, the cardiopulmonary bypass time was significantly shorter, the cardiac output was larger, and the incidence of arrhythmia, dosage of cardiovascular-active drugs, and serum level of creatine kinase-MB were lower. After declamping for 2 hours and 3.5 hours, the left ventricular hemodynamics of group A was significantly better than that of group B. The myocardial ultrastructure of group A was superior to that of group B.

CONCLUSIONS

Preservation of donor hearts in beating status with continuous, normothermic, blood perfusion is an effective approach for long-term preservation and is appropriate for heart transplantation.

Acute haemodynamic effects of accelerated idioventricular rhythm in primary percutaneous coronary intervention

AIMS

Accelerated idioventricular rhythm (AIVR) is very frequently observed in primary percutaneous coronary intervention (PCI), however knowledge of the haemodynamic effects is lacking.

METHODS AND RESULTS

We studied an ST-segment elevation myocardial infarction cohort of 128 consecutive patients (aged 62±11 years) in whom AIVR occurred following reperfusion during primary PCI. Mean systolic blood pressure (SBP), diastolic blood pressure (DBP) and heart rate were determined during periods of AIVR and sinus rhythm. We grouped patients according to the infarct-related artery and the site of the coronary occlusion. AIVR caused an immediate reduction in SBP (130±27 vs. 98±22 mmHg, p<0.001) and DBP (80±19 vs. 69±16 mmHg, p<0.001) and a small increase in heart rate (78±12 vs. 83±11 bpm, p<0.001) as compared to sinus rhythm, irrespective of infarct-related artery. Both absolute as well as relative reduction in SBP were more pronounced in distal than proximal left coronary artery (LCA) occlusions (36±16 vs. 27±12 mmHg, p<0.01, respectively 25±9 vs. 20±8%, p<0.05). These haemodynamic differences between proximal and distal occlusion sites were not observed in the right coronary artery.

CONCLUSIONS

AIVR following reperfusion is associated with marked reduction in both SBP and DBP, irrespective of infarct-related artery. These haemodynamic effects are accompanied by only a very modest increase in heart rate during AIVR. Patients with a culprit lesion in the proximal LCA showed a smaller reduction in systolic blood pressure than distal LCA lesions.

Assessment of cardiac function with the pressure-volume conductance system following myocardial infarction in mice

Myocardial infarction (MI) is a major cause of heart failure (HF) with the progressive worsening of cardiac performance due to structural and functional alterations. Therefore, we studied cardiac function in adult mice following MI using the Millar pressure-volume (P-V) conductance catheter system in vivo during the later phase of compensatory remodeling and decompensation to HF. We evaluated load-dependent and -independent parameters in control and 2-, 4-, 6-, and 10-wk post-MI mice and integrated changes in function with changes in gene expression. Our results indicated a significant deterioration of cardiac function in post-MI mice over time, reflected first by systolic dysfunction, followed by a transient improvement before further decline in both systolic and diastolic function. Associated with the function and adaptive remodeling were transient changes in fetal gene and extracellular matrix gene expression. However, undermining the compensatory remodeling response was a continual decline in cardiac contractility, which promoted the transition into failure. Our study provided a scheme of integrated cardiac function and gene expression changes occurring during the adaptive and maladaptive response of the heart independent of systemic vascular properties during the transition to HF following MI in mice. P-V loop analysis was used to quantitatively evaluate the gradual deterioration in cardiac function post-MI. P-V loop analysis was found to be an appropriate method for assessment of global cardiac function under varying load-dependent and -independent conditions in the murine model with many similarities to data obtained from larger animals and humans.

Left ventricular diastolic function following myocardial infarction

An acute myocardial infarction causes a loss of contractile fibers which reduces systolic function. Parallel to the effect on systolic function, a myocardial infarction also impacts diastolic function, but this relationship is not as well understood. The two physiologic phases of diastole, active relaxation and passive filling, are both influenced by myocardial ischemia and infarction. Active relaxation is delayed following a myocardial infarction, whereas left ventricular stiffness changes depending on the extent of infarction and remodeling. Interstitial edema and fibrosis cause an increase in wall stiffness which is counteracted by dilation. The effect on diastolic function is correlated to an increased incidence of adverse outcomes. Moreover, patients with comorbid conditions that are associated with worse diastolic function tend to have more adverse outcomes after infarction. There are currently no treatments aimed specifically at treating diastolic dysfunction following a myocardial infarction, but several new drugs, including aldosterone antagonists, may offer promise.

Cardiac and hemodynamic effects of TZC-5665, a novel pyridazinone derivative, and its metabolite in humans and dogs

1. TZC-5665 is a novel pyridazinone derivative with vasodilatory and beta-adrenergic blocking activities and type III phosphodiesterase inhibitory action. 2. In healthy volunteers, TZC-5665 was rapidly absorbed and immediately metabolized. Its main metabolite, M-2, remained at a higher concentration in plasma. Orally administered TZC-5665 reduced end-diastolic left ventricular volume (20.16 ml) and exhibited a tendency to increase ejection fraction (0.04). 3. In dogs, M-2 dose-dependently increased cardiac contractility and reduced both preload and afterload. These effects appeared more potent in the failed heart than in the normal heart. At the same dose (30 micrograms/kg), the effects of M-2 seem to be more potent than those of milrinone. 4. We concluded that TZC-5665 is a useful medication for treating patients with chronic congestive heart failure (CHF) because of the positive inotropic and vasodilating effects due to its active metabolite in addition to its own beta-adrenergic blocking actions.

Maintenance fluids in prehospital care: crystalloid versus dextrose solutions--is there a difference?

D5W is the maintenance fluid often used in prehospital care when transporting patients with cardiac or central nervous system processes. However, there is evidence that dextrose solutions are potentially harmful, and that suggests isotonic crystalloid solutions are the preferred maintenance fluid in treating emergent patients regardless of their underlying disease. Dextrose solutions may exacerbate cellular ischemic damage and they cannot be used to resuscitate hypotensive patients. Crystalloids do not cause fluid overload when used at maintenance rates and are effective resuscitative agents in managing hypotension. The use of a single crystalloid solution in the prehospital environment would simplify equipment stocking and management protocols, minimize cost, and would not have an adverse impact on patient care.

Neuroendocrine activation after acute myocardial infarction

Neuroendocrine response after acute myocardial infarction (MI) results in activation of the sympathetic nervous system, the renin-angiotensin system, and vasopressin and atrial natriuretic peptide release. The net effect of this response is vasoconstriction, cardiac stimulation and regional flow redistribution that may have a favorable effect in some situations and a deleterious effect in others. The possible adverse effects of vasoconstriction were studied in a Veterans Administration Cooperative Study that evaluated a 48-hour infusion of sodium nitroprusside in the setting of acute MI. In the presence of mild, probably primarily diastolic left ventricular dysfunction, nitroprusside appeared to have an adverse effect on long-term survival. However, in the presence of more severe, probably predominantly systolic dysfunction, nitroprusside had a favorable effect on the prognosis. Therefore, the decision of whether to accept or inhibit neuroendocrine activation in acute MI probably depends on the severity of the disease and the timing of the therapeutic intervals.

Significance of the magnitude of a QS wave deflection in evaluating the uninvolved muscle in anterior wall myocardial infarction

The significance of dynamic changes of the QS wave magnitude, as demonstrated in the precordial leads, within the natural evolution of acute anterior wall myocardial infarction (AAMI) was assessed in 25 patients within two weeks of their admission to the intensive cardiac care unit. Two sets of tests, including 12-lead electrocardiogram and a full radionuclear study, were performed in two time periods: (1) within the first 48 hours of admission; and (2) between the 12th and 15th day after admission. Comparison and correlation between the electrocardiographic data, QS waves in leads V2 and V3 and in V1 to V6 (sigma QV2-3 and sigma QV1-6), and radionuclear regional ejection fractions of the noninfarcted posterior muscle (inferior, infero-apical, and posterolateral regions and posterior index) were done. Significant linear correlations were demonstrated between the electrocardiographic variant differences in percentages (sigma QV2-3 and sigma QV1-6) and the radionuclear variant differences, especially the posterolateral and the infero-apical regions, as well as the posterior radionuclear index (r between 0.5 and 0.75; p less than 0.01). In addition, almost all of the patients who showed deepening of QS waves in the precordial leads also showed an increase in regional ejection fractions in uninvolved myocardium, and vice versa. It is concluded that the dynamic changes of the QS wave magnitude in the precordial leads within the evolution of acute anterior myocardial infarction well reflect the changes of the posterior noninfarcted muscle contraction and therefore offers a simple, inexpensive, and indirect electrocardiographic method for evaluating changes in contraction patterns of noninfarcted myocardium.

Rate and extent of recovery of left ventricular function in patients following acute myocardial infarction

To determine the rate and extent of recovery of left ventricular (LV) performance following acute myocardial infarction (MI), peak aortic blood acceleration was measured serially in 26 patients and in 11 normal volunteers with a continuous wave Doppler placed suprasternally. In patients, Doppler measurements were made 20 +/- 2 hours after the acute onset of chest discomfort and were repeated daily for 6 consecutive days. Infarction patients were divided into two groups. Group I consisted of 15 patients who did not have a previous MI and whose present course was not complicated by congestive heart failure (CHF). Group II consisted of 11 patients who had either a previous MI or developed CHF during the present admission. Peak acceleration in the normal volunteers showed minimal daily variations over a period of 6 days. Peak acceleration in the entire group of 26 MI patients increased from 13 +/- 3 m/sec/sec on the day of admission (day 1) to 18 +/- 6 m/sec/sec on day 6 (p less than 0.001). In group I, peak acceleration increased from 13 +/- 4 to 20 +/- 6 m/sec/sec between day 1 and day 6 (p less than 0.001). In group II, however, peak acceleration was 12 +/- 2 m/sec/sec on day 1 and increased to only 15 +/- 4 m/sec/sec on day 6 (NS). These results indicate that LV performance, based upon peak acceleration of blood in the ascending aorta, improves markedly within 6 days in patients suffering their first MI uncomplicated by CHF.(ABSTRACT TRUNCATED AT 250 WORDS)

Total body oxygen consumption and haemodynamics during the treatment of acute ischaemic heart failure with dopamine and high doses of insulin in dogs

Acute ischaemic left ventricular failure was induced in closed-chest anaesthetized dogs by injection of 50 microns plastic microspheres into the left main coronary artery. This effected a 33% decrease in cardiac output. Dopamine and high doses of insulin restored cardiac output, and these agents in combination raised cardiac output to 34% above pre-ischaemic levels. Total body oxygen consumption was calculated at the various levels of cardiac output, and was found to remain essentially unchanged. Inotropic agents, then, may result in overperfusion with respect to oxygen demand.

Hemodynamic abnormalities in acute myocardial infarction

Great strides have been made in the management of patients with acute myocardial infarction since the advent of coronary care units. However, congestive heart failure continues to be the major cause of in-hospital mortality. The accurate diagnosis and classification of hemodynamic abnormalities allow the application of specific therapies for each patient. Because clinicians can now routinely measure left and right ventricular preload, systemic and pulmonary vascular resistance, cardiac output, and arteriovenous oxygen difference, pharmacologic and surgical interventions can be applied in a scientific manner. In addition, mechanical complications can be promptly recognized and aggressively treated. Although the mortality rate for patients with severe left ventricular dysfunction after myocardial infarction remains high, expert management offers an improved prognosis for many patients.

Intravenous amrinone in left ventricular failure complicated by acute myocardial infarction

Hemodynamic dose-response effects of intravenous amrinone were studied in 22 male patients aged 38 to 62 years with left ventricular failure occurring within 18 hours of acute myocardial infarction. After hemodynamic confirmation of a raised left-sided cardiac filling pressure--pulmonary artery occluded pressure greater than 20 mm Hg--patients were randomized to either low-dose infusion of amrinone (200 micrograms/kg/hr for 30 minutes, 400 micrograms/kg/hr for 30 minutes and then 800 micrograms/kg/hr for 30 minutes) or high-dose infusion of the drug (800, 1,600 and 3,200 micrograms/kg/hr sequentially, each for 30 minutes). Hemodynamic measurements were obtained at 1 hour before amrinone and at the end of each infusion step. Low-dose infusion of amrinone resulted in a progressive increase in cardiac output (p less than 0.05) and stroke volume (p less than 0.05) and progressive reductions in pulmonary artery occluded pressure (p less than 0.01) and systemic vascular resistance (p less than 0.05). Systemic blood pressure and heart rate were unchanged. High-dose infusion resulted in a similar increase in cardiac output (p less than 0.05) but no change in stroke volume owing to associated tachycardia (p less than 0.01). There was a significantly greater decrease in pulmonary artery occluded pressure compared with the low-dose infusion (p less than 0.05), and systemic arterial diastolic and mean pressures were also decreased (p less than 0.05). The decrease in systemic vascular resistance was of a similar order to that induced by the low-dose infusion.(ABSTRACT TRUNCATED AT 250 WORDS)

Hemodynamic effects of vasodilators and long-term response in heart failure

Hemodynamic responses to vasodilators are commonly assessed when starting long-term vasodilator treatment in patients with chronic left ventricular failure, although the relation between short- and long-term responses is not established. Thus, short- and long-term hemodynamic responses to placebo and vasodilators (isosorbide dinitrate, minoxidil and enalapril or captopril) were measured and long-term clinical efficacy was assessed by changes in exercise capacity after 1 to 5 months of vasodilator administration (plus digitalis and diuretic agents) in 46 patients with New York Heart Association functional class II to IV heart failure caused by cardiomyopathy. There were no significant changes in hemodynamics or exercise capacity during placebo treatment. After initial doses and during long-term administration of vasodilator drugs, hemodynamics were significantly improved. After long-term vasodilator treatment, maximal oxygen uptake during exercise increased by 2.9 +/- 5.7 ml/min per kg from a control value of 14.1 +/- 5.6 ml/min per kg (p less than 0.01), and exercise duration also increased by 1.8 +/- 3.5 minutes (p less than 0.01). Changes in maximal oxygen uptake, however, did not correlate with short-term changes in pulmonary wedge pressure (correlation coefficient [r] = -0.14), cardiac index (r = -0.01) or systemic vascular resistance (r = -0.20). Long-term hemodynamic changes also failed to correlate with changes in exercise capacity. Baseline hemodynamics, cardiac dimensions and left ventricular ejection fraction before vasodilator administration all failed to correlate with baseline exercise capacity or with long-term changes in exercise capacity. Thus, hemodynamic measurements at initiation or during follow-up of vasodilator therapy do not relate to long-term clinical efficacy assessed by exercise capacity in patients with chronic left ventricular failure. Therefore, the rationale for making invasive hemodynamic measurements before initiating long-term vasodilator therapy for heart failure is questioned.

Mitochondrial and cytoplasmic isoenzymes of aspartate aminotransferase in sera of patients after myocardial infarction

Mitochondrial and cytoplasmic isoenzymes of aspartate aminotransferase (AST) were studied in the sera of 42 patients following acute myocardial infarction and compared to creatine kinase (CK), lactate dehydrogenase (LDH) and alanine aminotransferase (ALT). Mitochondrial AST( ASTm ) was detected in 93% (39/42) of patients. Maximum recorded ASTm activity was 59.5 +/- 8.8 U/l and was found 39.4 +/- 3.5 hours after the onset of symptoms (chest pain) of myocardial infarction. In contrast the maximum recorded cytoplasmic AST ( ASTc ) activity was greater (327 +/- 23 U/l) and it occurred earlier (33.5 +/- 2.2 hours) after onset of infarction compared to ASTm . ASTm correlated significantly (p less than 0.05) with ASTc , LDH and ALT but not with total CK or CK-MB. ASTc correlated significantly (p less than 0.05) with total CK, CK-MB and LDH but not ALT. Maximum recorded ASTm activity was significantly associated with the clinical assessment of left ventricular failure ( Killip classification) but not with ventricular arrhythmias. In a subset of 15 patients evaluated with invasive hemodynamic measurements of cardiac output and pulmonary capillary wedge pressure. ASTm correlated significantly (p less than 0.05) and better than CK-MB with the hemodynamic assessment of left ventricular dysfunction. Thus ASTSm can be readily identified in sera of patients after acute myocardial infarction and may be of value in the evaluation of patients with acute myocardial infarction.

Ritodrine hydrochloride infusion in pregnant baboons. II. Sodium and water compartment alterations

To evaluate the effects of intravenously administered ritodrine hydrochloride on sodium and water metabolism, a pregnant baboon model was studied. Animals given ritodrine retained significantly more sodium (p less than 0.001) and administered fluids (p less than 0.002) compared with control animals. Although plasma volume did not change significantly within or between the two groups, extracellular volume increased by a mean of 1,480 ml in those given ritodrine compared with 790 ml in the control animals. There was no significant difference between animals given ritodrine and their controls regarding serial hematocrits, serum sodium, or colloid oncotic pressures. From this we conclude that the retained sodium and water was in the interstitial space. Since plasma volume was unaltered by ritodrine administration it seems unlikely that pure volume overload can explain the pulmonary edema induced by beta-mimetics. Combined with the prior observation that direct pulmonary capillary membrane toxicity does not occur, the likely pathophysiology of beta-agonist-induced pulmonary edema involves left ventricular failure.

Haemodynamic advantages of isosorbide dinitrate over frusemide in acute heart-failure following myocardial infarction

The immediate haemodynamic effects of intravenous frusemide (1 mg/kg) and intravenous isosorbide dinitrate (50-200 micrograms/kg/h) were compared in a prospective, randomised, between-group study in 28 men with radiographic and haemodynamic evidence of left ventricular failure following acute myocardial infarction. The diuresis induced by frusemide reduced the left heart filling pressure and cardiac output and transiently raised systemic blood-pressure. In contrast, isosorbide dinitrate was accompanied by a reduction in systemic blood-pressure and peripheral resistance with the result that the cardiac output was not decreased despite a large fall in the pulmonary vascular and left heart filling pressures. These results indicate that reduction of excessive preload by venodilatation may be haemodynamically superior to that induced by diuresis in terms of both reducing myocardial oxygen consumption and maintaining peripheral perfusion. The influence of these contrasting treatments on the prognosis of these high-risk patients warrants further study.

Progression of myocardial damage following coronary microembolization in dogs

The aim of the present study was to determine whether induction of ischaemic heart failure by micro-embolization leads to only a single episode of myocardial injury or whether it sets up a vicious cycle of progressive myocardial damage. Acute left ventricular (LV) failure was produced in 15 closed-chest anaesthetized dogs by injection of 50 microns plastic microspheres into the left main coronary artery. The dogs showed signs of severely depressed LV function; there was a marked increase in LV end-diastolic pressure and a marked decrease in stroke volume. Myocardial lactate uptake decreased or reversed to production. Six dogs with very high LV end-diastolic pressure died during the subsequent 3 days and autopsy revealed pulmonary edema. The LV function was re-examined in four dogs at 2 and 4 weeks after embolization. Except for a modest elevation of LV end-diastolic pressure there were no haemodynamic or metabolic signs of myocardial dysfunction. Gross and light microscopic examination of the heart in dogs 8 hours to 6 weeks following microsphere injections revealed numerous small infarcts or focal areas of granulation or scar tissue throughout the entire left ventricle. At 1 to 6 weeks close to the infarcts there were scattered myocytes with strong eosinophilia and pyknosis or loss of nuclei, interpreted as myocytolysis. In two dogs killed at six weeks after the embolization there were areas of granulation tissue, similar to a recent infarction about 1 week old. Thus, in spite of apparent functional restoration there were morphological signs of repeated and progressive myocardial injury several weeks after coronary embolization.

Comparison of clinical signs and hemodynamic state in the early hours of transmural myocardial infarction

The initial PCW, Killip-Scheidt classification, presence of third heart sound, and mortality were compared in 90 patients presenting with acute transmural myocardial infarction. Clinical and hemodynamic assessment was performed within 12 hours (time to clinical classification = 4.7 +/- 2.7 hours (mean +/- SD), time to hemodynamic assessment = 5.8 +/- 2.4) of the sentinel event. A poor correlation was observed between early Killip-Scheidt clinical classification and early hemodynamic state when measured as percent correct classification (66%) or as a Kappa statistic (36% for the total population, 9% for nonsurvivors). Increased initial LVFP (greater than 18 mm Hg) was associated with increased mortality (p less than 0.01) and early clinical classification was not. Addition of third heart sound information did not alter this observation.

A reproducible and stable model of acute ischaemic left ventricular failure in dogs

A model of acute ischaemic left ventricular (LV) failure is presented. In closed-chest anaesthetized dogs 50 micrometer plastic microspheres were injected repeatedly into the left main coronary artery over a period of about 40 min. The injections effected stepwise elevations of LV end-diastolic pressure (LVEDP). Thus, LVEDP could be increased to a desired level, about 20 mmHg, in a very controlled manner. All dogs developed signs of markedly depressed LV performance. Haemodynamic conditions stabilized about 60 min after embolization. The maximum LVDP/dt decreased from 2696 +/- 169 to 1823 +/- 98 mmHg . x-1, cardiac output decreased from 2.81 +/- 0.20 to 1.98 +/- 0.14 l . min-1 and mean aortic blood pressure decreased from 144 +/- 4 to 127 +/- 3 mmHg, while total peripheral resistance increased from 56 +/- 3 to 69 +/- 3 mmHg . l-1 . min. Myocardial blood flow decreased from 103 +/- 7 to 79 +/- 6 ml . min-1 . 100 g-1 and myocardial oxygen consumption decreased from 12.5 +/- 0.9 to 8.3 +/- 0.8 ml . min-1. 100 g-5. Myocardial uptake of lactate and free fatty acids decreased markedly. Electrocardiography showed signs of acute ischaemia. There were no deaths due to ventricular fibrillation. Morphological studies showed multiple small infarcts throughout the entire LV. In conclusion, repeated coronary embolization with 50 micrometers plastic microspheres, guided by the rise of LVEDP represents a simple and reproducible method for induction of uniform and stable acute LV failure.

Effect of short-term infusion of sodium nitroprusside on mortality rate in acute myocardial infarction complicated by left ventricular failure: results of a Veterans Administration cooperative study

Eight hundred twelve men with presumed acute myocardial infarction and left ventricular filling pressure of at least 12 mm Hg participated in a randomized double-blind placebo-controlled trial to assess the efficacy of a 48-hour infusion of sodium nitroprusside. The mortality rates at 21 days (10.4 per cent in the placebo group and 11.5 per cent in the nitroprusside group) and at 13 weeks (19.0 per cent and 17.0 per cent, respectively) were not significantly affected by treatment. The efficacy of nitroprusside was related to the time of treatment: the drug had a deleterious effect in patients whose infusions were started within nine hours of the onset of pain (mortality at 13 weeks, 24.2 per cent vs. 12.7 per cent; P = 0.025) and a beneficial effect in those whose infusions were begun later (mortality at 13 weeks, 14.4 per cent vs. 22.3 per cent; P = 0.04). Nitroprusside should probably not be used routinely in patients with high left ventricular filling pressures after acute myocardial infarction. However, the results in the patients given late treatment suggest that those with persistent pump failure might receive sustained benefit from short-term nitroprusside therapy.

Vasodilator therapy: implications in acute myocardial infarction and congestive heart failure

The physiologic effects of systemic vasoconstriction on left ventricular performance and the salutary hemodynamic effect of acute administration of vasodilator drugs to patients with heart failure provide a rational basis for vasodilator therapy in acute myocardial infarction and chronic congestive heart failure. Use of vasodilators during the acute phase of myocardial infarction may reduce mortality when left ventricular filling pressure remains markedly elevated for at least 8 hours after the onset of clinical syndrome. Use of chronic vasodilator therapy in patients with congestive heart failure appears to have been effective in some patients in prolonging exercise tolerance; however, the likelihood of a beneficial effect and the impact of this therapy on the natural history of the disease remain unclear. A Veterans Administration Cooperative Study to address these questions is currently in progress. The new effort directed to studying the effects of vasodilator drugs in these syndromes has appropriately focused attention on their pathophysiology and natural history.

A QRS scoring system for assessing left ventricular function after myocardial infarction

A QRS scoring system for estimating the size of a myocardial infarct was evaluated in 55 patients who did not have left ventricular hypertrophy or conduction abnormalities. Serial 12-lead surface electrocardiograms were scored according to a 29-point system based on the duration of Q and R waves and on the ratios of R-to-Q amplitude and R-to-S amplitude. The scores were proportional to the severity of wall-motion abnormalities, which was determined by radionuclide blood-pool scanning and which correlated inversely with the radionuclide-determined left ventricular ejection fraction (LVEF). A score less than 3 was 93 per cent sensitive and 88 per cent specific for both severe regional dyssynergy and major depression of the global LVEF. The following equation was used to estimate the LVEF from the QRS score: LVEF (%) = 60 - (3 x QRS score). After acute myocardial infarction, an electrocardiogram can provide important indirect quantitative information about left ventricular function.

Effects of methylprednisolone on P50, 2,3 diphosphoglycerate and arteriovenous oxygen difference in acute myocardial infarction

In a double-blind randomized study, 30 mg/kg of methylprednisolone sodium succinate (MPN) or 15 mg/kg of mannitol placebo (PL) were infused in 28 patients after acute myocardial infarction. Measurements were obtained immediately before and after for 24 hours after the initial infusion. The partial pressure of oxygen at 50% saturation of hemoglobin (P50) did not change significantly in vitro or in vivo after MPN, whereas 2,3 diphosphoglycerate (2,3 DPG) increased from 13.2 to 14.2 mumol/g Hb (p < 0.05) in the group receiving PL. The arteriovenous oxygen difference (Ca-VO2) remained constant after MPN or PL. The cardiac index (CI) increased after MPN (p < 0.02) associated with an increase in the oxygen consumption index (CI X A-V O2) from 146 to 170 ml/min/m2 (p < 0.05). These data show that MPN increases CI after acute myocardial infarction, but has no specific effects on P50, 2,3 DPG or Ca-VO2.

Cardiovascular function during early recovery from acute myocardial infarction

Fifty patients with acute myocardial infarction were studied serially to evaluate the extent and nature of functional cardiovascular impairment and the time course of recovery. Reinfarction or death occurred in six patients. Peak workload during bicycle exercise in a subgroup of 25 patients with maximal initial test and complete follow-up increased from 334 to 409 kpm/min (P less than 0.01) bwtween three and six weeks. There was further significant (P less than 0.01) improvement between three and six months from 438 to 488 kpm/min. The incidence of ischemia at a constant workload decreased between three and six weeks without any significant changes in heart rate or blood pressure. Mean cardiac output during exercise at three months was 6.5 and at six months 7.8 L/min (P less than 0.05). Corresponding values for stroke volume were 61 and 72 ml (P less than 0.05). The data suggest that in clinically stable patients there is an early improvement of the relation between myocardial oxygen supply and demand and a late improvement of functional capacity associated with increased stroke volume and cardiac output.

Left ventricular hemodynamics and function in acute myocardial infarction: studies during the acute phase, convalescence and late recovery

The left ventricular hemodynamics of 70 patients with acute myocardial infarction were determined from measurements of pulmonary arterial end-diastolic pressure, cardiac index, mean arterial pressure and heart rate during the acute phase(first study, 5 hours after admission), 4 to 6 weeks later (second study, during convalescence) and in 35 percent of all subjects 6 to 12 months after the acute infarction (third study). Serial analysis of serum creatine kinase was carried out during the acute phase. The peak CK value normalized for body surface area was used as a rough index of the extent of the acute myocardial necrosis. The condition of all survivors of the acute stage improved. Patients with only slightly reduced left ventricular performance during the acute stage recovered to nearly normal during convalescence. The condition of patients with greatly reduced left ventricular function also improved but remained impaired during convalescence. In all patients the main changes in left ventricular hemodynamics occurred within the first 4 to 6 weeks; there was almost no further alteration during the following 9 months.

Detection of pulmonary edema in acute myocardial infarction

To evaluate methods for detecting pulmonary edema, pulmonary extravascular water volume was measured at 24 hour intervals (total 72 hours) in 25 patients with acute myocardial infarction. Measured lung water was compared with results of clinical, blood gas, X-ray and hemodynamic methods for detecting pulmonary edema. Increased pulmonary extravascular water volume on one or more measurements was observed in 18 of the 25 patients and was associated with an abnormal chest radiograph and increased pulmonary arterial wedge, pulmonary arterial diastolic and right atrial pressures. It was associated less well with clinical, blood gas and other hemodynamic measurements. Pulmonary arterial diastolic or pulmonary wedge pressure was a significant predictor of lung water 24 hours later. Both "preclinical pulmonary edema" and the "therapeutic phase lag" could be predicted from the pulmonary wedge pressure. Clinical, blood gas, radiographic and other hemodynamic measurements were not predictive.

Serial measurements of left ventricular ejection fraction by radionuclide angiography early and late after myocardial infarction

The left ventricular ejection fraction was determined serially with radioisotope angiography in 63 patients with acute myocardial infarction. After the peripheral injection of a bolus of technetium-99m, precordial radioactivity was recorded with a gamma scintillation camera and the ejection fraction calculated from the high frequency left ventricular time-activity curve. Since this technique requires no assumptions with respect to left ventricular geometry, it is particularly useful in patients with segmental left ventricular dysfunction. Serial measurements during the first 5 days after hospital admission were made in 50 patients, 30 of whom were studied during the subsequent 2 to 39 months (mean 19.9 months). Late follow-up serial studies were also performed in an additional 13 patients who had only one measurement of the left ventricular ejection fraction during the early postinfarction period. Early after infarction, the left ventricular ejection fraction was normal (more than 0.52) in only 15 of the 63 patients, and averaged 0.52 +/- 0.05 (standard deviation) in the 27 patients with an uncomplicated infarct. The ejection fraction was reduced in 24 patients with mild to moderate left ventricular failure (0.40 +/- 0.05, P less than 0.0001) and in the 12 patients with overt pulmonary edema (0.33 +/- 0.07, P less than 0.0001). In 35 patients the ejection fraction correlated with the mean pulmonary arterial wedge pressure (r = 0.72). In 15 patients with normal left ventricular wall motion by heart motion videotracking, the ejection fraction was significantly higher (0.53 +/- 0.08) than in the 26 patients with regional left ventricular dysfunction (0.41 +/- 0.10, P less than 0.0001). During the early postinfarction period, the left ventricular ejection fraction improved in 55 percent of patients and remained unchanged or decreased in 45 percent. A further increase in the ejection fraction was noted in 61 percent of patients during the late follow-up period. Patients with an initially low or decreasing ejection fraction had a significantly greater incidence of early mortality and left ventricular dysfunction (P less than 0.02) than those whose ejection fraction was normal or improved to normal early after infarction. These data indicate that the ejection fraction is a sensitive indicator of left ventricular function after acute myocardial infarction and that serial measurements are helpful in predicting early mortality and morbidity.

Ventriculography and coronary arteriography in the acutely III patient. Complications, extent of coronary arterial disease, and abnormalities of left ventricular function

Of 99 patients who underwent "emergency" diagnostic studies, 82 had "unstable angina" (group A), 15 had recent myocardial infarction (group B), and two had intractable congestive heart failure due to acute mitral regurgitation (group C). Two cardiac and two local complications occurred either during the procedure or during the following 48 hours. There were no deaths or myocardial infarctions. Ten (12 percent) patients of group A had "normal" coronary arteries and normal left ventricular function; 13, 26 and 33 patients had one, two, and three coronary arteries involved, respectively. Those with three-vessel disease had a significantly higher left ventricular end-diastolic pressure (LVEDP) and lower ejection fraction (EF) than those with one- and two-vessel disease. Those with previous myocardial infarction had a significantly higher incidence of reduced EF and of wall motion abnormalities than those without a previous myocardial infarction. All patients in group B had significant coronary arterial disease, and 80 percent (12) had abnormal left ventricular function. Their mean LVEDP and EF were significantly higher and lower, respectively, than those found in group A. In conclusion, acutely ill patients were studied with low risk. Most patients had three- or two-vessel disease. Abnormal left ventricular function was related to three-vessel disease and to recent and old myocardial infarction.

THE HEMODYNAMIC SPECTRUM OF ACUTE MYOCARDIAL INFARCTION: A REVIEW AND IDENTIFICATION OF THE HIGH-RISK PATIENT

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