Correlative classification of clinical and hemodynamic function after acute myocardial infarction

Serum estrogen levels in men with acute myocardial infarction

Serum estradiol and serum estrone levels were assessed in 29 men in 14 men in whom myocardial infarction was ruled out; in 12 men without apparent coronary heart disease but hospitalized in an intensive care unit; and in 28 men who were not hospitalized and who acted as control subjects. (The 12 men who were hospitalized but who did not have coronary heart disease were included to control for physical and emotional stress of a severe medical illness.) Ages ranged from 21 to 56 years. Age, height, and weight did not differ significantly among groups. Blood samples were obtained in the patient groups on each of the first three days of hospitalization. The serum estrone level was significantly elevated in all four patient groups when compared with that in the control group. Estrone level, then, did not differentiate patients with and without coronary heart disease. Serum estradiol levels were significantly elevated in the groups with myocardial infarction, unstable angina, and in the group in whom myocardial infarction was ruled out. However, estradiol levels were not significantly elevated in the group in the intensive care unit without coronary heart disease when compared to the level in the normal control group. Serum estradiol levels, then, were elevated in men with confirmed or suspected coronary heart disease but were not elevated in men without coronary heart disease even under the stressful conditions found in an intensive care unit. Serum estradiol levels were significantly and positively correlated (p less than 0.03) with serum total creatine phosphokinase levels in the patients with myocardial infarction. The five patients with myocardial infarction who died within 10 days of admission had markedly elevated serum estradiol levels. The potential significance of these serum estradiol elevations is discussed in terms of estradiol's ability to enhance adrenergic neural activity and the resultant increase in myocardial oxygen demand.

Evaluation of changes in left ventricular end-diastolic pressure by left atrial two-dimensional echocardiography

Two-dimensional echocardiography (2DE) measurements of left atrial (LA) cross-sectional areas were compared in closed-chest dogs with concurrent high-fidelity recordings of left ventricular end-diastolic pressure (LVEDP) measurements. One hundred forty-three simultaneous determinations of LVEDP and end-diastolic as well as end-systolic LA cross-sectional areas were obtained in eight dogs during control, after coronary artery occlusion, and following alterations in LV preload and afterload. Correlation coefficients for LVEDP versus LA end-diastolic cross-sectional area ranged from 0.85 to 0.97 in the eight dogs, with standard errors of estimate from 1.89 to 5.43 mm Hg. These findings suggest that 2DE measurements of changes in LA size may facilitate noninvasive evaluation of alterations in LVEDP in patients with LV failure or undergoing interventions.

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.

Role of vasodilators in the changing phases of acute myocardial infarction

Application of vasodilators in evolving myocardial infarction has not yet received wide acceptance. Heretofore, clinical trials of a variety of vasodilator agents have been conducted without regard to the phase of the disease with its changing pathologic features and altering cardiac function. A classification of these phases based on the underlying myocardial disease--ischemia, necrosis, compensation, and healing--may allow a more rational interpretation of the available information. At present, vasodilators are not recommended during the ischemic phase, although some evidence suggests that preload modification by use of nitroglycerin may be beneficial in certain instances. Vasodilator drugs productive of arterial impedance reduction are probably of the greatest value late in the necrotic phase and in the compensation and healing phases. It is in these circumstances that heart failure becomes clinically manifest and maximal short-term efficacy of this intervention can be achieved. Impedance reduction, using agents such as sodium nitroprusside, will cause a prompt improvement manifested by a reduction in left ventricular filling pressure and in pulmonary congesting pressure and an increase in cardiac output. A significant improvement in short-term survival, at least, should be expected by judicious use of vasodilators.

Prognostic implications of reduction of left ventricular filling pressure in early transmural acute myocardial infarction

The left ventricular filling pressure (LVFP) was measured within 12 hours of onset of acute myocardial infarction (AMI) in 99 patients, including 21 nonsurvivors. Initial LVFP for survivors was 18 +/- 6 mm Hg (mean +/- SD) and for nonsurvivors was 24 +/- 8 mm Hg (p less than 0.005). Of the total population, 87% had initial LVFP of 12 mm Hg or greater and all nonsurvivors were in this group. Life table analysis was employed to determine LVFP related mortality rates. If initial LVFP was less than or equal to 18 mm Hg, 72-hour mortality rate was 4% and 30-day mortality rate was 10%. For initial LVFP greater than 18 mm Hg, 72-hour mortality rate was 21% and 30-day mortality rate was 33% (p less than 0.005 for both 72 hours and 30 days). When final LVFP was analyzed 30-day mortality rate for final LVFP less than or equal to 18 mm Hg was 5%. Mortality rate of 60% was observed for final LVFP greater than 18 mm Hg. We compared sequential measurements of LVFP in a subset of survivors and nonsurvivors and observed that long-term average trend was for survivors to decrease their LVFP. We conclude that AMI mortality rate is related to LVFP and that LVFP greater than 18 mm Hg is associated with very high mortality rate when compared to LVFP less than or equal to 18 mm Hg. Thus reduction of LVFP either spontaneously or as result of therapy may lower AMI mortality rate.

Left ventricular diastolic pressure-volume relations in rats with healed myocardial infarction. Effects on systolic function

To determine the effects of healed myocardial infarction on the diastolic compliance of the left ventricle, we studied 36 rats 26 days after left coronary artery ligation. Peak cardiac output and stroke volume were measured under ether anesthesia during volume loading, and peak left ventricular developed pressure was determined during occlusion of the ascending aorta. During a slow infusion of saline into the potassium-arrested left ventricle, diastolic pressure and volume were measured continuously over the pressure range -5 to 30 mm Hg. Infarct size was determined by planimetry of serial sections taken from each heart at 1-mm intervals from apex to base. In rats with healed infarcts, left ventricular volume was increased in proportion to infarct size and the diastolic pressure-volume relationship was shifted so that at pressures below 2.5 mm Hg volume was increased, resulting in an increased ventricular compliance in this low pressure range. Above this pressure, the slopes of the pressure-volume curves were similar in rats with and without infarctions. Peak cardiac output and pressure-generating capacity were impaired in proportion to infarct size. This impairment of cardiac performance correlated with the infarct size-related increase in diastolic volume, which served to offset the reduction in flow generating capacity caused by systolic dysfunction, while contributing directly to the impairment of pressure generating capacity.

Randomized controlled trial of vasodilator therapy after myocardial infarction

Hemodynamic changes and mortality and morbidity were compared in a randomized controlled trial of sodium nitroprusside after acute myocardial infarction. Fifty patients with a mean pulmonary capillary wedge pressure of more than 20 mm Hg within 24 hours of acute infarction were randomly assigned to one of two groups: 25 patients treated with nitroprusside and 25 treated with furosemide. Nitroprusside rapidly produced a sustained decrease in systemic vascular resistance and increase in cardiac index (thermodilution). After 1 hour the cardiac index had increased 16 +/- 3 (mean +/- standard error of the mean) percent (p less than 0.001) compared with a decrease of 7 +/- 3 percent with administration of furosemide (p less than 0.01). Differences in systemic vascular resistance and cardiac index in the two groups persisted throughout the 48 hour treatment period (p less than 0.001). Pulmonary capillary wedge pressure decreased rapidly with nitroprusside and slowly with furosemide so that, although it was significantly lower in the former group overall (p less than 0.001), by 48 hours the values were not different. Although beneficial acute hemodynamic effects of nitroprusside were demonstrated, there was no difference in mortality or in morbidity assessed clinically, by chest X-ray film, echocardiogram or graded treadmill stress testing after 6 months or 1 year.

Ventricular compliance in ischemic right ventricular dysfunction

Ischemic right ventricular dysfunction was diagnosed in 54 patients with acute myocardial infarction who had a right atrial pressure disproportionately increased in relation to the pulmonary capillary pressure. The right atrial pressure curve in 40 patients (74 percent) was M- or W-shaped, termed a noncompliant pattern, and was similar to the pattern found in constrictive pericarditis. Kussmaul's sign was found in the patients whose respiration was recorded. This pattern, which represents poor right ventricular compliance, was severe in 30 cases (y descent greater than x descent) and slight in 10 cases (y descent = x descent). Its duration was variable, ranging from days to years. Of the 54 patients, 32 (59 percent) had a low output syndrome, diagnosed in the presence of a cardiac index of less than 2.2 liters/min per m2, with signs of poor tissue perfusion. The severe noncompliant pattern was significantly related to the presence of a low output syndrome (p less than 0.01) and mortality from this cause (p less than 0.05). The jugular venous tracing pulse had a pattern similar to that of the right atrial pressure recording and therefore may be valuable in the noninvasive diagnosis of right ventricular dysfunction and in the study of the evolution of the noncompliant pattern and, hence, of ventricular compliance.

Low output syndrome in right ventricular infarction

In this paper we describe clinical and hemodynamic data in ten patients with right ventricular infarction and low output syndrome. Atrioventricular block and supraventricular arrhythmias were a common finding. All of them had a right atrial pressure disproportionately increased (average 16.3 +/- 5.2 mm. Hg) in relation to left ventricular filling pressure (average 15 +/- 4.5 mm. Hg), and a very low cardiac index (average 1.42 +/- 0.45 liters/min./m.2). The right atrial pulse tracings were similar to those of constrictive pericarditis, showing a deep "y" descent in every patient. We made the differential diagnosis between similar hemodynamic entities and constructed function curves of right and left ventricles. Right ventricular diastolic work index was always increased (average 6.26 +/- 3.63 gm./beat/M.2), being higher than net work index (average 3.28 +/- 1.87 gm./beat/M.2). While all function curves of the right ventricle were flat or depressed, those of the left ventricle were very different. Treatment consisted mainly of fluid overload and, in some cases, of vasodilators or dopamine. Mortality rate was 40%. We think that coexisting left ventricular damage may account in part for the bad prognosis of these patients.

Effects of beta 2-adrenoceptor stimulation on cardiac metabolism in the conscious dog

1 The effects of the beta 2-adrenoceptor stimulant, salbutamol, on cardiac metabolism have been studied in conscious mongrel dogs. The potential effects of anaesthesia on the study of cardiac metabolism have been avoided by prior implantation of arterial (A) and coronary sinus (CS) catheters for blood sampling and a central venous catheter for infusion. Extraction of substrates for myocardial energy metabolism (CA-CS) was assessed 3 to 24 days post-operatively. A 100 micrograms bolus of salbutamol was given followed by an infusion of 3 micrograms/min for 1 h. 2 Although heart rate increased significantly from 106 to 165 beats/min, fractional extraction of oxygen tended to fall from 84% to 77%. Thus an increase in coronary blood flow rather than in oxygen extraction must have maintained an oxygen supply commensurate with the salbutamol-induced tachycardia. 3 Neither CA-CS glucose nor fractional glucose extraction altered significantly during salbutamol infusion despite increases in arterial concentration (CA) of glucose and arterial insulin immunoreactivity and a decrease in CA of free fatty acids (FFA). This suggests that an insulin-antagonistic action accompanies the infusion of salbutamol. 4 The fractional extraction of lactate increased during salbutamol infusion. In part, this may have been a reflection of a decreased myocardial extraction of FFA with salbutamol in this model.

Management of the patient with myocardial infarction

Coronary atherosclerotic heart disease and myocardial infarction constitute an epidemic in this century, mandating that the primary care physician be familiar with their recognition and management. However, in recent decades, an improved understanding of pathophysiologic alterations, an enormous advance in technology and significant accomplishments in pharmacology and operative procedures have virtually revolutionized the management of patients with myocardial infarction. Although patterns of care described in this monograph may well be obsolete a few years hence, to be superseded by safer, more precise, more efficient and more cost-effective therapeutic modalities, nevertheless basic principles underlying the management of the patient with myocardial infarction remain as appropriate guidelines. In the hospital phase, efforts should be directed toward enhancing survival, saving myocardium and restoring function. The long-term ambulatory care should be designed to maintain functional capacities, to control symptoms, to retard or arrest the atherosclerotic process thus decreasing the likelihood of recurrent myocardial infarction and/or of sudden cardiac death and to restore the patient to a normal or near-normal life style.

Hemodynamic monitoring in patients with hypotension after myocardial infarction. The role of the medical center in relation to the community hospital

Patients who develop hypotension after acute myocardial infarction are frequently transferred to medical centers for hemodynamic monitoring. To see if this practice is justified, we reviewed our experience with hemodynamic monitoring over a two-year period. Of 40 patients who underwent hemodynamic monitoring for hypotension, 28 were transferred from other institutions. Eleven (39 percent) of these 28 patients had a pulmonary capillary wedge pressure of 16 mm Hg or less. Ten (91 percent) of these 11 survived, compared with one survivor (8 percent) in the 13 transferred patients with a pulmonary capillary wedge pressure of 17 mm Hg or more (P less than 0.001). The pulmonary capillary wedge pressure did not correlate well with the presence of a third heart sound on physical examination or with chest x-ray films. All hypotensive patients with a low pulmonary capillary wedge pressure received fluids to expand the blood volume as their major form of therapy. Thus, hemodynamic monitoring in patients with hypotension clarifies their status regarding blood volume and identifies those who will benefit from expansion of this volume. Transfer of hypotensive patients for hemodynamic monitoring seems justified, as their status regarding volume of blood is frequently difficult to ascertain by noninvasive means.

Hospital treatment of congestive heart failure. Management according to hemodynamic profile

Selection of therapy for subjects with acute congestive dardiac failure usually involves a choice among a diuretic, a vasodilator and an inotropic agent. Three principal questions are involved in the decision: (1) Is cardiac out normal or depressed? (2) Is blood pressure normal or depressed? (3) is regional myocardial ischemia present? Diuretics are safe and easy to administer, but they do not increase cardiac output or relieve hypoperfusion. Inotropic agents increase cardiac output but differ widely in their effects on blood pressure: selection of specific agents is influenced by their blood pressure effect. All inotropic agents, however, potentially aggravate regional myocardial ischemia. In ischemic heart failure, therefore, vasodilators which also increase cardiac output, may be chosen. Vasodilator administration is in turn limited by the decrease in arterial pressure which accompanies increasing infusion rate. When these three questions are considered in combination, an effective therapeutic regimen can be identified. Thus, congestion without hypoperfusion requires a diuretic if blood pressure is normal; and a vasodilator when blood pressure is increased. In the presence of congestion with hypoperfusion, a vasodilator is employed if blood pressure is normal; and a positive inotropic drug when blood pressure is depressed.

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.

Principles of pre-operative fluid therapy and resuscitation

The pre-operative preparation of a patient for elective surgery requires correction of all major electrolyte abnormalities, osmolality and body fluid compartment excesses of deficits. For the emergency surgical procedure however, only stability of the cardiovascular system is required before the induction of anaesthesia. To facilitate rapid correction of the abnormal haemodynamic state a set of physiological principles are described which aim to simplify therapy.