Intravenous isosorbide dinitrate in patients with refractory pump failure and acute myocardial infarction

Short-term intravenous sodium nitrite infusion improves cardiac and pulmonary hemodynamics in heart failure patients

BACKGROUND

Nitrite exhibits hypoxia-dependent vasodilator properties, selectively dilating capacitance vessels in healthy subjects. Unlike organic nitrates, it seems not to be subject to the development of tolerance. Currently, therapeutic options for decompensated heart failure (HF) are limited. We hypothesized that by preferentially dilating systemic capacitance and pulmonary resistance vessels although only marginally dilating resistance vessels, sodium nitrite (NaNO2) infusion would increase cardiac output but reduce systemic arterial blood pressure only modestly. We therefore undertook a first-in-human HF proof of concept/safety study, evaluating the hemodynamic effects of short-term NaNO2 infusion.

METHODS AND RESULTS

Twenty-five patients with severe chronic HF were recruited. Eight received short-term (5 minutes) intravenous NaNO2 at 10 μg/kg/min and 17 received 50 μg/kg/min with measurement of cardiac hemodynamics. During infusion of 50 μg/kg/min, left ventricular stroke volume increased (from 43.22±21.5 to 51.84±23.6 mL; P=0.003), with marked falls in pulmonary vascular resistance (by 29%; P=0.03) and right atrial pressure (by 40%; P=0.007), but with only modest falls in mean arterial blood pressure (by 4 mm Hg; P=0.004). The increase in stroke volume correlated with the increase in estimated trans-septal gradient (=pulmonary capillary wedge pressure-right atrial pressure; r=0.67; P=0.003), suggesting relief of diastolic ventricular interaction as a contributory mechanism. Directionally similar effects were observed for the above hemodynamic parameters with 10 μg/kg/min; this was significant only for stroke volume, not for other parameters.

CONCLUSIONS

This first-in-human HF efficacy/safety study demonstrates an attractive profile during short-term systemic NaNO2 infusion that may be beneficial in decompensated HF and warrants further evaluation with longer infusion regimens.

Nitrate therapy is an alternative to furosemide/morphine therapy in the management of acute cardiogenic pulmonary edema

BACKGROUND

Nitrates are superior to furosemide in the management of acute pulmonary edema associated with myocardial infarction; however, their role in the absence of infarction is unclear.

METHODS AND RESULTS

A randomized comparison was undertaken of the relative effectiveness of primary therapy with either intravenous morphine/furosemide (men/women; n = 32) or nitroglycerin/N-acetylcysteine (NTG/NAC; n = 37) in consecutive patients with acute pulmonary edema. The primary end point was change in PaO2/FIO2 over the first 60 minutes of therapy. Secondary end points were needed for mechanical respiratory assistance (ie, continuous positive airway pressure via mask or intubation and ventilation) and changes in other gas exchange parameters. Both treatment groups showed improvement in oxygenation after 60 minutes of therapy; however, this reached statistical significance only with NTG/NAC therapy. There was no significant difference between groups in the assessed parameters (95% CI for differences in Pao2/FIO2: furosemide/morphine -12 to 23 and NTG/NAC 4 to 44), a finding also confirmed in 32 patients presenting with respiratory failure. Only 11% of the study group required mechanical ventilatory assistance (continuous positive airway pressure in 4 patients and intubation and ventilation in 3 patients).

CONCLUSIONS

NTG/NAC therapy is as effective as furosemide/morphine in the initial management of acute pulmonary edema, regardless of the presence or absence of respiratory failure. The necessity for mechanical ventilatory assistance is infrequent in these patients, regardless of the initial medical treatment regimen.

Enalaprilat decreases plasma endothelin and atrial natriuretic peptide levels and preload in patients with left ventricular dysfunction after cardiac surgery

OBJECTIVE

To study the acute effects of angiotensin-converting enzyme inhibition by intravenous enalaprilat infusion in patients with left ventricular dysfunction after cardiac surgery.

DESIGN

Prospective, consecutive sample, before-after trial.

SETTING

Surgical intensive care unit in a tertiary care university hospital.

PARTICIPANTS

Eight patients with left ventricular dysfunction after cardiac surgery. Patients were defined as having left ventricular dysfunction if the pulmonary capillary wedge pressure persisted above 18 mmHg in spite of conventional vasoactive medication (inotropic or vasodilating and diuretic drugs) and intermittent mandatory ventilation during the first postoperative week.

INTERVENTIONS

Enalaprilat was infused initially at 1 mg/ hour. The rate was doubled every 30 minutes until pulmonary capillary wedge pressure decreased at least 20% or until a maximum total dose of 10 mg was achieved.

MEASUREMENTS AND RESULTS

Central hemodynamics, systemic oxygenation, and hormonal regulation of circulation (plasma renin activity, plasma endothelin, atrial natriuretic peptide, norepinephrine, epinephrine, and vasopressin concentrations, serum angiotensin-converting enzyme activity, and serum levels of aldosterone) were assessed at baseline before enalaprilat infusion, and repeatedly over 2 hours after the infusion. Enalaprilat infusion (median dose, 2.0 mg; infusion time, 48 minutes) caused a significant decrease in pulmonary capillary wedge pressure (p = 0.004), lasting until the end of the 2 hours' follow-up. This coincided with inhibition of serum angiotensin-converting enzyme activity (p < 0.001), an increase in plasma renin activity (p = 0.022), and decreases in plasma endothelin (p = 0.035), atrial natriuretic peptide (p = 0.005), and serum aldosterone (p = 0.001) concentrations. Cardiac output, venous admixture, and oxygen delivery and consumption remained unchanged.

CONCLUSIONS

Adding enalaprilat to conventional therapy makes it possible to unload the left ventricle and to relieve overt neurohormonal activation temporarily while maintaining cardiac function and systemic oxygenation.

Failure of captopril to prevent nitrate tolerance in congestive heart failure secondary to coronary artery disease

The possible role of angiotensin-converting enzyme inhibition in preventing or minimizing tolerance to intravenous nitroglycerin in severe congestive heart failure (CHF) was studied by quantitating the degree of tolerance in 12 patients receiving nitroglycerin (group 1) and in 9 patients (group 2) receiving nitroglycerin and concurrent treatment with captopril (60 +/- 29 mg/day). At peak effect, nitroglycerin produced almost identical hemodynamic changes in both groups, with significant decreases in right atrial and pulmonary arterial wedge pressure, systolic blood pressure and systemic and pulmonary vascular resistances. Cardiac index increased. The extent of nitrate tolerance was calculated for each hemodynamic parameter as the percentage loss of the peak effect achieved by the drug. At 24 hours, 98 +/- 80% of the benefit achieved with respect to right atrial pressure was lost in group 1 and 61 +/- 74% in group 2 (group 1 vs 2, difference not significant). For pulmonary arterial wedge pressure, 51 +/- 31% (group 1) and 85 +/- 53% (group 2) (difference not significant) of the effect was lost, and for cardiac index, 53 +/- 58% (group 1) and 54 +/- 44% (group 2) (difference not significant). Tolerance was also almost identical regarding systolic blood pressure and systemic and pulmonary vascular resistance. Thus, the extent of tolerance to high-dose intravenous nitroglycerin in CHF was unaltered by administration of captopril, indicating that in clinical dosage, counter-regulatory neurohumoral mechanisms involving the renin-angiotensin system appear to be unimportant in its development.

Acute preload effects of furosemide

Acute preload effects (as reflected by the pulmonary capillary wedge pressure [PCWP]) of an intravenous furosemide bolus were studied in 33 patients. In those patients receiving no vasoactive drug and in those receiving predominantly preload reducing agents, there was an initial rise in PCWP up until 15 minutes followed by a diuresis-induced fall in PCWP below baseline levels at 1 h. Patients who were receiving preload and significant afterload reduction showed an immediate drop in PCWP which was sustained. This trend is independent of underlying pathology or dose of furosemide used. It is postulated that furosemide causes an early deleterious release of endogenous vasoconstrictors which may be blocked by combined preload and afterload reduction.

Nitrates: why and how should they be used today? Current status of the clinical usefulness of nitroglycerin, isosorbide dinitrate and isosorbide-5-mononitrate

Nitrates are highly effective both in terminating acute attacks of angina pectoris and in the prophylaxis of symptomatic and asymptomatic myocardial ischemia. Preload reduction by venodilatation is the prevailing mechanism of nitrates in patients with chronic stable angina and is the unique feature distinguishing them from beta and calcium-channel blockers. Nitrates dilate coronary arteries not only in pre- and poststenotic vessels, but also in eccentric lesions. In patients with endothelial dysfunction, nitrates seem to be the physiological substitute for endothelium-derived relaxing factor. During the past decade, however, there has been substantial evidence of a clinically relevant loss of the anti-ischemic effects ("nitrate tolerance"). Many studies with oral dosing of isosorbide dinitrate or isosorbide-5-mononitrate at least three times daily have proven nitrate tolerance in patients with coronary artery disease and/or congestive heart failure. Complete loss of anti-ischemic effects after repetitive, continuous patch attachments has also been found. As we first showed in 1983, intermittent therapy with once-daily ingestion of high-dose sustained-release isosorbide dinitrate was successful in preventing the development of tolerance. Similarly, tolerance to isosorbide-5-mononitrate also does not develop when it is ingested once daily. It is now generally accepted that a daily low-nitrate interval is required to prevent tolerance development. Although the minimal patch-free interval required to prevent tolerance needs further investigation, a 12-h patch-free interval should prevent tolerance in most patients. The prolonged duration of action of once-daily high-dosage administration of sustained-release formulations, the improved patient compliance with a single daily administration, and the increased likelihood of maximal anti-ischemic effects are important reasons for recommending high single daily doses of isosorbide dinitrate or isosorbide-5-mononitrate.

Effect of isosorbide dinitrate on cardiac output in severe cardiac failure: relation to initial hemodynamics, ventricular volume, and the preload reserve mechanism

Isosorbide dinitrate (ISDN) improves the clinical and hemodynamic state of patients with heart failure, but may cause dizziness and syncope. To characterize patients in whom cardiac output falls with high-dose nitrate therapy and to examine further the pathophysiology of the fall in cardiac output in these patients, we studies the effect of sublingual ISDN on forward cardiac output in 14 patients with severe cardiac failure (New York Heart Association grades 3-4). We examined systolic and diastolic left ventricular (LV) function from pressure and volume analyses of LV function. After administration of 15 mg ISDN, cardiac output was either unaltered or increased in 7 patients (Group 1) (11 +/- 12%, mean +/- SD), and decreased in 7 (Group 2) (-13 +/- 10%) (Group 1 vs. 2, p less than 0.002). Initial systemic arterial pressure, LV ejection fraction, wedge and LV transmural filling pressures were similar in both groups, but Group 2 patients had a lower systemic vascular resistance (p = 0.07) and tended to have a larger initial LV end-diastolic volume and increased end-diastolic compliance; following ISDN the decrease in LV filling pressure and end-diastolic volume was larger and the product of the changes greater (p less than 0.02). Thus ISDN decreases filling pressure and improves forward cardiac output in some patients with congestive heart failure, but large doses may decrease cardiac output in a subset of patients who have a lower systemic vascular resistance and a larger more compliant ventricle, maintaining forward blood flow predominantly by a preload reserve mechanism.(ABSTRACT TRUNCATED AT 250 WORDS)

Emergency treatment of severe cardiogenic pulmonary edema with intravenous isosorbide-5-mononitrate

Intravenous isosorbide-5-mononitrate (IS-5-MN) was administered to 24 patients, mean age 73, with severe respiratory distress after pulmonary edema and acute left heart failure. The condition was due to ischemic cardiopathy in 18 patients (4 with acute myocardial infarctions), congestive cardiomyopathy in 3, hypertensive cardiopathy in 2, and mitral valvular disease in 1. Therapy consisted of an intravenous (i.v.) bolus dose of IS-5-MN, followed by a continuous infusion (mean 8 mg/hour over 24 hours) of i.v. furosemide and additional oxygen. Clinical data were recorded as well as blood gas values and repeated chest radiographs. All patients survived and improved markedly; only 6 needed mechanical ventilation. Most patients had fast respiratory relief, with no untoward reaction, except a brief decrease of blood pressure in a ventilated patient taking morphine. These data indicate that i.v. IS-5-MN is effective and safe for the management of severe acute cardiogenic pulmonary edema.

Effect of intravenous isosorbide dinitrate versus nitroglycerin on elevated pulmonary arterial wedge pressure during acute myocardial infarction

To compare the acute and sustained effect of intravenous isosorbide dinitrate to intravenous nitroglycerin in patients with acute myocardial infarction and elevated pulmonary artery wedge pressure, 111 patients were randomized and studied within 96 hours of admission to the coronary care unit. All patients had a pulmonary artery wedge pressure greater than or equal to 10 mm Hg and received either isosorbide dinitrate (74 patients) or nitroglycerin (37 patients) for 24 to 48 hours. Blood pressure, heart rate, pulmonary artery wedge pressure, cardiac output, medication dose in micrograms per minute and retitration episodes were compared at baseline and at 6, 12, 18 and 24 hours. Both drugs significantly (p less than 0.05) lowered pulmonary artery wedge pressure and blood pressure and increased cardiac output. Isosorbide dinitrate required fewer retitration episodes and less increases in dosage than nitroglycerin at 24 hours. In the patient with acute myocardial infarction complicated by high pulmonary artery wedge pressure who requires intravenous nitrates for 24 hours, isosorbide dinitrate may offer the benefit of a more stable hemodynamic effect.

Hemodynamic effects of oral isosorbide-5-mononitrate and dinitrate in ischemic heart failure

Isosorbide-5-mononitrate (ISMN), the main metabolite of isosorbide dinitrate (ISDN) was recently introduced in clinical use. The hemodynamic effects of oral ISMN and ISDN, administered in equal doses, were studied in a randomized, crossover fashion in 20 patients with pump failure of ischemic etiology. Baseline hemodynamic criteria for admission into the study were: pulmonary capillary wedge pressure (PCW) of at least 20 mmHg and systolic arterial pressure (AP) above 90 mmHg. Hemodynamic parameters were serially measured and systemic vascular resistance was calculated up to 6 h postadministration of either ISMN or ISDN single dose (40 mg). Maximal effects obtained were statistically significantly different from baseline. While ISMN and ISDN appeared to be equipotent in reducing the filling pressure, with a maximum effect reached in 60-120 min, the mononitrate maintained its effects for a longer period.

The effect of isosorbide dinitrate on the arterial vascular bed: a dose response study in dogs

Isosorbide dinitrate (ISDN) was infused stepwise intraarterially into the left hindlimb (5.7-364.8 micrograms/kg/min.) into six dogs. The mean local vascular resistance was decreased by 32% in the left hindlimb after a dose of up to 91.2 micrograms/kg/min. corresponding to a 1.6-fold increase in the left femoral artery blood flow, without significant changes in the control limb or central haemodynamics. The muscular blood flow in the adductor magnus muscle obtained by the Xenon washout technique remained unchanged in 6 of 7 other dogs at ISDN infusion rates of 91.2 micrograms/kg/min., indicating that the increase in femoral artery blood flow was not a consequence of increased muscular blood flow. The arterio-venous extraction fraction of radioactive microspheres was lower in the experimental leg during ISDN infusion when compared with the control leg, suggesting that AV-shunts are opened during ISDN infusion. In addition to the well-known effect on preload, the present results confirm that ISDN also acts on afterload. Thus, ISDN may be classified as a mixed agent acting on both pre- and afterload which is in agreement with some previous studies.

Hemodynamic effects of intravenous isosorbide dinitrate and nitroglycerine in acute myocardial infarction and elevated pulmonary artery wedge pressure

We compared in a randomized fashion the hemodynamic effects of intravenous (IV) isosorbide dinitrate (ISDN) and nitroglycerine (NTG) in 45 patients with acute myocardial infarction and elevated pulmonary artery wedge pressure (Paw). Titration of ISDN dose to lower Paw greater than or equal to 25 percent resulted in a fall of this parameter from 32 +/- 8 to 24 +/- 5 mm Hg and was associated with a fall in mean blood pressure (96 +/- 15 to 90 +/- 14 mm Hg, p less than 0.05), systemic vascular resistance (1715 +/- 572 to 1548 +/- 414 dynes X s X cm-5, (p less than 0.05), pulmonary vascular resistance (182 +/- 106 to 154 +/- 78 dynes X s X cm-5, p less than 0.05) and mean right atrial pressure (11 +/- 4 to 7 +/- 4 mm Hg, p less than 0.05). In addition, ISDN significantly (p less than 0.05) increased cardiac index from 2.37 +/- 0.54 to 2.54 +/- 0.59 L/min/m2, stroke volume index from 28 +/- 8 to 31 +/- 8 ml/m2, and stroke work index from 28 +/- 11 to 31 +/- 12 g X m/m2. The ISDN dose ranged from 50 to 533 micrograms/min (mean +/- SD 326 +/- 176 micrograms/min) and could not be predicted from baseline hemodynamic values. A comparison between the effect of ISDN and NTG in doses producing comparable reduction in Paw showed similar hemodynamic changes. It was concluded that IV ISDN in patients with elevated mean pulmonary artery wedge pressure due to acute myocardial infarction results in a decrease in right and left ventricular preload and afterload and improvement of cardiac output and cardiac work. The effective dose ranges from 50 to 533 micrograms/min and cannot be predicted from baseline hemodynamic values. In doses producing comparable reduction in Paw, ISDN and NTG had similar hemodynamic effects.

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.

Alterations in myocardial perfusion during exercise after isosorbide dinitrate infusion in patients with coronary disease: assessment by thallium-201 scintigraphy

We studied the effect of intravenous isosorbide dinitrate (ISDN) on myocardial perfusion of patients with coronary artery disease, by using exercise thallium-201 (TI-201) myocardial scintigraphy. A control study was conducted initially to assess regional myocardial perfusion rate. Left ventricular myocardium was divided into six parts: anterior, lateral, apical, inferior, posterior, and septal segments. The segmental myocardial perfusion was characterized according to TI-201 initial uptake index (IUI) of relative distribution and redistribution index (RDI) of TI-201 washout. The normal limit of IUI and RDI was established from the data of 17 persons with normal coronary arteries, and then the IUI less than or equal to 84% and the RDI greater than or equal to 1.12 was defined as abnormal. Based on IUI and RDI, each segment was characterized into three types: A type = IUI less than or equal to 84%, RDI greater than or equal to 1.12; B type = IUI less than or equal to 84%, RDI less than 1.12; and C type = IUI greater than 84%, RDI less than 1.12. ISDN was given as a dose of 0.1 mg/kg/hr, and then treadmill testing was repeated for the same duration of exercise time using the same protocol as in the control period. The segments of A type showed a significant improvement in IUI and RDI after receiving ISDN infusion, while the B and C type segments showed no change. It was also shown that the improvement of IUI and RDI of the A type segments was not as marked in multivessel disease as in cases of single-vessel disease.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of molsidomine on hemodynamics and blood gases in acute myocardial infarction with left heart failure

We studied the effects of molsidomine on hemodynamic properties and blood gas levels in eight patients with acute myocardial infarction and left heart failure. One hour after an 8 mg intravenous bolus injection, pulmonary wedge pressure and right atrial pressure decreased, respectively, from 30 +/- 9 to 23 +/- 12 mm Hg (p less than 0.01) and from 10.4 +/- 3.6 to 7.8 +/- 4.0 mm Hg (p less than 0.05) without significant changes in heart rate, cardiac index, or systemic blood pressure. There was a mild decrease in arterial oxygen tension (from 61 +/- 15 to 56 +/- 6 mm Hg), but it was not significant. The drug induced no adverse effects. Intravenous bolus injection of molsidomine rapidly relieves pulmonary congestion in patients with acute myocardial infarction.

Hemodynamic comparison of primary venous or arteriolar dilatation and the subsequent effect of furosemide in left ventricular failure after acute myocardial infarction

The hemodynamic effect of venous dilatation (intravenous isosorbide dinitrate [ISDN]) and arteriolar dilatation (intravenous hydralazine), both as firstline treatment and then combined with intravenous furosemide, were evaluated in a randomized, between-group comparison in 20 men with severe acute left-sided cardiac failure after myocardial infarction (MI). Both ISDN (50 to 200 micrograms/kg/hour) (Group 1) and hydralazine (0.15 mg/kg) (Group 2) reduced systemic arterial pressure (p less than 0.05) and vascular resistance (p less than 0.05). Pulmonary artery occluded pressure was reduced (p less than 0.01) only by ISDN, whereas heart rate (p less than 0.01), cardiac output (p less than 0.01) and stroke volume (p less than 0.05) were increased only after hydralazine. After ISDN, furosemide (1 mg/kg) decreased left-sided cardiac filling pressure by 1 mm Hg (p greater than 0.05), whereas after hydralazine, furosemide in a similar dose reduced pulmonary artery occluded pressure by 5 mm Hg (p less than 0.01). In both groups of patients, furosemide transiently increased systemic arterial pressure (p less than 0.05). Cardiac output was reduced (p less than 0.05) and systemic vascular resistance increased (p less than 0.05) in Group 1 patients after furosemide. Similar changes in both variables in Group 2 patients did not attain statistical significance. In conclusion, ISDN-induced venous dilatation is preferable to primary arteriolar dilatation by hydralazine as first-line treatment in acute left-sided cardiac failure. However, hydralazine and furosemide in combination were equally effective in reducing pulmonary artery occluded pressure and increasing cardiac output. The influences of each regimen on prognosis await further investigation.

Hemodynamic and myocardial performance characteristics after verapamil use in congestive heart failure

Because of its intrinsic negative inotropic effect, the administration of the recently introduced calcium antagonist, verapamil, is thought to be contraindicated in presence of congestive heart failure (CHF). Yet, as CHF is frequently associated with arrhythmias and angina pectoris, and verapamil possesses potent antiarrhythmic and antianginal properties that could be of great benefit to selected patients with CHF, this study was undertaken to determine whether verapamil can be given to such subjects safely. For this purpose, 14 patients with CHF were studied in the control (preverapamil) state with a combined hemodynamic-cineangiographic approach; the same interventions were repeated during intravenous verapamil administration (0.1 mg/kg bolus, followed by 0.005 mg/kg/min infusion). Verapamil markedly lowered mean aortic pressure (95 +/- 19 to 81 +/- 12 mm Hg, p less than 0.001) and systemic vascular resistance (1,953 +/- 873 to 1,417 +/- 454 dynes s cm-5, p less than 0.01). Simultaneously, indexes of left ventricular (LV) performance substantially improved: the ejection fraction increased from 29 +/- 13 to 37 +/- 17% (p less than 0.01), and mean velocity of circumferential fiber shortening increased from 0.45 +/- 0.18 to 0.64 +/- 0.28 circ/s (p less than 0.001). Cardiac index also increased (from 1.98 +/- 0.49 liters/m2/min before verapamil to 2.24 +/- 0.60 liters/m2/min after verapamil), although this improvement did not become statistically significant. No appreciable changes were noted in the heart rate, LV end-diastolic pressure, or mean pulmonary arterial or pulmonary capillary wedge pressure. Thus, the intrinsic negative inotropic activity of intravenous verapamil in therapeutic doses generally does not represent a serious drawback even in patients with CHF; its potent unloading vasodilatory properties more than compensate for any intrinsic decrease in LV contractility, and can thereby actually improve overall cardiac function.

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.