Treatment of cardiogenic shock in myocardial infarction by intraaortic balloon counterpulsation surgery

Cardiogenic shock: a historical perspective

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

NONARRHYTHMIC COMPLICATIONS OF ACUTE MYOCARDIAL INFARCTION

Complications of acute myocardial infarction can be categorized as nonarrhythmic or arrhythmic; the latter is discussed elsewhere. Patients are at risk for a number of potentially serious or fatal complications during or after the acute infarction phase. These include shock, left ventricular free wall rupture, rupture of the interventricular septum, papillary muscle rupture, ventricular pseudoaneurysm, and stroke. Right ventricular infarction, which is typically associated with inferior myocardial infarction, will also be discussed.

Efficacy of invasive strategy for the management of acute myocardial infarction complicated by cardiogenic shock

This retrospective study evaluates the influence of an invasive strategy of urgent coronary revascularization on the in-hospital mortality of patients with acute myocardial infarction (AMI) complicated early by cardiogenic shock. Among 1,981 patients with AMI admitted to our institution from 1994 to 1997, 162 patients (8.2%) developed cardiogenic shock unrelated to mechanical complications. The strategy of management was considered invasive if an urgent coronary angiography was indicated within 24 hours of symptom onset. Every other strategy was considered conservative. Fifty-seven patients who developed the shock late or after a revascularization procedure, or who died on admission, were excluded. The strategy was invasive in 73 patients (70%). Five of them died before angiography could be performed and 65 underwent angioplasty (success rate 72%). By univariate analysis the invasive strategy was associated with a lower mortality than conservative strategy (71% vs 91%, p = 0.03), but this association disappeared after adjustment for baseline characteristics. Older age, nonsmoking, and previous ischemic heart disease were independent predictors of mortality. In conclusion, we have failed to demonstrate that a strategy of urgent coronary revascularization within 24 hours of symptom onset for patients with AMI complicated by cardiogenic shock is independently associated with a lower in-hospital mortality. This strategy was limited by the high mortality within 1 hour of admission in patients with cardiogenic shock, the modest success rate of angioplasty in this setting, and the powerful influence of some adverse baseline characteristics on prognosis.

Use of intraaortic balloon counterpulsation in patients presenting with cardiogenic shock: observations from the GUSTO-I Study. Global Utilization of Streptokinase and TPA for Occluded Coronary Arteries

OBJECTIVES

We sought to examine the use, complications and outcomes with early intraaortic balloon counterpulsation (IABP) in patients presenting with cardiogenic shock complicating acute myocardial infarction and treated with thrombolytic therapy.

BACKGROUND

The use of IABP in patients with cardiogenic shock is widely accepted; however, there is a paucity of information on the use of this technique in patients with cardiogenic shock who are treated with thrombolytic therapy.

METHODS

Patients who presented within 6 h of chest pain onset were randomized to one of four thrombolytic regimens. Cardiogenic shock was not an exclusion criterion, and data for these patients were prospectively collected. Patients presenting with shock were classified into early IABP (insertion within one calendar day of enrollment) or no IABP (insertion on or after day 2 or never).

RESULTS

There were 68 (22%) IABP placements in 310 patients presenting with shock. Early IABP use occurred in 62 patients (20%) and none in 248 (80%). Most IABP use occurred in the United States (59 of 68 IABP placements) involving 32% of U.S. patients presenting with shock. Despite more adverse events in the early IABP group and more episodes of moderate bleeding, this cohort showed a trend toward lower 30-day and 1-year mortality rates.

CONCLUSIONS

IABP appears to be underutilized in patients presenting with cardiogenic shock, both within and outside the United States. Early IABP institution is associated with an increased risk of bleeding and adverse events but a trend toward lower 30-day and 1-year all-cause mortality.

Intraaortic balloon pump insertion after percutaneous revascularization in patients with severe peripheral vascular disease

Severe aortoiliac peripheral vascular disease (PVD) is considered a contraindication for the placement of an intraaortic balloon pump (IABP) because of a high risk of limb ischemia. Recent advances in percutaneous transluminal angioplasty (PTA) and stenting have altered the treatment of iliac stenoses such that the results of PTA with stenting compare favorably with surgery. We reviewed our experience with placement of IABP between July 1994 and February 1996. Of 64 patients receiving IABP, 17 had known or suspected peripheral vascular disease. Severe iliac or distal aortic stenoses were present in 9. These 9 patients underwent PTA with or without stenting prior to 10 IABP insertions. Limb ischemia occurred in 10% of PVD patients treated with percutaneous revascularization, compared to 11% in patients without PVD. No patient had a serious vascular complication or required vascular surgery. We conclude that percutaneous revascularization in patients with severe aortoiliac PVD, for whom this IABP insertion had previously been considered contraindicated, results in a low rate of limb ischemia.

Cardiogenic shock: thrombolysis or angioplasty?

Cardiogenic shock (CGS) occurs in 3 to 20% of patients presenting with acute myocardial infarction (MI), and it generally involves dysfunction of at least 40% of the total myocardial mass. Prior to the advent of balloon angioplasty and thrombolysis, in-hospital mortality was greater than 75%. This mortality rate has been consistent in reported series despite the advent of cardiac intensive care units, vasopressor, inotropic, and vasodilator therapy. Intra-aortic balloon counterpulsation therapy provides hemodynamic improvement, and it may provide some mortality benefit when used in conjunction with appropriate revascularization. Survival studies have shown that patency of the infarct-related artery is a strong predictor of survival. No randomized trials have been completed to examine which reperfusion therapy best treats this emergent situation. Subgroup analysis of large scale, multicenter trials, although underpowered, has shown no improvement in mortality with use of thrombolytic agents, leading many to advise use of mechanical intervention. In patients who present with acute MI with contraindications to thrombolysis, primary angioplasty is the treatment of choice. At selected centers, primary angioplasty is comparable to or better than thrombolytic therapy for patients presenting with acute MI, with or without CGS. Studies examining angioplasty in patients with CGS have shown high procedural success rates (75%) and reduced in-hospital mortality (44%), particularly in those patients with successful revascularization. Emergency bypass surgery may improve survival, but it is costly, unavailable to many, and often leads to excessive delays in therapy. If available, we believe that primary angioplasty is the treatment of choice for patients with CGS.

Update on current techniques of myocardial protection

The spectrum of strategies for myocardial protection has led to the artificial creation of adversarial positions in regard to warm versus cold blood cardioplegia, antegrade versus retrograde delivery, and intermittent versus continuous perfusion. This report reviews the background for the aforementioned methods, that has led to the evolution of an integrated myocardial management technique that combines the advantages of the aforementioned methods to compensate for their individual shortcomings. This approach coordinates the myocardial protective strategies with the continuity of the operation so that the surgical procedure is never interrupted. It provides unimpaired vision, avoids unnecessary ischemia and cardioplegic overdose, allows aortic clamping as soon as cardiopulmonary bypass is started, permits aortic unclamping and discontinuation of bypass shortly after the technical procedure is completed, and minimizes the ration of ischemia and cardiopulmonary bypass. The preliminary results in 1,474 patients from four centers with surgeons participating in the infrastructure of this method are presented.

Hemodynamic, mechanical, and metabolic determinants of thrombolytic efficacy: a theoretic framework for assessing the limitations of thrombolysis in patients with cardiogenic shock

Although thrombolytic therapy has been shown to limit infarct size, preserve left ventricular function, and improve survival in most subgroups of patients with acute MI, a benefit has not been demonstrated in patients with clinical left ventricular dysfunction or overt cardiogenic shock before treatment is initiated. The reason(s) for the lack of benefit derived from thrombolytic therapy in these settings is unclear. Left ventricular dysfunction and overt cardiogenic shock are the result of extensive myocardial necrosis, typically in excess of 30% of the left ventricle, which progresses over time. The available data suggest that thrombolytic efficacy is decreased because of either hemodynamic, mechanical, or metabolic factors. As a result coronary patency is rarely achieved in a timely fashion, and if patency is achieved it typically is not maintained. The ability of mechanical revascularization by means of balloon angioplasty to reduce mortality suggests that reperfusion is a key determinant of outcome even among patients with large infarctions and early signs of left ventricular dysfunction. Thrombolytic therapy, which is widely available and extensively tested, represents the standard of care for patients with acute MI. Its apparent lack of efficacy in patients with congestive heart failure and cardiogenic shock is poorly understood. Further investigation must therefore be undertaken.

Prognosis in cardiogenic shock after acute myocardial infarction in the interventional era

OBJECTIVES

The purpose of this study is to describe the outcome in cardiogenic shock treated with aggressive reperfusion therapy and to identify factors predictive of in-hospital and long-term mortality.

BACKGROUND

Cardiogenic shock is the most common cause of death in patients admitted to the coronary care unit. Although studies have reported lower mortality rates in shock treated with angioplasty, few studies have described a cohort of patients with shock who were not selected because they were most likely to benefit from reperfusion therapy.

METHODS

A consecutive series of 200 patients admitted with acute myocardial infarction complicated by cardiogenic shock were studied.

RESULTS

The in-hospital mortality rate was 53%. Variables with significant univariable association with in-hospital death included patency of the infarct-related artery, patient age, lowest cardiac index, highest arteriovenous oxygen difference and left main coronary artery disease. The most important independent predictors of in-hospital death were patency of the infarct-related artery, cardiac index and peak creatine kinase, MB fraction. The mortality rate in patients with patent infarct-related arteries was 33% versus 75% in those with closed arteries and 84% in those in whom arterial patency was unknown. Patients who survived to hospital discharge were followed up for a median of 2 years, with a mortality rate of 18% after 1 year. The best descriptors of the relation between these variables and postdischarge mortality included age, peak creatine kinase, ejection fraction and patency of the infarct-related artery.

CONCLUSIONS

In a large consecutive series of patients with cardiogenic shock with complete follow-up, patency of the infarct-related artery was most strongly associated with in-hospital and long-term mortality. This finding supports an aggressive interventional strategy in patients with cardiogenic shock.

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

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

Early revascularization improves survival in cardiogenic shock complicating acute myocardial infarction

The effects of coronary revascularization by percutaneous transluminal coronary angioplasty or coronary bypass grafting, or both, on survival were evaluated in 81 patients with cardiogenic shock complicating acute myocardial infarction. Thirty-two patients had successful revascularization and 49 patients had unsuccessful or no revascularization. Revascularization was achieved by coronary angioplasty in 22 patients, coronary bypass surgery in 2 and angioplasty followed by bypass surgery in 8. No significant differences were noted between the two groups with regard to baseline clinical or hemodynamic variables. Intraaortic balloon counterpulsation was employed in 27 (84%) of the 32 patients in the group with revascularization and in 19 (39%) of the 49 patients without revascularization (p = 0.0006). The in-hospital survival was significantly better in the patients with--18 (56%) of 32--than in the patients without revascularization--4 (8%) of 49 (p less than 0.0001). At a mean follow-up period of 21 +/- 15 months, this survival difference persisted--16 (50%) of 32 patients with revascularization survived versus 1 (2%) of 49 patients without revascularization (p less than 0.0001). The mean time from the onset of shock to revascularization differed significantly between survivors (12.4 +/- 15 h) and nonsurvivors (58.5 +/- 93 h) in the group with revascularization (p = 0.0004). In the revascularization group, the in-hospital survival rate was 77% (17 of 22) when revascularization was performed within 24 h but only 10% (1 of 10) when it was performed after 24 h (p = 0.0006).(ABSTRACT TRUNCATED AT 250 WORDS)

Percutaneous transluminal coronary angioplasty in patients with cardiogenic shock

In cardiogenic shock complicating acute myocardial infarction, percutaneous transluminal coronary angioplasty has been reported to significantly improve the modest survival benefits afforded by emergency surgical revascularization and thrombolytic therapy. The records of all patients who underwent angioplasty for acute myocardial infarction complicated by cardiogenic shock were retrospectively reviewed to determine whether coronary angioplasty improves survival. Of the 45 patients, 28 (group 1, 62%) had successful dilation of the infarct-related artery and 17 (group 2, 38%) had unsuccessful angioplasty. The groups were similar in extent of coronary artery disease, infarct location, incidence of multivessel disease and hemodynamic variables. The overall hospital survival rate was 56% (71% in group 1 and 29% in group 2). Group 1 patients had more left main coronary artery disease, and group 2 patients were older and had a higher incidence of prior myocardial infarction. Multivariate analysis showed that the survival advantage in patients with successful angioplasty was statistically significant (p = 0.014) when these factors were taken into account. At a mean follow-up interval of 2.3 years (range 1 month to 5.6 years), there were five deaths (four cardiac and one noncardiac), for a 2.3-year survival rate of 80% in patients surviving to hospital discharge. During the follow-up period, 36% of hospital survivors had repeat hospitalization for cardiac evaluation, 8% had myocardial infarction, 8% had coronary artery bypass surgery and 24% had angina.

Limitations of thrombolytic therapy for acute myocardial infarction complicated by congestive heart failure and cardiogenic shock

As many as one quarter of patients treated with thrombolytic therapy present with congestive heart failure or cardiogenic shock. Although thrombolytic therapy has been shown to limit infarct size, preserve left ventricular ejection fraction and decrease mortality in most subgroups of patients, no apparent benefit has been demonstrated in patients with clinical left ventricular dysfunction. The lack of correlation between ejection fraction and other measurements of left ventricular dysfunction such as exercise time, cardiac output, filling pressures, activation of the neurohumoral system and regional perfusion bed abnormalities may partly explain this paradox. Alternatively, lower perfusion rates, higher reocclusion rates, associated mechanical complications or completed infarction may explain these findings. Preliminary data indicate that emergency coronary angioplasty or bypass graft surgery improves survival in selected patients with cardiogenic shock. Because these findings suggest that restoration of infarct artery patency is especially important in patients with clinical left ventricular dysfunction, additional studies are needed in these patients to investigate the potential benefit that new thrombolytic strategies, inotropic or vasodilator agents or intraaortic balloon counterpulsation might offer by augmenting coronary blood flow and improving reperfusion rates. Currently, acute mechanical revascularization should be considered for patients who present with congestive heart failure associated with hypotension or tachycardia and for patients with cardiogenic shock.

Percutaneous intraaortic balloon pumping: four years from Tiblisi

Intraaortic balloon pumping (IABP) has now evolved as the mechanical supportive treatment of choice for the management of refractory left ventricular power failure. A new single-chambered percutaneous intraaortic balloon (Datascope Corp., Paramus, NJ, U.S.A.) has been constructed around a central guidewire. The balloon can be wrapped around the guidewire, enabling its insertion into the femoral artery through a 12-F sheath, inserted by a modified Seldinger technique. A dual-lumen automatic wrapping version has recently been employed. Percutaneous IABP insertion has been performed in 149 patients (mean age 58 years). In our medical group of 75 patients, 59 underwent urgent open heart surgery and 53 (90%) survived. In patients who could not be separated from cardiopulmonary bypass, 23 of 61 (38%) survived. Vascular complications occurred in 10% of the patients. Percutaneous balloon insertion permits the rapid institution of IABP support and broadens the medical and surgical applications of IABP.

Early myocardial revascularization for postinfarction angina

In 1983 and 1984, coronary artery bypass grafting (CABG) was performed on 107 consecutive patients for postinfarction angina. In each instance, CABG was done within 30 days of infarction. Sixty-three patients (59%) required intravenous administration of nitroglycerin and/or the intraaortic balloon pump (IABP) for relief of angina. Oral medications relieved angina in the remaining 44 patients. Thirty-eight patients underwent CABG 7 days or less after the infarction (Group 1), 25 received it between 8 and 15 days later (Group 2), and 44 had CABG between 16 and 30 days later (Group 3). There were 9 in-hospital deaths: 4 in Group 1, 2 in Group 2, and 3 in Group 3. Thirteen patients needed the IABP for hemodynamic stability as well as relief of angina. Even when the patient was stable hemodynamically, death was more likely to occur among these 13 patients if CABG was conducted within 7 days of infarction. Follow-up was 94% complete at 29.4 months. Eighty-six percent of patients were asymptomatic or in New York Heart Association Functional Class I, and 6% were in Class II. There were 2 late deaths. CABG for angina can be accomplished within 30 days of an acute infarction with good results. The exception to this rule is the patient in whom shock develops after a myocardial infarction and who, despite stabilization, receives CABG within 7 days of the infarction.

Intraaortic balloon pump insertion: a randomized study comparing percutaneous and surgical techniques

To compare the percutaneous and surgical techniques of intraaortic balloon pump insertion, 101 patients referred for this procedure were randomly assigned to either percutaneous or surgical insertion. Insertion using the designated technique was successful in 45 (88%) of 51 patients with percutaneous insertion and 48 (96%) of 50 patients with surgical insertion (difference not statistically significant). The time from the beginning of the insertion procedure to the initiation of counterpulsation was 13 +/- 8 minutes for the percutaneous technique versus 31 +/- 16 minutes for the surgical technique (p less than 0.001). In the percutaneous group, 10 patients required Fogarty thrombectomy after balloon pump removal, and 1 patient developed severe leg ischemia requiring immediate termination of balloon pump support. In the surgical group, one patient developed leg ischemia requiring surgical intervention, three patients developed sepsis with bacteremia (including one patient who required vein patch repair of the femoral artery), one patient developed a wound infection requiring debridement and one patient had a cerebral embolus. Aortic dissection, aortoiliac perforation or amputation did not occur in either group. Major vascular complications occurred in 11 patients (22%) with percutaneous insertion versus 2 patients (4%) with surgical insertion (p less than 0.05). It is concluded that although the percutaneous technique for intraaortic balloon pump insertion is faster than the surgical technique and is technically easy, it is associated with a higher incidence of vascular complications.

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.

Shock in acute myocardial infarction: evolution of physiologic therapy

In the past 25 years the treatment of shock in myocardial infarction has evolved into a physiologic approach based on on-line measurements of hemodynamic variables. This has aided in the development of new pressor agents so that a family of pharmacologic agents is now available. Appropriate use of vasodilators and recognition and treatment of intravascular volume depletion have increased survival. Recognition and appropriate treatment of the preshock state have decreased the incidence of shock. The criteria for use of mechanical support and surgical intervention are soundly established; the use of thrombolytic therapy and balloon angioplasty for this syndrome is ready to be evaluated.

Evidence that hospital care for acute myocardial infarction has not contributed to the decline in coronary mortality between 1973-1974 and 1978-1979

To investigate whether the reported 17% decline in the national rates of acute ischemic heart disease mortality between 1973 and 1978 was attributable to decreased in-hospital mortality for patients with acute myocardial infarction (MI), we surveyed all 63 acute care hospitals in the Boston, Massachusetts, area. Compared with 1973-1974, more 1978-1979 MI patients were admitted to hospitals in metropolitan Boston, and especially to the five university teaching hospitals. Between 1973-1974 and 1978-1979, hospital admission rates decreased for younger patients and increased for older patients, but overall admission rates were almost identical. In-hospital mortality rates from acute MI did not change significantly in any age group. Because overall MI mortality was declining while in-hospital MI mortality was unchanged, the proportion of acute MI deaths that occurred inside the hospital increased from about 30% to about 40%. Although current hospital care undoubtedly benefits many individual patients, this study suggests that improvements in the in-hospital care of acute MI patients are a major explanation for nationwide mortality trends between 1973 and 1978.

Intraaortic balloon counterpulsation with and without reperfusion for myocardial infarction shock

Forty patients were treated for cardiogenic shock secondary to acute myocardial infarction. Twenty-one (group 1) were treated with intraaortic balloon counterpulsation and 19 (group 2) were treated with counterpulsation and coronary artery bypass grafting. The groups were similar in age, incidence of previous infarction, initial hemodynamics and coronary anatomy. The in-hospital mortality between group 1 (52.4%) and group 2 (42.1%) was not significantly different. The difference in long-term mortality between group 1 and group 2 was substantially different (71.4% vs 47.3%). The subset of group 2 (n = 12) that underwent reperfusion and counterpulsation within 16 hours from the onset of symptoms of infarction had a lower mortality (25.0%) than the subset (n = 7) that underwent operation more than 18 hours after the onset of symptoms (71.4%). The long-term mortality in the subset of group 2 patients operated on within 16 hours after the onset of infarction was significantly different from that in group 1 (25.0% vs 71.4%, p less than 0.03). The data suggest that reperfusion with counterpulsation is more effective when carried out early. Patients who develop shock more than 18 hours after the onset of symptoms of infarction appear to benefit most if treated with counterpulsation alone.

Aortocoronary bypass grafting in the management of patients with coronary artery disease

There is widespread agreement that aortocoronary bypass grafting generally lessens the symptoms and functional limitations of patients with angina pectoris. Evidence for prolongation of life or prevention of myocardial infarction, arrhythmias and ventricular dysfunction is inconclusive. Harmful effects associated with surgical management of coronary artery disease can be documented in terms of operative mortality, perioperative myocardial infarction, graft occlusion and progression of occlusive disease in the native circulation. In this review of published experience, the accomplishments and the limitations of myocardial revascularization are considered in various clinical settings. Critical assessment of evolving information leads to the conclusion that widespread application of this procedure beyond the alleviation of symptoms refractory to medical therapy is not justified by present data.

Comparative effect of counterpulsation and bypass on left ventricular myocardial oxygen consumption and dynamics before and after coronary occlusion

In this preparation counterpulsation effect was found equivalent to 42 +/- 7% of complete left ventricular bypass before, and 46 +/- 9% post-coronary occlusion. We conclude that counterpulsation is effective mainly by reducing a major determinant of myocardial oxygen consumption, i.e., afterload, whereas left ventricular bypass by reducing primarily preload results in secondary afterload reduction when peripheral resistance is unchanged. At the higher left ventricular bypass levels, reduction of myocardial oxygen consumption is far greater than during balloon counterpulsation. Acute functional loss of myocardium does not alter the effect of these assist methods regarding the reduction of myocardial oxygen consumption. Whether selection of either method for clinical application should be made only on the basis of its capability for reduction of myocardial oxygen consumption remains to be justified by conclusive demonstration of beneficial effect of reduction of myocardial oxygen consumption in the specific circulatory disorders.

Afterload reduction and cardiac performance. Physiologic basis of systemic vasodilators as a new approach in treatment of congestive heart failure

Digitalis and diuretics constitute conventional therapy of congestive heart failure, but systemic vasodilators offer an innovative approach in acute and chronic heart failure of decreasing increased left ventricular systolic wall tension (ventricular afterload) by reducing aortic impedance and/or by reducing cardiac venous return. Thus, vasodilators increase cardiac output (CO) by diminishing peripheral vascular resistance (PVR) and/or decrease increased left ventricular end-diastolic pressure (LVEDP) (ventricular preload) by diminishing venous tone. Concomitantly, there is reduction of myocardial oxygen demand, thereby reliably reducing angina pectoris in coronary disease, and potentially limiting infarct size and ischemia provided systemic arterial pressure remains normal. The vasodilators produce disparate modifications of cardiac function depending upon their differing alterations of preload versus impedance: nitrates principally cause venodilation (decrease LVEDP); nitroprusside, phentolamine and prazosin produce balanced arterial and venous dilation (decrease LVEDP and increase CO) provided left ventricular filling pressure is maintained at the upper limit of normal; whereas hydralazine predominantly effects arteriolar dilation (increases CO). With depressed CO plus highly increased LVEDP and increased PVR, nitrates also induce some increase of CO by reducing PVR. Combined nitroprusside and dopamine synergistically enhance CO and decrease LVEDP. Mechanical counterpulsation aids nitroprusside in acute myocardial infarction. The 30-minute venodilator action of sublingual nitroglycerin is extended for 4 to 6 hours by cutaneous nitroglycerin ointment, by sublingual and oral isosorbide dintrate, and by oral pentaerythritol tetranitrate and sustained-release nitroglycerin capsules. Ambulatory oral vasodilator therapy is provided by long-acting nitrates (relieve pulmonary congestion); hydralazine (improves fatigue); prazosin alone, combined nitrate-hydralazine combined prazosin-hydralazine (improve both dyspnea and fatigue).