Asian Cardiovasc Thorac Ann 1999;7:276-281
© 1999 Asia Publishing EXchange Pte Ltd
Role of Intraaortic Balloon Pump in Left Ventricular Endoaneurysmorrhaphy
Hossam Eldin Eid, MD
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Department of Cardiothoracic Surgery, Texas Heart Institute, Houston, Texas, USA, Ain Shams University Hospitals, Cairo, Egypt, Dubai Hospital, Dubai, UAE
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For reprint information contact: Hossam Eldin Eid, MD Tel: 971 4271 4444 Fax: 971 4271 9340 Department of Cardiothoracic Surgery, Dubai Hospital, P.O. Box 7272, Dubai, UAE.
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Abstract
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Intraaortic balloon counterpulsation has become a prerequisite for surgical repair of a left ventricular aneurysm. From October 1991 to October 1996, 60 consecutive patients underwent left ventricular endoaneurysmorrhaphy. Most had associated procedures, mainly coronary artery bypass grafting. Twenty-two patients (36.7%) were in New York Heart Association functional class III or IV preoperatively. These included 16 (26.7%) who had low cardiac output requiring an intraaortic balloon pump in the perioperative period. Pharmacological inotropic support alone was inadequate in 13 of these patients, one required a balloon pump for 5 days preoperatively due to severe low cardiac output, and 2 needed mechanical support postoperatively for ventricular arrhythmia and low cardiac output. The other 44 patients (73.3%) recovered without mechanical support. This study highlights the important role of intraaortic balloon counterpulsation in the surgical treatment of postinfarction left ventricular aneurysm.
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Introduction
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The decrease in left ventricular (LV) function associated with myocardial infarction (MI) is related to the volume of muscle damage. Because of the absence of oxygen reserve, contractility decreases significantly within 4 to 6 seconds of cessation of blood flow.1 In patients with congestive heart failure and LV aneurysm, surgical treatment has been shown to improve the quality of life and the prognosis for cardiac-related complications, although survival in early studies was not found to be increased compared with medical management.2 Hemo-dynamic benefits result from a reduction in both LV volume (thereby reducing wall stress in the residual myocardium) and functional mitral regurgitation. Studies evaluating hemodynamic improvement after LV aneurysmectomy have shown variable results, mainly because of differences in study population.3 The technique of endoaneurysmorrhaphy aims to achieve restoration of normal volume and contour to the dilated and elongated LV cavity. This can be accomplished with a patch of woven Dacron fabric.4 The current results of LV recon-struction with or without myocardial revascularization are better than in the past. Although advances in myocardial protection have contributed significantly, superior reconstructive techniques account for most of the improvement in outcome.5
The concept of intraaortic balloon counterpulsation to augment coronary and systemic blood flow was developed by Moulopoulos and colleagues6 in 1962. Intraaortic balloon counterpulsation is usually employed postoperatively in patients with severe LV dysfunction, with or without evidence of myocardial necrosis, and with signs of inadequate cardiac output or severe ventricular arrhythmia. This technique has clearly led to the salvage of some patients who otherwise would not have survived the cardiac operation.7 This study is reported to highlight the role of the intraaortic balloon pump (IABP) in the surgical treatment of LV aneurysm by endo-aneurysmorrhaphy, especially in patients with com-promised LV function.
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Patients and Methods
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From October 1991 to October 1996, 60 consecutive patients who were referred for surgical treatment of postinfarction LV aneurysm were included in this study. There were 55 men (92%) and 5 women (8%), ranging in age from 41 to 70 years old, with a mean age of 60.5 ± 1.1 years. Most patients underwent endoaneurysmor-rhaphy with concomitant myocardial revascularization. All patients were studied with regard to age, sex, preoperative clinical status, New York Heart Association functional class, time after MI, associated cardiac procedures, duration of cardiopulmonary bypass (CPB), aortic crossclamp time, occurrence of perioperative MI (monitored by electrocardiogram and cardiac enzymes), and the preoperative and postoperative LV ejection fractions. Sixteen patients who required hemodynamic support with an IABP were compared with 44 who did not need mechanical support. The patient profile is outlined in Table 1
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All operations were carried out under endotracheal general anesthesia with CPB, aortic crossclamping, and crystalloid potassium cardioplegia. The technique of endoaneurys-morrhaphy was as described by Cooley4 in which a fabric patch is used to compartmentalize the left ventricle, creating an extra-cavity space that is incorporated into the ventricular wall. The site of insertion of the intraaortic balloon catheter, duration of support, indications for weaning from the IABP, and incidence of complications were recorded. A Datascope model 90 intraaortic balloon pump and a 9.5F Datascope true sheathless catheter (Datascope Corp, Fairfield, NJ, USA) were used when required. The indications for use of an IABP were: mean blood pressure of 60 mm Hg and falling; cardiac index of 1.8 L•min–1•m–2; left atrial pressure of 25 mm Hg; need for high-dose inotropic support; recurrent ventricular arrhythmias; and evidence of significant intraoperative MI. The criteria for weaning from the IABP were: mean blood pressure of 65 mm Hg or above; cardiac index of 2.5 L•min–1•m–2; left atrial pressure of 15 mm Hg or less; minimum inotropic support (dopamine in diuretic dose); satisfactory arterial blood gases; adequate urine output; and improvement of LV ejection fraction on transthoracic echocardiography.
Quantitative data were analyzed using the paired Student t test and qualitative data were analyzed using the standard error of the difference between percentages (U test). A p value of less than 0.05 was considered significant. Data were expressed as mean ± standard error of the mean.
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Results
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The associated surgical procedures are listed in Table 2. The relationship between use of IABP support, perioperative MI, and revascularization of the left anterior descending coronary artery (LAD) is shown in Table 3. The LAD was revascularized in 45 (82%) of the 55 patients who had left ventricular endoaneurysmorrhaphy and concomitant coronary artery bypass grafting. Fifty-seven patients (95%) had an anteroapical LV aneurysm that involved the LAD region. The LAD was blocked by atheroma in 3 patients in whom endarterectomy was required in addition to saphenous vein patch angioplasty. The left internal mammary artery (LIMA) was used to revascularize the diagonal branch of the LAD in 5 patients and the first obtuse marginal in 2 patients. The LAD could not be grafted in 8 patients who had huge anteroapical LV aneurysms due to severe atheromatous changes. There was evidence of significant intraoperative MI in 5/60 patients (8.3%). From Table 3, it is apparent that there was an increased incidence of perioperative MI and need for a balloon pump in patients who had LIMA-to-LAD grafts compared to those who had saphenous vein grafts.
The relationship between type of LV aneurysm, use of an IABP, and mortality is shown in Table 4. Twenty-two patients (36.7%) were in New York Heart Association functional class III and IV preoperatively, of whom 16 (26.7%) developed low cardiac output in the operating theater on weaning from CPB, which required an IABP in 13 cases (21.7%). A comparison of patients who had an IABP with those who did not can be seen in Table 5. Six of the 16 patients who required an IABP died as a result of low cardiac output syndrome and its com-plications. The mean preoperative ejection fraction of these patients was 25.7% ± 2.1% (Table 6). The mean postoperative ejection fraction of the patients who survived after IABP support was 38.1% ± 3.6% compared with 28.1% ± 5.5% in those who died (p = 0.14). The mean duration of intraaortic balloon counterpulsation was 89.5 ± 21.8 hours, ranging from 2 to 288 hours. The 10 patients who survived after IABP insertion required mechanical hemodynamic support for a mean of 72.4 hours, whereas the 6 who died had a mean duration of balloon counterpulsation of 118 hours (p < 0.05). The sites of insertion and complications associated with IABP use are summarized in Table 7.
Twelve patients (20%) had a recent MI (within one month of operation). Four of these patients had suffered MI within 2 weeks of the procedure and showed marked hypokinesia of all myocardial segments in addition to akinesia of the infarcted area. The other 8 patients who had MI more than 3 weeks before the operation showed regional wall abnormality in the form of akinesia of the infarcted segments. Five of the patients with recent MI required an IABP and the other 7 tolerated the procedure without pump support.
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Discussion
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Left ventricular aneurysm is one of the complications of ischemia heart disease and MI. Congestive heart failure, recurrent ventricular arrhythmia, angina pectoris, and thromboembolism are consequences of LV aneurysm. The concept of protecting LV configuration and geometry in repairing an aneurysm has led to considerable functional improvement postoperatively.8 Endoaneurysmorrhaphy employing a woven Dacron patch was used for aneurysm repair in this series. Low cardiac output syndrome was one of the most serious complications in patients with poor LV ejection fractions (25% or less) undergoing coronary artery bypass grafting procedures and LV aneurysm repair.
Over the last 2 decades, counterpulsation has became a valuable and lifesaving method of preserving myocardial function.1 Intraaortic balloon counterpulsation is used for temporary mechanical assistance of the failing heart. It reduces the energy requirement of the left ventricle and maximizes coronary perfusion by diastolic augmentation.9 The most important indications for insertion of an IABP include intractable cardiac failure after CPB, preoperative stabilization of refractory angina, and severe LV dysfunction. Thus, at any time in the perioperative period, the use of intraaortic balloon counterpulsation may be required on the basis of these criteria. In this series, dopamine was used as a mild inotropic agent that could be augmented with dobutamine and if necessary, epinephrine in dose of up to 500 ng•kg–1•min–1 in addition to amrinone for combined inotropic support with vasodilation. In 16 patients who were difficult to wean from CPB due to low cardiac output, pharmacologic support achieved no immediate response in 13 patients, so an IABP was inserted.
In spite of advances in methods of myocardial protection and inotropic therapy, between 3% and 5% of patients undergoing routine coronary artery bypass grafting require an IABP after CPB.10 For patients with LV aneurysm as a complication of MI, the incidence of IABP use is higher. In this series, 26.7% of patients required an IABP, which is comparable to 26.9% in the study by Magovern and colleagues11 in 1989, and 26.3% reported by Amano and colleagues12 in 1984. These results compare favorably with 33% and 39.5% reported by the groups of Dor13 and Stephenson14 respectively, in 1989.
Long periods of aortic-cross clamping, prolonged ischemia, less than optimal surgical revascularization, and preexisting myocardial dysfunction can have detrimental effects during weaning from CPB. During this period, the depressed myocardium is unresponsive to increasing doses of inotropic agents and vasodilator therapy. In such circumstances, the use of an IABP can provide transient physiologic support that allows recovery of optimum cardiac function.15 The mean aortic cross-clamp time in patients who required an IABP in this study was 51.8 minutes compared to 46.8 minutes in the other patients, which was not statistically significant. However, CPB time was a significant risk factor in addition to perioperative MI and advanced age.
The mortality rate of 37.5% among patients who required an IABP in this series is within the reported range of 20% to 50%.11, 16–18 Three of the 6 patients who died had suffered a perioperative MI, all were aged 70 years, 2 had a recent MI before the operation, and the other had previous LV aneurysm repair and coronary artery bypass grafting. The 10 patients who survived after IABP insertion required mechanical hemodynamic support for a significantly shorter time than the 6 who died. Thus, the duration of perioperative low cardiac output was predictive of mortality in these patients.
One patient had an IABP for 5 days preoperatively. He was aged 64 years, in New York Heart Association functional class IV, with atrial fibrillation, a preoperative LV ejection fraction of 12%, an apical LV thrombus, and pulmonary hypertension (40 mm Hg). This patient did not tolerate the procedure and died 4 hours after the operation. One of the 2 patients who had an IABP inserted in the postoperative period had suffered ventricular arrhythmia and cardiac arrest on the 4th postoperative day. He required an IABP for 8 days but died 2 months later due to multiorgan failure. The other patient had an IABP on the first postoperative day for 24 hours only. He made a good recovery and was discharged from the hospital. Some recent large series have reported hospital mortality between 3% and 7% (Table 8), whereas the mortality rate in this study was 10%.19–21 The higher incidence in this series was attributed to increased use of LIMA to revascularize the LAD and to the fact that most of the patients had anteroapical LV aneurysms with poor vascularity of the septum and anterior wall. There was also a higher incidence of associated procedures compared to the previous studies.
It was concluded from this study that intraaortic balloon counterpulsation frequently has an important role in stabilizing hemodynamics in patients undergoing LV endoaneurysmorrhaphy. Advanced age, considerable preoperative congestive heart failure, perioperative MI, prolonged CPB time, and refractory ventricular arrhyth-mias are risk factors for postoperative low cardiac output syndrome that increases mortality and morbidity. An IABP should be used without delay in such circumstances.
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References
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Abstract
Introduction
